Vertebro-PICA aneurysms: midline suboccipital approach and laminectomy of the atlas.

Vertebro-PICA aneurysms represent a particular technical challenge because of the extremely narrow operative field and the presence of numerous vital neural and vascular structures. The lack of exposure still remains the limiting factor in most cases. During the 9-year period from January 1980 to October 1989, 8 vertebro-PICA aneurysms have been treated microsurgically. Of these, 2 underwent a pure suboccipital approach while 6 underwent a midline suboccipital approach with deliberate removal of the arch of the atlas in the park bench position. Seven patients did well and regained full activities while one patient died from complications related to vasospasm with brainstem infarction. One patient developed symptomatic obstructive dilation of the fourth ventricle requiring ventriculo-cisternostomy. The authors recommend the midline suboccipital approach with deliberate C1-laminectomy in ventrolateral decubitus for vertebro-PICA aneurysms. The main advantages are: constant access to the proximal vertebral artery, less medullary retraction in ventrally located aneurysms, improved exposure of the laterobulbar cisterns and the lateromedullary and tonsillar segments of the PICA, thus facilitating dissection of the aneurysm.