Right Occipital Transtentorial Approach. E, The vermis has been retracted, and the vein of Galen has been displaced to the left, to expose the pineal body, superior and inferior colliculi, trochlear nerves, and superior peduncles. The exposure of the lateral part of the contralateral half of the quadrigeminal cistern is limited. (Image courtesy of AL Rhoton, Jr.)