Consequences of preoperative evaluation of patterns of drainage of the cavernous sinus in patients treated using the anterior transpetrosal approach.

Extradural procedures in an anterior transpetrosal approach (ATPA) may interrupt the route of drainage from the superficial middle cerebral veins (SMCVs) and the cavernous sinus (CS) to the pterygoid venous plexus at the temporal skull base. Patterns of drainage of the SMCV and the CS and the results of surgery were examined in 12 patients with petroclival lesions treated using the ATPA between 2000 and 2008. The angiographic patterns of drainage of the SMCV were examined in 22 sides of the 12 patients. The SMCV drained into the sphenoparietal sinus in 12 sides, the sphenobasal veins in 4 sides, and the cortical veins in 6 sides. The patterns of drainage of the CS were examined on 12 sides in which the SMCV drained into the sphenoparietal sinus. The CS drained into the inferior petrosal sinus (IPS) in 7 sides and equally into the pterygoid plexus and IPS in 3 sides. The CS drained mainly into the pterygoid plexus in 2 sides of 2 patients, who both suffered temporal lobe swelling postoperatively. The pattern of venous drainage of the CS must be considered in planning surgical approaches to petroclival lesions. In patients with a well-developed pterygoid plexus, surgical interruption of this drainage route may be a cause of injury of the temporal lobe.