From the Guidelines
Sudden unilateral sensorineural hearing loss (SNHL) in adults is most commonly caused by idiopathic sudden sensorineural hearing loss (SSNHL), which affects 5 to 27 per 100,000 people annually, with about 66,000 new cases per year in the United States 1. The primary causes of sudden unilateral SNHL include:
- Idiopathic SSNHL, which accounts for 90% of cases and is defined as SSNHL with no identifiable cause despite adequate investigation 1
- Viral infections, particularly herpes viruses
- Vascular events that reduce cochlear blood flow
- Ménière's disease, characterized by vertigo and tinnitus
- Acoustic neuromas, benign tumors
- Autoimmune inner ear disease
- Physical blockages like impacted earwax or foreign bodies Less common causes include:
- Multiple sclerosis
- Stroke affecting the auditory pathways
- Head trauma
- Ototoxic medications, such as certain antibiotics and chemotherapy drugs
- Perilymphatic fistula It is essential to note that the inner ear's delicate structures and limited blood supply make it particularly vulnerable to damage, which explains why many of these conditions can cause rapid hearing deterioration 1.
Key Considerations
- Prompt recognition and management of sudden sensorineural hearing loss may improve hearing recovery and patient quality of life 1
- The guideline update group recognized that patients enter the health care system with sudden hearing loss as a nonspecific primary complaint, and therefore, the initial recommendations address distinguishing sensorineural hearing loss from conductive hearing loss at the time of presentation with hearing loss 1
- Early intervention within 72 hours is crucial for optimal treatment outcomes, and patients should seek immediate medical evaluation if they experience sudden hearing loss 1.
From the Research
Causes of Sudden Unilateral Sensorineural Hearing Loss (SNHL) in Adults
- The exact causes of sudden unilateral sensorineural hearing loss (SNHL) in adults are often unknown, but it is believed to be related to inflammation of the cochlea 2.
- Some studies suggest that SSNHL may be caused by various factors, including inner ear hair cell loss, but the differential for SSNHL is vast and for the majority of patients an etiologic factor is not identified 3.
- The etiological workup aims at treating known causes, while different pathophysiological hypotheses exist for idiopathic SSNHL 4.
Factors Affecting Prognosis
- The prognosis for hearing recovery for idiopathic SSNHL is dependent on a number of factors including the severity of hearing loss, age, presence of vertigo, and shape of the audiogram 3.
- Factors like age of the patient, gender, degree of hearing loss and duration of symptoms at initial presentation can affect the response to treatment, with patients who presented earlier after the onset of disease and the patients who had milder degree of hearing loss at presentation having a better response to therapy 2.
- Patients with pretreatment hearing grade 3 had the highest improvement rate (88.2% or 30/34) when treated with combined systemic and intra-tympanic steroid therapy 5.
Treatment and Recovery Outcomes
- Steroid therapy is the current mainstay of treatment of idiopathic SSNHL in the United States 3.
- Oral corticosteroid therapy is a good therapeutic option for the treatment of sudden sensorineural hearing loss (SSHNL) 2.
- Application of steroid medication significantly improves the recovery outcomes in cases of Severe Sudden Sensorineural Hearing Loss 6.
- Hearing improvements (complete recovery, partial recovery, slight improvement) were seen in 56 patients treated with combined intra-tympanic steroid therapy, with patients who received the combined steroid therapy as the initial modality having a better overall hearing improvement rate than did the salvage group 5.