Brain-stem monitoring. II. Preterminal BAEP changes observed until brain death in deeply comatose patients

Preterminal BAEP changes were studied until brain death in 8 head-injured patients out of a series of 38 comas monitored by means of a system allowing high-rate sequential recording. Two different modalities of BAEP degradation were disclosed: (1) simultaneous latency increase of all components associated with a decrease of cerebral perfusion pressure (CPP), consistent with ongoing ischaemia of the posterior fossa; (2) deterioration of brain-stem components (waves III-V) with preserved or even enhanced wave I. The latter pattern was not consistently associated with any haemodynamic change and might be related to mechanical factors causing rostro-caudal deterioration of brain-stem function. The time course of BAEP degradation ranged from a few minutes to more than 10 h. In the case of slow preterminal evolution definitely pathological trends were identified even when individual BAEPs were still within normal limits. Such trends would have remained unnoticed in single BAEP records. Hypothermia and anaesthetic drugs were found to induce falsely alarming BAEP changes very similar to those seen during preterminal evolution. Our results suggest that continuous brain-stem monitoring could be helpful for management of comatose head-injured patients.     

Brain stem AEP in toxic comas. Correlation with brain stem reflexes

24 deep toxic comas with respiratory assistance were studied by brain-stem reflex and BAEP. Laboratory analysis showed several simultaneous toxics (phenobarbital, benzodiazepines, tricyclic antidepressants...). Three groups of patients were defined: Twelve patients with normal BAEP and with relatively preserved brain-stem reflex (oculocephalic and oculovestibular are often disturbed but photomotor is present). Eleven patients with delayed BAEP and with more disturbed brain-stem reflex (photomotor is missing 3 times). In 2 cases (one of which is mentioned above in group B) brain-stem reflex and BAEP disappear and these patients die. Cerebral anoxia is associated here with toxics. Causes of delayed latencies (group B) are discussed (hypothermia, toxics). BAEP seems important in diagnosis and prognosis of toxic coma.     

Emergence of the brain-stem auditory evoked potential in the premature lamb.

Brain-stem auditory evoked potentials (BAEPs) were elicited by bone conducted stimuli in the very immature lamb following delivery, wherein liquid ventilation techniques were utilized to control cardiopulmonary and acid-base conditions, independent of umbilical-placenta support. Unlike previous studies of the in utero fetal lamb in which the BAEP could not be elicited by earphone delivered stimuli until 117 days gestation, our results demonstrate that the BAEP emerges at least as early as 106 days gestation in the lamb and consists of a full complement of readily discernible and reproducible wave forms. In addition, the results demonstrate substantial maturation of the BAEP from 106 to 122 days gestation during which time there is a significant decrease in absolute and interpeak latencies with an increase in developmental age. It is concluded that the ability to elicit the BAEP utilizing bone conduction at this early stage of gestation is related to improved stimuli delivery. Furthermore, this study demonstrates the feasibility and flexibility afforded by liquid ventilation and bone conduction BAEP techniques to study brain-stem function at particularly vulnerable stages of development.     

Absence of rate-dependent BAEP P5 latency changes in patients with definite multiple sclerosis: possible physiological mechanisms

Brain-stem auditory evoked potential (BAEP) rate studies have been incorporated into evoked potential protocols in an attempt to identify demyelinating lesions. A group of 9 patients with clinically definite MS are described who showed abnormal BAEP P1-P5 interwave latencies at slow repetition rates and failed to demonstrate a significant enhancement of this abnormality following rapid click presentation rates. The lack of rate-dependent P5 latency changes has been hypothesized to represent a less severe form of axonal demyelination. Thus, it may be possible to subclassify or subgroup patients with evidence of brain-stem demyelination based on the presence or absence of BAEP rate-dependent abnormalities.     

Clinical correlates of brain-stem auditory evoked potential variables in multiple sclerosis. Relation to click polarity.

