PROFILES OF NEUROMUSCULAR DISEASES HEREDITARY MOTOR AND SENSORY NEUROPATHY, TYPE-I AND TYPE-II

Data were collected prospectively for an impairment and disability pro file for 86 hereditary motor and sensory neuropathy, types I and II (H MSN) subjects over a 10-yr period. Our data confirm that HMSN is a slo wly progressive disorder that has a very heterogeneous phenotypical ex pression. The disorder was characterized primarily by diffuse muscle w eakness with prominent distal atrophy. The mean manual muscle test (MM T) strength grade for all muscle groups combined was 3.9 +/- 0.7 MMT u nits. There was a slowly progressive decline in strength, only -0.15 M MT units per decade. Distal muscle groups were weaker than proximal mu scles, and the decline in strength of the ankle muscles was greater th an for the proximal muscles. There was no side dominance. Anthropometr ic data revealed that distal atrophy may be masked by subcutaneous fat in female subjects. On average, HMSN subjects produced 20-40% less fo rce than normal controls, using quantitative isometric and isokinetic strength measures, even when MMT scores were normal. Pulmonary and car diac abnormalities were uncommon, as were spine deformity and joint co ntractures. Only 1 individual had severe restrictive lung disease, and 12 (14%) had a history of significant respiratory complications with no age or disease duration effect. As with the other neuromuscular dis eases, maximum expiratory pressure was more affected than forced vital capacity. Fourteen individuals (30%) had abnormal electrocardiograms, and six (7%) had a history of significant cardiovascular complication s with no age or disease duration effect. Kyphosis was the major spine deformity. Cardiopulmonary responses to exercise testing were markedl y abnormal, showing reduced aerobic capacity. Functional evaluations a nd timed motor performance tests showed only mild disability in most i ndividuals. With timed motor performance testing muscle weakness trans lated to impaired motor performance skills. Overall, mean scores on in tellectual function and neuropsychologic profiles were normal.