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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 5: “Old polio,” can’t run, and can’t swallow Case 5: “Old polio,” can’t run, and can’t swallow CASE 5 History A 67-year-old man was evaluated because he recently noticed mild dysphagia for solids, although he had never noted any facial weakness or trouble drinking through a straw. In 1952, when he was 18 years old, bilateral arm weakness, bilateral scapular winging, and atrophy of the left arm and leg developed after a flu-like illness. Poliomyelitis was diagnosed, but no tests were performed. Except for static atrophy of the left arm and leg, he lived an active life until age 57, when he noted reduced ability to run because of progressive left leg weakness. Gradually progressive, painless atrophy and weakness of affected muscle groups developed, involving primarily the left arm and leg. There was no family history of neuromuscular disease. Examination The cranial nerve examination was normal, and no facial weakness or atrophy was found. He had asymmetric, moderate weakness, especially of the proximal muscles of all four limbs, and mild weakness of neck flexors. Severe atrophy of the muscles of the left limbs was most apparent in proximal arm and distal leg muscles. No fasciculations were noted. There was bilateral scapular winging. Deep tendon reflexes were decreased, except for a mildly increased right gastrocnemius reflex. Sensory examination findings were normal. He walked with a left footdrop. Investigations Nerve conduction studies showed a low-amplitude right tibial compound muscle action potential. Needle examination demonstrated prominent short-duration, low-amplitude, polyphasic motor unit action potentials in all muscles without fibrillation potentials (Figure). Recruitment was rapid in weak muscles. The creatine kinase level was slightly increased at 387 U/L (normal, <336 U/L). A biopsy specimen from the right vastus lateralis muscle demonstrated changes typical of only denervation atrophy and not of a chronic neurogenic process such as poliomyelitis. P.18

FIGURE. A, Normal voluntary motor unit action potentials. B, Small, short, myopathic motor units as seen in this patient.

DIAGNOSIS CASE 5 Fascioscapulohumeral (FSH) muscular dystrophy
Commentary by Dr. Brian A. Crum Genetic studies revealed a deletion on chromosome 4q consistent with FSH muscular dystrophy. FSH muscular dystrophy is an autosomal dominant hereditary myopathy caused by deletion of a subtelomeric portion of chromosome band 4q35. The gene product has not been identified, although it is believed that this deletion leads to abnormal expression of another unknown gene or genes. Approximately 25% to 30% of cases are sporadic. The prevalence of the disorder is estimated at 1:20,000. Onset typically occurs by the teenage years, although onset has been reported in patients as old as 75 years. The severity and progression of FSH muscular dystrophy vary widely, but about 20% of patients eventually require wheelchair assistance. The disease may have prolonged periods of stabilization or even complete arrest. Life span is not significantly shortened. The classic phenotype is that of facial, proximal arm, pelvic, and distal leg weakness. It generally is accepted that FSH muscular dystrophy leads to “descending” weakness, although up to one-half of patients never experience pelvic girdle or leg weakness. Scapulohumeral onset is three times more common than facial onset; however, it may be that symptoms of arm and shoulder weakness first lead to medical evaluation, because at presentation most of the patients with these symptoms already have facial weakness. Other common features include scapular winging, asymmetry, and even congenital absence of individual muscles. The deltoid muscles may be spared. Other features commonly noted include anterior axillary folds and horizontal clavicles. Beevor’s sign (the umbilicus moves rostrally on contraction of abdominal muscles with flexion of the neck) may be seen with selective involvement of the lower abdominal muscles. With the advent of genetic testing, atypical presentations of FSH muscular dystrophy have been reported, including facial-sparing myopathy, distal myopathy, asymmetric arm weakness, calf weakness, and proximal weakness simulating limb-girdle muscular dystrophy. Thus, a detailed examination to assess for mild, especially asymmetric, limb weakness, facial weakness, and scapular winging is essential. Laboratory findings usually include increased levels of creatine kinase; however, after age 55, these levels may decrease or be normal. Electromyographic evaluation shows short-duration, low-amplitude P.20
motor units with rapid recruitment. The severity of the findings may vary between muscles and even between different sites in the same muscle. As in chronic myopathies, larger motor units may be seen. Fibrillation potentials may be sparse or prominent. Muscle biopsy specimens demonstrate myopathic changes, with central nuclei, fiber necrosis, variation in fiber diameter, and an increase in perimysial and endomysial connective tissue. Inflammatory infiltrates may be present in the perivascular areas of the endomysium and perimysium. The occurrence of these infiltrates may be genetically determined because they are either present or absent in a given family. Other systemic manifestations are rare. Deafness is uncommon, although subclinical hearing loss detected by audiometry is not. Coat’s disease is a retinal vascular disorder that, although uncommon, may be present, typically in association with severe childhood FSH muscular dystrophy. Exudative leakage from damaged endothelial cells in small retinal blood vessels can threaten vision. Cardiac conduction defects are exceedingly rare. Mental retardation has been associated with FSH muscular dystrophy, but a definite relationship has not been established. No effective treatment is available for FSH muscular dystrophy. Inflammatory changes may be seen in muscle biopsy specimens; however, the results of a clinical trial of prednisone therapy in FSH muscular dystrophy were negative. A clinical trial of albuterol found an increase in grip strength and lean body mass in the treatment group but no significant improvement in overall muscle strength. Other treatment measures such as scapular fixation and ankle-foot orthoses have a role in symptomatic treatment. REFERENCE Felice KJ, Moore SA. Unusual clinical presentations in patients harboring the fascioscapulohumeral dystrophy 4q35 deletion. Muscle Nerve 2001;24:352-6.

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