Longitudinal study of neuropathic deficits and nerve conduction abnormalities in hereditary motor and sensory neuropathy type 1.

We measured neuropathic deficit (neurologic disability score [NDS]) and attributes of nerve conduction in hereditary motor and sensory neuropathy (HMSN 1) in cross-sectional evaluation of 69 patients and in longitudinal evaluation over approximately 15 years in 31 of them. Neuropathic deficit worsened by 0.6 NDS point per year in patients 5 to 14 years old at first evaluation, by 1.1 points in patients 15 to 39 years old, and by 0.9 point in patients 40 or more years old. Neuropathic deficit was greater in HMSN 1b (the disorder linked to Duffy) than in HMSN 1a (not linked to Duffy). Nerve conduction attributes changed significantly depending on attribute studied, age, and nerve. In patients evaluated serially, ulnar conduction velocity (CV) increased by a few meters per second in patients who were 5 to 14 or 15 to 39 years old at first examination, but decreased in patients who were older. In serial measurements, peroneal nerve amplitude decreased in all 3 age groups. We found an association between CV and amplitude or NDS at first and last examinations, suggesting an association between severity of the CV abnormality and neuropathic deficit. The severity of the CV abnormality in the young appears to predict later neurologic abnormality.