Prevalence of Carpal Tunnel Syndrome in Motorcyclists

To the Editor: I enjoyed reading the article " Prevalence of Carpal Tunnel Syndrome in Motorcyclists " by Manes. 1 This article provides insight into a possible new association of symptoms with or the diagnosis for carpal tunnel syndrome due to motorcycle riding. The article makes recommendations for possible risk reduction (ie, prevention), which should be encouraged. However, problems with this case series should be emphasized. First, this study was a case series. Case series are considered low on the study design quality pyramid. 2 Therefore, case series can generate hypotheses or theories that require further evaluation using studies of higher methodologic quality. Second, this study is subject to selection bias. Selection bias means that those with carpal tunnel syndrome may have volunteered to be tested, whereas those without carpal tunnel syndrome did not volunteer. Only 50 of 100 patients surveyed were tested. Adding another 50 to the statistics (denominator) could drop the prevalence rate from 42% to 24%. It is unclear whether the 8% of patients with bilateral carpal tunnel syndrome were included in those with either left-or right-side disease. Granted, this is higher than the general population prevalence rate of 5% quoted in the article. 1 The cohort was unusual. Finding a group of 100 adults with an average age of 48 years and excluding only 2 because of the presence of " diabetes mellitus, kidney disease, obesity, arthritis , alcoholism, hypothyroid, rheumatoid arthritis, and fracture " 1 would be difficult. This severely limits the generalizability of the results of this study to the general population. Third, the Materials and Methods section provided no information on the specific inclusion criteria (ie, what was required to make the diagnosis of carpal tunnel syndrome). The article says " based on physical examination, history, and EMG [electro-myography] results " citing the Robinson 3 study, which probably means the definition of an " abnormal " nerve conduction test was to add together 3 nerve comparison differences. Unfortunately, this method probably has many more false positives than originally suggested. It would be possible to be classified as having nerve conduction documented carpal tunnel syndrome with median nerve latencies that are on the 50th percentile for the population as long as the ulnar and radial nerve latencies are somewhat faster than average. This would be like saying that if the left eye has 20/20 vision but the right eye has 20/10 vision, then the …