Seizure underreporting in LGI1 and CASPR2 antibody encephalitis

Area of Science:

• Neurology
• Immunology
• Epileptology

Background:

• Anti-leucine-rich glioma-inactivated 1 protein (LGI1) and anti-contactin-associated protein 2 (CASPR2) antibody encephalitis often present with frequent epileptic seizures.
• Seizures in these conditions typically respond well to immunosuppressive therapy, suggesting favorable long-term outcomes.
• Previous studies relied on patient reports, potentially leading to underreporting of persistent seizures.

Purpose of the Study:

• To investigate the long-term seizure outcomes in patients with LGI1 and CASPR2 antibody encephalitis.
• To evaluate the accuracy of reported seizure freedom using objective video-electroencephalography (EEG) data.
• To determine if the proportion of patients with persistent seizures is higher than previously estimated.

Main Methods:

• Retrospective screening of clinical records from a tertiary epilepsy center.
• Inclusion of patients with LGI1 or CASPR2 antibody encephalitis reporting seizure freedom for at least 3 months.
• Inclusion of patients who underwent prolonged video-EEG monitoring (>24 hours) during follow-up.

Main Results:

• 32 patients with LGI1 (n=24) and CASPR2 (n=8) antibody encephalitis were identified.
• 20 patients (15 LGI1, 5 CASPR2) met the criteria for seizure freedom and prolonged EEG.
• Four patients (20%) experienced focal aware or impaired awareness seizures during follow-up, with seizure-free intervals ranging from 3 to 27 months.

Conclusions:

• The favorable long-term seizure outcome in LGI1 and CASPR2 antibody encephalitis is questioned.
• A significant proportion of patients may experience persistent seizures, challenging the notion of acute symptomatic seizures.
• Prolonged video-EEG telemetry is essential for accurate assessment of seizure outcomes in these patients.