Subdural Hematoma

  • Etiology: venous hemorrhage due to tear of bridging veins and or intradural venous plexus, anticoagulation
  • Imaging: semilunar / crescent shape, crosses sutures, does not cross falx or tentorium
    — Hyperacute – inner layer of high density clotted blood + outer layer of low density nonclotted blood
    — Acute – high density clotted blood
    — Hygroma – post traumatic acute low density subdural collection, not all acute subdural collections are dense on CT, a subdural collection can be hypodense similar to CSF due to a CSF tear, subdural hematomas in anemic patients may also be low density
    — Chronic – common at convexity + posterior fossa, contrast enhancing membrane, follow CSF signal
  • Note: can occur infratentorial as well as supratentorial
  • Clinical: when seen in infants < 2 years old without significant trauma history need to rule out abuse
  • Imaging evolution of subdural hematoma on CT:
    — Up to 3 hours – hypodense
    — 1 day to 1 week – hyperdense
    — 1 week to 4 weeks – isodense
    — 1 month and up – hypodense
  • Note: variation may be seen in acute subdural hygroma, subdural hematoma in anemic patient, CSF leak into subdural collection through torn arachnoid membrane

Cases of Subdural Hematoma

CT of subdural hematoma
Axial CT without contrast of the brain with normal (left) and sharpened (right) windows shows a left hemispheric high density cresenteric intracranial extra-axial fluid collection that extends anteriorly along the falx.
US of subdural hematoma and intracerebral hemorrhage in patient on extracorporeal membrane oxygenation (ECMO)
Coronal US of the brain (below) shows echogenic material in right subdural space. Coronal and sagittal US of the brain (above) shows a right parietal round mixed echogenicity lesion.