Recommendations of the International Society of Intraoperative Neurophysiology for intraoperative somatosensory evoked potentials
來源：Clinical Neurophysiology 2019,130(1):161-179
作者：D.B. MacDonald, C. Dong, R. Quatrale
譯者：Eason 校對：Yuan
Abstract
摘要
Intraoperative somatosensory evoked potentials (SEPs) provide dorsal somatosensory system functional and localizing information, and complement motor evoked potentials. Correct application and interpretation require in-depth knowledge of relevant anatomy, electrophysiology, and techniques. It is advisable to facilitate cortical SEPs with total intravenous propofol–opioid or similarly favorable anesthesia. Moreover, SEP optimization is recommended to enhance surgical feedback speed and accuracy by maximizing signal-to-noise ratio (SNR); it consists of selecting highest-SNR peripheral and cortical derivations while omitting low-SNR channels.
術中體感誘發電位不僅提供了脊髓背側感覺系統的功能和定位信息，還對運動誘發電位的監測起到了補充作用。正確的應用和解讀術中SEP要求對相關解剖、電生理及技術方面知識有更高的要求。本指南建議採用異丙酚-阿片類全靜脈麻醉或類似麻醉方案來優化皮層SEPs。而且，推薦通過最大化信噪比來優化SEPs從而提高給與外科醫生反饋的速度和準確性；方式包括選擇高信噪比的外周和皮層導聯，不採用低信噪比的通道。
Confounding factors causing non-surgical SEP reduction should be excluded before issuing a warning. It is advisable to facilitate their identification with peripheral SEP controls and cortical SEP systemic controls whenever possible. Warning criteria should adjust for baseline drift and reproducibility. The recommended adaptive warning criterion is visually obvious amplitude reduction from recent pre-change values and clearly exceeding trial-to-trial variability, particularly when abrupt and focal. Acquisition and interpretation should be done by qualified technical and professional level personnel.
術中報警前，需排除非手術原因導致SEP降低的多種影響因素。建議儘可能地通過外周SEP對照和皮質SEP系統對照來幫助識別。報警標準應根據基線波動和重複性進行調整。推薦的可用的報警標準是與之前波幅相比顯著降低，且明顯超過了正常變化範圍，特別是突然和集中出現的波幅的下降。SEP的採集和解讀應由合格的技術人員和專業人員來進行。
Indications for SEP monitoring include intracranial, posterior fossa, and spinal neurosurgery, as well as orthopedic spine, cerebrovascular, and descending aortic surgery. Indications for SEP mapping include sensorimotor cortex and dorsal column midline identification. Future advances could modify current recommendations.
SEP監測的適應症包括顱內、後顱窩、脊髓神經外科手術，同時還包括骨科的脊柱手術，腦血管和降主動脈手術。SEP定位適應症包括感覺運動皮質定位和脊髓背柱中線的定位。目前的推薦需要未來的進展來修正。
1.Introduction
1.介紹
Somatosensory evoked potentials (SEPs) are an important part of intraoperative neurophysiologic monitoring (IONM) because they provide functional and localizing information about the dorsal somatosensory system and complement motor evoked potentials (MEPs). This document reviews relevant anatomy, physiology, methodology, interpretation and applications and forms recommendations of the International Society of Intraoperative Neurophysiology for intraoperative SEPs. It is also endorsed by the International Federation of Clinical Neurophysiology.
體感誘發電位(SEPs) 提供了人體背側感覺系統功能和定位的信息，並作為運動誘發電位（MEPs）的監測的補充，是術中神經生理監測的重要組成部分。本文匯總了SEPs相關的解剖學、生理學、方法學、解讀和應用，組成了國際術中神經生理學學會術中SEPs監測的推薦意見，並得到國際臨床神經生理聯盟（IFCN）的認可。
This is not a clinical practice guideline as defined by the Institute of Medicine (2011) because the absence of randomized controlled trials precludes formal systematic review. Nevertheless, it is based on currently available scientific evidence and consensus expert opinion. It also recognizes that alternative methods exist, that standards of care vary with resources in different regions, and that future advances could modify subsequent recommendations. An analysis of evidence for outcome benefit is beyond the scope of this article.
