Neurographic assessment of lesions of single proper digital nerves

Objective: To investigate which strategy should be used to assess lesions of single proper digital nerves by means of nerve conduction studies. Methods: Comparison of the results of various orthodromic and antidromic tests with surface electrodes and needle electrodes for stimulation and recording in two patients with a lesion of a single proper digital nerve of the middle finger. Results: It is shown that orthodromic and antidromic nerve conduction tests over the wrist-finger segment yield misleading results because of innervation overlap, volume conduction and co-stimulation. These problems could be avoided by selective stimulation of common digital nerves distally in the palm of the hand and recording with ring electrodes around the relevant finger. Efficacy and selectivity of stimulation are verified by simultaneous recordings from the neighbouring fingers. Conclusion: Lesions of single volar proper digital nerves are by no means rare, but no nerve conduction studies have been published so far to assess such lesions adequately. A novel, simple and reliable technique for this purpose is described.