Subdural hematohygroma

Last revised by Henry Knipe on 24 Jan 2023

Subdural hematohygromas are subdural hygromas into which bleeding has occurred. They are distinct from, and should not be confused with, acute on chronic subdural hematomas or with acute subdural hematomas with separation of blood into plasma and hematocrit.

Radiographic features


Subdural hematohygromas are usually imaged with CT and have the following features:

  • presence of mass effect, sulcal effacement, and midline shift

  • high density (blood) dependently and water-density (CSF) anti-dependently

  • smooth and often sharp transition between low and high-density collections

  • absence of internal strand-like membranes paralleling the skull vault (indicating a chronic subdural hematoma)

Differential diagnosis

  • acute subdural hematoma: it is difficult to distinguish subdural hematohygromas from acute subdural hematomas where blood has settled and separated with a hematocrit effect (red blood cells inferiorly and plasma superiorly) unless there are prior studies demonstrating a pre-exisitng subdural hygroma

  • acute on chronic subdural hematoma: the key feature is the presence of membranes within the collection that result in multiple fluid-fluid levels or heterogeneity; care must be taken to not mistake acute on chronic hematomas with hyperacute hematomas with active bleeding

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