Nervous System- Infection & Inflammation I
Question No. 7. The Answer is: (B) 1 and 3 are true.
1. Can present as subacute or chronic encephalitis.
3. Can present as space occupying lesions.
Discussion: Granulomatous amebic encephalitis can be caused by the Acanthamoeba species of ameba and Balamuthia mandrillars. In contrast to Naegleria fowleri, they are not associated with a history of swimming in fresh water ponds. In addition, granulomatous amebic encephalitis can take a prolonged but eventually fatal course. The route of entry is incompletely understood. Acanthamoeba species is neurotropic for the brain. They can present as subacute to chronic meningitis and meningoencephalitis. They can also present as space occupying lesions that mimic a tumor. Any location of the brain can be involved but the spinal cord is typically spared. On histology sections, Acanthamoeba species are 15-45 mm in diameter and have a clear nucleus with a dense central nucleolus, coarsely granular and vacuolated cytoplasm. Cysts (15-20 mm) formation with the characteristic double membrane can be identified and this feature allows separation from Naegleria fowleri. The infection causes a subacute or chronic meningitis and meningoencephalitis features by pervascular accumulation of plasma cells, macrophages, and lymphocytes. Thombosis and giant cell formation can also be found. Identification of the microorganisms within the inflammatory cell infiltration is not straight forward. A high index of suspicion is necessary in order to make the diagnosis. Acanthamoeba species of amoeba and Balamuthia mandrillars and morphologically very similar and can only be distinguished by specific antibodies. Prognosis is grave.
[Click here to see a case that presents as a space occupying lesion] [Click here to see a case with protracted course]