Amebic encephalitis

BACKGROUND: Amebic encephalitis (granulomatous amebic encephalitis, GAE) an extremely rare disease occurring in immunocompromised patients. Presentation and early imaging findings are nonspecific. In GAE, enhancement may or may not be seen on imaging studies despite the presence of an aggressive, necrotizing, parasitic infection. CASE DESCRIPTION: The patient was a 79-year-old man with ill-defined autoimmune hepatitis. He was on mild immunosuppression with 6-MP and low-dose prednisone. He presented with an acute febrile illness and obtundation. Imaging revealed a nonenhancing mass lesion of the frontal lobe. The patient briefly improved on high-dose steroids, then deteriorated again, with repeat imaging showing enlargement of the edematous brain lesion and herniation. The patient underwent craniotomy for evacuation of a necrotic brain lesion. His condition did not improve. Frozen section revealed only necrosis. Permanent pathology revealed GAE caused by Acanthamoeba. CONCLUSION: Neurosurgeons should remain aware of this rare disease. Imaging is variable and may not show enhancement or necrosis despite large areas of parasitic infection.