Q&A: The Causes of Hearing Loss

Hearing loss is a common problem that everyone experiences from time to time. Most commonly it occurs when flying or traveling up a mountain, and a full sensation develops in the ears, leading to the feeling of wanting to pop the ears open in order to hear better. Diminished hearing also may occur during an ear infection. These causes of hearing loss are usually short-lived. The other extreme is the permanent sensorineural hearing loss that occurs with aging, which most people experience to some degree.

This article is for Medical Students & Professionals

This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the The Ear, Hearing and Balance article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
Classification of hearing loss
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Classification of hearing loss

Hearing loss may be classified into three types:

• Sensorineural, involving the inner ear, cochlea, or the auditory nerve.
• Conductive, involving any cause that in some way limits the amount of external sound from gaining access to the inner ear. Examples include cerumen impaction, middle ear fluid, or ossicular chain fixation (lack of movement of the small bones of the ear).
• Mixed loss, which is a combination of conductive and sensorineural hearing loss.

A number of abnormalities may lead to hearing loss of each type. It is useful to begin the evaluation by classifying the loss as sensorineural or conductive, since this helps focus the remainder of the patient assessment. Conductive hearing loss is usually related to abnormalities of the outer or middle ear; sensorineural hearing loss is related to inner ear pathology.

MCQ exam: clinical scenario

A 45 year old man diabetic and smoker complains of dizziness and loss of balance. On examination it is noted that he has a mild bilateral Sensorineural Hearing Loss. In the history it is noted that his sister had a demyelinating disease. He is on long term gentamycin and aspirin.

A likely diagnosis is:

a) Aminoglycoside toxicity
b) Multiple sclerosis
c) Presbycusis
d) Meniere's disease
e) Acoustic neuroma

MCQ exam: answer

The correct answer is A.
This is Aminoglycoside toxicity.

MCQ exam: explanation

The aminoglycoside antibiotics are the most ototoxic of the commonly used drugs. The first sign of gentamicin ototoxicity is disequilibrium. Monitoring blood levels is the best way to avoid such problems, adjusting dose according to peak serum levels. Other potentially ototoxic drugs include furosemide, ethacrynic acid, quinidine, and aspirin. Aspirin doses averaging 6 to 8 g/day predictably cause tinnitus and completely reversible hearing impairment.

Reference(s)
1). UpToDate: Evaluation of hearing loss in adults. Available online: https://www.uptodate.com/contents/evaluation-of-hearing-loss-in-adults