Electroencephalographic findings post-COVID-19 vaccination: A systematic review of case reports and case series.

A number of different neurological complications have been reported following vaccination against the coronavirus disease 2019 (COVID-19). Electroencephalogram (EEG) is one of the modalities used to evaluate the neurological complications of diseases. The aim of the present study was to identify the EEG changes in participants vaccinated against COVID-19. PubMed, Scopus, Web of Science, medRxiv, and Google Scholar were searched up to 1 September 2022, with terms related to COVID-19 vaccines, EEG, neurological signs/symptoms, or neurological disorders. All case reports and case series were included if the participants had received at least one dose of a COVID-19 vaccine and a post vaccination EEG report was also reported. We used the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for case reports and case series to appraise the methodological quality of the included studies. Thirty-one studies were included, which were comprised of 24 case reports and seven case series and a total of 36 participants. Generalised slowing and non-convulsive focal status epilepticus were the most common EEG findings post-COVID-19 vaccination. The most frequent symptoms were headache, fatigue, generalised weakness, and vomiting. In addition, the most common signs were encephalopathy, post-ictal phases, and confusion. Encephalitis, acute disseminated encephalomyelitis, and post-vaccinal encephalopathy were the most commonly diagnosed adverse events. Furthermore, most of the imaging studies appeared normal. The EEG reports mainly showed background slowing and epileptiform discharges, encephalitis, encephalopathies, and demyelinating disorders. Future studies with larger samples and more vaccine types may help to further unravel the potential neurological effects of COVID-19 vaccinations on recipients.