脑干听觉诱发电位在脑干肿瘤手术中的监护

用双耳刺激、双侧记录的脑干听觉诱发电位(简称bBAEP)对16例脑干肿瘤进行术中监护。发现所有病人在手术操作时,均出现bBAEP改变,按其改变程度大致可分为轻、中、重三种改变。认为bBAEP更适用于手术中监护;bBAEP改变程度能反映脑干功能受影响程度;术中bBAEP监护有助于提高手术效果,且能预测预后;Ⅲ波和(或)Ⅴ波的潜伏期(PL),Ⅰ～Ⅲ、Ⅰ～Ⅴ、Ⅲ～Ⅴ的峰间潜伏期(IPL)延长超过1.5ms,或者全部波形消失,是脑干功能受到不可逆损害的具体指标。     

The effects of a supratentorial mass lesion on brain-stem auditory evoked potentials and short latency somatosensory evoked potentials

Nineteen patients with unilateral supratentorial mass lesion and without any evident clinical signs of transtentorial herniation were studied with Computed Tomography (CT), brain-stem evoked potentials (BAEPs) and central conduction time (CCT) of short latency somatosensory evoked potentials (SEPs). Sixteen had tumours, two had intracranial haematoma and one had chronic subdural haematoma. CT detected the initial signs of transtentorial herniation in every case. Preoperative I-V interpeak latency (IPL) was significantly (M+2SD) prolonged in 26% of cases on the lesion side and in 21% of cases on the opposite side. The mean I-V IPL was significantly prolonged both on the lesion side and the opposite side (P < 0.01, P < 0.02, respectively). Suppression of Wave V (M-2SD) was seen only in two cases, however, the mean amplitude of Wave V was significantly decreased both on the lesion side and on the opposite side (P < 0.001, P < 0.01, respectively). CCT of SEPs was significantly (M+2SD) prolonged in 33% of cases on the lesion side and in only 13% on the opposite side. The mean CCT was, however, significantly prolonged both on the lesion and on the opposite side (P < 0.001, P < 0.02, respectively). Postoperative I-V IPL was significantly prolonged in only 11% of cases while the mean I-V IPL was still significantly prolonged (P < 0.07) and the mean amplitude of Wave V was still suppressed (P < 0.001) on the lesion side. On the other hand, there was neither abnormality of I-V IPL nor suppression of Wave V on the opposite side. Postoperative CCT was significantly prolonged in 43% of cases and the mean CCT was also significantly (P < 0.01) prolonged on the lesion side. However, there was no prolongation of CCT on the opposite side. Preoperative findings of both BAEPs and SEPs show the abnormality due to the supratentorial lesion and postoperative findings of these potentials indicate both the effects of surgical decompression and the residual abnormalities due to the supratentorial mass lesion.     

Brain-stem auditory evoked potentials in adults with Down's syndrome.

Brain-stem auditory evoked potentials (BAEPs) were examined in 37 adult patients with Down's syndrome and in 37 age-matched normal subjects. All absolute and interpeak latencies except for the interpeak latency IV-V were shorter in patients than in normal subjects. The amplitude of wave V and the amplitude ratio V/I were smaller in patients than in normal subjects. Short latencies in patients were considered to be due to the smaller size of the brain-stem or to faster conduction velocity. The prolonged interpeak latency IV-V and the smaller wave V may indicate physiological dysfunctions between the upper pons and the lower midbrain.     

The clinical significance of the P15 wave of the somatosensory evoked potential in tentorial herniation

Somatosensory evoked potentials (SEPs) to median nerve stimulation and auditory brainstem evoked potentials (BAEPs) were recorded in 16 comatose patients who had suffered transtentorial herniation (TH) due to intracranial haematoma, hydrocephalus or tumour. An attempt was made to correlate the changes in the N14-P15 component of the central conduction time (CCT) and the I-V interpeak latencies (IPLs) of the BAEP with the clinical severity of TH. The N14-P15 component was not affected in seven patients at the diencephalic or early third-nerve stage, and six of these seven showed normal I-V IPLs. All six patients at the late third-nervel midbrain stage or worse, however, showed abnormalities in the N14-P15 components. Interestingly, five patients showed dissociation of SEP and BAEP abnormalities suggesting a differential sensitivity of the medial and lateral lemnisci in the brainstem to ischaemia and/or compression. All five patients in whom the P15 potential was absent on either side had a poor outcome and there was a correlation between the electrical failure in the N14-P15 component and the degree of brainstem damage caused by TH as assessed clinically. Reversible loss of the P15 potential by brainstem retraction has been shown in intraoperative SEP monitoring during aneurysm surgery. Prolonged compression of the upper brainstem seems to cause irreversible loss of the P15 which should be regarded as being due to irrecoverable brainstem dysfunction.     