The correlations between clinical signs and BAEP latency, amplitude and dispersion variables were investigated in 98 multiple sclerosis patients. A new dispersion variable, the wave IV-V "shape ratio" (SR IV-V), correlated most strongly with brain-stem signs (i.e., nystagmus). Severely reduced wave IV-V amplitude was frequently found in patients with vertical nystagmus or internuclear ophthalmoplegia, and interpeak latency (IPL) III-V correlated most strongly with cerebellar dysfunction (i.e., ataxia). The results may reflect different localizing ability among the various BAEP variables. The association between ataxia and increased IPL III-V was significantly stronger for BAEP to C clicks than to R clicks. Patients with abnormal BAEPs to one polarity (C or R) but not to the other, had significantly more clinical dysfunction than patients with normal BAEPs to both C and R clicks. Hence, C vs. R discordance may be interpreted to indicate possible brain-stem dysfunction.     

Brain-stem auditory evoked potentials in children with brain-stem or cerebellar dysfunction

Brain-stem auditory evoked potentials (BAEPs) were recorded in 23 children who had signs of brain-stem or cerebellar dysfunction. In patients with brain-stem gliomas, BAEPs were abnormal in all except one, in whom involvement of the brain-stem auditory pathway was limited to the midbrain tectum. The BAEPs were normal in neuronal ceroid lipofuscinosis, but abnormal bilaterally in inheritable leukoencephalopathies. All patients with Leigh's encephalopathy had BAEP abnormalities; in two, abnormalities occurred before the appearance of lesions on computed tomographic scan. Patients with Friedreich's ataxia and giant axonal dystrophy had abnormal BAEPs, but the test was normal in a child with similar neurologic findings with vitamin E deficiency. Patients with diffuse metabolic encephalopathies had variable findings. Thus, BAEP abnormalities are nonspecific for various disease processes but are frequently seen in neoplastic and neurodegenerative diseases, with primary white matter or extensive brain-stem involvement.     

The prognostic value of intraoperative BAEP patterns in acoustic neurinoma surgery.

Based on a consecutive series of 70 hearing patients with unilateral acoustic neurinomas and intraoperative monitoring of brain-stem auditory evoked potentials (BAEP), 4 dynamic BAEP patterns could be characterized. These patterns correspond with early and late postoperative hearing outcome. All patients with stable wave V (pattern 1) showed definite hearing preservation, all patients with irreversible abrupt loss of BAEP (pattern 2) lost their hearing, despite early hearing preservation in two cases. All patients with irreversible progressive loss of either wave I or wave V (pattern 3) eventually suffered from definite postoperative hearing loss, despite early hearing preservation in two cases. Those cases with intraoperative reversible loss of BAEP (pattern 4) showed variable short and long term hearing outcome. In 34% hearing was preserved, 44% suffered from postoperative hearing loss, the remaining 22% showed postoperative hearing fluctuation, either as a delayed hearing loss or as reversible hearing loss. Postoperative hearing fluctuation indicates anatomical and functional preservation of the cochlear nerve during surgery and is suggestive of a pathophysiological mechanism initiated during the surgical procedure and continuing thereafter. Patients at risk for delayed hearing loss can be identified during surgery by a characteristic BAEP pattern and may benefit from vasoactive treatment.     

Auditory evoked potentials in anxiety disorder

The pathophysiology of anxiety has received much recent attention. EEG findings in anxiety are nonspecific, and some changes in psychophysiological measures have been reported. We recorded short-latency brainstem auditory evoked potentials (BAEPs) and long-latency auditory event-related potentials (AEPs) in 12 patients with generalized anxiety disorder. All 12 patients had BAEP latencies within clinical norms, but I-V interpeak latencies were significantly longer in patients with anxiety than controls. N1, N2, P2, and P3 AEP components were within normal limits; N1 and P2 were reduced in amplitude in anxiety patients, but differences from controls were not significant. The BAEP findings may suggest altered brain-stem function in anxiety, which has been implied by biochemical studies of anxiety and depression. AEP differences may be related to difficulties in concentration and attention direction reported by anxious patients.     

