Autoimmune and paraneoplastic encephalitis-associated neuronal autoantibodies with serial EEG in adults with unexplained new-onset seizures or worsening epilepsy.

objectiveUnexplained seizures or worsening epilepsy in adult patients may be associated with specific neuronal or onconeuronal antibodies. We propose that comprehensive antibody testing is beneficial for adults with new-onset seizures or aggravated epilepsy without a predetermined etiology. Additionally, a combination of serial electroencephalography (EEG) may enhance clinical management.

methodsAdult patients with new-onset seizures or worsening of existing epilepsy of an unknown cause who were admitted for comprehensive evaluation and management (including cerebrospinal fluid study, brain MRI, and EEG) were retrospectively and consecutively enrolled. Clinical and laboratory data were also collected. Antibody prevalence in epilepsy score (APE) and antibody prevalence in epilepsy and encephalopathy score (APE2) were calculated. Serial EEG results were quantified on a 5-point scale using the EEG criteria of the American Clinical Neurophysiology Society (ACNS).

resultsBetween 2017 and 2022, a total of 46 patients were enrolled. Three of 15 patients (20.0%) from the outpatient clinic tested positive for specific antibodies, an indistinguishably high rate compared with 9 of 31 patients (29.0%) from the emergency room (ER) (p = 0.72). Receiver operating characteristic (ROC) analysis using the APE score to predict antibody positivity showed an area under the curve of 0.690. The optimal cutoff point was 6, with an overall accuracy of 73.9%, sensitivity of 41.7%, and specificity of 85.3%. Notably, a faster decrease in the 5-scale EEG severity scores, indicative of better EEG improvement, was associated with the application of immunotherapy and a high response to immunotherapy in epilepsy (RITE) score. SIGNIFICANCE: Our study supports prompt and thorough immunological workup for patients with new-onset or worsening epilepsy without a clear etiology. Immune etiology in these patients had a 26.1% yield rate. Moreover, serial EEGs play a pivotal role in monitoring the effectiveness of immunotherapy, in addition to being a diagnostic aid. PLAIN LANGUAGE SUMMARY: This study investigated adults who experienced seizures for which routine medical examinations could not identify the cause. We discovered that approximately 26% of these patients, whether they were acute cases in the emergency department or chronic cases in the outpatient department, had specific antibodies that might trigger their condition. Furthermore, using serial EEGs, we could effectively monitor treatment progression. Our results emphasize the importance of comprehensive antibody testing and brainwave monitoring for the management and understanding of previously unexplained seizures.