RESUMO
Post-acute COVID-19 syndrome (PCS) is highly prevalent. Critically ill patients requiring intensive care unit (ICU) admission are at a higher risk of developing PCS. The mechanisms underlying PCS are still under investigation and may involve microvascular damage in the brain. Cerebral misery perfusion, characterized by reduced cerebral blood flow (CBF) and elevated oxygen extraction fraction (OEF) in affected brain areas, has been demonstrated in cerebrovascular diseases such as carotid occlusion and stroke. This pilot study aimed to examine whether COVID-19 ICU survivors exhibited regional misery perfusion, indicating cerebral microvascular damage. In total, 7 COVID-19 ICU survivors (4 female, 20-77 years old) and 19 age- and sex-matched healthy controls (12 female, 22-77 years old) were studied. The average interval between ICU admission and the MRI scan was 118.6 ± 30.3 days. The regional OEF was measured using a recently developed technique, accelerated T2-relaxation-under-phase-contrast MRI, while the regional CBF was assessed using pseudo-continuous arterial spin labeling. COVID-19 ICU survivors exhibited elevated OEF (ß = 5.21 ± 2.48%, p = 0.047) and reduced relative CBF (ß = -0.083 ± 0.025, p = 0.003) in the frontal lobe compared to healthy controls. In conclusion, misery perfusion was observed in the frontal lobe of COVID-19 ICU survivors, suggesting microvascular damage in this critical brain area for high-level cognitive functions that are known to manifest deficits in PCS. Physiological biomarkers such as OEF and CBF may provide new tools to improve the understanding and treatment of PCS.
RESUMO
Objectives: Coronavirus disease 2019 (COVID-19) results in severe inflammation at the acute stage. Chronic neuroinflammation and abnormal immunological response have been suggested to be the contributors to neuro-long-COVID, but direct evidence has been scarce. This study aims to determine the integrity of the blood-brain barrier (BBB) in COVID-19 intensive care unit (ICU) survivors using a novel MRI technique. Methods: COVID-19 ICU survivors (n=7) and age and sex-matched control participants (n=17) were recruited from June 2021 to March 2023. None of the control participants were hospitalized due to COVID-19 infection. The COVID-19 ICU survivors were studied at 98.6 ± 14.9 days after their discharge from ICU. A non-invasive MRI technique was used to assess the BBB permeability to water molecules, in terms of permeability surface area-product (PS) in the units of mL/100â¯g/min. Results: PS was significantly higher in COVID-19 ICU survivors (p=0.038) when compared to the controls, with values of 153.1 ± 20.9 mL/100â¯g/min and 132.5 ± 20.7 mL/100â¯g/min, respectively. In contrast, there were no significant differences in whole-brain cerebral blood flow (p=0.649) or brain volume (p=0.471) between the groups. Conclusions: There is preliminary evidence of a chronic BBB breakdown in COVID-19 survivors who had a severe acute infection, suggesting a plausible contributor to neurological long-COVID symptoms.
