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Ovid: Oxford Handbook of Psychiatry

Editors: Semple, David; Smyth, Roger; Burns, Jonathan; Darjee, Rajan; McIntosh, Andrew Title: Oxford Handbook of Psychiatry, 1st Edition Copyright ©2005 Oxford University Press > Table of Contents > Chapter 16 – Learning disability Chapter 16 Learning disability P.682
Introduction More than any other specialty in psychiatry, learning disability (LD) presents a multi-faceted, complex discipline, encompassing everything from molecular genetic diagnostic techniques to provision of adequate social supports. Confronted by multiple physical, psychiatric, social, occupational, communication, and educational problems (to name but a few), it is all too easy to feel overwhelmed. However, LD can be one of the most rewarding specialties: dealing with children, adolescents, adults, the elderly, families, and carers; utilising a multidisciplinary approach through collaboration with other health care professionals, psychologists, teachers, and community services; significantly impacting upon the quality of life of both patients and their family/carers. There are great variations in the range and quality of services or the LD population in different geographical areas (meaning that ‘local knowledge’ is essential). With the closure of large institutions, there are fewer specialist inpatient services. This means that work will be concentrated in the community, with differing degrees of support, and often in liaison with adult services when admission to hospital is required (see p. 696). When involved with specialist inpatient units, the clinician’s role may be more managerial than ‘hands on’, except when admission is for assessment of behavioural or psychiatric problems. The role of the LD psychiatrist includes:

  • Establishing the reason for developmental delay in infants and young children (see p. 694).
  • Establishing the nature and extent of specific learning difficulties and the statement of special educational needs for children of school age.
  • Assessing longer-term social care needs particularly in advance oftransitional stages (e.g. adolescence, later life—see p. 720.)
  • Assessing behavioural problems (see p. 718) or possible psychiatric problems (see p. 714) in children or adults.
  • Ensuring physical problems, sensory impairments, or other disabilities are not overlooked and facilitating access to general medical services and other specialist assessments.

A structured approach is essential because of the complexity of needs in many people with LD (see p. 690). The ultimate aim of the process of assessment is to determine need and to inform what types of intervention and/or treatment may be effective (and to the benefit) of the person concerned (i.e. social, educational, psychological, medical, or psychiatric). The process ought to be open and transparent, with clear communication between the clinical team, the person with the problem (when possible), and family/carers. All too often problems arise when expectations are unrealistic, or where there are misunderstandings about the actual role of particular members of the clinical team. The clinician may act as a focal point in the collation and dissemination of information, being a ‘fixed point’ for the family/carers who may be somewhat ‘at sea’ with the dizzying array of professionals involved in the care of the child or adult with LD. P.683
Historical perspective The Mental Deficiency Act (1913) and The Elementary Education (Defective and Epileptic Children) Act (1914) were turning points in the management of those diagnosed as ‘mentally defective’ or ‘feebleminded’ (by ‘duly qualified’ medical practitioners) in the UK, requiring local authorities to provide suitable care in special institutions or the guardianship of families, and educational placements in special schools or classes. These ‘segregation’ acts moved those with LD from home, asylum, or workhouse, to special institutions, with the aim of providing for their special needs and the hope of social treatments (through education and training). This addressed the social concerns of the day, by scapegoating the ‘feebleminded’ as the cause of everything from social problems (e.g. poverty, alcoholism, unemployment, promiscuity, illegitimacy) to racial, and even imperial, decline. Defining ‘idiots’, ‘imbeciles’, and the ‘feebleminded’ by their ability to look after themselves (rather than by intelligence) led to ‘moral insanity’ (e.g. having an illegitimate child, habitual drunkenness) being used as grounds for committal to an institution. Progress was being made in classifying ‘defectives’, but most medical authorities believed causation was inherited (a ‘neuropathic trait’). This fed directly into prevalent eugenic notions of preventing ‘racial decline’ by segregation, with physical stigmata (e.g. facial characteristics) seen as ‘proof’ that appearance (esp. ‘racial characteristics’) and mental health were inter-related. Nowadays, such ideas seem simplistic (like the practice of phrenology at the time), but the notion that the Caucasian races were ‘more civilised’ had significant influence at the turn of the 20th century. Some doctors even advocated compulsory sterilisation ‘to protect social health, but permit liberty’. It would take decades, and two world wars, before social, political, and scientific pressure finally dismantled these firmly held ideas. Impetus came from concerns about large institutions, forms of treatment, and rights of the mentally handicapped. In the 1960s, official enquiries found evidence of abuse, malpractice, and neglect. Alarm among social reformers about the conditions in institutions was fuelled by Erving Goffman’s Asylums. Efforts were made to reduce stigma by replacing older labels with less pejorative terms, (e.g. ‘mental subnormality’, ‘mental retardation’, ‘mental handicap’ for ‘mental deficiency’, ‘idiot’, ‘imbecile’; ‘trisomy 21’ or ‘Down’s syndrome’ for ‘mongolism’; ‘congenital hypothyroidism’ for ‘cretinism’). In 1968, ICD-8 (WHO) classified ‘mental retardation’ according to severity of intellectual impairment (by IQ assessment) and social factors. The 1970s/80s saw major policy changes, emphasising integration with mainstream resources and education, away from institutions and to the community. Many people with LD moved from hospitals to purpose-built hostels or ‘group homes’. Understanding of the aetiology of LD expanded from the 1950s onwards, with Lionel Penrose’s Biology of Mental Defect in 1949, and the discovery of the genetic basis of Down’s syndrome by Jérôme Lejeune in 1959. By the 1970s most standard textbooks recognised multiple aetiologies (genetic and environmental), separating pre-, peri-, and post-natal causes. Karyotyping, identifying metabolic abnormalities, and isolating infectious agents, allowed for laboratory diagnoses, rather than reliance on clinical observation. P.685
Pharmacological treatments of epilepsy, behavioural disturbance, movement disorders, and psychiatric comorbidity; dietary treatments of metabolic disturbances; behavioural and cognitive approaches; improved assessment/ management of social/occupational functioning, communication problems, and educational needs have allowed rational management of LD. Problems still exist (e.g. inadequacy of funding for community care/resources, unequal distribution of specialist services), but the outlook for people with LD in this, the 21st century, is more promising than it was at the turn of the last. P.686
Classification In the UK, the preferred term ‘learning disability’ (deemed to be the least pejorative) is used interchangeably with the internationally agreed term ‘mental retardation’ (used in both ICD-10 and DSM-IV). ICD-10 defines ‘mental retardation’ as ‘a condition of arrested or incomplete development of the mind, characterised by impairments in cognition, language, motor and social abilities’. Both ICD-10 and DSM-IV also agree on the use of the terms mild, moderate, severe, and profound to describe the degree of mental retardation, with arbitrary ‘cut-offs’ varying only slightly:

IQ range for categories ICD-10 DSM-IV
Mild 50–69 50–55 to 70
Moderate 35–49 35–40 to 50–55
Severe 20–34 20–25 to 35–40
Profound Below 20 Below 20–25

ICD-10 guidelines Mild Delay in acquiring speech, but eventual ability to use everyday speech; generally able to independently self-care; main problems in academic settings (i.e. reading, writing); potentially capable of working; variable degree of emotional and social immaturity; problems more like the normal population. Minority with clear organic aetiology, variable associated problems (autism, developmental disorders, epilepsy, conduct disorders, neurological and physical disabilities). Moderate Delay in acquiring speech, with ultimate deficits in use of language and comprehension; few acquire numeracy and literacy; occasionally capable of simple supervised work. Majority have an identifiable organic aetiology, a substantial minority have associated problems (autism, developmental disorders, epilepsy, conduct disorders, neurological and physical disabilities). Severe Similar to moderate, but with lower levels of achievement of visuospatial, language, or social skills. Marked motor impairment and associated deficits. Profound Comprehension and use of language very limited; basic skills limited at best; organic aetiology clear in most cases; severe neurological and physical disabilities affecting mobility common; associated problems (atypical autism, pervasive developmental disorders, epilepsy, visual and hearing impairment) more common. DSM-IV additional features:

  • Onset before age 18.
  • Deficits/impairments in present adaptive functioning in at least 2 areas from:
    • Communication
    • Self-care
    • Home living
    • P.687

    • Social/interpersonal skills
    • Use of community resources
    • Self-direction
    • Functional academic skills
    • Work
    • Leisure
    • Health
    • Safety

