Documentation of brachial plexus compression in the thoracic inlet with quantitative sensory testing.

This study evaluated the cutaneous pressure threshold of subjects with and without a clinical diagnosis of brachial plexus compression in the thoracic inlet, usually termed thoracic outlet syndrome (TOS). Sixty-one subjects (102 arms) made up the control population; 11 subjects 120 arms) made up the TOS population. Assessment by two upper-extremity specialists preceded the testing. The one-point cutaneous pressure threshold was measured with the Pressure-Specifying Sensory Device (PSSD) on the pulp of both the index and little finger (upper and lower brachial plexus distributions) with the arm in the unprovoked (adducted) and provoked (abducted 180 degrees) positions. In the control subjects, there was no significant change in the cutaneous pressure threshold between unprovoked and provoked positions. In contrast in patients with TOS, there was a significant increase in the cutaneous pressure threshold at both sites (p < .0001 ) between the unprovoked and the provoked positions. Furthermore, the cutaneous pressure threshold for patients with TOS was significantly higher in both positions than it was in the controls (p < .0001 ). It was concluded that measurement of changes in the cutaneous pressure threshold with the PSSD in distal sensory targets of the upper and lower trunk can identify patients symptomatic for compression, when the brachial plexus is provoked as part of the testing sequence.