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Brainstem, Petrosal Surface, and Cerebellopontine Fissure

Surgical Correlation

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A, Oblique view. The petrosal surfaces of the cerebellum face forward toward the petrous bone and is the surface that is retracted to expose the cerebellopontine angle. The cerebellopontine fissure, which might also be referred to as the cerebellopontine angle, is a V-shaped fissure formed where the cerebellum wraps around the pons and middle cerebellar peduncle. The superior and inferior limbs meet laterally at the apex located at the anterior end of the petrosal fissure that divides the petrosal surface into superior and inferior parts. Cranial nerves V through XI arise within the margins of the cerebellopontine fissure. The flocculus and choroid plexus extend laterally from the foramen of Magendie above the lower limb of the fissure. The basilar sulcus is a shallow longitudinal groove on the anterior surface of the pons, which accommodates the basilar artery. B, Enlarged view. The petrosal fissure extends laterally from the apex of the cerebellopontine fissure. The abducens nerve arises in the medial part of the pontomedullary sulcus rostral to the medullary pyramids. The facial and vestibulocochlear nerves arise just rostral to the foramen of Luschka near the flocculus at the lateral end of the pontomedullary sulcus. The hypoglossal nerves arise anterior to and the glossopharyngeal, vagus, and accessory nerves arise posterior to the olives. Choroid plexus protrudes from the foramen of Luschka behind the glossopharyngeal and vagus nerves. C, Enlarged view of another brainstem. The facial and vestibulocochlear nerves join the brainstem 2 or 3 mm rostral to the glossopharyngeal nerve on a line drawn dorsal to the olive along the origin of the rootlets of the glossopharyngeal, vagus, and accessory rootlets. The rhomboid lip, a thin neural membrane in the ventral margin of the lateral recess, extends laterally behind the glossopharyngeal, vagus, and accessory nerves with the choroid plexus. D, Enlarged view of another cerebellopontine fissure. The cerebellopontine angle is the area situated between the superior and inferior limbs of the cerebellopontine fissure. The glossopharyngeal, vagus, and accessory nerves arise near the inferior limb, dorsal to the olive, and anterior to the choroid plexus protruding from the foramen of Luschka. The facial and vestibulocochlear nerves arise in the midportion of the fissure and the trigeminal nerve near the superior limb of the fissure. The hypoglossal rootlets arise in front of the olive and the cranial rootlets of the accessory nerve. (Images courtesy of AL Rhoton, Jr.)

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