Automated monitoring of brainstem auditory evoked potentials in the operating room

We monitored brainstem auditory evoked potentials in 112 patients undergoing retromastoid craniectomies for microvascular decompression. To provide information on latency changes as quickly as possible, we implemented a block averaging technique of data acquisition with automatic tracking of wave V latency, which is the most clinically useful information. A change in peak latency probably due to surgical manipulation was observed in 63% of the patients, and the change could be at least partially corrected by modification of surgical technique. Twenty percent ot the 89 patients who underwent preoperative and postoperative audiometric testing showed a postoperative hearing decrement. Some patients had large intraoperative increases in latency without suffering postoperative hearing deficits, and some incurred hearing deficits even though the intraoperative latency increases were relatively small. However, patients whose brainstem auditory evoked potentials were lost during surgery, even temporarily, were likely to have postoperative hearing decrements. Patients who had deficits tended to have slightly greater increases in latency than patients without deficits, but the difference in the mean increases ot the two groups was not statistically significant. Most of the deficits were small, and all resolved over time.     

Intraoperative monitoring of sensory evoked potentials may be neither a proven nor an indicated technique

Excluding specific neurosurgical indications for cortical localization or peripheral nerve surgery, the use of sensory evoked potentials as a monitor in the operating room should be controversial at this time. Whether appropriate or not, legal and medical forces have largely established the use of somatosensory evoked potential monitoring as a standard during procedures that threaten the integrity of the spinal cord. The author believes that such monitoring should not replace the use of a wake-up test during these procedures because of the recognized possible occurrence of false negative results (i.e., normal evoked potentials despite abnormal spinal cord function). Another apparent established practice is monitoring of brainstem auditory evoked potentials to recognize the onset of disturbance in the auditory system. It has not been established that other recommended evoked potential monitoring practices, such as somatosensory evoked potential monitoring for such purposes as recognizing cerebral ischemia, or brainstem auditory evoked potential monitoring for recognizing untoward medullary stimulation, are as good as or better for these purposes than currently recognized and simpler monitors.     

Monitoring of sensory evoked potentials is highly reliable and helpful in the operating room

Because short-latency evoked potentials are relatively resistant to anesthetic agents, they can be used to monitor neural pathways during surgical procedures. The use of median nerve somatosensory evoked potentials to localize the central sulcus is an established aid of indisputable value in neurosurgical procedures involving cortical incisions for resection of certain epileptic foci, vascular malformations, or neoplasms near the central area of the brain. Likewise, recording of intraoperative nerve action potentials is currently regarded as indispensable in management of the neuroma-incontinuity after peripheral nerve trauma, as this evoked potential monitoring technique provides the only reliable method of distinguishing between axonotmetic and neurotmetic lesions. Evoked potential monitoring has been of value during many other types of surgical procedures, including cerebral aneurysm clipping, carotid endarterectomy, aortic procedures, microvascular decompression for trigeminal neuralgia and hemifacial spasm, acoustic neuroma resection, and a variety of spinal procedures. A detailed review of the literature is presented on the use of evoked potential monitoring for one of the more common indications: scoliosis surgery. Many orthopedic surgeons use the wake-up test only if the somatosensory evoked potentials change during surgery. A detailed review of the few reported cases of false negative evoked potentials is presented. The dearth of convincing reports of such phenomena in the face of so many positive experiences should persuade even the skeptical that monitoring of evoked potentials is a highly reliable and helpful intraoperative tool.     

