Post-Infectious Cerebellitis: A Systematic Review of Aetiology, Clinical Presentation, Treatment, and Outcomes.

Post-infectious cerebellitis is an immune-mediated cerebellar inflammatory syndrome that follows a preceding infection (or, rarely, vaccination) after a latent interval. It spans a spectrum from benign post-infectious/acute cerebellar ataxia (ACA) through more severe acute cerebellitis (AC) with leptomeningeal enhancement and mass effect, to rare, life-threatening acute fulminant cerebellitis (AFC) with hydrocephalus risk. Evidence is largely limited to individual case reports and small case series, and no prior review has systematically pooled patient-level data across etiologies. A PRISMA-guided systematic review screened 899 records identified through electronic database searches, citation tracking, and supplementary bibliography searches. After duplicate removal and eligibility assessment, 47 studies (case reports, case series, and cohort studies) were included in the qualitative synthesis. Patient-level data from 73 individuals were extracted for quantitative pooling. Pooled patients had a mean age of 24.5 years (range 7 months-74 years; 40 pediatric, 28 adult); of 70 patients with sex reported, 51 (72.9%) were male. Based on neuroimaging findings and the presence of life-threatening features, 34 patients (46.6%) were classified as acute cerebellar ataxia (ACA), 26 (35.6%) as acute cerebellitis (AC), and 13 (17.8%) as acute fulminant cerebellitis (AFC), with complete recovery in 58.8%, 69.2%, and 69.2% of each subtype, respectively, and the cohort's only death occurring in the AFC subgroup. SARS-CoV-2 (n = 24, 32.9%) was the most frequently identified trigger, followed by patients with no pathogen identified (n = 18, 24.7%), varicella-zoster virus (n = 8, 11.0%), Epstein-Barr virus (n = 5, 6.8%), and influenza (n = 5, 6.8%). Corticosteroids were the most common treatment (54/73, 74.0%), followed by antivirals (35/73, 47.9%) and IVIG (19/73, 26.0%); plasma exchange was given for refractory cases. Complete recovery occurred in 47/73 patients (64.4%), partial recovery/residual deficit in 15/73 (20.5%), outcome was not stated for 10/73 (13.7%), and one death (1.4%) was recorded (COVID-19-associated necrotizing encephalopathy) - the only fatality, occurring in an adult. Post-infectious cerebellitis is a heterogeneous, largely immune-mediated syndrome with a generally favorable prognosis after corticosteroid-based immunotherapy, though outcomes and evidence quality vary by etiology and severity subgroup.