Histology and Explanation of Purulent Meningitis

Purulent leptomeningitis (suppurative leptomeningitis) is a diffuse purulent inflammation. The leptomeninges (arachnoida and piamater) contain purulent exudate (pus): leukocytes (neutrophils), fibrin, germs, proteins, necrotic debris. Blood vessels in the subarachnoidian space and those intracerebral are congested and neutrophil margination is present. (Hematoxylin-eosine, ob. x4)

Microscopically, a neutrophilic exudate is seen involving the meninges at the left, with prominent dilated vessels. There is edema and focal inflammation (extending down via the Virchow-Robin space) in the cortex to the right. This acute meningitis is typical for bacterial infection.

This 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.