What is the prognosis of sudden hearing loss?

Updated: Aug 28, 2019
  • Author: Neeraj N Mathur, MBBS, MS, DNB(ENT), MNAMS, FAMS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Fortunately, the spontaneous recovery rates for sudden SNHL are generally good. These rates range from 47-63%, with the caveat that different studies used different criteria for degrees of recovery. Ideally, criteria will be established by which to measure hearing improvement.

Negative prognostic factors include the following:

  • Age younger than 15 years or older than 65 years

  • Elevated ESR (>25)

  • Vertigo or vestibular changes evident on ENG

  • Hearing loss in the opposite ear

  • Severe hearing loss

Prognostic factors affecting outcome in patients with sudden SNHL have been postulated. Vertigo or imbalance seems to portend a lower recovery rate. Two studies, in addition, found severe vertigo associated with more cases of high-frequency or profound hearing loss. This association could be explained anatomically by the close proximity of the basal turn of the cochlea to the vestibule.

A study by Passamonti et al indicated that the presence of hyperhomocysteinemia or cardiovascular risk factors (ie, arterial hypertension, hyperlipidemia, diabetes, smoking) signals worse clinical outcomes in ISSHL. [13]

A study by Lin et al found evidence that in patients with ISSHL, higher ratios of low-density lipoprotein cholesterol (LDL-C) to high-density lipoprotein cholesterol (HDL-C) indicate a poorer prognosis for hearing recovery. According to the study, which involved 166 patients with ISSHL, patients who made a complete recovery had a significantly lower LDL-C/HDL-C ratio than did those who made only minimal recovery. [32]

A literature review by Sara et al indicated that bilateral sudden SNHL has a worse recovery rate than does unilateral hearing loss. [11]

A study by Lee et al indicated that in cases of sudden SNHL caused by intralabyrinthine hemorrhage (ILH), the prognosis is worse than in ISSNHL, ie, non-ILH cases. Patients whose condition arose from ILH had a worse final recovery threshold than did the other patients, and they apparently achieved hearing recovery at high frequencies (2000, 4000, 8000 Hz) less often than at low frequencies (250, 500, 1000 Hz). Moreover, 92% of the ILH patients complained of dizziness. The study included 35 patients, including 12 with ILH. [33]

Considerable controversy exists regarding the prognosis in sudden hearing loss. Existing studies have not provided answers to questions regarding spontaneous recovery rate, the best therapeutic regimen, prognostic factors in recovery, and the pathophysiology of sudden hearing loss. These are questions that require a randomized controlled clinical trial of adequate size. Given the apparent rate of spontaneous recovery, the prognosis for some hearing recovery for patients with sudden SNHL is moderate. Selection bias is likely to affect most studies of ISSHL because patients with sudden hearing loss and spontaneous recovery within a few days probably do not seek medical evaluation. The true spontaneous recovery rate is unknown.

A retrospective study by Kang et al indicated that prognostic factors for recovery from ISSNHL include patient age, the extent of the initial hearing loss, the initial speech discrimination score, the initial pure tone threshold, and the period of time between the start of symptoms and the beginning of treatment. [34]


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