Spring 08 Week 11

A student was recruited to the clinic. He reported having sudden decreased hearing sensitivity in his left ear at the age of 8 years old. Before this time, he recalls having normal hearing (i.e. he could use the telephone on both ears with no hearing difficulties). He noted having recurrent ear infections as a child; however no correlation to his sudden decrease in hearing was noted. He reported excessive noise exposure from rifle shooting for many years. He is also presently a musician who attends concerts on a weekly to monthly basis. He does not wear hearing protection during these activities. Currently, he contributes his hearing loss to noise exposure. Specific information on the type, degree, or configuration of loss was unknown by the patient even after undergoing several previous hearing evaluations as a child. He only knows that a hearing loss is present.

Otoscopy revealed normal ear canals and present, intact tympanic membranes bilaterally.
Normal, type A, tympanograms were measured bilaterally. Acoustic reflex thresholds were normal for the right contralateral and ipsilateral reflex pathways; however, there were no responses for the left contralateral and ipsilateral reflexes. Air conduction thresholds for the right ear were within normal limits using insert headphones. The left ear displayed a severe sloping to profound sensorineural hearing loss. No responses were obtained for 500 Hz, 2000 Hz, and 8000 Hz. The air and bone conduction responses of the left ear for all frequencies tested were described as “felt not heard” from vibrotactile cues due to high intensity stimuli.
Speech recognition threshold (SRT) was 10dBHL and in good agreement with the pure tone average of the right ear. Word recognition for the right ear was 100% presented at 40 dB SL. SRT and word recognition could not be tested for the left ear due to audiometer intensity restrictions.

Distortion product otoacoustic emissions (DPOAEs) yielded passing values bilaterally, at least 3 dB above the noise floor, during a 750 Hz-8000 Hz diagnostic test. No significant response differences were seen between the two ears. These results suggest properly functioning outer hair cells in the cochlea bilaterally. No consistent otoacoustic suppression pattern was measured when testing the left ear. Normal suppression occurs when DPOAEs reduce 1 to 3 dB while presenting broadband noise at 15-30 dB SL to the non-test ear. However, otoacoustic suppression results may vary among normal patients.

The patient was asked to return for auditory evoked potential testing. ABRs and single and alternating polarities electrocochleography should be administered at that time. Noise exposure and hearing protection was also discussed.

Normal DPOAEs usually suggest hearing sensitivity of 40 dB HL or better. Contrarily, behavioral responses for the left ear resulted in a profound loss. A retrocochlear loss is suspected in the left ear due to the abnormal findings of acoustic reflex thresholds and extremely elevated behavioral in the presence of normal DPOAE results. Preliminary results are consistent with unilateral late onset auditory neuropathy; however, further testing, specifically auditory brainstem response (ABR) and electrocochleography (ECochG) are needed for a complete audiologic evaluation with site-of-lesion information and is needed to confirm this suspicion. ECochG results can also give information about the cochlear microphonic when single polarity is used.

I found a study (after much searching) for treatments addressing auditory neuropathy. This study asks two questions: Does noise present a particular problem for people with auditory neuropathy? Can clear speech and cochlear implants alleviate this problem? The results concluded that clear speech improved temporal properties which, in turn, helped improve speech recognition. Comparing acoustic to electrical stimuli merited cochlear implants as a treatment option for those with auditory neuropathy. In addition, the authors suggested the use of high quality hearing aids to help with speech recognition also.


Zeng, F. & Liu, S. (2006) Speech perception in individuals with auditory neuropathy. ASHA, 49.

http://web.ebscohost.com.www.libproxy.wvu.edu/ehost/pdf?vid=1&hid=8&sid=640f8366-e105-4b8a-9cda-4c038216f6aa%40sessionmgr9