OBJECTIVE: Among the types of idiopathic sudden sensorineural hearing loss, low-tone type without vertigo has attracted attention for its recurrence and progression to Ménière's disease. The purpose of this article is to characterize the recurrent type of sudden low-tone sensorineural hearing loss without vertigo using neuro-otologic examination. STUDY DESIGN: Retrospective. SETTING: Tertiary referral center. INTERVENTIONS: Diagnostic and prognostic. METHODS: Long-term follow-up of 82 patients diagnosed at the university hospital with idiopathic sudden low-tone sensorineural hearing loss without vertigo. The recurrence rate was determined according to results of electronystagmography (ENG) and electrocochleography (ECochG) tests at the onset of the first episode of hearing loss. RESULTS: Forty percent of the patients experienced recurrent hearing loss. Among the patients who experienced recurrence, 45% had a recurrence within 6 months from the first episode of hearing loss. The recurrence rate varied largely according to the results of the ENG and ECochG tests. In patients with an elevated ratio of the summating potential to the action potential and spontaneous nystagmus on ENG, the recurrence rate was 78.6%. However, in those with a normal ratio of the summating potential to the action potential and without spontaneous nystagmus, the recurrence rate was 31.8%. CONCLUSION: Our results indicate that idiopathic sudden low-tone sensorineural hearing loss without vertigo has a high recurrence rate when vestibular alteration and endolymphatic hydrops are detected on initial examination. A combination of nystagmus detection and ECochG test well characterizes the pathophysiology of sudden low-tone sensorineural hearing loss without vertigo.
OBJECTIVE: Among the types of idiopathic sudden sensorineural hearing loss, low-tone type without vertigo has attracted attention for its recurrence and progression to Ménière's disease. The purpose of this article is to characterize the recurrent type of sudden low-tone sensorineural hearing loss without vertigo using neuro-otologic examination. STUDY DESIGN: Retrospective. SETTING: Tertiary referral center. INTERVENTIONS: Diagnostic and prognostic. METHODS: Long-term follow-up of 82 patients diagnosed at the university hospital with idiopathic sudden low-tone sensorineural hearing loss without vertigo. The recurrence rate was determined according to results of electronystagmography (ENG) and electrocochleography (ECochG) tests at the onset of the first episode of hearing loss. RESULTS: Forty percent of the patients experienced recurrent hearing loss. Among the patients who experienced recurrence, 45% had a recurrence within 6 months from the first episode of hearing loss. The recurrence rate varied largely according to the results of the ENG and ECochG tests. In patients with an elevated ratio of the summating potential to the action potential and spontaneous nystagmus on ENG, the recurrence rate was 78.6%. However, in those with a normal ratio of the summating potential to the action potential and without spontaneous nystagmus, the recurrence rate was 31.8%. CONCLUSION: Our results indicate that idiopathic sudden low-tone sensorineural hearing loss without vertigo has a high recurrence rate when vestibular alteration and endolymphatic hydrops are detected on initial examination. A combination of nystagmus detection and ECochG test well characterizes the pathophysiology of sudden low-tone sensorineural hearing loss without vertigo.