Amoebic Disease of CNS

Naegleria fowleri: is a free living opportunistic protozoon, ubiquitous in nature that may cause an infection known as amoebic meningoencephalitis (PAM)

Note: Differential diagnosis with rare invasion of the brain by the intestinal amoeba Entamoeba histolytica.

Acquired by exposure to polluted bodies of water (ponds, swimming pools and man-made lakes); raised temperatures during hot summer months or warm water from power plants facilitates the growth.

The amoeba enters the nasal mucosa  penetrates the cribriform plate of the ethmoid bone  pierces olfactory epithelium to the olfactory bulb of the brain  causing haemorrhage and meningitis / fulminant meningoencephalitis.

Macroscopically: an acute haemorrhagic necrotising meningoencephalitis with modest purulent exudate; mainly at the base of the brain, brain stem & cerebellum.

Microscopically: trophozoites can be seen within the CNS lesions mainly around blood vessels.

Balmuthia and Species of Acanthamoebia: are also free-living opportunistic protozoa that are ubiquitous in nature; may cause granulomatous amoebic encephalitis (GAE)…

The portal of entry is through the respiratory tract or an ulceration of the skin reaching the CNS by haematogenous spread.

It produces patchy chronic or sub-acute granulomatous encephalitis with the presence of trophozoites and cysts.

GAE occurs in the debilitated, malnourished, individuals undergoing immunosuppressive therapy for organ transplants and in AIDS.

Consequences include headache, altered mental states, and focal neurological deficit, which may progress over several weeks-months to death

Category: Medicine Notes , Pathology Notes