Acoustic Brainstem Response Research Articles

Alternobaric Vertigo-Really a Hazard?

To determine the prevalence of alternobaric vertigo (AV) in sport divers and to find out whether AV led to dangerous situations underwater. Furthermore, to examine whether objective neurootologic tests are associated with the manifestation of AV. Retrospective cohort study. Sixty-three sport divers with an average diving experience of 10 years and 650 dives were questioned regarding their medical and diving history and the manifestation of vertigo during diving. Microscopic otoscopy, tympanometry, stapedius reflexes, hearing threshold for air and bone conduction, caloric video-oculography including analysis of the slow-phase velocity of the nystagmus, acoustic brain stem responses, and magnetic resonance imaging were performed to find possible differences between divers with and without AV. We found 17 divers with AV (27%). There was no significant difference in all measured parameters apart from sex and history of middle ear equalization difficulty in divers with AV. Ten (59%) of 17 female divers and 7 (15%) of 46 male divers experienced AV, representing a significant sex difference (p < 0.001). Correlation with our divers' outpatient clinic revealed that female divers had a significantly higher incidence of middle ear equalization disorders which could be an explanation for the predominance of female divers with symptoms of AV. None of the divers reported any dangerous or life-threatening situations following AV. Whether AV leads to dangerous situations underwater remains unclear, but this hypothesis is not supported by our data. Alternobaric vertigo is a common finding in divers. In our study group, female divers had a four-time higher risk to suffer AV. Our data do not support the thesis that AV is a life-threatening condition.

Mice expressing constitutively active G sα exhibit stimulus encoding deficits similar to those observed in schizophrenia patients

People with schizophrenia display sensory encoding deficits across a broad range of electrophysiological and behavioral measures, suggesting fundamental impairments in the ability to transduce the external environment into coherent neural representations. This inability to create basic components of complex stimuli interferes with a high fidelity representation of the world and likely contributes to cognitive deficits. The current study evaluates the effects of constitutive forebrain activation of the G sα G-protein subunit on auditory threshold and gain using acoustic brainstem responses and cortically generated N40 event-related potentials to assess the role of cyclic AMP signaling in sensory encoding. Additionally, we examine the ability of pharmacological treatments that mimic (amphetamine) or ameliorate (haloperidol) positive symptoms of schizophrenia to test the hypothesis that the encoding deficits observed in G sα transgenic mice can be normalized with treatment. We find that G sα transgenic mice have decreased amplitude of cortically generated N40 but normal acoustic brainstem response amplitude, consistent with forebrain transgene expression and a schizophrenia endophenotype. Transgenic mice also display decreased stimulus intensity response (gain) in both acoustic brainstem response and N40, indicating corticofugal influence on regions that lack transgene expression. N40 deficits in transgenic animals were ameliorated with low dose haloperidol and reversed with higher dose, suggesting dopamine D 2 receptor-linked G i activity contributes to the impairment. Consistent with this hypothesis, we recreated the G sα transgenic deficit in wild type animals using the indirect dopamine agonist amphetamine. This transgenic model of sensory encoding deficits provides a foundation for identifying biochemical contributions to sensory processing impairments associated with schizophrenia.

New insights into water transport and edema in the central nervous system from phenotype analysis of aquaporin-4 null mice

Aquaporin-4 (AQP4) is the major water channel in the CNS. Its expression at fluid-tissue barriers (blood–brain and brain–cerebrospinal fluid barriers) throughout the brain and spinal cord suggests a role in water transport under normal and pathological conditions. Phenotype studies of transgenic mice lacking AQP4 have provided evidence for a role of AQP4 in cerebral water balance and neural signal transduction. Primary cultures of astrocytes from AQP4-null mice have greatly reduced osmotic water permeability compared with wild-type astrocytes, indicating that AQP4 is the principal water channel in these cells. AQP4-null mice have reduced brain swelling and improved neurological outcome following water intoxication and focal cerebral ischemia, establishing a role of AQP4 in the development of cytotoxic (cellular) cerebral edema. In contrast, brain swelling and clinical outcome are worse in AQP4-null mice in models of vasogenic (fluid leak) edema caused by freeze-injury and brain tumor, probably due to impaired AQP4-dependent brain water clearance. AQP4-null mice also have markedly reduced acoustic brainstem response potentials and significantly increased seizure threshold in response to chemical convulsants, implicating AQP4 in modulation of neural signal transduction. Pharmacological modulation of AQP4 function may thus provide a novel therapeutic strategy for the treatment of stroke, tumor-associated edema, epilepsy, traumatic brain injury, and other disorders of the CNS associated with altered brain water balance.

