Brainstem auditory evoked potential abnormalities in myelomeningocoele in the older child.

Brainstem auditory evoked potentials and clinical findings were examined in 18 children over the age of 5 years who were born with myelomeningocoele which was closed at birth, and whose hydrocephalus was managed by long term shunting in most of them. The potentials were compared with age and sex matched normal subjects and with four patients with hydrocephalus only. All but one had an abnormal brainstem auditory evoked potential with 72% showing a delay in the II-V and I-V interpeak latencies of more than three standard deviations. It is proposed that the abnormalities are a reflection of brainstem dysgenesis which is part of an associated Arnold-Chiari malformation, though the malformation was clinically asymptomatic in all. The usefulness of the brainstem auditory evoked potential for assessing the course of hydrocephalus and for predicting symptomatic Arnold-Chiari malformation is questioned.     

Brainstem auditory evoked response in adrenoleukodystrophy

Clinical, laboratory, and electrophysiological data, including brainstem auditory evoked responses, are reported in a case of adrenoleukodystrophy. A striking asymmetry was noted in wave VI of the brainstem auditory evoked potential, followed by absence of any recognizable wave on the abnormal side. The presumed site of origin of wave VI is the medial geniculate body, a structure severely involved in adrenoleukodystrophy. It is suggested that the brainstem auditory evoked response may promise noninvasive diagnostic aid in this disorder and that absence of wave VI may emerge as a clinically useful finding in diseases of the central nervous system.     

Brainstem auditory evoked potentials to different stimulus rates in parkinsonian patients

Twenty-five Parkinson's disease (PD) patients were studied by brainstem auditory evoked potentials (BAEP) with increased stimulus rate (ISR) and compared to a control age and hearing matched group. A second comparison was made between L-dopa-treated and untreated PD patients. The results of the study suggest that there is subclinical involvement of the auditory brainstem in PD patients, possibly due to the dopamine influence upon the blood vessels. Our results also indicate that dopamine is probably not involved in the synaptic transmission along the auditory pathway of the brainstem.     

Brainstem death

A patient with the clinical picture of brain death resulting from brainstem hemorrhage and subsequent infarction is presented. The EEG showed activity similar to what has been described in the cerveau isolé animal preparations. Cortical evoked potentials were unobtainable from auditory or somatosensory stimulation, but of unusually high amplitude to flash stimuli. The point is made that a diagnosis of brain death cannot be made on clinical grounds alone when a patient is on life support systems, and the differences between cerebral death, brainstem death and brain death are discussed.     

Delayed visual maturation associated with auditory neuropathy/dyssynchrony

Delayed visual maturation is a term used to describe infants who initially seem blind but subsequently have a marked improvement. The mechanism of visual loss and the subsequent improvement remains unknown. Auditory neuropathy/dyssynchrony is a condition of hearing impairment associated with absent or severely abnormal brainstem auditory evoked potentials but normal cochlear functions as measured by otoacoustic emissions. In this report, a 9-month-old infant who had no visual fixation for the first 3 months of life and congenital hearing impairment is described. Her brainstem auditory evoked potential study at 2.5 months of age showed no response to click stimuli presented at 90 dB nHL, whereas her otoacoustic emissions were normal. Subsequently, her vision and hearing improved. A brainstem auditory evoked potential study at 9 months of age showed reproducible waveforms. This case suggests the need for a detailed hearing evaluation of children with delayed visual maturation. Furthermore, this case highlights the need for follow-up brainstem auditory evoked potential testing prior to pursuing any audiologic intervention.     

Brainstem activates paroxysmal discharge in human generalized epilepsy

In nine patients with generalized epilepsy of convulsive seizures, the excitability change of the brainstem was evaluated over the course of the interictal paroxysmal discharge (poly spike-and-wave complex, poly SWC). The evaluation was carried out by a sequential analysis of brainstem auditory evoked potentials (BAEPs) before and during one sequence of poly SWC. The characteristics of BAEPs, i.e. far-field evoked potentials, allowed the evaluation of the excitability change in the brainstem, which was not influenced by the cortical activity. The excitability in the ventral brainstem, measured with the parameters of wave-III, showed a biphasic fluctuation (deceleration--acceleration) before the onset of poly SWC (minima at -0.7+/-0.4 s). On the other hand, the excitability in the dorsal brainstem, measured with the parameters of wave-V, showed no significant difference over the course of poly SWC. The results suggest that the biphasic excitability change in the ventral brainstem is conveyed to the cortex through the ascending activating system. The excitability acceleration preceded by deceleration in the ventral brainstem probably synchronizes the cortical activity profoundly enough to produce poly SWC through the activation of intralaminar thalamic neurons.     

