Covid-19 doesn’t seem to act like most other viruses. Since the pandemic began, an increasing number of strange neurological symptoms have appeared in Covid-19 patients alongside the typical flu-like symptoms, and doctors are striving to understand exactly what the virus does to the brain.
In a systematic review study published in the Seizure: European Journal of Epilepsy, researchers compiled 84 Covid-19 studies that contained electroencephalograms (EEG) to get a better understanding of the ways in which the brain changes as a result of virus infection. They found one-third of patients given an EEG showed abnormal imaging in the frontal lobe of the brain.
An electroencephalogram is a test that detects the usual rhythmic patterns and activity of the brain, in this case, whether they change during and after infection. Scientists are aware that Covid-19 is correlated with abnormal EEGs readings, but there is a lack of both understanding and consistency of these findings. Neurological abnormalities can have serious and lasting effects, and understanding them is paramount to effective Covid-19 treatment.
“As we know, the brain is an organ that cannot regenerate, so if you have any damage it will more than likely be permanent or you will not fully recover,” co-author Dr Zulfi Haneef said in a statement.
The review spanned 617 patients with a median age of 61 years old. Following analysis of each case and their reported symptoms, the researchers collated the most common reasons for ordering an EEG and then any EEG abnormalities that followed infection. The most common reason for requesting an EEG was an altered mental status of the patient, with 62 percent experiencing some form of confusion, delirium, or coma. This was closely followed by seizure-like events, including speech issues (31 percent). The least common reason was cardiac arrest, which only accounted for a small number of patients (3.5 percent).
Within the large cohort of patients, a number of similar abnormalities emerged. Of the 617 people tested, 543 (88 percent) had abnormal EEG recordings. The most dominant of the abnormalities was "diffuse slowing," a reading commonly seen in psychiatric patients that is correlated with general cognitive impairments in areas such as attention and memory. Nearly 69 percent of the entire cohort tested showed diffuse slowing within their EEG results. This could be related to inflammation as the body mounts an immune response, or if blood flow to the brain is reduced because the heart or lungs are weakened
Beyond this, approximately one-third of all patients exhibited changes within their frontal lobe, the area of the brain responsible for voluntary movement, high-level cognitive function, and language, whilst also controlling how we regulate emotion.
“We know that the most likely entry point for the virus is the nose, so there seems to be a connection between the part of the brain that is located directly next to that entry point,” Haneef said. “Another interesting observation was that the average age of those affected was 61, one-third were female and two-thirds were males. This suggests that brain involvement in Covid-19 could be more common in older males. More research is needed but these findings show us these are areas to focus on as we move forward.”
With such a significant portion of patients experiencing EEG abnormalities, it is extremely likely a large portion of the cases are directly related to Covid-19 infection. It is noted, however, that some of these cases may also be due to the high average age of the cohort. Furthermore, some patients also had pre-existing neurological conditions that may affect EEG results, and the researchers note this as a possible reason for the extremely high abnormality rate.
As a result of the findings, the researchers are now calling for hospitals to perform EEGs on a wider array of Covid patients to elucidate whether this is a phenomenon exclusive to hospitalized patients or if people with low-level symptoms are also affected.