脑干听觉诱发电位和体感诱发电位对昏迷患者预后的判断

目的脑干听觉诱发电位(BAEP)和体感诱发电位(SEP)与昏迷患者预后密切相关,探讨BAEP和SEP判断昏迷患者脑功能状态的可行性和准确性。方法采用丹麦Dantec公司生产Neuromatic2000型肌电图诱发电位仪。检查ICU病房中36例昏迷患者的BAEP和SEP。BAEP分析III-V波,SEP分析P15、N20、P25波。检查结果分为正常和异常。预后分为好转和死亡。结果36例患者,BAEP正常12例,异常24例。SEP正常13例,异常23例。好转13例,死亡23例。当SEP异常时,死亡率明显高于SEP正常时。而同时伴有BAEP异常时,死亡率更高。14例患者SEP检查P15、N20、P25波均消失,12例死亡,病死率为86%。5例患者BAEP检查III-V波和SEP检查P15、N20、P25波均消失,全部死亡,病死率为100%。结论BAEP和SEP的正常与否与昏迷患者的预后有密切关系(P=0.011)。SEP异常是判定的主要根据。BAEP和SEP相结合,则可以提高判断的准确性。对昏迷患者进行动态的BAEP和SEP观察可提高判断的准确性。     

Eliminating diathermy-induced artifacts during intraoperative monitoring of somatosensory-evoked potentials: A hardware solution

Somatosensory-evoked potentials (SEPs) recorded intraoperatively are often contaminated by artifacts arising from unipolar diathermy. This increases variability in serial SEP recordings and decreases the reliability of SEPs for intraoperative monitoring. Rejection of single sweeps on the basis of a voltage criterion can only partially prevent the inclusion of sweeps containing artifacts. We describe a low-cost hardware system that will halt SEP acquisition automatically before diathermy becomes active. Activation of the diathermy switch will halt SEP acquisition by sending a digital inhibit signal to the evoked potential machine via a fiberoptic cable. A timer delays the activation of the diathermy until the last sweep has been completed. To allow the electroencephalographic amplifiers to recover from any overload condition resulting from the high-voltage/high-frequency input during diathermy, acquisition is resumed only after a user-selectable time interval. The system was evaluated in 50 patients. It effectively interrupted SEP acquisition each time diathermy was used. By eliminating diathermy noise from the averaged waveforms, the system will allow evoked potential monitoring even during periods of intensive use of diathermy.     

Intraoperative somatosensory evoked responses recorded during onset of the anterior spinal artery syndrome

Somatosensory evoked responses may be used during operations on the thoracic aorta to monitor spinal cord function. A patient is described in whom the evoked responses were well maintained for the first 20 minutes of aortic occlusion and briskly returned to baseline configuration after reestablishment of aortic flow. Nonetheless, the patient was left with paralysis of the lower extremities consistent with the diagnosis of anterior spinal artery syndrome.     

Electroencephalographic and evoked potential monitoring in the hyperbaric environment

The purpose of this study was to investigate brain bioelectrical activity during hyperbaric oxygenation by continuous and simultaneous monitoring of electroenccphalographic and bimodal (auditory, somatosensory) evoked potentials. Multivariable recordings (electroencephalogram, brainstem auditory evoked potentials, early somatosensory evoked potentials, heart rate, heart rate variability, and transcutaneous partial pressure of oxygen) were measured with a new technique in 12 healthy male volunteers 26 to 52 years old (mean ± SD, 35.9 ± 9.5 years). Recordings were obtained while the subjects breathed (1) air at normal atmospheric pressure, (2) 100% oxygen at normal atmospheric pressure, (3) air at 2 atm (10 meters sea water [msw]), and (4) 100% oxygen at 2 atm (10 msw). Spontaneous brain electrical activity, somatosensory evoked potentials, and heart rate variability were not significantly affected during hyperbaric oxygénation, whereas the heart rate showed a significant decrease (pairedt test,P < 0.05). Alterations in brainstem auditory evoked potentials were seen under hyperbaric conditions and did not reach statistical significance (increase of the I-V interpeak latency by pairedt test;P < 0.2). All subjects showed insignificant increases in dominant alpha frequency and decreases in delta frequency under hyperbaric situations.     

Inconsistencies in the correlation between loss of brain stem auditory evoked response waves and postoperative deafness

This case underscores the difficulty of predicting postoperative hearing status from brain stem auditory evoked response (BAER) monitoring when wave I is preserved and all later waves are lost. During an operation involving the base of the skull, sudden and irreversible loss of all BAER waves beyond wave I occurred unilaterally. Wave I was preserved, with reduced amplitude and minimal latency shift. There was no permanent postoperative hearing sensitivity loss or speech discrimination loss.     

