Mass Effect

1-The mass effect is the effect of the presence of a mass in the brain parenchyma.

-This effect is as follows:

Effacement of cortical sulci.

Compression of the epsilateral ventricle.

Shift of the mid line structures.

Dilatation of the contra lateral ventricle.

As you see in this example there is sub dural hematoma causing mass effect on the right brain lobe resulting in effacement of the epsilateral cortical sulci, compression of the epsilateral lateral ventricle, shift of the mid line structures and dilatation of the contra lateral lateral ventricle.

2-So we have three degrees of mass effect

-First degree shows effacement of cortical sulci.

-Second degree shows compression of the epsilateral ventricle without shift to opposite side.

-Third degree shows compression of the epsilateral ventricle with shift of this ventricle to the opposite side.

3-The mass effect depend mainly upon two factors

-The size of the lesion which directly proportional with the mass effect.

-And the degree of perifocal edema surrounding the lesion which is also has a direct proportional with mass effect.

-This means that as the size of the lesion is increased and or the perifocal edema surrounding it is increased in size as the mass effect is increased.

4-There are two types of peri focal edema

-The first one is cytotoxic edema which is present as a rim of edema around acute infarction and hemorrhage.

-The second one is vasogenic edema which appears as finger like edema (like a tree) surrounding the lesion and it is seen around space occupying lesion such as( tumors, abscesses,...).

5-Here you can differentiate between a tumor shows hemorrhage and a hemorrhage primarily present without a tumor.

In case of hemorrhage caused by a tumor the peri focal edema present will be vasogenic due to the existing tumor, while in case of a primary hemorrhage without the presence of a tumor the type of peri focal edema will be cytotoxic type.

Example of a vasogenic edema surrounding a space occupying lesion

Example of a cytotoxic edema in case of infarction