経鼻咽頭電極記録の体性感覚誘発電位ならびに上行性脊髄誘発電位の起源と有用性の検討

概要

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Median somatosensory evoked potential (SEP) and ascending spinal cord evoked potential (ascending-SCEP) obtained from nasopharyngeal recordings were studied in 227 patients (age of 5-80 years, averaged 56.7 years). For SEP, two negative potentials were recorded after median nerve stimulation. The mean latency of the first negative potential (n1) was 14 msec, and the n1 wave form coincided fairly well with the inverted P13/14 far field potential obtained from noncephalic (scalp) recording. Nasopharyngeal electrodes were located at the ventral brain stem at approximately the same level of the medial lemniscus that generates the P13/14. Thus, the origin of n1 was suspected to be the medulla oblongata similar to P13/14. The second negative potential (n2) of the SEP recorded after peripheral nerve stimulation was considered to correspond to N20 of the parietal SEP. Ascending-SCEP following spinal cord stimulation recorded by nasopharyngeal electrodes showed three negative waves. The first and second negative waves were conductive potential, and the third negative potential was speculated to be the post-synaptic potential. The sensitivity and specificity of ascending-SCEP to detect new postoperative neurological deficits were 46.2% and 98.9%, respectively. SEP and ascending-SCEP were useful for intraoperative monitoring of the cervico-medullaly junction, the cervical spinal cord, and cervical roots.