Electromyographic mixed nerve and cutaneous silent period in evaluating the A-delta fibres in a patient with hereditary sensory-autonomic neuropathy.

The aim of this study was to evaluate A-delta fibre function in a patient with hereditary sensory-autonomic neuropathy (HSAN). We used the mixed and cutaneous silent period techniques in addition to a conventional electromyographic investigation in a patient with type 2 HSAN, a rare disease characterised by wide-spread sensory and variable autonomic dysfunction caused by incomplete development of sensory and autonomic neurons. Whereas the stimulation of one digital nerve did not show any evidence of silent period in either the left or the right hand, the simultaneous stimulation of two digital nerves, as well as the stimulation of a mixed nerve, revealed a measurable delayed and shortened silent period. These data suggest that a spatial summation mediated by A-delta fibres was required for generation of the silent period in this patient and that combining the CSP and MNSP may be of practical use in evaluating impairment of the small myelinated fibres.