根據美國醫學研究所的定義，由於缺乏隨機對照試驗，影響正式系統評價的形成，所以本文並不是一個臨床實踐指南。儘管如此，本文仍基於當前已知的科學證據和專家共識。然而不同地區的醫療標準因資源而異，且未來的研究進展將不斷完善，所以本文仍存在可以改進的地方。本文不包括預後受益的證據分析。
2.Anatomical considerations
2.解剖
As somatosensory anatomy and blood supply are important for intraoperative SEP interpretation, this section summarizes relevant information from several sources.
The dorsal somatosensory system conveys discriminative touch, vibration, and proprioception, while the anterolateral somatosensory system carries pain, light touch, and temperature sensation. Practitioners should understand that SEPs elicited by electrical peripheral nerve stimulation and recorded in100 ms sweeps selectively test the dorsal system because its abundant thick peripheral axons have low thresholds and fast, uniform conduction. These techniques do not assess the anterolateral system because its thinner axons have higher thresholds and slower, more variable conduction.
軀體感覺系統的解剖和血供對術中SEP的解讀非常重要，本節總結如下：脊髓背側的軀體感覺系統主要傳導辨別覺、振動覺、本體感覺，前外側的軀體感覺系統主要傳導痛覺、輕觸覺和溫度覺。從業人員應明白，由於背側軀體感覺系統的外周軸突刺激閾值低、傳導均勻、快速，從周圍神經電刺激誘發的潛伏期小於100ms的SEP是有選擇性地監測背側系統，並非評估前外側系統，因為前外側系統的軸突薄，刺激閾值高，傳導速度慢且不穩定。
2.1. Dorsal somatosensory pathway
2.1背側軀體感覺傳導通路
The dorsal system has cutaneous discriminative touch and vibration receptors as well as muscle spindle and other deep receptors for limb proprioception. The primary afferents travel up peripheral nerves, plexuses and sensory roots. Cervicothoracic roots have an approximately horizontal trajectory from their neural foramen to the cord, while lumbosacral roots ascend the spinal canal in the cauda equina to reach the cord that ends at the L1–L2 vertebrae. The afferent fibers pass by their pseudo-unipolar cell bodies in the dorsal root ganglia, reach the dorsal root entry zone and then bifurcate up and down and rebranch within the spinal cord (Niu et al., 2013).
背側系統包括皮膚辨別性觸覺、振動覺感受器以及肢體本體感覺的肌梭和其他深部感受器。初級傳入纖維是走行於外周神經、神經叢和感覺神經根。頸胸段神經根從椎間孔到脊髓水平大概一致，而腰骶神經根沿著馬尾神經根在椎管內上行並止於L1-L2椎體。傳入纖維在背根神經節通過其假單極細胞體傳導，到達脊髓背根神經入口後分叉，並在脊髓內重新分支。
Some branches ascend the entire ipsilateral dorsal column, with leg fibers in the medial gracile fasciculus and arm fibers in the lateral cuneate fasciculus. These long afferents terminate in the gracile and cuneate nuclei of the medulla, from which second-order axons decussate as the internal arcuate fibers and then ascend the contralateral medial lemniscus to synapse in the ventral posterolateral thalamic nucleus. Third-order axons ascend the posterior limb of the internal capsule and then fan out in the thalamocortical radiation to synapse in the primary sensory gyrus (S1), with arm fibers going to its lateral convexity and leg fibers to its mesial parasagittal region.
一些分支沿一側背柱上升，下肢纖維位於內側薄束，上肢纖維位於外側楔束。這些長的傳入纖維終止於延髓薄束核和楔束核，二級神經元軸突以弓狀纖維交叉到對側形成內側丘系，然後上行至丘腦腹後外側核的突觸。三級神經元軸突上行至內囊後肢，經丘腦皮質束呈扇形輻射至初級感覺皮質，上肢的纖維分布靠大腦皮層外側，下肢纖維分布於近中線區域。
Other branches synapse in spinal cord gray matter. These include muscle spindle afferent collateral branches that form the sensory arc of tendon stretch reflexes (Niu et al., 2013). Some branches terminate in the dorsal horn, from which second-order axons reenter and ascend the dorsal column. The dorsal columns also contain descending axons involved in sensory modulation, and propriospinal axons (Fitzgerald, 1992).
