title: Somatosensory evoked potential from S1 nerve root stimulation.
abstract: The objective of this study was to detect cerebral potentials elicited by proximal stimulation of the first sacral (S1) nerve root at the S1 dorsal foramen and to investigate latency and amplitude of the first cerebral potential. Tibial nerve SEP and S1 nerve root SEP were obtained from 20 healthy subjects and 5 patients with unilateral sciatic nerve or tibial nerve injury. Stimulation of the S1 nerve root was performed by a needle electrode via the S1 dorsal foramen. Cerebral potentials were recorded twice to document reproducibility. Latencies and amplitudes of the first cerebral potentials were recorded. Reproducible cerebral evoked potentials were recorded and P20s were identified in 36 of 40 limbs in the healthy subjects. The mean latency of P20 was 19.8 ± 1.6 ms. The mean amplitude of P20-N30 was 1.2 ± 0.9 μV. In the five patients, P40 of tibial nerve SEP was absent, while well-defined cerebral potentials of S1 nerve root SEP were recorded and P20 was identified from the involved side. This method may be useful in detecting S1 nerve root lesion and other disorders affecting the proximal portions of somatosensory pathway. Combined with tibial nerve SEP, it may provide useful information for diagnosis of lesions affecting the peripheral nerve versus the central portion of somatosensory pathway.
authors.affiliation: Department of Orthopaedics, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai 200003, China.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Wu
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhu
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Chen
authors.forename: Xiang
authors.initials: X
authors.lastname: Jin
authors.forename: Nicholas
authors.initials: N
authors.lastname: Tsai
authors.forename: Huang-Yuan
authors.initials: HY
authors.lastname: Huang
authors.forename: Jian-Yuan
authors.initials: JY
authors.lastname: Jiang
authors.forename: Dong-Qing
authors.initials: DQ
authors.lastname: Zhu
authors.forename: Pei-Ying
authors.initials: PY
authors.lastname: Li
authors.forename: Robert
authors.initials: R
authors.lastname: Weber
authors.forename: Wen
authors.initials: W
authors.lastname: Yuan
authors.forename: Hua-Jiang
authors.initials: HJ
authors.lastname: Chen
mesh_terms: D000328:Adult; D004568:Electrodiagnosis / Q000379:methods*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012584:Sciatic Nerve / Q000502:physiology; D020426:Sciatic Neuropathy / Q000175:diagnosis / Q000503:physiopathology*; D013126:Spinal Nerve Roots / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology; D020429:Tibial Neuropathy / Q000175:diagnosis / Q000503:physiopathology*; D055815:Young Adult