脑干听觉诱发电位在老年人椎基底动脉供血不足的诊断价值

目的 探讨脑干听觉诱发电位(BAEP)测定对诊断老年人椎基底动脉供血不足(VBI)的临床价值.方法 选择符合可临床确诊为VBI的60例老年患者为病例组,在眩晕症状发作期进行BAEP测定.并选择60例老年体检者为对照组.结果 病例组60例中有26例(43.3%)BAEP测定异常,BAEP测定异常病例中内耳型异常有10例(38.5%),8例表现为波I PL延长,2例表现为波I PL的ILD>0.4ms.脑干型异常16例(61.5%),10例表现为Ⅰ～Ⅲ IPL延长,2例为Ⅲ一Ⅴ的IPL延长和2例为Ⅰ-Ⅴ IPL的ILD>0.4ms等.对照组BAEP检查无异常.结论 BAEP检查为无创和客观测定,对老年人VBI的损伤部位(脑干或听神经通路)及损伤的程度都具有诊断意义,可作为老年人内耳型和脑干型病变定位的客观诊断指标.     

Brain-stem auditory evoked potentials and blink reflex in friedreich's ataxia

Summary The brain-stem involvement in Friedreich's ataxia (FA) was studied by using brain-stem auditory evoked potentials (BAEPs) and the blink reflex. Ten out of 18 patients had abnormal BAEPs, the main abnormality being complete absence of responses and disappearance of wave V. Combined degeneration of the peripheral and central acoustic pathways probably accounts for these findings. The blink reflex was abnormal in 50% of the cases. The outstanding abnormality was bilateral delay of late responses with normal early response, which could be correlated with the known pallor of the descending trigeminal tracts. In contrast with BAEP findings, blink reflex abnormalities did not correlate with either the age of patients or the severity and duration of the disease. These data suggest a difference in susceptibility to degeneration between the auditory system and neuronal system subserving the blink reflex. We conclude that systematic BAEP and blink reflex recording is useful in the electrophysiological evaluation of FA patients.     

犬腹部爆炸伤后早期SEP、MEP及BAEP的变化

目的 旨在从电生理角度了解腹部爆炸伤后早期脑的损伤情况。方法 建立犬腹部爆炸伤动物模型,对伤后24hSEP、MEP及BAEP的变化进行动态观察。结果 伤后3h SEP及MEP的潜伏期较伤前明显延长(P<0.01),且在伤后24h潜伏期延长更加明显,显著长于伤后3h(P<0.05)。BAEP除I波外各波潜伏期及峰间期于伤后12h显著延长(P<0.01),且持续发展至伤后24h。结论 腹部爆炸伤后,无论是感觉、运动还是脑干听觉通路皆受到了不同程度的损伤。     

Brain-stem auditory evoked potentials and brain death.

BAEP records were obtained from 30 brain-dead patients. Three BAEP patterns were observed: (1) no identifiable waves (73.34%), (2) an isolated bilateral wave I (16.66%), and (3) an isolated unilateral wave I (10%). When wave I was present, it was always significantly delayed. Significant augmentation of wave I amplitude was present bilaterally in one case and unilaterally in another. On the other hand, in serial records from 3 cases wave I latency tended to increase progressively until this component disappeared. During the same period, wave I amplitude fluctuations were observed. A significant negative correlation was found for wave I latency with heart rate and body temperature in 1 case. Two facts might explain the progressive delay and disappearance of wave I in brain-dead patients: a progressive hypoxic-ischaemic dysfunction of the cochlea and the eighth nerve plus hypothermia, often present in brain-dead patients. Then the incidence of wave I preservation reported by different authors in single BAEP records from brain-dead patients might depend on the moment at which the evoked potential study was done in relation to the onset of the clinical state. It is suggested that, although BAEPs provide an objective electrophysiological assessment of brain-stem function, essential for BD diagnosis, this technique could be of no value for this purpose when used in isolation.     

