COVID-19 and the brain

Headache, body pains or myalgias, and encephalopathy (confusion, drowsiness, altered brain function) are common signs of neurologic or brain involvement in patients with symptomatic Covid-19.
Dizziness, loss of smell (anosmia), dysgeusia (altered taste) stroke, seizures, and movement disorders are other manifestations.
The SARS-CoV-2 virus can affect the brain by directly invading neurons (brain cells) or nerves and blood vessels. Its effects may also be mediated through systemic inflammatory response to the infection.
Marked increase in blood levels of inflammatory markers like D-dimer and ferritin and cytokines are associated with confusion and altered consciousness. Hypoxemia or low levels of oxygen in the blood arising as a complication of the viral infection affects brain function and causes damage to brain tissue.
In one study, autopsy of 18 cases of severe Covid-19 patients who had encephalopathy before they died revealed acute ischemic changes.
The virus attaches to ACE2 receptors, proteins on the surfaces of cells, to enter cells. This can bring about dysfunction of the renin-angiotensin system (RAS) which is involved in blood vessel functions, blood pressure control, and other functions. RAS dysfunction leads to brain complications.
Anosmia and dysgeusia that can occur in the absence of nasal discharge or nasal congestion and reported as common early symptoms of Covid-19 occur because the SARS-CoV-2 invades the olfactory nerve, the structure in the brain responsible for the sense of smell. In one study, the mean duration of loss of smell was eight days.
Delirium may be an early or presenting sign in a Covid-19 case. In most patients, it develops during the course of illness.
Diagnostic procedures aside from the basic blood tests include magnetic resonance imaging, electroencephalogram, and examination of the cerebrospinal fluid (attained though insertion of a needle in the patient’s back).
Substantial improvement may occur but poor outcome and prolonged confinement are associated with the presence of altered brain status. Poorer outcomes are also seen in patients with associated diseases like elevated blood pressure, elevated blood sugar, and other underlying diseases.