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PubMedDate not supplied

Brain-stem auditory evoked responses as indicators of early brain insult.

The relationship between cranial ultrasonograms (SONOs) and brain-stem auditory evoked responses (BAERs) was evaluated in 2 independent samples of newborn infants at risk for brain injury (n = 113 and 203). Features of the BAER wave forms subjected to stepwise linear discriminant analysis formed the basis of an algorithm used to detect and follow early brain injury. Using this algorithm, information derived from BAERs reliably predicted SONO abnormalities at least 82.3% of the time in the initial study which was replicated with the second sample (77.3%). The wave I component latency (CL) and the wave III-V inter-peak latency interval (IPL) were independent of each other, and both contributed to a prediction of SONO abnormality. Possible mechanisms for these BAER results include compromise to the cochlear membrane or to the auditory nerve itself as well as prolongation of transmission in the brain-stem due to brain-stem hemorrhage, edema, or compression. Normative BAER values and non-linear regression functions for the wave I, III and V CLs, and the I-III, III-V, and I-V IPLs were calculated across age using data from 109 infants who demonstrated normal BAER patterns and had no history of SONO abnormalities. Our analyses indicate BAER techniques, where a single higher intensity is used to produce the BAER wave form, are both valid and efficient for use in the evaluation of early brain injury.

Brain Injuries↗
PubMed1999

Surgical management of cavernous malformations of the brain stem.

Different surgical approaches to the brain stem with results of excision of brain stem cavernous malformations are reported. Nine patients with brain stem cavernous malformations were operated with six different approaches. The patients were evaluated neurologically, and by magnetic resonance imaging (MRI) examination. All patients had at least one and often more episodes of haemorrhage. Seven patients underwent the total removal of the malformation, without recurrence. One patient with a large medullary cavernoma had recurrence, but without further growth. One patient with a large pontomesencephalic malformation and partial resection, suffered rebleeding due to residual cavernoma. The mean follow-up period was 49 months (range 3-112). The results of surgery were excellent or good in eight patients, and poor (worsening) in one. It is concluded that surgical resection is recommended for the cavernous malformations of the brain stem which are symptomatic, have bled or are growing, and are approachable through one of the pial surfaces of the brain stem. Different skull base approaches are useful for this procedure. Radiosurgery is not recommended in such cases.

Adult↗
PubMed1983

Vasopressin and oxytocin content are decreased in the brain stems of spontaneously hypertensive rats.

The brain stem and neurohypophyseal content of arginine vasopressin and the brain stem content of oxytocin were measured by radioimmunoassay in 3-, 7-, and 22- to 28-week-old spontaneously hypertensive rats of the stroke-prone strain (SHRSP) and the values were compared to those measured in age-matched normotensive Wistar-Kyoto rats (WKY). When compared to WKY, the content of vasopressin in the brain stems of SHRSP was reduced in all three age-groups; in contrast, the neurohypophyseal contents of vasopressin in the two species were not significantly different at 3 and 7 weeks of age and the content was increased slightly in SHRSP at 22-28 weeks. Similar to the findings for vasopressin in the brain stem, the content of oxytocin in this tissue was reduced in SHRSP at 7 and 22-28 weeks of age. The results demonstrate that brain stem arginine vasopressin levels and neurohypophyseal arginine vasopressin levels may change differentially and that the age-related differences in the brain stem levels of arginine vasopressin and oxytocin in SHRSP and WKY are consistent with the possibility that these peptides may play a role in altering cardiovascular reflex activity.

Age Factors↗
PubMed1990

Brain stem tumors.

The most common brain stem tumor in both the adult and pediatric population is the brain stem glioma. MR has significant advantages over CT in detecting the presence of the tumor as well as evaluating its extent. Diagnosis must be as precise as possible, since therapy is generally administered without biopsy material available for pathologic examination. Defining the extent of the tumor is mandatory so that appropriate radiation therapy margins are available and geometric misses do not occur. Unenhanced CT may yield some prognostic information regarding patients who have brain stem gliomas. Further work must be done to determine if any MR correlates, such as calculated T1- or T2-relaxation times, can provide similar information. Also, work relating to any prognostic information provided by the appearance of gadolinium enhancement should be undertaken. With MR, the ability to differentiate brain stem glioma from other posterior fossa tumors and from benign lesions that often do not require therapy now exists.

