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Biomedical subjects

P Kileny

Publications and source records attributed to P Kileny.

At least 19 recordsLinked to original sources
PubMed1993

Laryngeal brain stem evoked response in the porcine model.

Exaggeration of normally protective laryngeal reflexes is thought to play a role in several disorders, including the sudden infant death syndrome. An analysis of brain stem neural activity following laryngeal stimulation may provide insight into the pathophysiology of pathologic laryngeal reflexes and help to identify individuals at risk for these disorders. The purpose of this study was to define the far-field brain stem activity following laryngeal stimulation in the porcine model. This activity has been termed the laryngeal brain stem evoked response and may represent a potentially useful and objective measure of the neuronal activity in the laryngeal reflex pathway. Electrical stimulation of the superior laryngeal nerve was performed in 14 mixed-breed piglets under a variety of physiologic conditions. A total of six positive and six negative discrete waves were detected, with mean latencies ranging from 1.24 to 7.16 milliseconds. Stimulations performed during hypoxic, hypercapneic, or hypocapneic conditions resulted in no significant differences in waveform latencies. There appears to be a reproducible, but somewhat variable, brain stem response elicited by superior laryngeal nerve stimulation that can be recorded via a far-field technique in the porcine model.

Animals↗
PubMed1993

Correlation between the laryngeal brain stem evoked response and the laryngeal chemoreflex in the porcine model.

The laryngeal brain stem evoked response (LBR) represents the neural activity involved in laryngeal reflex pathways. The laryngeal chemoreflex (LCR) is a centrally mediated response consisting of apnea and hemodynamic changes that result from laryngeal stimulation. The purpose of this study is to determine the characteristics of the LBR that are predictive of LCR severity in the porcine model. The duration of apnea resulting from stimulation of the supraglottic larynx defined LCR severity. The LBR tracings were recorded from electrodes flanking the brain stem following direct electrical stimulation of the superior laryngeal nerve. The LBR peak latencies from piglets demonstrating prolonged LCR apnea were compared to those without an exaggerated LCR response. Two LBR peak latencies demonstrated a statistically significant difference between the two piglet groups. These peak latencies appear to be indicators of susceptibility to exaggerated laryngeal reflex sensitivity. Thus, the LBR may prove useful in identifying and evaluating subjects predisposed to conditions associated with dysfunctional laryngeal reflex activity.

Animals↗
PubMed1989

Effect of prenatal lignocaine on auditory brain stem evoked response.

To test the hypothesis that there would be a positive correlation between the interpeak wave (I-V) interval as measured by auditory brain stem evoked response and the ratio of umbilical cord blood arterial to venous lignocaine concentrations in infants born after maternal epidural anaesthesia, 10 normal infants born at full term by elective caesarean section were studied. Umbilical cord arterial and venous plasma samples were assayed for lignocaine, and auditory brain stem evoked responses were elicited at 35 and 70 dB at less than 4 (test 1) and greater than or equal to 48 hours (test 2). Mean wave I-V intervals were prolonged in test 1 when compared with test 2. Linear regression showed the arterial:venous ratio accounted for 66% (left ear) and 43% (right ear) of the variance in test 1 intervals. No association was found in test 2. In newborn infants, changes in serial auditory brain stem evoked response tests occur after maternal lignocaine epidural anaesthesia and these changes correlate with blood lignocaine concentrations.

Anesthesia, Epidural↗
PubMed1989

Anesthesia effects on the electrically evoked middle latency response in guinea pigs.

Recent data indicate that the electrically evoked middle latency response (EMLR) is useful for patient selection for cochlear implantation and may provide a test for determining safe levels of electrical stimulation in cochlear implant recipients. Some anesthetic agents have been reported to alter the auditory evoked middle latency response. The aim of our study was to examine the effects of ketamine and xylazine anesthesia on the EMLR in guinea pigs. A consistent, reproducible, and significant depression in the EMLR was observed after anesthesia. Response latencies were increased and the suprathreshold amplitudes were depressed initially, but later increased above preanesthetic values. Changes followed a predictable time course of depression and overshoot, which allows the investigator to compensate for these effects of anesthesia. No change in threshold was observed. The lack of threshold change and the predictable course of suprathreshold depression indicates that the EMLR may be useful to evaluate responsiveness of the auditory system to electrical stimulation in the anesthetized animal.