Inconsistencies in the correlation between loss of brain stem auditory evoked response waves and postoperative deafness

This case underscores the difficulty of predicting postoperative hearing status from brain stem auditory evoked response (BAER) monitoring when wave I is preserved and all later waves are lost. During an operation involving the base of the skull, sudden and irreversible loss of all BAER waves beyond wave I occurred unilaterally. Wave I was preserved, with reduced amplitude and minimal latency shift. There was no permanent postoperative hearing sensitivity loss or speech discrimination loss.     

Usefulness of epidurally evoked cortical potential monitoring during cervicomedullary glioma surgery

This report describes a patient with an intramedullary ependymoma at the region of the cervicomedullary junction in whom there was an abolition of somatosensory evoked potentials following median nerve stimulation. During intraoperative monitoring of cortical potentials elicited by epidural cervical cord stimulation, the tumor was removed. Posterior epidural stimulation appeared to depolarize more ascending fibers than did stimulation of a single peripheral nerve. We recommend that, in cases of operations in this vital area, epidurally evoked cortical potentials be monitored intraoperatively.     

An algorithm for monitoring sensory evoked potentials

Brainstem auditory evoked potentials (BAEP) testing is used extensively to monitor auditory function during retromastoid craniectomies for microvascular decompression. The latency between BAEP peaks can change notably over a period of several seconds or minutes, a much shorter time than is necessary to acquire and analyze a conventionally averaged BAEP. This article describes a continuous monitoring algorithm that detects both large, rapid changes in waveform and slow changes in latency. A prestimulus control interval in the response data window provides a mechanism for evaluating the reliability of the response. The algorithm tracks the latency and amplitude of a selected peak, using several checks to avoid detecting the wrong peak. The tracking mechanism is simple yet effective and eliminates the need to suspend averaging for manual measurement of peak parameters. The peak latency and amplitude are displayed immediately. The algorithm indicates gross changes in the BAEP within 30 seconds and provides reliable data on latency trends. By increasing the frequency of acquiring new waveforms, the algorithm provides more immediate information for the surgeon.     

Somatosensory evoked potential,a prognostic tool for the recovery of motor function following malperfusion of the spinal cord: Studies in dogs

The potential usefulness of somatosensory evoked potential monitoring during aortic cross-clamping is slowly being realized. In addition, the protection of endangered spinal nervous tissue during aortic cross-clamping has not been sufficiently evaluated. To test the pharmacologic protective efficacy of various agents, we recorded spinal evoked somatosensory potentials (bipolar epidural catheter) in dogs under controlled conditions (N₂O/O₂-enflurane anesthesia) following clamping of the aorta for 1 hour. There were 5 groups of animals: those treated with different medications, such as prostaglandin E₁ (PGE₁), prostacyclin (PGI₂), superoxide dismutase (SOD), and PGE₁ plus SOD for pharmacologic protection during ischemia, and the controls. The time to recovery of evoked potentials during the reperfusion period was 36 minutes in the controls, 15.9 minutes in the SOD group (p<0.01), 12.5 minutes in the PGE₁ group (p<0.001), 10.8 minutes in the PGI₂ group (p<0.001), and 3.8 minutes in the combination group (p<0.001). In addition, treatment resulted in a better neurologic outcome on the seventh postoperative day when compared with the control group. While in the control group only 1 animal could walk (9%), 7 of 12 in the PGE₁ group (58%), 4 of 12 in the SOD group (33.8%), 8 of 12 in the PGI₂ group (66.7%), and all animals in the combination group (100%) could walk. We computed an exponential correlation that related the mean time of potential recovery during reperfusion with Tarlov scoring (grade 0= paraplegia; grade 1= paraplegia with little movements; grade 2= paraparesis; grade 3= paraparesis with some problems; grade 4= normal motor function) in the various groups. On the seventh postoperative dayr=0.97 and the regression equation was y=50.6×10^(–0.28x). The correlation reflects a close relationship between late postoperative outcome of motor function and early intraoperative regeneration of somatosensory potentials after declamping. We conclude that (1) spinal evoked potential can be used as a prognostic tool to indicate recovery of motor function of the lower extremities after aortic clamping, and (2) during aortic cross-clamping the endangered spinal cord can be protected by means of pharmacologic treatment.

