1. David A. Morton, Ph.D. Jan 17th, 2013
Brainstem Medulla
David A. Morton, Ph.D.
Jan 17th, 2013

2. Objectives
Describe the trajectory of the cranial nerves, their components, and their functions
Identify and locate the CN’s associated with the medulla, the pons and the midbrain.
Explain how cranial nerves differ from spinal nerves
List the cranial nerves that contain parasympathetic fibers, the location of their nuclei, and their function
Recognize the major internal and external landmarks on the dorsal and ventral surface of the brain stem, so that you can determine if a gross or stained cross section is medulla, pons or midbrain.
Identify on a typical cross section all the brain stem nuclei containing motor neurons that end on striated muscle.
Explain why cranial nerves are so important in localizing lesions.
Name reflexes that test these nerves and brain stem levels.
Relate branches of the vertebrobasilar blood supply to the medulla and pons explaining the deficits that would occur with vascular occlusion.

3. Internal anatomy of brainstem
Alar
Basal
Sulcus limitans
Medulla
Som S VS VM SM BM
The fate of the alar and basal laminae
Why are brain stem sensory nuclei lateral to motor nuclei in brainstem?
Alar
Basal
Sulcus limitans
Spinal cord
Som S VS VM SM

4. Medulla oblongata External anatomy: Pyramid Olive
CNN VIII, IX, X, XI and XII
Fourth ventricle
Vertebral arteries
4th vent.
VIII P O
IX & X
Medulla
XII XI O P
Horizontal section

5. Solitary nuclei and tract
Medulla oblongata
Solitary nuclei and tract
Alar
Basal
Medulla
Som S VS VM SM BM
Spinal trigeminal nucleus
Sulcus limitans
Inf sal and dorsal vagal nuclei
Hypoglossal nucleus
Nucleus ambiguus

6. Medulla Oblongata Hypoglossal nucleus (CN XII) Somatic motor
Comparable to ventral horn
Tongue muscles

7. Medulla Oblongata Dorsal motor nucleus (CN X) Visceral motor
Comparable to lateral horn
Origin of preganglionic parasympathetic neurons

8. Medulla Oblongata Inferior salivatory nucleus (CN IX) Visceral motor
Comparable to lateral horn (can not see it on brains)
Origin of preganglionic parasympathetic neurons to otic ganglion

9. Medulla Oblongata Nucleus ambiguus (CN IX and X)
Branchial (spec visc) motor
Origin of BM neurons for IX and X

10. Medulla Oblongata Reticular formation
Forms the central core of brain stem
Nuclear groups not obvious

11. Medulla Oblongata Vascular supply: Vertebra artery
Anterior spinal artery
PICA
PICA
Vert
Ant sp

12. Objectives
Explain what the meninges cover and what spaces they surround.
For each meningeal space describe a classic source for blood in the space.
Describe where CSF is produced and how it circulates and is removed.
Name the most likely sites of obstruction of CSF circulation and the consequences.
Explain how the Blood Brain Barrier is different from the CSF Brain interface.

13. Cranial Meninges
Dura mater
Arachnoid mater
Pia mater

14. Cranial Meninges Dura mater (2 layers in the skull)
Periosteal layer and Meningeal layer
Dural venous sinus
Dural
Venous
sinuses
Cerebral vv.

15. Meningeal hemorrhages
Blood in meningeal spaces or potential spaces
Epidural hemorrhage
Subdural hemorrhage
Subarachnoid hemorrhage

16. Epidural space
Dura mater
Middle meningeal artery

17. Epidural hemorrhage Torn middle meningeal a.
1. Epidural hemorrhage: In potential space between skull and cranial dura, or in the spinal cord the space external to the dura

18. Epidural hemorrhage
Can lead to herniation of brainstem through the foramen magnum.

19. Subdural space Dura mater Bridging cerebral vein
Courses between cerebrum and dural venous sinus

20. Subdural hemorrhage Torn bridging cerebral v.
2. Subdural hemorrhage: In potential space between dura and arachnoid

23. What space is the artery located?
Dural
Venous
sinuses

24. Brain arteries – Subarachnoid space
Internal carotid artery (ICA)
Ophthalmic
Anterior cerebral
Middle cerebral
Vertebral artery
PICA
Basilar
AICA
SCA
Posterior cerebral
Cerebral arterial circle of Willis
Anterior communicating
ICA
Posterior communicating

25. Subarachnoid hemorrhage
3. Subarachnoid hemorrhage: In subarachnoid space filled with CSF
a. Typically due to rupture of a saccular aneurysm. – 25-50% fatal.
b. Typical location of aneurysms around circle of Willis
c. Worst headache of your life due to endothelins, nitric oxide, and arachidonic acid metabolites irritate blood vessels and cause vasospasm.
d. Cigarette smoking and hypertension (estimated to be present in about half of these patients).
e. Develop over time because of an underlying defect in the media of the vessel

26. Stroke

27. Organize the following terms:
Cerebral aqueduct
Lateral ventricle
4th ventricle
Arachnoid granulations
Superior sagittal sinus
Lateral apertures
3rd ventricle
Subarachnoid space
Aqueduct of Sylvius
Interventricular foramen
Foramen of Magendie
Median aperture
Foramen of Monro
Foramen of Luschka
Choroid plexus
Lateral ventricle
Mesencephalic aqueduct

28. The following terms are in order:
Choroid plexus
Lateral ventricle
Lateral ventricle
Interventricular foramen
Foramen of Monro
3rd ventricle
Cerebral aqueduct
Aqueduct of Sylvius
Mesencephalic aqueduct
4th ventricle
Lateral apertures
Median aperture
Foramen of Luschka
Foramen of Magendie
Subarachnoid space
Arachnoid granulations
Superior sagittal sinus

29. The ventricular system
The ventricles, lined by ependymal cells, are obvious internal landmarks, and are important as internal structures to relate other structures to. Try to visualize them and rotate them with the brain. They will form the “wire frame” for our orientation to the brain.

30. The ventricular system

31. The ventricular system
Hydrocephalus is dilation of all or part of the ventricular system due to obstruction of CSF flow. There are two types:
1. Obstructive (non-communicating) hydrocephalus. Block in the ventricular system or the outlet foramina.
2. Communicating (non-obstructive) hydrocephalus. Block in the subarachnoid space or the arachnoid granulations.
a. Meningitis followed by scarring.
b. Subarachnoid hemorrhage, meningeal fibrosis and scarring

33. Hydrocephaly
1. Obstructive (non-communicating) hydrocephalus. Block in the ventricular system or the outlet foramina.

34. 2. Communicating (non-obstructive) hydrocephalus
2. Communicating (non-obstructive) hydrocephalus. Block in the subarachnoid space or the arachnoid granulations.
Hydrocephaly

35. Figure 12.26a Formation, location, and circulation of CSF.
Superior
sagittal sinus 4
Choroid
plexus
Arachnoid villus
Interventricular
foramen
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater 1
Right lateral ventricle
(deep to cut)
Choroid plexus
of fourth ventricle 3
Third ventricle
CSF is produced by the
choroid plexus of each
ventricle. 1
Cerebral aqueduct
Lateral aperture
Fourth ventricle
CSF flows through the
ventricles and into the
subarachnoid space via the
median and lateral apertures.
Some CSF flows through the
central canal of the spinal cord. 2
Median aperture 2
Central canal
of spinal cord
CSF flows through the
subarachnoid space. 3
(a) CSF circulation
CSF is absorbed into the dural venous
sinuses via the arachnoid villi. 4