Sudden Hearing Loss
Timothy C. Hain, MD
Last update: 10/2001
What is Sudden Hearing Loss?
Sudden hearing loss (SHL) is defined as greater than 30 dB hearing reduction, over at least three contiguous frequencies, occuring over 72 hours or less. It occurs most frequently in the 30 to 60 year age group and affects males and females equally. Although called sudden, it seems unlikely that hearing loss is abrupt but rather it probably evolves over a few hours.
SHL can affect different people very differently. SHL is usually unilateral (that is, it affects only one ear); and is often accompanied by tinnitis. vertigo, or both. The amount of hearing loss may vary from mild to severe, and may involve different parts of the hearing frequency range. SHL may be temporary or permanent. About one third of people with SHL awaken in the morning with a hearing loss.
What Causes Sudden Hearing Loss?
Although some hold that this disease is generally idiopathic (of unknown cause), viral disease appears to be the basis for about 60% of all cases of SHL. Viruses detected at a study at the Massachusetts Eye/Ear infirmary included influenza type B, CMV, mumps, rubeola, and varicella-zoster (Harris, 1998). Others include measles, herpes-1, and infectious mononucleosis. Many of these are in the herpes family.
How is Sudden Hearing Loss Diagnosed?
In essence, SHL is diagnosed by documenting a recent decline in hearing. This generally requires an audiogram. Other studies are performed mainly to look for specific causes. The differential diagnosis includes viral disease, vascular disease (1%), autoimmune phenomena, perilymph fistulae and Meniere's disease, and acoustic neuroma (about 4 to 6% of SHL -- see Daniels et al, 2000 for a longer list of diagnoses). Evaluation usually begins with a careful history looking for potential infectious causes such as otitis media and exposure to known ototoxic medications.
How is Sudden Hearing Loss Treated?
Mattox and Simmons (1977) reported a rate of 65% spontaneous recover to "functional hearing levels." Byl also reported a recovery rate of about 69% (Byl, 1984). Because hearing tends to recover spontaneously at such a high rate, treatment is not always felt necessary, especially when impairment is minor.
When a treatment of SHL is used, it often consists of a burst of steroids such as prednisone. Eisenman and Arts recently reviewed the topic of steroid treatment (2000). Evidence to date for a good effect is mixed. Some studies suggest a better hearing prognosis for treated vs. untreated patients (Haberkamp and Tanyeri, 1999; Alexiou et al, 2001), and others a worse prognosis (Minoda et al, 2000). In the study of Alexiou et al, a better prognosis was associated with very high doses of intravenous prednisolone. Gianoli has recently reported a good response to transtympanic steroids, in persons who were unable to tolerate oral steroids (Gianoli, 2001).
Fattori et al (2001) suggested that hyperbaric oxygen therapy was the treatment of choice. This involved 10, 90-minute sessions of breathing pure oxygen at 2.2 atmospheric pressure in a multiperson chamber. While encouraging, is is difficult to see why this treatment should work and we would like to see this result confirmed with other studies.
Antivirals seem reasonable, given the frequency that herpes family viruses have been associated with SHL. In a recent animal study, combination treatment with an antiviral (acylovir) and steroids reduced damage in animals whose ears were inoculated with herpes simplex virus type 1 (HSV-1) (Stokroos, 1999), compared to treatment with either acyclovir or prednisolone alone. Unfortunately, in humans, acyclovir treatment seems unlikely to be helpful when the cause is a virus that is not in the herpes family, and one rarely knows at the time of the hearing loss which if any virus is responsible.
Research Studies in Sudden Hearing Loss
Haberkamp and Tanyeri recently reviewed the management of idiopathic SHL (Haberkamp and Tanyeri, 1999). They noted that while numerous treatments have been studied aiming to improve blood flow, such as Carbogen inhalation or stellate ganglion block, all remain controversial or simply lack convincing evidence of efficacy. Very few placebo controlled studies have performed of treatment of SHL and for this reason, there is presently a limited ability to determine what is the optimal treatment of SHL. At the American Hearing Research Foundation (AHRF), we are interested in funding good research on this condition. We have funded basic research on similar conditions in the past. If you would you would like more information about contributing to the AHRF's efforts, click here.
References
- Alexiou C and others. Sudden sensorineural hearing loss. Does application
of glucocorticoids make sense? Arch OHNS 2001127:253-258
- Byl FMJ. Sudden hearing loss: eight years experience and suggested prognostic table. Laryngoscope 1984:94:647-651
- Daniels and others. Causes of unilateral sensorineural hearing loss screened by high-resolution fast spin echo magnetic resonance imaging: review of 1070 consecutive cases. Am. J. otol 21:173-180, 2000
- Eisenman DJ, Arts HH. Effectiveness of treatment for sudden sensorineural hearing loss. Arch Otol HNS 126, 1161-1166, 2000
- Fattori and others.. Sudden hypoacusis treated with hyperbaric oxygen therapy: a controlled study. ENT journal, 80, 9, 655-
- Gianoli GJ, Li JC. Transtympanic steroids for treatment of sudden hearing
loss. Otolaryngol Head Neck Surg 2001 Sep;125(3):142-6
- Haberkamp TJ, Tanyeri HM. Management of sudden
sensorineural hearing loss. AM J. Otol 20:587-595, 1999
- Mattox DE, Simmons FB. Natural history of sudden sensorineural hearing loss. Ann ORL 1977:86:463-480
- Minoda R, Masuyama K, Habu K, Yumoto E. Initial steroid hormone dose in the treatment of idiopathic sudden deafness. Am J. Otol, 2000, 21,819-825
- Stokroos RJ, Albers FWJ, Schirm J. Therapy of idiopathic sudden sensorineural hearing loss; antiviral treatment of experimental herpes simplex virus infection of the inner ear. Ann ORL 108:1999:423-428
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