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Key Points
Î Sudden hearing loss (SHL) is a frightening symptom that often
prompts an urgent or emergent visit to a clinician. This guideline
update focuses on sudden sensorineural hearing loss (SSNHL), the
majority of which is idiopathic and which, if not recognized and
managed promptly, may result in persistent hearing loss and tinnitus
and reduced patient quality of life (QOL). SSNHL affects 5–27 per
100,000 people annually, with about 66,000 new cases per year in the
United States.
Î SHL is defined as a rapid-onset subjective sensation of hearing
impairment in one or both ears. The hearing loss in SHL may be
conductive (CHL), sensorineural (SNHL), or mixed (MHL), defined as
both CHL and SNHL occurring in the same ear. CHL and the conductive
component of MHL may be due to an abnormality in the ear canal,
tympanic membrane ('ear drum'), or middle ear.
• Physical examination will help determine if there is obstructing cerumen or a
foreign body in the ear canal, if there is a perforation of the tympanic membrane,
or if there is fluid in the middle ear.
• Tuning fork testing will enable the initial treating clinician to distinguish CHL
from SNHL, so that the SSNHL evaluation and management (E&M) pathway
can be triggered appropriately.
Î SSNHL is a subset of SHL that is: a) sensorineural in nature, b) occurs
within a 72-hour window, and c) meets certain audiometric criteria.
• SNHL is sometimes referred to colloquially as 'nerve hearing loss' and indicates
abnormal functioning of the cochlea, auditory nerve, or higher aspects of central
auditory perception or processing.
• The most frequently used audiometric criterion for SSNHL is a decrease in
hearing of greater than or equal to 30 decibels affecting at least 3 consecutive
frequencies. Because premorbid audiometry is generally unavailable, hearing loss is
often defined in relation to the opposite ear's thresholds.
• The CPG update group acknowledges that in both clinical practice and in research
studies, less stringent criteria for SSNHL are employed.
• SSNHL is often but not always accompanied by tinnitus and/or vertigo. The
tinnitus may persist and may be disturbing to the patient.
Î Idiopathic sudden sensorineural hearing loss (ISSNHL) is defined
as SSNHL with no identifiable cause despite adequate investigation.
This is the situation in 90% of patients with SSNHL and is the primary
focus of this CPG update. The use of SSNHL in this document refers
to ISSNHL, after the appropriate workup has been done as denoted in
KAS 1 and KAS 2.
