Etiologic factors in isolated paralysis of the serratus anterior muscle: A report of 197 cases.

One hundred ninety-seven cases of isolated paralysis of the serratus anterior muscle were analyzed to discover common etiologic factors and the mechanisms of injury producing this disorder. Exertion preceded 69 (35%) of the cases, and trauma caused 51 (26%) of the cases. Twenty-two (11%) occurred after locally invasive procedures, 13 (7%) after infection, and 10 (5%) after anesthesia. Sleeping position or exposure to cold proved to be causes in a few cases. Twenty-nine (15%) of the cases were of unknown cause. Evaluation of the mechanism of the injury indicated that in most cases the lesion was mechanical in origin. The data suggested that the long thoracic nerve is not unusually susceptible to infectious or toxic neuropathy, as has previously been supposed.