Abstract

Background
and Objectives: Vertebrobasilar ischemia (VBI) can cause sudden deafness because the vertebrobasilar system supplies most of the auditory system including the inner ear. There have been few reports that carefully examine the deafness associated with vertebrobasilar ischemia (VBI). The aim of this study was to investigate the incidence of deafness associated with VBI, the site predominantly involved in deafness, and the clinical implication of an isolated sudden deafness.
Methods
Of 364 consecutive cases of VBI diagnosed by clinical features and brain MRI between January 2000 and June 2003, we prospectively identified 29 cases of the sudden deafness as a symptom of VBI. We defined the sudden deafness of vascular cause as follows: (1) the patients noted a definite change in hearing with their other neurological symptom; (2) Pure tone audiogram also documented definite sensorineural hearing loss; and (3) brain MRI showed an acute infarct in the territory of vertebrobasilar system. Pure tone audiogram, speech discrimination testing, stapedial reflex testing, and auditory brainstem response were performed to localize the site of lesion in the auditory pathway.
Results
In our series, the incidence of sudden deafness in VBI is 7.9% (29/364). Of 29 cases with deafness of vascular origin, 21 patients had anterior inferior cerebellar artery (AICA) territory infarction. The other patients had an infarct in brainstem (4), caudal cerebellum in territory of the posterior inferior cerebellar artery (3), and non-territorial area of cerebellum (2), respectively. From the findings of audiological testings, hearing loss was predominantly localized to the cochlear in 14 patients, retrocochlear in 4 patients, and combined on the affected side cochlear and retrocochlear in 11 patients. Of 21 cases with AICA infarction, 5 patients had an isolated sudden deafness as a prodrome of the AICA infarction 1-10 days prior to onset of other brainstem and/or cerebellar symptoms. Conclusions: In our series, the overall incidence of sudden deafness of vascular origin is relative low (7.9%). The most common affected territory on brain MRI associated with the sudden deafness is the infarction in the distribution of the AICA. Audiological examinations suggest that the sudden deafness in VBI is usually due to dysfunction of the cochlear resulting from ischemia of the inner ear. Rarely, the sudden deafness may serve as a heralding manifestation of VBI.