Chapter

Thoracic Dermatomes

Jay A. Liveson and Dong M. Ma

in Laboratory Reference for Clinical Neurophysiology

Published in print May 1999 | ISBN: 9780195129243
Published online March 2012 | e-ISBN: 9780199847792 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780195129243.003.0005
Thoracic Dermatomes

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The twelve pairs of intercostal nerves consist of the anterior rami supplying the sensation of the trunk. The nerves can be divided into those running a thoracic course (T2 through T6), and those with a thoracoabdominal course. The former provide the motor supply to the intercostal muscles. The latter innervate the abdominal muscles, ending on the rectus abdominis. These nerves can be entrapped along their course. They also may be involved in respiratory abnormalities. For stimulation, surface electrodes, comma-shaped, at proximal sites (just lateral to the paraspinal muscles) and distal sites (six centimeters behind the costal margin) in the same costal interspace. Patients lie on the opposite side with arm rested overhead. It is unnecessary to hold one's breath. Supramaximal stimulation requires a higher voltage at the proximal site. Onset latencies and negative peak amplitudes are measured. Contralateral comparisons could be made of latencies and velocities, but not amplitudes.

Keywords: intercostal nerves; rami; latencies; velocities; thoracic course; thoracoabdominal course; supramaximal stimulation; rectus abdominis

Chapter.  431 words.  Illustrated.

Subjects: Neuroscience

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