Brain atrophy in autoimmune encephalitis: epidemiology, pathophysiology, clinical manifestations, treatment, and prognosis-an update.

PURPOSE

Autoimmune encephalitis (AE) refers to a group of rare autoimmune diseases affecting the central nervous system. New research shows that it can trigger neurodegenerative changes, especially brain atrophy. This atrophy has multiple causes, which worsen the prognosis. Thus, future studies need to focus on the early identification of AE patients at risk of brain atrophy and early interventions to prevent this complication. This review covers epidemiology, risk factors, clinical symptoms, pathophysiological mechanisms, and immunosuppressive therapy and summarizes current progress in understanding AE-related brain atrophy.

LATEST FINDINGS

AE patients with brain atrophy often have anti-N-Methyl-D-Aspartate Receptor (NMDAR), anti-Leucine-Rich Glioma-Inactivated 1 (LGI1), anti-glutamic acid decarboxylase 65 kDa Isoform (GAD65) antibodies, and other antibodies in serum and cerebrospinal fluid; however, seronegative patients may also have atrophy. The temporal lobe, cerebellum, and brainstem most often show reduced volume, causing ataxia, memory decline, and cognitive and motor impairments. The risk factors include patient age, antibody types, and early cognitive impairments as non-modifiable factors. Timely treatment, the duration of status epilepticus, cumulative disease burden, nutritional status, and concomitant medications are modifiable risk factors. The mechanisms of AE-related brain atrophy include metabolic disturbances and immune-mediated pathology. Glucocorticoids and intravenous immunoglobulin (IVIG) may reduce atrophy but do not restore brain volume. Some novel treatments are under investigation; however, no current clinical trials specifically target brain atrophy. Previous research has facilitated the understanding of the clinical presentation, mechanisms, and treatment of brain atrophy. Some studies suggest that children with AE can also experience brain atrophy, and subsequent follow-ups revealed brain dysplasia. However, the data primarily originate from studies with small-sized adult samples, and studies concerning children are lacking. Large-sample, multi-age stratified cohort studies are needed to explore early identification using neuroimaging biomarkers, new mechanisms, and novel therapeutic approaches to improve patient prognosis.

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