# From microbleeds to axonal damage: current evidence and future directions

## TL;DR

This paper reviews how cerebral microbleeds may indicate axonal damage in traumatic brain injury and discusses their use as imaging markers.

## Contribution

The paper synthesizes current evidence on cerebral microbleeds as potential markers of traumatic axonal injury in TBI.

## Key findings

- Cerebral microbleeds are associated with axonal injury and injury severity in traumatic brain injury.
- Susceptibility-based MRI and diffusion imaging are key methods for detecting and characterizing cerebral microbleeds.
- There is inconsistency in the literature regarding the interpretation and detectability of cerebral microbleeds.

## Abstract

Traumatic brain injury (TBI) represents a major public health challenge worldwide. Traumatic axonal injury (TAI) is a key determinant of outcome yet remains difficult to assess directly in vivo in routine clinical practice and is therefore typically inferred indirectly using advanced neuroimaging techniques. Cerebral microbleeds (CMBs), detected primarily with susceptibility-based MRI sequences, have emerged as putative imaging markers associated with axonal injury and injury severity in TBI. A broad and heterogeneous body of literature has explored their relevance using gradient-echo (GRE), susceptibility-weighted imaging (SWI), quantitative susceptibility mapping (QSM), and diffusion tensor imaging (DTI), as well as neuropsychological correlates. In this mini review, we provide a focused narrative synthesis of studies examining the detection, characterization, and interpretative framework of CMBs in TBI, with particular emphasis on susceptibility-based MRI and diffusion imaging approaches. We highlight areas of convergence and inconsistency in the literature and discuss methodological and conceptual considerations relevant to the use of CMBs as context-dependent imaging markers in TBI.

Overview of the proposed relationship between traumatic brain injury, cerebral microbleeds, and axonal damage, highlighting microbleed detectability and the multimodal assessment of white matter injury.Infographic showing the progression from traumatic brain injury to axonal damage, featuring detection of cerebral microbleeds through paramagnetic imaging, followed by neurocognitive assessment, histology for axonal injury, and diffusion imaging. Text highlights that cerebral microbleeds may serve as markers of white matter injury.

Overview of the proposed relationship between traumatic brain injury, cerebral microbleeds, and axonal damage, highlighting microbleed detectability and the multimodal assessment of white matter injury.