Early prognosis in severe cranio-cerebral trauma using the Glasgow Coma Score and evoked potentials

During 72 h following severe head injury, 103 patients in acute posttraumatic coma were assessed by clinical examinations (documented by Glasgow Coma Score) and brain stem auditory evoked potentials (BAEP) as well as short-latency somatosensory evoked potentials (SEP) following median-nerve stimulation. Patient outcomes were classified at 6 months or more according to the following categories: good recovery, severely disabled or vegetative, and brain dead. Patients who had died of systemic complications (pneumonia, septicemia, renal failure, etc.) were excluded from the study. The Glasgow Coma Score was reliable in forecasting a favorable outcome; all patients with a Score over 9 points had a good recovery. The Glasgow Coma Score was not reliable in predicting an unfavorable outcome, however; some patients with the lowest possible Glasgow Coma Score (3 points) at the early clinical examination survived with good recovery. The BAEPs were reliable predictors of an unfavorable outcome; the outcome was unfavorable when a missing wave V or more missing waves pointed toward a secondary brainstem lesion. Normal BAEPs were not reliable, however, in predicting a favorable outcome. SEP data served as a prognostic indicator of unfavorable as well as favorable outcomes. In summary, evoked potentials add valuable information to the clinical examination in assessing a patient's outcome after severe head injury.     

Evoked potentials in the follow-up and prognosis of patients with craniocerebral trauma

The aims of this study were to find a reliable way of establishing the prognosis for the final outcome in the first week after head injury, to show the correlation between abnormalities in evoked potentials (EP) and clinical coma score, and finally, to document EP results in patients with the clinical diagnosis of brain death. We examined 46 patients, 23 in different states of coma and 23 with bulbar syndrome (complete absence of cortical and brain stem function). In the group of comatose patients brain stem auditory EP (BAEP) and somatosensory EP (SEP) were recorded in the first 48 h, 3-5 days, 1 week and 4 weeks after the head injury. The depth of coma was scaled with a scoring system devised by the authors and with the Innsbruck coma scale. Outcome was evaluated with the Glasgow outcome scale after 3, 6, and 9 months. BAEP were recorded bilaterally after stimulation with clicks; SEP were recorded from the neck (C2) and the contralateral cortex (C3', C4') after electrical stimulation of the median nerve. Evoked potentials were scored according to a four-point scale from grade 1 (normal) to grade 4 (only component I present in BAEP or absence of cortical responses on both sides in SEP). We found a significant correlation between the mean SEP score of the first week and the Glasgow outcome of the 3rd month, but no significant correlation between the BAEP score of the first week and the Glasgow outcome. There was a significant correlation between SEP (BAEP) scores and the corresponding clinical score.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prediction of the Post-Comatose Motor Function by Motor Evoked Potentials Obtained in the Acute Phase of Traumatic and Non-Traumatic Coma

Summary  Objective. To define the value of electrically elicited motor evoked potentials (MEP), obtained during the initial phase of the coma, for correct prediction of the post-coma motor status. Methods: Fifty-two patients were investigated by MEP within 72 hours after onset of the coma. It was the aim to correlate the MEP findings to the motor function two months after coma onset. Results: Three patients with normal MEP showed no post-coma motor deficit. In 21 patients, a bilateral, symmetric prolongation of the central motor conduction time (CMCT) was registered. Eighteen of these 21 patients (86%) showed a normal post-coma motor status. In 28 patients, unilaterally absent evoked potential, or unilaterally prolonged CMCT, or bilaterally prolonged CMCT with significant difference in each hemispere were observed. A post-coma contralateral paresis was found in 25 of these 28 patients (89%). That paresis was functionally important in 15 patients (54%) and functionally unimportant in 13 patients (46%). Conclusion. We identified certain MEP patterns (unilateral extinction of the evoked potential, unilateral, bilateral prolongation of the CMCT with significant “side” difference), which indicated a pyramidal tract lesion and a post-coma motor deficit with an accuracy of 89%. This refers to the motor results, which may not be the final post-coma motor results which are usually assessed six months after the coma onset. The MEP changes did not allow one to predict the severity of the paresis. The accuracy of prediction of a motor deficit increased from the MEP finding of unilaterally prolonged CMCT to the MEP finding of unilateral extinction of the potential. The most common finding, bilateral central motor slowing without significant “side” difference, did not indicate a post-coma paresis in 86%, leading to the assumption, that bilateral, symmetrical prolongation of the CMCT was not caused by lesions of the descending motor pathways, but by the drugs administered for treating the comatose patient. In conclusion, MEP allows one to predict the presence of a post-coma motor deficit with a high degree of accuracy already in the initial phase of coma, but MEP fails to predict the severity of that deficit.     

