Among the many serious symptoms of COVID-19, the strange neurological effects that many patients experience are considered to be the most unexplored.
The sudden loss of smell and taste was one of the first unusual symptoms reported by patients with COVID-19, but cases of stroke, seizures, and cerebral edema (called encephalitis) have been documented.
Some patients diagnosed with COVID-19 also experience confusion, delirium, dizziness, and difficulty concentrating, according to reports and research.
For several months, doctors have tirelessly tried to understand this disease and its many manifestations that affect the brain.
To summarize some of the rapidly accumulating data, two neurologists reviewed studies examining how COVID-19 disrupts patterns of normal brain function that can be measured with EEG.
EEG, short for electroencephalogram, records electrical activity in various parts of a person's brain, usually using electrodes placed on the scalp.
In their review, the researchers collated data on nearly 620 COVID-infected patients from 84 studies published in peer-reviewed journals and on pre-press servers where EEG waveform data was available for analysis.
Analysis of EEG results may indicate some form of encephalopathy associated with COVID, in these patients – signs of deterioration or impairment of brain function.
About two-thirds of the patients in the studies were male, and the median age was 61 years.
Among 420 patients in whom the basis for EEG was recorded, the most common cause was a change in mental state: about two-thirds of the patients examined experienced delirium, coma, or confusion.
About 30% of patients experienced a seizure-like seizure that prompted their doctor to order an EEG, while a few patients had speech problems. Others have had sudden cardiac arrest, which could interfere with blood flow to the brain.
EEG scans of the patients showed a spectrum of abnormalities in brain activity, including some rhythmic patterns and epileptic bursts of activity. The most common abnormality noted was diffuse slowing, that is, a general slowing down of brain waves indicative of general dysfunction of brain activity.
In the case of COVID, this disorder could be the result of widespread inflammation as the body strengthens its immune response, or possibly decreased blood flow to the brain if the heart and lungs are weak.
In terms of localized effects, a third of all abnormalities found were found in the frontal lobe, the part of the brain that performs executive thinking tasks such as reasoning and decision making. The frontal lobe also helps us regulate our emotions, control our behavior, and is involved in learning and attention.
“These data tell us that we need to try EEGs in a wider range of patients, as well as other types of brain imaging, such as MRI or CT, that will allow us to take a closer look at the frontal lobe,” said neurologist and study co-author Zulfi Hanif. from Baylor College of Medicine in Houston.
Over time, an EEG can help confirm a diagnosis of COVID-19 or hint at possible complications. This could help doctors track long-term complications of COVID-19 and detect any long-term effects on a patient's brain function.
Unfortunately, the results do not currently provide any indication of how rare or common these brain wave disturbances are in the wider population, as only COVID-19 patients who had an EEG test were included in the analysis.
But it adds more and more evidence that the new coronavirus could seriously impact our neurological health.
“More research is needed, but these results show us that these are the areas to focus on as we move forward,” Hanif said.
“EEG abnormalities affecting the frontal lobe appear to be common in COVID-19 encephalopathy and have been suggested as a potential biomarker with ongoing recording,” the authors write in their paper.
The study was published in Seizure: European Journal of Epilepsy.
