Variability in the median and ulnar nerve latencies: implications for diagnosing entrapment

Electrodiagnostic studies were performed on 1472 patients referred with upper-extremity symptoms. Age and anthropometric measurements were the major determinants of median and ulnar nerve latency variability at the wrist. An increased wrist ratio, an increased body mass index, and aging were associated with prolongation of median latencies. Aging and increased height were associated with prolongation of ulnar latencies, whereas an increased body mass index was negatively correlated to ulnar latencies. These associations held whether or not symptoms were considered related to work. To interpret electrodiagnostic studies of the median and ulnar nerves, age and anthropometric measures must be considered. Otherwise, epidemiologic studies will be confounded, and entrapment neuropathies such as carpal tunnel syndrome will be overdiagnosed.