Which channels are used in normal upper-limb (median nerve) short-latency somatosensory evoked potential (SEP) testing?

Updated: Oct 25, 2019
  • Author: Andrew B Evans, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

For this test, at least 3 channels are needed, but 4 channels are generally used, as follows:

  • Erb point to Fz

  • Nuchal midline C2 spine electrode to Fz

  • Contralateral somatosensory area scalp electrode to Fz

  • Extra channel - Erb point to contralateral scalp; polarity is arranged so that active electrodes, Erb point, cervical, and cortical result in an upward deflection, representing negativity, with Fz used as the reference electrode for the upper-extremity EP; this electrode location on the scalp is not inactive and may attain electronegativity at 19-20 msec after stimulation that is equal or nearly equal to that at the contralateral cortical site and abolishes N19 in Cc-Fz derivation


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