Megakaryocytes in Brain Vessels May Cause Neurologic Impairment in COVID-19

Illustration of antibodies (y-shaped) responding to a coronavirus infection. Different strains of coronavirus are responsible for diseases such as the common cold, gastroenteritis and SARS (severe acute respiratory syndrome). The new coronavirus SARS-CoV-2 (previously 2019-CoV) emerged in Wuhan, China, in December 2019. The virus causes a mild respiratory illness (Covid-19) that can develop into pneumonia and be fatal in some cases. The coronaviruses take their name from their crown (corona) of surface proteins, which are used to attach and penetrate their host cells. Once inside the cells, the particles use the cells’ machinery to make more copies of the virus. Antibodies bind to specific antigens, for instance viral proteins, marking them for destruction by phagocyte immune cells.
A team of researchers investigated histopathology of patients with COVID-19 to provide insight into the disease’s impact on cognition and other neurologic symptoms.

Megakaryocytes in cortical capillaries of patients with coronavirus disease (COVID)-19 may cause distinct ischemic alterations and lead to various neurologic manifestations, according to study results published as a research letter in JAMA Neurology.

Many patients with COVID-19 may experience neurologic impairment during the acute illness and after recovery from the acute infection. These manifestations may include confusion, altered state of consciousness, and brain fog. The objective of this study was to assess histopathological changes that may underlie these neurologic disturbances.

Study researchers assessed brain tissues from autopsies of patients with COVID-19 at Johns Hopkins University and Mass General Brigham to identify histopathological changes in this population. Additionally, they included 2 patients without COVID-19 with hypoxic-ischemic changes.

Findings indicated megakaryocyte presence in cortical capillaries in 5 patients with COVID-19. These cells were not seen in the cortex of both COVID-19-negative cases that had hypoxic brain changes.

Several studies have previously shown that endothelial dysfunction may play an important role in severe COVID-19 illness. Examinations reported megakaryocyte presence in several other organs, including the lung, in patients with COVID-19, but this is the first report on megakaryocytes in brain vessels.

The study researchers suggested that in patients with COVID-19, megakaryocytes are recruited into the circulation and pass through the lungs. In the current study, they observed these megakaryocytes in cortical capillaries in 33% of examined cases.

“We report here a finding that may contribute in some cases, identified by analysis of brain tissue from patients who died of COVID-19,” wrote the study researchers. They added, “By occluding flow through individual capillaries, these large cells [megakaryocytes] could cause ischemic alteration in a distinct pattern, potentially resulting in an atypical form of neurologic impairment.”


Nauen DW, Hooper JE, Stewart CM, Solomon IH. Assessing brain capillaries in coronavirus disease 2019. JAMA Neurol. Published online, February 12, 2021. doi:10.1001/jamaneurol.2021.0225