Lateral supracerebellar infratentorial approach for microsurgical resection of large midline pineal region tumors: techniques to expand the operative corridor.

Pineal region tumors pose certain challenges in regard to their resection: a deep surgical field, associated critical surrounding neurovascular structures, and narrow operative working corridor due to obstruction by the apex of the culmen. The authors describe a lateral supracerebellar infratentorial approach that was successfully used in the treatment of 10 large (> 3 cm) midline pineal region tumors. The patients were placed in a modified lateral decubitus position. A small lateral suboccipital craniotomy exposed the transverse sinus. Tentorial retraction sutures were used to gently rotate and elevate the transverse sinus to expand the lateral supracerebellar operative corridor. This approach placed only unilateral normal structures at risk and minimized vermian venous sacrifice. The surgeon achieved generous exposure of the caudal midline mesencephalon through a "cross-court" oblique trajectory, while avoiding excessive retraction on the culmen. All patients underwent the lateral approach with no approach-related complication. The final pathological diagnoses were consistent with meningioma in 3 cases, pilocytic astrocytoma in 3 cases, intermediate grade pineal region tumor in 2 cases, and pineoblastoma in 2 cases. The entire extent of these tumors was readily reachable through the lateral supracerebellar route. Gross-total resection was achieved in 8 (80%) of the 10 cases; in 2 cases (20%) near-total resection was performed due to adherence of these tumors to deep diencephalic veins. Large midline pineal region tumors can be removed through a unilateral paramedian suboccipital craniotomy. This approach is simple, may spare some of the midline vermian bridging veins, and may be potentially less invasive and more efficient.