‘Subcultural’ LD Although the concept of ‘psychosocial’ causation (due to physical and emotional neglect) is controversial, it is true to say that mild or borderline intellectual impairment is more common in families of lower socio-economic status. This is best viewed as a cultural norm, and individuals generally have no, or only minor, impairments in adaptive functioning (i.e. lack of disability or handicap—see p. 688). Generally the intellectual ability of family members is also in the borderline range, dysmorphic characteristics are less likely, and other impairments or disabilities are unusual. This is in contrast to biological causation where impairments are more significant, there is no difference in socio-economic status, parents and sibling are usually of normal intelligence, and dysmorphic features are more common. P.688
Impairments, disabilities, and handicaps It is often confusing when terminology is used interchangeably. This is especially true for learning disability or mental retardation when they are inaccurately used as diagnostic terms. In fact, they both describe a constellation of impairments with associated disability and handicap, the aetiology of which may be known (e.g. Down’s syndrome) or unknown (e.g. childhood disintegrative disorder). The WHO1 has proposed a system of classification which helps define needs and direct interventions/treatments, without making specific aetiological assumptions: Impairment

  • Any loss or abnormality of psychological, physiological, or anatomical structure or function.
    • A deviation from some norm in an individual’s biomedical status.
    • Characterised by losses or abnormalities that may be temporary or permanent.
    • Includes the existence or occurrence of an anomaly, defect, or loss in a limb, organ, tissue, or other structure of the body, or a defect in a functional system or mechanism of the body, including the systems of mental functioning.
    • Is not contingent upon aetiology.


  • Any restriction or lack (resulting from impairment) of ability to perform an activity in the manner or within the range considered normal for a human being.
    • Concerned with compound or integrated activities expected of the person or of the body as a whole (e.g. tasks, skills, and behaviours).
    • Includes excesses or deficiencies of customarily expected activities and behaviour, which may be temporary or permanent, reversible or irreversible, and progressive or regressive.
    • The process through which a functional limitation expresses itself as a reality in everyday life.


  • A disadvantage for a given individual, resulting from impairment or disability that limits or prevents the fulfilment of a role that is normal for that individual.
    • Places value on this departure from a structural, functional, or performance norm by the individual or his/her peers in their cultural context.
    • Is relative to other people and represents discordance between the individual’s performance or status and the expectations of their social/cultural group.
    • P.689

    • A social phenomenon, representing the social and environmental consequences for the individual stemming from his/her impairment or disability.

References 1 World Health Organisation (1980) International classification of impairments, disabilities, and handicaps (10th revision). World Health Organisation, Geneva. P.690
The process of assessment—a structured approach When a person with LD presents to services because of a particular problem (e.g. ‘challenging behaviour’, see pp. 716, 717), the task for the clinician is to determine the underlying cause, which will include predisposing, precipitating, and perpetuating factors. Causation may in fact be multifactorial, and because of this a structured approach is best. Some aspects of assessment may be well documented (e.g. the aetiology of the LD), particularly when the patient is an adult. Any ‘diagnostic formulation’ should always take note of previous assessments and highlight what further assessments may be helpful.

  • Intellectual impairment Assessed using standardised tests (e.g. Wechsler scales).
  • Severity of LD ICD-10 or DSM-IV criteria (see p. 686).
  • Disabilities Assessments of functioning (e.g. Vineland Adaptive Behaviour Scales, American Adaptive behaviour Scales, Hampshire Assessment for Living with Others (HALO)).
  • Handicap Assessment of quality of life and life experiences (e.g. Life Experiences Checklist).
  • Aetiology of LD See Assessing causation p. 694.

Other aspects of assessment will include:

  • Full physical examination As this may identify undiagnosed problems, which the patient may be unable to communicate.
  • Mental state examination See Psychiatric comorbidity in the LD population p. 714, which may go unrecognised and untreated. This includes temperament, usual behaviour patterns, current medication.
  • Communication difficulties Which may include formal speech and language assessment.
  • Environmental and social factors Which may be contributing to the problem.

Current support network Assessment will involve not only talking to the patient, but also gathering information from previous documentation (including current treatments / previous diagnoses), family/carers, other support services, and teachers. The aim is to view the current problem in the light of past experiences, known problems, and current situational factors. A longitudinal approach is advised (i.e. does the current presentation reflect a recurrent problem, is it part of progressive functional decline, or does it represent a new, unidentified problem/unmet need?). It is useful to document the current supports received by the patient, and any important contacts for future reference. Needs’ assessment Should it be the case that the persons’ needs have changed, then there may, be a statutory responsibility to undertake a formal ‘needs’ assessment’, taking into account the wishes of the person (if they have capacity to make the kinds of decisions required) and others involved in care provision. This includes social care, educational, and health care needs. P.691
Aetiology A specific cause for LD can be identified in about 80% of severe and 50% of mild cases. About 50–70% of cases will be due to a prenatal factor, 10–20% perinatal, and 5–10% postnatal. The identification of aetiological factors is important because it allows for discussion of the risk of recurrence in future pregnancies. A known cause can allow for discussion of likely disabilities, possible cognitive impairments, and prognosis. This can be useful for planning supports/services, access to education, and optimising environmental factors (see Needs and priorities, p. 690). Modern classifications of aetiological factors are based on timing of the event: Genetic causes

  • Autosomal chromosome disorders (e.g. Down’s syndrome, pp. 700, 701)
  • Sex chromosome disorders (see p. 702)
  • Deletions and duplications (see pp. 704, 705)
  • Autosomal dominant (p. 706) and recessive (pp. 706, 707) conditions
  • X-linked recessive (p. 708) and dominant (p. 709) conditions
  • Presumed polygenic conditions (e.g. neural tube defects, pervasive developmental disorders)
  • Mitochondrial disorders, maternally inherited (e.g. MERRF myoclonic epilepsy with ragged red fibres).

CNS malformations of unknown aetiology About 60% of all CNS malformations do not have a known genetic or exogenous cause. The types of malformation seen indicate the timing of the causative event, but not its nature (see opposite). External prenatal factors (see Non-genetic causes of LD, p. 710) Particularly in the early stages (during blastogenesis or organogenesis). Infection; exposure to medication, alcohol, drugs, and toxins; maternal illness (diabetes, hypothyroidism, hypertension, malnutrition), and gestational disorders. Perinatal factors Occurring around the time of delivery. Neonatal septicaemia; pneumonia; meningitis/encephalitis; other congenital infections; problems at delivery (asphyxia, intracranial haemorrhage, birth injury); other newborn complications (respiratory distress, hyperbilirubinaemia, hypoglycaemia). Postnatal factors Occurring in the first years of life. CNS infections, vascular accidents, tumours; causes of hypoxic brain injury (e.g. submersion); head injury (e.g. RTAs, child abuse); exposure to toxic agents; psychosocial environment (i.e. deprivation). Other disorders of unknown aetiology (see p. 711) e.g. cerebral palsies, epilepsy, autistic spectrum disorders, childhood disintegrative disorders. P.693
Types of malformation and the timing of the causative event

Timing (in gestation) CNS event Malformation
3–7 weeks Dorsal induction Anencephaly, encephalocele, meningomyelocele, other neural tube closure defects
5–6 weeks Ventral induction Prosencephalies and other faciotelencephalic defects
2–4 months Neuronal proliferation Microcephaly or macrocephaly
3–5 months Neuronal migration Gyrus anomalies and heterotopias
6 months (to 1st year of life) Neuronal organisation Myelination
Disturbed connectivity (dendrite/synapse formation)
Disturbed proliferation of oligodendrocytes and myelin sheets

Assessment of causation This requires comprehensive history taking from the parents (examination of prenatal records), and a careful physical examination of the child. Factors in the history

  • Family history Parents: ages; consanguinity; medical history; any previous pregnancies (including abortions, stillbirths). Wider family: any history of LD; specific cognitive impairments; congenital abnormalities; neurological or psychiatric disorders.
  • Gestational history General health and nutrition; maternal infections; exposure to medication, drug and alcohol use, toxins, radiation; chronic medical conditions; history of pre-eclampsia, abnormal intrauterine growth, or foetal movements.
  • Birth of child Gestational age; multiple pregnancy (birth order); duration of labour; mode of delivery; any complications; any placental abnormalities. Examination of birth records (Apgar scores, weight, length, head circumference).
  • Neonatal history Need for special care (respiratory distress, infections, hypoglycaemia, hyperbilirubinaemia), baby checks (physical examination, Guthrie test).
  • Childhood history Weight gain, growth pattern, feeding pattern, sleeping pattern, early developmental milestones. History of childhood illnesses (esp. CNS infections or seizures, metabolic/endocrine disorders) and accidents. General systemic enquiry.

