1. CROSS SECTIONAL
ANATOMY OF BRAIN
STEM
PRESENTER – Dr. R.S.K. Karthik, 2nd year
M.Ch resident
MODERATOR –Dr. M.V. Vijayasekhar , MS
M.Ch , Professor and HoD
5. Ventral – Dorsal Organization
Tegmentum
Anterior cell body-rich
areas, floor of brainstem:
red nuclei, substantia
nigra, reticular formation
6. Ventral – Dorsal Organization
Tectum
Roof of the
brainstem: superior
colliculi, inferior
colliculi: corpus
quadrigemina
Cerebellum
Cuneatus, gracilis
(medulla)
9. Internal Columns of Nuclei
III, IV, VI, XII
V, VII, N. ambiguus, XII
EW, Salivatory, DMN X
V, VII, IX, X
N. Solitary tract
VIII
10. Subdivisions of Vertical
Columns
• Motor nuclei
– Somatic motor
• closest to midline
• eyes, tongue
• CN III, IV, VI, XII
– Branchial motor
• Lateral position
• Branchial arches: chewing,
expression, middle ear, pharynx,
larynx, sternomastoic, trapezius
• CN V, VII, XI
• N. ambiguus (IX, X)
– Visceral motor
• ventral / ventrolateral
• Parasympathetic: glands, smooth
muscle, heart, lungs, GI above
splenic flexure
• Edinger-Westfall (III)
• Sup. & Inf. salivatory (VII)
• Dorsal motor nucleus of X
• Sensory nuclei
– General sensory
• lateral to branchial motor
• Face, sinuses, meninges
• All modalities
• CN V mainly
• Also CN VII, IX, X
– Visceral sensory
• lateral to visceral motor
• Taste; cardiorespiratory, GI info
• N. of the solitary tract (CN VII,
IX, X)
– Special sensory
• furthest lateral
• Balance; hearing
• CN VIII (vestibular)
• CN VIII (cochlear)
12. Internal Structure of Medulla
Cross section at three levels
• Level of pyramidal decussation
• Level of lemniscal decussation
• Level of inferior olivary nuclei
13. Level of Pyramidal
Decussation
Pyramidal tract
Lateral corticospinal tract
75 – 90%
Anterior corticospinal tract -- fibers to innervate muscles of trunk
Spinal
nucleus
of V
From pons
to C4
Gracile
nucleus
Contralateral movement
14. Internal Structure of Medulla
Cross section at three levels
• Level of pyramidal decussation
• Level of lemniscal decussation
• Level of inferior olivary nuclei
15. Level of Lemniscal
Decussation
Medial lemniscus
Carries 2nd order sensory
neurons to VPL thalamus
Gracile nucleus
Cuneate
nucleus
Internal arcuate
fibers
MLF
Pyramids
Position & vibration sense
16. Internal Structure of Medulla
Cross section at three levels
• Level of pyramidal decussation
• Level of lemniscal decussation
• Level of inferior olivary nuclei
17. Level of Inferior Olives
Inferior cerebellar
peduncle =
Restiform body
Inferior olivary
nuclei
Relay between cortex,
vestibular nuclei,
cerebellum, basal ganglia,
and dorsal column nuclei
MLF
Vestibular nuclei
Medial Inferior
Hypoglossal nucleus
CN XII
Arcuate nuclei pontine nuclei
19. Cranial Nuclei of the Medulla
N. solitarious
Sensory nucleus
for
CN VII, IX, X
20. Cranial Nuclei of the Medulla
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Spinal
trigeminal tract
CN V, VII, IX, X
21. Cranial Nuclei of the Medulla
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Spinal
trigeminal tract
CN V, VII, IX, X
22. Cranial Nuclei of the Medulla
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Spinal
trigeminal tract
CN V, VII, IX, X
Dorsal motor
nucleus of X
23. CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Spinal
trigeminal tract
CN V, VII, IX, X
24. CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Posterior 1/3 of
the tongue
Spinal
trigeminal tract
CN V, VII, IX, X
25. CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Posterior 1/3 of
the tongue
Spinal
trigeminal tract
CN V, VII, IX, X
Sensation behind
ear
26. CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
Stylopharyngeus
(lifts pharynx)
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Posterior 1/3 of
the tongue
Spinal
trigeminal tract
CN V, VII, IX, X
Sensation behind
ear
27. CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
Stylopharyngeus
(lifts pharynx)
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Posterior 1/3 of
