What are the cervical components of upper limb somatosensory evoked potentials (SEPs)?

Updated: Feb 26, 2019
  • Author: Sombat Muengtaweepongsa, MD, MSc; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

An SEP component that most likely arises in the first-order afferent neuron at or near the dorsal root entry zone (ie, in the dorsal root and/or the dorsal column) can be recorded as a far-field P11 peak in scalp-to-noncephalic reference recordings and as a near-field N11 peak in surface recordings over the lower cervical spine. This component is small, and it is not identifiable in all healthy subjects. [5]

A larger and more consistent component recorded over the lower cervical spine (eg, at SC5 or SC7) is N13. N13 has a horizontally oriented voltage field, negative dorsally and positive ventrally (see image below), and is generated by postsynaptic activity of neurons in the gray matter of the lower cervical spinal cord. It sometimes is called the stationary cervical potential, because its latency is not affected by changes in the cervical recording electrode location. [6]

Somatosensory evoked potentials (SEPs) to stimulat Somatosensory evoked potentials (SEPs) to stimulation of the left median nerve, recorded from a ring of electrodes placed around the neck at the level of SC5 posteriorly and the superior border of the thyroid cartilage anteriorly. Courtesy of Emerson et al, 1984.

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