Sudden Hearing Loss Causes and Considerations

Definition and Classification

Sudden hearing loss is defined as a rapid onset, occurring over a 72-hour period, of a subjective sensation of hearing impairment in one or both ears 1
It can be classified as conductive hearing loss, sensorineural hearing loss, or mixed hearing loss, with sensorineural hearing loss involving the cochlea, auditory nerve, or central auditory processing 3

The majority of sudden hearing loss cases (90%) are idiopathic, with the most concerning non-idiopathic causes being vestibular schwannoma (acoustic neuroma), stroke, and malignancy, according to the American Academy of Otolaryngology-Head and Neck Surgery 1
Vestibular schwannoma (acoustic neuroma) and other malignancies affecting the auditory pathway are identifiable causes of SSNHL 1

Emergency intervention may be needed for rare, life-threatening conditions presenting with SSNHL, and prognosis for recovery depends on several factors, including patient age, presence of vertigo at onset, degree of hearing loss, audiometric configuration, and time between onset and treatment, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 1
In up to one-third of cases, the cause may only be identified during long-term follow-up 4

Initial evaluation should distinguish between conductive and sensorineural hearing loss, and audiometric testing is essential to confirm SSNHL, defined as ≥30 dB hearing loss at 3 consecutive frequencies 3
Patients should be assessed for bilateral hearing loss, recurrent episodes, or focal neurologic findings, and MRI, auditory brainstem response, or audiometric follow-up is recommended to evaluate for retrocochlear pathology 2

A maximum of 32-65% of SSNHL cases may recover spontaneously, and early intervention may improve hearing recovery and quality of life 1
Corticosteroids (systemic or intratympanic) are commonly used as initial therapy, and long-term follow-up is important as some patients will have an underlying cause identified later 2

Delaying diagnosis and treatment, missing life-threatening causes, inadequate follow-up, and overlooking SSNHL in intensive care settings can be detrimental to patient outcomes, as warned by the American Academy of Otolaryngology-Head and Neck Surgery 5