Etiology matters for neuroprognostication: A multimodal electrophysiological investigation in a case of Bickerstaff's brainstem encephalitis

We report the case of a 19-year-old patient with an acute-onset non-traumatic coma. Brain MRI scan was normal, CSF showed mild pleocytosis and moderately elevated protein, and continuous EEG-monitoring was compatible with spindle-coma. Cortical somatosensory evoked potentials (SSEPs) and middle-latency auditory evoked potentials (MLAEPs) were bilaterally absent, and brainstem auditory evoked potentials suggested a brainstem dysfunction. Serum anti-GQ1b and anti-GT1a IgG antibodies positivity suggested Bickerstaff's brainstem encephalitis (BBE). The clinical and functional outcomes were favorable and normal cortical SSEPs/MLAEPs reappeared in a few weeks. Based on this report, in cases of unexplained MRI-negative coma with neurophysiological evidence of brainstem dysfunction, BBE should be eliminated before considering withdrawal of life-sustaining therapy (WLST).     

Short- and long-term outcome of severe neonatal nonhemolytic hyperbilirubinemia

We studied the effects of hyperbilirubinemia on brainstem auditory pathways and neurodevelopmental status in 99 full-term neonates with severe nonhemolytic hyperbilirubinemia (total serum bilirubin level = 301 to 500 micromol/L) born between 1995 and 2000. These were divided into three groups: group 1, moderate hyperbilirubinemia (n = 30; mean maximum total serum bilirubin = 320.7 micromol/L or 18.9 mg%); group 2, severe hyperbilirubinemia (n = 63; mean maximum total serum bilirubin = 369.0 micromol/L or 21.7 mg%); and group 3, super hyperbilirubinemia (n = 6; mean maximum total serum bilirubin = 457.2 micromol/L or 26.9 mg%). All received phototherapy, and three neonates also had exchange transfusion. Initial brainstem auditory evoked potentials were recorded in all at the mean age of 3.1 months (range 1-9 months). At initial assessment, only nine neonates (9.1%) had abnormal brainstem auditory evoked potentials. All except two returned to normal at 2 years. These two children had a hearing threshold at 50 nHL. We then compared serial brainstem auditory evoked potentials until 2 years for these nine cases with initial abnormal brainstem auditory evoked potentials, and nine cases with initial normal brainstem auditory evoked potentials were recruited for comparison. All 99 children had regular physical, neurologic, visual, and auditory assessments every 3 to 6 months until the age of 3 years. There was no significant correlation between demographic factors (gender, gestational age, or birthweight), maximum total serum bilirubin, and total serum bilirubin at discharge with an abnormal brainstem auditory evoked potential. There was no significant difference in the rate of brainstem auditory evoked potential abnormalities between the three groups: moderate (10%), severe (7.9%), and super (16.7%). All had normal neurodevelopmental status at 3 years. Only two children had transient mild motor delay and hypotonia, and both had normal brainstem auditory evoked potentials. There was no relationship between the abnormalities of the brainstem auditory evoked potentials and neurodevelopmental status. None of the three children receiving exchange transfusion had abnormal brainstem auditory evoked potentials or neurodevelopmental outcome. With the neurophysiologic and clinical outcomes in our cohort with severe nonhemolytic hyperbilirubinemia, we propose that the toxic effect of hyperbilirubinemia on auditory brainstem pathways might be transient provided that prompt treatment is initiated.     

Brainstem evoked potentials in panic disorder.

Patient reports and laboratory tests support the notion that panic attacks are generated by stimulation of brainstem nuclei. Scalp-recorded brainstem auditory evoked potentials may serve as a unique measurement strategy for the noninvasive assessment of the role of brainstem functioning in panic disorder. Ipsilateral and contralateral BSAEP recordings were examined in response to separate left and right ear click stimulation in 28 patients with a diagnosis of panic disorder and in 18 normal controls. Latency measures did not differentiate between the patient and control groups but amplitudes of wave III and V were found to be larger in patients. These findings are discussed in relation to pathophysiological and neurochemical theories of panic and specific emphasis is placed on serotonergic function.     

