Effect of coexistent carpal tunnel abnormality on sensory conduction findings in polyneuropathy

Objectives: To investigate the change of pattern of sensory conduction findings in polyneuropathy with coexistent carpal tunnel abnormality (CTAbN). Methods: We reviewed sensory conduction findings of 46 patients with acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and 66 with diabetic polyneuropathy (DP). Both groups were categorized into those with and without CTAbN according to transcarpal median sensory conduction velocities. Results: In AIDP, median sensory nerve action potential (SNAP) amplitudes were reduced, whereas sural SNAP amplitudes remained unchanged. Median SNAP amplitude was lowest, and sural/median SNAP amplitude ratio was highest in AIDP with coexistent CTAbN. In DP, both median and sural SNAP amplitudes were reduced. Their sural/median SNAP amplitude ratios remained unchanged. Incidence of abnormal median-normal sural pattern was higher in AIDP than in DP. Nevertheless, these incidences did not alter with coexistent CTAbN. The ulnar SNAP amplitude and sural/ulnar SNAP amplitude ratio were not significantly different between those with and without CTAbN in both AIDP and DP groups. Conclusions: Coexistent CTAbN caused further increase of sural/ median SNAP amplitude ratio only in AIDP.