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

A prospective study of upper limb nerve conduction velocity was performed in 39 subjects (9 males, 30 females, mean age 46.8 years) with idiopathic Raynaud'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 idiopathic 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 carpal tunnel syndrome (CTS). Three patients with secondary RP (17%) had reduction of SCV of the distal median nerve, associated with increased DML of the 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 significantly lower and mean DMLs were significantly higher in both groups with respect to a control group. Mean distal conduction of the ulnar nerve was significantly slower only in the group with secondary RP. No slowing was observed in the proximal part of any nerve. It seems likely that patients with idiopathic RP have slowing of conduction in the distal part of the median nerve, along the carpal tunnel. Since slowing does not occur in all parts of the nerves of the hand, it cannot be related to acral vasomotor disturbances, but 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 the hand could be useful in cases of suspected secondary origin of RP. In idiopathic RP, slowing of conduction may only affect the median nerve, whereas in secondary RP it may affect other nerves of the hand.