A pilot investigation of high-frequency audiometry in obscure auditory dysfunction (OAD) patients

The diagnosis of obscure auditory dysfunction (OAD) has been an elusive one, based primarily upon reports of poor speech perception in noise by the patient. Basic audiometric testing reveals hearing within normal threshold limits and it is thought that there may, in part be some subtle psychoacoustic and/or central auditory deficits causing this phenomenon. The use of high-frequency audiometry (HFA) as a test of subclinical cochlear damage has been well documented, especially to monitor the early effects of noise exposure and ototoxic drugs. However, it has not been used in the diagnosis of OAD patients. This study examines the use of HFA as an aid to the understanding of OAD pathophysiology. HFA was conducted on nine OAD subjects, each matched to two controls. Results indicate an elevated threshold amongst all frequencies (10-20 kHz) in OAD patients with significant differences occurring at 10, 14, 16 and 20 kHz. It could be postulated that OAD in fact, is the product of an ultra-high-frequency hearing impairment and its psychoacoustic sequelae. Furthermore, HFA may be a useful inclusion in a diagnostic test battery for OAD status. However, the degree to which it can be used may be limited due to the large intersubject variability in HFA thresholds in the normal population. It is suggested that further investigations into the ultra-high-frequency hearing abilities of OAD patients should be completed in the future.