Distortion-product otoacoustic emissions hearing screening in high-risk newborns

Universal infant hearing screening has recently been recommended by the National Institutes of Health. Otoacoustic emissions have been proposed as the first-level screening technique. Although transient evoked otoacoustic emissions have shown limited applications, distortion-product otoacoustic emissions hold promise as a screening technique but have not been fully investigated. The purpose of this study was to determine the validity of distortion-product otoacoustic emissions as a hearing screening technique. A total of 208 ears of 104 infants at risk for hearing loss were tested with both automated auditory brain stem response and distortion-product otoacoustic emission screening protocols. Acoustic brain stem response results were used as the standard for normal hearing. Distortion-product otoacoustic emission results were analyzed by means of calculation of the difference between the mean of the response levels and the mean of the noise floor levels from five frequency pairs between 2000 and 4000 Hz. Pass-fail rates for response above noise floor criteria of 5, 10, and 15 dB were examined. The sensitivity of distortion-product otoacoustic emissions was 50%, 67%, and 87%, and the specificity was 94%, 68%, and 38% at the 5, 10, and 15 dB levels, respectively. The pass-fail criterion of distortion-product otoacoustic emissions should be based on instrumentation calibration, infant status, and an acceptable false-positive, false-negative yield. The ability to test rapidly the hearing of all infants with distortion-product otoacoustic emissions points to the feasibility of using this test as a first-stage screen. (Otolaryngol Head Neck Surg 1998;118:37-43.)

Evaluation of contralateral acoustic brain stem reaction in patients with pontocerebellar angle tumors

Contralateral acoustic brain stem response (ABR) waveforms were analyzed in 63 subjects with tumors of the pontocerebellar angle. The tumors were diagnosed by CT and the diagnoses were surgically confirmed. According to the latency changes and amplitude sizes, the ABR waveforms were classified into four types (O, A, B and C). All tumors were separated into groups (depending on size), and into subgroups (depending on type). Contralateral ABR was found to be affected by tumors greater than 20 mm, and significantly more often by neuroma than by other tumors (significance level 5%).

頚静脈球憩室を合併した頚静脈球高位症例 内耳障害との関連について

The jugular bulb is the upper part of internal jugular vein in the temporal bone. Occasionally, the jugular bulb may be high. The relationship between a high jugular bulb and various inner ear diseases has been discussed by several authors. A high jugular bulb with jugular bulb diverticulum is an extremely rare condition which is thought to affect inner ear. We describe a patient with a high jugular bulb and a jugular bulb diverticulum and discuss the relationship between this condition and inner ear disorders.A 32-year-old woman had had recurrent vertigo attacks and right tinnitus for 4 years. She did not notice any hearing impairment. She suffered a severe vertigo attack starting September 19, 1991 and was admitted to Otowa Hospital on September 27.Equilibrium function was essentially normal. Pure tone audiogram (on the right) revealed low tone sensori-neural hearing loss. The acoustic brainstem response was almost symmetrical and there was no inter-peak-latency prolongation. A right plain x-ray (Schuller) showed an ordinary sigmoid sinus plate, but CT scan revealed a high jugular bulb on the right. MR angiography demonstrated a high jugular bulb and also a jugular bulb diverticulum.

Cochlear and renal pathology in the autoimmune strain mouse.