Physical examination

  • Look for evidence of any dysmorphic features and note whether these are seen in close relatives, (e.g. skin—pigmentation, dermatoglyphics; facial features; musculoskeletal abnormalities).
  • Full physical examination of all systems including neurological examination for localising signs.
  • If suggested by the history/examination, ophthalmological and audiological examinations should be arranged.


  • Standard routine tests will include FBC, U&Es, LFTs, TFTs, glucose, infection screening (blood and urine), and serology (ToRCH—toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus; HIV).
  • Where dysmorphic features are evident, or physical signs indicate, arrange X-rays of skull, vertebrae, chest, abdomen, hands, feet, and long bones; cardiac/abdominal ultrasound.
  • If metabolic disorder is suspected (e.g. progressive course) arrange screening tests of blood and urine.
  • If genetic disorder suspected arrange for karyotyping (G-banding, high resolution banding, fluorescence in situ hybridization—FISH) or other more specific genetic tests (e.g. FraX DNA testing).
  • Other more detailed investigations may include neurophysiological tests (EEG, evoked potentials), neuroimaging (cranial ultrasound, CT/ MRI, functional imaging), (neuro)pathological examination (fibroblast culture; biopsies—muscle, skin, rectum).

Overview of management approaches (1)—considerations and choices Cautionary notes

  • Attributing ‘treatment success’ to a particular intervention may miss the ‘real’ reason for improvement e.g. return of familiar carer, more structured environment (if admitted to specialist centre), or treatment effects on ‘undiagnosed’ primary condition (e. g. anticonvulsant used for aggressive behaviour may actually be treating underlying epilepsy).
  • Many conditions may run relapsing-remitting courses, leading to erroneous conclusions about effectiveness of an intervention, which only become clear when symptoms return despite treatment.
  • Improvement (or worsening) of symptoms may reflect normal maturational processes or, conversely, further pathological degeneration.
  • Because of the wide variation in aetiology (genetic, environmental, psychological, social) and the complexity (and variable degree) of cognitive impairments, most trials of treatment are by nature empirical. Most management plans will inevitably be individually tailored and the current ‘evidence base’ for many treatment modalities is limited.
  • Issues of consent to treatment should be seriously considered in a population who may have varying degrees of capacity (see Ethics and the law section, pp. 820, 821, 822, 823).

A therapeutic environment Provision of care and support should always be within an appropriate setting. Support may be: general (care provided by usual carers, schools, community teams) and/or specific (addressing particular needs e.g. special education, parental support groups, physical or psychiatric problems, maladaptive behaviours). Although, in general, every effort will be made to sustain a ‘normal’ environment (i.e. remaining at home, integration into ‘mainstream’ schools, use of local community resources), often more specialised environments are necessary (see below). Factors influencing management choices

  • The nature of the problem (i.e. biological, psychological, social).
  • The degree and aetiology of the LD.
  • Comorbid physical conditions (which may restrict choice of medication).
  • Situational factors (i.e. practicalities of instituting various treatment options, supports, ability to monitor progress).

Admission to specialist environments Sometimes disabilities or problems may be too severe or too complex to manage with standard community resources:

  • The degree of LD or the specific cognitive impairments require well-structured, predictable environments that cannot be provided elsewhere.
  • The degree of physical impairment requires more intensive specialist nursing, or a safer environment where medical care is close at hand (e.g. severe treatment-resistant epilepsy).
  • P.697

  • The severity of behavioural problems prohibits management at home (e.g. abnormally aggressive or disinhibited behaviour which constitutes a serious risk of harm to themselves or others).
  • The person requires treatment for a comorbid psychiatric disorder, which has failed to respond to initial treatment.

Other reasons may include:

  • Respite placements to allow individuals and their families some relief from the intensity of long-term care.
  • Assessment of complex problems—to disentangle environmental from illness factors, or where treatment requires close monitoring.
  • ‘Crisis’ admissions due to an acute breakdown of usual supports.

Overview of management approaches (2)—treatment methods Behavioural treatments May be used to help teach basic skills (e.g. feeding, dressing, toileting), establish normal behaviour patterns (e.g. sleep), or more complex skills (e.g. social skills, relaxation techniques, assertiveness training). Behavioural techniques may also be used to alter maladaptive patterns of behaviour (e.g. inappropriate sexual behaviour, phobias). Cognitive therapies and CBT For borderline, mild, or moderate LD, cognitive approaches may be adapted to the level of intellectual impairment. These may be effective in the teaching of problem-solving skills, the management of anxiety disorders and depression, dealing with issues of self-esteem, anger management, and treatment of offending behaviours (e.g. sex offenders). Psychodynamic therapies May be helpful in addressing issues of emotional development, relationships, adjustment to life events (e.g. losses, disabilities, and bereavement). The range of approaches varies from basic supportive psychotherapy, to more complex group and family therapies. Pharmacological treatments Cautions

  • Comorbid physical disorders (e.g. epilepsy, constipation, cerebral palsy) increase the need to closely monitor adverse effects.
  • Atypical responses such as increased (or reduced) sensitivity, and ‘paradoxical’ reactions are more common, hence low doses and gradual increases in medication are advisable.
  • The evidence base for many drug treatments is lacking and many claims for efficacy are at best based on small, open, uncontrolled trials.

Antipsychotics For the treatment of comorbid psychiatric disorders (e.g. schizophrenia and related psychosis) and acute behavioural disturbance. May also be effective in managing autistic spectrum disorders, self-injury, social withdrawal, ADHD, and tic disorders. Antidepressants Effective for the treatment of depression, OCD, and other anxiety disorders. They have also been used in the management of violence, self-injury, ‘non-specific’ distress, and other compulsive behaviours. Anticonvulsants There is some evidence for the use of anticonvulsants in the treatment of episodic dyscontrol (e.g. carbamazepine), but this may be due to better control of underlying epilepsy. P.699
Lithium Aside from the treatment of bipolar affective disorder and augmentation of antidepressant therapy, lithium may have some utility in reducing aggressive outbursts. β-Blockers May be useful in conditions of heightened autonomic arousal (e.g. anxiety disorders) which may be at the root of aggressive behavioural disturbance. Stimulants (e.g. methylphenidate) For the treatment of ADHD (see pp. 576, 577, 578). Opiate antagonists (e.g. naltrexone) May be effective in the treatment of repetitive self-injury. Anti-libidinal drugs (e.g. cyproterone acetate and medroxyprogesterone, which reduce testosterone levels) Used in the treatment of sexual offending (see p. 467). P.700
Down’s syndrome1 Down’s syndrome is the most common genetic cause of LD. It is due to trisomy of chromosome 21. Its main features are LD and associated characteristic facies and habitus. Although Down’s syndrome is diagnosed at birth, LD only becomes evident at the end of the first year of life, with subsequent delayed developmental milestones. The IQ in adults is most often below 50 (range: low to high/moderate LD). Those who survive into their 40s and 50s show pathological brain changes similar to Alzheime’s disease (AD). Aetiology Risk factors for giving birth to a child with Down’s syndrome: being aged over 40yrs; having a previous child with the syndrome; and Down’s syndrome in the mother (although pregnancy is rare). Incidence per 1000 living births is approx. 0.5 for a woman under 25, 0.7 under the age of 30, 5 under 35, 25 under 40, and 34.6 over the age of 45. Despite this, most children with Down’s syndrome (70–80%) are born to mothers under the age of 35 (due to the higher number of pregnancies in younger women). Genetics Full trisomy 21 (non-disjunction) in -95% of cases. Robertson translocations in -5% (of which -45% show fusion—usually 14 and 21, also 13/15/22 and 21 described). Mosaicism (a mixture of normal and trisomic cell lines) -2–5%: IQ can be in the 70s and physical features may be less marked. Clinical features

  • General Short stature (mean 1.4–1.5m), overweight (-30%), muscular hypotonia.
  • Head and neck Brachycephaly and reduced AP diameter, maxilla reduced more than mandible, underdeveloped bridge of nose, eyes close together, Brushfield’s spots—grey or very light yellow spots of the iris, epicanthic fold, low-set ears, high-arched palate, protruding tongue, instability of atlanto-axial joint, narrowed hypopharynx (may lead to sleep apnoea).
  • Congenital heart defects (-50%) e.g. ASD, VSD, mitral valve disease, patent ductus arteriosus.
  • Congenital GI abnormalities Oesophageal atresia, Hirschprung disease, umbilical and inguinal hernia.
  • Hands Short broad hands with a single palmar crease (simian crease), syndactyly (webbed fingers), clinodactyly (incurving of fingers), and altered dermatoglyphics.
  • Eye defects Strabismus -20%, myopia -30%, blocked tear ducts, nystagmus, late-life cataracts, keratoconus.
  • Hearing defects Structural anomalies may lead to recurrent otitis media, sensorineural deafness.
  • Immunological abnormalities Raised IgG and IgM, lowered T-lymphocytes.
  • Endocrine abnormalities Thyroid dysfunction (hypothyroidism -20%), diabetes.
  • CNS abnormalities Reduced brain weight -10–20%, reduced gyri, cortical thinning, underdeveloped middle lobe of cerebellum, reduced P.701
    neuronal numbers in cerebellum/locus coeruleus/basal forebrain, reduced cholinergic neurones, neuropathological changes similar to AD (in those over 40yrs), epilepsy (5–10%).

