Hearing loss

Abstract

We investigated the prognostic significance of the presence or absence of vertigo and tinnitus, the timing of the initiation of treatment, the type and severity of hearing loss, and age in 72 patients who had experienced sudden hearing loss. We found that the factors associated with a positive prognosis were the absence of vertigo, the presence of tinnitus, initiation of treatment within 7 days, a greater degree of hearing loss in the low frequencies, and a hearing loss of less than 45 dB. Age had no effect on prognosis.

Introduction

Sudden hearing loss is defined as a sensorineural hypoacusis of at least 30 dB in 3 consecutive speech frequencies that has occurred within the previous 3 days. (1,2) Its worldwide incidence has been reported to range from 5 to 20 cases per 100,000 population. (2) The reported incidence is lowest in patients aged 20 to 30 years (4.7 per 100,000) and highest in those aged 50 to 60 years (15.8 per 100,000). (3) Since some patients experience a spontaneous resolution of their deafness and therefore do not seek treatment, the actual incidence is higher. (2) Sudden hearing loss affects the two sexes equally. Approximately 90% of cases are unilateral. (4)

Studies of the etiology of sudden hearing loss have focused on four possible causes: (1) circulatory anomalies (e.g., thrombosis, vasospasm, and embolism), (2) viral labyrinthitis or viral infection of the cochlea, (3) irregularities of the cochlear membrane, and (4) autoimmune disorders. (4) Support exists for each of these explanations, but the most popular theory is that sudden deafness is caused by a disturbance of the cochlear blood flow. (5) Support for this theory is based on histopathologic findings, the suddenness of the hearing loss, and the fact that affected patients often have concomitant vascular disease. (6,7)

Many studies have been conducted to identify factors that may have a positive or negative effect on patients with sudden hearing loss. (3,8-10) We conducted our own study to test the reliability of these previously investigated variables.

Patients and methods

Between Jan. 2, 1999, and Dec. 31, 2002, 107 patients were diagnosed with sudden hearing loss in the Department of Otorhinolaryngology at the Cerrahpasa Medical School and at a private hyperbaric oxygen therapy center. Of this group, 72 patients had been treated with 1 mg/kg of fluocortolone with dose reductions of 10 mg every 3 days, 100-mg ampules of pentoxifylline three times a day for 15 days, 500 ml of dextran once a day for 3 days, and hyperbaric oxygen therapy for 2 weeks. These 72 patients--39 males (54.2%) and 33 females (45.8%), aged 10 to 72 years (mean: 36.94 [+ or -] 15.24)--were included in our study; the remaining 35 patients received different treatment and were not included.

We investigated the prognostic significance of the presence or absence of vertigo and tinnitus, the timing of the initiation of treatment, the type and severity of hearing loss, and age. To that end, we obtained a history from each patient, with emphasis on how and when the hearing loss had begun, the presence or absence of accompanying vertigo and tinnitus, and the onset of treatment. Patients also underwent audiometry (125 to 8,000 Hz) and tympanometry, as well as determinations of speech perception thresholds, speech discrimination scores, and acoustic reflexes. Magnetic resonance imaging (MRI) of the cranium was performed on all patients. We also performed routine ENT and otoneurologic examinations and ordered biochemical testing, which included measurements of the total blood count, erythrocyte sedimentation rate, C-reactive protein level, prothrombin time, activated partial thromboplastin time, bleeding and coagulation times, aspartate and alanine transaminase levels, blood lipid concentrations, thyroid function, rheumatoid factor level, and antinuclear antibody level. In addition, serologic investigations for hepatitis B and C virus, human immunodeficiency virus (HIV), and syphilis were obtained.

We classified patients into various groups according to possible prognostic factors:

* vertigo-positive and vertigo-negative patients

* tinnitus-positive and tinnitus-negative patients

* patients whose treatment had been initiated within 7 days of the onset of sudden hearing loss and those who had been treated 8 days afterward or beyond

* patients with specific types of hearing loss as determined by audiometric curve patterns: ascending (hearing loss greater at the lower frequencies), flat, descending (hearing loss greater at the higher frequencies), and total

* age: two primary age groups ([less than or equal to] 40 and [greater than or equal to] 41 yr), further subclassified into five secondary groups ([less than or equal to] 15 yr, 16 to 30, 31 to 45, 46 to 60, and [greater than or equal to] 61)

We then determined the degree of hearing recovery in each group. (11) Recovery was rated on a scale of 1 to 4:

* 1: complete recovery (hearing threshold: <20 dB)

* 2: moderate recovery (hearing gain: [greater than or equal to] 30 dB)

* 3: slight recovery (hearing gain: 11 to 29 dB)

* 4: no recovery (hearing gain: 0 to 10 dB)

Statistical comparisons among groups were based on the Mann-Whitney U test and the Kruskal-Wallis test. Because deviations in hearing loss and gain were wide and determinations of hearing gain were based on an artificially precise recovery score, we also compared groups according to nonparametric tests. In addition, we also used nonparametric tests in cases in which the number of patients in a group was small (e.g., the [greater than or equal to] 61-yr age group; n = 3). As a result, our data were calculated as both median values and as standard deviations from the mean. The chi-square test was used to compare categoric parameters with each other.

