Power spectral analysis normal and pathological brainstem auditory evoked potentials

Brainstem auditory and visual evoked potentials in infants with myelomeningocele

Brainstem auditory-evoked potentials (BAEPs) were recorded from 26 dogs with intracranial neoplasia. The tumors were grouped according to their neuroanatomic location. Normal BAEPs were recorded from 12 dogs with cerebral (6/7), diencephalic (4/4), cerebellar (1/1), and multifocal tumors (1/5). Abnormal BAEPs were recorded from 14 dogs were cerebral (1/7), cerebellar/brainstem (4/4), brainstem (5/5), and multifocal tumors (4/5). Analysis of the multifocal neoplasms showed that alterations of BAEPs correlated with the degree of brainstem involvement. Overall, 13 of the 14 dogs with abnormal BAEPs had tumors involving the brainstem. The changes of the BAEP correlated with the extrinsic or intrinsic location of the tumor relative to the brainstem. The BAEP reflected the right, left, or median location of the tumor in 7 of the 14 abnormal recordings. In 1 dog, the BAEP was abnormal contralateral to the tumor side. A peripheral hearing disorder was excluded in most dogs based on the presence of peak I.

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.

Purpose The brainstem dysfunction in multiple sclerosis (MS) often causes significant functional impairment leading to disability. This study aims to explore modified brainstem auditory evoked potential (BAEP) scores based on the pattern of BAEP abnormalities and relate with brainstem symptoms, brainstem functional system scores (BFSS), brainstem lesions, and disability. Method Forty-five participants with relapsing-remitting MS and 45 age- and gender-matched healthy controls underwent case history assessment, otoscopic examination, pure-tone audiometry, and BAEP testing. Also, neurological examination (Expanded Disability Status Scale, FSS scales) and magnetic resonance imaging were carried out on MS participants. Patterns of BAEP abnormalities were categorized and converted to BAEP scores. Results Out of 45 participants' brainstem symptoms, BFSS > 1, brainstem lesions (magnetic resonance imaging), and BAEP abnormalities were observed in 75.6%, 42.2%, 62.2%, and 55.56% of participants, respectively. Waves V and III abnormalities were more common among MS participants and showed a significant difference from the control group in the Mann-Whitney U test. Chi-square test did not show a significant association of BAEP abnormalities with brainstem symptoms and lesions but showed significant association with BFSS. The mean and standard deviation of BAEP scores in MS participants were 1.73 + 2.37. All healthy controls showed BAEP scores of 0. BAEP scores in MS participants showed significant correlation with BFSS scores and predict Expanded Disability Status Scale scores. Conclusion BAEP scores based on the pattern of BAEP abnormality can be a valid and useful measure in evaluating brainstem functions and predicting disability in MS.

Multimodality evoked potentials as a prognostic tool in term asphyxiated newborns

Maximum Entropy Spectral Analysis (MESA) Method is a powerful alternative to the traditionally used Blackman Tukey (BT) and Fast Fourier Transform (FFT) Methods in hydrologic and climatologic time series analysis. Maximum entropy spectra of annual rainfall time series measured at Mangalore and Waltair and monthly flow time series of Godavari and Krishna Rivers in India are presented and compared with the spectra obtained by using BT and FFT methods. A recently developed Bayesian decision rule is applied to determine the length of filters in MESA. Sensitivity of the maximum entropy spectra to the length of filter used is also discussed.

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.

