Abnormal Brainstem Auditory Evoked Potentials Research Articles

Reversible brainstem auditory evoked potential abnormalities in jaundiced Gunn rats given sulfonamide.

Neurologic and audiologic sequelae produced by bilirubin toxicity are preventable by appropriately timed therapeutic intervention. To understand the timing and reversibility of the neural dysfunction that follows exposure to bilirubin, we recorded brainstem auditory evoked potentials (BAEP) in the Gunn rat model of bilirubin encephalopathy. Abnormal BAEP occur in jaundiced Gunn rats after injection of sulfadimethoxine (sulfa) 100 mg/kg intraperitoneally, which displaces bilirubin from blood albumin binding sites and promotes the net transfer of bilirubin into brain tissue. Reversal of BAEP abnormalities with injection of human serum albumin (HSA) 2 g/kg intraperitoneally was studied in 17- to 20-d-old jaundiced Gunn rats. One animal from each of 14 litters was randomly assigned to one of the following treatment groups: 1) sulfa alone, 2) sulfa + HSA at 2 h, 3) sulfa + HSA at 8 h, or 4) saline alone. BAEP were recorded in each rat before and 0.1, 4, 8, 24, and 48 h after injection of sulfa or saline. BAEP I-II interwave intervals increased in all sulfa groups (p < 10(-9) to 0.27 ms (21%) above baseline at 8 h for the two sulfa groups not receiving treatment before that time (p = 0.0002), but increased less for the sulfa group given HSA at 2 h compared with untreated animals (p = 0.02). Partial recovery of function occurred at 24 and 48 h for both HSA-treated groups compared with their 8-h values (p = 0.001), and there was increased mortality at 24 h for the sulfa group not treated with HSA (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of multiple sclerosis brainstem lesions on sound lateralization and brainstem auditory evoked potentials

Magnetic resonance (MR) imaging, brainstem auditory evoked potentials (BAEPs), and tests of interaural time and level discrimination were performed on sixteen subjects with multiple sclerosis (MS). Objective criteria were used to define MR lesions. Of the eleven subjects in whom no pontine lesions were detected and the one subject who had pontine lesions that did not encroach upon the auditory pathways, all had normal BAEPs and interaural level discrimination, although a few had abnormal interaural time discrimination. Of four subjects with lesions involving the pontine auditory pathway, all had both abnormal BAEPs and abnormal interaural time discrimination; one also had abnormal interaural level discrimination. Analysis of the data suggest the following: waves I and II are generated peripheral to the middle of the ventral acoustic stria (VAS); wave III is generated ipsilaterally in the region of the rostral VAS, caudal superior olivary complex (SOC) and trapezoid body (TB); and waves V and L are generated contralaterally, rostral to the SOC-TB. The region of the ipsilateral rostral SOC-TB is implicated as part of the pathway involved in the generation of waves V and L. Interaural time discrimination of both high and low frequency stimuli were affected by all brainstem lesions that encroached on auditory pathways. A unilateral lesion in the region of the LL affected interaural time discrimination for low-frequency stimuli less severely than bilateral lesions of the LL or a unilateral lesion of the VAS. The only interaural level discrimination abnormality occurred for a subject with a unilateral lesion involving the entire rostral VAS. It appears that detailed analysis of lesion locations coupled with electrophysiological and psychophysical data holds promise for testing hypotheses concerning the function of various human auditory brainstem structures.

Evaluation of Brain Function in Acute Carbon Monoxide Poisoning with Multimodality Evoked Potentials

