Sudden deafness is a severe sensorineural hearing loss that develops within a few hours or is felt on waking. It affects about 1/5000 people every year. The initial hearing loss is typically unilateral (other than drug-induced) and can be mild to severe. Many also experience tinnitus, and some faint, feel dizzy, or both.
Some of the causes of sudden deafness are different from the causes of chronic hearing loss, and must be addressed urgently.
The general characteristics of sudden deafness are:
Most cases are idiopathic.
Some cases arise during events that clearly explain them.
A few represent the initial sign of an occult disease that can be detected.
Idiopathic: There are a number of theories, some of which have some (albeit contradictory and incomplete) evidence. The most promising are the possibilities of viral infections (especially herpes simplex), autoimmune attacks and acute microvascular occlusion.
Obvious events: Some causes of sudden deafness are obvious.
A blunt head injury with a fracture of the temporal bone or a severe concussion affecting the cochlea can cause sudden deafness.
Large changes in environmental pressure (e.g., when diving) or strenuous activities (e.g., lifting weights) can cause a peri lymphatic fistula between the middle and inner ear and cause sudden, severe symptoms. Peri lymphatic fistula can also be congenital, which can spontaneously cause sudden hearing loss, or it can occur after an injury or pressure change.
Ototoxic drugs can cause hearing loss, sometimes after one day, especially with an overdose (systemic or after application to a large area of the wound, such as a burn). There is a rare gene disorder transmitted by mitochondria that increases susceptibility to aminoglycoside ototoxicity.
A number of infections cause sudden deafness during or immediately after an acute illness. Common causes include bacterial meningitis, Lyme disease, and viral infections that affect the cochlea (and sometimes the vestibular apparatus). The most common viral causes in industrialized countries are mumps and herpes. Measles is a rare cause because most of the population is vaccinated.
SOME CAUSES OF SUDDEN DEAFNESS
- Idiopathic causes
- OBVIOUS EVENTS
- Acute infections (e.g., bacterial meningitis, mumps, herpes)
- Severe head or ear injury (including barotrauma due to deep diving causing peri lymphatic fistula)
- Ototoxic drugs (e.g., aminoglycosides, vancomycin, cisplatin, furosemide, ethacrynic acid) *
- HIDDEN DISEASES
- Acoustic neuroma
- Autoimmune diseases (e.g., Cogan syndrome, vasculitis)
- Cerebellar stroke
- Meniere’s disease
- Multiple sclerosis
- Reactivation of syphilis in an HIV-infected patient
- Loss usually occurs within one or several days.
Processing consists of detecting hearing loss, assessing its severity, and determining the etiology (especially reversible causes).
The current medical history should confirm that the loss is sudden and not chronic. A medical history should also record whether the loss is unilateral or bilateral, and whether there is an acute event (eg head injury, barotrauma [especially diving injury], infectious disease). Important concomitant symptoms are other ear-derived symptoms (e.g., tinnitus, ear discharge), vestibular symptoms (e.g., disorientation in the dark, dizziness), and other neurological symptoms (e.g., headache, weakness, or facial asymmetry, impaired taste sensation).
Looking at other organ systems should look for symptoms of possible causes, including transient, migrating neurological outbursts (multiple sclerosis) and eye irritation and redness (Cogan syndrome).