Symptoms, signs and nerve conduction velocities in patients with suspected carpal tunnel syndrome

Abstract

Background: To inform the clinical management of patients with suspected carpal tunnel syndrome (CTS) and case definition for CTS in epidemiological research, we explored the relation of symptoms and signs to sensory nerve conduction (SNC) measurements.

Methods: Patients aged 20-64 years who were referred to a neurophysiology service for investigation of suspected CTS, completed a symptom questionnaire (including hand diagrams) and physical examination (including Tinel's and Phalen's tests). Differences in SNC velocity between the little and index finger were compared according to the anatomical distribution of symptoms in the hand and findings on physical examination.

Results: Analysis was based on 1806 hands in 908 patients (response rate 73%). In hands with numbness or tingling but negative on both Tinel's and Phalen's tests, the mean difference in SNC velocities was no higher than in hands with no numbness or tingling. The largest differences in SNC velocities occurred in hands with extensive numbness or tingling in the median nerve sensory distribution and both Tinel's and Phalen's tests positive (mean 13.8, 95% confidence interval (CI) 12.6-15.0 m/s). Hand pain and thumb weakness were unrelated to SNC velocity.

Conclusions: Our findings suggest that in the absence of other objective evidence of median nerve dysfunction, there is little value in referring patients of working age with suspected CTS for nerve conduction studies if they are negative on both Tinel's and Phalen's tests. Alternative case definitions for CTS in epidemiological research are proposed according to the extent of diagnostic information available and the relative importance of sensitivity and specificity.

Figure 1

Classification of anatomical regions of hand.

Figure 2

Recruitment of patients and numbers of hands analysed.

Figure 3

Distributions of differences in sensory nerve conduction velocity between the little and index fingers in a random 50% sample (N=193) of hands a) with no numbness/tingling and negative for Tinel’s and Phalen’s tests ("negative" hands) or b) positive for all three of these clinical features ("positive" hands). The vertical red line indicates the proposed cut-point for abnormality of sensory nerve conduction.