Background: Although the superficial middle cerebral vein (SMCV) usually connects with the cavernous sinus, there are several anatomical variations. We determined whether differences in SMCV drainages patterns affected the perioperative management of petroclival meningioma. Methods: The subjects included 17 patients (4 men
13 women) who underwent resection of a petroclival meningioma. SMCV drainage patterns were classified into four groups according to angiographic findings: (1) The SMCV connected with the cavernous sinus (Group A)
(2) The SMCV was either absent or connected directly with the superior sagittal or transverse sinus through the cortical veins (Group B)
(3) The SMCV turned downward and connected with the pterygoid plexus through the sphenobasal vein (SpBV, Group C)
and (4) The SMCV ran across the bottom of the middle fossa and connected with transverse sinus via the sphenopetrosal sinus (SpPS, Group D). Results: In all 9 patients in Group A, the SMCV drainage pattern did not affect any aspect of perioperative management. In contrast, SMCV drainage patterns in 3 of 4 patients in Group B and both patients in Groups C and D had an effect on perioperative management, indicating a significant impact of variations in SMCV drainage patterns (P &lt
0.005). In 2 patients in Group C and 1 in Group D, the operating corridor provided by a transpetrosal approach was small in order to preserve the SpBV or SpPS. In the other patient in Group D, an anterior transpetrosal approach was not selected preoperatively because the SpPS would likely be injured during surgery. Conclusions: In cases, where the SMCV directly connects with superior sagittal or transverse sinus, SpBV or SpPS, surgeons have to meticulously select a safe and effective approach and take measures to preserve the SpBV or SpPS during surgery.