The median nerve somatosensory evoked potentials (SEP), pattern reversal visual evoked potentials (VEP), and brain stem auditory evoked potentials (BAEP) were studied in 109 healthy adults and in 88 patients with acute carbon monoxide (CO) poisoning. The upper limits for normal values of peak and interpeak latencies of multimodalities of evoked potentials in the reference group were established by a stepwise multiple regression analysis. SEP changes selectively affecting N32 and N60 were found in 78.8% of patients. There was prolonged P100 latency of VEP in 58.2% of the cases examined. The prevalence of BAEP abnormalities in comatose patients (36%) was significantly higher than that (8.6%) in conscious patients. BAEP abnormalities were most frequently seen in comatose patients who had diminished brain stem reflexes (77.8%). It has been found that a consistent abnormality involving N20 and subsequent peaks in SEP, a remarkable prolongation of P100 latency in VEP, or a prolongation of III-V interpeak latency in BAEP as well as the reoccurrence of evoked potential abnormalities after initial recovery all indicate unfavorable outcomes in patients with acute CO poisoning. The multimodality evoked potentials have proved to be sensitive indicators in the evaluation of brain dysfunction and in the prediction of prognosis of acute CO poisoning and the development of delayed encephalopathy.

Evoked potentials in children with oxidative metabolic defects leading to Leigh syndrome

We studied evoked potentials in 15 children (age range: 2 wks to 4 yrs; mean: 10 mos) with metabolic disturbances that led to Leigh syndrome. These disturbances included deficiencies of pyruvate dehydrogenase (N = 5), complex 1 (N = 7), complex 4 or cytochrome oxidase (N = 2), and complex 5 (N = 1) deficiencies. Subsequent studies were performed in 11 children. All of the children with pyruvate dehydrogenase deficiency had abnormal brainstem auditory evoked potentials (BAEPs) due to poor morphology and reproducibility of the waveforms; central conduction time was normal in 4 of 5 initial studies. The patients with complex 4 or cytochrome oxidase deficiency had abnormal BAEPs, due to increased interpeak latencies and low amplitude or absent waves IV/V. Six of 7 of the children with complex 1 deficiency had normal BAEPs. The remaining patient (the youngest, age 6 wks) had only waves I and II bilaterally and suffered from the rapidly progressive form of complex 1 deficiency; the other 6 with complex 1 deficiency had the slowly progressive form. The one patient with complex 5 deficiency had normal BAEPs when first tested at 4 mos; abnormal BAEPs with loss of later waves were observed 10 weeks later. The visual evoked potentials and somatosensory evoked potentials usually were abnormal in these patients, but the findings were not specific to the patient subgroups. In all but one patient, subsequent studies disclosed a lack of normal maturational changes and/or deterioration across all 3 modalities. The BAEPs appeared to covary with the specific metabolic findings in these patients and with the patient's clinical course, but no BAEP could be considered characteristic of Leigh syndrome.

Effects of age on event-related potentials in chronic alcoholics: a multimodal study.

To test different versions of the premature aging hypothesis in alcoholics, brainstem auditory evoked potentials (BAEPs), long-latency auditory evoked potentials (LAEPs), P3 and visual evoked potentials (VEPs) were recorded in 32 alcoholic subjects. The phenomena in patients' event-related potentials (ERPs) differ from those observed in normal aging subjects and become more pronounced with age. ANOVA showed a significant effect by group (alcoholic patients/controls) on certain parameters of BAEPs (III, III-V, I-V), VEPs (P100 latency) and LAEPs (N1-P2 amplitude and N2 latency) unaffected by age, while age had a significant effect on some parameters of LAEPs (N2-P3 amplitude, P3 latency) unaffected, or less affected by chronic alcohol consumption. At a clinical level, abnormalities in BAEPs and VEPs seem good early trouble indices in alcoholic patients, while alterations in latencies and amplitudes of LAEPs appear in older patients. These data seem to be in favor of a critical age or critical abuse in the action of alcohol, in place of the classical hypothesis of premature aging.

