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News — There is great debate in the medical community regarding whether carpal tunnel syndrome (CTS) is based on a person's bone structure, what a person's does at work, or some other underlying reasons. Over a 15-year period, a Brazilian researcher found that dairy farmers that manually milked their cows were at an increased risk for developing carpal tunnel syndrome. The research also revealed specific features associated with CTS in this unique occupational group that differed from patients that presented with CTS from an unknown cause. For Brazil, a country with the largest production of milk in Latin America, manual milking presents an occupational concern for small herd farmers that reside in the rural areas. The study however, also reveals, at least in this population, the repetitive motions involved in the milking may be the reason for the CTS.

While studying 3125 patients that had been referred for electrodiagnosis of carpal tunnel syndrome (CTS), 43 cases were found to be associated with manual milking and carried similar characteristics and symptoms. The patients, 88.4% of them male with an average age of 44.9 years old, presented with common complaints of bilateral hand numbness while milking. The mean time in the milking profession was just over 20 years and they spent an average of 146 minutes manually milking daily. Some of the farmers initially believed that their symptoms were natural or normal, but in fact their symptoms were caused by the repetitive and interchangeable right and left hand fingers flexion and extension involved in manually milking their cows.

Unlike the patients that presented with CTS from no known cause, the symptoms and diagnostic findings were found on both hands and were the same in both hands. Nerve conduction studies also differed from the electrodiagnosis of other CTS patients because the motor function of the hand revealed to be more affected than the sensory function, which resulted from the repetitive effort on finger flexion in manual milking. According to researcher, Dr. J.A. Kouyoumdjian of Sao Jose do Rio Preto, Brazil, "There is a lot of discussion about carpal tunnel syndrome and occupation. In this research, we found a natural model of CTS and these cases seem to be originally caused by occupation." This study will not end the debate but adds another piece in the CTS puzzle.

The results of this research will be reported at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) 52nd Annual Scientific Meeting in Monterey, California, September 21-25. The AANEM is the largest organization worldwide, with nearly 5000 members, dedicated to advancing neuromuscular, musculoskeletal, and electrodiagnostic medicine.