The clinical significance of the P15 wave of the somatosensory evoked potential in tentorial herniation

Somatosensory evoked potentials (SEPs) to median nerve stimulation and auditory brainstem evoked potentials (BAEPs) were recorded in 16 comatose patients who had suffered transtentorial herniation (TH) due to intracranial haematoma, hydrocephalus or tumour. An attempt was made to correlate the changes in the N14-P15 component of the central conduction time (CCT) and the I-V interpeak latencies (IPLs) of the BAEP with the clinical severity of TH. The N14-P15 component was not affected in seven patients at the diencephalic or early third-nerve stage, and six of these seven showed normal I-V IPLs. All six patients at the late third-nerve/midbrain stage or worse, however, showed abnormalities in the N14-P15 components. Interestingly, five patients showed dissociation of SEP and BAEP abnormalities suggesting a differential sensitivity of the medial and lateral lemnisci in the brainstem to ischaemia and/or compression. All five patients in whom the P15 potential was absent on either side had a poor outcome and there was a correlation between the electrical failure in the N14-P15 component and the degree of brainstem damage caused by TH as assessed clinically. Reversible loss of the P15 potential by brainstem retraction has been shown in intraoperative SEP monitoring during aneurysm surgery. Prolonged compression of the upper brainstem seems to cause irreversible loss of the P15 which should be regarded as being due to irrecoverable brainstem dysfunction.     

Age-related latency changes in the brain-stem auditory evoked potentials

The effects of age on the brain-stem auditory evoked potentials were studied on 156 healthy subjects with ages ranging from 18 to 76 years. The latencies of peaks I-VII and the interpeak latencies of I-III, III-V and I-V were consistently shorter for the female group than the male group. The females also had higher peak amplitude than the males. The effects of sex on the peak and interpeak latencies were observed in all age groups. There was a small progressive prolongation in the peak latency with increasing age, particularly peak V. Although a correlation between the age and the I-III interval was not observed, there was also a small increase with age in the interpeak latencies of III-V and I-V.     

Chronic effects of phenytoin on brain-stem auditory evoked potentials in man.

The effects of phenytoin (PHT) on brain-stem auditory evoked potentials (BAEPs) were studied in 65 epileptic patients who received long-term PHT monotherapy at therapeutic and supra-therapeutic levels with no clinical evidence of brain-stem toxicity. Abnormal BAEPs were found in 7.5% and 33.3% of patients with therapeutic and supra-therapeutic PHT levels respectively. Serum PHT levels had a trend towards a positive relationship with the I-V interpeak latency (IPL), and a significant negative relationship with the amplitudes of waves I and V. At supra-therapeutic levels, both I-V and I-III IPLs were significantly prolonged while at therapeutic levels only I-III IPLs were prolonged. The absolute latency of wave I was prolonged in both the therapeutic and the supra-therapeutic groups. These results suggest that PHT acts both peripherally on either the auditory nerve or the cochlea, and centrally on brain-stem conduction.     

Central somatosensory conduction time and acoustic brainstem transmission time in post-traumatic coma

Short-latency evoked potentials (SEPs) of the scalp and neck after median nerve stimulation and acoustic brainstem evoked potentials (BAEPs) were recorded in 85 patients in post-traumatic coma with clinical signs of brainstem impairment between days 2 and 6 after trauma. The central somatosensory conduction time (CCT), the amplitude ratio (AR) N20:N13, the interpeak latencies (IPL) I-III, III-V, I-V, and the ARs between waves I and V (I:V) and between wave I and the wave IV/V complex (I:IV/V) were calculated and related to the outcome of the patients. In cases of coma due to supratentorial lesions, CCT and ARs of SEPs were close to normal in patients with good outcome: CCT increased and ARs decreased with worsening of outcome. In cases of primary brainstem injury, a significant prolongation of CCT was also seen in patients with good recovery, whereas normal CCTs could be found in patients with severe disability and death outcome. In this case, unilateral absent scalp SEPs were frequently found. The IPLs I-III, III-V, I-V, and the ARs of BAEPs increased with worsening of outcome. Significant differences of IPL I-V and III-V (brainstem transmission time) were seen between patients with good recovery or moderate disability outcome and the patients with severe disability or death outcome. There was no difference in BAEPs between patients with primary brainstem lesion and patients with secondary brainstem lesion. Patients with bilateral absent SEPs and bilateral absent BAEPs not related to traumatic or preexisting hearing disorders died or survived severely disabled. Unilateral absence of scalp SEPs and unilateral absence of BAEPs were frequently found in patients who died or who had severe disability. Asymmetries in scalp SEPs appeared to be distributed equally to all outcome categories, but asymmetries in BAEPs increased with worsening of outcome too. In most of the patients who died or survived disabled, both SEPs and BAEPs were abnormal.     

