Nerve conduction velocity study of the upper limb in Raynaud's phenomenon

A prospective study of upper limb nerve conduction velocity was performed i n 39 subjects (9 males. 30 females, mean age 46.8 years) with idiopathic Ra ynaud's phenomenon (RP and 18 patients (3 males, 15 females, mean age 49.9 years) with RP secondary to systemic sclerosis (SS). Five subjects with idi opathic RP (13%) showed slowing of sensory conduction velocity (SCV) of the distal median nerve, associated with delayed distal motor latency (DML) of the same nerve in three patients, without clinical signs or symptoms of ca rpal tunnel syndrome (CTS). Three patients with secondary RP (17%) had redu ction of SCV of the distal median nerve, associated with increased DML of t he same nerve in one and with clinically silent slowing of SCV of the ulnar nerve in two (11%). Mean distal SCVs of the median nerve were significantl y lower and mean DMLs were significantly higher in both groups with respect to a control group. Mean distal conduction of the ulnar nerve was signific antly slower only in the group with secondary RP. No slowing was observed i n the proximal part of any nerve. It seems likely that patients with idiopa thic RP have slowing of conduction in the distal part of the median nerve, along the carpal tunnel. Since slowing does not occur in all Darts of the n erves of the hand, it cannot be related to acral vasomotor disturbances, bu t to local or systemic factors. In contrast, patients with secondary RP had slowing of median and ulnar nerve conduction velocity, presumably related to subclinical distal peripheral neuropathy. A nerve conduction study of th e hand could be useful in cases of suspected secondary origin of RP. In idi opathic RP, slowing of conduction may only affect the median nerve, whereas in secondary RP it may affect other nerves of the hand.