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
April 25-April 30, 2015
ASNR 53rd Annual Meeting & The Foundation of
the ASNR Symposium 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
Olive
Preolivary
Groove
Pyramid
Anterolateral
Sulcus
*Retroolivary groove not seen on image
Anterior
Median
Fissure
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 4th ventricle. Represent motor fibers of cranial nerves VII
as they loop around the abducens nuclei.
Sulcus Limitans
Lateral sulcus of the floor of the 4th ventricle seperating cranial nerve motor nuclei
from sensory nuclei.
Hypoglossal Trigone
Bilateral eminences along the more caudal portion of the floor of the 4th 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 4th ventricle and
Inferiolateral to hypoglossal trigone. Location of the dorsal nucleus of the vagus
nerve.
Obex
Confluence between the 4th ventricle and central canal of the spinal cord
Dorsal Surface of Brainstem
Facial
Colliculus
Superior
colliculus
Inferior
colliculus
Hypoglossal
Trigone
Posterior
Median
Fissure
Sulcus
Limitans
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
Questions?
Jacob Ormsby, MD, MBA (jormsby@uthsc.edu)
Thank you!