COVID-19 Long Haulers

A detailed study from Stanford University of tissue from the brains of people who died of COVID-19 looks a lot like what’s observed in the brains of people who die of Alzheimer’s or Parkinson’s disease. This helps explain why many COVID-19 patients report neurological problems. The symptoms can persist as an aspect of “long-haulers”, a disorder that sometimes arises following infection with COVID-19. About one third of people hospitalized with COVID report symptoms of fuzzy thinking, forgetfulness, difficulty concentrating and depression.

Yet despite this occurrence, they can’t find any of the COVID virus present in the brain tissue. One reason is the blood-brain barrier which is selective as to which molecules can get into the brain. But now, work by Wyss-Corays group shows blood born factors that are outside the brain can signal through the blood-brain barrier to ignite inflammatory responses inside the brain. These findings may help explain COVID long-haulers symptoms of brain fog, fatigue and other symptoms.

Potentially, discovering how this works could lead to treatments for dementia that occurs due to aging. But getting the samples of brain tissue from deceased COVID patients is hard, since neuropathologists are reluctant to take the steps to excise it because of potential exposure.

In the samples they received, there were signs of distress in the neurons that play a key role in decision-making and memory.  The molecular
changes in the outermost layers of the brain tissue suggest suppressed signaling of these neurons. This inhibition of neurons acts like putting the brakes on. This kind of signaling imbalance has been associated with conditions such as Alzheimer’s. 

In addition, they found that T cells, immune cells that prowl for pathogens, were more abundant in the brain tissue from COVID-19 patients. In healthy brains, these immune cells are few and far between.

Viral infection appears to trigger inflammatory responses throughout the body, and may cause inflammation across the blood-brain barrier.

More studies can be done by analyzing COVID patients cerebrospinal fluid, whose contents mirror those of the living brain and are easier to extract.