Nitrous oxide suppresses the electromyographic response evoked by electrical stimulation of the motor cortex

The influence of nitrous oxide on motor evoked potential (MEP) elicited in rats by cortical and midcervical electrical stimulation was studied and compared with early components of somatosensory evoked potential (SEP) following stimulation of the posterior tibial nerve in 6 rats. We found that nitrous oxide gradually suppresses MEP, depending on the concentration of this inhalation agent. At a concentration of 66 vol% of nitrous oxide, the MEP was completely abolished, whereas the initial component N1-P1 of the SEP was only slightly reduced. We conclude that the descending impulse elicited by electrical stimulation of the corticospinal tract is mainly inhibited at the level of the spinal neuronal or interneuronal system, since (1) neuromuscular transmission is not blocked by nitrous oxide, and (2) MEP suppression is the same following cortical and midcervical stimulation.     

Auditory brain stem evoked responses in comatose head-injured patients

Brain stem evoked responses (BSERs) were obtained within the first 72 hours after hospital admission from 38 patients with closed head injuries whose Glasgow coma scale scores were 8 or less. Peak V latency differentiated patients with unfavorable outcomes (vegetative or dead) from patients with more favorable outcomes, but no features of the response could further discriminate good, moderate, and severe outcomes as assessed by the Glasgow outcome scale. These data provide further support that BSERs are generally resistant to central nervous system trauma but, when impaired, are prognostic of unfavorable outcome.     

经颅刺激运动诱发电位联合体感诱发电位监测在脊柱畸形手术中的应用

 目的分析联合应用经颅刺激运动诱发电位(transcranial electric stimulation motor evoked potential, TcMEP)+体感诱发电位(somatosensory-evoked potential, SEP)的多模式术中神经功能监测对预 测脊柱畸形矫形手术中医原性神经功能损害的意义。方法 在脊柱畸形矫形手术中, 同时应用 TcMEP 和(或)SEP进行神经功能监测。 MEP监测采用经颅刺激 ₃、C₄, 记录外周肌源性 MEP, SEP监测采用刺 激双侧胫后神经, 记录置于 C_z-FP_z。阳性诊断标准为, 与基线相比, MEP波幅下降 75%, SEP波幅下降 50%。结果 153例脊柱畸形患者中, 150例成功进行了术中 MEP监测, 83例进行了术中 SEP监测。联 合 MEP、SEP监测的检出率为 100%。MEP监测阳性共 12例, 所有患者中有 1例出现永久性神经功能障 碍, 4例出现一过性神经功能障碍。 MEP监测的敏感性为 90.9%, 特异性为 98.6%; SEP监测敏感性为 54.5%, 特异性为 94.3%;联合 MEP、SEP监测的敏感性达 92.3%, 特异性为 99.3%。结论 联合 MEP+ SEP的多模式术中神经功能监测可提高监测的敏感性及特异性, 可预测术中神经功能损伤事件的发生。 MEP是多模式监测的基础, 而 SEP是重要补充。     

