A study of prognostic factors in sudden hearing loss

Ear, Nose & Throat Journal, Oct, 2005 by Aydin Mamak, Suleyman Yilmaz, Harun Cansiz, Ender Inci, Ender Guclu, Levent Derekoylu

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)