Practical Neurology | 2021
Amoebic encephalitis mimicking acute disseminated encephalomyelitis
Abstract
© Author(s) (or their employer(s)) 2021. No commercial reuse. See rights and permissions. Published by BMJ. A 16yearold Japanese girl presented with left hemiparesis and coma, following a 2day history of headache and fever. She had been previously well and no history of a skin wound. MR scan of the brain showed a 6 cm lesion in the right frontal white matter with mass effect and slight edge enhancement (figure 1). A craniotomy was performed for external decompression and brain biopsy. The intraoperative finding was of white matter necrosis rather than tumour or abscess. An interim biopsy showed prominent neutrophil infiltration and fibrinoid necrosis in small vessels but no evidence of a specific pathogen. We suspected either a central nervous system infection or an autoimmune disease such as acute disseminated encephalomyelitis, and so started antibiotics and pulsed corticosteroids in the intensive care unit. On day 2, she had mydriasis with a defective pupillary light reflex. Repeat MR scan of brain showed multiple T2 highintensity lesions with marked oedema involving the brainstem, bilateral basal ganglia, cerebellum, corpus callosum and white matter (figure 1). We diagnosed acute haemorrhagic leukoencephalitis (WestonHurst syndrome) based on the rapidly worsening clinical situation and imaging and started enhanced immunotherapy. We continued the pulsed corticosteroid therapy, then plasma exchange followed by intravenous immunoglobulin. However, her condition and imaging findings remained unchanged. The brain biopsy histopathology in our institute had suggested infection but with no traceable organism. We therefore asked the National Institute of Infectious Diseases to examine the brain biopsy