The operating table is tilted head-down to prevent further air entrainment and aid with the VAE-associated hypotension treated with vasopressors and fluid resuscitation. The neurosurgeon is alerted while the FiO 2 is increased to 100%, and the surgical field is covered with wet swabs, irrigated with saline. Indications of potential VAE include hypotension, sudden drop in ETCO 2 with no change in ventilation settings or drop in oxygen saturations depending on FiO 2. Patients are ventilated with an inspired concentration of oxygen (FiO 2) 40–50%. Routine monitoring includes ECG, continuous end-tidal CO2 (ETCO 2), oxygen saturations, spirometry, continuous invasive pressure monitoring and right internal jugular vein cannulation (CVC), allowing use of vasopressors, in cardiovascular collapse. The quadrigeminal and velum interpositum cisterns communicate with the posterior pericallosal cistern (Fig.

The cistern of the velum interpositum, extending from the foramen of Monroe anteriorly to the habenula encloses the ICvs and the posterior medial choroidal artery. The paired ambient cisterns contain P2 and P3, the anterior choroidal artery, the CvRo and SCA segments. The unpaired quadrigeminal cistern contains all three major venous systems, VG, the confluences of both BvRo and ICvs, P4 and the posterior medial choroidal artery. The internal cerebral veins (ICv) lie deeper, laterally and slightly underneath the BvRo exiting through the cistern of the velum interpositum, also converging to the VG. The vein of Galen (VG) is the most dorsal part of the venous complex, joining the straight sinus (SS) while the paramedian, paired basal veins of Rosenthal (BvRo) exit the ambient cistern and converge to the VG. The surgical venous anatomy of the pineal region is complex and are covered by an arachnoid layer of varied thickness, ranging from thick and opaque to thin and translucent (Fig.

The second (P2) and third (P3) segments of the posterior cerebral artery (PCA) lie between the thalamic pulvinar and superior colliculi, while loops of the superior cerebellar artery (SCA) are often visible anterior to pineal gland. The posterior incicura extends inferior to the cerebellomesencephalic fissure that accomodates its corresponding vein, also termed precentral vein, a key, midline venous landmark (Fig. Although off midline (lateral and far-lateral) approaches are available for pineal region tumours, the midline IT/SC approach offers optimal surgical orientation in the region of posterior incisura, bounded superiorly by the inferior aspect of the splenium, the forniceal crura and the hippocampal commissure and inferiorly by the vermian culmen, and medially and laterally, by the central and quadrangular lobules, respectively. The complex pineal region can be accessed by the supracerebellar/infratentorial (SC/IT) approach, occipital transtentorial, posterior interhemispheric transcallosal and the combined supra-/IT approach, for giant tumours.

Me and She Square by Chandan Sharma