Electrophysiological study of chronic intractable shoulder pain

Electrophysiological criteria for carpal tunnel syndrome (CTS) may be defined by difference of the distal latencies between median and ulnar nerves in the same hand greater than 2 SD from the normal mean. Based on the data in 20 normal subjects (10 men and 10 women), the criteria for abnormality were distal sensory latency (DSL) over 0.9 msec and/or distal motor latency (DML) over 1.4 msec. Of 100 patients (24 men and 76 women) with chronic intractable shoulder pain (CISP) tested, 53 had electrophysiological CTS; 9 (17%) were men and 44 (83%) were women. Thirty-nine (74%) of these patients had bilateral CTS. Twenty of the 100 patients had nocturnal exacerbation (NE). Eighteen (90%) had CTS; one (6%) was a man and 17 (94%) were women. NE does not necessarily reflect the severity of CTS from statistical analysis. Electrophysiological evaluation is essential for middle-aged women with CISP, and nocturnal exacerbation may be pathognomonic for CTS in these patients.