How do contusions present on imaging, and which MRI technique highlights associated microhemorrhages?

How do contusions present on imaging, and which MRI technique highlights associated microhemorrhages?

• A. Subarachnoid hemorrhages that appear as uniform hyperdensities on CT.
• B. Contusions are cortical/subcortical bruising; CT may show irregular, mixed-density lesions; MRI with susceptibility-weighted imaging highlights microhemorrhages.
• C. Contusions show diffuse axonal injury on MRI.
• D. Contusions cannot be distinguished from other hemorrhages on imaging.

Answer: (B)

Contusions are bruising of brain tissue that typically involve the cortex and underlying subcortical white matter. On CT they often look irregular with mixed density, reflecting stunned tissue, edema, and hemorrhage of different ages rather than a uniform area. When MRI is used, susceptibility-weighted imaging (SWI) is especially good at picking up microhemorrhages within these contusions because it is highly sensitive to magnetic field distortions from blood products. Those tiny bleeds may be invisible on CT but appear clearly on SWI as small signal voids, helping to define the full extent of the injury.

Contusions are bruising of brain tissue that typically involve the cortex and underlying subcortical white matter. On CT they often look irregular with mixed density, reflecting stunned tissue, edema, and hemorrhage of different ages rather than a uniform area. When MRI is used, susceptibility-weighted imaging (SWI) is especially good at picking up microhemorrhages within these contusions because it is highly sensitive to magnetic field distortions from blood products. Those tiny bleeds may be invisible on CT but appear clearly on SWI as small signal voids, helping to define the full extent of the injury.