Brainstem Acoustic Evoked Potentials Research Articles

Brainstem evoked potentials and magnetic resonance imaging abnormalities in differential diagnosis of intracranial hypotension

To compare brainstem acoustic evoked potentials (BAEP) and magnetic resonance imaging (MRI) in the differential diagnosis of intracranial hypotension (IH), Chiari malformation (CM) and sensorineural hearing loss (SNHL). BAEP were recorded in 18 IH, 18 CM, 20 SNHL patients and 52 controls. MRI were acquired in all IH and CM patients. Abnormal BAEP were observed in 94% of IH patients, in 33% of CM and 70% of SNHL patients. After recovery from IH, BAEP abnormalities disappeared. Internal auditory canal (IAC) MRI abnormalities were described in 88% of IH patients. MRI signs of IH were observed in 33-78% in IH patients, but the most frequent MRI sign was 8th nerve T2 hyperintensity, with contrast enhancement in T1 sequences. This finding, combined with wave I latency, yielded highest specificity and sensitivity for IH diagnosis. Our study points out how IH can be effectively distinguished from CM and SNHL through the contribution of neurophysiology and MRI; in particular, evaluation of the 8th nerve achieves a high sensitivity and specificity in patients with IH. Further studies are required to examine the combined use of BAEP recordings ad MRI in diagnosis and monitoring of patients affected by IH.

Stochastic game of data transmission in the presence of buffers of finite capacity

Current research aimed to investigate informational content of brainstem acoustic evoked potentials (BAEPs) and auditory cognitive event-related potential — mismatch negativity (MMN) in assessment of brain functional status and cognitive functions in patients with ischemic stroke. MMN is a component of auditory event-related potential with peak latency at 100–250 ms, which reflects automatic process of difference detection between stimuli and neurodynamic processes in auditory cortex at pre-attentive stage. Clinical and neurophysiological examination, including registration of BAEPs and MMN was performed for 22 patients (12 — with ischemic stroke in carotid circulation, 10 — without cerebrovascular diseases). According to results obtained using scales of MMSE, FAB, test with 10 words repetition and Schulte tables, patients with IS demonstrated cognitive impairment as compared to control group. During BAEPs examination, functional changes in brainstem were observed (increased latency of wave V and elongation of interpeak intervals III-V on both sides and III–V ipsilaterally) in patients with ischemic stroke. Also they demonstrated increased peak latency and decreased amplitude of MMN. It points at a decline in auditory discrimination accuracy, shortened lifetime of memory traces and deficit in involuntary attention switching and also indicates of cognitive impairment.

Disfunzioni corticali e sotto-tentoriali nella Sclerosi Tuberosa

Visual evoked potentials (VEP) and brain stem acoustic evoked potentials (BAEP) were studied in eight children with tuberous sclerosis (four boys and four girls, average age 4.5 years) comparing them with a control group of 21 healthy children (ten boys and 11 girls). The patients had an increased average latency of VEP (IV component or P2; p < .01694) and BAEP (right V wave = p < .001145; left V wave = p < 013792; right I-V interpeak = p < .000543; left I-V interpeak ? p < .009854). Impaired responses were common in both VEP (80%) and BAEP (85%). In addition, altered BAEP were also present in patients without subtentorial structural abnormalities. Evoked potentials serve as a sensitive test for early diagnosis of tuberous sclerosis.

PEV e BAEP in bambini affetti da Neurofibromatosi

Visual evoked potentials (VEP) and brain stem acoustic evoked potentials (BAEP) were studied in 19 children with neurofibromatosis (13 males and six females aged from seven months to 17 years; average age 6.3 years) comparing them with those of a control group of 43 healthy children (25 males and 18 females). The patients had an increased average VEP latency (III wave = p < .01559; IV wave = p < .00001) and I-V interpeak of BAEP (right I-V interpeak = p < .04083; left I-V interpeak ? p < .00852). Impaired responses were relatively common in both VEP (40%) and BAEP (35%), with a moderate but not constant relation to neuroradiological findings. Altered potentials were also present in patients without structural abnormalities. Evoked potentials serve as a sensitive test for early diagnosis of neurofibromatosis.