Sexual development

  • Males: normal course; delayed puberty; problems with spermatogenesis (unless mosaic).
  • Females: normal onset of menstruation; fertile, but problems with ovulation and follicular growth; early menopause.

Psychiatric comorbidity Associated with -18% of children and -30% of adults with Down’s syndrome (usually depression -10%; less commonly bipolar affective disorder, OCD, Tourette’s disorder, schizophrenia, increased risk of autism). References 1 James Langdon Down remarked in his original observations on ‘mongolism’ (1866) that he was surprised it had not been described earlier. In fact, the first description of this syndrome was made in 1838 by Esquirol (1772–1840), with similar observations reported by Séguin (1812–1880) in 1844. The typical phenotype has also been noted in paintings dating from the Middle Ages. In 1959 the chromosomal abnormality leading to Down’s syndrome was found by the French human geneticist Jérôme Lejeune (1926–1994). In doing so, Lejeune became the first researcher to elucidate the genetic mechanism of an inherited disorder. P.702
Sex chromosome disorders Turner’s syndrome Sex chromosome monosomy; karyotype 45, XO (i.e. phenotypically female); LD rare. Trisomy X Sex chromosome trisomy; karyotype 47, XXX; 1:1000 female births. Clinical features Slight increase in height, -70% have learning disorder (usually mild), some evidence of reduced fertility (children have normal karyotypes), possibly increased incidence of schizophrenia. Klinefelter’s syndrome Sex chromosome trisomy; karyotype 47, XXY; 1:1000 male births (50% due to paternal and 50% maternal non-dysjunction). Clinical features Variable degree of development of secondary sexual characteristics with hypogonadism, scant facial hair (90%), gynaecomastia (50%). Taller than average (-4cm), asthenic body build, median IQ -90 with skewed distribution—most in 60–70 range, uncertain association with psychiatric disorders. XYY male Sex chromosome trisomy; karyotype 47, XYY; 1:1000 male births. Clinical features Controversial suggestion of higher incidence in prison populations, IQ may be slightly lower than average, behavioural problems commonly seen. P.703
Deletions and duplications α-Thalassaemia mental retardation Small deletion; karyotype 16pter-p13.3 (cryptic terminal deletion). Clinical features LD. Angelman (‘Happy puppet’) syndrome Microdeletion (60–75% of cases); karyotype 15q11-q13; 1:20000–30000; a contiguous gene syndrome (the complement of PWS) with 80% due to deletion of maternally derived chromosome 15, 2% uniparental disomy (UPD)—i.e. inheritance of 2 genes from the same parent (paternal), the remainder due to direct mutations. Clinical features Ataxia (jerky limb movements, gait problems); epilepsy (86%); paroxysms of laughter; absence of speech; facial features (blond hair, blue eyes, microcephaly, flattened occiput, long face, prominent jaw, wide mouth, widely-spaced teeth, thin upper lip, mid-facial hypoplasia); severe/profound LD; other behaviours (hand flapping, tongue thrusting, mouth movements); other problems (URTIs, ear infections, obesity). Crit du chat Partial monosomy; karyotype 5p- (varies from deletion of a small band at 5p15.2 to the entire arm of 5p); usually sporadic, occasionally inherited; 1:20000–50000. Clinical features ‘Cat-like’ cry (possibly due to abnormal laryngeal development), microcephaly, rounded face, hypertelorism, micrognathia, dental malocclusion, epicanthic folds, low-set ears, hypotonia, severe/profound LD. Puberty occurs normally and some may survive to adulthood. Di George (Velo-cardio-facial) syndrome Microdeletion; karyotype 22q11.2; incidence 1:5000.Clinical features -50% have LD (mild: 2/3; moderate: 1/3), cardiac abnormalities (75%: Fallot tetralogy, VSD, interrupted aortic arch, pulmonary atresia, truncus arteriosis), facial features (microcephaly, cleft palate/submucous cleft, small mouth, long face, prominent tubular nose, hypoplasia of adenoids—nasal speech, bulbous nasal tip, narrow palpebral fissure, minor ear abnormalities, small optic discs/tortuous retinal vessel/cataracts), hypocalcaemia (60%—seizures, short stature, hearing problems, renal problems, inguinal/umbilical hernia), hypospadias (10% of males), long, thin hands (hypotonia and hyperextensible fingers), associated behavioural and psychiatric disorders (including schizophrenia, blunted/inappropriate affect). Miller-Dieker syndrome Microdeletion; karyotype 17p13.3. Clinical features Lissencephaly, profound LD. Prader-Willi syndrome (PWS) Microdeletion; karyotype 15q11-q13; 1:10000–1:20000; the complement of Angelman syndrome; 75% deletion of paternally derived chromosome 15, 25% UPD (maternal). M:F = 4:3. Clinical features Neonates Hypotonia, sleepiness, unresponsiveness, narrow bifrontal diameter, triangular mouth (feeding difficulties and swallowing problems), strabismus, acromicria (shortness of extremities). Childhood/adolescence Short stature, hypogenitalism (cryptorchidism, micropenis; amenorrhoea), behavioural disorders (over-eating and obesity, self-injurious behaviour), mild-moderate LD, speech abnormalities, sleep disorders. Associated features Small hands and feet, cleft palate, almond-shaped eyes, strabismus, incurved feet, clubfoot, congenital hip dislocation (abnormalities of the knee and ankle), scoliosis. Other physical P.705
problems Diabetes, GI problems (obstruction, duodenal ulcer, rectal prolapse, gall stones), heart disease, respiratory (asthma, cor pulmonale), renal calculi, hearing deficits, hypothermia. Rubenstein-Taybi syndrome Microdeletion of the gene encoding human cAMP-regulated enhancer binding protein; karyotype 16p13.3; incidence 1:125000. Clinical features LD and dysgenesis of the corpus callosum. Other features: broad thumbs and great toes; persistence of foetal finger pads; facial features (short upper lip, pouting lower lip, maxillary hypoplasia, beaked nose, slanted palpebral fissure, long eyelashes, ptosis, epicanthic fold, strabismus, glaucoma, iris coloboma); cardiac problems (pulmonary stenosis and hypertension, mitral vale regurgitation, patent ductus arteriosus); propensity to keloid formation; genitourinary features (hypoplastic kidneys, cryptorchidism, shawl scrotum); GI problems (constipation, megacolon); collapsible larynx (leading to sleep apnoea); epilepsy (25%); behavioural problems (sleep problems, stereotypies e.g. rocking, self-injurious behaviour). Smith-Magenis syndrome Rare—incidence 1:50000; deletion in 17p11.2. Clinical features Moderate LD; facial features (brachycephaly, broad face, flattened mid-face, strabismus); myopia; short broad hands; upper limb deformity; insensitivity to pain. Behavioural problems ‘Self-hugging’ posturing, aggression, self-injury, hyperactivity, severe sleep problems, other autistic features. Williams syndrome Small deletion; karyotype 7q11.23 (possibly gene for elastin or protein kinase—LIMKI); 1:55000 live births; may also be related to excessive maternal vitamin D intake. Clinical features Hypercalcaemia (in -50%) with supravalvular aortic stenosis and unusual facies. Neonates May be irritable, have feeding problems and failure to thrive. Childhood Growth retardation, ‘elfin’ facial features, hoarse voice, premature wrinkling and sagging of the skin, cardiovascular anomalies (e.g. supravalvular aortic stenosis), urinary tract abnormalities (asymmetrical kidneys, nephrocalcinosis, bladder diverticuli, urethral stenosis), pulmonary artery stenosis, mild to moderate LD (verbal often better than visuospatial and motor abilities). Often there is abnormal attachment behaviour (manifest as anxiety, poor peer relationships, hypersensitivity, or conversely as social disinhibition, excessive friendliness). Wolf-Hirschhorn syndrome Partial monosomy; karyotype 4p-. Clinical features Severe LD; many survive to adulthood. P.706
Autosomal dominant conditions This group of disorders is also termed the phakomatoses—a variety of conditions with neurocutaneous signs. Neurofibromatosis Caused by a number of genetic conditions, 1:40000; variable association with LD. Von Hippel-Lindau syndrome A rare genetic condition associated with angiomatous tumours in various areas of the body and LD. Sturge-Weber syndrome Not inherited, but associated with ‘port wine stains’, angiomas of the meninges in the temporal and occipital areas, with LD, epilepsy, and hemiparesis. Tuberous sclerosis (TSC) Occuring in 1:7000–10000; M = F. Clinical features Varying degree (usually severe) of LD (50%), seizures (e.g. ‘Salaam attacks’ and other types, in 90%), hamartomas of the CNS (including the retina) as well as ependymomas and astrocytomas, facial angiofibroma, adenoma sebaceum, depigmented skin patches (‘ash leaf spots’ in 96%), shagreen patches, depigmented naevi, subcutaneous nodules, ‘café-au-lait’ spots, fibromas of the nails, pitted tooth enamel, hypoplasia, and occasionally tumours of the heart (rhabdomyeloma, hamartoma), kidney problems (Wilm’s tumour, renal cysts), olfactory hamartomas, hypertension, and aortic aneurysm. Subtypes TSC1: 1:12000; associated with a gene (for hamartin—believed to be tumour-suppressant) near the ABO blood group locus on chromosome 9 (9q34—40% of cases). TSC2: associated with a gene for tuberin (a guanosine triphosphatase-activating protein also believed to be tumour-suppressant) on chromosome 16 (16p13.3-); more psychiatric and behavioural problems.TSC 3: a rare translocation of a gene on chromosome 12. Autosomal recessive conditions These conditions include some of the lysosomal storage diseases e.g. mucopolysaccaride storage—Hurler syndrome, Sanfillipo disease (see below), sphingolipid storage*—Tay-Sachs disease, Niemann-Pick disease (sphingomyelins), glucoprotein storage—sialidosis; phenylketonuria; and rare disorders such as Laurence-Moon syndrome and Joubert syndrome (see below). Phenylketonuria A preventable cause of severe LD, due to deficiency of phenylalanine hydroxylase (long arm of chromosome 12), leading to phenylalaninaemia and phenylketonuria; prevalence 1:15000; diagnosed postnatally (‘Guthrie test’). Clinical features Fair hair/skin and blue eyes (lack of pigment—tyrosine deficiency), neurological signs (stooped posture, broad-based gait, increased tone and reflexes, tremor, stereotypes movements). Behavioural problems Hyperactivity, temper tantrums, perseveration, echolalia. Management Supervised early dietary restriction of phenylalanine. Prognosis Even with dietary treatment, lower than average IQ. P.707
