The approaches that are directed along or near the midline are shown as solid lines, and those that approach the third ventricle away from the midline are shown as dotted lines. The midline or near-midline approaches to the anteroinferior part of the third ventricle are the transsphenoidal and the subfrontal. The subfrontal operative route is divided into four different approaches: (a) the lamina terminalis approach through the lamina terminalis; (b) the opticocarotid approach through the opticocarotid triangle; (c) the subchiasmatic approach below the optic chiasm between the optic nerves; and (d) the transfrontal-transsphenoidal approach through the planum sphenoidale and sphenoid sinus. The approaches to the floor and anteroinferior part of the third ventricle that are directed off the midline are the subtemporal and the frontotemporal. The approaches to the anterosuperior part of the third ventricle in the region of the foramen of Monro are the anterior transcallosal and the anterior transcortical. The supratentorial approaches to the posterior part of the third ventricle are the posterior transcallosal, posterior transcortical, and occipital transtentorial. The infratentorial supracerebellar approach is directed below the tentorium cerebelli to the posterior part of the third ventricle. (Images courtesy of AL Rhoton, Jr.)