Why are aneurysms of the posterior inferior cerebellar artery so unique? Clinical experience and review of the literature.

BACKGROUND: Aneurysms of the posterior inferior cerebellar artery (PICA) are rare lesions. The anatomical behaviour of the artery itself is complex and characterised by a multitude of variations. The same holds true for the aneurysms discovered there. Dissecting aneurysms can be found from the PICA origin to the distal artery berry. They have a wider range of clinical and radiographical presentations and their surgical treatment requires more than one standard approach.

METHODS: We encountered 14 patients with PICA aneurysms within two surgical series of a total of 1345 cerebral aneurysm patients (1 %). In this patient group of the last 27 years only 3 of the 14 were distal aneurysms ("true" PICA aneurysms)

RESULTS: The 14 patients harboured 15 aneurysms (9 right-sided and 6 left-sided). The female/male ratio of the patients was 9/5, the mean age 52.7 years. 13 of them had sustained an SAH. 7/14 patients were hypertensive, in 10 patients at least one of putative cerebrovascular risk factors was found. From the 15 aneurysms treated, 11 were typical berry aneurysms, 4 dissecting aneurysms. The aneurysms ranged in size from 5 to 20 mm (mean 9.1). 11 aneurysms were located within the anterior medullary segment, 1 in the tonsillomedullary and 2 in the telovelomedullary segments. All patients were surgically treated, 10 in a semi-sitting position via a suboccipital craniotomy, 4 in the prone position. 13 aneurysms were clipped, two were treated differently. Two patients died due to their bad preoperative clinical status.

CONCLUSIONS: The clinical, radiographical and surgical approaches to PICA aneurysms still represent a challenge.