Surface Anatomy of the Brainstem: Correlation of 2D Radiologic Landmarks, 3D Image Reconstructions, and Gross Anatomic Appearance J Ormsby (1), T Morris (2), A Blitz (3), AF Choudhri (4) 1 University of Tennessee Health Science Center/Methodist Healthcare, Memphis, TN, 2 Louisiana State University Health Science Center Shreveport, Shreveport, LA, 3 Johns Hopkins University, Baltimore, MD, 4 University of Tennessee Health Science Center/Le Bonheur Children's Hospital, Memphis, TN ASNR 53 rd Annual Meeting & The Foundation of the ASNR Symposium 2015 April 25-April 30, 2015

Disclosures No conflicts to report

Introduction Understanding the surface anatomy of the brainstem is a valuable tool for the neuroradiologist to become an effective consult for the neurosurgeon when planning surgery.

Purpose Correlate 2D and 3D MR images of the brainstem surface anatomy with gross anatomy images Provide general function of these structures Review cisternal segments of lower cranial nerves VI-XII

Approach Review of high resolution MR Images of the brainstem were preformed for representative images of the surface anatomy of brain stem. Osirix, Vitrea, and Terarecon were used to create 3-D images of the brainstem to be able to correlate visually with what the neurosurgeon sees Gross anatomy images were collected to further provide correlation

Labeling Naming of structures was based on commonly accepted names at our institution The names can slightly very between institutions especially when talking about sulcus/fissure/groove It is best to discuss with your referring physicians on the nomenclature they prefer

Ventral Surface of Brainstem

Basilar Groove Ventral midline of the pons where the basilar artery courses

Pontomedullary sulcus Groove at which the Pons and Medulla connect ventrally. Site of cisternal segment origin of cranial nerves VI-VIII.

Anterior Median Fissure Central groove ventrally of the Medulla oblongata. Disrupted at pyramidal decussation.

Pyramids Prominences bilaterally of the superior ventral medulla omblangata. Contain the corticospinal corticobulbar tracts which course in a craniocaudal direction

Preolivary Groove Goove between Pyramids and Olives. Site of cisternal segment origin of crainial nerve XII fibers.

Olives Structures lateral to the pyramids containing the superior and inferior olivary nuclei. Nuclei aid in sound perception and cerebellar motor learning/function, respectively.

Retroolivary Groove Groove seperating the olives from the ventral spinocerebellar tract. Site of cisternal segment origin of cranial nerves IX and X.

Anterolateral Sulcus Confluence of Preolivary and Retroolivary groove caudally. Location of rootlets of cranial nerve XII.

Ventral Surface of Brainstem* Basilar Groove Pontomedullary Sulcus Anterior Median Fissure Olive Preolivary Groove Pyramid Anterolateral Sulcus *Retroolivary groove not seen on image

Dorsal Surface of Brainstem

Superior Colliculus Paired structures along dorsal Midbrain inferior to the pineal gland. Major function is for eye movements, but also helps with directing head movement with visualization.

Inferior Colliculus Paired structures along dorsal midbrain inferior to the superior coliculli. Complex integrative site for the auditory pathway.

Posterior Median Fissure Midline sulcus along the dorsal surface of the medulla oblongata

Facial Colliculus Dorsal prominences just lateral to the posterior median fissure along the caudal portion of the floor of the 4 th ventricle. Represent motor fibers of cranial nerves VII as they loop around the abducens nuclei.

Sulcus Limitans Lateral sulcus of the floor of the 4 th ventricle seperating cranial nerve motor nuclei from sensory nuclei.

Hypoglossal Trigone Bilateral eminences along the more caudal portion of the floor of the 4 th ventricle. Superiomedial to valgal trigone this is the location of the hypoglossal nucleus.

Vagal Trigone Bilateral eminences along the caudal portion of the floor of the 4 th ventricle and Inferiolateral to hypoglossal trigone. Location of the dorsal nucleus of the vagus nerve.

Obex Confluence between the 4 th ventricle and central canal of the spinal cord

Dorsal Surface of Brainstem Superior colliculus Inferior colliculus Posterior Median Fissure Sulcus Limitans Facial Colliculus Hypoglossal Trigone Vagal Trigone Obex

Cranial Nerve VI (Abducens) Most medial of the cranial nerves with cisternal segment originating in the pontomedullary sulcus. Superior to the pyramids.

Cranial Nerve VII (Facial) Cisternal segment origin situated between cranial nerves VII and VIII in the pontomedullary sulcus. Superior to the olives.

Cranial Nerve VIII (Vestibulocochlear) Most lateral of the cranial nerves with cisternal segment originating in the pontomedullary sulcus. Superior to the retroolivary groove.

Cranial Nerve IX (Glossopharyngeal) More superior cranial nerve with cisternal segment originating in the retroolivary groove. Can be difficult to discern from cranial nerve X, especially on axial.

Cranial Nerve X (Vagal) More inferior cranial nerve with cisternal segment originating in the retroolivary groove. Can be difficult to discern from cranial nerve IX, especially on axial.

Cranial Nerve XI (Accessory Spinal) Rootlets are found just inferior to the olive in the anterolateral sulcus.

Cranial Nerve XII (Hypoglossal) Cisternal segment origin is found within the preolivary sulcus

Summary Knowledge of surface anatomy of the brainstem gives greater skills as a consultant for neurosurgical planning This presentation lays down a format for quick review of this anatomy with both gross anatomical an 3D correlations Additonal review of the lower cranial nerves were provided as they are closely related with the reviewed surface anatomy

Jacob Ormsby, MD, MBA Questions?

Thank you!