Description

• Classification of subdural hematoma (SDH):
  • Acute: Diagnosis within the first 2 d
  • Subacute: Diagnosis 3 d–2 wk
  • Chronic: Diagnosis after 2 wk
• CT description:
  • Rarely crosses midline
  • Does cross suture lines
  • Inner margins are often seen to be irregular
• Acute:
  • Most commonly due to acceleration–deceleration forces and less commonly from direct trauma
  • Sagittal movement of the head causes stretch of parasagittal bridging veins
  • Other bleeding sites include:
    • Laceration of dura
    • Venous sinus injury
    • Cortical arteries
    • Nontraumatic injuries: Intracerebral aneurysm rupture, arteriovenous malformation, coagulation disorder, arterial HTN, drug or alcohol abuse
• Chronic:
  • Encapsulated hematoma most likely caused by repeated small hemorrhages of bridging veins

Etiology

• Acute:
  • Most common type of intracranial hematoma (66–70%)
  • Occurs most commonly at cerebral complexities > falx cerebri > tentorium cerebelli
  • Peak incidence 31–47 yr, second peak >75 yr
  • Represents 26–63% of blunt head injury
  • Motor vehicle crash (MVC) is the most common cause overall
  • Falls and assault more commonly result in isolated SDH (72%) than do MVCs (24%)
  • Elderly patients and those with seizure disorders are at increased risk
  • Mortality is related to presenting signs and symptoms as well as comorbidities:
    • Mortality is 50% for age >70
    • <1/2 present as simple extra-axial collection (22% mortality rate)
    • ∼40% of patients will have complicated SDH: Parenchymal laceration or intracerebral hematoma (mortality rate >50%)
    • Third group associated with contusion (30% mortality rate with functional recovery of 20%)
• Coagulopathy: INR >2 increases risk of bleed ×2, INR >3 is associated with larger initial volume and increased expansion
• Atraumatic can occur with AV malformation rupture, meningiomas, dural metastasis
• Chronic:
  • Most common in babies or elderly with atrophy:
    • Associated with infarction in underlying brain
• 75% of patients are >50
• <50% have history of head trauma
• 50% are alcoholic
• Epilepsy and shunting procedures

• May occur secondary to trauma at birth
• Nonaccidental trauma more common