What is the rationale for performing an emergency burr hole in subacute subdural (SDH) hematoma?

Emergency Burr Hole in Subacute Subdural Hematoma

Emergency burr hole drainage in subacute subdural hematoma is performed to rapidly decompress the brain and prevent irreversible neurological deterioration from mass effect and impending herniation, serving as either definitive treatment or a life-saving temporizing measure before definitive craniotomy. 1, 2

Primary Rationale for Emergency Burr Hole

Immediate Decompression

• The fundamental goal is rapid reduction of intracranial pressure to prevent or reverse cerebral herniation, which is the most time-sensitive life-threatening complication 2
• Burr hole evacuation achieves immediate pressure relief within minutes, compared to the delay required for preparing a formal craniotomy 2, 3
• In patients with altered consciousness and signs of herniation, even minutes of delay can result in irreversible brainstem injury and death 1, 2

Evidence for Clinical Benefit

• A retrospective study demonstrated that patients with acute subdural hematoma and cerebral herniation who underwent emergent single burr hole evacuation followed by definitive surgery had significantly higher Glasgow Coma Scale scores at 1 month (p=0.04) and 6 months (p=0.03) compared to those who received only mannitol infusion before surgery 2
• The same study showed significantly better Glasgow Outcome Scale scores and activities of daily living at 6 months in the burr hole group (p<0.05) 2
• For non-acute (subacute and chronic) subdural hematomas specifically, single burr hole evacuation with saline irrigation achieved 90% excellent outcomes at 6 weeks, with only 4.5% poor outcomes 4

Clinical Scenarios Requiring Emergency Burr Hole

Definitive Treatment Indication

• Burr hole drainage is the preferred first-line surgical treatment for symptomatic subacute subdural hematomas presenting with altered consciousness, vomiting, and neurological deficits 1
• The American College of Surgeons recommends burr hole evacuation as first-line treatment for symptomatic chronic subdural hematomas, which applies to subacute presentations as well 1

Temporizing Bridge to Definitive Surgery

• When a patient presents with impending herniation and the operating room is not immediately available, burr hole evacuation can be performed in the emergency department while simultaneously preparing for definitive craniotomy 5
• This approach is particularly valuable in facilities without immediate neurosurgical capability, where burr hole drainage can stabilize the patient for transfer 3

Mechanism of Therapeutic Effect

Pressure Relief Components

• Burr hole evacuation addresses multiple pathophysiological mechanisms: decompression of brain parenchyma, removal of the semisolid hematoma component, and removal/dilution of endogenous fibrinolytic agents that perpetuate hematoma expansion 4
• Saline irrigation through the burr hole enhances evacuation of liquefied hematoma contents and dilutes inflammatory mediators 4

Cerebral Perfusion Restoration

• Rapid decompression restores cerebral perfusion pressure by reducing intracranial pressure, preventing secondary ischemic injury 2
• This is critical because maintaining cerebral perfusion pressure ≥60 mmHg is essential for preventing secondary brain injury 6

Critical Caveats and Pitfalls

When Burr Hole Alone Is Insufficient

• Craniotomy should be reserved for acute-on-chronic subdural hematomas with solid components that cannot be adequately evacuated through a burr hole 1
• If initial burr hole evacuation does not provide sufficient decompression on post-procedure CT, immediate craniotomy at the same site should be performed 5

Contraindications and Complications

• In spontaneous intracranial hypotension with subdural hematoma, burr hole drainage can paradoxically worsen brain herniation and should be avoided 7
• Delaying surgical intervention in symptomatic patients with altered consciousness leads to neurological deterioration and poorer outcomes 1
• Patients on anticoagulants or antiplatelet therapy require reversal prior to intervention, with target platelet count >100,000/mm³ 1, 6

Post-Procedure Management

• Maintain euvolemia and avoid hypovolemia to optimize cerebral perfusion; hypervolemia does not improve outcomes 1
• Consider subdural drain placement during surgery to reduce recurrence rates 1
• Monitor for post-operative complications including seizures and reaccumulation requiring re-evacuation (occurred in approximately 11% of cases) 1, 4