Dipole localization methods (DLM) and auditory evoked brainstem potentials.

Otoacoustic emissions (OAE) are sound products generated by the outer hair cells (OHC) in the inner ear. The OHC are capable of moving spontaneously or in response to acoustic stimuli (spontaneous otoacoustic emissions and evoked otoacoustic emissions), these movements are known as electromotility. Electromotility is affected when contralateral acoustic stimulation is introduced to the ear. Different types of stimuli may produce this response. Clicks, pure tones, and white masking noise have been used as contralateral stimulation. This effect appears to be mediated by the medial efferent olivocochlear bundle. Contralateral masking produces suppression of OAE, especially on the amplitude. However, the effect of contralateral masking on the latency of distortion product otoacoustic emissions (DPOAE) has not been studied. The purpose of this paper is to investigate whether contralateral masking, with wide band masking noise, may produce a significant change on the latency of the DPOAE. Three different latency measurements of DPOAE measurements were made on low, middle and high frequencies of fl including 574 Hz, 2454 Hz and 4919 Hz. Each one of these frequencies was measured with and without contralateral masking. Twenty-eight ears of 15 subjects were studied. Non-significant differences (P > 0.05) between masked and unmasked conditions were found in all cases. It is concluded that contralateral masking does not appear to affect latency of DPOAE.

Audiometry↗

PubMed1998

Prevalence and etiology of unilateral sensorineural hearing impairment in a Finnish childhood population.

A retrospective study was undertaken on the prevalence and etiology of unilateral sensorineural hearing impairment (> 25 dB at 0.5-4 kHz, including mixed hearing impairments with bone conduction thresholds > or = 25 dB) among children born between 1972 and 1986 in a province of eastern Finland. Only patients who had been diagnosed before the age of 10 years were included. A total of 84 children with such an unilateral hearing loss were identified, with prevalence of 1.7 per 1000 live births. A significant decline from the prevalence of 2.2 per 1000 in the 1970s to the prevalence of 1.2 per 1000 in the 1980s was observed, which was mainly due to the disappearance of hearing losses caused by mumps and measles in the 1980s and the decrease in cases attributed to otitis media. In agreement with some previous studies, a considerable male predominance was present. Thirty-five percent of the hearing losses were profound (> 95 dB) and 15% were severe (71-95 dB). Etiology of the hearing impairment was estimated as genetic in 2%, congenital non-genetic in 12%, delayed-onset non-genetic in 35% and remained unknown in 51%.

Audiometry↗

PubMed1998

Sensorineural hearing loss in children after liver transplantation.

OBJECTIVE: To investigate risk factors for sensorineural hearing loss (SNHL) in children after liver transplantation. DESIGN: Retrospective medical record review. SETTING: Pediatric tertiary care hospital. PATIENTS: One hundred twenty-five consecutive children who received liver transplants between March 1, 1987, and June 30, 1996. MAIN OUTCOME MEASURES: The presence of SNHL (bone conduction threshold of >35 dB of hearing loss in at least 1 frequency) and the cause of the liver abnormality in all 125 patients. In addition, among the subset of children who had biliary atresia and underwent transplantation before 2 years of age, the total dose (milligrams per kilogram of body weight) of aminoglycoside antibiotic medications (tobramycin sulfate, gentamicin sulfate, and amikacin sulfate) and of intravenous loop diuretic agents (furosemide) was compared between children with and without SNHL. RESULTS: Audiologic evaluations were available for 66 of 125 patients, 15 (12%) of whom have SNHL. Of 5 survivors with the short-bowel syndrome, 4 have severe to profound SNHL. Of 46 children who have biliary atresia and who underwent transplantation before 2 years of age, 8 (17%) have SNHL. Among the 26 evaluable children with biliary atresia undergoing liver transplantation before 2 years of age, logistic regression analysis revealed that the most important risk factor for SNHL was the cumulative dose of amikacin (P = .05). CONCLUSIONS: Children receiving liver transplants are at an increased risk for SNHL. Those with the short-bowel syndrome have the greatest prevalence of SNHL. Among the subset of children with biliary atresia receiving liver transplants before 2 years of age, statistical analysis demonstrates a dose-response relationship between the receipt of amikacin and the occurrence of SNHL.

Audiometry↗