Spectral analysis of corticomotor evoked potentials in spinal cord injury. Part 2. Chronic studies

Abstract

Corticomotor evoked potentials (CMEPs) have been suggested to accurately reflect neurological function, particularly with regard to the integrity of the spinal cord. However, the utility of these potentials to evaluate gradedchronic injury has received little attention. Frequency analysis has been suggested by the authors to be a method of simplifying interpretation of these complex signals. Ischaemic spinal cord injuries were produced in rabbits causing mild, moderate, or severe neurological deficits. CMEPs were recorded before, during, immediately following, and three days after injury. Alterations in the features of the power spectra reflected the degree of neurological injury. CMEP power spectra may predict neurological outcome and augment currently used electrodiagnostic tests. [Neurol Res 1993; 15: 373-378]     

Spectral analysis of corticomotor evoked potentials in spinal cord injury. Part 1. Acute studies

Abstract

A model of graded spinal cord injury using ischaemia has been developed by using balloon occlusion of the abdominal aorta in rabbits. This model has been used to test pharmacological agents thought to provide protection against spinal cord injury based on changes in corticomotor evoked potentials (CMEPs). These highly reproducible signals are percutaneously recorded from the spinal cord in response to cortical stimulation and accurately reflect the degree of residual spinal cord function. The present study focused on the power spectra of CMEPs to clarify alterations in post-injury signals. This added dimension of previously unreported CMEP analysis will augmentfuture applications of the current model. [Neurol Res 1993; 15: 367-372]     

Descending lumbosacral cord potentials (DLCP) evoked by stimulation of the median nerve

In 22 normal human subjects, descending lumbosacral cord potentials (DLCP) were recorded intrathecally after stimulation of the median nerve at the elbow. The onset of DLCP is very short in latency (mean 12.1 ms) with a prominent sharp early positive peak (mean latency 13.7 ms) followed by a sharp negative peak (mean 17.6 ms). The amplitude of the first part of DLCP varied between 0.6 and 6.7 microV (mean 2.3 microV). The response was recorded most easily when the tip of intrathecal electrode was posterolaterally positioned. The threshold of the response was above or around the excitation threshold of the motor nerve fibers and it could not be produced by pure skin nerve stimulation. It resisted to subtetanic peripheral shocks. Mean peripheral conduction velocity responsible for the response was about 60.8 m/s. Some late and slower deflections appeared in many cases. It was concluded that the DLCP must have originated from the descending and very fast conducting propriospinal pathways located within the anterolateral funiculus which has an oligosynaptic anatomical organization. This response seemed to be the first direct evidence of interlimb reflex action between the arm and leg in man which is important in the coordination of movements and posture.     

Spinal cord conduction pathway for cerebellar evoked potentials from C-fibers

Evoked responses from saphenous nerve C fiber stimulation were identified on the ipsilateral intermediate cerebellar cortex. This late potential has a latency between 180 and 250 msec, duration 50–70 msec, and an amplitude 10–20 μV. The potential is conducted in the ipsilateral dorsal quadrant as determined by differential section of the spinal cord. The probable pathway is assigned to the dorsal spinocerebellar tract.     

Monitoring spinal cord motor and somatosensory evoked potentials in anesthetized primates

Abstract

Monitoring Motor Evoked Potential (MEP) to Transcranial Stimulation (TMS) monitoring (MEP) is a growing technique to assess motor function under anesthesia. The following primate study was conducted to analyze the non-myogenic spinal motor and sensory volleys and to examine their reproducibility under nitrous oxide-methohexidone anesthesia. The traveling periodic spinal descending MEP to TMS and ascending somatosensory (SEP) to posterior tibial nerve stimulation across the thoracic cord were recorded in 12 cynomolgus monkeys. Through a small Tn~Tu laminotomy, an insulated stainless steel electrode was inserted into the epidural thoracic space. The potentials were analyzed under 50 vol% NO in 02 with methohexital (0.1-0.2 mg kg~1 min~1). A well-defined periodic TMS-MEPs and PTN-SEPs were recorded with high reproducibility and consistency in repeated trials under N20-methohexital anesthesia. MEP tracing consisted of an initial peak (direct (D) wave), occurring at 2.43 (±0.28) msec followed by subsequent five positive (indirect (I) waves). Spinal SEPs-MEPs were clearly defined, morphologically stable, and consistent over time under N20-methohexitone anesthesia. The present primate study may set a model to monitor both modalities in anesthetized neurosurgical patients.[Neurol Res 1999; 21: 359-367]     

