Thesis title: ELECTRO-CLINICAL CHARACTERIZATION OF AUTOIMMUNE ENCEPHALITIS
Purpose: Seizures are common in autoimmune encephalitis (AE), and an extensive work-up is required to exclude alternative etiologies, especially in elderly subjects. Given the dearth of data on “autoimmune seizures”, the aim of this study was to investigate 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 213 video-electroencephalographic (EEG) and 31 24-h ambulatory EEG (AEEG) recordings were retrospectively reviewed. Posterior dominant rhythm, interictal epileptiform discharges (IED), 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 (FBDS), 7 showed prominent autonomic manifestations, associated with emotional symptoms in 4 cases. SCSs were detected in 11 subjects (36.6%), mainly via AEEG (260/287 SCSs vs 150/332 CSs, p<0.001) and during sleep (216/287). Eight patients presented seizures during hyperventilation (HV), although FBDS appeared more sensitive to HV (HV-related seizures: 10/66 FBDS+ vs 12/192 other CSs vs 3/72 SCSs, p=0.042). IED, documented in 21 cases, were bilateral in 14 and focal temporal in 13, and tended to increase during sleep. 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: This 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, this work enhances the crucial role of long-lasting EEG monitoring in revealing subclinical and relapsing seizures.