Neuropathology Lecture 01 Neuropathology Cerebral Edema, Intracranial Shift, Herniation

Front 1

Back 1

Neuron

Front 2

Back 2

Neuron

Front 3

What are the domains of a neuron?

Back 3

Soma (cell body)
Dendrites (input)
Axon (output)

Front 4

Back 4

Astrocytes

Front 5

Back 5

Astrocytes

Front 6

Describe astrocytes

Back 6

-Major glial cell of the brain
-Stellate or star shaped
-Attached to a number of other elements in the brain
-Astrocyte processes overlay blood vessels in brain
-Attach to pial surface of brain
-Enfold synapses
-Instruct epithelial cells to make tight junctions for BBB
-Have transporters for many neurotransmitters
-Control neurotransmitter and potassium levels in brain
-Promote growth and facilitate synaptic conduction

Front 7

Describe oligodendrocytes

Back 7

-Myelinating cells of the CNS
-One oligodendrocyte wraps many neurons
-Nodes of Ranvier in neurons are areas between myelin with lots of Na channels
-Oligodendrocytes and/or myelin are destroyed in many pathological processes

Front 8

Back 8

Oligodendrocyte

Front 9

Back 9

Node of Ranvier

Front 10

Describe ependymal cells

Back 10

-Line the ventricular walls
-Ciliated single columnar or cuboidal epithelium
-Cilia moves CSF
-CSF is made by choroid plexus, it fills ventricles and bathes brain
-

Front 11

Describe the choroid plexus

Back 11

-Produces CSF
-Where brain interfaces with mesenchymal elements
-Has a core of fibrous tissue and blood vessels
-Lined with choroid plexus epithelium that is contiguous with ependymal cells
-CSF is an ultrafiltrate of plasma filtered by the choroid plexus

Front 12

Back 12

Ependymal cells

Front 13

Back 13

Choroid plexus

Front 14

Describe microglia

Back 14

-Hematopoetically derived
-Enter brain during embryonic life and stay there forever
-From monocyte lineage
-Cover most of the volume of the brain
-APCs
-Have phagocytic activity

Front 15

Describe the distribution of blood vessels in the brain

Back 15

-Brain is highly vascularized
-Blood vessels come up over the surface of the brain and enter radially
-Cortex (gray matter) has many more vessels than white matter

Front 16

How many choroid plexuses are there?

Back 16

4
One in each lateral ventricle and 2 in the 4th ventricle

Front 17

What connects the 3rd and 4th ventricles?

Back 17

Aqueduct of Silvius

Front 18

What is the roof of the 4th ventricle? The base?

Back 18

Roof: Cerebellum
Base: Brain stem

Front 19

What connects the 4th ventricle and the subarachnoid space?

Back 19

Foramina

Front 20

Where is CSF resorbed? How often is CSF resorbed?

Back 20

Arachnoid granulations
Several times a day

Front 21

How much CSF is in the average adult?

Back 21

150ml

Front 22

Back 22

Microglia

Front 23

Back 23

Microglia

Front 24

Back 24

Blood vessels in the brain
The cortex has more than the white matter

Front 25

What is hydrocephalus? What causes it?

Back 25

An enlargement of one of more of the ventricles
It can be caused by:
-An overproduction of CSF (rare)
-A block of CSF through the ventricles
-A block of CSF resorption

Front 26

When does overproduction of CSF occur?

Back 26

With choroid plexus papillomas

Front 27

What is an obstructive/non-communicating hydrocephalus?

Back 27

Hydrocephalus caused by a block of CSF flow through ventricles.

This occurs with aqueductal stenosis, masses in the ventricle system and foramina, and with malformations (Arnold Chiari)

Front 28

What is a communicating hydrocephalus?

Back 28

A hydrocephalus caused by a block in the resorption of CSF

This can be caused by meningitis, subarachnoid hemorrhage, or dural sinus thrombosis

Front 29

What is the relationship between intracranial pressure and brain volume?

Back 29

-Volume inside skull is fixed
-With intracranial hemorrhage, blood leaks into brain
-There are some thing in the brain, CSF in ventricles and subarachnoid space, that can be squeezed out
-Eventually there is nothing left to squeeze
-After that pressure increases dramatically

Front 30

Describe the BBB

Back 30

-Endothelial cells form tight junctions
-Outside endothelial cells is basement membrane
-Then there are foot processes of astrocytes
-BBB restricts cells and macromolecules from the blood directly entering the brain

Front 31

What is often responsible for rapid expansion of the brain?

