COVID-19 and the brain: What do we know so far?

How does SARS-CoV-2, the virus that causes COVID-19, affect the human brain? Recent studies have given us clues, shedding light on why COVID-19 can be so severe for some people and why the symptoms can last a long time.

There is a long history of similar viruses affecting the brain, researchers have pointed out, so many expect the new coronavirus to have this effect.

For example, Dr. Gabriel A. de Erausquin, a professor of neurology at The University of Texas Health Science Center at San Antonio, notes that “Since the flu pandemic of 1917 and 1918, many of the flu-like diseases have been associated with brain disorders.”

“Those respiratory viruses included H1N1 and SARS-CoV. The SARS-CoV-2 virus, which causes COVID-19, is also known to impact the brain and nervous system,” adds the researcher. The question is — how, and to what extent?

Effect on the brain explains loss of smell

Dr. de Erausquin recently published a paper along with colleagues, including senior author Dr. Sudha Seshadri, a professor of neurology at the same institution and director of the university’s Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases.

“The basic idea of our study is that some of the respiratory viruses have affinity for nervous system cells,” Prof. Seshadri explains. She adds, “Olfactory cells are very susceptible to viral invasion and are particularly targeted by SARS-CoV-2, and that’s why one of the prominent symptoms of COVID-19 is loss of smell.”

Olfactory cells are concentrated in the nose. Through them, the virus reaches the olfactory bulbin the brain, which is located near the hippocampus, a brain area involved in short-term memory.

“The trail of the virus, when it invades the brain, leads almost straight to the hippocampus,” explains Dr. de Erausquin. “That is believed to be one of the sources of the cognitive impairment observed in COVID-19 patients. We suspect it may also be part of the reason why there will be an accelerated cognitive decline over time in susceptible individuals.”