Spontaneously resolving seronegative autoimmune limbic encephalitis.

OBJECTIVE We describe a patient with seronegative autoimmune limbic encephalitis (SNALE) masquerading as glioma. Brain magnetic resonance imaging (MRI) abnormalities, distinctive pathological findings, and spontaneous remission are highlighted. BACKGROUND There are 15 previously reported SNALE cases, 1 with pathology. MATERIALS AND METHODS A 66-year-old man presented with prominent amnestic syndrome, progressive cognitive decline, and refractory complex partial seizures. RESULTS Initial brain MRI suggested herpes limbic encephalitis. A 3-week course of intravenous acyclovir was ineffective. Cerebrospinal fluid analysis revealed no pleocytosis. Repeat brain MRI showed a left uncal-hippocampal, contrast-enhancing lesion with mass effect, which was resected. Pathology revealed perivascular and parenchymal mixed lymphocytic inflammatory infiltrates, microglial nodules, neuronophagia, microglial activation, astrocytosis, and lymphocyte emperipolesis within neurons. Thorough searches for infectious pathogens and autoantibodies were negative. Six weeks later, a new enhancing right mesial temporal lesion appeared, with increased seizure activity and further cognitive impairment. Although immune therapy was declined, spontaneous resolution of the new enhancing lesion, with full seizure control and significant cognitive improvement, occurred. CONCLUSIONS SNALE may masquerade as glioma. Pathologic changes in our case of SNALE are distinctive. Spontaneous resolution of a focal SNALE lesion may potentially occur without immune therapy.