Brainstem auditory evoked responses (BAERs) were recorded from 202 patients with definite, probable, or possible multiple sclerosis (MS). Definitions of abnormality were based only on interwave separations and the wave I/wave V amplitude ratio. Thirty-two percent of the patients had abnormal BAERs, and the presence of clinically unsuspected lesions was revealed by BAER abnormalities in 7.4%. Thirty-five percent of the patients who had nystagmus and 53% of those who had internuclear ophthalmoplegia at the time of testing had BAER abnormalities. Forty-five percent of the abnormalities were elicited with stimulation of one ear only, stressing the importance of monaural stimulation. Click rates faster than 10 per second did not reveal abnormalities undetected at slower rates. BAERs were normal by these criteria in patients with labyrinthine diseases and amyotrophic lateral sclerosis. Thus, the BAER in MS can (1) confirm the presence of central lesions in patients with suspected brainstem involvement, (2) document the presence of clinically unsuspected lesions, and (3) be followed over time to provide possible assistance in evaluating the effectiveness of therapeutic measures. The BAER is a useful tool in the diagnosis and management of MS.

Multimodality evoked potential testing in acute mild closed head injury.

A comparison of brainstem auditory evoked responses evoked by rarefaction and condensation stimulation in control subjects and in patients with Wernicke-Korsakoff syndrome and multiple sclerosis

Continuous monitoring of brainstem auditory evoked potentials (BAEPs) was carried out in 57 comatose patients for periods ranging from 5 hours to 13 days. In 53 cases intracranial pressure (ICP) was also simultaneously monitored. The study of relative changes of evoked potentials over time proved more relevant to prognosis than the mere consideration of "statistical normality" of waveforms; thus progressive degradation of the BAEPs was associated with a bad outcome even if the responses remained within normal limits. Contrary to previous reports, a normal BAEP obtained during the second week of coma did not necessarily indicate a good vital outcome; it could, however, do so in cases with a low probability of secondary insults. The simultaneous study of BAEPs and ICP showed that apparently significant (greater than 40 mm Hg) acute rises in ICP were not always followed by BAEP changes. The stability of BAEP's despite "significant" ICP rises was associated in our patients with a high probability of survival, while prolongation of central latency of BAEPs in response to ICP modifications was almost invariably followed by brain death. Continuous monitoring of brainstem responses provided a useful physiological counterpart to physical parameters such as ICP. Serial recording of cortical EPs should be added to BAEP monitoring to permit the early detection of rostrocaudal deterioration.

Diagnostic value of multimodal evoked potentials in patients with multiple sclerosis

This paper studies the effect of otologic disease on the brain stem auditory evoked response (BAER). Both conductive and neurosensory hearing losses are analyzed by plotting wave V latencies and amplitudes as a function of sound intensity. It was found that the BAER is elicited primarily by frequencies greater than 2000 Hz. Conductive hearing losses produce a latency intensity function which approaches the norm with high decibel stimulation. Neurosensory losses produce a variety of latency intensity functions. In determining the degree of hearing loss, wave threshold is found to be the best index. Wave latency at high decibels is found to have little correspondence to degree of neurosensory loss; wave amplitude is highly variable among subjects but still a useful indicator for detecting pathology. Between-ear comparisons of wave latencies elicited by high decibel sound stimulation suggest that unilateral nonrecruiting or partially recruiting hearing losses will result in a latency difference. This method can be used to detect unilateral acoustic neuromas, and the false positives found by this technique are probably caused by other unilateral nonrecruiting hearing losses. In evaluating neurological disease, and especially when testing for a second occult lesion in multiple sclerosis (MS) an audiogram should be obtained because the criterion of a normal wave latency with decreased amplitude for the diagnosis of MS can be mimicked by peripheral hearing loss.

Assessment of brainstem function in Chiari II malformation utilizing brainstem auditory evoked potentials (BAEP), blink reflex and masseter reflex.

A case of multiple sclerosis with acute deafness and dizziness as initial symptoms was reported. The pure-tone audiometry showed a high-frequency sensorineural hearing loss; in the auditory evoked brain stem response (ABR), the left side had a normal peak I with an absence of subsequent peaks. In the equilibrium test, Bruns' nystagmus was present, and the caloric test demonstrated CP on the left side. MRI disclosed a high-intensity lesion in the cerebellar peduncle (T2-weighted image). With steroid therapy, the deafness and dizziness improved within 10 days, although, after 20 days, the findings of the ABR and caloric test remained unchanged.