Brainstem auditory evoked potentials correlate with morphological changes in Gunn rat pups

The relationship of brainstem structure and function in bilirubin encephalopathy is incompletely understood. The present experiments compare quantitative measures of brainstem structures with brainstem auditory evoked potentials (BAEPs) in infant jaundiced (jj) and nonjaundiced (Nj) Gunn rats. Ten jj's from 4 litters were injected with sulfadimethoxine at 11–12 days of age to raise their brain bilirubin concentration. Littermate controls were jj's given saline, and Nj's given sulfadimethoxine or saline. At 15–17 days of age BAEPs were recorded, and rats were prepared for histological examination, as was reported in the previous paper (Conlee and Shapiro. 1991). Significant differences between groups were seen for BAEP wave I latency ( P = 0.002), I–II interwave interval ( P = 0.001), and amplitudes of waves I, II, III, and IV (each P <0.0005) due to increased latencies and decreased amplitudes in the jj-sulfa group. Animals with the most severe BAEP abnormalities had the most severe histological abnormalities. Cochlear nucleus volume had a positive linear correlation with the amplitude of BAEP waves I. II, and IV, and an inverse correlation with wave I latency and I–II interwave interval ( P ≦ 0.001). The highest correlations were BAEP I–II interwave interval and amplitude of waves I and II with cochlear nucleus volume ( r = −0.78, 0.71 and 0.70, respectively, P < 0.0005). In the cochlear nucleus, spherical cell area correlated with wave I latency and amplitude, and wave III amplitude ( P < 0.001), the I–II interwave interval, and the amplitudes of waves II and IV ( P < 0.01). In contrast, globular cells, which were not affected anatomically, did not correlate significantly with later BAEP waves. Cell area in the nucleus of the trapezoid body correlated with amplitude of I and II ( P < 0.01). There were no significant correlations of cell area in the superior olive with any of the BAEP values. These results show that BAEPs are sensitive indicators of morphometric abnormalities in the brainstem of jaundiced Gunn rats, and help to establish the predictive validity of BAEPs in determining the specific sites of bilirubin-induced brain damage.

Myotonic Dystrophy: An Electrophysiological Study of Cognitive Deficits

Patients with Myotonic Dystrophy (MyD) frequently suffer from a dysfunction of the primary sensory pathways, as documented by abnormalities of short-latency evoked potentials. Impairment of intellectual functions has been less extensively investigated. Short-latency brainstem auditory evoked potentials (BAEPs) as well as long-latency auditory event-related potentials (ERPs) were recorded from 5 female and 6 male patients affected by MyD. A simple discrimination ("oddball") paradigm was used to record ERPs to tones from Fz, Cz, Pz. Both BAEPs and ERPs were significantly altered as compared to normals. BAEP abnormalities were detected in 9 patients and ERP components N2 and P3 were delayed or absent for all patients, who nonetheless correctly discriminated between tones. These data indicate that CNS dysfunction in MyD involves not only primary sensory systems but also neural mechanisms underlying cognitive events and ERP generation.

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

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.

Neurophysiological and neuro-otological study of homozygous beta-thalassemia under long-term desferrioxamine (DFO) treatment.

This report presents data on visual evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs), as well as neurologic, ophthalmologic and otologic assessments performed on 120 patients with beta-thalassemia major undergoing long-term DFO treatment. A total of 32 patients showed abnormal VEPs and 14 abnormal BAEPs; seven had both VEP and BAEP abnormalities; 12 had sensorineural hearing loss (SNHL); 18 had conductive hearing loss, while 14 showed a combination of SNHL and conductive hearing loss. After DFO administration was modified (taking in consideration the serum ferritin levels) patients with abnormal findings were retested. The values of 15 patients of 23 who underwent VEP examinations had been normalized. Eleven of 15 who repeated the BAEP test had also gained normal values. The audiogram had not returned to normal in any patient with SNHL. In a second repetition of the examinations, no change was observed. It is concluded that in a great percentage of thalassemics at least one of the above examinations shows abnormal values. These abnormalities are mostly reversible, and probably reflect a dysfunction of the visual or auditory system, due either to DFO neurotoxicity or to iron overload or both.

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

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.