运动诱发电位联合体感诱发电位监测在脊髓髓内肿瘤手术中的应用

目的 探讨全静脉麻醉下运动诱发电位(MEP)联合体感诱发电位(SEP)术中监测应用于脊髓髓内肿瘤手术的优越性、可靠性及临床应用价值.方法 对72例脊髓髓内肿瘤患者术中行SEP和MEP联合监测,参照McCormick评分标准对术前、术后脊髓功能的改变和诱发电位变化之间的关系进行统计分析.结果 14例脊髓神经功能改善,18例术后脊髓神经功能下降者与诱发电位监测结果具有一致性(P＜0.05).结论 对脊髓髓内肿瘤手术进行SEP与MEP监测有利于避免"假阴性/假阳性"结果及术后神经功能障碍的发生.     

Spinal evoked potentials in normal Japanese infants and children

The spinal evoked potentials on right peroneal nerve stimulation were recorded with surface electrodes in 58 normal children of 41 weeks to 15 years old. Bipolar recordings were performed. In all subjects, tri- or quadri -phasic potentials with poorly defined initial positive phases were recorded. The latency of the evoked potentials increased progressively from the lumbar to cervical location. The peripheral conduction velocity from the stimulating cathode in the popliteal fossa to the lumbar recording location increased until 4 or 5 years, and then reached a plateau. Spinal conduction velocity between the lumbar and cervical locations increased until 7 years, and then remained constant.     

Megnetic motor evoked potentials (MEP) in diseases of the spinal cord

Transcranial magnetic stimulation (TMS) is a non-invasive diagnostic method particularly suited to investigation of the long motor tracts. The clinical value of this method in many cortical and subcortical diseases has been well established, but comparable studies for most spinal cord diseases have still to be made. Forty patients in whom spinal cord disease was established by clinical examination, cerebrospinal fluid examination, and magnetic resonance imaging (MRI) were studied by means of somatosensory evoked potentials (SEP, median and tibial nerve stimulation) and magnetic motor evoked potentials (MEP, first dorsal interosseus and tibialis anterior muscle recordings after transcranial and spinal stimulation). The underlying pathology was neoplastic (n= 16), inflammatory (n= 15) or ischemic (n = 9). Clinical signs and symptoms ranged from slight sensory disturbances to complete paraplegia and had developed within minutes (ischemia) or over many years (benign neoplastic disease). The overall frequency of pathological SEP was slightly higher than that of MEP (78% vs 68%) which was statistically not significant (p > 0.05). This was also true for the subgroups, except for pure motor disorders, which gave the same yield for both methods. Decreased amplitudes or absence of MEP were more frequent in neoplastic than in inflammatory lesions (75% vs 33%, p < 0.05). In the latter, however, MEP more often occurred with increased latencies (40% vs 31%, p > 0.05, n. s.). Pathological SEP were found in 75% of patients presenting with pure motor abnormalities, while pathological MEP were found in 30% of patients with pure sensory disturbances. We conclude, in common with the SEP, the MEP are helpful in the examination of spinal cord diseases, even in subclinical disturbances, although the SEP would seem to yield a larger percentage of pathological results.     

Somatosensory evoked potentials in the differential diagnosis between compression and amyotrophic srinal cord literal sclerosis

Spinal cord compression (SCC) often presents a similar clinical picture to amyotrophic lateral sclerosis (ALS). An early differential diagnosis is important because SCC is a potentially treatable clinical disorder. We carried out a longitudinal study of 43 patients with an initial diagnosis of ALS, in order to ascertain the percentage of patients with SCC, and to evaluate the usefulness of somatosensory evoked potentials (SEPs) in early diagnosis. Thirty-three patients had a final diagnosis of ALS and 8 of SCC. SEPs central conduction was abnormal in 3 ALS and 7 SCC patients, respectively (Fisher exact test, p < 0.05). We concluded that SEPs investigation is useful in the differential diagnosis between ALS and SCC patients with pure motor signs.     