Anesthetics↗
PubMed1988

Hearing recovery following suboccipital excision of acoustic neuroma.

Improvement of hearing after excision of an acoustic neuroma has been observed infrequently. We present a case of dramatic recovery of hearing in a patient with a 1-cm acoustic neuroma whose pure-tone thresholds and speech discrimination had profoundly deteriorated while she awaited surgical therapy. Postoperatively, her hearing in the affected ear is equal to that in her other ear, and her speech discrimination exceeds that of her best preoperative audiogram. Issues related to hearing preservation and improvement after acoustic tumor surgery are discussed.

Female↗
PubMed1987

Neurologic, audiologic, and electrophysiologic sequelae of bilateral temporal lobe lesions.

A 67-year-old woman with demonstrated intact peripheral and brain-stem auditory pathways presented with sudden deafness secondary to sequential bilateral temporal lobe infarcts. Initial examination revealed no behavioral response to sounds and a mild Wernicke's aphasia. Hearing gradually returned but auditory agnosia persists. Changes seen on the computed tomographic scan and the middle latency auditory evoked response over a seven-month period were analyzed and suggest that the peak component of the middle latency response arises from Heschl's gyrus.

Aged↗
PubMed1987

Effects of cortical lesions on middle-latency auditory evoked responses (MLR).

Middle-latency auditory evoked responses (MLRs) were recorded simultaneously at 3 or 4 electrode locations in the coronal plane in 5 normal subjects, 11 patients with temporal lobe lesions and in 5 patients with cortical lesions not involving the temporal lobes. In patients with unilateral temporal lobe lesions, the amplitude of Pa and hence that of the Na-Pa complex was reduced over the involved hemisphere but remained intact over the contralateral hemisphere. No MLR asymmetries were demonstrated in patients with cortical lesions that did not affect the temporal lobes or in 2 cases with unilateral anterior temporal lobectomy. The latency of wave V of the auditory brain-stem response was within normal limits in the majority of the patients studied regardless of the site of their cortical lesion.

Adult↗
PubMed1986

Middle-latency and 40-Hz auditory evoked responses in normal-hearing subjects: click and 500-Hz thresholds.

Click and 500-Hz tone-burst thresholds were determined by four independent judges from sequentially recorded auditory brain stem responses--middle-latency responses (ABR-MLR)--and from 40-Hz event-related potentials (ERP) in 10 normal-hearing subjects. The thresholds determined from the two electrophysiologic methods were compared to each other and to behavioral pure-tone thresholds by means of matched-pair t tests (alpha less than or equal to .016 for each comparison). Thresholds estimated from both techniques closely approximated behavioral audiometric thresholds. The general trend was for the 40-Hz ERP thresholds to be lower than the MLR thresholds. However, the statistical analysis indicated that the differences between the two electrophysiologic thresholds and pure-tone audiometric thresholds were not significant. At threshold, the amplitudes of the 40-Hz ERPs were almost twice as large as the MLR amplitudes for clicks and only slightly larger than the MLR amplitudes for the 500-Hz tone-bursts. It was concluded that the MLR and the 40-Hz ERP techniques are equally viable procedures for threshold estimation in adults.

Acoustics↗
PubMed1986

Comments on 'Auditory brainstem responses to middle- and low-frequency tone pips'.

This article contains critical comments on data described in a recent paper dealing with differences between click- and tone-pip-evoked auditory brainstem responses (ABR) by Maurizi et al. [Audiology 23: 75-84, 1984]. The primary criticism relates to the lack of validity of comparing ABR obtained with different input filter settings. When utilizing identical input filter settings, click- and tone-pip-evoked brainstem responses exhibit similar morphologies: both consist of a slow vertex-positive wave with faster superimposed vertex-positive components.

Acoustic Stimulation↗
PubMed1985

Incidence of hearing loss in high risk and intensive care nursery infants.