Back 31

Edema

Front 32

What is edema?

Back 32

Increase in volume and weight due to accumulation of fluid.

Edema can accompany rapid or slow expansion of the brain. The rapid expansions are much more problematic.

Front 33

What is vasogenic edema?

Back 33

-Edema due to increased cerebrovascular permeability.
-This occurs when the BBB is damaged and opens up.
-It allows serum for the capillary systems to enter the brain.
-Fluid can produce an increase in intracranial pressure
-Duration of BBB incompetence varies with the type of pathology

Front 34

What does the progression and extent of vasogenic edema depend on?

Back 34

1. Level of systolic blood pressure (when intracranial pressure equals systolic BP, no more fluid will enter brain)
2. Duration of BBB incompetance

Front 35

What can cause vasogenic edema?

Back 35

(BBB breakdown)
Trauma
Infarction
Hemorrhage
Neoplasms
Infections
Inflammation

Tumors and metastatic cancers tend not to have BBB anymore. The blood vessels that feed most metastatic cancers don’t maintain a BBB. The blood vessels that feed malignant gliomas don’t maintain a BBB.

Front 36

Describe brain herniations

Back 36

-Rapidy growing hemorrhage or tumor would increase pressure in one area and push brain in opposite direction
-Brain can move under free edges of dural folds
-Cingulate gyrus can be pressed under the corpus callosum under the free edge of the falx cerebri
-Uncus can be pushed over free edge of tentorium
-Cerebellum can be pressed into the foramen magnum

Front 37

What is the big issue with brain herniations?

Back 37

It is not the area doing the pushing, it is the area being pressed against

Front 38

Back 38

Patient with metastatic carcinoma - mass lesion/cerebral edema
Subfalcine herniation. Normal gyri and sulci are effaced.

Front 39

Back 39

Intracerebral hemorrhage
Probably on the basis of hypertension. Hypertensive hemorrhages usually come in under arterial pressure because the arterioles break. This produces a pressure gradient and forced the brain in a particular direction.

Front 40

Back 40

Herniations from subdural hematoma

You see the flattening side of the brain due to eh subdural hematoma. There is a shift tin the ventricles. This is easy to pick up on a CT or MRI.

Front 41

What occurs with uncal herniation at the midbrain level?

Back 41

1. CNIII- pupil dilation on side of herniation
2. PCA/SCA - visual cortex/occipital lobe infarction
3. Cerebral peduncles compression -ipsi (if contralateral peduncle is compressed) or contralateral hemiparesis (if ispilateral peduncle is compressed)
4. AP compression - aqueductal compression hydrocephalus

Front 42

Back 42

Uncal herniation

Front 43

Back 43

Medial occipital infarction (visual cortex) from PCA compression from uncal herniation

Front 44

What is a duret hemorrhage? How do they occur?

Back 44

Bleeding in the midbrain and pons

As the pressure and herniation start to now move down further it not only compresses the midbrain but also starts to compress the pons and medulla. It can force the pons and medulla caudally. The blood vessels that serve it come from the circle of Willis and are tehtered at the circle of Willis. If you put a lot of pressure down on those vessels they bleed and produce hemorrhages within the brain stem. These are fatal.

Front 45

Back 45

Duret hemorrhage

Front 46

Back 46

Duret hemorrhage

Front 47

Back 47

Cerebellar tonsillary herniation

Compression of the medulla. What happens here is that the medulla gets compressed. The medulla is where your respiratory and cardiovascular synchronicity and automatic centers are. Patients who get this far end up with abnormalities in breathing and heart rate. This is fatal as well.

Front 48

What are the sequelae of rapidly expanding supratentorial lesions?

Back 48

1. Uncal, hippocampal herniation
2. Compression of ipsilateral CN III
3. A-P compression of midbrain
4. Obstructive hydrocephalus
5. Cerebral peduncle compression (ipsi- or contralateral hemiparesis)
6. PCA compression (ischemica of visual cortex and thalamus)
7. Duret hemorrhages (central stem)
8. Tonsillar herniation - compression of medulla