A new median motor test: comparison with conventional motor studies in carpal tunnel syndrome

Comparison of the modified method and the median sensory-ulnar motor latency difference in the diagnosis of carpal tunnel syndrome

OBJECTIVES

This study aimed to compare the modified method and the median sensory-ulnar motor latency difference in the diagnosis of carpal tunnel syndrome.

METHODS

The study recruited the electromyography results of 105 hands of 60 patients who had a complaint of carpal tunnel syndrome (CTS) on the hand diagram. The average sensory-ulnar motor delay difference (MSUMLD) was determined by simple subtraction, and the modified method was calculated based on the results of the classic method. The modified method and the MSUMLD were compared according to their sensitivity and specificity in the diagnosis of CTS.

RESULTS

In this study, 54 hands were evaluated with a unilateral nerve conduction study (45 right; 9 left). A total of 23 hands with CTS and 31 hands without CTS were diagnosed electrophysiologically. The MSUMLD had 91.3% sensitivity and 93.5% specificity; however, the modified method showed 95.7% sensitivity and 96.8% specificity in the diagnosis of CTS. Moreover, the modified method had 100% sensitivity and specificity in the diagnosis of moderate CTS.

CONCLUSIONS

The modified method may have higher diagnostic accuracy than the MSUMLD for diagnosing CTS.

Second lumbrical and mixed nerve segmental conduction studies in carpal tunnel syndrome

OBJECTIVES

We report the findings of 20 patients with carpal tunnel syndrome (CTS) who had segmental motor studies to the second lumbrical (2L) and mixed nerve action potential (MNAP) across the carpal tunnel.

METHODS

This was a prospective study of 20 patients randomly selected who had clinical and electrophysiologic evidence of CTS using standard techniques. Six CTS patients had studies pre- and post-surgical release.

RESULTS

Mean 2L motor amplitude reduction across the carpal tunnel was 55.19% ± 6.6% in patients (controls = 15.9% ± 9.4%). Mean motor velocity across the carpal tunnel was 23.4 ± 7.05 m/s versus 46.45 ± 6 m/s in controls. Mean reduction of the MNAP amplitudes was 79.0% ± 23% versus 20% ± 15% in controls. The mean MNAP velocity was 12.3 ± 13.1 m/s versus 48.35 ± 5.18 m/s in controls. The 6 surgical cases showed improvement in amplitude reduction and velocity at 2-6 months consistent with preoperative severity.

CONCLUSIONS

These studies show that segmental conduction studies to the 2L and MNAP can demonstrate conduction block that improves with decompression.