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Abstrakt Erst in letzter Zeit wird die potentiele Bedeutung somatosensorischvozierter Potentiale zur Überwachung der Rückenmarksfunktion während der Aortenabklemmung erkannt. In diesem Zusammenhang ist die pharmakologische Protektion des ischämischen Rückenmarks während der Abklemmungphase noch nicht ausreichend untersucht worden. Um die protektive Effiziens unterschiedlicher Pharmaka. auf die Ischämietoleranz zu bestimmen wurden spinal-evozierte Potentiale (bipolarer Epiduralkatheter) bei Hunden unter kontrollierten Bedingungen (N₂O/O₂—Enflurannarkose) 1 Stunde nach der Aortenabklemmung abgeleitet. 5 Gruppen erhielten eine unterschiedliche protektive Medikation: (a) Prostaglandin E₁ (PGE₁), (b) Prostacyclin (PGI₂), (c) Superoxydismutase (SOD), (d) PGE₁ plus SOD und die Effekte mit einer Kontrollgruppe verglichen. Die Zeit bis zur Erholung des spinal-evozierten Potentials betrug in der Reperfusionsphase: (a) bei der Kontrollgruppe im Mittel 36 min, (b) nach PGE₁ Protektion im Mittel 12.5 min (p<0.001), (c) nach PGI₂-Protektion im Mittel 10.8 min (p<0.001), (d) nach SOD-Protektion im Mittel 15.9 min (p<0.01), (e) nach der kombinerten Gabe von PGE₁ plus SOD im Mittel 3.8 min (p<0.001). Die jeweilige protektive Therapie war auch mit einem geringeren neurologischen Defizit am 7 postoperativen Tag im Vergleich zur Kontrolle vergesellschaftet. Nach PGE₁ konnten 7 von 12 Tiere laufen (58%) nach PGI₂ konnten 8 von 12 laufen (66.7%) nach SOD konnten 4 von 12 laufen (33.8%) und nach der Kombination PGE₁ plus SOD konnten alle Tiere am 7. postoperativen Tag laufen (100%). In der Kontrollgruppe konnte nur 1 Tier laufen (9%). Es bestand eine exponentielle Beziehung zwischen den mittlere Erholungszeiten des evozierten Potentials in den verschiedenen Gruppen und in der Motorischen Erholung Einteilung nach Tarlov: Grad 0= Paraplegie, Grad 1= Paraplegie mit eingeschränkter Bewegung, Grad 2= Paraparese, Grade 3= Paraparese mit motorischen Dysfunktionen, Grad 4= normale Motorik, Am 7. postoperativen Tag lag eine Korrelation von r=0.97 vor und die Regressionsgleichung betrug y=50.6×10^(–0.28x). Diese Korrelation weist auf eine enge Beziehung zwischen der zu erwartenden späten postoperativen Erholung der motorischen Funktion und der introperativen Erholung des somatosensorisch-evozierten Potentials in der Reperfusionsphase hin. Heraus ist abzuleiten: (1) Spinal evozierte können als prognostischer Indikator fur die Erholung der motorischen Funktion der untern Extremitäten nach Aortenabklemmung eingesetzt werden. (2) Während der Aortenabklemmphase kann das gefährdete Rückenmark mit Hilfe von Pharmaka geschützt werden.