Adult↗
PubMed1981

Neuropathology of the brain stem in psychiatric disorders.

The brain stem was examined in a series of 27 autopsy cases for a possible association of microscopic changes and primary psychiatric disorder. Seven cases were found to have brain stem microglial nodules or perivascular infiltrates in association with a range of CNS pathological conditions. One of eight schizophrenic and none of four primary affective disorder patients showed brain stem pathology. While evident in many forms of coarse brain disease, brain stem microscopic changes do not appear related to primary psychiatric disorder.

Adult↗
PubMed1985

A staging system for brain stem gliomas.

Intrinsic brain stem neoplasms are almost invariably malignant, and irrespective of radiation treatment and chemotherapy, are associated with a very abbreviated survival. It is possible that occasional long-term survival is the result of a radiation-sensitive low-grade astrocytoma. It is suggested that a primary staging system may separate poor-risk and good-risk patient populations and that this classification may be important in assessing future therapeutic options.

Brain Neoplasms↗
PubMed1983

Comparison of the latencies between bone and air conduction in the auditory brain stem evoked potential.

Brain stem auditory evoked potentials obtained by air and bone conduction were investigated in 22 subjects. The necessity for a carefully selected stimulus being presented to the headphone and the bone vibrator is discussed. Latency values of both responses are presented for wave V. Bone conduction showed latencies which were longer than those obtained by air conduction (about 0.9 msec). Possible mechanisms for this delay are discussed.

Audiometry↗
PubMed1987

Ultrastructural alterations of neuronal cells in a brain stem ganglioglioma.

A brain stem ganglioglioma in a 9-year-old female was examined ultrastructurally. The constituent neuronal (ganglion) cells displayed various ultrastructural features of neuronal degeneration including Hirano, Lafora and zebra bodies, inclusion-like aggregates of neurofilaments and large dilatations of rough endoplasmic reticulum. Although similar observations have been reported in peripheral neuronal tumors, this is the first reported occurrence in ganglioglioma, an uncommon tumor in the central nervous system. The coincidence of these alterations in the present tumor appeared to be of great interest, however, their exact etiology remained uncertain.

Brain Neoplasms↗
PubMed1991

[The intermediary nerve at its entry and exist site in the brain stem].

On 119 brain stem halves the nerve root fasciculi of the intermediary nerve were examined in respect of their position relative to the facial and vestibulocochlear nerves. The following variants were seen: 1.) the intermediary nerve lies between the facial and vestibulocochlear nerves as stated in the textbooks, in 32.9% of the cases; 2.) in 18.5% of the cases it is entirely apposited to the vestibulocochlear nerve from the beginning and branches off from that nerve only later; 3.) part of the nerve root fasciculi are apposited to the vestibulocochlear nerve and the others originate between the facial and vestibulocochlear nerves. This was seen in 49.6% of the cases.

Brain Stem↗
PubMedDate not supplied

The approximation of audiometric thresholds by auditory brain stem responses.

Auditory brain stem response (ABR) thresholds for tone pip stimuli were compared with audiometric thresholds for 63 ears to assess the feasibility of deriving audiograms with ABR techniques. Correlations between the two measures were highly significant, indicating a high degree of accuracy in assessing degree and configuration of hearing loss with ABR. Patients with conductive losses showed a simple one-to-one relationship between ABR and audiometric thresholds, while patients with cochlear losses did not. Possibly this is due to the effects of abnormal temporal integration or poor frequency selectivity in this latter group.

Adolescent↗
PubMedDate not supplied

A study of methods used to enhance wave I in the auditory brain stem response.