Sanfillipo disease Due to disorders of the breakdown of heparan sulphate, of which there are 4 subtypes (types A–D). Prevalence 1:25000–325000. Clinical features Severe LD, claw hand, dwarfism, hypertrichosis, hearing loss, hepatosplenomegaly, biconvex lumbar vertebrae, joint stiffness. Behavioural problems Restlessness, sleep problems, challenging behaviour. Aetiology Type A (most severe, most common) mapped to 17q25.3 (heparan sulphate sulphatase).Type B 17q21 (N-acetyl-α-D-glucosaminidase).Type C on chromosome 14 or 21 (acetyl-CoA-α-glucosaminide-N-acetyltransferase). Type D 12q14 (N-acetyl-α-D-glucosamine-6-sulphatase). Prognosis Poor, many die between 10–20yrs of respiratory tract infections. Hurler syndrome Due to deficiency in A-L-iduronidase (4p16.3); incidence 1:76000–144000. Clinical features Progressive LD (eventually severe/profound), skeletal abnormalities (short stature, kyphosis, flexion deformities, claw hand, long head, characteristic facial appearance), hearing loss, respiratory and cardiac problems, hepatosplenomegaly, umbilical/inguinal hernia. Prognosis Poor, some survive to 20s; may benefit from allogenic bone transplantation. Laurence-Moon syndrome Associated with multiple loci (11q13, 11q21, 15q22, 3p13); prevalence 1:125000–160000 (higher in Bedouins of Kuwait and Newfoundland). Also known as Laurence-Moon-Biedl syndrome (incorporating Bardet-Biedl syndrome which shares clinical features, but additionally there is central obesity and polydactyly). Clinical features Mild-moderate LD, short stature, spastic paraparesis, hypogenitalism (most males are infertile), night blindness (due to red cone dystrophy), NIDDM, renal problems (diabetes insipidus, renal failure). Joubert syndrome Exceptionally rare, no loci identified, but recessively inherited. Clinical features Severe LD, characteristic hyperpnoea (‘panting like a dog’), cerebellar dysgenesis, hypotonia, ataxia, tongue protrusion, facial spasm, abnormal eye movements, cystic kidneys, syndactyly/polydactyly. Behavioural problems Self-injury. Prognosis Poor—no specific treatments. P.708
X-linked recessive conditions These include other lysosomal storage diseases e.g. mucopolysaccaride storage—Hunter syndrome (see below); trihexosylceramide storage—Fabry disease and other extremely rare conditions such as Lesch-Nyhan syndrome and oculocerebrorenal syndrome of Lowe. Hunter syndrome Caused by iduronate sulphatase deficiency (mapped to Xq27-28); incidence 1:132000–280000 (more common in male Ashkenazi Jews: 1:34000). Only 20% have complete depletion of iduronate sulphatase and two subtypes are recognised: Type A Progressive LD and physical disability, with death before age 15yrs. Type B Milder form, with minimal intellectual impairment and better prognosis. Clinical features Dyostosis (dwarfism, grotesque facies ‘gargoylism’, degenerative hip disease, joint stiffness, claw hand, pes cavus, cervical cord depression), eye defects (retinitis pigmentosa, papilloedema, hypertrichosis), umbilical/ inguinal hernia. Lesch-Nyhan syndrome An extremely rare X-linked recessive condition, due to a mutation in HPRT gene (hypoxanthinephosphoribosyl transferase) on the short arm of chromosome Xq26-27, with a nearly total loss of the enzyme leading to hyperuricaemia. Prognosis is poor and most affected individuals die in early adulthood. Clinical features Children appear healthy at birth, dystonias become apparent around 3–4 mths with delayed developmental milestones, later there is development of spasticity, choreoform movements and transient hemiparesis (which may be misdiagnosed as cerebral palsy), variable degree of LD (usually severe), microcephaly is common, -50% develop epilepsy. Behavioural problems Around age 2 yrs (sometimes not until adolescence) self-mutilating behaviours may be seen (biting of lips, inside of mouth, fingers). Sometimes there is an episodic pattern, and some may show a reduction in frequency and severity after age 10yrs. May be associated with verbal and physical aggression. There is no clear cause for this behaviour—CNS findings include reduction in dopamine in the basal ganglia and at synaptic terminals (but not in the cell bodies of the substantia nigra), with other monoaminergic systems apparently intact. Management Even treating hyperuricaemia does not appear to reduce behavioural problems; however there is some evidence for use of SSRIs. Oculocerebrorenal syndrome of Lowe Very rare X-linked recessive condition (Xq24-26); incidence 1:200000. Clinical features Moderate-severe LD (up to 25% have normal IQ), short stature, hypotonia, epilepsy (-30%), eye problems (e.g. congenital cataracts), renal problems (tubular dysfunction). Behavioural problems Temper tantrums, hand-waving movements, self-injury (-70%—esp. in early adolescence). P.709
X-linked dominant conditions Fragile X syndrome The most common inherited cause of LD, affecting -1:4000 males and 1:8000 females, with X-linked dominant transmission. Penetrance is low, but greater in males than females (due to the ‘protective’ effects of the second normal X chromosome in females). Gene sequence has been cloned1 and designated FMR-1. The syndrome is associated with a large sequence of triplet repeats (CGG)n at a fragile site on the X chromosome (Xq27.3). In affected males ‘n’ > 230–1000+, in transmitting males and obligate females n = 43–200, and in the general population n = 6–54 (mean 30). Clinical features Variable, subtle, and often cannot be detected before adulthood. May include: large testicles and ears, smooth skin, hyperextensible fingers, flat feet, mitral valve prolapse, inguinal and hiatus hernia, facial features (long, narrow face with underdevelopment of the mid-face, macrocephaly), epilepsy (-25%), variable LD (borderline to profound), behavioural features appear to be similar to those seen in ADHD and autism: hand flapping / waving, repetitive mannerisms, shyness, gaze avoidance, poor peer relationships, communication difficulties (e.g. delayed language development, conversational rigidity, perseveration, echolalia, palilalia, cluttering and overdetailed/circumstantial speech), psychiatric problems (e.g. mood and personality disorders). NB General domestic and daily living skills may be excellent. Brain imaging: reduced posterior cerebellar vermis, enlarged hippocampus and caudate nuclei, enlarged ventricles. Other disorders with ‘fragile’ sites Two other fragile sites have been found on the X chromosome. The original ‘fragile X’ site has hence been designated ‘FRAX A’. FRAX E, caused by FMR-2 mutation is also associated with mild LD, with an incidence of 1:100000, and 200–1000 triplet repeats. FRAX F has not (yet) been associated with any disorder. Another fragile site has been located on chromosome 16 (FRA 16) associated with a large GCC triplet expansion—but no specific clinical disorder. Aicardi syndrome Rare (only 200 reported cases—all female); dysgenesis of the corpus callosum and cerebrum, with severe LD; prognosis poor (often death in infancy). Clinical features Microcephaly, facial asymmetry, low-set ears, eye lesions (chorioretinal lacunae), hypotonia, scoliosis, epilepsy. Behavioural problems 25%—aggression, lack of communication, tiredness/sleep problems, self-injurious behaviour. References 1 Verkerk AJ, Pieretti M, Sutcliffe JS, et al (1991) Identification of a gene (FMR-1) containing a CGG repeat coincident with a breakpoint cluster region exhibiting length variation in fragile X syndrome. Cell 65, 905–14. P.710
Non-genetic causes of LD Congenital hypothyroidism A treatable cause of mental and growth retardation due to loss of thyroid function; incidence 1:3500–4000, but now screened for neonatally and treated early with thyroxine. If untreated, leads to typical clinical picture of lethargy, difficulty feeding, constipation, macroglossia, and umbilical hernia. Foetal alcohol syndrome (FAS) One of the major causes of LD, incidence 0.2–3 per 1000 live births. 10–20% of cases of mild LD may be caused by maternal alcohol use. Important factors include: level of drinking, bingeing, other drug use (including smoking), genetic variation, and low socio-economic status. May be due to the effects of alcohol on NMDA receptors, which may alter cell proliferation. Clinical features Perinatal problems Signs of alcohol withdrawal (irritability, hypotonia, tremors, seizures); Facial features Microcephaly, small eye fissures, epicanthic folds, short palpebral fissure, small maxillae and mandibles, underdeveloped philtrum, cleft palate, thin upper lip; Growth deficits Small overall length, joint deformities; CNS features High incidence of mild LD, associated behavioural problems (hyperactivity, sleep problems), optic nerve hypoplasia (poor visual acuity), hearing loss, receptive and expressive language deficits; Other physical abnormalities ASD, VSD, renal hypoplasia, bladder diverticuli. Other toxins e.g. cocaine, lead, bilirubin, coumarin anticoagulants, phenytoin. Infective agents ToRCH, syphilis (treponema pallidum), HIV, and other causes of meningitis and encephalitis. Hypoxic damage Secondary to placental insufficiency, pre-eclampsia, birth trauma, severe prematurity, ‘small for dates’ babies (foetal growth retardation), or multiple pregnancy. CNS and skull developmental abnormalities Micro-and macrocephalies, spina bifida, hydrocephalus, craniostenosis, callosal agenesis, lissencephalies, holoprosencephalies. P.711
Disorders of unknown aetiology This includes a broad range of disorders associated with LD, but for which a clear aetiology is as yet undetermined e.g. cerebral palsies, epilepsy, autistic spectrum disorders (see pp. 584, 585), childhood disintegrative disorders (see below), and other clearly defined syndromes with a suspected (but not yet proven) genetic basis (e.g. Cornelia de Lange syndrome—see below). Rett syndrome Exclusively affecting girls, incidence 1:10000–15000. Clinical features Normal development up to 18–24mths, followed by development of abnormal involuntary movements (hand flapping and hand wringing), often with autistic features (may be misdiagnosed). By age 5yrs up to 72% have epilepsy, and general progression is to spasticity of the limbs, plateauing for a short time (associated with improved social skills), before further motor deterioration with marked spasticity, rigidity, muscle wasting, contractures, and deformities. Behavioural problems Low mood, anxiety (with marked distress—often situation-specific), self-injury (40–50%), sleep problems (often involving laughing). Aetiology Unknown, may be associated with MECP2 gene at Xq28. Prognosis Characteristic progression to severe disability with moderate to severe LD. Disintegrative disorder Clinical features Characterised by normal development until the age of -4yrs, followed by profound regression with disintegration of behaviour, loss of acquired language and other skills, impaired social relationships, and stereotypies. Aetiology Unknown, but may follow minor illness or viral encephalitis (e.g. measles). Prognosis Poor, with development of severe LD. Cornelia de Lange syndrome (Brachmann-de Lange syndrome) Usually IQ is below 60 (range 30–86), prevalence 1:50000–100000, mode of inheritance unknown (possibly autosomal dominant). Clinical features Hypertrichosis (hirsuitism, synophyrs, long eyelashes), facial features (depressed nasal bridge, eye abnormalities, prominent philtrum, thin lips, down-turned mouth, anteverted nostrils, bluish tinge around eyes/nose/mouth, widely-spaced teeth, high-arched palate, low-set ears, micrognathia, short neck), limb deformities (esp. upper limbs), cryptorchidism/hypoplastic genitals (males), small umbilicus, low-pitched cry, small nipples. Associated with GI problems, congenital heart defects, visual and hearing problems, skin problems, epilepsy, and death in infancy. Behavioural problems Expressive language deficits, feeding difficulties, sleep disturbance, self-injury, temper tantrums, mood disorders, and autistic features. P.712
Epilepsy and LD Epilepsy represents a particular diagnostic challenge when it occurs in people with LD. It may begin at any age, presentations may change over time, and multiple forms may occur in the same individual. The prevalence of epilepsy is -40% in the hospitalised LD population and is higher in severe (30–50%) than mild (15–20%) LD Common pitfalls

