Axial non-enhanced head CT showing a left sided holohemispheric subdural hematoma.

Subdural hematomas are collections of blood between the brain’s tough dural covering and thin arachnoid covering. The most common cause is tearing of venous structures, and it can be caused by minor trauma. Patient’s on anticoagulants, thrombocytopenia or significant cerebral atrophy are at higher risk.

Clues to the presence of subdural hemmorhages include:

  • No extension into the sulci (as would be seen in subarachnoid bleeding)
  • Concave shape, like a crescent
  • Not typically associated with skull fractures, unlike epidural hematomas
  • Typically slowly expanding
Coronal subdural hematoma – notice the compression of the brain on the left side, and again the lack of extension of the blood into the cerebral sulci.
Axial T2W FLAIR – the same patient, showing subacute blood on MRI.
I included a photo of Ubehebe crater to remind you of the convex shape of subdurals!