Provocative F waves may help in the diagnosis of thoracic outlet syndrome: a report of three cases.

To determine the value of F waves in provocative positions for the diagnosis of thoracic outlet syndrome, we performed provocative maneuvers on three patients with a clinical diagnosis of thoracic outlet syndrome. The patients had complained of intermittent upper limb pain with associated weakness and paresthesias for several years, and previous evaluations included essentially normal cervical and shoulder imaging studies and electrodiagnostic studies. Although upper limb nerve conduction studies, including ulnar and median F waves, were within normal limits, provocative F waves were obtained in the symptomatic and asymptomatic arm. When routine nerve conduction studies are normal, despite a strong clinical suspicion, provocative maneuvers may help to show subtle electrodiagnostic abnormalities to support the diagnosis of thoracic outlet syndrome.