the tongue
Inf. salivatory
nucleus
Parotid gland,
parasympathetic
Spinal
trigeminal tract
CN V, VII, IX, X
Sensation behind
ear
28. CN X: Vagus Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Spinal
trigeminal tract
CN V, VII, IX, X
“Wanderer”
29. CN X: Vagus Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Taste, epiglottis
Cardiorespiratory
Spinal
trigeminal tract
CN V, VII, IX, X
“Wanderer”
30. CN X: Vagus Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Taste, epiglottis
Cardiorespiratory
Spinal
trigeminal tract
CN V, VII, IX, X
Ear
“Wanderer”
31. CN X: Vagus Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
Pharynx
Larynx
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Taste, epiglottis
Cardiorespiratory
Spinal
trigeminal tract
CN V, VII, IX, X
Ear
“Wanderer”
32. CN X: Vagus Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
Pharynx
Larynx
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Taste, epiglottis
Cardiorespiratory
Dorsal motor
nucleus of X
Spinal
trigeminal tract
CN V, VII, IX, X
Ear
“Wanderer”
33. CN X: Vagus Nerve
N. ambiguus
Motor nucleus for
CN IX, X & XI
Pharynx
Larynx
N. solitarious
Sensory nucleus
for
CN VII, IX, X
Taste, epiglottis
Cardiorespiratory
Dorsal motor
nucleus of X
Parasympathetic,
preganglionic
Spinal
trigeminal tract
CN V, VII, IX, X
Ear
“Wanderer”
36. Pontine Nuclei
Pontine nuclei
Project to cerebellum
Continuation of arcuate
nuclei (over pyramids)
Input (ipsilateral)
Motor cortex
Sensory cortex
Association cortex
Cingulate cortex
Output (contralateral)
Transverse crossing
via middle cerebellar
peduncle to cerebellum
37. Internal Structure of the Pons
Cross section at three levels
• Level of facial nucleus (CN VII)
• Level of middle cerebellar peduncle
• Level of locus ceruleus
38. Pons
Descending upper motor neurons
Connection of pons to
cerebellum
Restiform body (inf.
cerebellar peduncle)
Middle cerebellar peduncle
Medial lemniscus
Ascending 2nd order
sensory neurons
4th Ventricle
39. Cranial Nerves of Lower
Pons
CN VIII – Vestibular Nuclei
Pure sensory lateral location
Balance
Posterior view:
Cerebullum cut away
40. Cranial Nerves of Lower
Pons
CN VIII –
Vestibular Nuclei
(Cochlear Nuclei)
41. Cranial Nerves of Lower
Pons
CN VII nucleus – Facial nerve
Muscles of face
At a slightly higher level
CN VI nucleus – Abducens
nerve
Abduction of eye
Longest, most vulnerable CN
42. Cranial Nerves of Lower
Pons
CN VII nucleus - Facial nerve
Muscles of face
43. Cranial Nerves of Lower
Pons
CN VI nucleus – Abducens
nerve
Abduction of eye
44. Internal Structure of the Pons
Cross section at three levels
• Level of facial nucleus (CN VII)
• Level of middle cerebellar peduncle
• Level of locus ceruleus
Anterior view
48. Mid Pons
Pontine nuclei
Lateral lemniscus
Medial lemniscus fibers
from dorsal column
(position and vibration)
Trigeminal
tract pain,
temperature,
touch from
contralateral
face
Lemniscal sensory system – in tegmentum of the pons
49. Cranial Nerve of the Mid Pons
4th Ventricle
CN V
Motor trigeminal
nucleus
50. Cranial Nerve of the Mid Pons
4th Ventricle
CN V
Motor trigeminal
nucleus
Principal trigeminal sensory nucleus
51. Cranial Nerve of the Mid Pons
4th Ventricle
CN V
Motor trigeminal
nucleus
Principal trigeminal sensory nucleus
Trigeminal
fascicles
Trigeminal
nerve
52. Internal Structure of the Pons
Cross section at three levels
• Level of facial nucleus (CN VII)
• Level of middle cerebellar peduncle
• Level of locus ceruleus
56. Upper Pons
4th ventricle cerebral aqueduc
MLF
Locus ceruleus
Primary source of
noradrenergic
innervation to the
brain
Neurons contain
melanin
57. Upper Pons
4th ventricle cerebral aqueduc
MLF
Parabrachial Nucleus
Also release
catecholamines
Neurons also
contain melanin
58. Upper Pons
4th ventricle cerebral aqueduc
MLF
Pediculopontine Nucleus
Some neurons
release
acetylcholine
Other neurons
release glutamate
They assist in
learning and
voluntary motor
control,
e.g. locomotion,
saccadic eye