Relationship between abnormal brainstem auditory-evoked potentials and subnormal CSF levels of HVA and 5-HIAA in first-episode schizophrenic patients

Auditory brainstem-evoked responses (ABRs) were recorded and the CSF concentration of the amine metabolites homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were measured in 39 drug-free schizophrenic patients. Twenty-four of the patients were first admissions and had never received antipsychotic medication. The ABRs were judgedaccording to our normative data and the CSF concentrations of the amine metabolites were compared with those of 47 healthy volunteers. Clear-cut abnormal ABRs, identified as a lack of one or more peaks or abnormal peak latencies, were found in 15 patients. In controls and patients with abrmal ABRs, there was a significant positive correlation between the cerebrosinal fluid (CSF) levels of HVA and 5-HIAA; no such correlation was found in patients with abnormal ABRs. Schizohrenics with abnormal ABRs had significantly lower levels of HVA, but not 5-HIAA, in the CSF when compared with controls. Schizophrenic patients with normal ABRs ( n = 24) did not differ from the controls with regard to the amine metabolites in CSF. A comparison of the CSF levels of HVA and 5-HIAA yielded no significant difference between patients with normal and those with abnormal ABRs. In contrast, when only first-episode, never treated schizophrenics were considered, patients with abnormal AifABRs( n = 10) had significantll lower levels of both HVA and 5-HIAA when compared with those having normal ABRs( n = 14) The results indicate an association between brainstem dysfunction and reduced central nervous dopaminergic and possibly also serotoninergic activity in schizophrenia.

LONG‐TERM IMPAIRMENTS OF BRAIN AND AUDITORY FUNCTIONS OF CHILDREN RECOVERED FROM PURULENT MENINGITIS

Sixty children who had recovered from purulent meningitis one to six years earlier were investigated for long-term impairment of brain and auditory function, using brainstem auditory evoked potentials(BAEP) and developmental screening tests. Neurological and/or audiological BAEP abnormalities were found in 23 per cent of the children: 15 per cent had mild brainstem impairment and 12 per cent had hearing dysfunction. Developmental screening tests were administered to 46 children, of whom 61 per cent had normal, 22 per cent questionable and 17 per cent abnormal results. The results of the BAEP significantly correlated with those of the developmental screening tests, suggesting that the neuropsychological development of children with BAEP abnormalities was significantly delayed compared with that of children without BAEP abnormalities. The characteristic finding in a neurologically abnormal BAEP was slightly depressed amplitude of wave V, and the authors suggest that this is the most sensitive BAEP measure for the assessment of brainstem function in children recovered from meningitis.

Auditory Evoked Potentials in Vertebrobasilar Transient Ischemic Attacks

Brainstem auditory evoked potentials (BAEPs) are affected by stroke or migraine in the vertebrobasilar arterial system. Some studies have reported BAEP changes in vertebrobasilar transient ischemic attacks (TIAs), but others have shown no alterations. We recorded BAEPs in 35 patients with TIAs in the vertebrobasilar system who did not have a stroke, other neurologic disease or significant hearing loss. Thirty patients were recorded after resolution of symptoms, while five individuals still had some resolving signs or symptoms. TIA patients as a group had longer interpeak latencies, but I-III, III-V, and I-V latencies were not significantly longer than in controls. Wave V was significantly longer in latency and lower in amplitude in TIA patients, however. The patients whose TIAs had resolved at absolute and interpeak latencies were within normal limits, but three of five had interpeak latencies at or above three standard deviations beyond the normal mean in the still symptomatic group. One of these was later tested and found to be within normal limits. BAEPs after subsidence of symptoms may add little to the evaluation of vertebrobasilar ischemia, but further AEP analysis may show more definitive differences of diagnostic use. The occasional BAEP abnormality during the resolving transient ischemia supports the recently suggested continuum between ischemia and infarction in the vertebrobasilar territory.

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 evels onl 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.

Brainstem auditory evoked potentials in Wilson's disease

Twelve patients with Wilson's disease, aged 11–25 years, underwent brainstem auditory evoked potential (BAEP) study. The results were correlated to clinical, neuroradiological and laboratory data. Ten had prominent to severe neurological manifestations, suggestive of involvement of one or several CNS structures, and 2 were neurologically free. All had evidence of abnormal copper metabolism, and 8 had CT scan evidence of brain atrophy, or hypodense areas in basal ganglia, or both. The 2 patients without neurological manifestations as well as one with neurological signs had normal BAEP. One patient with neurological signs had increased N1 latency due to cochlear hearing loss, but normal interpeak intervals, while 8 of 10 patients with prominent neurological symptoms and signs had abnormal BAEPs (prolongation of NIII-NV interpeak interval). The value of NIII-NV interpeak interval correlated with the number of different neurological signs (neurological score) attributable to involvement of different CNS structures ( r = 0.64 at P = 0.001). Abnormal BAEPs do not seem to be an early finding in Wilson's disease.