Results

None of the serology tests for hepatitis B and C virus, HIV, and syphilis was positive. No acoustic neuroma was found on MRI.

Vertigo. Hearing recovery was significantly better in the vertigo-negative group (p < 0.05) (table 1).

Tinnitus. The presence of tinnitus was associated with significantly greater hearing recovery (p < 0.05) (table 1).

Time to treatment. Patients who had begun treatment 7 days or earlier after the onset of their hearing loss experienced significantly greater recovery (p < 0.05) (table 1).

Type of hearing loss. Significantly better recovery was seen in patients with ascending curves than in those with flat audiograms, descending curves, and total hearing loss (all p < 0.05) (table 1). No significant differences were seen among the groups with flat audiograms, descending curves, and total hearing loss.

Severity of hearing loss. Analysis of recovery rates according to specific measurements of the severity of hearing loss (i.e., 30 to 45 dB, 46 to 90 dB, and [greater than or equal to] 91 dB) revealed a statistically significant difference in favor of those with less severe hearing loss (p < 0.01) (table 2).

Age. Analysis of recovery according to the five age subcategories revealed no significant differences among groups (table 1). Analysis of patients according to the two primary age categories ([less than or equal to] 40 and [greater than or equal to] 41 yr) showed that the mean hearing gain was 28.21 dB ([+ or -] 26.54) in the younger group and 21.53 dB ([+ or -] 24.29) in the older group--not a statistically significant difference. Among the 42 patients in the younger group, recovery was complete in 14 (33.3%), moderate in 8 (19.0%), and slight in 5 (11.9%); 15 of these patients (35.7%) experienced no recovery. Corresponding figures among the older group (n = 30) were 12 (40.0%), 7 (23.3%), 4 (13.3%), and 7 (23.3%). Again, no statistically significant difference in recovery rates was seen between the two primary age groups.

Discussion

Although sudden hearing loss has been an ongoing problem throughout history, its etiopathogenesis is still not completely clear. More than 100 possible causes have been implicated over the years, but most cases remain idiopathic. (3,12) Many studies of the prognosis of affected patients have centered on the same parameters that we investigated in our study: the presence or absence of vertigo and tinnitus, the timing of the initiation of treatment, the type and severity of hearing loss, and age. (3,8-10)

The presence of vertigo, which has been reported to occur in as many as 40% of patients with sudden hearing loss, has previously been shown to be a negative prognostic factor. (8,13) Affected patients usually complain of aural fullness, pressure, and awareness of a humming sound. (3,7,12) Moskowitz et al reported that the presence of vertigo indicates a poor prognosis; they found that only 14% of patients they studied achieved a complete recovery of hearing. (8) Shiraishi et al reported a complete, moderate, or slight recovery in 40% of vertiginous patients with sudden hearing loss. (14) Saeki and Kitahara reported a complete, moderate, or slight recovery in 70% of patients with no vertigo and no abnormal findings on electronys-tagmography. (9) Our findings are consistent with those in these previous reports. In our study, 26 of the 72 patients (36.1%) were vertigo-positive, and only 6 of them (23.1%) achieved a complete recovery. However, almost one-half of the 46 vertigo-negative patients experienced only a slight recovery or none at all.

Tinnitus has been reported to accompany sudden hearing loss in 75% of patients, and its presence is considered to be a positive prognostic indicator. (9) Our findings were consistent with those in the literature, as tinnitus was present in 53 of our patients (73.6%), and a complete recovery was achieved in a significantly greater proportion of patients who had tinnitus (37.7%) than in those who did not (10.5%). Even so, more than one-half of our tinnitus-positive patients experienced only a slight recovery or none at all.

