F wave evaluation of thoracic outlet syndrome: a multiple regression derived F wave latency predicting technique

To assess the occurrence of a neurologic verus a vascular component of thoracic outlet syndrome (TOS), ulnar nerve function via the F wave was studied in 16 patients with clinically diagnosed TOS and 38 control subjects. To simplify the procedure the following formula was developed, through multiple regression analysis, which can predict the ulnar F wave latency in an individual: [arm length (cm) x 0.31] minus [ulnar nerve forearm velocity (meters/sec) x 0.123] plus [11.05]. The mean plus 2 standard deviations, the maximum acceptable prolongation above the predicted value, is 2.5 msec. This formula can be used for assessment of any ulnar nerve conduction defect. Using this technique, some patients with clinically diagnosed TOS were shown to have slowed conduction of the ulnar nerve through the thoracic outlet.