Clinical characteristics, treatment, and outcomes in anti-metabotropic glutamate receptor-1 encephalitis: A systematic review.

[OBJECTIVES] To characterize the clinical manifestations, paraclinical findings, treatment, and outcomes in 42 cases of anti-metabotropic glutamatergic receptor-1 (mGluR1) encephalitis.

[METHODS] We conducted a systematic review of 42 reported cases of anti-mGluR1 encephalitis in accordance with the PRISMA statement. Clinical data were systematically extracted from published literature in PubMed, Web of Science, Embase, and Cochrane databases spanning January 2000 to August 2025. Statistical analysis was conducted on demographic characteristics, clinical presentations, paraclinical findings, treatment regimens, and clinical outcomes.

[RESULTS] Twenty-two articles with 42 cases were included. The median age at onset was 50.5 years (range: 3-81 years) with equal gender distribution. Prodromal symptoms were present in 26.2 % of cases. Cerebellar manifestations developed in nearly all cases (n = 41, 97.6 %) during the disease course. Lymphoma represented the most frequently associated malignancy. Magnetic resonance imaging (MRI) abnormalities were detected in 50.0 % of patients and inflammatory cerebrospinal fluid findings were frequently observed. Glucocorticoids constituted the most common immunotherapy (n = 29, 80.6 %). The majority of patients showed clinical improvement (n = 31), and a few of patients (n = 5) experienced disease relapses.

[CONCLUSIONS] Anti-mGluR1 encephalitis represents a rare yet treatable autoimmune disorder, characterized by predominant cerebellar involvement, typically of non-paraneoplastic origin. Initial comprehensive neoplastic screening appears sufficient for most cases. Immunotherapy yields favorable responses in most patients, with generally good long-term outcomes.