Transient disappearance of microbleeds in the subacute period based on T2*-weighted gradient echo imaging in traumatic brain injury.

We report three cases of traumatic microbleeds evaluated by sequential observation. Hypo-intensities on T2* gradient echo imaging (T2*GEI) appeared just 2-3 h after the injury (the hyper-acute period). However, these hypo-intensities on T2*GEI disappeared or became obscure 2-6 days after the injury (the subacute period). A follow-up MRI again revealed clear hypo-intensities on T2*GEI 1-3 months after the injury (the chronic period). Our cases indicate that hypo-intensities on T2*GEI might change dynamically from the hyper-acute to the chronic period. The differences of susceptibility effects by hematoma age might be the cause of this dynamic change.