Provocative motor nerve conduction testing in presumptive carpal tunnel syndrome unconfirmed by traditional electrodiagnostic testing

How to measure outcomes of peripheral nerve surgery

Evaluation of outcomes after peripheral nerve surgeries include several assessment methods that reflect different aspects of recovery, including reinnervation, tactile gnosis, integrated sensory and motor function, pain and discomfort, and neurophysiologic and patient-reported outcomes. This review lists measurements addressing these aspects as well as the advantages and disadvantages of each tool. Because of complexities of neurophysiology, assessment remains a difficult process, which requires researchers to focus on measurements best relevant to specific conditions and research questions.

Neurophysiology not required before surgery for typical carpal tunnel syndrome

Sixty-eight patients with typical carpal tunnel syndrome underwent neurophysiological investigations preoperatively, but these were not assessed until the end of the study. Open carpal tunnel release was performed and the clinical diagnosis of carpal tunnel syndrome was considered as confirmed when there was a prompt resolution of the preoperative symptoms. Sixty-three of the 68 patients responded well to surgery, three had equivocal outcomes and two did not improve, and thus were considered not to have carpal tunnel syndrome. The neurophysiological tests were normal in these two patients, but were also normal in 14 of the 63 patients who improved with carpal tunnel surgery. Preoperative neurophysiology might therefore have led to up to 14 of the 63 cases of carpal tunnel syndrome being turned down for surgery. We conclude that neurophysiological studies contribute little to the diagnosis in typical cases of carpal tunnel syndrome, and are more often confounding than of assistance.

Differential latency testing: a more sensitive test for radial tunnel syndrome

A modification of the standard electrodiagnostic test was developed in an effort to provide a more sensitive electrodiagnostic evaluation in radial tunnel syndrome. Radial motor nerve latency recordings were obtained in 3 different forearm positions: neutral, passive supination, and passive pronation. The maximal difference in these recordings, the differential latency, in 25 patients with radial tunnel syndrome of greater than 6 months duration (test group) was compared with those in 25 asymptomatic volunteers (control group). Differential latency recordings were obtained in all patients in the test group before and after surgery. Radial nerves that were compressed demonstrated a significantly greater differential latency (0.44+/-0.12 ms) versus controls (0.12+/-0.008 ms). Following radial nerve decompression, differential motor latencies in the test group decreased below control values, demonstrating a resolution of the provoked electrical response with a postoperative differential latency of 0.07+/-0.05 ms. Our results demonstrate the differential motor latency of the radial nerve to be a sensitive electrodiagnostic tool in patients with radial tunnel syndrome. A differential latency of > or =0.30 ms was considered indicative of radial tunnel syndrome.