Wertigkeit früher somatosensorisch evozierter Potenziale bei intubierten und beatmeten Patienten mit Schädel-Hirn-Trauma

The objective of this study was to evaluate the prognostic value of early somatosensory evoked potentials (SEP) in patients with brain injury. A total of 85 patients who had been intubated and mechanically ventilated were investigated retrospectively. The results were compared to the Glasgow Coma Scale (GCS). The Glasgow Coma Scale as determined by the emergency doctor at the accident site, an SEP score, and the outcome of the patient were compared. There was no correlation of the Glasgow Coma Scale with the outcome. Probably the reason for this finding is the short interval of time between accident and evaluation of the GCS so that an awakening of the patient a short time after the accident is not reflected by the GCS. On the other hand, there was a significant correlation of the SEP score in the first examination after the accident with the outcome (p<0.001). SEP gave no false pessimistic prognoses. All patients without cortical responses either in one hemisphere or both hemispheres remained in coma vigile or died because of their brain injury.If cortical responses over both hemispheres remained normal, it was highly probable that the patients were later not severely handicapped. A reliable prognosis based on SEP is possible at a time when the clinical examination of the patient is limited due to sedating drugs. Repetitive examinations can monitor the course of recovery and correct false optimistic prognoses. The method may be applied at bedside and requires minimal time and little financial effort.     

Motor evoked potential in cats with acute spinal cord injury

We have previously reported that a motor evoked potential (MEP) can be produced by transcranial stimulation of the motor cortex in cats and humans. This signal travels in both dorsolateral and ventral spinal cord. We report here the evaluation of this evoked potential in comparison to the somatosensory evoked potential (SEP) in an acute spinal cord weight drop model. In all animals, the peripheral nerve signal was the component of the MEP most sensitive to injury. Often, it was significantly reduced in amplitude by incidental manipulation of the spinal cord during a careful laminectomy and then returned. It was lost first in animals with weight drop spinal cord injury and was abolished with as little as 50 to 75 g/cm of force. The spinal cord signal of the MEP was consistently more sensitive to injury than the SEP and was abolished at about 100 to 150 g/cm of impact. The cortical SEP was abolished at about 200 to 250 g/cm, and the spinal cord SEP was abolished at similar levels. The SEP returned earlier after injury than the MEP. Anesthetic agents had an effect on the MEP in the spinal cord and substantially changed the peripheral nerve signal, in both wave form shape and optimal stimulation frequency. Marginal cord injury and abnormal metabolic conditions caused the peripheral nerve signal to decrement in amplitude with increasing trial numbers during a run and become unstable. These latter effects need further characterization and are critical guides to investigative and clinical use of this test. This study indicates that the MEP is more sensitive than the SEP in detecting spinal cord injury.     

Somatosensory- and motor-evoked potential monitoring during spine and spinal cord surgery

STUDY DESIGN: Prospective, observational study. SETTING: Regional Trauma Center, Torino, Italy. OBJECTIVES: Complex spinal surgery carries a significant risk of neurological damage. The aim of this study is to determine the reliability and applicability of multimodality motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SEPs) monitoring during spine and spinal cord surgery in our institute. METHODS: Recordings of MEPs to multipulse transcranial electrical stimulation (TES) and cortical SEPs were made on 52 patients during spine and spinal cord surgery under propofol/fentanyl anaesthesia, without neuromuscular blockade. RESULTS: Combined MEPs and SEPs monitoring was successful in 38/52 patients (73.1%), whereas only MEPs from at least one of the target muscles were obtained in 12 patients (23.1%); both MEPs and SEPs were absent in two (3.8%). Significant intraoperative-evoked potential changes occurred in one or both modalities in five (10%) patients. Transitory changes were noted in two patients, whereas three had persistent changes, associated with new deficits or a worsening of the pre-existing neurological disabilities. When no postoperative changes in MEP or MEP/SEP modalities occurred, it was predictive of the absence of new motor deficits in all cases. CONCLUSION: Intraoperative combined SEP and MEP monitoring is a safe, reliable and sensitive method to detect and reduce intraoperative injury to the spinal cord. Therefore, the authors suggest that a combination of SEP/MEP techniques could be used routinely during complex spine and/or spinal cord surgery.     

