Journal Article

Diffusion tensor imaging after COVID-19 infection: A systematic review

Saint, Sidney A., Stoessl, A. Jon, Field, Thalia S., Wellington, Cheryl, Song, Catie, Sossi, Vesna, Farah, Lea N., Silverberg, Noah D., Panenka, William J., Nelson, Breanna K., Lang, Donna, Honer, William G.

2025

Overview

•Diffusion MRI has been used to compare COVID-19 patients with healthy controls.•COVID-19 patients tend to have widespread lower anisotropy than healthy controls.•More severe COVID-19 illness is associated with more dMRI differences.•Systemic inflammation is a possible mechanism for dMRI changes after COVID-19. Most COVID-19 neuroimaging research focuses on clinically evident lesions occurring during the acute period after infection. Chronic effects on brain structure, especially at a microstructural level, are less well defined. Existing advanced neuroimaging studies report inconsistent differences in white matter integrity after COVID-19 infection. Our aim was to systematically evaluate the advanced neuroimaging literature with a specific focus on examining diffusion MRI (dMRI) abnormalities observable after the resolution of the acute phase of COVID-19 illness. A search of the literature was conducted on PubMed, Embase, and Scopus on May 27th, 2023, and an updated search was performed September 20th, 2024. Inclusion criteria were a quantitative comparison of dMRI metrics between COVID-19 patients and non-COVID-19 volunteers with MRI acquired >6 weeks after COVID-19. Studies that included only subgroups of COVID-19 patients with specific symptoms, case reports, and post-mortem studies were excluded. Forwards and backwards citation chasing were performed. The initial search identified 1709 unique records, and 11 met inclusion criteria. Most studies included hospitalized COVID-19 patients, with brain MRI acquired between 2 and 6 months after COVID-19 infection. The majority of studies reported lower fractional anisotropy and higher mean diffusivity in the post-COVID-19 cohort, compared to non-COVID-19 controls. However, there were inconsistent findings, with one study reporting higher fractional anisotropy after COVID-19 infection. Cohorts with a more severe acute COVID-19 illness tended to have lower fractional anisotropy and higher mean diffusivity than cohorts with a milder illness course. Compared to shorter follow-up periods, a longer time between COVID-19 and MRI was associated with fewer differences between COVID-19 patients and non-COVID-19 volunteers. A review of the literature indicates that the heterogeneity of findings regarding dMRI metrics after the resolution of the acute phase of COVID-19 illness may be due in part to the severity of COVID-19 illness and the time between COVID-19 and MRI. Future studies should also consider how different SARS-CoV-2 variants differentially affect the structural brain differences after COVID-19.

• Publisher: Elsevier Inc,Elsevier Limited,Elsevier
• Subject: Anisotropy / Bias / Brain - diagnostic imaging / Case reports / Chronic effects / Chronic infection / COVID-19 / COVID-19 - diagnostic imaging / Diffusion Tensor Imaging - methods / Hospitalization / Humans / Infections / Literature reviews / Magnetic resonance imaging / Medical imaging / Neuroimaging / Olfaction disorders / SARS-CoV-2 / Severe acute respiratory syndrome coronavirus 2 / Substantia alba / Systematic review / White Matter - diagnostic imaging