Quantitative Multiple Sclerosis Plaque Assessment With Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) of the cerebrum, cerebellum, brain stem, and upper cervical cord was performed in 62 individuals with clinically definite chronic, progressive multiple sclerosis (MS). The total area of MRI-demonstrated lesions was measured from film enlargements for each region using an interactive image analysis system. While the MRI was abnormal in 60 (97%) of 62 patients, the visual-evoked potentials in 51 (85%) of 60 patients, the brain stem auditory-evoked potentials (BAEPs) in 24 (46%) of 52 patients, and the somatosensory-evoked potentials (SSEPs) in 45 (89%) of 54 patients, an abnormal intra-blood-brain barrier (BBB) IgG synthesis rate, IgG oligoclonal bands, or both were found in all 62 patients. The total area of MRI abnormality in the cerebrum was significantly correlated only with the intra-BBB IgG synthesis rate, abnormal visual-evoked potentials, impaired performance on the Symbol Digit Modalities Test (SDMT), and one test of standing duration in the quantitative examination of neurologic function (QENF). The brain stem lesion area correlated with the Kurtzke expanded disability status scale and brain stem functional systems score, the ambulation index, abnormal BAEPs, and impaired performance on the SDMT as well as multiple tests of upper and lower extremity function in the QENF. The cerebellar lesion area correlated with impaired performance on the SDMT and primarily upper extremity testing in the QENF.(ABSTRACT TRUNCATED AT 250 WORDS)

Brainstem auditory and somatosensory evoked potentials in neuro-Behçet's syndrome.

Brainstem auditory evoked potentials (BAEPs) and somatosensory evoked potentials after median nerve stimulation (MN-SEPs) and after posterior tibial nerve stimulation (PTN-SEPs) were studied in 17 patients with neuro-Behçet's syndrome (NB). Eleven patients (64.7%) showed an absence of wave I, III or V or a prolongation of the interpeak latency I-III, or III-V in BAEPs. Six patients (37.4%) showed a prolongation in the latency of cortical P37 of PTN-SEPs and/or the interpeak latency EP-N13 or N13-N18 of MN-SEPs. The BAEP and SEP abnormalities indicated a conduction failure of the acoustic lateral lemniscus pathway and the medial lemniscus pathway in the brainstem of the patients with NB. Abnormal EPs can provide sensitive information which shows the presence of subclinical lesions in the central nervous system.

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.

Brainstem auditory evoked potential abnormalities and magnetic resonance imaging in posterior fossa lesions.

Brainstem auditory evoked potentials (BAEPs) were evaluated in a series of 15 patients with extra-axial cerebello-pontine angle tumors (3 cases), demyelinating plaques (11 cases), and intra-axial tumor (1 case), verified by magnetic resonance imaging (MRI). A satisfactory correlation between the location of the lesions and the type of BAEP abnormalities was found in 11 cases. In 2 other cases, definite MRI brainstem lesions located outside the acoustic pathways were associated with normal BAEPs. In the opposite situation (2 cases of BAEP abnormalities with normal MRI), the inability of MRI to detect demyelinating lesions may be due to the temporal evolution of the lesions themselves. The results of this BAEP-MRI comparative study confirm that BAEP is a sensitive diagnostic tool in revealing brainstem dysfunction, although its localizing power appears to be debatable. The most satisfactory MRI/BAEP topodiagnostic correlation was found with lesions involving the acoustic nerve in its intracranial tract or the caudal pons and bulbopontine junctions.

Absence of rate-dependent BAEP P 5 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 P 1–P 5 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 P 5 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.