Intraoperative monitoring of blood flow insufficiency during surgery of middle cerebral artery aneurysms

OBJECT: The usefulness of motor evoked potential (MEP) monitoring to detect blood flow insufficiency (BFI) in the cortical branches of the middle cerebral artery (MCA) and lenticulostriate arteries (LSAs) during MCA aneurysm surgery was investigated based on the correlation between MEP and somatosensory evoked potential (SEP) monitoring. METHODS: Fifty-three patients with MCA aneurysms underwent surgery accompanied by intraoperative MEP and SEP monitoring. There was no postoperative motor paresis in 43 patients in whom MEP and SEP results remained unchanged. In the other 10 patients, nine manifested transient MEP changes; in five of these, SEP changes did not occur. The transient MEP changes were thought to be attributable to BFI of the MCA cortical branches in two patients, the LSA in three, and either the MCA branches or the LSA in four patients. Of these nine patients, six did not present with postoperative motor paresis; transient motor paresis was recognized in the other three. In the 10th patient, MEP waves disappeared and did not recover. This patient's SEPs remained at 70% of the control level, and he developed severe hemiparesis. A postoperative computerized tomography scan revealed a new low-density area in the corona radiata and putamen. CONCLUSIONS: Blood flow insufficiency in both the LSA and MCA cortical branches that perfuse the corticospinal tract can be detected by intraoperative MEP monitoring. Somatosensory evoked potential monitoring is not reliable enough to detect BFI in the MCA branches and the LSAs.     

经颅刺激运动诱发电位联合体感诱发电位监测在特发性脊柱侧凸矫形手术中应用的研究

背景：特发性脊柱侧凸手术治疗中神经功能障碍是最应受到关注的并发症,术中神经功能监测可帮助早期发现可能的神经功能损伤。目的：分析联合应用经颅刺激运动诱发电位（TcMEP）和体感诱发电位（SEP）的多模式术中神经功能监测在特发性脊柱侧凸矫形手术中对预测医源性神经功能损害的作用。方法：在特发性脊柱侧凸矫形手术中,运用TcMEP和（或）SEP进行神经功能监测。MEP监测采用经颅刺激C3、C4,记录外周肌源性MEP,SEP监测采用刺激双侧胫后神经,记录电极采用Cz—CPz。阳性诊断标准：与基线相比,MEP波幅下降75％,SEP波幅下降50％。结果：112例特发性脊柱侧凸患者中,联合MEP、SEP监测的检出率为100％。MEP监测阳性6例,假阳性1例。1例出现一过性神经功能障碍。MEP的监测敏感性为100％,特异性为99％;SEP监测敏感性50％,特异性为100％;联合MEP、SEP监测的敏感性、特异性均为100％。结论：特发性脊柱侧凸矫形手术中MEP＋SEP的术中神经功能监测可提高监测敏感性及特异性,可预测术中神经功能损伤事件的发生。MEP是多模式监测的基础,SEP是重要补充。单独应用MEP监测在特发性脊柱侧凸患者手术中有应用前景。     

Effects of hematopoietic autologous stem cell transplantation to the chronically injured human spinal cord evaluated by motor and somatosensory evoked potentials methods

