ISOLATED TRIGEMINAL NEURALGIA SECONDARY TO DISTAL ANTERIOR INFERIOR CEREBELLAR ARTERY ANEURYSM

A 43-year-old woman complaining of severe pain of the right side of th e face was admitted to the Department of Neurosurgery. It had been pre sent for three months and diagnosed as trigeminal neuralgia. The CT sc an without contrast material had been considered normal at that time. Three months later, after a favourable response to carbamazepine, she suddenly developed right occipital headache and drowsiness. On admissi on, she was alert, and neurological examination revealed only mild nec k stiffness. Computed tomographic scan demonstrated an acute hematoma in the right cerebellopontine angle and in the fourth ventricle. Verte bral angiography revealed an aneurysm of the right anterior inferior c erebellar artery (AICA). A posterior fossa approach disclosed a large, nearly totally thrombosed, saccular AICA aneurysm, which showed minim al compression to the pens at the trigeminal root entry zone. The aneu rysm was clipped and excised. She showed an excellent recovery and was free of pain in the early postoperative period and at the last examin ation 16 months later. Aneurysms in the distal AICA are very rare lesi ons. Only 31 cases have been published so far. Distal AICA aneurysm in an extremely unusual cause of trigeminal neuralgia secondary to aneur ysmal compression. The literature concerning AICA aneurysms and their clinical manifestations is reviewed and discussed.