Ring finger sensorial conduction studies in grading carpal tunnel syndrome

Comparing the distal sensory latencies of median and ulnar nerve over wrist-to-ring finger (RF) segment is a sensitive conduction parameter in the diagnosis of carpal tunnel syndrome (CTS). However to the best of our knowledge, there is not any research questioning whether the RF studies are useful in grading the CTS or not.

To determine whether the hands with moderate degree CTS and elicitable median nerve sensory responses over second finger and unelicitable responses over RF represent a more severe electrophysiological grade than the hands with elicitable responses over both fingers.

In patients with clinical diagnosis with CTS, obtained values on sensory and motor nerve conduction studies of median and ulnar nerves were compared between median nerve-to-RF sensorial responders (group 1) and nonresponders (group 2).

Seventy-four recordings belong to 59 patients with moderate degree CTS were included. There were 55 hands in group 1, and 19 in group 2. Mean sensory onset latency of median nerve over second finger was longer (4.17 ± 0.53 msec versus 3.47 ± 0.46 msec; p< 0.001), sensory conduction velocity was slower (34.1 ± 5.5 m/sec versus 40.1 ± 5.3 m/sec; p< 0.001), SNAP amplitude was smaller (7.0 ± 3.3 μ V versus 13.7 ± 6.7 μ V; p< 0.001), and distal motor latency was longer (5.75 ± 0.96 msec versus 4.76 ± 0.42 msec; p< 0.001) in group 2 than in group 1.

Median nerve-to-RF sensorial nonresponders have a more progressed compressive neuropathy, and represent a more severe electrophysiological grade than the responders.