Effects of hypothermia on brainstem auditory evoked potentials in humans

Ten adult patients who underwent open heart surgery under induced hypothermia had brainstem auditory evoked potentials (BAEPs) recorded at 1 degree- to 2 degrees C-steps as body temperature was lowered from 36 degrees C to 20 degrees C to determine temperature-dependent changes. Hypothermia produced increased latencies of BAEP waves I, III, and V; the prolongation was more severe for the later components with the result that interpeak latencies I-III, III-V, and I-V were also prolonged. The temperature-latency relationship was nonlinear and best expressed by exponential curve. The latencies of waves I, III, V and the interpeak latency I-V increased roughly 7% for each 1 degree C drop; they doubled at a temperature around 26 degrees C. The amplitude of the BAEP components had a quasiparabolic relationship to temperature; the amplitude rose with hypothermia to 28 degrees or 27 degrees C, but decreased linearly with further cooling. All BAEP components were present at temperatures above 23 degrees C and absent below 20 degrees C. With rewarming, the changes reversed and BAEPs returned to initial prehypothermia status.     

Magnetic resonance imaging and brain-stem auditory evoked potentials in neuro-Behcet's disease

We studied central nervous system lesions in patients with neuro-Behcet's disease using magnetic resonance imaging (MRI) of the brain and recording of brain-stem auditory evoked potentials (BAEPs). MRI revealed abnormal findings in seven of eight patients. MRI studies demonstrated extensive regions with high intensity signal in the brain stem and/or basal ganglia on T2-weighted images obtained during the acute stage of the disease in three patients. One of these patients had a strongly gadolinum-enhanced round lesion in the lower pons. In four of the other five patients with chronic disease, brain-stem atrophy was observed on T1-weighted images. Atrophic changes were more severe in the brain stem than in the cerebellum. Abnormal BAEPs were observed in three patients and consisted of prolongation of interpeak latency of waves III-V and defects of wave III or V. Abnormal BAEPs were recorded in patients with severe inflammatory changes or progression of atrophic changes in the brain stem. Our findings show that MRI and BAEPs are useful in detecting the presence and assessing the degree of neurological involvement in patients with neuro-Behcet's disease.     

Diagnostic role of brain-stem auditory evoked potentials in neurobrucellosis.

Evoked potential audiometry and brain-stem auditory evoked potentials were evaluated in 15 patients with systemic brucellosis in whom brucella meningitis was suspected clinically. In 8 patients cerebrospinal fluid (CSF) was abnormal with high brucella titre, and evoked potentials were abnormal in all of them. In 7 patients the CSF was normal and evoked potentials were also normal. Brain-stem auditory evoked potential abnormalities were categorised into 4 types: (1) abnormal wave I, (2) abnormal wave V, both irreversible, (3) prolonged I-III interpeak latencies, and (4) prolonged I-V interpeak latencies, both reversible. These findings are of important diagnostic value and correlate well with the clinical features, aetiopathogenesis and final outcome.     

A prewarning sign for hearing loss by brainstem auditory evoked potentials during microvascular decompression surgery for hemifacial spasm

ObjectiveWe aimed to define the prewarning sign of brainstem auditory evoked potentials (BAEPs) associated with cerebellar retraction (CR) during microvascular decompression surgery for hemifacial spasm.MethodsA total of 241 patients with a latency prolongation of 1 ms or an amplitude decrement of 50% of wave V were analyzed. According to BAEPs before significant changes during CR, patients were classified into Groups A (latency prolongation of wave I [≥0.5 ms] without prolongation of the I–III interpeak interval [<0.5 ms]) and B (no latency prolongation of wave I [<0.5 ms] with prolongation of the I–III interpeak interval [≥0.5 ms]). BAEPs and postoperative hearing loss (HL) were compared between the two groups.ResultsGroup B comprised 160 (66.4%) patients. With maximal changes in wave V, latency prolongation (≥1 ms) with amplitude decrement (≥50%) was more common in Group B (p < 0.018). At the end of the operation, wave V loss was observed in 11 patients, including 10 patients from Group B. Five patients developed postoperative HL; all were from Group B.ConclusionsLatency prolongation of wave III during CR was associated with serious BAEPs changes and postoperative HL.SignificanceLatency prolongation of wave III is a significant prewarning sign.     

