Further Outpatient Care
Patients who continue to have a significant hearing loss require aural rehabilitation.
Prognosis
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:
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Age younger than 15 years or older than 65 years
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Elevated ESR (>25)
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Vertigo or vestibular changes evident on ENG
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Hearing loss in the opposite ear
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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. [19]
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. [33]
A literature review by Sara et al indicated that bilateral sudden SNHL has a worse recovery rate than does unilateral hearing loss. [17]
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. [34]
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. [35]
A review of outcomes for the various therapeutic regimens produces conflicting results, again because of differences in reporting. With different inclusion criteria, exclusion criteria, recovery criteria, and duration of follow-up, comparisons between studies are often not valid. Many studies lack control subjects.
Several studies using vasodilator therapy as a component of treatment did not show significant differences from placebo. However, in 1996, Fetterman et al reported their best recovery results (63% improved pure-tone average [PTA] by more than 10 dB or speech discrimination more than 15%) when treatment included vasodilators. [36] Based on controlled studies, little data support vasodilator therapy.
Several studies assessing low molecular weight dextrans and/or pentoxifylline did not demonstrate recovery rates better than placebo. One exception by Redleaf et al in 1995 reported 64% of patients improving. [37] In this study, concomitant diatrizoate therapy was also administered, and no placebo arm was used.
Corticosteroid therapy has been investigated with varying outcomes. Published recovery rates range from 41-61%. In 1980, Wilson et al demonstrated a significant improvement, finding 61% improved on oral corticosteroids compared to a 32% improvement rate on placebo. [38] They also stratified their patient groups by audiometric patterns, and determined that hearing losses from 40-90 dB responded better to steroid therapy; 78% improved.
Diatrizoate has not been studied to any great extent. In 1987, Wilkins et al found no significant difference in recovery using diatrizoate in a multidrug regimen compared to spontaneous recovery rates. [39] Redleaf et al reported a beneficial effect using diatrizoate and dextran, improving 64% of patients. [37] Interestingly, using the hearing recovery criteria of Wilkins et al, recalculated data from the 1995 Redleaf study indicated only a 36% recovery rate to a classification of complete or good.
A review of hyperbaric oxygen therapy found a beneficial effect, especially if therapy was instituted within 2-6 weeks of the onset of the hearing loss. Fifty percent of patients improved by 20 decibels. If therapy was delayed, less improvement was found, with no beneficial effect for delays of longer than 3 months.
At an average 8-year follow-up, a study by Härkönen et al indicated that patients who suffered unilateral ISSNHL who had not recovered normal hearing in the affected ear experienced not just lower quality of hearing but also significantly lower quality of life, as well as more tinnitus and greater balance problems, than did patients with unilateral ISSNHL whose hearing did recover to normal. [40]
Patient Education
The American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) guidelines recommend physicians educate patients with sudden hearing loss about the natural history of the condition, the benefits and risks of medical interventions, and the limitations of existing evidence regarding efficacy. Physicians should obtain follow-up audiometry within six months of diagnosis and counsel patients with incomplete hearing recovery about the possible benefits of amplification and hearing assistive technology and other supportive measures. [1]
For excellent patient education resources, visit eMedicineHealth's Ear, Nose, and Throat Center. Also, see eMedicineHealth's patient education article Hearing Loss.
