Brainstem Anatomy

General Organization

General organization Sensory cranial nerve nuclei are lateral Sensory cranial nerve nuclei are lateral Motor cranial nerve nuclei are medial Motor cranial nerve nuclei are medial Visceral motor and visceral sensory nuclei are intermediate Visceral motor and visceral sensory nuclei are intermediate

Pyramidal decussation Medullary pyramid CN IX CN X CN XII Inferior olive Obex Tubercuum gracilis Tubercuum cuneatus 4 th ventricle

Tracts Depending on direction of fibers, cut in long section or cross section. Depending on direction of fibers, cut in long section or cross section. Most tracts are in cross section because they run from rostral to caudal (“descending”) or caudal to rostral (“ascending”). Most tracts are in cross section because they run from rostral to caudal (“descending”) or caudal to rostral (“ascending”). Image of the brainstem of a Brainbow mouse, by Jean Livet of Harvard UniversityBrainbow mouse

Sympathetics to eye Sympathetic chain Superior cervical ganglion T1 T2 T3 Hypothalamospinal tract *Damage will produce Horner’s syndrome: anhidrosis, meiosis (small pupil); minor ptosis (drooping of the upper lid)

Pyramidal Decussation

Pyramid Pyramidal decussation Spinal tract of trigeminal Spinal nucleus of trigeminal Cervical motor neurons Fasciculus cuneatus Fasciculus gracilis Nucleus gracilis Central canal Lateral corticospinal tract Spinal accessory motor neurons Anterolateral system

Pyramidal Decussation

Pyramid Pyramidal decussation Lateral corticospinal tract Spinal tract of trigeminal Spinal nucleus of trigeminal Cervical motor neurons Fasciculus cuneatus Fasciculus gracilis Nucleus gracilis Central canal Nucleus cuneatus Anterolateral system Spinal accessory motor neurons

Caudal Medulla

Pyramid Medial lemniscus Internal arcuate fibers Spinal tract of trigeminal Spinal nucleus of trigeminal Fasciculus cuneatus Nucleus gracilis Central canal Nucleus cuneatus Central gray mater Medial Longitudinal fasciculus Anterolateral system

Caudal Medulla

Pyramid Medial lemniscus Internal arcuate fibers Spinal tract of trigeminal Spinal nucleus of trigeminal Fasciculus cuneatus Nucleus gracilis Central canal Nucleus cuneatus Central gray mater Medial longitudinal fasciculus Hypoglossal nucleus Inferior olivary nucleus Anterolateral system

Mid-Medulla

Mid-Medulla Pyramid Medial lemniscus Internal arcuate fibers Spinal tract of trigeminal Spinal nucleus of trigeminal Fasciculus cuneatus Nucleus gracilis Solitary nucleus & tract Nucleus cuneatus Obex Medial longitudinal fasciculus Hypoglossal nucleus Inferior olivary nucleus Anterolateral system Dorsal motor nucleus of vagus Ext. cuneate n.

Mid-Medulla

Mid-Medulla Pyramid Medial lemniscus Internal arcuate fibers Spinal tract of trigeminal Spinal nucleus of trigeminal Solitary nucleus & tract Nucleus cuneatus Obex Medial longitudinal fasciculus Hypoglossal nucleus Inferior olivary nucleus Anterolateral system Dorsal motor nucleus of vagus Ext. cuneate n. Inf cerebellar peduncle

Mid-Medulla

Mid-Medulla Pyramid Medial lemniscus Spinal tract of trigeminal Spinal nucleus of trigeminal Solitary nucleus & tract Vestibular nucleus Medial longitudinal fasciculus Hypoglossal nucleus Inferior olivary nucleus Anterolateral system Dorsal motor nucleus of vagus Ext. cuneate n. Inf cerebellar peduncle

Rostral Medulla

Pyramid Medial lemniscus Spinal tract of trigeminal Spinal nucleus of trigeminal Choroid plexus Vestibular nucleus Medial longitudinal fasciculus Cerebellar cortex Inferior olivary nucleus Anterolateral system 4th ventricle Inf cerebellar peduncle

Rostral Medulla

Pyramid Medial lemniscus Spinal nucleus & tract of trigeminal Vestibular nucleus Medial longitudinal fasciculus Dentate nucleus Inferior olivary nucleus Anterolateral system 4th ventricle Inf cerebellar peduncle Dorsal cochlear n

Caudal Pons

Pontine nuclei Trapezoid body Anterolateral system Facial nerve Medial longitudinal fasciculus Corticofugal fibers Medial lemniscus 4th ventricle Middle cerebellar peduncle Facial nucleus Abducens nucleus Abducens nerve Raphe nucleus

Mid to Rostral Pons

Pontine nuclei Anterolateral system Superior cerebellar peduncle Medial longitudinal fasciculus Corticofugal fibers Medial lemniscus 4th ventricle Middle cerebellar peduncle Trigeminal nerve Trigeminal nuclei

Mid to Rostral Pons

Pontine nuclei Anterolateral system Superior cerebellar peduncle Medial longitudinal fasciculus Corticofugal fibers Medial lemniscus Raphe nuclei Middle cerebellar peduncle

Rostral Pons

Pontine nuclei Anterolateral system Superior cerebellar peduncle Medial longitudinal fasciculus Corticofugal fibers Medial lemniscus Raphe nuclei Lateral lemniscus Cerebral aqueduct

Pontomesencephalic Junction

Pontine nuclei Anterolateral system Superior cerebellar peduncle Medial longitudinal fasciculus Corticofugal fibers Medial lemniscus Inferior colliculus Lateral lemniscus Cerebral aqueduct

Pontomesencephalic Junction

Pontine nuclei Anterolateral system Superior cerebellar peduncle Medial longitudinal fasciculus Corticofugal fibers Medial lemniscus Inferior colliculus Periaqueductal gray Cerebral aqueduct

Mesencephalon

Mesencephalon Cerebral peduncle Anterolateral system Superior cerebellar peduncle Substantia nigra Medial lemniscus Superior colliculus Periaqueductal gray Cerebral aqueduct Medial geniculate Red nucleus Oculomotor nucleus and nerve

Rostral Mesencephalon

Cerebral peduncle Anterolateral system Superior cerebellar peduncle Substantia nigra Medial lemniscus PinealPeriaqueductal grayCerebral aqueductPretectal n Red nucleus Oculomotor nerve Thalamus

Atlas of brain stem anatomy