International standards for stem cell treatment of neurological disorders have not yet been established. In particular, specific quantitative methods have not yet been adopted to assess the effectiveness of stem cell treatment. The aim of this study is to evaluate the functional changes detectable by conventional neurophysiologic methods in an injured spinal cord during stem cell therapy. Twenty adult patients with chronic spinal cord injury at C4-C8 level were examined by somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) methods, the first time prior to the treatment and then regularly during its course (1-4 years). The treatment consisted of repeated intrathecal transplantations of autologous hematopoietic stem cells. After at least 1 year of treatment, four effects were detected: 1) restoration of the initially absent short-latency SEP (three patients); 2. N20P23 interpeak amplitude increase in SEP elicited by median nerve stimulation (four patients); 3) P38 latency reduction in SEP elicited by tibial nerve stimulation (two patients); 4) appearance of MEP (three patients). The nonidentical effects of stem cell transplantation in different patients presumably reflect the variety of the regeneration processes in different pathways of the spinal cord, depending on the extent and nature of lesion of the spinal cord pathways in different patients. The local effects of stem cell treatment at the cervical level were evaluated by median SEP and wrist muscle MEP demonstrate the ability of stem cells to spread within the spinal cord at least from lumbar to the cervical level, home there, and participate in the neurorestoration processes.     

Neurophysiological monitoring during scoliosis surgery using controlled hypotension

Controlled arterial hypotension understood to be a mean arterial pressure (MAP) between 55 and 60 mmHg is often used as a complementary technique in anesthesia even though it is not without complications and associated mortality even in young patients. During surgery to reduce scoliosis in a young boy, MAP fell to 60 mmHg accompanied by bilateral loss of sensory and motor evoked potentials (SEP and MEP). Detecting the absence of SEP and MEP allowed us to prevent medullar injury due to ischemia secondary to hypotension, once possible surgical or technical causes had been ruled out. We believe that monitoring SEP and MEP is useful not only to the surgeon but also to the anesthesiologist.     

Motor evoked potential monitoring with supratentorial surgery

OBJECTIVE: To assess feasibility and clinical value of motor evoked potential (MEP) monitoring with surgery close to supratentorial motor areas and pathways. METHODS: Functional mapping by somatosensory evoked potential phase reversal and continuous MEP recording after high-frequency repetitive electrical cortex stimulation was performed during 182 operations in 177 patients. Significant MEP changes were reported to trigger surgical reaction. Intraoperative surgical and electrophysiological findings were documented prospectively. Patient files were reviewed for clinical data. MEP monitoring results were correlated with motor outcome. RESULTS: MEP recording was successful in 167 cases (91.8%). Inadequate electrode placement was an important reason for failed recording in the remaining patients, whereas preoperative paresis and anesthesia had no significant effect. Permanently disabling new motor deficit occurred in 8 cases (4.9%), whereas transient and nondisabling weakness was frequent (27.4%). Significant MEP changes occurred during 64 operations (39%). Irreversible MEP loss always predicted new, usually permanent, paresis. Unaltered MEP recordings indicated unimpaired motor function in the monitored muscle groups, except for rare transient deficit because of late edema and rebleeding. Irreversible MEP deterioration without loss and reversible changes could be associated with new paresis, which was transient in most patients. No major complications were observed, except for intraoperative generalized seizure in one epilepsy patient under insufficient anticonvulsant therapy. CONCLUSION: MEP monitoring with supratentorial surgery is feasible and safe. It may help to maximize resection within the limits of preserved motor function. Further evidence is needed to confirm these results.     

Transcranial electrical motor evoked potential monitoring for brain tumor resection