Auditory brain stem responses (ABR) were recorded in 15 audiometrically and neurologically normal adult subjects. The purpose of the study was to investigate various aspects of stimulus composition (intensity, click rate, and polarity) and response measurement parameters (band-pass filtering and electrode linkage) that might serve to enhance detectability of wave I in the ABR. Amplitude of wave I was significantly enhanced by an increase in intensity, a decrease in click rate, and use of a negative (rarefaction) polarity click. Amplitude of wave I was not significantly influenced by bandwidth of the response filter or by a horizontal (mastoid-to-mastoid) electrode linkage. Use of simultaneous response acquisition from an ipsilateral and contralateral reference electrode array did aid in the detection or visualization of wave I, particularly for lower stimulus intensity levels or faster click rates.

Acoustic Stimulation↗
PubMed1982

Auditory evoked potentials from the human midbrain: slow brain stem responses.

Slow brain stem auditory evoked potentials (BAEP) were recorded in humans from depth electrodes in the thalamus and from movable electrodes within the IVth ventricle (the vicinity of the pons), the aqueduct of Sylvius (the midbrain), the IIIrd ventricle (the thalamus) and the lateral ventricle. The slow potentials consist of the positive wave peaking at 5-6 msec, and two large negative waves: No (8-10 msec) and Na (12-17 msec) in the nomenclature of Picton et al. (1974). The sources of these slow negative waves have been identified, on the basis of observation of amplitude increase in depth recordings and by tracing these potentials from their intracranial maximum to the scalp. Both No and Na have their origins in the midbrain, probably representing postsynaptic activities within the inferior colliculus. No comparable slow waves were recorded from the medial geniculate body. The present observations give a basis for non-invasive evaluation of patients with midbrain dysfunction.

Brain Stem↗
PubMedDate not supplied

The frequency specificity of tone-pip evoked auditory brain stem responses.

Auditory brain stem responses were elicited by unfiltered clicks as well as 500-Hz and 1000-Hz tone-pips with and without high-pass noise masking, from normal hearing subjects and from patients with high-frequency hearing losses. The responses elicited by tone-pips were similar in configuration to the familiar click-evoked responses. When presented in quiet, the latencies of responses elicited by tone-pips (i.e. wave V latency) were identical, or close to those evoked by clicks, suggesting common origins on the basilar membrane. With the addition of high-pass filtered white noise mixed with the tone-pips, wave V latency shifted, suggesting responses originating from apical low-frequency regions. This procedure yielded a good approximation of audiograms obtained from the same subjects. The unfiltered clicks inferred hearing sensitivity in the 2000 to 4000 Hz range, the masked tone-pips closely reproduced thresholds at 500 Hz and 1000 Hz.

Acoustic Stimulation↗
PubMed1983

Effects of stimulus repetition rate on the auditory brain stem responses (ABR).

Brain stem auditory evoked potentials were recorded from 26 normal subjects who listened to 100 ms clicks at 10, 20, 50, and 100 repetitions per second at varying intensities. A 0.5+/-0.3 ms shift of the V wave latency was observed between 10 clicks per second and 100 clicks per second; a lesser difference was found when the repetition rate was shifted between 10 to 50, 20 to 50, or 20 to 100 clicks per second. No significant differences were observed when the repetition rate moved from 10 to 20 or between 50 and 100 clicks per second. Whatever latency shifts were observed appeared to be independent of the stimulus intensity. Waveform morphology seemed to be the same between 10 and 20 clicks per second, with only minor changes observed at the 50 clicks per second rate. At 100 clicks per second a decrease or a complete disappearance of some components or both was seen. These changes are accounted for by peripheral phenomena for the most part, and a number of clinical applications are suggested based on these observations.

Acoustic Stimulation↗
PubMed1990

Transient elevation of threshold of the neonatal auditory brain stem response.