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Resumen Objetivo. Lentamente se ha tomado conciencia de la potencial utilidad de los potenciales evocados somatosensoriales durante el pinzamiento aórtico. Además, no se ha evaluado suficientemente la protección del tejido neural espinal durante el pinzamiento aórtico. Para evaluar la eficacia protectora de varios agentes farmacológicos, registramos potenciales evocados somatosensoriales espinales (catéter epidural bipolar) en perros bajo condiciones controladas (anestesia enflurane y NO2/O2) siguiendo un pinzamiento aórtico de una hora de duración. Se estudiaron 5 grupos de animales, según el agente farmacológico usado para protección durante isquemia: 1. tratados con prostaglandina E1 (PGE1), 2. prostaciclina (PGI2), 3. superóxido dismutasa (SOD), 4. PGE1 más SOD, y 5. controles. El tiempo hasta la recuperación de los potenciales evocados durante el período de reperfusión fue 36 minutos en el grupo control, 15.9 minutos en el grupo SOD, (p<0.01), 12.5 minutos en el grupo PGE1 (p<0.001), 10.8 minutos en el grupo PGI2 (p<0.001), y 3.8 minutos en el grupo combinado (p<0.001). Además, el tratamiento resultó en mejor evolución neurológica al séptimo día al comparar con el grupo control. Mientras que en el grupo control sólo un animal pudo caminar (9%), 7 de 12 en el grupo PGE1 (58%), 4 de 12 en el grupo SOD (33.8%), 8 de 12 en el grupo PGI2 (66.7%), y todos los animales en el grupo combinado (100%) pudieron caminar. Computamos una correlación exponencial que relacionó el tiempo medio de potencial recuperación durante reperfusión con el puntaje de Tarlov (grado 0, paraplegia; grado 1, paraplegia con poco movimiento; grado 2, paraparesis; grado 3, paraparesis con algunos problemas; grado 4, función motora normal) en los varios grupos. En el séptimo día postoperatorio, r fue 0.97 y la evaluación de la regresión fue y=50.6×10^(–0.28). La correlación refleja una relación estrecha entre la evolución postoperatoria tardía de la función motora y la recuperación precoz de los potenciales evocados somatosensoriales durante el intraoperatorio.Conclusiones. 1. Los potenciales evocados espinales pueden ser usados como herramienta de pronóstico para indicar recuperación de la función motora de extremidades inferiores después de pinzamiento aórtico, y 2. La médula espinal amenazada puede ser protegida durante el pinzamiento aórtico mediante tratamiento farmacológico.

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Résumé L'utilité potentielle du monitorage des potentiels évoqués somato-sensitifs durant le clampage aortique est lentement en train de s'établir. De plus, la protection de la moelle épinière durant le clampage aortique n'a pas été suffisamment évaluée. Dans le but de tester l'efficacité de la protection apportée par divers agents pharmacologiques, nous avons enregistré les potentiels évoqués somato-sensitifs spinaux (à l'aide d'un cathéter épidural bipolaire) chez des chiens sous des conditions contrôlées (anesthésie par inhalation: mélange N₂O/O₂ et enflurane) suivant un clampage aortique de durée 1 heure, 5 groupes d'animaux ont été constitués: 4 groupes traités par divers médicaments tels que la prostaglandine E1 (PGE1), la prostacycline (PGI2), la superoxyde dismutase (SOD), et l'association PGE1 plus SOD, et un groupe contrôle. Les délais nécessaires `a la réapparition des potentiels évoqués durant la période de reperfusion ont été respectivement de 36 minutes dans le groupe contrôle, 15,9 minutes dans le groupe SOD (p<0,01), 12,5 minutes dans le groupe PGE1 (p<0,001), 10,8 minutes dans le groupe PGI2 (p<0,001), et 3,8 minutes dans le groupe de l'association PGE1 plus SOD (p<0,001). De plus, les traitements ont eu pour conséquence un mejlleur résultat neurologique au septième jour post-opératoire en comparaison avec le groupe contrôle. Alors que dans le groupe contrôle un seul animal était capable de marcher (9%), 7 sur 12 dans le groupe PGE1 (58%), 4 sur 12 dans le groupe SOD (33,8%), 8 sur 12 dans de groupe PGI2 (66,7%), et tous les animaux dans le groupe association PGE1 plus SOD l'ont été. Nous avons retrouvé une corrélation exponentielle dans les différents groupes entre le délai moye de réapparition des potentiels évoqués après reperfusion et le score de Tarlov (grade 0: paraplégie; grade 1: paraplégie avec petits mouvements; grade 2: paraparésie; grade 3: paraparésie modérée; grade 4: fonction motrice normale) apprécié au septième jour post-opératoire (r=0,97; équation de régression: y=50,6×10^(–0.28×). La corrélation reflète une relation étroite entre le degré de récupération de la fonction motrice en postopératoire tardif et la régénération peropératoire des potentiels évoqués somato-sensitifs après le déclampage. Nous concluons que (1) les potentiels évoqués spinaux peuvant être utilisés en tant qu'outil de prédiction du degré de récupération de la fonction motrice des membres inférieurs après clampage aortique, et (2) la moelle épinière menacée durant un clampage aortique peut être protégée par un traitement pharmacologique.