OBJECTIVE: This study was designed to examine whether transcranial electrical motor evoked potential (MEP) monitoring is safe, feasible, and valuable for brain tumor surgery. METHODS: Fifty consecutive patients undergoing brain tumor resection were studied, using nitrous oxide/propofol anesthesia. MEPs were continuously recorded throughout surgery, using a Sentinel 4 evoked potential system (Axon Systems, Inc., Hauppauge, NY). The MEPs were elicited by transcranial electrical stimulation (train of 5; stimulation rate, 0.5-2 Hz; square wave pulse with a time constant of 0.5 ms; stimulation intensity, 40-160 mA) through spiral electrodes placed over the primary motor cortex and were recorded by needle electrodes inserted into the contralateral orbicularis oris, biceps, abductor pollicis brevis, and anterior tibialis muscles. When MEP amplitudes decreased by more than 50%, MEP stimulation was repeated, with increased stimulation intensity, and MEP changes were reported to the surgeon. The motor function of each patient was examined before and after surgery, using a reproducible scale. The relationship between MEP amplitude decreases and worsening motor status was analyzed using linear regression. RESULTS: Preoperative neurological examinations revealed mild to moderate motor deficits (2/5 to 4/5) for 38% of patients (19 of 50 patients). Most of the patients (96%) exhibited recordable baseline MEPs. Persistent MEP decreases of more than 50% were noted for eight patients (16%) (11 muscles). The MEPs were completely abolished in two patients (three muscles). The degree of postoperative worsening of motor status was correlated with the degree of intraoperative MEP amplitude reduction (r = -0.864; P < 0.001). CONCLUSION: Persistent intraoperative MEP reductions of more than 50% were associated with postoperative motor deficits. The degree of MEP amplitude reduction was correlated with postoperative worsening of motor status. Transcranial electrical MEP monitoring is feasible, safe, and valuable for brain tumor surgery.     

术中无肌松全静脉麻醉用于联合神经电生理监护脊柱手术的可行性

［摘要］ 目的 比较全静脉麻醉下术中使用或不使用肌松药对脊柱手术中联合神经电生理监测结果的影响,探讨安全有效的神经电生理监测麻醉方案。方法 选择拟行联合神经电生理监测的择期脊柱手术病人 40 例,分为A、B两组。两组病人均采用丙泊酚、瑞芬太尼和右美托咪定全凭静脉麻醉,A组病人术中使用小剂量阿曲库铵维持肌松,B组病人术中不使用肌松药。同时监测体感诱发电位（SEP）和运动诱发电位（MEP）评判脊髓功能。记录术中不同时间点两组病人的生命体征和SEP和MEP的波幅和潜伏期,同时记录经颅电刺激时病人是否出现剧烈体动和自主呼吸。比较两组病人术毕后麻醉苏醒时间和质量。结果 两组病人不同时间点的生命体征差异无统计学意义。两组病人的SEP的波幅和潜伏期差异无统计学意义,MEP的潜伏期差异无统计学意义,MEP的波幅差异有显著性统计学意义。两组病人在电刺激时均无自主呼吸和剧烈体动发生。结论 术中不使用肌松药的全静脉麻醉方案可安全有效地用于行神经电生理监测的脊柱手术,并且在电生理监测信号质量和术后苏醒方面具有明显优势。     

Prediction of motor function by magnetic brain stimulation in patients with intracerebral hematoma.

Corticospinal motor pathways were monitored with motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation in 13 patients with radiologically confirmed hypertensive intracerebral hemorrhage and varying degrees of hemiparesis. The electromyographic responses of the thenar muscles were recorded. The motor weakness of the upper extremity was assessed at initial monitoring and 3 months after hemorrhage, and correlated with changes in MEP. Absence of MEP in the acute stage indicated poor recovery of muscle strength. No false negative results were seen in our series. The presence of MEP in a completely hemiplegic patient predicted some recovery of motor function. The suppression of amplitude was more accurate than prolongation of latency in predicting the functional recovery. MEP monitoring of patients with hypertensive intracerebral hemorrhage in the acute stage can predict the outcome of motor function.     

