ICP

NO prod.

Vagal activity

Venous resistance

Ventricle size

Clinical comments

Raised ICP

↑

↑

normal

↓

↑

Venous resistance decreases according to Monro-Kellie doctrine

Low ICP

↓

↓

normal

↑

↓

e.g. iatrogen

SAH

↑↑

↑↑

normal

↑↑

↓

Sympathetic overflow overwrites the vagus-ICP system

Obliterated CSAS

AG: no ICP registr.

none

normal

↓

↑

No information reaches the vagus, venous resistance is low

Slit ventricles

↓↓

↓↓

normal

↑↑

↓↓

Due to overdrainage

PC

↑↑

?

disturbed information

↑↑

↓↓

Pseudotumor cerebri breaks the rule, probably disturbed/wrong message to vagus

NPH

↑

↑

normal

↓

↑

Disturbed absorption, not frank hydrocephalus. Gradual change in ventricle size