     

The prognostic value of somatosensory evoked potential monitoring and tumor data in supratentorial tumor removal

The aim of this study was to find appropriate somatosensory evoked potential (SSEP) and tumor data that would predict immediate postoperative outcome. Seventeen patients were evaluated, all with supratentorial mass lesions. Intraoperative SSEP monitoring was carried out, and central conduction time, N20 amplitude, and N20 to N13 amplitude ratio were recorded throughout the operation. The differences between the end and the start of the procedure and between the end of the operation and the most substantial changes during tumor removal were calculated for statistical evaluation. Tumor location and extent were carefully determined and calculated by computed tomographic reconstructions in the axial and sagittal planes. Several tumor parameters were measured: the distances from the midpoint of the tumor to the central sulcus, midline, and base of the skull and the longitudinal and cross-sectional diameters. The electrophysiologic and tumor data sets were correlated with the immediate postoperative neurologic deterioration. For this purpose, patients were divided into two groups: group 1 = no neurologic deterioration after operation (13 patients); group 2 = neurologic deterioration after operation (4 patients). The difference in central conduction times between the end and the start of the procedure was the only variable that exhibited a significant influence on the immediate postoperative condition (P = 0.007), as determined by analysis of variance. The other electrophysiologic data as well as the tumor data failed the significance threshold ofP = 0.05. Discriminant analysis was applied to test the classification capacity of the measured variables. Involving all measured variables (electrophysiologic and tumor data), discriminant analysis allowed a correct classification of all 17 patients to their proper neurologic deterioration group. Discriminant analysis for SSEP data alone led to 15 correct classifications. Tumor data, used alone for discriminating procedures, revealed 14 correct classifications. When each variable was analyzed separately, only the difference in central conduction times between the end and the start of the procedure gave significant predictions, namely, 15 correct classifications. This was the same number as achieved by all electrophysiologic variables together. No other variable could on its own yield any valid prognosis for assessment of immediate postoperative neurologic deterioration. The data confirm the importance of central conduction time recovery before the end of the operation on the patient’s immediate postoperative neurologic condition.     

脑干听觉诱发电位对糖尿病患者的应用

目的用相关性分析糖尿病（DM）患者脑干听觉诱发电位（BAEP与神经传导（NC）间的关系。方法回顾性分析接受BAEP和NC研究的患者,分为DM组43例和对照组43例,其中DM组再次分为4组包括神经病组,非神经组,梗死组和非梗死组,比较各组之间脑干听觉诱发电位峰间潜伏期I～Ⅲ波和I～V波等的差异。结果DM组和对照组之间比较,脑干听觉诱发电位峰间潜伏期I～Ⅲ波和I～V波差异有统计学意义,DM神经组IPLI～III（2．21±0．17）msvs（2．07±0．12）ms（P〈0．01）;DM梗死组IPL I～III（2．20士0．17）msvs（2．07±0．12）ms（P〈0．05）,DMIPLI～Ⅲ非梗死组（2．20±0．11）msvs（2．07±0．12）ms（P〈0．01）;DM神经组IPLI～V（4．16±0．21）msvs（4．02土0．10）ms（P〈0．05）。脑干听觉诱发电位的I～Ⅲ波峰间潜伏期与胫神经运动传导速度有相关性（r=-0．308,P〈0．05）。结论DM患者的I～Ⅲ波峰间潜伏期延长,特别在神经病亚组。这种延长现象可以由听神经损伤解释。DM患者,胫神经,正中神经感觉,腓肠神经神经传导速度与听觉神经病存在相关性。     

