Auditory brainstem responses (ABR) in multiple sclerosis

Thirty-two multiple sclerosis (MS) patients, 10 males and 22 females, aged between 21 and 55, underwent pure-tone audiometry and testing of auditory brainstem response (ABR). Thirteen were classified as 'definite', 12 as 'probable' and 7 as 'possible', according to the McAlpine criteria. Each ear of each patient was tested monoaurally. The most common alterations were seen in the parameters of the cross-correlation between the normal template and the template of the individual MS patient. The second most altered parameters were those concerning the V wave which was absent in most cases but, when present, rarely showed latency-amplitude values falling outside the 90% confidence limit ellipses. Test-retest replicability and stimulations with increasing numbers of stimuli per second were useful in detecting intra-individual variability of waveform characteristics. When considering all the tests performed, 88% of the 'definite', 71% of 'probable' and 64% of 'possible' MS patients' ears showed ABR abnormalities. We stress the importance of a separate evaluation of the two ears due to the frequent unilateral alterations, and of an accurate evaluation of the ABR characteristics. We conclude that brainstem audiometry is a more reliable test for detecting demyelinating processes than is usually described in the literature.     

Auditory evoked averaged responses in monkeys

Averaged responses evoked by tone-bursts were investigated in the alert, anesthetized, and sedated Rhesus monkey. Identified were a short latency (peak 13.5 msec) triphasic extracranial response and a longer latency (P₁ 38 msec, N₁ 93 msec, P₂ 152 msec, N₂ 199 msec) polyphasic intracranial response. The early and late components of the intracranial response seemed to originate in different auditory centers. It was concluded that, with intracranially implanted electrodes, determining averaged response thresholds for tone-bursts in the monkey sedated with phencyclidine hydrochloride is a reasonably accurate method of estimating behavioral thresholds of hearing.     

Central auditory tests and auditory nerve-brainstem evoked responses in multiple sclerosis

In 43 multiple sclerosis (MS) patients and an equal number of age- and sex-matched normal controls, auditory nerve-brainstem evoked responses (ABR), audiometric tests, central auditory tests (CAT) and clinical-neurological examinations were conducted. The CAT included rapid alternating speech perception, masking level differences to tones and to words and lateralization based on interaural time and intensity differences. The results in the MS group on the ABR and each of the CAT differed significantly from those in the control group. The ABR results and the lateralization test results were each abnormal in 50% of the MS patients. The ABR, CAT and clinical examination results were all mutually correlated. These findings are probably related to the fact that the demyelination in MS induces a decrease in impulse velocity, to temporal dispersion and to desynchrony of impulses in groups of affected axons and to the fact that the ABR and the CAT tests chosen are dependent on synchronous impulse firing and on the precise timing of the arrival of impulses from each ear at some brain centre. These tests may therefore contribute to neurological and to audiological diagnosis.     

Stapedius reflex and brainstem auditory evoked responses in multiple sclerosis patients

The stapedius reflex (SR), its adaptation and the brainstem auditory evoked potential (ABR) were recorded in a group of 53 multiple sclerosis patients. All cases were classified as definite according to Schumacher's criteria, and their grade of disability in Hyllested's system was 1-4: no cases of the gravest (grades 5 and 6) disability were included in the series. The peripheral hearing (pure-tone audiogram and speech threshold) was normal in 44 and slightly impaired in 8 cases. SR was abnormal in 6 (11%) and borderline in 11 (21%), whereas the ABR was considered abnormal in 21 (40%) patients. Deviant SR and ABR findings had only slight or no correlation to clinical data. Intercorrelation between SR and ABR abnormality was better but not implicit and a few cases with deviant ABR showed normal SR: The frequency of abnormal and borderline SR findings was clearly higher in bilateral than in unilateral ABR abnormality. Subclassification of ABR into an upper and a lower type of pathology did not correlate with SR abnormality.     

