Recording Somatosensory Evoked Potential of the Posterior Tibial Nerve with a Subdural Strip during Surgery for Spinal Dysraphism and Tethered Cord Syndrome

Objective: To investigate the feasibility of a subdural strip, placed just proximal to the surgical field, to record somatosensory evoked potentials (SSEPs) of the posterior tibial nerve (PTN) during detethering surgery for spinal dysraphism and/or tethered cord syndrome (TCS). Method: Twenty three patients (thirteen boys and ten girls; age, 4 months to 15 years) were enrolled in this study. Eleven patients had lipomyelomeningoceles, seven had TCS, two had split cord malformations, one with terminal myelocystocele, one with VACTERL syndrome, and one had a spinal tumor at the T11 to L4 level. Aside from the routine preparation needed for functional mapping and monitoring during surgery for spinal dysraphism and TCS, a 1×4 strip was placed rostral to the surgical field where it was secured by a surgeon after opening of the dura. Under total intravenous anesthesia, we stimulated the PTN and simultaneously recorded SSEPs with this strip and subdermal needles at Cz-Fz. Results: With the exception of one patient, SSEP amplitudes obtained by subdural recordings were much larger than cortical recordings. Moreover, much less averaging was necessary to get a clear subdural SSEP when compared to the averaging needed to obtain a clear cortical SSEP (10 vs. 200 averages, respectively). All recordings were stable throughout the surgical procedures and none of the patients sustained new functional deficits after surgery. Conclusions: Recording SSEPs of the PTN through a subdural strip proved to be a feasible and valuable tool during detethering surgery in young patients. When compared to recordings obtained byconventional cortical SSEPs, this approach could improve both the safety and efficiency of surgical procedures.

關鍵字

somatosensory evoked potentials ； intraoperative monitoring ； spinal dysraphism ； tethered cord syndrome

並列摘要

研究目的：擬探討在進行脊柱裂及脊髓牽扯症候群的手術時，使用硬膜下電極紀錄後脛神經的體感覺誘發電位的可行性。研究方法：總共收集了23位患者，13位男孩，10位女孩，年齡在4個月大到15歲間。疾病診斷分別為脂肪脊髓脊膜膨出(11)、脊髓牽扯症候群(7)、脊髓發育畸形(3)、VACTERL症候群(1)及脊髓腫瘤(1)等。除了常規使用的監測方法以外，在外科醫師打開硬膜後，會將一條硬膜下電極固定在手術部位的頭端。在全靜脈麻醉下，刺激後脛神經時同時在頭頂Cz-Fz及硬膜下電極紀錄體感覺誘發電位。結果：除了一位患者以外，所有患者用硬膜下電極紀錄記錄到的體感覺誘發電位的振幅都明顯大於皮質體感覺誘發電位。同時有別於一般需連續電200下才能取得一個穩定的皮質體感覺誘發電位判讀，硬膜下電極紀錄到的體感覺誘發電位只需要不到10下的刺激即可取得，節省了很多等待時間。本研究中，所有的硬膜下電極紀錄到的體感覺誘發電位在術中都維持穩定，同時所有患者術後都沒有新的神經功能障礙發生。結論：在脊柱裂及脊髓牽扯症候群手術中，使用硬膜下電極紀錄後脛神經的體感覺誘發電位證實為一個有價值的監測神經功能方法。與傳統的皮質體感覺誘發電位比較，這種紀錄法除了可以提升手術的安全性以外，也可以促進手術的效率。

並列關鍵字

體感覺誘發電位(somatosensory evoked potentials) ；術中監測(intraoperative monitoring) ；脊柱裂(spinal dysraphism) ；脊髓牽扯症候群(tethered cord syndrome)

參考文獻

1. Khealani B, Husain AM. Neurophysiologic intraoperative monitoring during surgery for tethered cord syndrome. J Clin Neurophysiol 2009;26:76−81.

2. Hertzler DA, DePowell JJ, Stevenson CB, et al. Tethered cord syndrome: a review of the literature from embryology to adult presentation. Neurosurg Focus 2010;29 (1):E1.

5. Bowman RM, McLone DG. Neurosurgical management of spina bifida: research issues. Dev Disabil Res Rev 2010;16:82−87.

6. Zamel KM. Special considerations in pediatric surgical monitoring. In: Galloway GM, Nuwer MR, Lopez JR, Zamel KM (eds) Intraoperative neurophysiologic monitoring, 1st ed. Cambridge, New York, 2010, p163-171.

7. Pouratian N, Elias WJ, Jane JA, et al. Electrophysiologically guided untethering of secondary tethered spinal cord syndrome. Neurosurg Focus 2010;29 (1):E3.

國際替代計量

Recording Somatosensory Evoked Potential of the Posterior Tibial Nerve with a Subdural Strip during Surgery for Spinal Dysraphism and Tethered Cord Syndrome

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