A COMPARISON OF TRADITIONAL ELECTRODIAGNOSTIC STUDIES, ELECTRONEUROMETRY, AND VIBROMETRY IN THE DIAGNOSIS OF CARPAL TUNNEL-SYNDROME

In 49 patients (98 hands), referred to an electrodiagnostic laboratory , assessments were made by conventional nerve conduction studies on th e upper extremity and by two more portable modalities, namely electron eurometry (skin surface electrical stimulation of the motor nerve) and single-frequency (120 Hz) vibrometry. Tests were performed on median and ulnar nerves. Correlations with motor nerve conduction studies for each screening test on the median nerve were r=.81 For the electroneu rometer and r=.48 for the vibrometer. When carpal tunnel syndrome was diagnosed either by clinical criteria only or by nerve conduction abno rmality, the association with electroneurometry was characterized by h igh sensitivity and low specificity, while the opposite relationship p revailed with vibrometry. These associations were highly dependent on the methods used to select normal values from a reference population. While the manufacturer's recommended normal values offered good predic tability, with thresholds that corresponded to nerve conduction studie s, normal values generated in a more standard way produced much weaker and less useful associations. The selection of an appropriate electri cal screening test for peripheral nerve injury, such as entrapment neu ropathy, depends on the prevalence and seriousness of the target disea se and the relative consequences of over- and underdiagnosis.