Retrospective Analysis of EEG in Patients With COVID-19: EEG Recording in Acute and Follow-up Phases

Abstract

Background. Interest in electroencephalographic (EEG) coronavirus disease 2019 (COVID-19) findings has been growing, especially in the search for a specific-features EEG of encephalopathy. Methods. We made a retrospective analysis of 29 EEGs recorded in 15 patients with COVID-19 and neurological symptoms. We classified the EEGs as “Acute EEG” and “follow-up EEG.” We did a statistical analysis between voltage and respiratory status of the patient, stay or not in the intensive care unit (ICU), days of stay in the ICU, sedative drugs, pharmacological treatment, type of symptoms predominating, and outcome. Results. We found EEG abnormalities in all patients studied. We observed the amplitude of background <20 µV at 93% of “acute EEG,” versus only 21.4% of “follow-up EEG.” The average voltage went from 12.33 ± 5.09 µV in the acute EEGs to 32.8 ± 20.13 µV in the follow-up EEGs. A total of 60% of acute EEGs showed an intermittent focal rhythmic. We have not found a statistically significant association between voltage of acute EEG and nonneurological clinical status (including respiratory) that may interfere with the EEG findings. Conclusions. Nonspecific diffuse slowing EEG pattern in COVID-19 is the most common finding reported, but we found in addition to that, as a distinctive finding, low voltage EEG, that could explain the low prevalence of epileptic activity published in these patients. A metabolic/hypoxic mechanism seems unlikely on the basis of our EEG findings. This pattern in other etiologies is reminiscent of severe encephalopathy states associated with poor prognosis. However, an unreactive low voltage pattern in COVID-19 patients is not necessarily related to poor prognosis.

The value of EEG attenuation in the prediction of outcome in COVID-19 patients

“…Higher prevalence of attenuated patterns was reported in two more recent studies, reaching 21-25% of cases [16,19]. The association between generalized attenuation and higher mortality was postulated but not confirmed [16]. In patients who performed more than one EEG, we observed that the attenuation pattern found in the latter EEG was more likely to predict unfavourable outcome.…”

“…Diffuse attenuation has also been reported in other case series, but almost always in small percentages [2,7,18] or presumably none [13,14]. Higher prevalence of attenuated patterns was reported in two more recent studies, reaching 21-25% of cases [16,19]. The association between generalized attenuation and higher mortality was postulated but not confirmed [16].…”

“…All case series report low percentages of patients with asymmetrical EEG patterns, focal slowing, or lateralized epileptiform activity. Diffuse voltage attenuation has been considered an infrequent pattern, with only one recent study emphasizing this condition [16]. We hypothesize that in COVID-19 patients a stereotyped EEG diffuse attenuated unreactive pattern is more frequent than previously considered.…”

SARS-CoV-2 alters neural synchronies in the brain with more severe effects in younger individuals

“…According to a systematic review and meta-analysis, the proportion of abnormal EEG in C19 subjects is as high as 96% 16 . Non-specific, generalized background or diffuse slowing has been reported in several studies as the most common finding 10 , 11 , 18 , whereby EEG abnormalities correlate with encephalopathy, disease severity 8 , 9 , 17 , and risk for novel seizures 13 , including psychogenic non-epileptic seizures 5 . In particular, delta waves with absence of epileptic activity have been documented 12 , as well as alpha coma patterns suggestive of SARS-CoV-2 neurotropism for the brainstem ascending reticular system 15 .…”

EEG background frequency is associated with discharge outcomes in non-ICU hospitalized patients with COVID-19

“…A retrospective chart review of 42 SARS-CoV2-infected patients found 9 (21.4%) had EEGs with an encephalopathy pattern, defined as continuous or rhythmic frontal or diffuse slow diphasic or triphasic waves or sharp waves ( 14 ). In a study by Saez-Landete et al, common EEG characteristics of nonspecific diffuse slowing and low voltage EEG were identified on acute and follow-up EEGs on 15 SARS-CoV2 infected patients ( 15 ). Although there have been several studies characterizing encephalopathy and related conditions, there are still gaps in the literature predominantly due to the heterogeneity of small studies whose methods vary widely.…”