Subdural hemorrhage (summary)

This is a basic article for medical students and other non-radiologists

Subdural hemorrhage (SDH) is a collection of blood between the dura and the arachnoid layers of the meninges. They are common and can occur in any age range, usually related to a history of head trauma. Prognosis tends to depend on the extent of the bleed and associated mass effect.

The bleed in relation to the dura mater is the key anatomical difference between an subdural and a extradural hemorrhage. As a student, a helpful tip is to remember that the dura tightly adheres to the intracranial bony sutures. Thus, a subdural hemorrhage may freely move in the cranial cavity, producing the typical crescentic shape.

Reference article

This is a summary article; read more in our article on subdural hemorrhage.

Summary

• anatomy
  • subdural space
• epidemiology
  • children: non-accidental injury
  • adults: high energy trauma, e.g. road traffic collisions
  • elderly: falls (there may not be a clear history of trauma)
• presentation
  • acute
    • usually associated with head injury
      • may be associated contusions or extradural hemorrhage
    • underlying vascular malformations
  • subacute or chronic
    • confusion and vague neurological change
    • a classic cause of pseudodementia
    • beware patients on anticoagulants, e.g. warfarin
• pathophysiology
  • tearing of bridging veins found in the subdural space
  • veins are subject to shearing forces
    • occurs with lower forces in the elderly
• investigation
  • non-contrast CT head
• treatment
  • correction of abnormal coagulation
  • discussion with neurosurgical services
  • small subdural can be observed with repeated CT
  • surgical evacuation of the clot
    • may carry significant mortality and morbidity

Imaging

• role of imaging
  • initial diagnosis
  • assessment of the associated mass effect
  • look for an underlying cause
  • suggest further imaging
  • follow up
• radiographic features
  • general
    • typically unilateral
    • crescent distribution around the periphery
    • not limited by sutures
    • fill dural reflections (falx cerebri, tentorium)
  • CT
    • acute
      • hyperdense crescent
      • central hypodensity represents active bleeding
      • acute bleed mixed with CSF may appear less dense
      • density is variable in coagulopathic patients, e.g. warfarinised
    • subacute
      • over the first couple of weeks, the blood is broken down
      • density approaches that of the brain
      • they may be tricky to see
    • chronic
      • over time, the hematoma approaches CSF density
  • MRI
    • may be used to assess the underlying brain parenchyma
    • aging blood on MRI is a complex process