The incidence of hearing impairment in high risk infants is summarized for five programs which use brainstem electric response audiometry (BERA) to detect hearing loss in this population. Programs are compared with respect to the following variables which may affect reported incidence figures: population characteristics, stimulus and recording parameters, criteria for failure on the initial BERA test, and follow-up protocols. Between 10-30% of these infants fail an initial BERA test, with initial failure rate largely dependent on the failure criteria used. Approximately 10% will continue to show some degree of hearing impairment on follow-up tests at 2-5 months of age. Between 2-4% will have a moderate to profound bilateral sensorineural hearing loss requiring amplification and habilitation.

Acoustic Stimulation↗
PubMed1985

Neurological aspects of infant hearing assessment.

The relationship between the results of an infant hearing screening program and neurological impairment may be considered in two ways: 1) Is there a correlation between incidence of neurological dysfunction and the incidence of sensorineural hearing loss in the target population? In our target population, the incidence of sensorineural hearing impairment was 3.13% for the group with a positive neurological history vs. 1.3% in those with a negative neurological history. 2) Do auditory evoked potentials used for hearing screening and follow-up provide any additional information on the neurological status of the target population, or, are certain neurological conditions associated with certain typical auditory evoked potential configurations? In our experience auditory evoked responses do provide additional information especially if for diagnostic purposes both the brainstem and the later components are considered. Often, specific neurological problems may be associated with typical auditory evoked response configurations.

Asphyxia Neonatorum↗
PubMed1983

Middle-latency auditory evoked responses during open-heart surgery with hypothermia.

Middle-latency auditory evoked responses (MLRs) were recorded from infants and adults before and during open heart surgery. Hypothermia was induced through perfusion cooling by cardiopulmonary bypass. In infants deep hypothermia (to 15 degrees C nasopharyngeal temp.) was often followed by the induction of total circulatory arrest. In adults nasopharyngeal temperatures of 25 degrees C were reached. The MLRs were elicited by unfiltered clicks presented through an insert type earphone and recorded with a vertex to ipsilateral earlobe electrode configuration. The MLRs proved to be resistant to muscle relaxation induced by pancuronium and to anesthesia induced and maintained in most cases by fentanyl. In most cases MLR peak latencies were progressively delayed as temperature decreased. Hypotension resulted in decreased MLR (Pa) amplitude.

Adolescent↗
PubMed1980

Auditory brainstem responses in perinatal asphyxia.

Averaged auditory brainstem responses (ABR) elicited by unfiltered clicks were recorded from 14 asphyxiated neonates with clinical evidence of CNS suppression at 3-17 days of age, and from a group of healthy neonates matched in gestation period and weight. Statistically significant differences were found between the two groups in several ABR parameters and characteristics. In general, longer ABR component latencies and interwave intervals were the rule in the asphyxiated group. Short-term follow-up of the asphyxiated infants suggested that the ABR is sensitive to recovery trends from hypoxic encephalopathy. The results of a 6-month follow-up are also summarized. The results are discussed with regard to the histopathological and experimental information available from current literature.

Asphyxia Neonatorum↗
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↗
PubMedDate not supplied

Normative characteristics of ipsilateral acoustic reflex adaptation.

Contralateral and ipsilateral acoustic reflex adaptation (decay) were examined using 500-, 1000-, and 2000-Hz tonal activators for stimulation periods of 30 seconds in 30 normal subjects. For these normal subjects, ipsilateral adaptation always exceeded contralateral adaptation, although differences between the two conditions were not significant. In addition, contralateral and ipsilateral acoustic reflex adaptation of four subjects with varying degrees of sensorineural hearing loss were compared to the normative data. Results for these impaired ears indicated that a longer period of activation may be necessary to distinguish between normal reflex adaptation and adaptation which may occur in cochlear pathology. Further, in three normal ears and two ears with cochlear pathology, ipsilateral adaptation equaled or exceeded 50% of the initial value within 10 seconds of activation. This finding suggests that the same criterion which is used for establishing abnormal contralateral adaptation cannot be used for abnormal ipsilateral adaptation.

Acoustic Impedance Tests↗