30-80% of COVID-19 patients experience neurological symptoms, such as headaches, dizziness, loss of concentration and nausea, which may last beyond the disease recovery period. As the long-term complications of COVID-19 are not clear yet, research into the development of these neurological symptoms is essential. Two recent studies have highlighted crucial findings on the link between COVID-19 and the brain.
Abnormal and slow electrical discharge
The first study, from researchers at the University of Pittsburgh and Baylor College of Medicine, have analysed 80 studies to look for similarities and differences in brain electrical activity. The studies used electroencephalogram (EEG) technology to look at this activity.
The researchers found that one third of patients given an EEG showed abnormal neuroimaging primarily in the frontal lobe of the brain. The most frequent findings from the EEG measurements were abnormal or slow electrical discharge. These alterations may represent damage in the brain that may be irreparable after recovering from COVID-19.
The researchers also found that, from those affected, 61 was the average age, and two-thirds were male. Therefore, COVID-19 brain involvement may be more frequent in older males. The researchers also pointed out that, as the coronavirus is likely to enter through the nose, it appears as though the brain damage is occurring at the virus’ entry point.
However, it is important to note that it may not always be the virus directly affecting the brain. The abnormal EEG recordings could also be due to COVID-19 related complications, such as oxygen intake, heart problems or other side-effects.
‘Leaky’ blood-brain barrier
The second study, from researchers at Temple University, looked at the effect of SARS-CoV-2 (the virus that causes COVID-19) on the blood-brain barrier. The blood-brain barrier is a border of cells that protects against circulating toxins or pathogens that could cause brain infections. It acts as a filter, whilst still allowing vital nutrients to reach the brain.
The researchers found that proteins from SARS-CoV-2 promote inflammatory responses on cells forming the blood-brain barrier, causing the barrier to become ‘leaky’. This could disrupt the crucial and delicate neural networks of the brain. Proteins on SARS-CoV-2 do this by converting enzyme 2 (ACE2), which are found on cells forming the lining of blood vessels. The researchers looked at post-mortem brains and found that ACE2 is found in blood-vessels in the frontal cortex.
When the blood-brain barrier is altered, neuroinvasions can occur, which may be the cause of neurological manifestations experienced by COVID-19 patients.
The authors of both of these studies emphasised the fact that the long-term consequences of COVID-19 on the brain are unknown. However, once the effect of COVID-19 on the brain becomes clear, treatments for long-term issues could begin to be developed.
Study 1: Arun Raj Antony, Zulfi Haneef. “Systematic review of EEG findings in 617 patients diagnosed with COVID-19”. Seizure, 2020. Accessible at: https://www.seizure-journal.com/article/S1059-1311(20)30332-0/fulltext
Study 2: Tetyana P. Buzhdygan, Brandon J. DeOre, Abigail Baldwin-Leclair, Trent A. Bullock, Hannah M. McGary, Jana A. Khan, Roshanak Razmpour, Jonathan F. Hale, Peter A. Galie, Raghava Potula, Allison M. Andrews, Servio H. Ramirez. “The SARS-CoV-2 spike protein alters barrier function in 2D static and 3D microfluidic in-vitro models of the human blood–brain barrier”. Neurobiology of Disease, 2020; 146: 105131. Accessible at: https://www.sciencedirect.com/science/article/pii/S096999612030406X?via%3Dihub
Featured photo: Pesce N. L. “55% of coronavirus patients still have neurological problems three months later: study”. Market Watch, The Margin, 2020.