脊髓灰質中的其他分支突觸，包括形成肌肉牽張反射的感覺弧的肌梭傳入側支。一些分支終止於后角，二級軸突從此重新進入和上行至背柱。背柱也包含參與感覺調節的下行軸突和脊髓固有神經元軸突。
2.2. Indirect proprioception pathways
2.2間接本體感覺傳導通路
The traditional view that proprioception afferents projecting to cortex directly ascend the dorsal columns is controversial. One alternative based on animal evidence proposes that they synapse in the dorsal horn, with second-order axons ascending the dorsolateral funiculus just behind the corticospinal tract (Gilman, 2002). Another proposes that they terminate in Clarke’s column, with second-order axons ascending the dorsolateral funiculus in the spinocerebellar tract just superfificial to the corticospinal tract (Landgren et al., 1971; Gilman, 2002; Niu et al., 2013).
傳統觀點認為本體感覺傳入直接通過背柱上行投射到皮層上是有爭議的。其中一種基於動物實驗證據的觀點認為它們在脊髓后角形成突觸，次級軸突上行至皮質脊髓束後方的背側索。另一種觀點認為它們終止於Clarke氏柱，其次級軸突上行於僅淺於皮質脊髓束的脊髓小腦束背外側索。
The extent of these indirect pathways in humans is uncertain (Ross et al., 1979; Lockard and Kempe, 1988; Ross, 1991) and the issue is relevant to SEP interpretation. For example, it is thought that dorsolateral funiculus conduction generates lower limb spinal epidural SEP components (Jones et al., 1982; Halonen et al., 1989). It has also been proposed that dorsolateral funiculus conduction generates lower limb scalp SEPs (York, 1985). However, recordings during intramedullary spinal cord tumor surgery indicate dorsal column conduction (Fig. 1). Consequently, if indirect proprioceptive pathways exist then lower limb scalp SEPs could represent mostly cutaneous afferents. Furthermore, there is unresolved uncertainty about proprioceptive contributions to mixed-nerve SEPs in general (Burke et al., 1981; Gandevia et al., 1984; Halonen et al., 1988; Fukuda et al., 2007). Thus, practitioners should understand that scalp SEPs involve dorsal column conduction and cutaneous afferents, but that the contribution of proprioceptive afferents is unclear.
人體中這種間接的傳導通路程度並不確定，但該問題與SEPs的解讀有關。比如有研究認為背外側索傳導生成了脊髓硬膜外下肢SEP的成分，也有人提出背外側索傳導生成了頭皮的下肢SEPs。然而，在脊髓髓內腫瘤手術中的記錄卻表明了背柱傳導。（Fig1）因此，如果存在間接的本體感覺傳導通路，那麼下肢的頭皮SEPs能夠代表大多數經皮的傳入感覺。此外，總的來說本體感受器對混合神經SEPs的作用仍是不確定的。因此，從業人員應該明白，頭皮SEPs包括背柱的傳導和皮膚感覺的傳入，但是本體感受器的傳入作用仍是不確定的。
Fig1:Tibial nerve scalp SEP disappearance after cervical dorsal midline myelotomy for intramedullary spinal cord tumor surgery. This recurring observation suggests dorsal column conduction of scalp SEPs. Disruption of indirect dorsolateral funiculus sensory pathways is an unlikely explanation for SEP deterioration since the immediately adjacent corticospinal tracts are unaffected as evidenced by MEP preservation.
L, left; R, right; P37 and N20, tibial and median nerve cortical SEPs; AH, abductor hallucis; Th, thenar.
頸段背側中線髓內腫瘤術中脊髓切開後，脛神經頭皮SEP消失。這一重複觀察表明頭皮SEPs的背柱傳導。間接背外側索感覺通路的中斷不太可能解釋SEP的惡化，因MEP保存可證明緊鄰的皮質脊髓束不受影響。
L, 左; R, 右; P37 and N20, 脛神經和正中神經皮層SEPs; AH, 拇展肌; Th, 魚際肌.
2.3. Nondecussation
2.3無交叉的情況
Practitioners should also be aware that some rare brainstem malformations cause dorsal sensory system and corticospinal tract nondecussation due to absence of the internal arcuate and pyramidal decussations, so that the dorsal columns project to ipsilateral cortex (MacDonald et al., 2004a; Vulliemoz et al., 2005). Horizontal gaze palsy and progressive scoliosis is the most relevant of these conditions for IONM.