This study was designed to investigate the role of immunologic mechanisms in sensorineural hearing disorders and the relationship between inner ear and renal disorders. Autoimmune strain (NZB/kl) mice, in which autoimmune disease can be spontaneously induced, were used in this study. The mice were tested for acoustic brain stem responses, cochlear and renal disorders, and circulating immune complex serology by means of enzyme immunoassay. Pathologic studies consisted of observation of tissue changes following hematoxylin and eosin staining and indirect immunofluorescence staining under light microscopy. Compared to controls, the hearing was impaired in NZB/kl mice. Indirect fluorescence staining showed immunoglobulin G deposits in the stria vascularis. There was a correlation between the degree of hearing impairment and the severity of stria vascularis lesions. The NZB/kl mouse can provide a model for sensorineural hearing disorders secondary to immunologic disorders.

Binaural difference in rat

The binaural difference (BD) is the sum of monaural acoustic brainstem responses (ABRs) minus the binaural ABR. Its construction implies operation of a nonlinear element with binaural input. The BD in five rats was studied using insert earphones that provided 60 dB of interaural isolation measured in the occluded external meatus. Scalp to chin BD consisted of a double‐peaked complex with a following trough occurring during peaks IV and V of the sum of monaural ABRs. BD magnitude was defined as the maximum peak‐to‐trough waveform amplitude. As stimulus intensity increased, BD magnitude increased linearly with the magnitude of ABR peak I. A bilaterally symmetric stimulus generally yielded smaller BD magnitude than did stimuli with small bilateral asymmetry (8‐dB interaural intensity difference, 64‐μs interaural time difference). With larger asymmetry, BD magnitude decreased. The linear increase of BD magnitude with ABR peak I magnitude is consistent with operation of an element that applies a rectification nonlinearity to the difference of binaural signals during peaks IV and V of the ABR.

Prä- und postoperative Hörschwellen und Hirnstammpotential bei Akustikusneurinomen*

Following acoustic neuroma excision through the middle fossa route hearing was maintained in 30% (8.8% of all patients with acoustic neuroma) within 20 dB compared with preoperative thresholds. Acoustic evoked brain stem responses had the tendency to normalise within 2 to 6 months following surgery. In individual cases hearing function was improved.

Value of neuropsychologic tests and acoustic evoked brain stem potentials in the prognosis of subjective complaints in patients with brain concussion

Neuropsychological impairment and pathologically delayed Acoustic Brain stem Responses (ABR) have been found in patients examined after minor head injury. The relation of these alterations with the emergence of post-concussional symptoms is unknown. In this study 27 patients were examined with ABR within 48 hours of a clearly defined head injury and with a complete neuropsychological test battery one month after the trauma. They were checked for postconcussional symptoms such as headache, depression or dizziness one year later. ABR recordings were pathological in four patients. Neuropsychological testing showed no difference between patients and age-matched controls. No correlation was found between postconcussional symptoms and ABR and neuropsychological examination results, posttraumatic amnesia, and neurotic symptoms present before the trauma. Subclinical brain stem involvement as shown by ABR does not seem to correlate with symptoms of the postconcussional syndrome. This greatly limits the use of ABR in forensic medicine.

Analysis of cat multichannel acoustic brain-stem response data using dipole localization methods

We have used dipole localization methods (DLMs) to examine multielectrode acoustic brain-stem response (ABR) data for 9 data files collected in 5 experiments on 2 cats. The analytical model for scalp surface voltage consisted of a single current dipole in a homogeneous spherical head model. DLM sources were compared to ABR generator sites determined in intracranial and lesion experiments described in the literature. DLM source along the mediolateral axis is consistent with a predominantly ipsilateral cochlear nucleus origin for P2, and a predominantly contralateral origin for P3. DLM source for P4 and P5 was near the midline plane, consistent with the suggestion of sources arrayed along both sides of the midline. Average DLM source position increased by 7.1 mm superiorly from P3 to P5, nearly what would be expected from movement from superior olive to inferior colliculus levels. A lack of DLM source movement in the postero-anterior direction is attributed to limitations of the spherical model. The overall progression of mean DLM equivalent source position at successive ABR peaks demonstrates the existence of substantive information about generator source position in scalp surface ABR field patterns. However, model constraints of available DLM techniques present severe restrictions on the physiological interpretation of results.

Roundoff errors in signal averaging systems.

