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Perimesencephalic hemorrhage

Case contributed by Frank Gaillard
Diagnosis almost certain

Note: This case has been tagged as "legacy" as it no longer meets image preparation and/or other case publication guidelines.

mri

Prepontine cistern shows an intermediate to hyperintense signal on T1 and hypointense signal on T2 mostly reflecting prepontine hemorrhage. Note how the blood is confined by the anterior pontine membranes that separate the prepontine cistern (midline) from the cerebellopontine cisterns (laterally).

Case Discussion

The presence of subarachnoid hemorrhage with no aneurysmal or vascular source, often limited to the interpeduncular fossa and prepontine cistern is referred to a perimesencephalic hemorrhage. It is essential that extensive vascular imaging is performed (CTA, MRA and DSA) to ensure that a small arterial source is not present. This was performed in this instance. 

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