Brain-stem auditory evoked potential abnormalities with unilateral brain-stem lesions demonstrated by magnetic resonance imaging

We correlated the brain-stem auditory evoked potential (BAEP) abnormalities in 24 patients with discrete unilateral brain-stem lesions demonstrated by magnetic resonance imaging. In 18 patients who had BAEP abnormalities either confined to or more severe on stimulation of one ear, the lesion on magnetic resonance imaging was in the brain stem ipsilateral to the corresponding ear. Mesencephalic lesions produced amplitude abnormalities of the IV/V complex while pontine lesions resulted in abnormalities of earlier components (wave II and/or III). Prolongation of the I-III interpeak latency tended to occur with pontine lesions and of the III-V interpeak latency with mesencephalic lesions. Unilateral brain-stem lesions, particularly at the mesencephalic level, often produced BAEP abnormalities on both ipsilateral and contralateral monaural stimulation.     

Vertebral artery dominance,brainstem auditory evoked potential,and vertigo of vascular origin

Abstract

Objective: Vertebral artery dominance (VAD) is defined when there is a significant difference between the diameters of the vertebral arteries (VAs). VAD may be a risk factor for vertigo of vascular origin. The objectives of this study were: (1) to investigate changes of brainstem auditory evoked potential (BAEP) in patients with vertigo caused by VAD through magnetic resonance; and (2) to understand the possible mechanism(s) by which VAD triggers vertigo of vascular origin.

Methods: This prospective study involved 64 patients with vertigo, including 35 patients with VAD (VAD group) and 29 without VAD (non-VAD group) as detected by head magnetic resonance angiography. Age, sex, and other clinical histories were comparable in both groups. The degree of vertigo was graded and BAEP examination was performed in each patient. BAEP changes as well as their correlations of BAEP with the dominant VA and basilar artery (BA) were analyzed in both groups.

Results: The rate of abnormal BA shapes was 60% in the VAD group compared with 34·5% in the non-VAD group (Chi-square?=?4·135, P<0·05). The median BA curvature was higher in the VAD group than that in the non-VAD group, 3·67 and 1·73 mm, respectively (P<0·01). Peak latencies (I, III, and V) in the VAD group were longer than those in the non-VAD group (P<0·01), but the difference in the III did not reach statistical significance (t?=?1·916, P>0·05). Interpeak latencies (III–V and I–V) were longer in the VAD group than those in the non-VAD group (P<0·05); there was no significant difference in the interpeak latencies of I–III (P>0·05). The III–V/I–III ratios were higher in the VAD group than those in the non-VAD group. The vertigo severity level was significantly higher in the VAD group than that in the non-VAD group (3·2±1·0 versus 2·2±0·7). The vertigo severity level correlated with VAD and every major anomaly index of BAEP; its correlations with III–V/I–III were remarkably significant (r?=?0·617, P?=?0·013).

Conclusion: The incidence of abnormal BA shapes and abnormal BAEP, and the vertigo severity level were higher in VAD patients. Moreover, VAD was found to correlate with abnormal BAEP, suggesting that VAD contributed to vertigo of vascular origin.     

Evoked potentials in basilar artery thrombosis: correlation with clinical and angiographic findings

