Relationships between Clinical Scales on Severity of Symptoms and Electrodiagnostic Measures on Abnormality of Nerve Conduction in Carpal Tunnel Syndrome

Abstract

This study examined the severity of carpal tunnel syndrome symptoms in relation to nerve conduction measures of the median nerve. The symptom scales include (1) numbness, (2) tingling, (3) nocturnal symptoms, (4) pain, (5) weakness, and (6) clumsiness; the nerve conduction measures are (1) peak amplitude and (2) peak latency of the sensory action potential, (3) conduction velocity of the sensory nerve fibers, (4) peak amplitude and (5) onset latency of the motor action potential. The symptom severity and nerve conduction impairment were evaluated for 34 affected hands of 24 patients (6 males and 18 females) by using a questionnaire developed by Levine et al. and an electromyographic instrument, respectively. Significant relationships identified among the clinical scales resulted in a dichotomous symptom classification scheme with a criterion of the relatedness to nerve damage: primary and secondary symptoms. Correlation analysis on the symptom and electrodiagnostic measures showed both the severity scales for the primary and all the symptoms had higher correlations with the extent of the nerve injury than that for the secondary symptoms. These results demonstrated a biological significance of the clinical scales, which can be used in evaluating the outcome of treatments and developing a model for exposure-severity relationship.