Auditory brain stem evoked responses to bone-conducted signals.

Auditory brain stem evoked responses to air-conducted and bone-conducted signals were recorded in subjects with normal hearing and in subjects with conductive hearing loss. In normal subjects, the latency to wave V for bone-conducted signals was approximately 0.5 ms longer than the latency for air-conducted signals delivered at the same sensation level. In conductive hearing loss, the separation of the latency-intensity functions for air conduction and bone conduction (corrected for the 0.5-ms delay) provided a valid estimate of the behavioral air-bone gap in the 1,000- to 4,000-Hz region.     

Patterns of auditory abnormality in multiple sclerosis

This paper stresses the relatively high prevalence of auditory abnormality in multiple sclerosis. An auditory test battery consisting of the acoustic reflex (AR), the auditory brainstem response (ABR), the masking level difference (MLD) and speech audiometry (SA) was administered to 62 patients with diagnosed 'definite' multiple sclerosis. The AR showed the highest identification rate (71%). SA was next (55%), followed by the ABR (52%) and the MLD (45%). The combination of an abnormality on either AR, ABR or SA yielded a 90% identification rate. Interestingly, the combination of AR or SA or MLD yielded an 87% identification rate without any contribution from ABR.     

Auditory brain-stem evoked responses in cerebellopontile angle tumors

Large acoustic or nonacoustic cerebellopontile angle tumors cause severe to total hearing loss on the same side. Such a tumor can also cause hearing loss on the opposite side by pressure effect on the brain stem. This was observed in 23 patients with large tumors that were surgically treated. Their computed tomographic scans and surgical findings supported the auditory brain-stem evoked potential changes noted in this study. Early removal of such a tumor is essential to prevent any possible hearing loss on the opposite side that may be produced by the tumor.     

Auditory efferent function is affected in multiple sclerosis

OBJECTIVE: This study evaluated efferent medial olivocochlear (MOC) function in patients with multiple sclerosis (MS). Various afferent auditory abnormalities have been described in MS, but there is a paucity of data on efferent function. The brain stem is a site of predilection for MS plaques and the efferent MOC pathway may be affected at this level. METHODS: The study included 30 patients who had normal hearing. According to MRI findings, they were divided into two groups: those with an identifiable brain stem lesion (n = 10) and those with MS lesions in other parts of the central nervous system but without demonstrable MS plaques in the brain stem (n = 20). MOC function was evaluated by the olivocochlear suppression test, using transient evoked otoacoustic emissions. All subjects underwent standard auditory tests, including pure-tone audiometry and recording of auditory brain stem evoked responses. Twenty-two healthy subjects with normal hearing, matched for age and gender, served as a reference group for the auditory data. RESULTS: The results showed that 66.6% of all patients had reduced MOC function, particularly those (90%) with identified lesions of the brain stem on MRI. Furthermore, abnormal MOC function was found in 55% patients without evidence of a brain stem lesion on MRI. CONCLUSIONS: This study provides the evidence for a deficit of efferent auditory function in the majority of patients with MS. Taking into consideration the possible roles of the MOC system in processing of auditory information, abnormal MOC suppression in patients with MS may explain a variety of auditory presentations that are currently largely overlooked. This study also highlights the diagnostic value of the MOC suppression test as a site-of-lesion diagnostic test in MS and in identifying subtle brain stem lesions undetected by MRI, suggesting that subtle brain stem lesions may exist and that the MOC suppression test is sufficiently sensitive to detect them. Accordingly, the MOC suppression test may provide a tool for an early diagnosis of MS.     

Auditory deficits in multiple sclerosis: a review

This article reviews available clinical and psychophysical data concerning the effects of multiple sclerosis (MS) on basic auditory processes. On the basis of the data, it is suggested that the presence of auditory deficits should be sought in MS patients. This is especially important in light of recent psychophysical evidence suggesting that subtle auditory problems present in affected individuals may not always be detectable via conventional clinical testing. These data also provide an alternate means of interpreting various aspects of impaired auditory functioning in MS patients, and aid in generating new hypotheses regarding the possible consequences of demyelination on normal auditory perception. Finally, new ways of testing such hypotheses are proposed, and possible directions for future research are suggested.     