In 28 patients with vertebro-basilar or basilar artery thrombosis brain-stem auditory evoked potentials (BAEPs) and somatosensory evoked potentials (SEPs) have been recorded. Visual evoked potentials (VEPs) were recorded in 7 of these 28 patients. In 24 patients the diagnosis was angiographically proven and in 4 patients Doppler sonography and computerized tomography suggested this diagnosis. The BAEP and SEP findings were correlated to clinical and angiographical signs. BAEPs could be classified into 6 different patterns. In more than half of the patients different BAEP patterns from the two ears could be found. A pathological IV/V complex was most often found in comatose patients and in patients with a basilar artery occlusion distal to the anterior inferior cerebellar artery. Prolonged interpeak latency of I-III was mainly found in alert or drowsy patients with caudal occlusions. The frequent occurrence of a BAEP with only wave I preserved, or with no waves preserved, in patients with brain-stem functions suggests that BAEPs are not useful in the diagnosis of brain death when basilar artery thrombosis is suspected. SEPs were either absent bilaterally or else severely altered on one side in all comatose patients. In alert patients, including those with 'locked-in' syndrome, SEPs were never absent bilaterally. Increased N13-N20 interpeak latency was an uncommon finding in this series. There was no correlation between the SEP and the angiographically proven location of the occlusion. In the 'locked-in' syndrome both SEP and BAEP findings were non-uniform. Normal SEPs were sometimes found in combination with severely altered BAEPs, suggesting partial deafferentation. Since basilar artery thrombosis is now a treatable condition, early diagnosis and documentation of functional deficits moves into a more important clinical area than heretofore.     

Age-dependent amplitude variation of brain-stem auditory evoked potentials

Normative amplitude values of brain-stem auditory evoked potential (BAEP) components are given for normally hearing subjects at 1, 10, 30, 50 and 70 years of age, with an intragroup age variation of only +/- 6 months. Under these circumstances amplitude standard deviations decreased to less than 20% of the mean values. In contrast with the reduced evolution of latency with age, BAEP amplitude (for components I-V) undergoes a greater oscillation during ontogeny. With the exception of component I, it increased markedly from 1 year to 10 years of age and decreased thereafter constantly up to 50 years, with a mean rate of 10 nV yearly. The decrease slowed down between 50 and 70 years. The amplitude differences between the subgroups are highly significant statistically (P less than 0.01). Possible reasons for these changes are discussed.     

脑干听觉诱发电位对面肌痉挛微血管减压术中听力保护的应用

目的探讨面肌痉挛微血管减压（microvascular decompression,MVD）术中应用脑干听觉诱发电位（brain—stem auditory evoked potential,BAEP）监测,对减少术后听力损伤的应用价值。方法回顾性分析43例面肌痉挛患者术中BAEP波V波形的变化以及手术前后平均纯音听力阈值（pure tone average,PTA）的改变,经统计学分析得出术中V波潜伏期延长的警示阈值。结果MVD术中,在显露面神经和责任血管减压操作时,V波潜伏期延长最为显著。38例患者术后PTA增高小于20dB,V波潜伏期平均延长（0．60±0．43）ms。其余5例术后PTA增高大于20dB,V波潜伏期平均延长（1．07±0．35）聪。两组患者V波潜伏期延长时间存在差异（P〈0．05）。术中V波潜伏期延长大于0．6ms与患者术后听力损伤相关;术中V波潜伏期延长大于1．0ms与患者术后听力损伤密切相关。因此术中V波潜伏期延长警示闾值可设定为0．6ms和1．0ms。结论BAEP监护警示阈值有助于指导面肌痉挛MVD术操作,避免术中过度牵拉听神经,减少对其周围微循环的干扰,为术中保护听神经提供警示作用。     

Evaluation of electrophysiological neuromonitoring in the diagnosis of brain death: Part I. Brainstem auditory evoked potentials

