Encephalitis

1-Causes: Viruses.

2-Predisposing factors:Immunosuppresive state of the patient such as in cases of AIDS, cancer and organ transplant in addition to chronic illness as diabetes, renal failure and old age.

3-Effects:It affects meninges, brain parenchyma and ventricles.

Meninges=Meningitis.

Parenchyma=Encephalitis which could be acute, sub acute, chronic and acute demyelnating encephalomyelitis.

Ventricles=Ventriculitis.

Any organism reaches the brain will cause these three effects, remember that well.

 

4- Radiological appearance is non specific.

CT: Multiple area of hypo density.

 MRI: Low signal intensity in T1 and high signal intensity in T2.

           Could enhanced (gyral form), but usually do not enhance. 

D.D. from infarction

Could be differentiated by

-Clinical history as in patient with infarction the patient is hemiplegic while in encephalitis is suffering from fever, neck regidity and semi conscious.

-Encephalitis could be bilateral and symmetrical while in case of infarction is not.

-Infarction shows cortical distribution with specific vascular territory while encephalitis does not have.

-Encephalitis has a predisposing factor while infarction does not has.