This case series retrospectively reviews the clinical, neuroimaging, EEG, and laboratory features of seropositive autoimmune encephalitis (SAE) patients with isolated seizures presentation (ISP).

Patients with ISP refractory to anti-epileptic medications often experience delayed diagnosis of SAE and delayed immunotherapy initiation. Few studies explore the diverse antibodies associated with ISP.

A retrospective multicenter study was conducted across two tertiary referral centers, reviewing  217 consecutive autoimmune encephalitis cases from January 2002 to April, 2024. Of the 217 patients, 135 patients had confirmed SAE. SAE patients with concurrent psychosis, catatonia, movement disorders, focal neurologic deficits, and memory deficits were excluded resulting in 10 patients in this case series.

Ten patients presented with ISP with a median age of 46 years. Of these patients, 40% were female, 50% Caucasian, and 40% African American. Anti-NMDA receptor antibody encephalitis was the most common antibody (40%), followed by anti-LGI1 (30%), anti-GAD65 (20%), dual anti-VGKC/anti-LGI1 (10%), and one case of Hashimoto’s encephalopathy. Known malignancy was present in 20% of patients. Imaging revealed temporal lobe involvement in 70% of cases, while all patients had abnormal EEG findings. Of the eight patients who underwent a lumbar puncture, four patients demonstrated inflammatory CSF. Acute immunotherapy included IV steroids, IVIG, and plasma exchange therapy (PLEX). 40% later received Rituximab, and one was treated with Cytoxan. Status epilepticus occurred in 50% of the patients, with 20% experiencing refractory status until immunotherapy was added. A Charlson comorbidity score of ≥2 was observed in 30% of patients. No deaths were reported, and 40% of patients achieved a good recovery with a Glasgow Outcome Score of 5.

ISP as a presentation of SAE is rare. This case series highlights the diverse antibodies and clinical presentations associated with ISP. The absence of mortality underscores the importance of early diagnosis and prompt intervention with immunotherapy.