Auditory evoked responses in clinical populations and in the cat

An overview is presented of auditory brainstem responses (ABRs) and middle- and long-latency auditory evoked responses recorded from clinical populations and from an experimental model, the cat. The research strategy of this program is to use auditory evoked responses as surface probes of central auditory processing functions and of substrate systems. Comparisons of ABRs between normal and mentally handicapped populations indicate specific types of abnormalities in particular subpopulations. Generator substrates of these responses have been suggested from analytical animal experiments. Middle- and long-latency responses are now beginning to be compared in normal and mentally handicapped subjects. Experimental data from the cat suggest that these responses reflect the relatively independent activation of several parallel forebrain systems which receive input from brainstem levels.     

Auditory potentials of cochlear nerve and brain stem in multiple sclerosis.

Auditory evoked potentials of the cochlear nerve and the brain stem were recorded in ten patients with multiple sclerosis (MS) and four patients thought to possibly have MS. A characteristic pattern materialized, with a prolonged N1-P4 conduction time and absent or small N2 and/or N5 waves. We discuss possible clinical implications.     

Auditory brainstem evoked responses and attention. Contribution to a controversial subject

The clinical usefulness of the brainstem evoked response (BAER) derives from the high inter- and intra-subject reproducibility of V-wave latency. Attentiveness represents one possible cause of variation. To evaluate the effect of auditory or visual attention tasks and their repetition, we recorded BAERs during six repetitions of each of these two tasks. Each BAER was evoked by 2 000, 40 dB Hearing Level clicks. The results show that, at the 0.05 level, the difference in V-wave latency for auditory and for visual tasks is not significant. Moreover, repetition of the attention tasks fails to bring about any significant (p less than 0.05) change in this difference. In agreement with some researchers, but not with others, we show that attentiveness has little effect on BAER V-wave latency.     

Auditory evoked responses in control subjects and in patients with problem-tinnitus

Auditory brainstem responses (ABRs) and middle latency responses (MLRs) recorded from problem-tinnitus patients were compared with responses from normal hearing, hearing loss, and elderly subjects. Ten stimulus frequencies were presented in counterbalanced sequence and all frequencies were presented before any given frequency was presented again. The variables of importance were problem-tinnitus, hearing loss, subject age and stimulus frequency. Repeated measures analysis of variance showed a significant difference only in the latency of ABR wave 7. The intrinsically high variability in the problem-tinnitus and elderly groups rendered standard statistical analyses ineffective with the sample sizes used. Alternative analyses were employed in which the MLR waves of the normal hearing subjects were taken as the standard against which the other groups were compared. Very large MLR waves occurred in some, but not all, of the subjects in the problem-tinnitus and elderly groups. Different MLR waves were large in different subjects without correspondingly large ABR potentials. These results suggest: (1) selective alteration of MLR generators in different forms of tinnitus; and (2) differing effects of age on auditory physiology. Stimulus frequency and hearing loss contributed to this multivariate picture. Another variable, the average sound pressure level of the long-term acoustic environment, may also be important.     

Auditory responses of infants.

Forty infants, aged three through 12 months, participated in a study designed to differentiate the auditory response characteristics of normally developing infants in the age ranges three to five months, six to eight months, and nine to 12 months. Their selection was based on a determination of normal development upon pediatric examination and from the results of the Denver Developmental Screening Test. The results confirmed that a predictable developmental pattern as a function of age in the first year of life is observable despite the wide variability that may occur in a given child. Increased knowledge of these developmental milestones in normal-hearing infants should add to more effective programs of early identification and management of hearing-impaired children.