Challenges in the Management of a Ruptured Bihemispheric Posterior Inferior Cerebellar Artery Aneurysm.

Abstract

Bihemispheric posterior inferior cerebellar artery (PICA) is a rare anatomic variant wherein a single PICA supplies both cerebellar hemispheres. Inasmuch as it is the only PICA, treatment of aneurysms arising from this anatomic variant is more complex. We present a case of a ruptured bihemispheric PICA aneurysm and the challenges encountered in its management. A 54-year-old man presented with giddiness and nausea. Otherwise, he was neurologically intact. Computed tomography of the brain showed a right cerebellar hematoma and intraventricular hemorrhage. Cerebral angiography revealed a dissecting aneurysm in the retromedullary segment of a right bihemispheric PICA with a prominent saccular component. Initially, the patient refused to undergo any invasive treatment. However, when a follow-up angiogram showed an increase in the size of the aneurysm sac, he consented to treatment. Although parent vessel occlusion (PVO) was the clinical recommendation, in view of the patient's apprehensions, only the saccular component of the aneurysm was coil embolized without sacrifice of the parent vessel. Fifteen days after the coiling, there was a rebleed from this dissecting aneurysm, which was treated with PVO followed by suboccipital craniectomy. The patient made a reasonable recovery, and his modified Rankin score was 1 at his 6-month follow-up visit. In dissecting aneurysms of a bihemispheric PICA, isolated endosaccular occlusion provides uncertain protection from a rebleed, whereas a more reliable treatment with PVO carries an unpredictable risk of ischemic complications. The risks of a PVO may be rationalized as a life-saving measure; however, the subsequent threshold for posterior fossa decompression should be low.