Comparison of the diagnostic value of ultrasonography and neurography in carpal tunnel syndrome.

Objective: The aim of the study was to compare the sensitivity and specificity of ultrasonography and neurography in patients with carpal tunnel syndrome (CTS) and to estimate the critical value of cross-sectional area of median nerves.

Methods: Eighty-nine patients (153 carpal tunnels) (17 men and 72 women, mean age 62.5 years) with CTS and 50 healthy volunteers were examined. In all patients and controls standard neurographic tests were done (motor and sensory conduction velocity tests in median and ulnar nerves). Ultrasonography was done in transverse projections with estimation of cross-sectional circumference and area of median nerves.

Results: Mean parameters of ultrasonography and neurography, except the mean latency of sensory potentials, were statistically different in the patient and control groups. Correlations between mean parameters of ultrasonography and neurography were also statistically significant. The critical value of median nerves' cross-sectional area equal to 0.1 cm2 seemed to be important in CTS diagnostics. Oedema of median nerve was observed in some CTS cases without electrophysiological changes. Radial slide of median nerve round the tendon of superficial flexor muscles of second and third fingers was observed in 68% of CTS patients.

Conclusions: Ultrasonographic findings correlate well with electrophysiological tests in CTS patients. Cross-sectional area equal to 0.1 cm2 is important in CTS diagnostics. Median nerve oedema, revealed in the early stage of CTS without any electrophysiological changes, might be an important factor in occurrence of subjective complaints. Radial slide of median nerve phenomenon is a common ultrasonographic finding in CTS.