Clinical information was retrospectively obtained from medical records, together with data from previously published pediatric patients.

We identified 115 patients, of which 84 (71 adults, 13 children) had AMPAR antibodies alone and 31 (27 adults, 4 children) had additional neuronal antibodies. Considering patients with AMPAR antibodies alone, tumors were only identified in adults (37/71 (52%) vs 0/13 (0%), p<0.0001). Compared to adults, children were more likely to show behavioral/psychiatric symptoms at onset (5/13, 39% vs 8/71, 11%, p=0.026), cerebellar dysfunction (6/13, 46% vs 7/68, 10% p= 0.005) or movement disorders (5/13, 39% vs 8/67, 12%, p=0.032) during the disease course, and extratemporal brain MRI abnormalities (4/9, 44% vs. 5/44, 11%, p=0.035).

A follow-up >24 months was available from 34 alive patients (30 adults, 4 children): 23 (68%), all adults, had neurological sequelae and 11 had full recovery. At multivariate analysis, failure to respond to first-line immunotherapy was the only predictor of bad outcome (i.e. modified Rankin scale [mRS]>2 (OR 8.8, 95%CI 1.3–59.5, p=0.025). Among the 31 patients with additional neuronal autoantibodies, 22 (79%) had an associated tumor; those with high-risk antibodies had higher mortality (p= 0.009).

Children with anti-AMPAR encephalitis have different clinical-radiological features compared to adults. Neurological sequelae are frequent in adults, and failure to respond to first-line immunotherapy predicts worse outcome. Additional high-risk antibodies are associated with higher mortality.