In biomedical signal averaging applications where a small repetitive signal is to be extracted form a very noisy waveform (noise variance σ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ), the A/D converter range is set at ±Aσ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> where A typically has a value of 3 or 4. In this case, A/D roundoff noise using a (b + 1)-bit A/D converter degrades the SNR of the resulting signal estimate by an amount slightly greater than 10 log (1 + A <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2b</sup> /12). Application of this result to the design of a system for digital acquisition and averaging of the acoustic brainstem response indicates that an increase of A/D resolution beyond the first few bits yields little improvement in the SNR of the measurement.

Multichannel data acquisition system for recording the acoustic brainstem response

A system has been developed to sample and average multichannel ABR data. All channels are sampled simultaneously. The simple design incorporates one sample-and-hold amplifier and one analog-to-digital converter in each channel. For sampling of 13 channels or less, sampling interval must exceed 36 μsec for full 10-bit resolution. For sampling more than 13 channels, data transfer to the host computer limits minimum sampling interval to 20+(1.2× N ) μsec, where N is the number of channels sampled.

Patterns of Acoustic Reflex and Auditory Brainstem Response Abnormality

We present results of acoustic reflex (AR) measures and auditory brainstem response (ABR) audiometry in six patients with confirmed or suspected brainstem dysfunction. In each case, specific patter...

ABR multielectrode recording: Determination of source position movement through cat brainstem

The click-evoked acoustic brainstem response (ABR), average of 512 responses, was recorded at 18 sites on the scalp of anesthetized cats. Scalp recordings were used to determine source position by attributing the scalp-surface potential field at each instant to the presence of a single current-dipole equivalent source, immersed within a spherical, homogeneous volume conductor. At each sampling instant, equivalent source position was determined by the method of Schneider [IEEE Trans. BME-21, 52–54 (1974)]. At those instants corresponding to vertex-positive response peaks, the single-source model was generally consistent with observed field patterns. Plots of equivalent source position along the axis from head center through vertex between 2.5 and 6.0 ms following the click. Movement along other axes is less prominent. Lack of movement along the centro-lateral axis may reflect the activity of sources arrayed symmetrically along either side of the brainstem, while the lack of expected ventral movement is attributed to limitations of the spherical head model assumed. [Work supported by the Whitaker Foundation.]

An analysis of auditory brainstem responses in infants.

Acoustic brainstem responses (ABRs) were recorded from 148 infants from 4 to 60 weeks of age. 28 subjects returned to the laboratory 3 or more times for additional recordings. Filtered clicks of 1, 2, 4 and 8 kHz were presented at two intensities, 30 and 50 dB HL re the average threshold for a group of young adults. Responses to a broadband click, 50 dB nHL, were also recorded. The latencies of waves I, III and V were measured. Wave I latencies for the 8 kHz filtered click showed no change but those for lower frequencies decreased with age. The latency decreases with age were largest for wave V, and, among the filtered clicks, was largest for the responses to 1 kHz. Best-fitting curves were determined for latency vs. age for each filtered click and for the broadband click. Wave V--Wave I latency differences showed that the rostral conduction time for responses to the 8 kHz FC decreased with age and, for the 1 kHz filtered click (50 dB), remained constant. The early development of basal regions in the cochlea is viewed as insuring the delivery of a wide range of frequencies to rostral segments of the auditory system. The limiting feature of maturation is at rostral sites. The immature auditory system appears to be fully capable of transducing low frequency stimuli, but not high frequencies.

Acoustic brainstem responses in adults and infants

BSRs to filtered clicks (FCs) with center frequencies at audiometric values were recorded from infants and adults. The latencies of Wave V for the respective FCs and intensities were compared for the two groups. The latencies are strongly determined by stimulus parameters: Low frequencies and weak intensities elicit responses with long latencies while high frequencies and strong intensities produce responses with short latencies. The strong stimulus control of response latency is most apparent in adults and is diminished in infants. For low frequency FC's, response latency in infants latencies lag adult values. As the infant matures, latency for the high frequencies decreases. Since Wave V is relatively late in the auditory chain, following cochlear mechanisms and, perhaps, four or more levels of neural processing, interpretation of our data is still uncertain. However, the differentiation of response latency re frequency suggests that one site of auditory maturation is within the cochlear system. [Supported by NINCDS contract NS‐5‐2313.]