The 'normal' audiogram

Ear, Nose & Throat Journal, August, 2006 by Kenneth H. Brookler, Mohamed A. Hamid

Welcome to the first offering of the Auditory and Vestibular Medicine Clinic, formerly the Vestibulology Clinic. The Vestibulology Clinic was devoted to electronystagmography as applied to case presentations. This focus was prompted by the almost complete abandonment of this testing modality in clinical practice.

Now we are recognizing an evolution in the field of Auditory and Vestibular Medicine that originates from two disciplines. The first discipline is made up of practitioners who have confined their practice to Auditory and Vestibular Medicine, and the second discipline includes a generation of fellowship-trained neurotologic surgeons who have given up surgery and have refocused their practices on the nonsurgical management of neurotologic disorders.

In this respect, 1 believe the American Board of Otolaryngology--Head and Neck Surgery has made an error in developing the criteria for the Certificate of Added Qualifications in Neurotology by mandating a surgical experience. That certificate should have been in skull base surgery, and there should be a separate track for Auditory and Vestibular Medicine.

I have asked Mohamed Hamid, MD, PhD, to join me as coeditor of the new Clinic. A member of EAR Nose & THROAT JOURNAL'S editorial board, Dr. Harold brings with him an impressive background in audiology, vestibular science, and engineering. In 1980 he founded the Section of Vestibular and Balance Disorders at the Department of Otolaryngology and Communicative Disorders of the Cleveland Clinic Foundation, and he served as its director until 1996. At that time he founded the Cleveland Hearing and Balance Center, which is dedicated to Auditory and Vestibular Medicine, and he has since served as its director. I welcome Dr. Harold as my coeditor. We look forward to shaping the Auditory and Vestibular Medicine Clinic to reflect contemporary neurotologic practice.

According to traditional teaching, air-conduction (AC) and bone-conduction (BC) thresholds less than 20 dB are considered normal. However, some patients with normal audio will actually have subtle signs of early hearing loss.(1) An audiogram might be misinterpreted as normal even though there is a clear asymmetry (figure). In the example shown, the patient complained of difficulty hearing in the right ear despite 100% speech discrimination. A follow-up audiogram 3 months later showed further hearing loss. This finding prompted a further evaluation to search for a cochlear or retrocochlear cause. In retrospect, additional audiovestibular and radiologic studies would have been appropriate at the initial presentation.

[FIGURE OMITTED]

Traditional teaching has also implied that there is no need to test patients whose AC or BC thresholds are less than 0 dB. However, Minor reported in 2000 that it is important to test a patient whose BC level is less than 0 dB in order to uncover possible BC hypersensitivity, which is commonly seen in superior canal dehiscence syndrome. (2)

References

(1.) Harold MA. Recent advances in medical otology-neurotology. Mediterr J Otol 2005:1:45-53.

(2.) Minor LB. Superior canal dehiscence syndrome. Am J Otol 2000; 21:9-19.

Kenneth H. Brookler, MD, Mohamed A. Hamid, MD, PhD

From Neurotologic Associates, PC, New York City (Dr. Brookler), and the Cleveland Hearing and Balance Center, Beachwood, Ohio (Dr. Harold).