Somatosensory evoked potentials: Lack of value for diagnosis of thoracic outlet syndrome

Abstract

Twenty patients with thoracic outlet syndrome (TOS) seen at the Mayo Clinic between October 1984 and November 1985 were studied prospectively with routine nerve conduction studies, concentric needle examination, and bilateral median and ulnar somatosensory evoked potentials (SEPs). Results of nerve conduction studies and needle examination were abnormal in 30% of the patients, one patient having a reduced ulnar sensory nerve action potential amplitude and five others having neurogenic motor unit potential changes in the hand muscles. Ulnar SEPs were abnormal in three patients (15%), and median SEPs were abnormal in one patient, who also had abnormalities in ulnar SEPs. In patients with TOS, routine nerve conduction studies and needle examination were the most helpful electrophysiologic studies in excluding more common conditions. The routine use of ulnar SEPs in the evaluation of patients with TOS is probably not worthwhile.

True neurogenic thoracic outlet syndrome: Electrophysiological diagnosis in six cases

“…There are reports of a focal proximal slowing by stimulating at Erb's point and recording at the hypothenar muscles. 1,13,14 However, the reliability of these reports has been questioned. 2,4,16 Direct needle stimulation of the C8 root and surface stimulation in the supraclavicular fossa have been used to measure conduction across the thoracic outlet.…”

“…12 The use of somatosensory evoked potentials for diagnostic purposes has also been questioned. 14,22 Our 6 patients had clinical features typical of true neurogenic TOS. All were female and presented marked atrophy of the thenar muscles.…”

Thoracic Outlet Syndrome

“…Furthermore, in the case of positive results, F-wave may not be useful in narrowing the differential or localizing the lesion as the causative fiber loss may be expected in patients with severe denervation, regardless of the etiology. [43][44][45] Somatosensory evoked potentials studies have been found useful in some reports. 46,47 However, somatosensory evoked potential has also been criticized as nonspecific, nonlocalizing, and rarely abnormal.…”

Neuromuscular and musculoskeletal problems in instrumental musicians

“…The ulnar NCS reported as useful in TOS 84 has been shown to be of no value, 87 as have other techniques designed to assess this segment of the peripheral nervous system. 85 Symptomatic TOS remains as a clinical diagnosis.…”