L'impiego dei Potenziali Evocati nella Sclerosi Tuberosa

Evoked potentials (EP) allow the assessment of the functional integrity and degree of maturation of the main pathways of sensory afference (visual, acoustic and somaesthetic). For this reason, EP can be used in the study of patients with tuberous sclerosis. In clinical practice, EP serve to give information for early diagnosis and a better prognostic assessment of the individual patient. A recent analysis of visual evoked potentials (VEP) and brain stem acoustic evoked potentiials (BAEP) in children with tuberous sclerosis disclosed an increased average latency of some components of both VEP (component IV or P2) and BAEP (V wave and I-V interpeak). Impaired responses were present in 80% of VEP and 85% of BAEP. In addition, impaired BAEP were also present in patients without subtentorial structural abnormalities. EP serve as a useful instrument for early diagnosis of tuberous sclerosis. Given the anatomofunctional differences of the systems stimulated and the preferential location of lesions in certain areas, the various different EP have varying degrees of sensitivity in disclosing abnormalities: visual and brain stem acoustic EP are more sensitive than somatosensory EP.

Brainstem acoustic evoked potentials in children with developmental disabilities--a useful tool for differential diagnosis

In a retrospective study brainstem acoustic evoked potentials (BAEP) were evaluated in 222 children with psychomotor retardation or dysmorphic signs. Registrations were done, when no clear response to acoustic stimuli of medium intensity (60-80 dBA) could be obtained during clinical examination. Only 118 children (53%) had normal BAEP. 50 patients (22%) suffered from hearing impairment. 39 children (17%) showed disturbances of neuronal conduction. In 15 cases (7%) a combination of both conditions occurred. The mean age of our children with hearing impairment was 33.1 months, no case having been diagnosed before. In 57% the impairment was of the conductive type with an amount of less than 40 dB nHL This type was predominant in children with skeletal dysplasias (43%), chromosomal aberrations (43%) and malformation syndromes (40%). Severe hearing deficits of the sensorineural type with more than 69 dB nHL were found in children with malformation syndromes (28%), perinatal injuries (23%) and cns malformations (16%). As far as reference data were available, the hearing impairment in the BAEP was confirmed in 92% by our pedaudiologists. As a consequence hearing aids were first prescribed in 10 children, their medium age being 33.6 months. In 18 cases grommets were inserted. 9 children required paracentesis and 4 adenotomy. Disturbances of neuronal conduction with increased interpeak latencies and deformed potentials were predominantly found in the group of children with neurometabolic diseases (67%) and cns malformations (32%). Early diagnosis of hearing impairment in children with psychomotor retardation remains a problem as it is in the general population. More attention in clinical examination and appropriate screening is necessary. BAEP provide a powerful tool for hearing screening and additional information for differential diagnosis especially in children with neurometabolic diseases.

Brain stem evoked potentials in childhood neurological diseases.

This review article tries to highlight the most important information available at present on the use of brainstem acoustic evoked potentials (BAEPs) in child neurology. It lists the main original papers with considerable materials and discusses the main territories of use in child neurology according to the diagnosis. Particular emphasis has been placed on the neurodegenerative and neurometabolic disorders, asphyxia, head trauma, brain tumours, autoimmune NS diseases and evaluation of dizziness. It summarizes the importance of BAEPs in child neurology relying, on the data from the literature and the experience and opinion of the author.

Click-evoked otoacoustic emissions and acoustic brain stem potentials in early detection of hearing disorders in premature and newborn infants after neonatal critical care

Evoked otoacoustic emissions (EOAE) and brainstem acoustic evoked potentials (BAEP) were recorded from 78 children following neonatal intensive care. In 23% no EOAE could be obtained. Hearing impairment in the BAEP was found in 9%. In 22% negative EOAE were found in spite of normal BAEP. According to the latency-intensity function of waves I and V all children with abnormal BAEP were classified having a conductive hearing loss. In accordance in no case a narrowing of the emission spectrum could be found in the EOAE. In both methods the rate of hearing impairment was highest in children with birth weights of less than 1000 g. A screening of all infants after neonatal intensive care using EOAE is recommended. BAEP should be done additionally in cases with deficient EOAE.

