Clinical and neurophysiological aspects of anatomical variants in dorsomedial hand innervation

Objective: Three patients presented with painful paraesthesias in the dorsomedial aspect of the hand after removal of a ganglion cyst of the dorsal lower third of the forearm. This hand territory is usually innervated by the dorsal cutaneous branch of the ulnar nerve (DCU) but here it was innervated by a branch of the radial superficial nerve (RS). Consequently, we aimed to examine the frequency of this variant in the general population. Methods: Both RS and DCU were stimulated in the forearm and sensory response recorded from the dorsomedial skin area of the hand in the three patients and 100 normal controls. Results: In all three patients, the RS nerve innervated the dorsomedial hand bilaterally. Nineteen out of 100 controls demonstrated variants of dorsomedial skin innervation of the hand on nerve conduction studies: 12 unilaterally and seven bilaterally. Among them, 13 individuals had mixed innervation by both RS and DCU and six by the RS nerve only. Conclusion: Nerve conduction studies of both RS and DCU with sensory response recording on the dorsomedial hand area should be considered before surgical procedures on the dorsal lower forearm in order to prevent iatrogenic postoperative sensory nerves lesions.