Subdural hematoma

  • Blood accumulation between the inner layer of the dura and the arachnoid
  • Most aSDH are traumatic and result from tearing of bridging cortical veins that cross the subdural space or, less commonly, tearing of cortical arteries adjacent to a skull fracture
  • aSDH may occasionally result from aneurysm rupture, bleeding metastases or spontaneous hemorrhage in patients with coagulopathy or on anticoagulants
  • Incidence of acute subdural hematoma (aSDH) is 10-20% of head trauma admissions
  • Can occur at any age and male:female ratio is 1:1
  • Presentation may vary from asymptomatic to comatose. Often no “lucid interval”. More insidious course than EDH, with slower progression
  • Delayed deterioration is common, especially in the elderly and patients on anticoagulants

Radiologic appearance

  • CT: Crescent-shaped extraaxial collection that may cross sutures and spread along but not across dural folds (tentorium, falx)
  • 60% are hyperdense and 40% may be mixed-attenuation
  • Hypodense areas within larger hyperdense aSDH indicate rapid bleeding (“swirl sign”)
  • aSDH in extremely anemic patients (Hb 8-10g/dL) or patients with coagulopathy may appear isodense to cortex
  • Mixture with CSF leaking from torn arachnoid may produce mixed attenuation
  • Subacute SDH (4 days to 3 weeks old) appear isodense on CT (if no re-bleeding occurs)
  • Chronic SDH (>3 weeks) approach CSF density (if no re-bleeding occurs)
  • MR: aSDH appear isointense to cortex on T1, hypointense to cortex on T2, iso- or hyperintense to CSF on FLAIR and hypointense on T2*. DWI may show patches of restricted diffusion in the underlying cortex

Findings associated with worse outcome

  • aSDH thickness >20mm (35-90% mortality)
  • Difference between midline shift and hematoma thickness >3mm

Management

Indications for surgical management:

  • aSDH with thickness >10mm or causing midline shift >5mm should be evacuated regardless of GCS
  • aSDH with thickness <10mm and midline shift <5mm should be evacuated if:
    1. Patient’s GCS has dropped by ≥2 from injury to admission
    2. and/or the pupils are asymmetric or fixed and dilated
    3. and/or ICP is >20mmHg
  • ICP should be monitored in all patients with aSDH and GCS <9



References

  • Greenberg M Handbook of Neurosurgery 8th edition, Thieme
  • Surgical management of traumatic acute subdural hematoma in adults: a review Neurol Med Chir (Tokyo). 2014;54(11):887-94. doi: 10.2176/nmc.cr.2014-0204
  • Evidence based diagnosis and management of chronic subdural hematoma: A review of the literature J Clin Neurosci. 2018 Apr:50:7-15. doi: 10.1016/j.jocn.2018.01.050
  • Updates on the diagnosis and management of subdural hematoma JAAPA. 2024 Aug 1;37(8):9-15. doi: 10.1097/01.JAA.0000000000000055