Hydrocephalus

HYDROCEPHALUS
1-Definition: Enlarged ventricular system due increased Intraventricular pressure.
2-MRI signs:
-Transependymal CSF permeation.
-Upward bowing and thinning of the corpus callosum
-Dilatation of ventricles.
3-Hydrocephalic types
-Obstructive: Obstruction proximal to foramina of Luschka and Magendie(lower image).
-Communicating: Obstruction is distal to fourth ventricle foramina(upper image).
-Normal pressure hydrocephalus
*Is a subset of communicating hydrocephalus?
*Hyper flow of CSF.
*Occurs in elderly.
*Ventricles dilated out of proportional to the enlarged cortical sulci.
*Key finding on MRI is marked loss of signal in aqueduct and adjacent third and fourth ventricles. In addition to the extent of this flow void starting from foramen of Monroe down to the fourth ventricle.
4-Causes of obstructive hydrocephalus

A) At the level of aqueduct of sylvious
*Tectal tumors
*Pineal region tumors
*Aqueductal Stenosis.

B)At the level of foramen of Monrow

*Colloid cyst

*Giant cell astrocytoma
5-Compensation process: Occurs when a tumor close e.g. foramen of Monroe causing CSF permeation, than after that the lateral ventricles start to dilate resulting in decreasing Intraventricular pressure and interstitial edema start to resorb, this is called compensation process.
Presence of interstitial edema indicates presence of increased Intraventricular pressure and resorption of this fluid indicates normalized pressure even if ventricles still dilated.
Presence of interstitial edema=elevated ventricular pressure