Causes of intra cranial infection

1-Causes:

-Congenital.

-Bacterial---cerebritis.

-Viral---causing encephalitis.

-Fungal.

-T.B---causing granulomatous infection.

-Parasitic.

-AIDS.

2-Results of brain infection:

Brain infection affects the following

-Meninges causing meningitis, epi dural and sub dural empyema .

-Brain parenchyma---encephalitis, cerebritis or brain abscess.

-Ventricles---causing ventriculitis.

3-Radiological appearance of this results:

-Effect of contrast injection---causes enhancement which means that the contrast will goes to the lesion appearing in CT as increased density while in MRI as marginal enhancement.

In case of meningitis, it causes--- Meningeal enhancement.

In case of sub dural or epi dural infection--- Marginal enhancement.

In case of brain abscess--- Marginal enhancement.

In case of ventriculitis--- Marginal enhancement.

4-Important rule:

-To assess the intra cranial infection you must use contrast injection.

-This rule should be applied during the examination using CT or MRI even if you know that the lesion will not take contrast, as this result by itself is a diagnosis for the case.

-So injection of contrast is a basic in case of diagnosis of brain infection.

-If you find the meninges thickened or not but enhanced--- this means meningitis.

-If you find the lesion is marginally enhanced, look to the site of the lesion, if it is in the area of meninges, so it will be epi dural or sub dural empyema, but if the lesion is in the parenchyma, it will be brain abscess, and if the lesion is in the ventricles, it will be ventriculitis.

-If the lesion is not enhanced, it will be hydatid cyst if it is in the brain parenchyma, but if it is in the CSF spaces it could be arachnoid or epidermoid cyst.