皮层体感诱发电位在不同水平脊髓缺血中的变化

目的 为术中应用皮层体感诱发电位(CSEP)监测脊髓功能,预防术后运动功能障碍提供理论依据. 方法 33只新西兰大白兔采用随机数字表法分为6组,对照组8只用于排除麻醉和手术对诱发电位的影响,余25只根据结扎左肾动脉和动脉分叉间节段性脊髓供血动脉的条数分为5组(n=5),分别为1～5根组.记录各组动物麻醉后基线诱发电位,血管结扎后急性期诱发电位,结扎后30 min、2 d后诱发电位.动物麻醉清醒后、血管结扎后2 d时进行运动功能评分,并取缺血中心区标本行HE染色. 结果 潜伏期对缺血性损伤不敏感,实验组与对照组差异无统计学意义(P>O.05);波幅变化复杂,对运动功能特异性差,2、3、4根组均观察到急性期波幅先降低又逐渐恢复趋势,波幅的变化可以反映脊髓的病理损害程度和运动功能. 结论 缺血急性期CSEP波幅变化复杂,对运动功能特异性差,波形记录的信号需要平均化过程,造成结果 解释的延迟,术中应联合运动诱发电位对脊髓功能进行监测.     

Giant somatosensory evoked potentials in a patient with the anterior spinal artery syndrome

We studied a previously healthy 25-year-old woman with the anterior spinal artery syndrome, a rare thoracocervical myelopathy with multiple potential etiologies. Quantitative and clinical sensory examination showed dissociated loss of pin-prick and temperature discrimination below the level of the lesion, with normal light touch, vibratory, and position sense. Magnetic resonance imaging was consistent with cervical spinal cord infarction. Median SEPs showed normal Erb's potential with absent spinal N—₁₃ and normal scalp N—₂₀ latency. Tibial SEPs showed normal lumbosacral responses and normal scalp P—₃₀ latency. Both median and tibial nerve stimulation produced cortical responses of unusually large amplitude (median 38 m?V, tibial 17 m?V). We hypothesize that large SEP amplitudes in this patient resulted from loss of anterolateral inhibitory influences on the dorsal column–medial lemniscal system. © 1993 John Wiley & Soncs, Inc.     

Evaluation of spinal evoked potentials: a model for assessment of spinal cord function in isolation

Spinal evoked potentials were recorded from the dorsal columns of in vitro mouse hemicord preparations. The response of these potentials to different periods of hypoxia was studied. A decrease in amplitude of the potential to 50% and 10% of pre-hypoxia reference occurred after 3.19 ± 1.36 and 7.3 ± 2.97 min, respectively. Complete recovery of the potential was seen in specimens exposed to 5 and 10 min of hypoxia. Incomplete recovery occurred with exposure to longer periods of hypoxia. In preparations that remained isoelectric for less than 5 min total recovery was seen.     

Tethered cord after spina bifida aperta: a longitudinal study of somatosensory evoked potentials

Progressive neurological deterioration may occur after meningomyelocele repair. Magnetic resonance imaging almost invariably demonstrates a conus medullaris in an abnormally low position, whether neurological symptoms develop or not. Surgery of a secondary tethered cord is indicated when progression of neurological symptoms is documented. We performed a longitudinal study of posterior tibial nerve somatosensory evoked potentials (SSEPs) in children and adolescents after neonatal meningomyelocele repair. All patients were able to walk. Declining or negative posterior tibial nerve SSEPs were recorded in 15 patients; 14 of these had clinical signs of a secondary tethered cord. After surgery of the tethered cord, the SSEPs improved in 8 of 10 patients. Posterior tibial nerve SSEPs may contribute to the diagnosis of secondary tethered cord. After untethering, the evoked potentials demonstrate recovery of spinal cord function and might help to delineate prognosis.     

