Increased Intracranial Pressure and Herniation Occur With Space-Occupying Lesions

Question 1

What does the Monro-Kellie hypothesis state?

Answer 1

Intracranial volume = Volume_CNS + Volume_CSF + Volume_Blood + Volume_Lesion

Question 2

What is the normal ICP?

Answer 2

< 200 mm H₂O or 15 mmHg

Question 3

What compensates when a lesion takes up space in the cranium?

Answer 3

CSF volume is reduced

Question 4

What happens if a lesion occupies more space than the CSF can compensate for?

Answer 4

The blood volume is reduced

Question 5

If the lesion expands and CSF volume and blood volume changes cannot compensate for these changes, what occurs?

Answer 5

The brain will give on itself and potentially herniate.

Question 6

What occurs when one hemisphere of the brain is pushed under the falx cerebri? Syx? What artery may become displaced? What Syx would follow?

Answer 6

Subfalcine (Cingulate Herniation); Confusion and Drowsiness; Anterior Cerebral Artery (ACA); Contralateral lower extremity weakness and urinary incontinence

Question 7

What herniation likely occurs when a hemisphere is forced from the supratentorial compartment toward the infratentorial compartment? What nerve is crushed? What does this cause?

Answer 7

Uncal herniation; CNIII; Ipsilateral pupillary dilatation and paresis of all extraocular muscles except the lateral rectus (CN VI) and superior oblique (CN IV) resulting in lateral looking eye

Question 8

Describe the Kernohan notch. What are the signs?

Answer 8

Crushing of a cerebral pedicle resulting in hemiparesis on the same side as the offending mass. The ipsilateral signs clinically are confusing and are called “false localizing” sign.

Question 9

A lesion causes a cerebral hemisphere herniation downward and medial. The herniation occludes one of the posterior cerebral arteries. What clinical sign will be present? Why is this a “false localizing” sign?

Answer 9

The patient may lose sight. One therefore would expect the lesion to be in the occipital lobe, but the lesion is actually in the superior part of the brain.

Question 10

Both cerebral hemispheres herniate transtentorially. What is the name of this syndrome? What are the Syx? What is a typical post-mortem finding?

Answer 10

Central Herniation Syndrome; Bilateral pupil dilation, flaccidity and coma; Duret hemorrhages

Question 11

The cerebellum becomes forced downward through the foramen mangnum. What likely becomes compressed?

Answer 11

The cerebellar tonsils and medulla

Question 12

What is fungus cerebri?

Answer 12

The brain oozes out of an opening in the skull

Question 13

What are the three types of cerebral edema?

Answer 13

Cytotoxic, Vasogenic, Interstitial

Question 14

What is cytotoxic edema?

Answer 14

Osmotic forces drive H2O across the BBB

Question 15

What is the most common form of cerebral edema? What causes it?

Answer 15

Vasogenic; BBB loosens permitting uncontrolled fluid to enter brain.

Question 16

What causes interstitial cerebral edema?

Answer 16

Overproduction/failure of egress of CSF

Question 17

What are the two causes of hydrocephalus?

Answer 17

Overproduction or failure of egress of CSF

Question 18

What is noncommunicating hydrocephalus? What is another name for noncommunicating hydrocephalus? What is the most common cause?

Answer 18

Blockage of CSF flow causing dilation of ventricles proximal to blockage; Obstructive; Blockage of Aqueduct of Sylvius betwixt 3rd and 4th ventricle

Question 19

What is communicating hydrocephalus? What ventricles dilate?

Answer 19

Blockage of CSF flow after it has left the ventricular system. All ventricles dilate.

Question 20

What are clinical signs that an infant/child have hydrocephalus?

Answer 20

The head can enlarge to grotesque proportions

Question 21

What are general clinical signs of hydrocephalus?

Answer 21

Confusion, drowsiness, pailledema and vomiting

Question 22

What are clinical signs of hydrocephalus in an older person?

Answer 22

Dementia, gait impairment, urinary incontinece (Wacky, wobbly, wet)

Question 23

What is normal pressure hydrocephalus?

Answer 23

Intracranial pressure is not increased, but there is an abnormal accumulation of CSF leading to ventrculomegaly.