Brainstem: Topography and Levels
peduncles
(myelinated) tracts that link cerebellum with brain stem, cerebrum, and spinal cord -superior, middle, and inferior
pons ventral surface structures
-basilar sulcus -basilar pons -basilar artery -trigeminal CN V
between pons and medulla ventral surface
-cerebellar pontine angle -pontomedullary sulcus -Abducens CN VI -Facial CN VII -vestibulocochlear CN VII
midbrain ventral surface structures
-cerebral crus -interpeduncular fossa -oculomotor CN III -trochlear CN IV
telencephalon adult derivative and cavities
-cerebral hemispheres -lateral ventricles
parts of closed medulla dorsal surface
-cuneate tubercle -gracile tubercle -posterior median sulcus
damage to the brainstem is manifested by
-functional loss (somatosensory, motor, etc.) -abnormalities in cranial nerve functions
parts of open medulla dorsal surface
-median sulcus -inferior fovea -hypoglossal trigone -vagal trigone
Myelencephalon adult derivative and cavities
-medulla -caudal (inferior) half of fourth ventricle
olive
-medulla ventral surface -between preolivary sulcus and postolivary sulcus -elevation lateral to pyramid
preolivary sulcus
-medulla ventral surface -between the pyrammid olive -hypoglossal CN XII
anterior median fissure
-medulla ventral surface -deep groove on anterior medulla
pyramid
-medulla ventral surface -directly lateral to anterior median fissure
postolivary sulcus
-medulla ventral surface -lateral to olive -glossopharyngeal CN IX -vagus CN X -accessory CN XI
mesencephalon adult derivative and cavities
-midbrain -aqueduct
cerebral crus
-midbrain ventral surface -forms the ventral surface of the midbrain
interpeduncular fossa
-midbrain ventral surface -space between cerebral crus
parts of brainstem
-mindbrain -pons -medulla
closed medulla
-more inferior -not associated with fourth ventricle
open medulla
-more superior -associated with fourth ventricle
motor and sensory root of trigeminal nerve
-motor: more medial -sensory: more lateral
medulla dorsal surface structures
-part of vestibular area -inferior fovea -median sulcus -cuneate tubercle -gracile tubercle -posterior median sulcus -vagal trigone -hypoglassal trigone
metencephalon adult derivative and cavities
-pons and cerebellum -rostral (cranial) half of fourth ventricle
basilar sulcus
-pons ventral surface -anterior midline sulcus where basilar artery lies
primary transverse segments of brain
-prosencephalon (forebrain) -mesencephalon (midbrain) -rhombencephalon (hindbrain)
medulla ventral surface structures
-pyramid -preolivary sulus -olive -postolivary sulcus -anterior median fissure
midbrain dorsal surface structures
-superior colliculus -inferior colliculus -trochlear (IV) nerve
pons dorsal surface structures
-superior, middle, and inferior peduncles (?) -medial eminence -facial colliculus -stria medullaris -part of vestibular area -median sulcus
diencephalon adult derivative and cavities
-thalamus -subthalamus -hypothalamus -epithalamus -third ventricle
tonsillar herniation effects
-tonsillar impactation in the foramen magnum -results in brainstem pressure -> depression of conscious level and respiratory irregularities
frequency of anencephaly
-very common affecting 1 in 1,000 pregnancies with most ending in miscarriage -an estimated 1 in 10,000 infants are born with most dying soon after birth -only 4 cases of anencephalic children surviving for longer periods
caudal open medulla transverse stain
ANTERIOR -anterior median fissure -pyramid -preolivary sulcus -olive -postolivary sulcus POSTERIOR -4th Ventricle -hypoglossal trigone -vagal trigone -inferior fovea -vestibular area -inferior cerebellar peduncle
closed medulla transverse stain
ANTERIOR -anterior median fissure -pyramid MIDDLE -reticular formation POSTERIOR -posterior median sulcus -gracile tubercle -posterior intermediate sulcus -cuneate tubercle
rostral pons transverse stain
ANTERIOR -basilar sulcus POSTERIOR -small circular cerebral aqueduct -trochlear cCN IV
caudal midbrain transverse stain
ANTERIOR -narrow interpeduncular fossa -squared, short cerebral crus POSTERIOR -small cerebral aqueduct
rostral midbrain transverse stain
ANTERIOR -wide interpeduncular fossa -wide, rectangular cerebral crus POSTERIOR -small circular cerebral aqueduct
caudal pons transverse stain
ANTERIOR -basilar sulcus -pontine nuclei INTERNAL -abducens CN VI -facial CN VII POSTERIOR -round 4th ventricle
middle pons transverse stain
ANTERIOR -basilar sulcus -pontine nuclei INTERNAL -trigeminal CN V POSTERIOR -oval 4th ventricle
pontomedullary sulcus
Separates pons & medulla. -Abducens CN VI -Facial CN VII -vestibulocochlear CN VII
cerebellar pontine angle
angle between pons, medulla and cerebellum -Facial CN VII -vestibulocochlear CN VII
fourth ventricle location
between pons/medulla and cerebellum
tracts
bundles of myelinated axons in the CNS
cuneate tubercle
closed medulla dorsal surface -lateral prominence
gracile tubercle
closed medulla dorsal surface -medial, right next to posterior median sulcus
brainstem and cranial nerves
contains functional centers for all but 1 of the 12 pair of cranial nerves
brainstem and long tracts
contains the long tracts that transmit impulses from all parts of the body to the forebrain as well as impulses that originate in the forebrain
cause of anencephaly
cranial end of neural tube fails to close properly -forebrain does not form
prognosis of brainstem lesions
frequently fatal -vital functional centers (cardiac, respiratory) are located in the brainstem
posterior median sulcus
medulla dorsal surface
inferior fovea
medulla dorsal surface -between hypoglossal and vagal trigone
primary mesencephalon becomes
mesencephalon (midbrain)
rhombencephalon becomes
metencephalon and myelencephalon
superior and inferior colliculus
midbrain dorsal surface -4 protrusions
aqueduct location
near midbrain
median sulcus
open medulla and pons dorsal surface
vagal trigone
open medulla dorsal surface -medial inferior prominence
hypoglossal trigone
open medulla dorsal surface -medial superior prominence, next to median sulcus
vestibular area
pons and medulla dorsal surface -lateral edges inside 4th ventricle
stria medullaris
pons dorsal surface
facial colliculus
pons dorsal surface -medial, inferior prominence
medial eminence
pons dorsal surface -superior, medial prominence
brainstem and cerebellum are found in the
posterior cranial fossa
prosencephalon becomes
telencephalon and diencephalon
anencephaly
the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development -brain stem still present
basilar pons
ventral surface of pons
oculomotor nerve stems from
CN III -interpeduncular fossa of midbrain
trochlear nerve stems from
CN IV -only cranial nerve from DORSAL surface of brainstem -wraps laterally around the cerebral crus
glossopharyngeal nerve stems from
CN IX -postolivary sulcus -closest to pons
trigeminal nerve stems from
CN V -midpontine surface
abducens nerve stems from
CN VI -medial pontomedullary sulcus between pons and medulla
facial nerve stems from
CN VII -cerebellar pontine angle/ pontomedullary sulcus -more medial
Vestibulocochlear nerve stems from
CN VIII -cerebellar pontine angle/ pontomedullary sulcus -more lateral
vagus nerve stems from
CN X -postolivary sulcus -between glossopharyngeal and accessory
accessory nerve stems from
CN XI -spinal and cranial parts -postolivary sulcus -closest to spinal cord
hypoglossal nerve stems from
CN XII -preolivary sulcus (medial brain stem)
