Epileptic phenotypes in autoimmune encephalitis: from acute symptomatic seizures to autoimmune-associated epilepsy

Objective To describe the clinical and paraclinical findings, treatment options and long-term outcomes in autoimmune encephalitis (AE), with a close look to epilepsy. Methods In this retrospective observational cohort study, we enrolled patients with new-onset seizures in the context of AE. We compared clinical and paraclinical findings in patients with and without evidence of antibodies. Results Overall, 263 patients (138 females; median age 55 years, range 4-86) were followed up for a median time of 30 months (range 12-120). Antineuronal antibodies were detected in 63.50%. Antibody-positive patients had multiple seizure types (p=0.01) and prevalent involvement of temporal regions (p=0.02). A higher prevalence of episodes of SE was found in the antibody-negative group (p<0.001). Immunotherapy was prescribed in 88.60%, and effective in 61.80%. Independent predictors of favourable outcome of the AE were early immunotherapy (p<0.001) and the detection of antineuronal surface antibodies (p=0.01). Autoimmune-associated epilepsy was the long-term sequela in 43.73%, associated with cognitive and psychiatric disturbances in 81.73%. Independent predictors of developing epilepsy were difficult to treat seizures at onset (p=0.04), a high number of antiseizure medications (p<0.001), persisting interictal epileptiform discharges at follow-up (p<0.001) and poor response to immunotherapy during the acute phase (p<0.001). Conclusions The recognition of seizures secondary to AE represents a rare chance for aetiology-driven seizures management. Early recognition and treatment at the pathogenic level may reduce the risk of long-term irreversible sequelae. However, the severity of seizures at onset is the major risk factor for the development of chronic epilepsy. This study provides class IV evidence for management recommendations.

Automated summary

This study describes the clinical and paraclinical findings, treatment options, and long-term outcomes in autoimmune encephalitis (AE), with a focus on the relationship with epilepsy. The study found that early immunotherapy and detection of antineuronal surface antibodies were independent predictors of favorable outcomes in AE. Autoimmune-associated epilepsy was a common long-term sequelae, often accompanied by cognitive and psychiatric disturbances. The severity of seizures at onset was the major risk factor for the development of chronic epilepsy.