Seizures in autoimmune encephalitis: Findings from an EEG pooled analysis

Seizure. 2020 Dec:83:160-168. doi: 10.1016/j.seizure.2020.10.019. Epub 2020 Oct 31.

Abstract

Purpose: Seizures are common in autoimmune encephalitis (AE), and an extensive work-up is required to exclude alternative etiologies. The aim of our study was to identify possible clinical/EEG peculiarities suggesting the immune-mediated origin of late-onset seizures.

Methods: Thirty patients diagnosed with AE (19 men, median age 68 years, 18 seronegative) were included. Overall 212 video-electroencephalographic (EEG) and 31 24-h ambulatory EEG (AEEG) recordings were retrospectively reviewed. Posterior dominant rhythm, interictal epileptiform discharges (IEDs), clinical (CSs) and subclinical seizures (SCSs) were analyzed.

Results: Six-hundred-nineteen ictal events were recorded in 19/30 subjects, mostly (568/619) during AE acute stage. Among ten patients with CSs other than faciobrachial dystonic seizures, 7 showed prominent autonomic and emotional manifestations. SCSs were detected in 11 subjects, mainly via AEEG (260/287 SCSs vs 150/332 CSs, p < 0.001). Eight patients presented seizures during hyperventilation. IEDs, documented in 21 cases, were bilateral in 14 and focal temporal in 13. Multiple ictal EEG patterns were detected in 9/19 patients, 6 of whom had both CSs and SCSs, bilateral asynchronous seizures and ictal activities arising from temporal and extra-temporal regions. No correlation was found between the lateralization of MRI alterations and that of EEG findings.

Conclusion: Our study confirms that adult-onset, high frequency focal seizures with prominent autonomic and emotional manifestations should be investigated for AE. Multiple ictal EEG patterns could represent a 'red flag', reflecting a widespread neuronal excitability related to the underlying immune-mediated process. Finally, our work enhances the crucial role of long-lasting EEG monitoring in revealing subclinical and relapsing seizures.

Keywords: 24-h ambulatory EEG; Amygdala; Autoimmune encephalitis; Late-onset epilepsy; Subclinical seizures; Transient epileptic amnesia.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Autoimmune Diseases / physiopathology*
  • Brain / immunology
  • Brain / physiopathology*
  • Electroencephalography* / adverse effects
  • Encephalitis / diagnosis
  • Encephalitis / immunology
  • Encephalitis / physiopathology*
  • Epilepsies, Partial / complications
  • Epilepsies, Partial / immunology
  • Epilepsies, Partial / physiopathology
  • Female
  • Hashimoto Disease / diagnosis
  • Hashimoto Disease / immunology
  • Hashimoto Disease / physiopathology*
  • Humans
  • Magnetic Resonance Imaging / methods
  • Male
  • Middle Aged
  • Retrospective Studies
  • Seizures / diagnosis
  • Seizures / immunology
  • Seizures / physiopathology*

Supplementary concepts

  • Hashimoto's encephalitis