Sudden sensorineural hearing loss (SSNHL) develops over a period of hours or a few days and loss may be partial or complete.
Though mostly unilateral, it may affect both ears.
SUDDEN SNHL is defined as a hearing loss that should be a 30 dB sensorineural loss in at least 3 consecutive frequencies occurring over a period of 72 hours.
The patient may have associated symptoms of tinnitus and a temporary spell of vertigo.
What Are the Causes of Sudden Hearing Loss?
- In most of the cases, it is IDIOPATHIC as the cause remains obscure in 85-90% of the cases.
- Three etiological factors speculated are Viral, Vascular, and the Rupture of cochlear membranes.
- Spontaneous formation of perilymph fistulae in the oval or round window can occur.
The cause of sudden hearing loss are listed below —-
1) Infections: Mumps, herpes zoster, meningitis, encephalitis, otosyphilis, Lyme disease, otitis media.
2) Trauma: Head injury, ear operations, noise trauma, barotraumas(dividing and ascending), and spontaneous rupture of cochlear membranes.
3) Vascular: Hemorrhage(leukemia), embolism, thrombosis, and spasm of the labyrinthine or cochlear artery.
Risk factors include diabetes, hypertension, polycythemia, macroglobulinemia, and sickle cell trait.
4) Ototoxic drugs: Aminoglycoside, analgesics, antimalarial, chemicals (alcohol, tobacco, marijuana), loop diuretics.
5) Tumors: Acoustic neuroma, metastases in the cerebellopontine angle, carcinomatous neuropathy.
6) Miscellaneous: Meniere’s disease, Cogan syndrome, Multiple sclerosis, Hypothyroidism, Sarcoidosis.
What Are The Symptoms Of Sudden Deafness?
- Sudden muffled hearing in one ear
- Fullness or stuffed or clogged ears
- Dizziness
- Loss of sensation in the pinna of the ear (the soft part of the earlobe)
- Ear balance problems or vertigo
- Tinnitus or ringing in the ears
- Difficulty in hearing high-pitched sounds or High-frequency hearing loss
Clinical features of Sudden Hearing Loss:
- Sudden sensorineural hearing loss develops over a period of hours or a few days.
- Hearing loss may be partial or complete.
- Though mostly unilateral, it may affect both ears.
- The patient may have associated symptoms of tinnitus and a temporary spell of vertigo.
- Upper respiratory infections within 1 month of hearing loss.
The cause of hearing loss should be discovered by detailed history and physical examination including audiometry.
How Is Sudden Hearing Loss Identified?
1. Laboratory Tests:
The following laboratory investigations may be ordered to confirm the cause, which is suspected on the basis of history and physical examination, and audiometry findings:-
- CBC
- ESR,
- Tests for syphilis,
- Diabetes,
- Hypothyroidism,
- Blood disorders and
- Lipid profiles and
- Vestibular tests.
2. Gadolinium-enhanced MRI
It is indicated on the suspicion of ACOUSTIC NEUROMA.
Though only 1-3% of SSNHL is due to acoustic neuroma, about 10% of acoustic neuroma patients present with SSNHL.
3. Perilymph Fistula
Exploratory tympanostomy may be done where perilymph fistula is strongly suspected.
What Are the Treatments for Sudden Hearing Loss?
As the cause often remains obscure, the treatment also remains empirical.
Though CORTICOSTEROID THERAPY is the mainstay vasodilator, diuretics, anticoagulants, and thrombolytic agents have also been tried.
In addition to bed rest, treatment consists of the following elements:
1) Steroid therapy:
Prednisolone 40–60 mg in a morning dose for 1 week and then tapered off in a period of 3 weeks.
Steroids relieve edema as they have an anti-inflammatory effect.
They are of particular use in hearing loss of a moderate degree.
Steroids if delayed for more than 2 weeks to 4 weeks are LESS LIKELY to reverse or reduce permanent hearing loss.
2) Intratympanic steroids:
They have been tried when oral steroids failed to give satisfactory results or in diabetes and psychiatric disorders where systemic steroids can exacerbate the conditions.
The current reports have observed that intratympanic injection of steroids was as effective as oral steroids.
3) Antivirals such as acyclovir.
4) Inhalation of carbogen (5% CO2 + 95% O2):
It increases cochlear blood flow and provides better oxygenation.
5) Low molecular weight Dextran:
The infusions decrease blood viscosity. It is contraindicated in cardiac failure and bleeding disorders.
6) Hyperbaric oxygen therapy:
If given in the first month of the onset of hearing loss, some benefits have been seen.
7) General measures: Low salt diet and bed rest.
8) Other agents :
Vasodilators, diuretics, anticoagulants, and thrombolytic agents have also been found helpful in some studies.
9) Hearing aids/cochlear implants:
If the hearing loss is severe, does not respond to treatment, and/or bilateral hearing aids or cochlear implants may be required.
Prognosis:
About 50% of patients recover spontaneously within 15 days.
The chances of recovery are less after one month.
Good prognostic factors:
They include young adults, moderate and low-frequency hearing loss, lack of vertigo, and early treatment.
Poor prognostic factors:
They include old age, profound deafness, the presence of vertigo, vascular risk factors, and delayed treatment.