Brain Herniations

Name 5 Classic brain herniations

1. Subfalcine/cingulate gyrus herniation

2. unilateral temporal/uncal, trans-tentorial herniation

3. Cerebellar tonsil herniation into the foramen magnum

4. Upward tenting of cerebellum thru tentorial notch

5. Herniations thru skull defects (post surgery or post trauma

Upward Herniation of Cerebellum

In what clinical context could this happen?

Patient has a tumor, the surgeon removed some fluid from a ventricle to relieve ICP/make room, and the resulting negative pressure causes the cerebellum to herniate upward thru the tentorial notch (trans-tentorial 'tenting' herniation)

Uncal Herniation

Clinical presentation?

What can become compressed in extreme cases of uncal herniation, and what is the clinical result

Compression of the PCA and CN III

Presents w/ headache and mydriasis; why? Because oculomotor nerve provides parasympathetics to the eye --> w/o CN III tone, all you have is sympathetic stim, causing dilation 

extreme uncal herniation can compress the midbrain, which is essential in breathing and cardiac reg (this compression is not compatible with life!)

Clinical Triad of Trans-Tentorial Herniation

1. Dilated pupil

2. PCA occluded

3. Midbrain compression

(Life and death situation)

Five Consequences of Uncal Herniation:

Number 1 --> Pressure Necrosis 

3 Parts of the brain it affects?

What is Kernohan's notch?

Clinical effects?

 Pressure necrosis, affects:

Uncus (of temporal lobe)

Hippocampus

Cerebral peduncle --> causes Hemiparesis 

Kernohan's notch = cerebral peduncle indentation, secondary condition caused by primary injury on the opposite hemisphere.  Its an ipsilateral condition, in that a primary injury on the left side will cause a Kernohan's notch on the right cerebral peduncle, resulting in motor impairment of the left side (the same side as the primary injury.

Five Consequences of Uncal Herniation:

Number 2 --> Nerve Compression

Five Consequences of Uncal Herniation:

Number 3 --> Arterial Compression

Clinical effects?

Occlusion of one or both PCA's

Causes infarcts to the hippocampus (causing memory disorders)

and calcarine region (cortical blindness & other visual defecits)

Five Consequences of Uncal Herniation:

Number 4 --> Duret Hemorrhages

Five Consequences of Uncal Herniation:

Number 2 --> Obstructive Hydrocephalus

Consequences of cerebellar tonsilar herniation (3)

What are 2 possible causes of cerebellar tonsillar herniation?

1. Blockage of CSF flow in foramen magnum --> hydrocephalus

2. compression of medulla, disrupting reg of respiratory drive and heart rhythmn

3. Necrosis of cerebellar tissues

Possible Causes:

1. cerebellar tumor

2. Cerebellar hemorrhage -- due to excessive cocaine use

Presence of Nucleus, Nucleolus

Nissle substance = granular basophilic material

rough ER

prominent mitochondria

Astrocytes

functions in the NS

remarkable histo features

1.Principle supporting cell of the CNS, responds rapidly and dramatically to CNS injury, responsible for gliosis and scarring (like when cerebral infarct occurs)

2. Take part in the blood-brain barrier, which is composed of endothelial cells surrounded by astrocyte processes

Histo:

the largest of the glial cells, possess a naked nucleus w/ no nucleolus

Cytoplasm highlighted w/ GFAP antibody

Describe the following Characteristic Histopathological changes that occur in each of these CNS cells:

Neurons:

Astrocytes:

Oligodendrocytes:

endothelium:

microglia:

Neurons: hypoxic/ischemic damage --> red neurons

inclusions (eg Lewy bodies in the substantia nigra of Parkinson's patients, or Pick bodies)

Astrocytes: Gliosis

Alzheimer type II astrocytes

Oligodendrocytes: tau inclusions seen in 1. multiple system atrophy and 2. PML

endothelium: hypertrophy/hyperplasia

microglia: activation, grouped together to form nodules

What is a common complication of penetrating brain traumas?

What does intraxial vs extraxial hemorrhage mean? One cause/example of each

Complication: infection!

Extra-axial = outside of the brain, like a subdural hematoma

or an epidural hematoma (often caused by skull fracture)

Intra-axial is within the brain tissue itself; brain herniations may cause intra-axial hemmorhage

Did you lose consiousness?

Do you have a headache?

Do you have nausea/did you vomit?

If yes to any of these, must keep them in the hospital for monitoring for 24 hours

What vessel is most often the cause of epidural hematoma, and what is a secondary complication of this?

Zagzag said this is the most important concept of this lecture

2 other possible complications?

How does subdural hematoma course/progression compare to that of epidural?

Epidural hematoma is the result of middle meningeal artery tear, thus progression is generally rapid, and can secondarily result in uncal herniation

Other less important/frequent complications:

1. Subfalcine (cingulate) herniation

2. Shifting of the lateral ventricle

Subdural hematoma is often due to rupture of the bridging veins, its veins so the hemorrhage is slower, patient may not present for weeks or even months

Cerebral Contusions - describe

What is a remote contusion, and what are its results?

What are coup/contre-coup contusion?

Surface lesions, wedge shape, can be shallow or large

Old or remote contusions are associated with resorption of the injured tissue, resulting in various degrees of cavitation, and has the potential to cause seizures

Coup:  One part of the brain is hit, and the oppostie side in a line w/ the impact bangs against the skull

Diffuse Axonal Injury

Characteristic neuropath finding?

Cause of what shitty clinical condition?

Histo:  Axonal spheroids, aka axon contraction balls

DAI is the cause of coma

Subfalcine/Cingulate Herniation

What is it?

Results?

(the most common cerebral herniation)

Swelling causes the cingulate gyrus to be displaced under the falx cerebri

Results:

Increased ICP

Potential compression of the anterior cerebral artery

Patient may present w/ abnormal posturing, and/or coma

Cingulate herniation is often the precursor to other type of herniation

Acute: causes severe craniocerebral injury

Chronic:  causes progressive neurological deficit

3 Territories:

1. supplied by the PCA: Includes occipital lobe and inferior temporal lobes

2. Middle cerebral artery: supplies the superior temporal lobes, as well as the lateral portions of the frontal and parietal lobes

3. Anterior cerebral artery:  supplies the superior/medial portions of the frontal lobe and parietal lobe