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 (20 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(TM) (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) posit ions. In the control subjects, there was no significant change in the cutan eous pressure threshold between unprovoked and provoked positions. In contr ast, in patients with TOS, there was a significant increase in the cutaneou s pressure threshold at both sites (p <.0001) between the unprovoked and th e provoked positions Furthermore, the cutaneous pressure threshold for pati ents 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 c utaneous 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.