[A Case of Suspected Nonparaneoplastic Autoimmune Panencephalitis with Widespread Multifocal Brain Lesions and Treatable Dementia Following Pernicious Anemia: A Seven Year Follow-Up Study].

We present a case of a 73-year-old female who developed subacute memory disturbance, reduced consciousness and quadriparesis following pernicious anemia. Brain magnetic resonance imagings (MRI) in diffusion weighted, T2 weighted and fluid attenuated inversion recovery (FLAIR) images revealed hyperintensities in bilateral frontal, parietal, temporal and occipital cortices, left thalamus, bilateral splenium of corpus callosum, and bilateral subcortical white matters. Brain gadolinium enhanced T weighted MRI revealed very slight post-contrast enhancement lesions in the right posterior temporal region and bilateral parietal regions. Serum was negative for anti- aquaporin (AQP) 4 antibody, anti-glutamic acid decarboxylase (GAD) antibody and anti-voltage-gated potassium channel (VGKC) antibody, and cerebrospinal fluid (CSF) was negative for anti- N-methyl-D-aspartate (NMDA) receptor antibody. CSF analysis showed slight protein elevation with normal cellular content. No evidence of neoplasm was observed using whole-body 18 F -fluorodeoxyglucose- positron emission tomography/computed tomography. Pathological findings of the left frontal lesion revealed perivascular and scattered parechymal T-lymphocytic infiltration, and astrogliosis without vascular hyalinization. Patient achieved partial recovery during two intraveneous pulse methylprednisolone treatments, and exacerbation afterwards. After the third intraveneous pulse methylprednisolone treatment, remission is sustained for six years. This case can be regarded as autoantibody-negative but probable autoimmune encephalitis with the features of nonparaneoplastic panencephalitis and treatable dementia. Nonparaneoplastic autoimmune panencephalitis with widespread multifocal brain lesions on brain MRI is extremely rare, with exception of anti- NMDA receptor antibody encephalitis.