Brainstem auditory evoked response in newborns and infants

Brainstem auditory evoked response studies were carried out on 105 neonates, with gestational ages ranging from 26 to 43 weeks. The mean chronologic and postconception ages of the subjects were 6.5 weeks and 40.6 weeks, respectively. Statistically significant relationships between brainstem auditory evoked response and gestational age, postconception age (gestational age plus chronologic age), and the 5-minute Apgar score, were demonstrated. Shortening of brainstem auditory evoked response as related to postconception age was demonstrated and this trend was statistically significant. However, of these factors a statistically significant shortening (maturation) of evoked response was demonstrated only in relation to postconception age.     

Brainstem auditory evoked potential study in children with autistic disorder

Brainstem auditory evoked potentials were compared in 109 children with infantile autism, 38 with autistic condition, 19 with mental retardation, and 20 normal children. Children with infantile autism or autistic condition had significantly longer brainstem transmission time than normal (p<.001). Autistic features, rather than age, sex, or lower mentality, correlated with brainstem transmission time (p<.0001). The autistic characteristics may be related to dysfunction of the brainstem which affects the processing of the sensory input through the auditory pathway. The brainstem lesion may be part of a generalized process of neurological damage that accounts for the deviant language, cognitive, and social development in the spectrum of autistic disorder.We thank R. Ko and F. Pun for their scretarial assistance.     

Spatial Distribution of Brainstem Auditory Evoked Potentials and Their Alterations in Lesions of the VIIIth Nerve and Brainstem1

Abstract

Brainstem auditory evoked potentials (brainstem AEPs) were simultaneously recorded from 13 scalp and earlobe electrodes from normal subjects employing a noncephalic reference. The scalp distributions of the individual components (waves I-V) were presented as isopotential maps with the use of a topographic computer display system. Binaural clicks produced symmetrically distributed brainstem AEPs over the scalp. With monaural stimulation, the topography of the responses differed in locus of maximum amplitude for each of the components, suggesting that different generators are involved in the production of these components (for example, wave V is of maximal amplitude with the shortest peak latency over the contralateral frontal area). Wave I was the only component that reversed its polarity according to electrode locations. Other waves were positive over the scalp and earlobes in confonnity with the concept that they are volume conducted, far field potentials. Brainstem AEPs in subjects with lesions in the Vlllth nerve and brainstem have different distributions from those of normal subjects, that is, reversal of polarities of the components after wave I at the ipsilateral earlobe and generalized reduction of their amplitudes over the scalp and contralateral earlobe. Thus an accentuation as well as an attenuation should be carefully evaluated in the clinical assessment of brainstem AEP changes associated with brainstem lesions, for brainstem AEPs are commonly recorded from the vertex referenced to the ipsilateral earlobe. These alterations in the observed field distributions, including polarity reversals of brainstem AEPs, seem to reflect changes in the spatial properties of the generators associated with brainstern lesions, such as a reduction in the magnitude of currents with a possible deviation of the dipole axes assuming that the generator for a given component is approximated by an equivalent dipole layer source.

Brainstem auditory evoked potentials (brainstem AEPs) that can be recorded from the scalp of humans have been considered far field reflections of the potentials generated within the brainstem auditory pathways. In contrast to the long-latency AEPs, it was suggested that the position of the scalp electrode is not critical in determining the waveforms of brainstern AEPs because of the large distance of the electrode from the supposed generators. The concept of far field thus defined by Jewett and Williston (1971) has led many workers to record the potentials only from a single electrode at the vertex with the earlobe or mastoid ipsilateral to stimulation as a reference in clinical applications.

In our laboratory, however, simultaneous bilateral recordings with C₃ to A_l and C₄ to A₂ configurations have been employed. Brainstem AEPs obtained froin both sides were similar in morphology in normal subjects except for wave I, and in lesins of the VIIIth nerve and brainstem considerable asymmetries were recorded. These asymmetries of the brainstem AEPs were correlated with the site of the lesions (Hashimoto et al., 1978; Hashimoto et al., 1979a). Apart from the clinical implications of the asymmetric brainstem AEPs, we think that such profound differences seen at the different locations on the scalp are seemingly inconsistent with the definition of the volume conducted far field potentials.

To our knowledge, there have been few studies involving detailed mapping of the distribution of the potentials in humans (Picton et al., 1974; Streletz et al., 1977; Martin and Moore, 1977). In mapping studies, however, amplitudes and latencies of the brainstem AEP components were measured on separate recordings from various locations on the scalp, presenting the obvious problem of run-to-run variability.

