Causes of Subdural Hematoma
Traumatic brain injury is the most common cause of subdural hematomas, with high-energy impacts like motor vehicle collisions and falls being the primary mechanisms of injury. 1, 2
Traumatic Causes
- Motor vehicle collisions - The leading cause of subdural hematomas, particularly in younger populations 2
- Falls - Common cause especially in elderly patients, even from low heights 3, 2
- Assaults and direct head trauma - Blunt force trauma to the head can cause subdural bleeding 4
- Frontal bone injuries - High-energy impacts to the frontal bone can result in subdural hematomas, with 8-10% of patients with frontal sinus fractures developing subdural hematomas requiring surgical intervention 1
Non-Traumatic and Iatrogenic Causes
- Anticoagulation therapy - Significant risk factor for spontaneous subdural hematomas and can worsen traumatic ones 5, 3
- Antiplatelet therapy - Present in up to 62.5% of patients with acute-on-chronic subdural hematomas 3
- Coagulopathies - Increase risk of progressive bleeding and hematoma expansion 5
- Neurosurgical procedures - Can occur as a complication of cranial surgery 4
Anatomical Considerations
- Bridging vein rupture - Tearing of veins that bridge from the brain surface to the dural sinuses is the primary mechanism 6
- Dural laceration - Can allow blood to migrate from one compartment to another (e.g., from epidural to subdural space) 7
- Falx cerebri region - Interhemispheric subdural hematomas form specifically in the space between cerebral hemispheres along the falx cerebri 5
Age-Related Factors
- Elderly patients - More susceptible due to brain atrophy creating additional space for hematoma expansion and stretching of bridging veins 2
- Children - In pediatric populations, subdural hematomas are the most common intracranial abnormality in abusive head trauma, often presenting as multiple, convexity, interhemispheric, or posterior fossa collections 1
Clinical Pearls
- Subdural hematomas can be classified as acute, subacute, or chronic based on timing and imaging characteristics 4
- Patients with low Glasgow Coma Scale scores at presentation have worse outcomes and higher mortality 2
- Rapid reversal of anticoagulation is critical in patients with subdural hematomas to prevent hematoma expansion 5
- The risk of progressive bleeding is greater when baseline CT scan is performed early after injury and when coagulopathy is present 5
Diagnostic Considerations
- Non-contrast CT is the first-line imaging modality for diagnosing acute subdural hematomas 1
- MRI provides better characterization of subacute and chronic subdural collections and can detect smaller hematomas missed on CT 1
- Care should be taken when attempting to determine the age of subdural hematomas by imaging alone, as collections of low or intermediate density may not necessarily indicate chronic blood products 1