  • Epilepsy may be misdiagnosed in patients with LD, particularly when there is a history of sudden unexplained aggression, self-mutilation, and other ‘bizarre’ behaviours, including abnormal or stereotyped movements, fixed staring, rapid eye blinking, exaggerated startle reflex, attention deficits, or unexplained intermittent lethargy. (If antiepileptic medication has been previously prescribed for these kinds of presentations, consider careful withdrawal with close monitoring.)
  • Non-epileptic (pseudo) seizure disorder can also occur in patients with epilepsy.
  • Epilepsy-related behaviours may also be confused for psychiatric problems e.g. hallucinations in simple (somatosensory) partial seizures; psychosis-like episodes during complex partial seizures (esp. temporal or frontal lobe); or post-ictal confusion.


  • History and examination May be difficult to obtain accurate information, often relying on third-party information (home video may be useful). Try to exclude other differential diagnoses (e.g. infection, trauma, hypoglycaemia, hyperventilation, withdrawal from drugs or alcohol, over-sedation, localising signs of intracranial pathology, evidence of movement disorders). Also conduct a MSE, focusing on observed behaviours, identification of any stressors (esp. if anxiety-provoking).
  • Investigations Baseline laboratory tests—FBC, U&Es, LFTs, glucose. Consider EEG and CT/MRI (in complex cases video-EEG monitoring may be very useful), PET or SPECT (to detect areas of hypometabolism).