The main objectives of the present study were (1) to map the scalp distribution of each component of brainstem AEPs in normal subjects and patients with VIIIth nerve and brainstem lesions on the basis of simultaneous recordings from multiple electrodes and (2) to relate the altered distributions to the lesions involving various levels of the brainstem. The scalp distributions of the components were presented as isopotential maps with the use of a topographic computer display system (Veno and Matsuoka, 1976).     

Brainstem auditory evoked potential in Japanese encephalitis.

Japanese encephalitis (JE) is associated with varying degrees of coma and brainstem involvement is frequent which can be evaluated and monitored by brainstem auditory evoked potential (BAEP). The present study has been undertaken to evaluate the BAEP changes and their role in predicting the outcome. Twelve adult patients with JE were subjected to CT scan, MRI and BAEP studies after detailed neurological evaluation. The severity of coma was assessed by Glasgow coma scale and outcome was defined at the end of 3 months into good and poor recovery on the basis of Barthel Index score (BI). The mean age of the patients was 28.3 years (range 14-50), and four of them were females. Most of the patients were comatose. The mean Glasgow coma scale (GCS) score was 7 (range 4-11). There were no brainstem signs or cranial nerve palsy. Cranial CT scan revealed thalamic hypodensity in four, whitematter oedema in three and left putaminal hypodensity in one patient. Cranial MRI was carried out in eight patients which revealed bilateral thalamic lesions in all, basal ganglia and midbrain lesions in three each and pontine and cerebellar lesions in one patient each. Brainstem auditory evoked potentials were recordable bilaterally. The absolute latency of wave I, II, III, IV and V and interpeak latencies (IPL) of I-V, III-V, and I-III were normal. The V/I amplitude ratio were significantly reduced in five patients. The BAEP abnormalities correlated with brainstem lesions on CT or MRI but not with severity of coma or outcome. The reduced amplitude ratio of wave V/I may be due to raised intracranial tension or brainstem involvement in JE.     

Brainstem auditory-evoked potentials in iron-deficiency anemia

Slight-to-moderate impairments may be observed in mental and motor developments of infants with iron- deficiency anemia. Brainstem auditory-evoked potentials provide a noninvasive means of examining the auditory aspect of the central nervous system functions. In this study the effect of iron-deficiency anemia on auditory functions was investigated by using brainstem auditory-evoked potentials. Brainstem auditory-evoked potentials of the 20 iron-deficient infants were not significantly different from those of the control group that included 20 healthy age-matched infants. Furthermore, there was not a statistically significant difference between the brainstem auditory-evoked potentials of the study group performed before and 3 months after oral iron therapy. Although we could not demonstrate a hearing loss in infants with moderate iron-deficiency anemia in this study, the relationship between severe iron-deficiency anemia and hearing loss or auditory dysfunction remains to be determined.     

The importance of brain stem evoked potentials in the diagnosis of neurosurgical patients]

The technique of Brainstem Electric Response Audiometry (BERA) is a non-invasive electrophysiologic method used in comatose patients for localization of areas of neuronal and synaptic dysfunction not evident in clinical evaluation. This test has a diagnostic and prognostic value in detection of abnormalities and evaluation of comatose head-injured patients at a reversible clinical stage. In contrast to most clinical signs, brainstem auditory evoked potentials are independent of levels of consciousness, analgesics, sedatives. This test is aetiologically non-specific and must be carefully integrated into the clinical situation. Generators of brainstem auditory evoked potentials are located in the auditory nerve (waves I and II) and brainstem (waves III-V). Patients in acute posttraumatic coma are assessed by means of Glasgow Coma Score (GCS), which is reliable in forecasting a favourable outcome. Patients with a score 8 points have an unfavourable outcome in 16%. Brainstem auditory evoked potentials are reliable predictors of unfavourable outcome. Subsequent brainstem auditory evoked potential testing provides relevant prognostic information, since improvement of graded brainstem auditory evoked potentials indicates a favourable outcome. Progressive deterioration of brainstem auditory evoked potentials indicates irreversible damage and is associated with unfavourable outcome, whereas singular abnormal evoked potentials may result from reversible neuronal dysfunction. The absence of waves III-V associated with the end EEG activity is the proof of brain death. Serial BERA monitoring has been used to evaluate progressive clinical syndromes, such as "uncal herniation" and evolving brain death. The use of serial BERA recordings appeared to improve the outcome predictions in comparison with single BERA tests. A combination of brainstem auditory evoked potentials, somatosensory and visual evoked potentials (multimodality evoked potentials-MEP) provides more information for management of a patient than a single evoked potential modality. The main goal to use BERA is early detection of secondary deterioration in comatose patients suffering from intracranial lesions. The results of brainstem auditory evoked potentials and clinical examination of patients obtained within the acute phase after head injury may indicate increased intracranial pressure (ICP) and incipient transtentorial herniation but do not always predict outcome (GOS). The outcome can be better evaluated later, 3-6 days after head injury. In summary, BERA is a non-invasive, safe and objective method of evaluating patients after severe head injury and adds valuable information for assessment of their outcome.     