Electrophysiological neuromonitoring of brainstem auditory evoked potentials (BAEP), short-latency somatosensory evoked potentials (SSEP) and compressed spectral array (CSA) EEG can provide precise and immediate information concerning functional integrity of the brain, brainstem and upper spinal cord of severely brain-damaged patients. We applied this neuromonitoring system in the cases of 154 severely brain-damaged patients in order to evaluate its reliability in the diagnosis of brain death. In particular, this study considers the relationships between BAEP and neurological findings, conventional EEG findings and factors affecting final BAEP findings. As a result, we evaluated the significance of BAEP in the diagnosis of brain death. A total of 109 brain-dead patients were divided into two groups: group A with 48 patients determined brain dead neurologically and by EEG prior to BAEP monitoring, and group B with 61 patients who had undergone automatic BAEP monitoring every 10 to 30 minutes before and/or after determination of clinical brain death. A third group, C, included 45 non brain-dead patients subjected to neuromonitoring, and served as a comparative group. Brain damage was caused by subarachnoid hemorrhage in 50 patients, intracerebral hemorrhage in 36, cerebral infarction in 8, head injury in 47, meningitis in 3, brain tumor in 3 and anoxia in 7. There were no significant differences in causes among the three groups (chi 2 = 20.3). The mean ages in the three groups were 50 (ages 10-91) in group A, 51 (14-86) in group B, and 50 (5-87) in group C. There were no significant differences in age distribution among the three group (chi = 25.0). The last BAEP findings of the 109 brain-dead patients indicated loss of all waves in 99 (91%), the presence of wave I in 9 (8%), and the presence of waves I and II in one patient (1%) (Table 1). Only three of the 45 group C non brain-dead patients indicated loss of all BAEP waves within one month after onset (Table 1). The one demonstrated loss of all BAEP waves 17 days after her accident, with recovery of waves I to V three months later. The temporal relationships in group B patients of the course of BAEP findings and the time of neurological brain death diagnosis are shown in Table 2 and Fig. 1. All but two of the 61 patients were followed up until final loss of BAEP waves (Fig. 1).(ABSTRACT TRUNCATED AT 400 WORDS)     

Transitory, spontaneously recovering, peripheral facial nerve palsy after vinorelbine administration

Abstract Childhood intrinsic brain-stem gliomas have a dismal prognosis. Different treatment strategies have been adopted over the years without changing the final outcome of this ominous disease. Due to this grim prognosis, experimental therapeutic designs are worthwhile. Vinorelbine is a semi-synthetic vinca alkaloid that has demonstrated a broad spectrum of activity both in in vitro and in vivo experimental systems. By adopting vinorelbine during and after focal radiotherapy in the last two years, we have tried to evocate its known synergistic effect in brain-stem tumour control. Vinorelbine was administered intravenously before, during and after radiotherapy on tumour bed for a total duration of 10 months. All the consecutive patients whose clinical and radiological features corresponded to the diagnosis of an intrinsic brain-stem tumour, i.e., diffuse pontine glioma, have been accrued to this treatment protocol since July 2002. A histological assessment was not required. All patients were treated during hospital stay or in the outpatient clinic at the Istituto Nazionale Tumori of Milan (n=12) and at the Pediatric Clinic of Policlinico in Catania (n=1). Two of the thirteen patients so far treated have developed multiple subsequent, and transitory, episodes of monolateral peripheral facial nerve palsy during vinorelbine administration. The palsy always completely and spontaneously resolved at a short interval—around 30 min—after the end of the drug infusion. Obvious tumour progression was excluded by means of MRI; therefore the drug was administered as scheduled until the end of the treatment. We describe possible neurological and oncological implications of this unusual side effect, until now not reported in any other series dealing with vinorelbine as adjuvant treatment.     

Brain-stem auditory evoked potentials in multiple sclerosis: the relation to VEP,SEP and CSF immunoglobulins

Summary One hundred patients with multiple sclerosis (MS) were analysed retrospectively with respect to investigations of brain-stem auditory evoked potentials (BAEP), pattern reversal visual evoked potentials (VEP), somatosensory evoked potentials (SEP), and cerebrospinal fluid immunoglobulins (CSF-IG). BAEP were abnormal in 42% of those with normal VEP and SEP examinations, and in 38% of patients with normal CSF-IG. The chance of obtaining at least one abnormal EP was lower in patients with normal CSF-IG than in patients with abnormal CSF. When a dispersion ratio was included in the criteria for BAEP abnormality, the sensitivity increased compared with conventional BAEP criteria. We recommend that BAEP should still be included in the EP test battery for patients with suspected MS.