Brain stem auditory evoked potentials and chronic alcoholism

Brain-stem auditory evoked potentials (BAEPs) were obtained from 25 chronic alcoholic patients. The patients had been drinking heavily for an average of 15 years and a minimum of 5 years. All patients were totally abstinent for a minimum of 3 weeks. The morphology of waves were often altered. All presented prolonged I-III, III-V, inter-peak latencies (IPLs) and a loss of amplitude of wave V. The I-III, III-V and I-VIPLs were increased between 30 and 40 years, and III-V and I-VIPLs between 40 and 50 years. The incidence of abnormal BAEPs in patients with alcoholic epilepsy was not different from that of patients without a history of alcoholic seizures. Patients with clinical manifestations of alcoholic polyneuropathy had the highest incidence of abnormal BAEPs. BAEPs are more reliable in chronic alcoholic patients than EEG. The mechanisms of the increase in neural transmission time within the auditory brain-stem are discussed.     

The effect of click rate on latency and interpeak interval of the brain-stem auditory evoked potentials in children from birth to 6 years.

Latency and interpeak interval of the brain-stem auditory evoked potentials at different click rates were measured in 80 healthy children from birth to 6 years, and 21 adults. Clicks were presented at 10, 30, 50, 70 and 90/sec, and 70, 40 and 20 dB HL. At high stimulus intensity (70 dB SL), all latencies of waves I, III and V and the I-V, I-III and III-V intervals showed a progressive prolongation with increasing repetition rate. The latency- and the interval-rate functions were similar for all age groups but their slopes were slightly steeper in younger than in older. As click rate increased from 10/sec to 90/sec, the latencies of waves I, III and V at different age groups were prolonged by 4-10%, 9-13% and 12-15% respectively, and the intervals of I-V, I-III and III-V were prolonged by 15-16%, 8-16% and 14-24% respectively. The mean increments of wave V latency and I-V interval in different age groups were 0.404-0.575 and 0.332-0.526 msec respectively with increasing click rate from 10 to 50/sec, and 0.697-1.009 and 0.629-0.776 msec respectively with increasing click rate from 10 to 90/sec. The younger the age the larger the absolute increments for all these BAEP parameters, but the increasing rates for a BAEP measure were similar among different age groups, exhibiting no age-dependent differences.(ABSTRACT TRUNCATED AT 250 WORDS)     

Multimodality evoked potentials in progression of metachromatic leukodystrophy

A 2-yr-3-mo-old girl with metachromatic leukodystrophy (MLD) was examined using serial multiple electrophysiological procedures. Sensory nerve conduction velocity was delayed earlier and more severely than motor nerve conduction velocity. Visual evoked potentials (VEPs) showed prolonged latency of wave IV. Auditory brainstem responses (ABRs) showed prolonged latency of waves I and V, and the I-V interval. As to the interpeak latency of somatosensory evoked potentials (SEPs), the P9-P14 and the P14-N20 intervals were prolonged on admission. Two months later, both intervals were more prolonged, but the prolongation of the P9-P14 interval was the most prominent. The demyelination in our case may have started in the cerebral white matter, progressed to the peripheral nerves, and at last via the spinal root reached the brainstem. An electrophysiological follow-up study may be valuable in the understanding of the progressive pathological changes and in the evaluation of therapeutic measures.     

Brain-stem auditory evoked responses to hypercarbia in preterm infants

To determine the effect of acute hypercarbia on brain-stem function in preterm neonates, we compared brain-stem auditory evoked responses (BAERs) during 8% CO₂ breathing to those elicited during room air breathing in 12 healthy preterm infants during the first week of life. End-tidal CO₂ (ETpCO₂), respiratory rate and depth were monitored throughout the protocol. Absolute wave latencies and interpeak intervals of the BAERs were ana;yzed from duplicate trials. During 8% CO₂ breathing, ETpCO₂, respiratory rate depth of respiration increased significantly (p < 0.05). The absolute latency of wave V was prolonged (P < 0.025). Values of absolute peak latencies I and III were unaffected by the hypercarbic state. These data demonstrate that elevations in pCO₂ which elicit ventilatory responses also effect the BAER. The specific effects on ventilatory pattern, peak V latency and interpeak interval III–V indicate brain-stem responsiveness and alterations in the more central components of the auditory pathway. These findings raise important considerations regarding the influence of hypercarbia on brain-stem function preterm infants and the clinical management of such infants with abnormalities of gas exchange.     

