Electrodiagnostic values through the thoracic outlet using C8 root needle studies, F-waves, and cervical somatosensory evoked potentials
Livingstone, E.F.; DeLisa, J.A.; Halar, E.M.
Archives of Physical Medicine and Rehabilitation 65(11): 726-730
1984
ISSN/ISBN: 0003-9993 PMID: 6497620 Document Number: 241517
Mid-humerus cadaver determination of ulnar F-wave, C7 spinal somatosensory evoked potential (SEP), and modified C8 root stimulation (RS) were performed bilaterally on 20 normal subjects to standardize technique and obtain normal values for the segment from mid-humerus to cervical spine. The cadaver study shows that the best position for upper extremity measurement of mid-humerus-cervical spine distance is at 60.degree. of shoulder abduction, 45.degree. of internal rotation and at the distance of 35 cm, measured by caliper. Using this position and distance the following normal values were obtained: Mid-humerus F-wave minimal, maximal mean latencies and minimal nerve conduction velocity (NCV) were 21.8 .+-. 1.2 ms, 22.3 .+-. 1.2 ms, 22.3 .+-. 1.1 ms and 59.7 .+-. 2.4 m/s, respectively. Latency difference between minimal and maximal F-wave was 1.4 .+-. 0.4 ms. Cervical spine SEP was 5.1 .+-. 0.4 ms, with left to right difference of < 0.9 ms. C8 RS and mid-humerus ulnar nerve (UN) pick-up latency and NCV were 4.9 .+-. 0.2 ms and 71.4 .+-. 2.2 m/s, whereas C8 root pick-up and mid-humerus UN stimulation latency and NCV were 5.2 .+-. 0.4 ms and 66.9 .+-. 5.2 m/s, respectively. To evaluate proximal nerve conductivity through the thoracic outlet, the sequential use of the 3 modified techniques for 35 cm mid-humerus-cervical spine distance is recommended. The use of these techniques in diagnosing thoracic outlet compression is discussed.