The preoperative venogram in planning extended craniectomies.

A technique of extended craniectomy sometimes allows removal of large central or transtentorial mass lesions at a single operative sitting because it affords better exposure and control of normal structures. While seeking to avoid multiple craniotomies, this method requires permanent ligation of the transverse venous sinus. Unless there is adequate collateral venous drainage from the ipsilateral hemisphere, the patient is at risk for venous infarction in the post-craniectomy period. The purpose of this study is to propose a method of establishing the presence of collateral venous drainage preoperatively. Each carotid artery is injected with the head in a neutral position and with the head turned to the side ipsilateral to the carotid artery injection in an attempt to divert the venous flow. Fifty patients were examined using this method; seven were being evaluated for possible craniectomies. The technique identified nine patients with potential venous collaterals (20%). They would otherwise have been considered nonoperable: two of the six patients eventually operated upon (33%) fell into this category. In general, the operative procedure may be safe more often on the left than the right (45%) vs (20%). Particular attention must be given to the pattern of venous drainage from the posterior temporal lobe to avoid isolation of the venous drainage from this area.