Vessel tortuosity as a cause of posterior fossa cranial nerve syndromes.

Neurologic syndromes may be caused by mechanical vascular compression of cranial nerves in the posterior fossa. The clinical expression is variable and can be divided into two main groups. Isolated cranial nerve involvement is most frequently associated with tortuous, elongated vertebral and basilar arteries as well as redundant loops of the anteroinferior cerebellar artery. Pseudotumoral manifestations of cranial nerve involvement at the level of the cerebellopontine angle are more frequently related to aneurysms of the vertebral and basilar arteries.