Effects of carbamazepine and valproate on brainstem auditory evoked potentials in epileptic children

Brainstem auditory evoked potentials (BAEPs) were recorded in 18 epileptic children receiving carbamazepine and 10 epileptic children receiving valproate. BAEPs were recorded before the administration of antiepileptic drugs (AEDs) and 13 months later during which the children received AEDs. Statistical analysis of peak latencies and interpeak intervals of waves I–III–V were made. Carbamazepine treatment resulted in prolongation of peak latencies of waves I–III–V and interpeak intervals I–III and I–V. Valproate monotherapy, on the other hand, caused no consistent changes on BAEP. On the basis of these results we suggest that chronic carbamazepine therapy exerts a suppressive influence on the auditory pathways, both peripherally at the level of the cochlea and/or auditory nerve, and centrally at the brainstem.     

Prognostic evaluation of severe brain damage by auditory brainstem evoked potentials (BAEPs)

Auditory brainstem evoked potentials (BAEPs) reflect activities of the brainstem auditory pathway and the influence of activities of structures surrounding the pathway. It is said that BAEPs are reliable in predicting the outcome of patients with severe brain damage. The author studied the relationship between initial BAEP findings, particularly interpeak latencies of waves I to V and waves III to V, and mortality as based on the cause of each disorder. BAEPs were sequentially recorded in 241 cases of various neurological diseases resulting in severe brain damage (GCS less than 8) during the first few days after onset. BAEPs were graded into four groups based on initial findings. Group A: all waves I to V were recorded (159 cases). Group B: waves IV & V absent (11 cases). Group C: either wave I or waves I & II only were recorded (28 cases), Group D: all waves absent. Prognosis in Group B & C was poor, only two patients surviving in a vegetative state. There were no survivors in Group D. The relationship in Group A between interpeak latencies (I-V ipl, III-V ipl) and prognosis is discussed. This group consisted of 41 cases subarachnoid hemorrhage, 29 cases hypertensive intracerebral hemorrhage, 5 cases severe cerebral infarction, 21 cases infratentorial cerebral vascular disease, 49 cases supratentorial severe head injury, and 14 cases infratentorial head injury. In deceased cases of subarachnoid hemorrhage and supratentorial head injury, there was significant prolongation of I-V ipl and III-V ipl over the mean latency of 20 normal subjects plus 2SD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Peroxisomal bifunctional enzyme deficiency: serial neurophysiological examinations of a case

We report on a case of 21-month-old girl with peroxisomal bifunctional enzyme deficiency, which was diagnosed by means of complementation analysis. Serial neurophysiological examinations were also carried out. The motor and sensory nerve conduction velocities of the median nerve showed lower borderline values at 3 months of age and were within normal range at 11 months of age. Later, those velocities had gradually decreased. The electrically elicited blink reflex at 3 months of age showed the prolongation of latencies of R1, R2 and R2′ and the interpeak latencies of R1, R2 and R1 -R2′. Furthermore, RI, R2 and R2′ showed prolonged latencies at 11 months of age and were absent at 15 months of age. The auditory brainstem response (ABR) showed, bilaterally, normal latency of wave I, prolonged interpeak latencies of waves I–V. At 11 months of age, waves III and IV–V of ABR were detected, but their amplitude was very low. At the age of 15 months ABR was absent. These results and the following report are valuable for understanding the pathogenesis of neurological symptoms.     

Brain-stem auditory evoked potentials in different types of hepatic diseases

Brain-stem auditory evoked potentials (BAEPs) were studied in 69 patients with different types of hepatic diseases. BAEPs were normal in viral hepatitis, but the peak V and interpeak I-V latencies were prolonged in liver cirrhosis. Prolongation in peaks III, IV and V and interpeaks I-III, III-V and I-V were observed in both alcoholic liver disease and Wilson's disease with the latter more severely affected. The present data indicate that BAEPs may be used to study the effect of various hepatic diseases on the CNS.