Anatomical Overview of Brainstem

General Functions of the Brainstem

• relays information between the brain and spinal cord (motor and sensory)

• relays information to and from cerebellum

• integrates information between systems

  • ex: eye movements with vestibular input

• helps regulates vital functions:

  • respiration, HR, consciousness & arousal, pain modulation, etc.

  • anatomically associated with 10 of the 12 pairs of cranial nerves

Brainstem

Ventral View

Ventral brainstem: anatomical structures

Midbrain: cerebral peduncles

Pons: basilar pons

• *middle cerebellar peduncle

Medulla: pyramids

• Olives

• (pyramidal/motor decussation)

Cerebral peduncles

midsagittal view

basilar pons

midsagittal view

pyramids

midsagittal view

Cranial Nerves associated with brainstem (ventral view)

Midbrain:

• CN III (oculomotor)

• CN IV (trochlear)

Pons:

• CN V (trigeminal)

• CN VI (abducens)

• CN VII (facial)

• CN VIII (vestibulocochlear)

Medulla:

• CN IX (glossopharyngeal)

• CN X (vagus)

• CN XI (accessory)

• CN XII (hypoglossal)

Dorsal brainstem: cranial nerve

Midbrain: CN IV (trochlear)

Dorsal brainstem: anatomical structures

Midbrain:

• superior colliculus (tectum)

• inferior colliculus (tectum)

• superior cerebellar peduncle (S)

Pons:

• middle cerebellar peduncle (M)

Medulla:

• inferior cerebellar peduncle (I)

• cuneate tubercle

• gracile tubercle

Midsagittal view

Dorsal View

midbrain

smallest segment of brainstem - continuous with pons and diencephalon

midsagittal: midbrain

cerebral peduncles (crus cerebri)

Brainstem Sections:

rostal midbrain at level of superior colliculus

Rostral Midbrain: cross section

Caudal midbrain: cross section

Midbrain Blood supply

Midbrain Blood Supply: Posterior cerebral artery

Midsagittal: pons

two regions: tegmentum and basilar

Mid-Pons: Cross section

Pons Blood Supply

Medulla

Medulla:

• CN IX (glossopharyngeal)

• CN X (vagus)

• CN XI (accessory)

• CN XII (hypoglossal)

Rostal Medulla

Caudal Medulla

Rostral Medulla: Cross section

Medulla

Rostal (open)

Caudal (closed)

Caudal Medulla: cross section

Blood Supply of Medulla

Anterior spinal A., vertebral A., and PICA

Caudal Medulla: Brainstem Blood supply

Rostal Medulla: Brainstem Blood supply

Blood Supply of CNS

• internal carotid system (anterior circulation)

• vertebral/basilar arterial system (posterior circulation)