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Hearing
Loss: A Merck Manual of Patient Symptoms podcast
Sudden deafness
is severe sensorineural hearing loss that develops within a few
hours. It affects about 1/5000 people each year.
Sudden deafness has causes that differ from chronic hearing loss and must be addressed urgently.
Etiology
Mechanical causes include blunt head trauma with fracture or hemorrhage involving the cochlea. Large ambient pressure changes or strenuous activities, such as weight lifting, can induce a perilymphatic fistula between the middle and inner ear.
Infectious causes include mumps and measles. Other causative viruses include influenza, varicella, adenoviruses, and Epstein-Barr virus. Lyme disease is a rare cause.
Vascular disorders involving the terminal branch of the anterior inferior cerebellar artery cause ischemia of the 8th cranial nerve in rare cases. Diseases include Waldenström's macroglobulinemia, sickle cell disease, and some forms of leukemia.
Ototoxic drugs (see Inner Ear Disorders: Drug-Induced Ototoxicity) can result in hearing loss occurring within a day, especially if with overdose, systemically or when applied to a large wound area, such as a burn. There is a rare genetic mitochondrial-transmitted disorder that increases the susceptibility to aminoglycoside ototoxicity.
Idiopathic sudden deafness may involve occult viral or bacterial infections; head trauma; autoimmune disorders, such as Cogan's syndrome; toxic causes, such as snake bites; ototoxic drugs; circulatory problems; neurologic causes, such as multiple sclerosis; increased intracranial pressure; brain tumors; hyperlipidemia; and Meniere's disease.
Symptoms and Signs
Initial hearing loss may initially range in severity from mild to profound. A patient with perilymphatic fistula may hear an explosive sound in the affected ear when the fistula occurs and experience vertigo, nystagmus, and tinnitus. Viral infections may manifest only as hearing loss but can be associated with vertigo, nausea, or vomiting.
Diagnosis
Traumatic, ototoxic, and some infectious causes are usually apparent clinically. Other causes require a complete medical history. All patients should undergo an initial examination of the ear canal and tympanic membrane. Unless the diagnosis is determined from the history and physical examination, the patient should undergo an audiogram. If a perilymphatic fistula is suspected clinically, it may be confirmed by tympanometry and electronystagmography (ENG). Additional tests that may be needed include MRI, CBC with differential, ESR, antinuclear antibody, and tests for hypercoagulability.
The fistula may be demonstrated by combining the pressure changes in the ear canal used in tympanometry with ENG. Nystagmus resulting from pressure changes in the ear canal can be detected by ENG and suggests a perilymphatic fistula.
Treatment
Treatment addresses the underlying disorder. Perilymphatic fistulas require surgical exploration and repair of the defect; hematologic abnormalities require correction.
In viral and idiopathic cases, the deficit returns to normal in most patients and is partially recovered in others. In those patients who recover their hearing, improvement usually occurs within 10 to 14 days. Glucocorticoids are used mainly in patients with autoimmune disorders such as Cogan's syndrome. Glucocorticoids and antiviral drugs may also be helpful for patients with an idiopathic sudden sensorineural hearing loss.
Last full review/revision January 2007 by Robert J. Ruben, MD
Content last modified January 2007
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