Electrophysiological Epidemiology of Carpal Tunnel Syndrome FESSH June 13, 2018 Electrophysiological Epidemiology of Carpal Tunnel Syndrome Tatsuki Ebata, Ikuo Nakai, Akira Kogure,Ken-ichiro Goto Sakura Orthopaedic Hospital Chiba, Japan

T. Ebata Objective Carpal tunnel syndrome (CTS) is the most common upper extremity entrapment neuropathy. Nerve conduction studies are used for the diagnosis of CTS. As the severity of CTS progresses, the nerve conduction velocity in the carpal tunnel reduces. The compound muscle action potential of the abductor pollicis brevis (APB-CMAP) demonstrates progressively increased latency and decreased amplitude. In the most advanced stages of CTS, APB-CMAP finally becomes undetectable and the motor conduction velocity cannot be measured (terminal CTS). The purpose of the present study was to investigate the epidemiology (risk factors) of CTS in relation to APB-CMAP.

Materials and Methods (Between 2012 and 2017) T. Ebata Materials and Methods (Between 2012 and 2017) 786 hands (572 patients ) whose latencies of APB-CMAP ≥4.5 Mean age : 60.7 years Men : 136 (23.8%) Women : 436 (76.2%) Right-handed: 542 (94.8%) Left-handed : 30 (5.2%) The hands with undetectable APB-CMAP was defined as terminal CTS. The binomial test, McNemar test, Wilcoxon test, and logistic regression analysis were employed for statistical analysis. A P-value of <0.05 was considered statistically significant.

Dominant to non-dominant ratio T. Ebata Results Total: 786 hands Men to women ratio (P<0.01) Dominant to non-dominant ratio (P<0.01) Men 191hands (24.3%) Dominant 446hands (56.8%) Non-dominant 340hands (43.2%) Women 595 hands (75.7%)

Results Terminal CTS rate Average latency of APB-CMAP T. Ebata Results Terminal CTS rate (290 patients with bilateral CTS) Average latency of APB-CMAP (162 patients with bilateral non-terminal CTS) P<0.01 P<0.01 Hands ms 7.00 83 (28.6%) 6.29 52 (18.0%) Dominant Non-dominant Dominant Non-dominant

Results Number of hands T. Ebata Results Number of hands Aged 60–69 years was the highest and aged 50–59 years was the second highest Terminal CTS rate Aged 70–79 years had the highest rates and aged 80 years and older had the second highest rates. Hands % 222 227 29.7 26.9 27.6 22.9 101 113 71 10.9 52 5.9

Conclusions There are some possible risk factors of idiopathic CTS. T. Ebata Conclusions There are some possible risk factors of idiopathic CTS. Women were three times more likely to develop CTS than men. This may be because women have relatively smaller hands than men, or perhaps estrogen plays a part in the development of CTS. Dominant hands tended to develop CTS and were more susceptible to progression than non-dominant hands. The cause of CTS may be related to overuse of the hand, as repetitive motion at work. The age distribution curve of CTS peaked in the fifties and sixties when the most serious CTS occurred. Therefore, age is also an important factor of CTS. A combination of these risk factors appears to contribute to the development of CTS.

T. Ebata Thank you!