Brainstem auditory evoked potentials in rats with streptozotocin-induced diabetes

Brainstem acoustic evoked potentials (BAEPs) were studied in streptozotocin (STZ)-diabetic rats and age-matched controls at 3 and 5 months from induction of the pathology. The diabetic status of the animals was kept uncontrolled throughout the study. Body weight and glycosylated hemoglobin were markedly altered in the diabetic animals (− 42% and + 120% of control values, respectively). Neurophysiological results showed an increase in the latency of the major components of BAEPs; this increase was clearly time-dependent for the peripheral component (peak I). The central component (peak IV) was also significantly delayed. However, no significant impairment of the central conduction time was demonstrated by examining the interpeak I–IV latency. In conclusion, BAEPs prove to be a useful non-invasive neurophysiological technique that may help unravel both the relative involvement of the peripheral and central nervous systems in the course of diabetes mellitus, and the evolution of diabetic neuropathy.

Developmental course of brain-stem auditory evoked potentials in the first days of full term infants

Modifications of brain-stem acoustic evoked potentials (BAEPs) in the first 5 days of life of normal full-term infants are reported. BAEPs were recorded using rarefaction clicks at 70, 60, 40, 20 dB HL. Multiple linear regression analysis was performed to evaluate chronological and gestational age differences for all positive and negative peaks, interpeak latencies, amplitudes and amplitude ratios. The percentage of newborn infants with auditory threshold of 20 dB HL increased with the number of days. At all intensities the latency of PIII and PV decreased significantly between the 2nd and 3rd day, while the latency of PI decreased significantly between the 3rd and the 4th day; PIII and PV latencies decreased also between the 4th and the 5th day. The longer the period of gestation the longer was the PI latency recorded between the 2nd and 5th day after birth. The anatomical and physiological changes developing shortly after birth are probably responsible for the above findings. These changes most probably appear firstly in the cochlear and trapezoid nuclei and later on in the organ of Corti.

Afferent information processing in patients with chronic alcoholism. An evoked potential study

Visual evoked potentials (VEP), median nerve sensory conduction velocity (SNCV) as well as sensory evoked potentials (SEP), and brainstem acoustic evoked potentials (BAEP) were investigated on both sides in 40 patients with chronic alcoholism (mean age 37 years) without clinical signs of alcohol-induced central nervous system lesions. The results were compared to those obtained in 40 normal controls (mean age 32 years). In both groups, the parameters were analysed by means of both dependence and interdependence statistics. Dependence statistics (ANOVA) revealed significant differences between both groups. In 70% of the patients, at least one pathological parameter (>mean ± 2.5 SD) was found; about 38% of the patients had two or more pathological values. Most pathological parameters were observed with BAEP testing (45% of patients) followed by SNCV (33%), median nerve SEP (30%), and VEP (10%). No significant clustering of pathological parameters was found in certain patients. By means of interdependence statistics, evidence is presented for a disturbance of sensory processing in the brainstem auditory pathways of the patients.

Loss of Brainstem Acoustic Evoked Potentials with Spontaneous Breathing in a Patient with Supratentorial Lesion

The loss of brainstem acoustic evoked potentials (BAEP) is considered as a confirmatory test for the diagnosis of brain death in patients with supratentorial lesions. We report a patient with ischemia in the territory of the left middle and anterior cerebral artery, who showed a loss of BAEP waves III-V as a sign of brainstem compression, but maintained spontaneous breathing and EEG activities. We conclude that occasionally BAEP may provide misleading results in the diagnosis of brain death.

Neurophysiologic monitoring in posterior fossa surgery. I. Technical principles, applicability and limitations.

In 135 cases of posterior fossa surgery almost exclusively in the cerebellopontine angle (CPA) intraoperative monitoring of brain-stem acoustic evoked potentials (BAEP) and partly somatosensory evoked potentials (SEP) was performed. The series consisted of 20 microvascular decompressions, 63 acoustic neurinomas, 7 vascular lesions and 45 other space occupying lesions, mostly in the CPA. BAEP monitoring alone was employed in 76 cases, combined BAEP and SEP monitoring less frequently. The technique of anaesthesia and intraoperative monitoring is presented in detail including an analysis of technical problems (17 in 135 = 13% of cases) and technical failures (11 of 135 = 8%). The results of monitoring brainstem pathways contralateral to the lesion are detailed. It is concluded that the technical principles of evoked potential monitoring in posterior fossa surgery are well established. The applications and limits of this technique including its modifications are described.

