In order to quantitatively evaluate the electroencephalography (EEG) findings in patients (18 years old and older) with coronavirus disease 2019 (COVID-19), a systematical review of the sources and meta-analysis were performed. Publications with descriptive EEG in patients diagnosed with COVID-19 were systematically searched in PubMed databases until May 31, 2022. In analysis of the EEG data, American Clinical Neurophysiology Society’s terminology was used. Confidence intervals (CIs) for the general sample were computed using the Wilson score CI method, adjusting for continuity. The I 2 statistic was used to measure heterogeneity of studies. Of 295 identified publications, there were selected 121 studies from 19 countries throughout the world. EEG data of 1916 patients (age from 18 to 97 years old; mean age 60 years old) were included in the meta-analysis. Normal EEG was recorded in 7.52 % (95 % CІ: 6.39–8.83). Abnormal background activity (86.90 % (95 % CІ: 85.31–88.34), I 2 = 41.23 %), first of all generalized slowing (75.22 % (95 % CІ: 73.23–77.11)), was the most prevalent finding. Generalized periodic and rhythmic EEG patterns were more prevailed than lateralized ones (31.05 % vs. 7.90 %). Epileptiform discharges were registered in 23.06 % (95 % CІ: 21.19–25.05) of patients, along with this status epilepticus (both anamnestic and de novo) had 9.49 % (95 % CІ: 8.19–10.98), I 2 = 58.82 %, including nonconvulsive status epilepticus in 3.59 % (95 % CІ: 2.81–4.58), I 2 = 33.35 %. Non-specificity of the EEG findings in COVID-19 supports a multimodality of pathophysiological mechanisms of their origin.

Further researches of EEG-abnormalities in COVID-19 in dynamics are necessary, whereas now the prevalence of these abnormalities is useful from the point of view of adequacy of a diagnostic minimum rather than risk prognosis for each patient.