Asymmetric hearing loss and tinnitus

Audiological assessment confirmed moderate right sensorineural hearing loss in all frequencies and a mild drop in high frequencies in the left ear.Because of the asymmetry of his symptoms, magnetic resonance imaging (MRI) of the brain and internal auditory canal was performed (fig 1 ).2 12 However, histological studies on human cadavers have shown a much higher prevalence of 0.8-2.7%, suggesting that a large number of cases are asymptomatic (silent) or even misdiagnosed. 13 14 15 Interestingly, the prevalence of incidentally diagnosed vestibular schwannomas is about two in 10000 people in the US (California); this is lower than the histological prevalence but higher than that reported in clinical and epidemiological studies. 16 Currently, MRI is the gold standard for diagnosing vestibular schwannomas. 1 2 These tumours typically appear as well delineated hypointense (dark grey-black) lesions on non-contrast T2 weighted scans and isointense (light grey) lesions on non-contrast T1 weighted scans, whereas they enhance strongly after administration of intravenous gadolinium (fig 2).20 Hearing loss is progressive in most cases. 2 18 However, unilateral sudden sensorineural hearing loss can be the initial symptom and is seen in 1.7-27% of patients with vestibular schwannomas. 21 Patients with sudden sensorineural hearing loss who undergo MRI have a 2% chance of having a vestibular schwannoma. 2 Hearing is completely normal in the affected ear in 5-12.5% of patients with vestibular schwannomas. 22 Unilateral tinnitus has been reported as the main presenting symptom in 8-13% of patients with vestibular schwannoma. 2 However, tinnitus can be an accompanying symptom, mainly associated with hearing loss, in 60-83% of such patients. 2 18 Dizziness or imbalance is the main symptom in 7-26% of patients with a vestibular schwannoma. 2 3 4 5 6 21 22 However, symptoms related to the vestibular nerve are not always described as rotatory vertigo but also as unsteadiness or even "light headedness," so the precise incidence of vertigo in unclear.Overall, abnormal clinical balance test results raise the suspicion of peripheral vestibulopathy or even central balance disorder and warrant further investigation and imaging studies. 2 Several studies have looked into the correlation between the severity of vestibulocochlear symptoms (hearing loss, tinnitus, dizziness, and imbalance) and tumour growth or size. 4 5 6 8 9 10 11 23 24 Most studies, including rigorous systematic reviews,