To wake up suddenly and find that you cannot hear in one ear is a terrifying experience. Sudden sensorineural hearing loss (SSNHL) occurs when hearing loss of 30 decibels or more is measured across 3 consecutive frequencies within 3 days. In the large majority of patients, there is no identifiable cause despite extensive investigations, and it is termed Idiopathic Sudden Sensorineural Hearing Loss (ISSNHL).
There are many postulations as to why this occurs, ranging from viral infections to “small strokes” to inflammatory conditions as a result of deranged immune-mediated processes. Up to two-thirds of patients with ISSNHL recover spontaneously, with the greatest recovery seen in the first 2 weeks.
Potential Causes of Sudden Sensorineural Hearing Loss
There are several causes of Sudden SNHL that can be diagnosed on investigations: These include the following:
- Acoustic Neuromas: These are tumours arising from the sheath of the balance nerve called the vestibular nerve. An MRI scan of the Internal Acoustic Meatus (Part of the Brain) will be ordered, and it will be able to diagnose this condition
- Autoimmune Diseases: Sometimes the body has a tendency to produce substances that are harmful to its own tissue because it recognises some of its own tissues as being foreign. Several blood tests are done to elicit this possibility
- Syphilis: Syphilis infection may be a possible cause of sudden SNHL and can be excluded from blood tests that will be performed
- Strokes: MRI brain scans or certain blood tests will determine the likelihood of strokes as a cause for Sudden SNHL.
Medical Management of Idiopathic Sudden Sensorineural Hearing Loss
There are numerous treatment options that have been tried for the treatment of ISSNHL:
- Steroids: Current guidelines support the use of oral steroids as a good form of initial therapy. These are usually given over a period of 2 weeks at gradually decreasing doses. Sometimes, when the oral steroids are not advised in certain patients, such as those with diabetes or who are hepatitis carriers, then there is the option of injecting the steroids through the eardrum into the middle ear space. This is known as intratympanic injection of steroids. The steroid that is often chosen is called dexamethasone. Usually, a total of 4-6 injections over 2-4 weeks is given.
- Hyperbaric oxygen therapy (HBOT): HBOT is a useful treatment strategy to augment the benefit of steroid administration and is usually advised within the first 3 months after the onset of ISSNHL. There is some evidence supporting the benefit of early adjuvant HBOT, especially in younger patients and those with at least moderate-to-severe hearing loss. HBOT therapy typically involves 10-20 sessions over several weeks.
- Other Medicines: Many other medications can also be tried to improve hearing outcomes in ISSNHL. These include the following classes of medications: Antivirals, thrombolytics, vasodilators, vasoactive substances, growth factors and antioxidants.
