Magnetic resonance imaging of vertebrobasilar ectasia in trigeminal neuralgia.

Vertebrobasilar ectasia is a rare cause of typical trigeminal neualgia. In a recently published large series only thirty-one (2%) of 1404 consecutive patients with vascularly determined neuralgia were found to have vertebrobasilar compression. We present three patients with trigeminal neuralgia caused by vertebrobasilar ectasia, who were evaluated with high resolution magnetic resonance imaging (MRI). MRI studies provided accurate information on the anatomical location and course of the ectatic vessel in the cerebellopontine angle and the caused mass effect on the brainstem. With gadolinium-enhancement vascular compression of the trigeminal nerve was demonstrated clearly. Surgery confirmed compression of the fifth nerve by an ectatic and tortuous vertebrobasilar artery in two cases. Following microvascular decompression neither patient experienced further pain. The third patient was treated with a ventriculoperitoneal shunt, as he developed occlusive hydrocephalus caused by the vertebrobasilar dolicho-ectasia. MRI is useful in the evaluation of trigeminal neuralgia as it excludes other aetiologies such as tumour or arteriovenous malformation, but also demonstrates cranial nerve compression by ectatic vertebral arteries.