From microbleeds to axonal damage: current evidence and future directions

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.