[Idiopathic sudden hearing loss: role of the posterior communicating cerebral arteries of the Willis' circle].

Sudden hearing loss (SHL) is a neurosensorial hearing loss of variable entity with an onset of less than three days. In most cases (85-90%) it is of unknown etiology (idiopathic sudden hearing loss--ISHL). The most accredited hypotheses for origin are: viral, immunitary and vascular. ISHL accounts for approximately 1% of all neurosensorial hearing loss; onset is most frequent in winter, i.e. January and February, and it most frequently affects women, particularly at 15 and between 40-50 years of age. In order to evaluate the role of vascular condition on the onset of ISHL, we focused our attention on the circle of Willis. The results confirm that, in the absence of cerebro-vascular pathology, posterior communicating arteries (PCAs) that cannot be activated--evaluated by transcranial Doppler (TCD)--are associated with ISHL. Moreover, hemodynamic alterations detected in the basilar artery in ISHL patients are correlated with the final prognosis for hearing. These observations highlight the importance of TCD in testing subjects at risk for idiopathic SHL and show that PCAs are essential in maintaining normal cochlear function.