Second lumbrical-interossei latency difference: A strong predictor of median neuropathy at the wrist in uremic patients.

Abstract

PURPOSE: Hand symptoms in uremic patients on dialysis can occur due to peripheral neuropathy, median neuropathy at wrist (carpal tunnel syndrome) or a combination. Routine electrophysiological parameters for diagnosing carpal tunnel syndrome do not differentiate median neuropathy at wrist in cases with concomitant peripheral neuropathy. Measuring 2L-INT latency difference has been described as the most sensitive test in establishing median neuropathy at wrist in cases with severe carpal tunnel syndrome and concomitant peripheral neuropathy. This study tested the significance of 2L-INT latency difference as a predictor of median neuropathy at wrist in uremic patients on dialysis. METHODS: 80 consecutive cases (158 hands) of end-stage renal failure on either hemodialysis or peritoneal dialysis were subjected to routine electrophysiological studies for carpal tunnel syndrome. 2L-INT latency difference was measured in all cases. RESULTS: 132/158 hands (83.5%) had abnormal electrophysiological studies. Routine tests were consistent with neurophysiological carpal tunnel syndrome in 66 (41.8%) hands and 63 of these 66 (95.5%) had prolonged 2L-INT latency difference. Peripheral neuropathy was found in 66 (41.8%) hands but 59 out of these 66 (89.4%) had prolonged 2L-INT latency difference suggesting a concomitant median neuropathy at wrist. Routinely performed tests would have missed median neuropathy at wrist with concomitant peripheral neuropathy in 59 (37.3%) hands. Overall, the incidence of median neuropathy at the wrist in our uremic patients on maintenance dialysis using standard nerve conduction parameters was 41.8%, however the incidences increased substantially to 79.1% if 2L-INT latency difference is included in the criteria for the diagnosis. CONCLUSIONS: Median neuropathy at wrist is common in patients with end-stage renal failure patients on dialysis. Diagnosis of median neuropathy at wrist is difficult in the presence of peripheral neuropathy when using the routine electrophysiological tests. Second Lumbrical-Interossei latency difference is a sensitive electrophysiological test to predict median neuropathy at wrist in presence of peripheral neuropathy.