Documentation of brachial plexus compression (in the thoracic inlet) utilizing provocative neurosensory and muscular testing.

Abstract

Diagnosis and documentation of brachial plexus compression in the thoracic inlet, "thoracic outlet syndrome", remains difficult because the syndrome complex overlaps that of patients with cervical disc disease, intrinsic shoulder pathology, and peripheral nerve compression. While traditional electrodiagnostic testing can identify cervical radiculopathy and the rare isolated lower trunk compression, it cannot identify brachial plexus compression in the thoracic inlet. In 2000, neurosensory testing with the Pressure-Specified Sensory Device (PSSD) was applied to this diagnostic dilemma, demonstrating a significant increase in the one-point static touch cutaneous pressure threshold between controls and patients, when the index finger (upper trunk) and little finger (lower trunk) were tested with the hands at rest and after provoking the plexus by elevating the hands above the head. In the present study, this approach has been extended to include two-point static touch thresholds with the PSSD, and pinch and grip strength (Digit-Grip). Sixteen controls (mean: 34.2, range: 11 to 48 years) were tested and the 99 percent upper confidence limit calculated for percent change after elevation of the hands for 3 min. Forty-one patients symptomatic for brachial plexus compression (mean: 41.0, range: 21 to 62 years) were tested. The clinical severity of the plexus compression was dichotomized as either "severe" or "not severe" judged by the Roos and Tinel sign. Results demonstrated that when five or more of the eight possible neurosensory and motor test results were > 99 percent normal confidence limit for change, this testing has a sensitivity of 82 percent, a specificity of 100 percent, and a positive predictive value of 100 percent for the diagnosis of clinically severe brachial plexus compression. Seventeen patients who were in the "severe" category prior to surgery, were tested before and after plexus neurolysis and anterior scalenectomy. All 17 patients were clinically improved and in 16 of these patients, postoperative neurosensory and motor testing returned to a normal pattern (no significant increase in thresholds with hand elevation). It is concluded that neurosensory (PSSD) and motor testing (Digit-Grip) can help in the diagnosis and documentation of brachial plexus compression.