Effect of click-polarity on abnormality of intraoperatively monitored brainstem acoustic evoked potentials.

The configuration of brainstem acoustic evoked potentials (BAEP) is influenced by the type of click stimuli used and may thus affect detectability of abnormalities. In a group of 19 patients with lesions in the posterior fossa BAEP were recorded pre- and intraoperatively. Repeat recordings were performed in each patient in two alternating series with rarefaction and condensation click stimuli. The findings demonstrated that intraoperative potential changes in latency and amplitude were different between the two stimulation modes, but did not vary significantly in their incidence. It was also not possible to predict from the preoperative BAEP which click polarity would demonstrate intraoperative changes more markedly, taking latency and amplitude as parameters. Two conclusions are drawn from this study: None of the two stimulation modes is superior in detecting intraoperative changes and therefore no recommendation can be made which click polarity to use. When working with only one click polarity it is recommended to use occasional control recordings with the other click polarity.

Detailed analysis of intraoperative changes monitoring brain stem acoustic evoked potentials.

A series of 31 neurosurgical procedures in the posterior fossa monitored intraoperatively with ipsilateral brain stem acoustic evoked potentials (BAEPs) is analyzed for intraoperative potential changes. The evaluation of patients included pre- and postoperative BAEP recordings and pure tone audiometry. The series included 25 tumors, 4 neurovascular decompressions, 1 basilar artery aneurysm, and 1 arteriovenous malformation. Two intraoperative findings correlated significantly with a postoperative decrease in hearing: an amplitude reduction of more than 50% for Waves I to V and the loss of one of the waves, even if it was a wave that first appeared intraoperatively. We could attribute no significance to reversible or irreversible latency increases for all waves. The transient loss of one of the peaks followed by its reappearance was also insignificant with regard to postoperative hearing. A good prognostic sign was the intraoperative appearance of a peak undetectable on the preoperative recordings. These findings suggest that in intraoperative BAEP monitoring the observation of amplitude reduction is more important than that of latency increases. The surgeon should be informed when an amplitude reduction of more than 50% occurs before the peak is lost totally, as it is impossible to predict whether this peak will reappear intraoperatively.

Zur Validität der frühen akustisch evozierten Potentiale in der Diagnose des Hirntods

Brainstem acoustic evoked potentials (BAEP) in clinically proven brain death are already described in the literature. In most cases there were no reproducable BAEP or only wave I ipsilateral. In a few cases, shortly after the onset of brain death, wave I and a wave II ipsilateral have been detected.

Kreuzkorrelationsfunktionen akustisch evozierter Hirnstammpotentiale

A method for the analysis of brainstem acoustic evoked potentials (BAEP) is presented. The calculation of the normalized cross correlation function between BAEP recordings of the right and left side yields a quantitative and objective valuation of the symmetry of the electrical brainstem activity. Contrary to the usual interpretation of latencies and amplitudes the BAEP waveform is also considered. To demonstrate the regular properties of the normalized cross correlation function 20 healthy subjects were tested. Different stimulus and recording conditions, the influence of the BAEP signal length on which the calculation of the cross correlation function is based as well as filtering of the BAEP with variing cutoff frequencies are studied.

Electrophysiological investigations of the brainstem in the vertebrobasilar reversible attacks.

A total of 70 selected patients affected by reversible ischemic attacks in the vertebrobasilar system were studied. 50 patients presented transient ischemic attacks (TIA), while the other 20 patients suffered from 1-2 protracted transient ischemic attacks (PTIA). All patients underwent brainstem acoustic evoked potentials (BAEP) and electrooculography (EOG) 7-20 days from the last reversible ischemic attack, when all signs and symptoms completely disappeared. The combination of BAEP and EOG gave objective evidence of brainstem dysfunction in 61 out of 70 patients. BAEP resulted abnormal in 26 patients (16 TIA, 10 PTIA), EOG in 49 (36 TIA, 13 PTIA). Serial controls at 3, 6, and 12 months were conducted in 27 patients. 5 patients showed a normalization for BAEP and 7 for EOG 12 months after the first examination.