COVID-19 May Damage Blood Vessels in the Brain

A new study suggests that the virus might actually damage the brain's small blood vessels rather than nerve cells themselves.

A postmortem analysis found abnormalities in the brains of a small sample of patients with COVID-19, suggesting inflammation and vascular damage to the brain stem and olfactory bulb. The findings add further weight to previous research into neurological complications from COVID-19.

The research was published online Jan. 12 in the New England Journal of Medicine. Myoung Hwa Lee, PhD, was the lead author.

The study included high resolution magnetic resonance imaging and histopathological examination of 13 individuals with a median age of 50 years. Among 10 patients with brain alterations, the researchers conducted further studies in 5 individuals using multiplex fluorescence imaging and chromogenic immunostaining in all 10.

The team conducted conventional histopathology on the brains of 18 individuals. Fourteen had a history of chronic illness, including diabetes, and hypertension, and 11 had died unexpectedly or been found dead. Magnetic resonance microscopy revealed punctuate hypo-intensities in nine subjects, indicating microvascular injury and fibrinogen leakage. Histopathology using fluorescence imaging showed the same features. Collagen IV immunostaining showed thinning of the basal lamina of the endothelial cells in five patients. Ten patients had congested blood vessels and surrounding fibrinogen leakage, but comparatively intact vasculature. The researchers interpreted linear hypo-intensities as micro-hemorrhages.

The researchers found little perivascular inflammation, and no vascular occlusion. Thirteen subjects had perivascular-activated microglia, macrophage infiltrates, and hypertrophic astrocytes. Eight had CD3+ and CD8+ T cells in the perivascular spaces and in lumens next to endothelial cells, which could help explain vascular injury.

The researchers also obtained a convenience sample of subjects who had died from COVID-19. Magnetic resonance microscopy, histopathology, and immunohistochemical analysis of sections revealed microvascular injury in the brain and olfactory bulb, despite no evidence of viral infection.