Auditory Brainstem Response Responses Research Articles

Computer Methods for On-Line Hearing Testing with Auditory Brain Stem Responses

On-line computer methods were developed and evaluated for automated hearing testing with auditory brain stem responses (ABR). The system contained (1) a response recognition unit which recognized the presence or absence of an ABR response and (2) a threshold tracking unit which adjusted stimulus intensity and determined the ABR threshold. Two methods, one nontemplate (variance ratio) and one template (cross-correlation), were evaluated for response recognition while three threshold tracking methods were explored: clinical, Békésy, and PEST (parameter estimation by sequential testing). Both response recognition and threshold tracking units were evaluated by computer simulations for on-line operation using a standard set of experimentally recorded ABRs. The results indicated that while all the response recognition methods were reasonably accurate, their on-line use resulted in significant differences in test efficiency due to differences in tracking methods.

Effects of cisplatin and thiosulfate upon auditory brainstem responses of guinea pigs.

Two side effects which limit the use of cisplatin in cancer chemotherapy are severe nephrotoxicity and ototoxicity. The concurrent administration of sodium thiosulfate with cisplatin reportedly protects from cisplatin nephrotoxicity, however, protection from ototoxicity has not been documented. The purpose of this study was to examine the efficacy of using thiosulfate to ameliorate the ototoxic effects of cisplatin. Toward this end, the effects of cisplatin alone, cisplatin administered concurrently with sodium thiosulfate (CIS/THIO), and sodium thiosulfate alone on the auditory brainstem response (ABR) of guinea pigs were compared. ABR waveforms, comparing latencies, amplitudes and response thresholds, were monitored before, immediately after, and 30 days post treatment. Sodium thiosulfate administered with cisplatin (CIS/THIO) consistently protected animals from hearing loss and surprisingly yielded significant increases in amplitude when compared to baseline and saline controls. However, ABRs of CIS/THIO animals returned toward baseline values after 30 days.

Auditory Brain-stem Responses in Obstructive Sleep Apnea

Dr Stephen Wetmore and coworkers at the University of Arkansas (Little Rock) reported that changes in auditory brain-stem responses (ABR) occur after successful surgery for sleep apnea. Their report at the meeting of the Southern Section of the Triological Society investigated changes in the latency of ABR responses in controls and in patients with sleep apnea before and after surgery. There was no statistically significant difference between control patients and patients with preoperative sleep apnea. However, the patients with sleep apnea who achieved good control of their sleep apnea after undergoing uvulopalatopharyngoplasty of tracheostomy had a shortening of wave III and I to III interval latencies. Patients not achieving good control did not have a decrease in ABR response latencies. They conclude that ABR has no role in the preoperative evaluation of patients with sleep apnea, but their results do suggest improvement in brain-stem function after successful management of sleep

Fetal auditory brain stem response: external and intrauterine auditory stimulation.

Singleton fetuses from five pregnant ewes of 120-129 days gestation (term = 145 days) were tested for fetal auditory brain stem responses (ABR) generated by earphones placed on the maternal abdomen and compared with ABRs generated by an earphone secured in the fetal lamb's ear. To conduct these studies a cesarean section was performed on the pregnant ewe at 105-110 days gestation in order to implant stainless steel electrodes in the fetal scalp and a hearing aid receiver in the fetal external ear canal. The fetus was returned to the uterus, and the pregnancy was allowed to continue. Comparison of the externally elicited fetal ABR with the internally elicited fetal ABR indicates similar response patterns with delayed peak latencies observed in ABR responses from external stimulation. This new method of generating fetal ABRs by an external sound source documents the neurological response of the fetal auditory end organ and the fetal brain stem in the pregnant nonstressed animal model and may have applications in developmental studies of the fetal auditory system.

Stapedius reflex test, brainstem audiometry and opto-vestibular tests in diagnosis of acoustic neurinomas. A comparison of test sensitivity in patients with moderate hearing loss.

The stapedius reflex test, brainstem audiometry and the opto-vestibular tests for identifying acoustic neurinomas (AN) were evaluated and compared in a study of 21 patients with radiologically or surgically verified AN and a pure tone average not exceeding 60 dB HL. The stapedius reflex test results were interpreted according to the criteria developed at this clinic. The stimuli for the auditory brainstem response (ABR) were 2 kHz haversine waves and 4 kHz square waves. The vestibular examination consisted of a caloric test and the recording of eye-tracking and gaze nystagmus. In the cases studied the stapedius reflex test gave 1 false-negative result and ABR none. The ENG gave 3 false-negatives whereas the results of speech discrimination tests were misleading in no fewer than 1/3 of the cases. The results of the different tests were directly correlated but correlation coefficients did not exceed 0.65. Tumours larger than 15-20 mm showed a different test pattern than those below that size: stapedius reflex response, ABR and caloric response were eliminated and all of these patients had abnormal optomotor function. It is suggested that an optimal routine test procedure should consist of a pure tone audiogram, supplemented by ABR or the stapedius reflex test. Opto-vestibular tests may be of value in a preliminary estimation of tumour size.

Chronic electrical stimulation of auditory nerve in cat: Physiological and histological results.

Cats were implanted with two-channel scala tympani bipolar electrode arrays consisting of four PtIr wires in a molded silicone rubber carrier. The electrically evoked auditory brainstem response (ABR) was recorded to monitor the physiological response to biphasic pulsatile stimulation in these chronic preparations. Baseline data were collected over a 1-6 month period. Animals were then subjected to a long period of continuous high level stimulation delivered through a system designed to insure delivery of charge-balanced biphasic waveforms. Subsequent changes in physiological response were interpreted as indicating electrically induced damage to the cochlea. Localized loss of hair cells and growth of connective tissue resulted from the implantation of scala tympani inserts. Electrically evoked ABR responses were not altered by the long-term presence of the electrode, nor by the presence of intervening connective tissue. Physiological manifestations of stimulus-induced change appeared only after hundreds of hours of continuous stimulation. Apparent functional damage was not suspended or reversed with cessation of stimulation, but rather continued for several hundred hours after the stimulation was terminated. Deterioration of physiological response was accompanied by two deleterious histological changes: (a) bone growth within the scala tympani; and (b) loss of nerve fibers and spiral ganglion cells. Both of these changes were restricted to an area corresponding to the implant intracochlear location and were most marked in the region adjacent to the chronically stimulated electrode pair. In cases where stimuli were not charge balanced or surgical trauma was incurred, bone growth was most extensive and nerve damage most pervasive. The data from cases stimulated at lower levels of charge density, i.e. 20-40 muC/cm2, suggest that these may be more feasible levels for safe chronic electrical stimulation in scala tympani.