Nonpyramidal motor activation produced by stimulation of the cerebellum, direct or transcranial: a cerebellar evoked potential

There is a need to monitor the functional status of the motor pathways well enough to predict the state of that function during operations and in injured or diseased patients. We previously reported that a motor evoked potential (MEP) can be produced by direct or transcranial stimulation of the motor cortex in both cats and humans. This signal descends through both the dorsolateral and ventral spinal cord and is primarily localized in the pyramidal tracts, producing a peripheral nerve signal and an electromyogram (EMG) response. It is more sensitive to injury than the somatosensory evoked potential (SEP). We report here that one can stimulate the cerebellar cortex, either directly or transcranially, and produce a descending signal in the spinal cord that has different characteristics from the MEP. The cerebellar evoked potential (CEP), located in the dorsolateral and the ventral cord, has an earlier latency and a faster conduction velocity than the MEP. It is predominantly ipsilateral with some contralateral components and also produces EMG responses. In the peripheral nerves, the CEP often produces a pattern of several waves that is different from the one or two predominant contralateral waves of the MEP. The CEP is not diminished by pyramidotomy. It arises from two sites on the cerebellar cortex, medial and lateral. The pathways activated may be the vestibulospinal, rubrospinal, reticulospinal, and fastigiospinal systems. This test seems to offer a monitor of selected motor pathways in the spinal cord largely separate from and complementary to the MEP. The ventral pathways activated probably include those demonstrated to be most essential to basic ambulation after spinal cord injury in primates. Also of importance, one type of evoked potential can facilitate another, which provides additional diagnostic tests. The CEP should be of investigative and clinical value.     

Usefulness and Pitfalls of Intraoperative Spinal Motor Evoked Potential Recording by Direct Cortical Electrical Stimulation

Summary ? Objective. The aim of this study is to investigate the usefulness and problems with spinal motor evoked potential (MEP) recording, especially the reasons for failed recording. We report our personal experience over the last 8 years in patients with lesions adjacent to the primary motor cortex. Methods. MEP records of 50 consecutive patients were retrospectively reviewed. MEP was recorded by a catheter electrode inserted in the cervical epidural space. Stimulation electrodes were placed on the cortical surface during surgery. SEP recording was also performed in 29 of 50 patients. Results. MEP was obtained in 40 cases, and SEP was recorded in all 29 cases. The central sulcus was identified in 93% of patients in whom both MEP and SEP were performed, whereas in only 86% of patients who underwent only MEP. The main reason for MEP failure were inadequate exposure of the motor cortex, pre-existing hemiparesis and technical errors. Postoperative deterioration of motor function was closely related to intra-operative MEP changes. Conclusion. MEP is a useful tool to determine the motor cortex and to predict postoperative motor function. However, precise pre-operative craniotomy planning and combination with intra-operative SEP is essential to reduce the MEP failure.     

Evaluation of post-traumatic coma using evoked potentials

In 130 cases of post-traumatic coma a study of multimodality evoked potentials (MEP) was carried out shortly after the traumatism (within 72 h). According to the morphology of the records they were classified in grades (I-IV) in agreement with Greenberg et al. The worst grade of EP in the different types was related to the outcome at 6 months, distinguishing between focal lesions and diffuse lesions. Only a group (22.9%) of the 109 patients in which the auditory brain-stem evoked potentials (ABEP) could be studied, showed severe disorders (grade III-IV). There was a significant correlation between the ABEP grades and the outcome in the focal lesions (p less than 0.001). In the diffuse lesions the ABEP grades did not show significant differences with the outcome. A 22.4% of the patients with diffuse lesions had some visual evoked potentials (VEP) in grades III-IV against almost the double (41.6%) in the focal lesions. The grades of the VEP in the focal lesions did not have differences with outcome and in the diffuse lesions they did (p less than 0.05). Approximately half of the cases with focal lesions and one third of the diffuse lesions showed severe disorders (grades III-IV) of the somatosensory evoked potentials (SEP). In the two types of lesions there were significant differences with the outcome (p less than 0.001) and (p less than 0.01). The multimodality evoked potentials (MEP) are useful for predicting the outcome, especially in the patients where the neurological examination is impossible. Among the different modalities, the SEP were shown to be more predictive.(ABSTRACT TRUNCATED AT 250 WORDS)