Microsurgical Resection of a Midbrain Cavernous Malformation via the Paramedian Supracerebellar Infratentorial Translateral Mesencephalic Sulcus Approach Using the Dynamic Lateral Semisitting Position: Two-Dimensional Operative Video with 3-Dimensional Anatomical Models.

Brainstem cavernous malformations are relatively rare lesions with a higher tendency of hemorrhage than supratentorial cavernous malformations. Due to the compact arrangement of fiber tracts and nuclei of the region, any hemorrhagic event can cause severe neurological deficits. This eloquent architecture of the area also makes any surgical attempt challenging. Anatomical location and dimension of the lesion, presence of hemorrhage, age, and the neurological status of the patient need to be considered before determining the appropriate course of treatment. A surgical approach is preferred for young symptomatic patients with at least 1 previous episode of bleeding. Subtemporal and supracerebellar infratentorial approaches can be used to access these lesions. We present a 44-year-old woman with a hemorrhagic tegmental cavernous malformation presenting with imbalance and right-sided hemiparesis (Video 1). The paramedian supracerebellar infratentorial translateral mesencephalic sulcus approach is used to resect the lesion with the patient in a dynamic lateral semisitting position. The paramedian variant of the supracerebellar infratentorial approach provides a relatively bridging vein-free corridor compared with midline approaches. With the patient in the semisitting position, gravity retraction of the brain provided a natural corridor with a clear surgical field. In the dynamic lateral semisitting position, we aimed to reduce the risk of venous air embolism associated with the sitting position by keeping the patient in the lateral decubitus position during the dural and extradural phases of the surgery..