What is the difference between a Subdural Hematoma (SDH) and an Epidural Hematoma (EDH)?

From the Guidelines

Subdural and epidural hematomas are distinct types of brain bleeds with important differences in location, cause, presentation, and management, with subdural hematomas having a higher mortality rate and often requiring more urgent surgical intervention. The key differences between subdural and epidural hematomas lie in their location, with subdural hematomas occurring between the dura mater and the brain, and epidural hematomas forming between the skull and dura mater 1. Some of the main characteristics of subdural hematomas include:

• Typically resulting from tearing of bridging veins following trauma
• Crescent-shaped appearance on imaging
• Often develops slowly, presenting with headache, confusion, and neurological deficits over hours to days
• More common in elderly patients and those on anticoagulants In contrast, epidural hematomas are characterized by:
• Usually forming from arterial bleeding (often the middle meningeal artery) after skull fracture
• Lens-shaped appearance on imaging
• Typically presents with a lucid interval followed by rapid deterioration, making it a more immediate neurosurgical emergency Treatment for both conditions may include observation for mild cases, but surgical evacuation is often necessary for significant hematomas causing neurological symptoms or increased intracranial pressure, with the type of surgery varying between centers, as shown by a median odds ratio (MOR) of 1·84 for acute surgery in acute subdural haematoma, and an MOR of 2·68 for primary decompressive craniectomies 1. The mortality rate for epidural hematomas is approximately 10-20% with prompt treatment, while subdural hematomas carry a higher mortality rate of 50-90% for acute cases, reflecting their different pathophysiology and typical patient populations.

From the Research

Differences between Subdural Hematoma (SDH) and Epidural Hematoma (EDH)

• Location:
  • Subdural Hematoma (SDH) occurs between the dura mater and the arachnoid mater 2, 3
  • Epidural Hematoma (EDH) occurs between the dura mater and the skull 4, 5
• Causes:
  • SDH is often associated with trauma, anticoagulation, and aging 2, 3
  • EDH can be caused by trauma, arterial or venous rupture, and can sometimes resolve spontaneously 4, 5
• Diagnosis:
  • Both SDH and EDH can be diagnosed using imaging techniques such as MRI and CT scans 4, 6
  • MRI is particularly useful in differentiating between epidural and subdural hematomas, especially using transverse T2*-weighted gradient echo sequences 4
• Treatment:
  • SDH treatment focuses on managing intracranial hypertension, maintaining cerebral perfusion, and preventing seizures 2, 3
  • EDH treatment may involve surgical evacuation, especially in cases of chronic EDH or those that do not resolve spontaneously 5
• Prognosis:
  • SDH has a high recurrence rate and significant morbidity and mortality 2
  • EDH can be life-threatening, but small-volume EDHs can resolve spontaneously, and chronic EDH may require surgical treatment 5