ASA 125th Meeting Ottawa 1993 May

3aPP5. Effects of click polarity on ABR parameters in the older population.

Vishakha W. Rawool

Commun. Disord. & Special Educ., Bloomsburg Univ., Bloomsburg, PA 17815

The auditory brain-stem response (ABR) is known to be useful for detection of acoustic tumors and the onset of symptoms for acoustic tumors is usually between 30 and 50 years of age. Hence, this study was designed to evaluate the effects of stimulus polarity in the older population at intensity levels that are used in obtaining ABRs for clinical diagnosis. Nine subjects between the age of 40--69 years participated in the study. Rarefaction and condensation clicks were delivered at 70 and 80 dB nHL. The latencies were significantly earlier for rarefaction clicks for components II and V (p<0.05). The interpeak interval I--II was significantly shorter for rarefaction clicks than for condensation clicks (p<0.03). The amplitudes of the IV--V complex did not change with stimulus polarity at 80 dB nHL, but at 70 dB nHL larger amplitudes were observed with rarefaction clicks yielding a significant polarity--intensity interaction (p<0.04). The ratio of the IV--V complex with wave I was larger for rarefaction clicks at both the stimulus levels. These results will be discussed in reference to clinical diagnosis and auditory physiology.