Can studies of the second lumbrical interossei and its premotor potential reduce the number of tests for carpal tunnel syndrome?

The second lumbrical interossei latency difference test (2-LINT) is a frequently used test for diagnosing carpal tunnel syndrome (CTS). Recently, the premotor potential (2-LUMP) observed with 2-LINT was identified as a median sensory potential. 2-LINT recording therefore not only compares conduction across equidistant median and ulnar motor segments, but also registers median sensory conduction. In 52 CTS and 50 control hands, we tested whether motor and sensory data obtained with 2-LINT help to reduce the number of tests necessary to diagnose CTS. The combined sensitivity of 2-LINT derived parameters (2-LUMP latency, median second lumbrical to ulnar interossei latency difference, ulnar digit 5 sensory to 2-LUMP velocity, and ulnar interossei to 2-LUMP latency difference) was 89%, identical to that of combined non-2-LINT derived parameters (median digit 3 sensory velocity, ulnar digit 5 to median digit 3 sensory velocity difference, median abductor pollices brevis [APB] latency, median APB to ulnar abductor digiti minimi latency). The 2-LINT technique with its premotor potential may therefore help to reduce the number of nerve conduction tests commonly needed to investigate patients with suspected CTS.