It is a common opinion that the treatment of sudden hearing loss should generally begin within 10 weeks. As one would expect, earlier treatment is associated with a better prognosis. (8,10,15,16) All patients in our study had come to us within 1 month of the onset of sudden hearing loss; 50 of them (69.4%) had presented to us during the first 7 days. This figure is consistent with those reported by Shiraishi et al (14) and Kronenberg et al. (17) Shaia and Sheehy reported that a complete, moderate, or slight recovery was achieved in 75% of patients who had been treated with a vasodilator within 7 days; the recovery rate dropped to 53% among those who had presented 1 week to 1 month after the onset of their hearing loss. (10) Likewise, Moskowitz et al reported a 56% rate of complete, moderate, or slight recovery with steroid treatment within 7 days and a 27% recovery rate thereafter; they also noted that recovery occurred in 68% of patients who were treated within 3 days. (8) Finally, Byl reported a first-week recovery rate of 56%. (3) The recovery rates of patients who had been treated during the first week in our study were both at variance with and consistent with those reported by others. We observed a complete recovery in 19 of the 50 patients (38.0%) who had been treated during the first week (vs. 56% reported by Byl (3)), while 35 patients (70.0%) experienced either a complete, moderate, or slight recovery (vs. 75% reported by Shaia and Sheehy (10) and 56% reported by Moskowitz et al (8)). Also in our study, 11 of 22 patients (50.0%) who had been treated beyond 1 week of the onset of sudden deafness experienced no recovery, a rate that is consistent with the failure rate of 53% reported by Shaia and Sheehy. (10) Overall, our findings with respect to the benefit of early treatment are consistent with those reported in the literature.

Others have reported that the prognosis is good for patients whose audiogram curves are ascending or flat and poor for those with descending curves. (5,8,18,19) Reported rates of spontaneous recovery at low frequencies (ascending curves) range from 40 to 66%. (3) We also found that patients with ascending curves experienced significantly better recovery than did those with other audiographic findings.

Recovery is also influenced by the severity of sudden hearing loss. (8) Ustun et al reported that the prognosis for recovery was very poor in patients whose hearing loss was total. (16) Kronenberg et al found that only 22% of patients with a total hearing loss experienced a complete, moderate, or slight recovery following treatment with a vasoactive agent. (17) Shiraishi et al reported a complete, moderate, or slight recovery in 38% of patients with a severe hearing loss. (14) Byl reported complete, moderate, or slight recovery in 83% of patients with a severe heating loss and only 22% among those with a total hearing loss following steroid treatment. (3) Again, our findings were consistent with those in the literature. (3,17) We observed no recovery in 12 of 15 patients (80.0%) with a total hearing loss (the remaining 3 patients experienced a moderate recovery). On the other hand, all 7 of our patients whose hearing loss was in the range of 30 to 45 dB recovered completely. Recovery rates among those whose hearing loss was more severe were significantly worse. Again, our findings are consistent with those of others.

No consensus exists in the literature as to the prognostic importance of age. Megighian et al found that the highest incidence of sudden hearing loss occurred in patients aged 30 to 60 years, and they suggested that age is a prognostic factor. (15) Others consider age to be irrelevant. (8) We also found the highest incidence of sudden hearing loss occurred in patients aged 31 to 60 years (62.5%), but the difference between this group and other age groups was not statistically significant.

In conclusion, we found that a good prognosis for patients with sudden heating is associated with the absence of vertigo, the presence of tinnitus, early treatment, a hearing loss in the lower frequencies, and a hearing loss of 45 dB or less. We found no evidence to suggest that age has any influence on prognosis.

References

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(17.) Kronenberg J, Almagor M, Bendet E, Kushnir D. Vasoactive therapy versus placebo in the treatment of sudden hearing loss: A double-blind clinical study. Laryngoscope 1992;102:65-8.

(18.) Mattox DE, Lyles CA. Idiopathic sudden sensorineural hearing loss. Am J Otol 1989;10:242-7.

(19.) Menotti A, Kromhout D, Blackburn H, et al. Food intake patterns and 25-year mortality from coronary heart disease: Cross-cultural correlations in the Seven Countries Study. The Seven Countries Study Research Group. Eur J Epidemiol 1999;15:507-15.

Aydin Mamak, MD; Suleyman Yilmaz, MD; Harun Cansiz, MD; Ender Inci, MD; Ender Guclu, MD; Levent Derekoylu, MD

From the Department of Otorhinolaryngology, Cerrahpasa Medical School, University of Istanbul.

Reprint requests: Suleyman Yilmaz, MD, Istanbul Universitesi Cerrahpasa, Tip Fak KBB ABD, Istanbul, Turkey. Phone: 90-216-576-7012; fax: 90-216-469-5338; e-mail: dryilmazsuleyman@yahoo.com

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