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Ovid: Fifty Neurologic Cases from Mayo Clinic

Editors: Noseworthy, John H. Title: Fifty Neurologic Cases from Mayo Clinic, 1st Edition Copyright ©2004 Oxford Unversity Press (Copyright 2004 by Mayo Foundation for Medical Education and Research) > Table of Contents > Case 1: Forgets names but has a new appreciation for polka music Case 1: Forgets names but has a new appreciation for polka music CASE 1 History At age 52 years, a left-handed man began experiencing difficulties stating the names of familiar people and objects. Initially, he had no apparent problems with memory or other cognitive functions or changes in behavior. By age 54, difficulties with verbal comprehension had developed, but he still worked as a farmer and had no problem working or driving. At age 55, he developed a profound interest in listening to polka music, sometimes doing so for 12 hours or more at a time. By age 57, he was not able to read or write or to recognize most familiar faces and objects. His father and paternal aunt had become forgetful late in life. His son has congenital apraxia of speech that has improved markedly with speech therapy. Examination Neurologic examination at age 53 revealed an alert, cooperative man whose language was fluent. He had difficulty naming simple objects and famous faces. Reading, writing, memory, and constructional praxis were all preserved. Over the next 4 years, his aphasia worsened, as did recognition of words, objects, and faces (associative agnosia). His verbal memory and attention also declined; yet, on examination at age 57, his recall of where objects were hidden in the office and his ability to draw figures remained intact. Investigations The cerebrospinal fluid examination was normal. Serial magnetic resonance imaging demonstrated progressive left, and then right, anterior temporal lobe atrophy (Figure). Initial neuropsychologic testing at age 53 demonstrated problems with divided attention, mental manipulation, executive functioning, and verbal learning and recall; his performance on language function tests (e.g., Boston Naming Test [BNT] score of 16/60) was particularly poor. Subsequent testing sessions showed progression in all cognitive domains, particularly language (BNT, 3/60 at age 56); yet, his copy of the Rey-Osterreith Complex Figure was almost perfect. P.2

FIGURE. Representative T1-weighted coronal magnetic resonance images of patient from age 53 to 57 years. Note the progressive atrophy of the left amygdala and temporal cortex beginning at age 53. Atrophy in the right amygdala and temporal cortex was subtle at age 54, but it was clearly progressive over the years. (From Boeve BF, Geda YE. Neurology 2001;57:1485. By permission of the American Academy of Neurology.)

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DIAGNOSIS CASE 1 Asymmetric cortical degeneration syndrome: semantic dementia
Commentary by Dr. Bradley F. Boeve The terms “semantic dementia,” “semantic aphasia and associative agnosia,” “primary progressive aphasia,” “chronic progressive aphasia,” “temporal variant of frontotemporal dementia,” and “focal or asymmetric cortical degeneration syndrome” have all been applied to patients who exhibit a degenerative neurobehavioral disorder with progressive impairment predominantly or exclusively in the domain of language. When impairment is isolated to language, the term “primary progressive aphasia” is appropriate; when impairment is present in object naming (i.e., anomia) and word meaning (i.e., agnosia), with other aspects of language and cognition relatively intact, the term “semantic dementia” is apt. The initial symptom is typically “forgetfulness for names,” and although paraphasic errors, dyslexia, dysgraphia, visual agnosia, and executive dysfunction usually evolve with time, many patients perform daily activities remarkably well over the initial 2 to 5 years of symptoms. Progression can vary, with symptoms reflecting the topography of progressive cortical dysfunction. Typically, degeneration spreads posteriorly in the ipsilateral temporal lobe, with involvement eventually extending to the perisylvian, frontosubcortical, and sometimes superior parietal regions in the dominant hemisphere. When the contralateral hemisphere is affected, a remarkably consistent finding is progressive atrophy in the opposite anterior temporal lobe. If and when sufficient nondominant hemisphere frontotemporal cerebral dysfunction ensues, problematic neuropsychiatric features can evolve, such as socially inappropriate, disinhibited, and even criminal behavior. Misidentification errors, prosopagnosia, and ultimately multimodal associative agnosia become apparent as the nondominant temporal lobe atrophies. Semantic dementia is one of the focal or asymmetric cortical degeneration syndromes and is associated with anterior temporal lobe dysfunction. Other clinical syndromes include progressive nonfluent aphasia associated with dominant hemisphere frontal opercular or insular dysfunction; frontotemporal dementia associated with dorsolateral prefrontal, orbitofrontal, or anterior cingulate dysfunction (or a combination of these); corticobasal syndrome associated with parietofrontal cortical dysfunction; and posterior cortical atrophy associated with parieto-occipital cortical dysfunction. Although the nomenclature P.4
for these syndromes and the disorders that underlie them can be confusing, the conceptual perspective is the same—symptomatology is dictated more by the topography of dysfunction than by the underlying histopathologic disorder. The pathologic substrates for semantic dementia have tended to be associated with either nonspecific neurodegenerative changes (e.g., “dementia lacking distinctive histopathology” or “frontotemporal lobar degeneration” with or without ubiquitin-positive inclusions) or a disorder within the tauopathy spectrum (e.g., Pick’s disease, corticobasal degeneration, or argyrophilic brain disease). Alzheimer’s disease rarely presents in this manner. Mutations in the tau gene have been identified in some patients who present with semantic dementia. No therapy has been identified that alters the pathophysiologic mechanism of the disorders that manifest as semantic dementia, nor have pharmacologic manipulations led to a marked and sustained symptomatic benefit in any patient. Speech therapy is reasonable for patients early in the course of the disease. A striking and poorly understood observation is the remarkable evolution of artistic talent in rare persons with frontotemporal dementia, of whom some have had semantic dementia. Some patients have produced paintings more elaborate than their past renderings, whereas others have developed interests in listening to or playing forms of music that previously had not been considered interesting. This phenomenon seems completely contrary to degenerative brain disease. Whether compensatory mechanisms in relatively unaffected neuronal networks or disinhibition of affected neuronal networks (or both) explains this phenomenon is not known. Further study in semantic dementia and other focal or asymmetric cortical degeneration syndromes may not only improve our understanding of degenerative brain disease but also provide insight into the neurologic underpinnings of artistic appreciation and expression. REFERENCE Neary D, Snowden J, Gustafson L, et al. Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria. Neurology 1998;51:1546-54.

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