我們應該意識到，一些罕見的腦幹畸形會導致背側軀體感覺系統和皮質脊髓束未產生交叉，由於缺乏弓狀纖維和錐形交叉，背柱會直接投射到同側大腦皮質。水平凝視麻痺與進行性脊柱側凸是這類狀況中與IONM最相關的。
This autosomal recessive disorder is more likely in regions with prevalent consanguinity, such as the Middle-East where it comprised 2.3% of a series of scoliosis surgery patients (MacDonald et al., 2007). However, it also arises sporadically in other regions, including North America, Europe, and Japan. As the anomaly requires reversed-lateralization scalp monitoring derivations and will be missed unless sought, this document includes methods to routinely screen for and rarely adapt to nondecussation, without implying that it is common.
這些常染色體隱形遺傳的疾病多見於近親結婚的區域，如中東，佔脊柱側凸手術患者的2.3%。然而，它也偶爾出現在其他地區，包括北美、歐洲和日本。由於這種異常需要使用反向單側化頭皮導聯來監測，除非特意註明，容易被忽略，本文包含常規篩選和少量的適用於無感覺交叉的情況，但並不意味著這是常見狀況。
2.4. Blood supply
2.4 血供
The anterior cerebral artery supplies the mesial S1 gyrus and subcortical sensory fibers for the lower limb, while the middle cerebral artery supplies the lateral S1 gyrus and subcortical sensory fibers for the upper limb. Thus, tibial and median nerve SEPs are relevant monitors for anterior and middle cerebral artery ischemia, respectively.
大腦前動脈供應支配下肢的近中線S1回和皮質下的感覺傳導白質纖維，大腦中動脈供應支配上肢的外側S1回和皮質下感覺傳導白質纖維。因此，監測脛神經和正中神經的SEPs分別與大腦前及大腦中動脈的缺血相關。
Lenticulostriate branches of the middle cerebral and anterior choroidal arteries supply thalamocortical sensory axons. Posterior cerebral artery branches supply thalamic sensory nuclei. Basilar and vertebral artery branches supply the medial lemniscus.
大腦中動脈的豆紋動脈分支和脈絡膜前動脈分支供應丘腦皮質束的感覺軸突。大腦後動脈分支供應丘腦感覺核團。基底動脈和椎動脈分支供應內側丘系。
The left and right posterior spinal arteries supply the dorsal columns and outer dorsal horns, while the anterior spinal artery supplies the remaining gray matter and inner white matter, including the anterior horns and corticospinal tracts (Mawad et al., 1990; Connolly, 1998). These longitudinal arteries also form pial anastomoses supplying the outer white matter, and receive collateral supply from cervical, aortic, and iliac radicular arteries.
左右脊髓後動脈供應脊髓背柱和後外側角，脊髓前動脈供應餘下的灰質和內部白質部分，包括脊髓前角和皮質脊髓束。這些縱行的動脈同時與軟腦膜吻合供應外側白質部分，接受頸動脈、主動脈、髂根動脈的側支供血。
Autoregulation adjusts brain and spinal cord blood flow to metabolic need across a range of blood pressure and persists under anesthesia. Due to higher metabolic rate, spinal gray matter receives four times more blood flow than white matter and is more sensitive to ischemia (Marcus et al., 1977). Consequently, acute cord ischemia causes rapid muscle MEP disappearance due to anterior horn cell failure but delayed or no deterioration of SEPs conducted through the relatively resistant dorsal columns (MacDonald and Dong, 2008). Thus, very abrupt SEP deterioration during spinal cord monitoring may suggest another pathophysiology, such as compression.
自動調節機制使大腦和脊髓的血流在大範圍波動的血壓範圍內滿足代謝需要，並在麻醉狀態下維持。脊髓灰質代謝率較高，血流量是白質的四倍，對缺血更加敏感。因此，急性的脊髓缺血導致的脊髓前角細胞功能衰竭，肌源性MEP迅速消失，但是由於相對缺血耐受，通過背柱的SEP傳導會出現延遲變化或沒有變化。因此，在脊髓監測中，突然的SEP惡化的可能提示其它的病理生理變化，如壓迫。
未完待續~~~
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