多种脊髓诱发电位测评高龄脊髓型颈椎病患者颈脊髓机能

目的调查高龄脊髓型颈椎病患者的颈脊髓机能状态,并结合磁共振影像学（MRI）及X线放射学探讨其病理生理形成机制.方法对23例MRI显示为多椎间脊髓压迫的高龄脊髓型颈椎病患者,采用经颅电刺激-脊髓硬膜外记录、经脊髓硬膜外刺激-脊髓硬膜外记录、经正中神经刺激-脊髓硬膜外记录的三种脊髓诱发电位进行颈脊髓机能测定.结果17例患者（73.9%）显示为颈脊髓单一椎间的障碍,其中10例位于C3-4、5例位于C4-5、2例位于C5-6.另外6例患者（26.1%）的正中神经刺激-脊髓硬膜外记录结果表现为多个或两个椎间的障碍.结论在MRI影像学上显示为多椎间脊髓压迫的高龄脊髓型颈椎病患者,其多数在脊髓电生理上：表现为单一颈椎椎间的脊髓白质损伤,特征是不仅脊髓后索的感觉传导束,而且侧索的皮质脊髓束也受到损伤.结合X线放射学结果分析,C3-4或C4-5颈椎椎间的过大活动度或不稳是导致高龄脊髓型颈椎病患者脊髓传导束损伤的一个重要原因.     

Hyperventilation as a model for acute ischaemic hypoxia of the brain: Effects on cortical auditory evoked potentials

Summary Controlled hyperventilation (HV) may be used as an experimental procedure to produce transient ischaemic hypoxia of the brain. The effect of HV on the cortical auditory evoked potential (AEP) components N1 and P2 was studied in ten healthy adult subjects. AEP were recorded before HV, during 3 min of controlled HV, and 1 min and 5 min after the end of HV. The P2 amplitude was significantly reduced by HV and regained its initial value 1 min after the end of HV. The P2 amplitude decrease probably reflects an impairment of synaptic function produced by cerebral hypoxia. Thus, the investigation of cortical AEP components may provide a useful parameter in the study of anti-ischaemic or antihypoxic therapies.     

Changes in spinal cord function evaluated by evoked potentials and spinal cord blood flow from a lateral retraction post-cervical laminectomy

We induced ischemia and stretching by retraction of the spinal cord after laminectomy in 12 anesthetized mongrel adult cats, recorded spinal motor evoked potential (SpMEP) and spinal somatosensory evoked potential (SpSSEP) and determined the spinal cord blood flow (SCBF). The results showed a correlation between progressive deterioration of the function and a decrease in SCBF. Comparing the abnormal findings of both the peak and interpeak latencies in evoked potentials, useful data were more frequently obtained using SpSSEP than SpMEP. Factors involved in their deteriorations seem to be a moderate ischemia by compression, and a stretching by the retraction of the spinal cord. From these results, we conclude that SCBF and SpSSEP are important for monitoring the impulse propagation during retraction of the cervical cord.     

Somatosensory evoked potentials in a case of neurosyphilis

Here we report median and common peroneal nerve SEPs in a patient with tabes dorsalis. SEPs were within normal limits following median nerve stimulation, but of prolonged latency for common peroneal nerve. This was in keeping with clinical findings of posterior column involvement confined to the lumbosacral tract and with pathological features of tabetic neurosyphilis.

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Sommario Gli autori riportano le caratteristiche dei potenziali evocati somatosensoriali del nervo mediano e peroneo comune in un paziente affetto da tabe dorsale. I potenziali evocati somatosensoriali sono risultati nei limiti della norma stimolando il nervo mediano ma di latenza aumentata per il nervo peroneo comune. Ciò risultava in accordo sia con le caratteristiche cliniche di segni di interessamento dei cordoni posteriori limitato al tratto lombosacrale che con le caratteristiche anatomopatologiche della neurosifilide.

     

Monitoring somatosensory evoked potentials in spinal cord ischemia-reperfusion injury

It remains unclear whether spinal cord ischemia-reperfusion injury caused by ischemia and other non-mechanical factors can be monitored by somatosensory evoked potentials. Therefore, we monitored spinal cord ischemia-reperfusion injury in rabbits using somatosensory evoked potential detection technology. The results showed that the somatosensory evoked potential latency was significantly prolonged and the amplitude significantly reduced until it disappeared during the period of spinal cord ischemia. After reperfusion for 30-180 minutes, the amplitude and latency began to gradually recover; at 360 minutes of reperfusion, the latency showed no significant difference compared with the pre-ischemic value, while the somatosensory evoked potential amplitude in- creased, and severe hindlimb motor dysfunctions were detected. Experimental findings suggest that changes in somatosensory evoked potentia~ ~atency can reflect the degree of spinat cord ischemic injury, while the amplitude variations are indicators of the late spinal cord reperfusion injury, which provide evidence for the assessment of limb motor function and avoid iatrogenic spinal cord injury.