- Clinical science
Subdural hematoma (SDH) refers to bleeding between the dura mater and arachnoid membrane. It is caused by head trauma that results in a tear in the bridging vein, which connects the superficial cerebral veins to the dural venous sinuses. The onset of symptoms may be acute, subacute, or chronic. Symptoms of SDH include headaches, changes in mental status, and focal neurologic deficits. CT and MRI scans are used to diagnose SDH, which presents as a crescent-shaped collection of blood that crosses the suture lines but not the falx or tentorium. Treatment may be surgical (e.g., trephination) or supportive, depending on the size of the subdural hematoma. Supportive therapy involves close clinical monitoring, normalizing coagulation parameters of patients on anticoagulant therapy, and preventing intracranial hypertension The prognosis of patients with chronic SDH is significantly better than those with acute SDH.
Classification is based on the onset of symptoms after the inciting event.
- Acute SDH: immediately after trauma or rapidly within 72 hours
- Subacute SDH; : 4–21 days after trauma
- Chronic SDH: > 21 days after trauma
Sex: ♂ > ♀ (3:1)
Epidemiological data refers to the US, unless otherwise specified.
Rupture of the bridging veins caused by:
- Blunt head trauma (most common)
- Nontraumatic intracranial hemorrhage
- Idiopathic, or iatrogenic (i.e., surgical) causes
SDH may occur after trivial trauma in patients with multiple risk factors!
Symptoms and their onset depend on the size, location, and rate of growth of the SDH.
- Impaired consciousness and confusion
- Focal neurologic signs (i.e., hemiparesis , gait, speech, or visual impairment, personality changes, or a dilated or nonreactive pupil )
- Memory impairment
Both SDH and epidural hematoma can occur after head trauma and cannot be differentiated based on symptoms alone!
- SDH is diagnosed on brain imaging.
- Appearance on brain imaging
- Crescent-shaped, concave hemorrhage that crosses suture lines but not the midline
- Varies depending on clot age and organization:
|Acute SDH||Hyperdense with respect to the cortex||Hypointense to isointense with respect to grey matter|
|Subacute SDH||Isodense with respect to the cortex after 10–14 days||Mostly hyperintense|
|Chronic SDH||Hypodense with respect to the cortex and may appear isodense with respect to cerebrospinal fluid||Mostly isointense with respect to cerebrospinal fluid|
In contrast to SDH, epidural hematoma is lentiform on imaging and does not cross suture lines but can cross the falx or tentorium!
Treatment depends on size and onset of SDH, as well as the patient's condition.
- Close clinical monitoring (especially neurological status)
- Measuring and optimizing intracranial pressure; see
- Normalizing of clotting parameters
- Conservative treatment
Indications (Only one of the following criteria must be met.)
- Clinical signs of herniation
- Unstable neurologic status
- Midline shift > 5 mm
- Hematoma > 10 mm
- Indications (Only one of the following criteria must be met.)
- Urgent neurosurgery consult for consideration of surgical intervention and ICP monitoring.
- Airway management
- Establish IV access.
- Identify and treat any underlying coagulopathy. 
- Stop all anticoagulants and NSAIDs (including aspirin).
- Urgent anticoagulant reversal, if applicable
- Consider hematology consult for complex cases (e.g., recent DOAC use).
- Avoid platelet transfusion unless surgical intervention is planned or the patient is thrombocytopenic (platelet count < 75,000). 
- Blood pressure management
- Consider invasive blood pressure monitoring.
- Target blood pressure: SBP < 180 mm Hg and MAP 80–110 mm Hg (goal CPP > 60 mm Hg) 
- Avoid aggressive lowering of blood pressure.
- Supplemental oxygen/ventilation as needed to maintain PaO2 > 60 mm Hg. 
- Consider prophylactic anticonvulsive therapy (e.g., levetiracetam ). 
- Identify and treat any complications (e.g., seizures, ).
- Euglycemia: Avoid hypoglycemia and hyperglycemia.
- Normothermia: antipyretics for fever
- Normovolemia: IV fluids for hypovolemia
- Admit to neurosurgical ICU.
- Close observation, GCS monitoring, and serial CT scans during the first 36 hours after bleed. 
- VTE prophylaxis
- The prognosis of chronic SDH is better than that of acute SDH.