Auditory brain stem responses (ABRs) of 33 high risk, full term or near term newborns with transient elevation of ABR threshold (transient group) were compared with those of normal infants (normal group) and high-risk infants with known conductive (conductive group) and known sensorineural hearing loss (sensorineural group). ABRs of infants in the transient group initially were not significantly different from those of the conductive group in terms of wave I latency, wave V latency, and the slope of the latency-intensity (L-l) function of wave V. In infants with transient unilateral threshold elevation, significantly shorter interpeak latencies were recorded in the affected ear than in the ear that passed. This finding has been previously described in infants with conductive disorders. On follow-up, ABRs in the transient group closely resembled those of the normal group with respect to the same measures. Otologic histories in the transient group were unremarkable in the majority of cases. Increased slope of the L-l function in infants with confirmed conductive disorders was an unexpected finding. Previous studies of patients with conductive loss had not revealed a significant deviation from normal for this measure. An age interaction for the effect might explain the discrepancy between this and previous studies.

Age Factors↗
PubMed1987

Threshold characteristics of the human auditory brain stem response.

Auditory brain stem responses (ABRs) were recorded from ten normal-hearing subjects in response to 100-microseconds clicks from a TDH 49 earphone at a rate of 48 pps and at levels randomly varied in 2-dB steps between 34 and 52 dB p.e. SPL. At each level, 10 000 epochs were averaged with use of a weighted concept and a running estimate was made of the signal-to-noise ratio (SNR). This quantity was used to detect the presence of the ABR and the median threshold was found at 38 dB p.e. SPL. The mean averaged background noise level was 11.3 nVrms, and the "true" ABRrms amplitude function crossed this value at 35.5 dB p.e. SPL, which indicates the level where the SNR = 1. By extrapolation, it was found that the ABR amplitude became zero at 32 dB p.e. SPL. The perceptual thresholds of the click were estimated by means of a modified block up-down procedure, and the median value was found at 33 dB p.e. SPL. The slope of the amplitude function and the magnitude of the averaged background noise are the two factors responsible for the ABR threshold sensitivity, which thus depends on both physiological and technical parameters. Therefore, these have to be considered together with the method of detection when the ABR is used to indicate the hearing sensitivity.

Auditory Threshold↗
PubMed1992

Effect of hearing loss of cochlear origin on the auditory brain stem response.

Auditory brain stem response (ABR) testing is widely used to detect lesions of the auditory neural pathways. The ABR waves depend not only on the integrity of the neural pathways, but also on the condition of the cochlea. To properly interpret the ABR response, it is necessary to understand the effects of cochlear hearing loss on the ABR wave latencies. We studied two populations of subjects with cochlear hearing loss: one with varying degrees of high-frequency hearing loss and the other with varying degrees of flat configuration hearing loss. The degree of cochlear hearing loss was quantified in several different ways and subjected to one linear and three nonlinear regression analyses to test for accuracy in predicting ABR wave latencies and interpeak intervals (waves I, III, V, I-V, I-III, and III-V) for three click intensities. Hearing loss levels from 2 to 6 kHz, in particular 4 kHz, were superior to other audiometric test frequencies as predictors of ABR wave latencies for the group with the high-frequency losses. No particular characterization was found to be superior for the flat hearing loss configurations. From these results, modeled predictions of wave latencies as a function of degree and configuration of hearing loss were made. The modeled predictions are then used to suggest guidelines for interpretations of ABR results where hearing impaired patients are involved.

Adult↗
PubMed1977

Anoxic-ischemic encephalopathy in the human neonatal period. The significance of brain stem involvement.

Although the human brain stem is considered relatively invulnerable to ischemic anoxia, evaluation of 16 cases of a single acute asphyxial episode either at or following birth indicates that such involvement is a frequent and characteristic aspect of anoxic encephalopathy in the infant. Ischemic cell change, neuronal loss, and nuclear or reticular formation gliosis were present in the brain stem of all but one infant. At least two topographic patterns of anoxic encephalopathy exist: (1) a rostrocaudal pattern of decreasing vulnerability, with the cerebral cortex being most sensitive and the brain stem least sensitive, and (2) a pattern of brain stem and thalamic damage. Of the two, the latter pattern appears to follow most acute asphyxial episodes in the human neonate and infant.

Adolescent↗