New research shows that the spike protein, often depicted as the red arms of the virus, can cross the blood-brain barrier in mice. The spike proteins alone can cause brain fog. Since the spike protein enters the brain, the virus also is likely to cross into the brain.
More and more evidence is coming out that people with COVID-19 are suffering from cognitive effects, such as brain fog and fatigue.
The spike protein often called the S1 protein, dictates which cells the virus can enter. Usually, the virus does the same thing as its binding protein. Binding proteins like S1 usually by themselves cause damage as they detach from the virus and cause inflammation.
This intense inflammation caused by the COVID-19 infection is called a cytokine storm. The immune system, upon seeing the virus and its proteins, overreacts in its attempt to kill the invading virus. The infected person is left with brain fog, fatigue and other cognitive issues.
Source: University of Washington Health Sciences/UW Medicine