ABSTRACT
Previous studies have shown that patients with acoustic neuroma (AN) sometimes present with sudden sensorineural hearing loss (SSNHL) as an initial symptom. The purpose of this research was to investigate the clinical characteristics, diagnosis and treatment of AN in patients diagnosed as SSNHL initially. A total of 10 patients presented with SSNHL as the initial symptom and diagnosed as AN by magnetic resonance imaging (MRI) finally were enrolled in this study. Patient demographics, associated complaints (mostly tinnitus and vertigo), severity of hearing loss, audiogram configurations, auditory brainstem response (ABR) and MRI examination were reviewed and analyzed. Treatment outcome and management protocols were also included in this study. These patients exhibited varying severity of hearing loss and a variety of audiogram configurations. All patients showed an abnormal ABR. According to the Koos grading standard, there were 5 grade I (intracanalicular) tumors, 3 grade II tumors and 2 grade III tumors. The treatment outcome revealed that 2 patients exhibited recovery of the average hearing of impaired frequency by more than 15 dB, and 6 patients showed no recovery. Four patients were referred to undergo surgical treatment after being diagnosed with AN, 1 patient accepted stereotactic radiation therapy, and the remaining 5 patients were taken “waiting and scan” strategy. The findings of this study show that hearing recovery after corticosteroid treatment for SSNHL does not exclude the presence of AN and all patients diagnosed as SSNHL initially should undergo MRI and ABR to prevent misdiagnosis and delays in potential treatment.
1. Introduction
Sudden sensorineural searing loss (SSNHL) is defined as a rapid-onset sensorineural hearing loss of ≥20 decibels (dB), affecting at least 2 consecutive frequencies that occurred within 72h with no identifiable cause [1]. The incidence of SSNHL is reported to be 5–20 per 100,000 individuals, with about 66,000 new cases per year in the United States [2]. An epidemiological survey in Japan revealed that the incidence of SSNHL was 60.9 per 100 000 population [3]. In China, the prevalence of SSNHL has been on the rise in recent years, but large samples of epidemiological data are lacking. For patients suffering SSNHL, more than 90% cases are idiopathic and the remainder are due to causes such as acoustic neuroma, stroke, malignancy, Meniere’s disease, trauma, autoimmune disease, syphilis, Lyme disease, and perilymphatic fistula [4, 5].
Acoustic neuroma (AN) is known as a benign tumor that originates from superior or inferior vestibular branch of the cochleovestibular nerve in the internal auditory canal (IAC) [6]. Sensorineural hearing loss is the major presentation of patients with AN and patients with AN could present with SSNHL as an initial symptom occasionally [7-9]. According to previous studies, the reported prevalence of AN in patients presenting with SSNHL ranges from 1.8% to 5.2% [10, 11]. As a result of the increasing widespread use of magnetic resonance imaging (MRI), more patients with AN than expected have been detected among those with SSNHL. MRI is regarded as the gold standard for imaging diagnosis of AN. In the meantime, auditory brainstem response (ABR) test is recommended for the initial assessment of SSNHL patients when appropriate, and it is highly sensitive to AN larger than 10 mm in size [10]. AN is the most frequently observed MRI abnormality in patients with SSNHL [9]. According to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines, MRI or ABR should be used for the retrocochlear pathology evaluation of patients with SSNHL [2].
Previous studies have found that hearing can improve with corticosteroid treatment in AN patient initially presenting with SSNHL [12-14] and that drug therapy is usually administered before MRI is performed. As a result, some physicians may assume that patients with SSNHL who respond to steroid therapy could effectively exclude the presence of AN, which leads to delays in the diagnosis. Since a small number of SSNHL patients whose hearing loss is caused by AN, which is also prone to clinical misdiagnosis and missed diagnosis.
In the present study, we conducted a retrospective study of 10 AN patients presenting with SSNHL as an initial symptom, with the aim of clarifying the detailed clinical features and the efficacy of treatment of AN with SSNHL and of guiding the clinic to prevent misdiagnose and missed clinically.
2. Methods