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 tear in arachnoid membrane, subdural hematomas in anemic patients may also be low density
  • — Chronic – common at convexity + posterior fossa, contrast enhancing membrane forms at 1 week, follow CSF signal, may come from acute subdural hematoma or subdural hygroma
  • Note: can occur infratentorial as well as supratentorial
  • DDX: benign enlargement of the subarachnoid space can mimic chronic bilateral subdural hematomas
  • Clinical: when seen in infants < 2 years old without significant trauma history need to rule out child abuse as subdural hematoma is most common intracranial manifestation of child abuse
  • Imaging evolution of subdural hematoma on CT:
    — Up to 3 hours – hypodense
    — 3 hours to 7-10 days – 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
  • Imaging evolution of intracerebral hemorrhage evolution on MRI:
    — Note: this is most commonly used to date subdural hematomas
AgeStateT1WIT2WI
< 1 dayOxyHbIsoBrightHyperacute
1-3 daysDeOxyHbIsoDarkAcute
3-7 daysIntracellularMetHbBrightDarkEarly Subacute
1-3 weeksExtracellularMetHbBrightBrightLate Subacute
> 3 weeksHemosiderinDarkDarkChronic

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.
Radiograph of parietal skull fracture and CT of chronic subdural hematomas in child abuse
AP radiograph of the skull shows a linear lucency in the left parietal bone that connects to the left lambdoid suture. Axial CT without contrast of the brain shows bilateral low density extra-axial fluid collections around the brain.
MRI of acute and chronic subdural hematomas in child abuse
Axial CT without contrast of the brain (upper left) shows bilateral large low density extra-axial fluid collections and a left frontal small high density extra-axial fluid collection. There is also prominence of the cortical sulci and the ventricular system. Axial T1 (upper right), T2 (lower left) and FLAIR (lower right) MRI without contrast of the brain better demonstrates the extra-axial fluid collections with the bilateral large collections being bright on T1 and T2 and the small left frontal collection being iso on T1 and dark on T2.
Radiograph of stellate skull fracture and CT of acute subdural hematoma due to accidental trauma
AP and lateral radiographs of the skull show numerous branching lucencies in the right parietal bone. Axial CT without contrast of the brain shows high density material in the right subgaleal tissues, a small high density cresenteric fluid collection in the right extra-axial space that extends posteriorly along the falx, and a mixed low-density and high density lesion in the right posterior parietal brain parenchyma.
CT of acute and chronic subdural hematomas in child abuse
Axial (above) and coronal (below) CT without contrast of the brain shows a right moderate sized high density cresenteric extra-axial fluid collection that extends around the entire right cerebral hemisphere as well as interhemispherically. There is also a left moderate sized low-density cresenteric extra-axial fluid collection.
CT of tricompartmental chronic subdural hematomas in child abuse
Axial CT without contrast of the brain shows very large low density extra-axial fluid collections supratentorially around the left and right cerebral hemispheres and infratentorially around the cerebellum. There is also a round high density focus along the posterior right falx.
CT of diffuse cerebral edema in child abuse
Axial CT without contrast of the brain shows normal density in the rounded top of the cerebellum (in the center of the left image) compared to the diffuse low-density throughout the cerebrum. There is obliteration of the basal cisterns and loss of the normal gray matter-white matter differentiation. There is also a small left sided high density extra-axial cresenteric fluid collection that tracks medially along the entire falx.