脑出血患者脑干听觉诱发电位与脑血流量相关性研究

目的：研究高血压脑出血患者脑干听觉诱发电位（ＢＡＥＰ）与脑血流量（ＣＢＦ）的相关性。方法：检测８３例高血压脑出血患者和７５例正常人的ＢＡＥＰ及用１３３Ｘｅ吸入法测定ＣＢＦ。结果：脑出血患者ＢＡＥＰ和ＣＢＦ异常率分别为６９．９％和６３．９％，病情愈重则异常率愈高，脑出血量大者ＢＡＥＰ和ＣＢＦ异常率高于出血量少者，Ｐ＜０．０５～０．０１。脑出血患者ＢＡＥＰ主波潜伏期和波间期均比正常对照组明显延长，Ｐ＜０．０５～０．０１；ＢＡＥＰ异常患者ＣＢＦ明显低于ＢＡＥＰ正常患者，Ｐ＜０．０５～０．０１。结论：ＢＡＥＰ是评估脑出血患者脑干功能和脑血流量的良好手段。     

Somatosensory evoked potentials are not a sensitive indicator of potential positioning injury in the prone patient

Objective. This study monitored somatosensory evoked potentials (SSEP) at the median and ulnar nerves in awake volunteers placed in a simulated position for prone surgery. Neurologic symptoms were used as a surrogate end-point for position related peripheral nerve injury; the occurrence of these symptoms was correlated with the presence or absence of SSEP changes in median and ulnar nerves.Methods. Median and ulnar nerve SSEP data was obtained from awake volunteers in the supine and prone positions. With the head midline in the prone position, SSEPs were measured as the arms were advanced in four cephalad increments. Symptoms, defined as tingling, numbness, or aching in the hand, forearm, or upper arm, were recorded at each position. SSEP changes were considered significant when amplitude decreased 60% and/or latency increased 10% compared with baseline prone measurements. Symptoms were correlated with SSEP changes using chi-squared analysis (p < 0.05), and Fisher's exact analysis (p < 0.07).Results. Data were collected on 14 patients, mean age 34 ± 3 years. Seven (50%) subjects reported symptoms with changes in position, while four (29%) subjects displayed SSEP changes. There was no statistically significant association between symptoms and SSEP changes. There were no false positives (no symptoms in the presence of significant SSEP changes), but there were 3 (21%) false negatives (positive symptoms without SSEP changes).Conclusions. While all SSEP changes were associated with symptoms, the development of symptoms in 3 of 7 patients without SSEP changes suggests that SSEPs may be an imperfect monitor for the detection of positioning injury. The limited sensitivity of SSEPs in this study may be due to the duration of the monitoring, sample size, or the validity of symptoms as a surrogate for nerve injury.     