  • Epilepsy is commonly associated with numerous causes of LD e.g. Down’s syndrome (5–10%), fragile X (25%), Angelman syndrome (90%), Rett syndrome (90%). This may be due to shared aetiologies such as alterations in neuronal development and function, or co-associated brain lesions (haemorrhage, ischaemia, neoplasm, vascular malformation).
  • Frequent epileptic seizures may lead to (or worsen) permanent loss of intellectual functioning (e.g. ‘acquired epileptic aphasia’/Landau-Kleffner syndrome, progressive partial epilepsies such as epilepsia partialis Kozhevnikov or Rasmussen syndrome type 2) emphasising the need for early diagnosis and treatment to prevent often fatal progression.

Epilepsy syndromes in infancy and childhood Infancy Early infantile epileptic encephalopathy due to congenital or acquired abnormal cortical development; early myoclonic epileptic encephalopathy P.713
possibly due to metabolic disorders; infantile spasms/West syndrome1 due to intrauterine infections (toxoplasmosis, CMV, rubella), Down’s syndrome, tuberous sclerosis, progressive degenerative disorders, or intracranial tumours; severe myoclonic epilepsy. Childhood A variety of other myoclonic epilepsy syndromes are recognised: Lennox-Gastaut syndrome, myoclonic-astatic epilepsy (Doose syndrome), progressive myoclonus epilepsies (Baltic or Lafora disease), Northern epilepsy. Treatment NB This is essentially the remit of the neurologist, not the psychiatrist– liaison with other specialists is vital. Choice of treatment will depend upon a number of factors:

  • Accurate classification of the type of seizures / epilepsy syndrome
  • Possible drug interactions
  • Minimising side-effects (esp. cognitive impairment)

Points to note:

  • Behavioural problems may be associated with antiepileptic drugs, and may be more common in patients with brain injury or LD (e.g. phenobarbitone, primidone, benzodiazepines, vgabatrin).
  • Communication difficulties may make assessment of side-effects more difficult.
  • For intractable epilepsy, neurosurgery may be an option, but is not without significant ethical considerations.

Prognosis There is wide variation in outcome; however up to 70% of patients with LD can achieve good control of their epilepsy without major side-effects. References 1 West syndrome is the triad of infantile spasms, mental retardation, and hypsarrhythmia (characteristic EEG finding of chaotic intermixed high-voltage slow waves and diffuse asynchronous spikes). P.714
Psychiatric comorbidity in the LD population Although originally thought to be mutually exclusive, it is now clear that psychiatric disorders do occur more frequently in the LD population than the general population. Confusion of primary and secondary handicap may lead to underdiagnosis. The lack of longitudinal studies makes any prediction of outcome speculative at best. Schizophrenia Clinical features Age of onset tends to be earlier (mean 23yrs), with few differences in symptomatology, except in severe LD where there may be unexplained aggression, bizarre behaviours, mood lability, or increased mannerisms and stereotypies. Aetiology Genetic factors are important (associated with FHx). Co-association suggests possible contiguous gene deletions, or one underlying genetic condition presenting with multiple clinical presentations. Bipolar affective disorder Prevalence is estimated to be greater than the general population (2–12%), with difficulty in making the diagnosis in severe LD. Symptom ‘equivalents’ may include: hyperactivity, wandering, mutism, temper tantrums. Depressive disorder Clinical features Biological features tend to be more marked, with diurnal variations. Suicidal thoughts and acts may occur in borderline-moderate LD, but are less frequent in severe LD (need to exclude other ritualistic self-injurious behaviours). Other causes of mood disturbance (e.g. perimenstrual disorders) should also be considered. Other disorders Anxiety disorders May be difficult to distinguish from depression, except where there are situational features. OCD Reported to be more prevalent in LD. Differential diagnosis: ritualistic behaviours, tic disorders, behavioural manifestations of autism/ Asperger disorder. ADHD Often a prominent feature in children with LD (up to 20%). Stimulants may help in mild LD with clear symptoms, but has no clear efficacy in severe-profound LD. Personality disorder Difficult to define, but prevalence is estimated in -20% of mild-moderate LD patients who are inpatients. P.715
Behavioural disorders and ‘challenging’ behaviour Behavioural disorders are over-represented in LD populations, ranging from minor antisocial behaviours to seriously aggressive outbursts. Prevalence estimates are 7% of the LD population: 14% for inpatients (esp. 25–29yr-olds), and 5% for those in the community (esp. 15–19yr-olds). Studies of behavioural disorders in the LD population identify 6 relatively consistent groupings of the types of pathological behaviours1 which may create a significant burden for parents/carers:

  • Aggression-antisocial
    • Antisocial behaviours Shouting, screaming, general noisiness; anal poking/faecal smearing (may reflect constipation); self-induced vomiting/choking; stealing.
    • Aggressive outbursts Against persons or property.
    • Severe physical violence Rare.
    • Self-injurious behaviour Skin picking, eye gouging, head banging, face beating (more common in severe/profound LD; prevalence 10% overall, 1–2% most sever.)
  • Social withdrawal
  • Stereotypic behaviours (some of which may be self-injurious)
  • Hyperactive disruptive behaviours
  • Repetitive communication disturbance
  • Anxiety fearfulness

When these behaviours are particularly severe, they are often termed ‘challenging’ (see opposite). Associated factors Assessment of behavioural problems should cover a number of interrelated domains:

  • Cognitive functioning Severity of intellectual impairment, language ability, memory (visual/verbal), performance of specific tasks (e.g. complex motor tasks), social comprehension.
  • Temperament Particularly high emotionality, high activity, poor sociability.
  • Physical problems e.g. epilepsy, cerebral palsy, cardiac problems, GI problems, visual/hearing impairment.
  • Medication Particularly psychotropic drugs may produce or mask cognitive, behavioural, or emotional problems. Sometimes a ‘drug holiday’ may be helpful to assess how medication contributes to the presentation.
  • Psychological factors Primary reinforcers e.g. food, drink, pain (often undetected). Secondary reinforcers e.g. praise, environment, aversive stimuli.
  • Communication difficulties Frustration of normal forms of communication.
  • Adverse experiences Common to the general population, and also particular to the LD population e.g. experience of institutions, social rejection, neglect, and emotional, physical, or sexual abuse.
  • P.717

  • Environmental factors Living conditions, stability and continuity of day-to-day activities (NB Most common precipitants: multiple short-term residential placements; multiple changes in care staff.) The quality of the care environment may be directly responsible for behavioural problems and assessment should include factors such as: social relationships, specific environmental stressors, consistency of care, and lack of stimulation.
  • Comorbidity Psychiatric disorders may complicate the presentation of behavioural problems e.g. ADHD (see p. 576); conduct disorder/oppositional defiant disorder (see p. 581); tic disorders (see p. 602); anxiety disorders (see pp. 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357)—fears/phobias, separation anxiety (see p. 590), PTSD (see p. 368), OCD (see p. 538); depressive disorder (see pp. 246, 247, 248, 249, 250, 251); bipolar disorder (see pp. 304, 305, 306, 307, 308, 309, 310, 311); pervasive developmental disorders (see p. 582). Identification and appropriate treatment may significantly improve behavioural problems.
  • ‘Behavioural phenotypes’ (see below).

Criteria for clinically significant ‘challenging behaviour’

  • At some time the behaviour has caused more than minor injuries to themselves or others, or destroyed their immediate living or working environment.
  • At least weekly behaviours requiring intervention by staff; placed them in physical danger; caused damage that could not be rectified; caused at least 1hr of disruption.
  • Behaviour has caused over a few minutes’ disruption at least daily.

Qureshi H (1994) The size of the problem. In: Emerson E, McGill P, Mansell J (Eds) Severe mental retardation and challenging behaviours: designing high quality services Chapman and Hall, London. ‘Behavioural phenotypes’ Many genetic causes of LD are associated with characteristic patterns of behaviour. Recognising these ‘behavioural repertoires’ may help in diagnosis and management, and forms the basis for ongoing research into the genetic basis of some behavioural problems. Examples include: Down’s syndrome (oppositional, conduct, and ADHD); fragile X syndrome (autism, ADHD, stereotypies e.g. hand flapping); Lesch-Nyhan syndrome (self-mutilation); Prader-Willi syndrome (OCD, multiple impulsive behaviour disorder e.g. hyperphagia, aggression, skin picking); Smith-Magenis syndrome (severe ADHD, stereotypies—‘self-hugging’, severe self-injurious behaviours, insomnia); Williams syndrome (‘pseudomature’ language ability in some; initially affectionate and engaging; later anxious, hyperactive, and uncooperative). References 1 Einfeld SL, Aman M (1995) Issues in the taxonomy of psychopathology in mental retardation. J Autism Dev Disord. 25, 143–67. P.718
Behavioural disorders—assessment and principles of management At all stages in assessment and management, it will be essential to involve parents, carers, and other allied professionals (e.g. teachers) both as sources of information and in implementing any proposed interventions. Assessment

  • Exclusion of psychiatric disorder.
  • Exclusion of physical disorder (and assessment of general state of health).
  • Assessment of physical impairments (vision, hearing, etc.)
  • Assessment of communication difficulties (including formal speech and language assessment).
  • Assessment of specific cognitive impairments (including formal psychological testing).
  • Identification of environmental and social factors.
  • Use of behavioural diaries (by carers/staff) ‘ABC’s—: antecedents, behaviours, consequences.

