Practical

A thick layer of yellow purulent suppurative exudate covers the brain stem and cerebellum, and thickens the leptomeninges
Pyogenic meningitis


The yellow-tan clouding of the meninges seen here is due to an exudate from acute bacterial meningitis; it obscures the sulci.
Acute bacterial meningitis


Clouding of the meninges seen here is due to an yellow purulent exudate from acute bacterial meningitis; it obscures the sulci. The cerebrospinal fluid (CSF) in such cases typically has a low glucose, high protein, and many PMN's. A gram stain should be done to identify organisms.
Acute bacterial meningitis


A neutrophilic exudate is seen involving the meninges above, with prominent dilated vessels. There is edema and focal inflammation (extending down via the Virchow-Robin space) in the cortex below. This acute meningitis is typical for bacterial infection. The edema can lead to herniation and death. Resolution of infection may be followed by adhesive arachnoiditis with obliteration of subarachnoid space leading to obstructive hydrocephalus.
Acute bacterial meningitis

Viral Meningitis CSF

Polymorphic population of lymphocytes

Abscesses in the frontal white matter (arrows): discrete lesions with central liquefactive necrosis and a surrounding zone of hyperemia
Brain abscess

There is a liquefactive center with yellow pus surrounded by a thin wall*.

Cerebral abscess

Brain abscess

Brain abscess that is sharply demarcated, indicating that it has been present for some time. Purulent exudate is visible in the center of the abscess.


The lesion's purulent contents (Rt.) are separated from neighboring white matter by a granulation tissue-like zone of angioblastic and fibroblastic activity.
Brain abscess

There is marked necrosis of the right temporal lobe, and petechial haemorrhages and early necrosis in the left temporal lobe. This distribution is characteristic of herpes simplex encephalitis.
Herpes encephalitis


Characteristic findings of viral meningitis include perivascular cuffs of lymphocytes (A) and microglial nodules (B).
Viral infections
A
B

Note the microglial nodule and multinucleated giant cell (arrow).

HIV encephalitis


In this prion disease there is spongiform change in the cerebral cortex. Inset, High magnification of neuron with vacuoles
Creutzfeldt-Jakob disease (CJD)