Supracerebellar Perspective of Pineal Region. The occipital lobes and deep cerebrovascular structures have been removed bilaterally to permit visualization of the pineal region. The right trochlear nerve is visible emerging from the dorsal surface of the brainstem. The right trochlear nerve originates from the left trochlear nucleus then decussates within the superior medullary velum prior to exiting the dorsal surface of the brainstem immediately caudal to the inferior colliculus. The paired inferior and superior colliculi together constitute the tectum or quadrigeminal plate.  The brachium of the inferior colliculus courses from the inferior colliculus to the medial geniculate nucleus (MGN) of the thalamus.  The MGN lies medial to the lateral geniculate nucleus and inferior to the pulvinar, the bulbous caudal nuclear group of the thalamus (not labeled).  This supracerebellar perspective can assist to orient the surgeon during the surgical approach to the pineal region. (Image courtesy of AL Rhoton, Jr.)