脑干听觉诱发电位波幅比值和波峰潜伏期比值的生后变化

目的探讨脑干听觉诱发电位(BAEP)波幅比值和波峰潜伏期(PL)比值的生后变化,为建立理想的动物模型奠定理论基础。方法选用SD大鼠,雌雄不拘。对照组15只成年大鼠,实验组选用3窝(共32只)新生大鼠,1个月后断乳,雌雄分笼饲养,每窝新生鼠选用5只用于实验。计算机平均叠加技术颅表记录大鼠BAEP,实验组15只新生SD大鼠,于14～70d动态观察BAEP的波幅比值和PL比值的变化。结果生后14d首次引出的BAEP的I,II,III和IV波的PL明显长于成年大鼠值,生后20d实验组的III/I,III/II,IV/I和IV/IIPL比值(2.57±0.13,1.39±0.13,3.56±0.19,1.93±0.18)明显大于成年大鼠值(2.28±0.17,1.29±0.07,3.05±0.26,1.72±0.11,t=5.713,3.315,5.110,3.903,P<0.01);随鼠龄增长,各PL逐渐缩短至成年大鼠值,PL比值逐渐变小至成年大鼠值。生后14d,BAEP的I,II,III和IV波的波幅均明显低于成年大鼠值,生后1个月内随年龄增长而递增,并明显超过成年大鼠值,然后又逐渐回降至成年大鼠值;III/II和IV/II波幅比值随鼠龄增长也有先增后降的相似变化。但II/I和IV/IIIPL比值与III/I,IV/I和IV/III波幅比值无明显生后变化。结论大鼠BAEP部分波幅比值和PL比值有显著的生后变化。     

糖尿病脑干听觉诱发电位分析

目的探讨脑干听觉诱发电位(BAEP)对糖尿病患者脑干功能损害的评定价值。方法对30例临床诊断为2型糖尿病的患者进行BAEP检测,并与20例正常组进行对照分析。结果糖尿病患者BAEP的异常率为63.33%,并与其病程呈正相关,但与血糖浓度无相关性。其中Ⅲ、Ⅴ波潜伏期(PL),Ⅰ～Ⅲ、Ⅲ～Ⅴ、Ⅰ～Ⅴ峰间期(IPL)较正常组延长,Ⅲ、Ⅴ波波幅降低,均有显著性差异(P<0.05)。结论BAEP对糖尿病脑干亚临床功能异常的诊断有重要意义。     

聋哑儿童238例脑干听觉诱发电位特征分析

目的:探讨脑干听觉诱发电位(brainauditoryevokedpotential,BAEP)在早期诊断聋哑的意义。方法:使用英国OXFORD公司的034W11B-V4.0多媒体肌电/诱发电位仪对238例有听力和/或言语障碍的儿童进行BAEP检测。结果:有新生儿窒息史、早产等高危因素的25例,异常20/25,其中11/20属周围性损害。曾使用耳毒性药物8例,异常6/8。有聋哑家族史2例,异常1/2。不明原因203例,异常168/203。结论:BAEP运用于常规检测,对早期诊断聋哑,监测神经系统和听觉系统康复进程,协助评价治疗效果均具有重要意义。     

Bilateral measurement of bispectral index and mid-latency auditory evoked potentials in patients with unilateral brain lesions

Purpose

The impact of intracranial lesions on the results of bispectral index (BIS) and mid-latency auditory evoked potentials (MLAEP) remains unclear. We tested the hypothesis that MLAEP (latencies of wave Pa and wave Nb) obtained bilaterally from patients with unilateral brain lesions result in less bias than BIS values obtained from both sides.

Patients

Twenty patients with unilateral supratentorial lesions were included in the study.

Materials and Methods

Bispectral index and MLAEP were measured bilaterally using the BIS and AEP modules of the Monitor S/5 (GE, Helsinki, Finland). Significance of the difference in the number of patients with a clinically relevant bias (more than 10%) of BIS and MLAEP was calculated by Fisher exact test.

Results

Bispectral index was significantly in more patients different on the side of the lesion than latencies of wave Pa and Nb (18 patients for BIS, 1 patient for Pa, 3 patients for Nb, P < .0001). Mean bias was −18.8 ± 25.7 for BIS, 1.5 ± 3.4 milliseconds for wave Pa, and −1.5 ± 6.1 milliseconds for wave Nb (data given as mean ± SD).

Conclusions

Mid-latency auditory evoked potentials are less biased by intracranial lesions than BIS and seem to be superior to BIS for the monitoring of patients with intracranial lesions.