3. Volume and Edema

Question 1

Monro-Kellie Hypothesis

Answer 1

Head is a closed shell

The three major components:

1. Brain
2. Blood - arterial and venous
3. CSF

are in the state of dynamic equillibrium.

As the volume of one goes up, the volume of another goes down

Question 2

Intfacranial Hypotension

Answer 2

Leaking CSF = decrease overall fixed volume = venous blood increases = maintain equillibrium =

Meningeal engorgement (enhancement
Distention of the dural venous sinus
Prominence of the intracranial vessels
Engorgement of the pituitary (Pituitary pseudomass)

Subdural hematoma and hygroma develop

Question 3

Idiopathic Intracranial Hypertension (Pseudotumor Cerebri

Answer 3

Too much CSF, or not absorbing it correclty

increased CSF =
Slit like ventricles
Shrinked pituitary (partially empty sella)
Compressed venous sinus

Downward displacement ofthe brainstem = streteched CN6 (Abducens) = 6th nerve paresis

Question 4

Blood, pus, or cancer plugs up the villie (SAH, Meningitis (TB or bacterial, and Carcinomatous Meningitis) = obstructioin between basal cistern and arachnoic granulation = All ventricles are big + CSF can exit all the ventrilces

Answer 4

Communicating hydrocephalus + True obstruction

Question 5

Brain Atrophy (ex-vacuo) + Normal Pressure hydrocephalus + Choroid Plexus Papilloma (CSF secreting tumor) = obstructioin between basal cistern and arachnoic granulation = All ventricles are big + CSF can exit all the ventrilces

Answer 5

Communicating hydrocephalus without Obstruction

Question 6

Big upstream ventrices + Obstruction with the ventricle system + CSF cannot exit ventricles =

Answer 6

Non-communicating hydrocephalus

Question 7

Level of obstruction in Non-communicating hydrocephalus

Answer 7

Foramen of Monro = colloid cyst

Aqueduct = Aqueduct stenosism tectal Glioma

4th ventricle = posterior fossa tumor
Cerebellar edema/bleed

Question 8

Answer 8

Arachnoid Cysts

They are CSF density, without any solid components, or abnormal restricted diffusion

Question 9

This type of edema can be thought about as intracellular swelling secondary to
malfunction o f the Na/K pump

Answer 9

Cytotoxic Edema

Question 10

Imaging features of Cytotoxic Edema

Answer 10

Loss of gray-white matter differentiation seen in stroke (Early signs)

Question 11

Cytotoxic vs Vasogenic Edema

Answer 11

Question 12

Midline shift (deviation of
ipsilateral ventricle and bowing of the falx)

Answer 12

Subfalcine Herniation

Question 13

What is compressed in Subfalcine herniation?

Answer 13

Anterior cerebral artery (ACA) maay be compressed = infarct

Question 14

The uncus and hippocampus herniate through the tentorial incisura. Effacement of the ipsilateral suprasellar cistern occurs first

Answer 14

Descending Transtantorial herniation

Question 15

What are compressed in Descending Transtatorial herniation?

Answer 15

Perforating basilar aryery

CN3 - between the PCA an dSuperior cerebellar artery - dialatation of pulils and ptosis

Kernohan’s notch/phenomenon -

Question 16

Think about this in the setting of a posterior fossa mass. The vermis will herniate upward through the tentorial incisura, often resulting in severe obstructive hydrocephalus

Answer 16

Ascending transtentorial henriation

Question 17

Ascending transtentorial henriation imaging features:

Answer 17

Fattened smile - quadrigeminal cistern

“SPINNING TOP” midbrain from bilateral compression along its posteiror aspect

Question 18

Cerebellar Tonsil Herniation

Answer 18

From Severe herniataion after DOWNWARD transtentorial henriation

if in isolation you are
thinking more along the lines of
Chiari (Chiari I = 1 tonsil - 5 mm).