Spring 08 Week 3

I saw an adult man who stated that he notices a hearing loss especially in his left ear with occasional tinnitus. A previous surgery for the removal of a neuroma of the pituitary gland was reported. However, he noted that his hearing loss did not coincide with the surgery. He also reported having served in the military and he target shoots annually.

Otoscopy revealed normal ear canals and tympanic membranes bilaterally. Immittance results were normal type A tympanograms bilaterally. Pure tone audiometry using insert earphones revealed a normal sloping at 1000 Hz to severe sensorineural hearing loss in the left ear. The right ear is normal sloping at 500 Hz to severe sensorineural hearing loss with an abnormal air-bone gap at 1000 Hz. Pure tone averages were in good agreement with the speech recognition thresholds of 30 dB in the right ear and 55 dB in the left ear. Speech discrimination was 84% in the right ear and 60% in the left ear. According to the results, the client has a sensorineural hearing loss bilaterally with an unexplained, unusual air-bone gap at 1000 Hz that was retested with active assistance of the supervisor.

After this finding, several other patients had strange masking responses in our clinic. When searching for an article about calibration and the effects on bone conduction scores, I found this article which discusses random and systematic errors made when performing BC audiometry. When two different sites were observed, bone conduction thresholds at 2 kHz revealed a notch or 'inflection'. The authors described, "part of the problem appears to be related to excessive air borne sound from the bone vibrator at these high frequencies. Regarding lower frequencies, several audiology professionals in the UK have expressed some concern about the accuracy of bone conduction at 1 kHz and 2 kHz". As a result, the authors suggest a complete review of technology of bone vibrators and also precise placement of the bone vibrators. This was a very strange finding since I've never heard of it. This may be a useful piece of information for all clinics.


O'Neill, G. et al. (2000). Systematic errors in bone conduction audiometry. Clinical Otolaryngology, 25, 357-369.

http://web.ebscohost.com/ehost/pdf?vid=1&hid=104&sid=3d17ea14-0ffe-465b-a833-cd2aaebebedf%40sessionmgr102