Brainstem auditory evoked potentials in tuberous sclerosis

Brainstem auditory evoked potentials were recorded in 4 subjects and pattern reversal evoked potentials in 1 subject, all with tuberous sclerosis. Alterations were found (absence or delay of components and prolonged interpeak intervals) which may suggest impaired nervous conduction also at brainstem level in patients with tuberous sclerosis.

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Sommario Sono stati registrati i potenziali evocati auditivi troncoencefalici in 4 soggetti con sclerosi tuberosa, in uno di essi sono stati registrati anche i potenziali evocati visivi da pattern reversal. Sono state ritrovate alterazioni delle risposte (assenza o ritardo di alcune componenti ed intervalli interpicco prolungati) che possono suggerire l'esistenza di una conduzione nervosa alterata anche a livello del tronco dell'encefalo nei pazienti con sclerosi tuberosa.

     

Brainstem auditory evoked potentials in meningomyelocele

The brainstem auditory evoked potentials (BAEP) of twenty-seven Myelomeningocele (MMC) patients were analyzed and compared with the results of a normal population. The longest wave V or V-I interpeak latencies were seen in patients with shunted hydrocephalus and cranial nerve defects. The shortest wave V and V-I interpeak latencies were found in patients without hydrocephalus. However, these latencies of MMC patients were significantly longer than the latencies of a normal population. Wave I latencies of all MMC subgroups were not significantly different from the results of the normal probands. It is assumed that V-I interpeak latency prolongation in MMC patients, which is related to the severity of the clinical signs of the Arnold Chiari malformation, is mostly due to an elongation of the brainstem.     

Electrophysiologic study of Fisher syndrome

Electrophysiologic studies were performed on a 6-year-old girl with Fisher syndrome. We recorded several evoked potentials in this patient: visual evoked potentials, auditory brainstem responses, auditory evoked potentials, short-latency somatosensory evoked potentials, blink reflex elicited by photic stimuli (photo-evoked eyelid microvibration), blink reflex elicited by auditory stimuli (auditory evoked eyelid microvibration), and motor nerve conduction velocity. In our study, photo-evoked eyelid microvibration response was not obtainable; laterality was indicated in visual evoked potential and electroencephalographic studies, and the remaining evoked potentials demonstrated normal responses. The results obtained from the brainstem reflex (photo-evoked eyelid microvibration) suggest that the pathologic focus of Fisher syndrome is located in the midbrain, particularly in the pretectum. It is expected that the combined use of these electrophysiologic techniques may facilitate differentiation between Fisher and Guillain-Barré syndromes.     

Brainstem auditory evoked potential (BAEP) abnormalities in brucellosis

Twelve patients with neurobrucellosis and 17 patients with systemic brucellosis without neurological involvement underwent a brainstem auditory evoked potentials (BAEP) study. All neurobrucellosis patients (100%) showed abnormalities in their BAEP recordings, suggestive of brainstem lesions at various levels. On the other hand, only 5 (29%) of the 17 patients with systemic brucellosis had mild unilateral BAEP abnormalities, while the remaining 12 had normal responses. Comparison of pooled data between the systemic brucellosis and neurobrucellosis groups showed highly significant differences in all BAEP parameters. The recording of BAEP is thus considered a sensitive supplementary method to reveal CNS lesions in patients with neurobrucellosis.     

Brainstem auditory evoked potentials in early diagnosis of basilar artery occlusion

Brainstem auditory evoked potentials (BAEPs) were recorded in the acute and chronic phases of two patients with basilar artery occlusion. BAEPs in the acute phase showed disappearance of the waves before CT evidence of a definite low-density area in the brainstem. In one patient, the waves reappeared in the chronic phase, suggesting the importance of monitoring BAEPs in the acute phase.