Contralateral hearing loss as an effect of venous congestion at the ipsilateral inferior colliculus after microvascular decompression: report of a case

Contralateral hearing loss after surgical procedures within the cerebellopo ntine angle is rarely seen and its pathophysiological background is not yet understood. A patient with contralateral hearing loss after microvascular decompression for trigeminal neuralgia is described. Ipsilateral brainstem auditory potential (BAEP) monitoring and facial nerve EMG did not show majo r abnormalities. During otherwise uneventful and successful surgery a branc h of the petrosal vein was sacrificed to widen the access to the trigeminal root exit zone. On the third postoperative day the patient complained abou t contracteral hearing loss, which was verified by audiometry. Contralatera l BAEPs showed low amplitudes and delayed interpeak latencies. Brain CT was normal. Brain MRT. on the 8th postoperative day disclosed abnormal signals within the ipsilateral inferior colliculus. Intravenous heparinisation was performed and hearing slowly recovered over a 3 month period. Results from this patient offer a pathophysiological mechanism for contralateral hearin g loss after cerebellopontine angle surgery, illustrate the importance of v enous drainage preservation, gives evidence about the generation of BAEP co mponents within the contralateral brainstem, and stresses the importance of intraoperative BAEP monitoring.