To wake up suddenly and find that you cannot hear in one ear is a terrifying experience. Sudden sensorineural hearing loss (SSNHL) happens when there is a sudden hearing loss that is measured at 30 decibels or more involving over 3 consecutive frequencies over 3 days. In the large majority of patients, there is no identifiable cause despite extensive investigations and 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.
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 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 it’s 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.
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 in a gradually decreasing dosing strength. Sometimes, when the oral steroids are not advised in certain patients such as those with diabetes or are hepatitis carriers, then there is the option of injecting the steroids through the ear drum 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 between 4-6 injections over a period of 2-4 weeks is given.
- Hyperbaric oxygen therapy (HBOT): Hyperbaric Oxygen Therapy is a useful treatment strategy to augment the benefit of steroid administration and is usually advised within the first 3 months of the onset of ISSNHL. There is some evidence showing 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 in an attempt to improve the hearing outcomes in ISSNHL. These include the following classes of medications: Antivirals, thrombolytics, vasodilators, vasoactive substances, growth factors and antioxidants.