Management Following assessment, specific factors should be addressed—psychiatric/ physical causes, reduction of stimuli/reinforcers, modification/removal of environmental factors, social issues. Approaches may involve:

  • Educational interventions Both for families/carers (to improve understanding) and for patients (to ensure educational needs are being appropriately met in a suitable setting).
  • Social interventions To address unmet needs at home, with family/carers, or widen access to other services or facilities (to provide opportunities for social interaction and improve support networks).
  • Facilitating communication of needs Addressing impairments of hearing, vision, and language (including use of pictures, sign language, electronic speech devices).
  • Behavioural interventions Modification of behaviour using operant conditioning (e.g. removal of aversive stimuli, rewarding ‘good’ behaviour, use of appropriate attention—‘neutral’ response to attention-seeking behaviours), secondary reinforcers, modelling, ‘positive programming’.
  • Cognitive approaches At an appropriate level for degree of cognitive impairment and language abilities—may range from counselling on specific issues to simple imitation of relaxation/breathing techniques.
  • Pharmacotherapy Including specific comorbid conditions (e.g. ADHD—stimulants; OCD—SSRIs; antidepressant treatment; tic disorders—antipsychotics; epilepsy—anticonvulsants). Sometimes a trial of antipsychotic treatment may be useful for serious aggression, hyperactivity, or stereotypies (often depot; caution in epilepsy; increased risk of EPSEs). Other options for aggression, agitation, or self-injurious behaviours (mainly empirical evidence): anticonvulsants, lithium, β-blockers, buspirone. For self-injurious behaviours alone there is some evidence for opiate antagonists (e.g. naltrexone).
  • P.719

  • Physical interventions (i.e. restraint): from splints and headgear to isolation (to protect individual and others from injury/damage to property).

Any intervention should be closely monitored to ensure compliance, acceptability, and therapeutic response. In the case of medication, side-effects should be minimised and if treatment is deemed ineffective drugs should be carefully withdrawn (to avoid secondary problems). P.720
Critical periods of changing needs Adolescence This may be a difficult transitional period; issues that may require attention include:

  • Engaging with adult services Loss of the additional support provided by supported mainstream, or special schools, may lead to problems if there is not a smooth transition to adult services. Where appropriate (or available) this may include moving to social educational/ day centres. Some countries have specific legislation to ensure that needs are identified early (e.g. ‘transitional planning’ from the age of 14 under the UK Education Act 1993).
  • Social/economic independence
    • Employment Depending on the level of disability, this may be in sheltered employment, workshops, or supported open employment. Despite changing attitudes, there are considerable barriers to finding work in the open job market, although for some this may be worth pursuing.
    • Living arrangements Loss of additional social supports may actually increase the burden of care shouldered by the family. For some, the wish for independence or the lack of family support may be best met with small group homes where support may be tailored to individual needs.
  • Health and mental health needs
  • Sexual relationships Societal views may find it difficult to accept the fact that people with LD have ‘normal sexual desires’, which can be more of a problem for families/carers than the individuals themselves. Nonetheless, issues raised by appropriate sexual relationships will include consideration of contraception, understanding of the responsibilities of parenthood, issues of commitment and marriage. Many people, particularly with mild LD, are capable of being successful parents and provide a stable environment for children with appropriate support.

Later adulthood

  • Changing health needs With increasing age, health needs may be unrecognised or there may be failure to access services. Despite issues of capacity and consent to medical treatment, everyone has a right to high standards of medical care, and this ought not to be neglected.
  • Changing mental health needs These may relate to changing symptomatology over time, altered tolerance of medication, and additional specific age-related cognitive impairment (e.g. due to chronic intractable epilepsy, early onset Alzheimer’s disease in Down’s syndrome).
  • Ageing carers The ability of carers to continue to provide the same level of care for their children ought to be considered before a crisis is reached. This requires an ongoing assessment of supports. Increasing reliance on carers may also lead to social isolation, and it is prudent to raise the issue of planning for the future at an early stage. Issues of bereavement may complicate support arrangements due to the P.721
    consequent life changes (e.g. may need to move out of the family home and entail learning to be with new carers and people who will have problems of their own). There may be cultural differences in preferences and expectations, and these should be sympathetically addressed.

Family issues Having a child with LD is a major, unexpected blow to any family. Individual responses vary, but the majority of parents do adapt well to the situation and show remarkable resilience and resourcefulness. Depression is quite common in parents and should not be overlooked. Important positive factors include: having a good relationship with their partner and the support of relatives and friends. Needs and priorities will vary over time and should be identified early and addressed collaboratively with the involvement of parents and other carers in any key decisions (see opposite). Early impact Prenatal diagnostic screening can place parents in the unexpected position of having to make difficult choices even before the birth of their child. Advice and counselling are a necessary and important part of the screening process, and should not be ignored even when testing is regarded as ‘routine’. The mistaken assumption that screening ‘guarantees’ a healthy child may lead to even greater feelings of disappointment and anger, magnified further by anxious times after the birth, with a baby in a special care unit. Although some conditions can be diagnosed at birth, often parents only realise there is a problem when their child fails to reach developmental milestones, or develops seizures after an apparently ‘normal’ infancy. Often the response is one of bereavement (see p. 366) or guilt, and parents may need support to ‘work through’ their feelings. The importance of diagnosis Clear diagnosis is essential and may greatly relieve the anxieties of many parents who may blame themselves for their child’s problems. It may allow access to specific supports including parent groups and education regarding what the future may hold (i.e. usual course, associated problems, prognosis). For inherited conditions, the issue of further genetic counselling/testing of family members needs to be addressed. Provision of clear information allows individuals to make informed decisions about being tested and to weigh the risks of having other affected children. The effect on other family members Although it was previously thought that having a child with LD impacted adversely on other unaffected siblings (often leading to the removal of the child from the family), there is little evidence that this is the case and worries about long-term damage appear unfounded. In fact, brothers and sisters of individuals with LD appear to be drawn to the caring professions and many end up working as doctors, nurses, teachers, or providing support for children with special needs. Grandparents may be a useful supportive resource for parents, but may also need to come to terms with their own feelings of having a disabled grandchild. The ‘burden of care’ For carers, informal support may actually be more valuable than formal (professional) support. Frequent appointments or regular home visits may be more disruptive than helpful. Developmental delay brings with it P.723
associated problems (e.g. longer time until the child can walk, achieve continence, acquire language/communication skills, establish a normal sleep pattern). The social, financial, and psychological impact on carers should be acknowledged and appropriate help and support provided. For infants and children, schooling may be both a benefit (in terms of learning social skills, support/respite for parents, and close contact with teachers/other parents) and a burden (particularly if necessary specialist schooling is not locally available). Transitional periods (e.g. adolescence/ early adulthood) are accompanied by parental anxieties as well as changes in how needs are met (see Critical periods of changing needs, pp. 720, 721). Advance planning will go some way to alleviate increased carer stress. Carers may also be concerned about what will happen to their child when they are no longer able to care for them and the open discussion of these issues, with provisional planning, may help avert crises (see also Ageing carers, p. 720). Needs and priorities

  • Early, accurate diagnosis.
  • Informative genetic advice to parents and other family members.
  • Access to high-quality primary (and secondary) health care.
  • Advice and access to appropriate help and support (practical help, financial assistance, social and educational needs).
  • Help and advice with any communication problems (communication aids, learning of sign language).
  • Consideration of the needs of carers (education, support groups, respite care).
  • Provision of specialist and domiciliary help with specific behavioural problems.
  • ‘Safety net’ of open access to increased support when necessary.
  • Acknowledgement that needs will change over time (and planning for this—see pp. 720, 721).

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