Sudden hearing loss, also known as sudden deafness, is defined as a sensorineural hearing loss of more than 30 dB in three or more consecutive frequencies occurring within less than 72 hours. Many patients notice hearing loss instantly upon waking in the morning, while others perceive it over the course of a few hours. The severity of the loss varies from patient to patient and usually affects only one ear.
Along with hearing loss, patients often experience tinnitus (ringing in the ear), and up to 40% report vertigo.
Epidemiology
Sudden hearing loss is estimated to occur in 5 to 20 per 100,000 people per year, accounting for 1% of all sensorineural hearing loss cases. It occurs equally in men and women, can affect people of any age, but is most commonly seen in individuals over the age of 40.
Causes of Sudden Hearing Loss
There are many potential causes of sudden hearing loss, including:
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- Infections
- Vascular problems
- Cochlear hydrops
- Tumors
- Trauma
- Metabolic disorders
- Hematological disorders
- Neurological disorders
- Immune system disorders
- Toxins
- Idiopathic (unknown cause) – For idiopathic cases, several theories have been proposed, such as:
- Viral labyrinthitis
- Labyrinthitis due to vascular compromise
- Immune-mediated inner ear disease
- Rupture of intracochlear membranes
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Unfortunately, in 70% of cases, despite an exhaustive search for possible causes, none are identified.Audiometry Findings
Sensorineural hearing loss in the right ear. Normal hearing in the left ear.
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Audiometría: Hipoacusia neurosensorial del oído derecho. Oído izquierdo normal
Diagnosis
Diagnostic evaluation begins with a comprehensive medical history to identify potential causes. A physical examination, including otoscopy, is performed to rule out conductive causes such as earwax blockage or serous otitis media.
Hearing tests include:
- Tuning fork tests (acumetry)
- Impedance audiometry
- Pure-tone audiometry (the most important test for confirming sensorineural hearing loss)
Additional tests that provide valuable information:
- Speech audiometry
- Otoacoustic emissions (OAE)
- Auditory brainstem response (ABR)
Additional Tests
Blood tests are often performed to diagnose underlying metabolic, autoimmune, or infectious diseases such as syphilis or Lyme disease, depending on clinical suspicion.
A cranial MRI is also recommended to rule out acoustic neuroma, a benign tumor that presents with hearing loss in 2% of cases.
Treatment of Sudden Hearing Loss
Since the cause is unknown in most cases, treatment remains controversial. However, about one-third of patients recover hearing spontaneously.
Early treatment is recommended, as the response varies. The most widely accepted treatments due to their efficacy include:
- High-dose systemic corticosteroids
- Intratympanic corticosteroids, either alone or in combination with systemic corticosteroids, or as a rescue therapy if there is no favorable response
- Hyperbaric oxygen therapy, which has proven effective, especially when initiated within the first six weeks after symptom onset
Prognosis
Several factors are associated with poor recovery, including:
- Age (patients under 15 and over 65 have worse prognosis)
- Delayed treatment initiation
- Severity of hearing loss
- Presence of additional symptoms like vertigo
Finally, patients should be followed up for at least 12 months with audiometric evaluations. In cases of partial recovery or no recovery, hearing aids or cochlear implants may be considered as treatment options.