Bilateral Burr Hole Craniostomy: Order of Evacuation
There is no evidence-based guidance on which side to evacuate first in bilateral chronic subdural hematoma (CSDH), as no studies have specifically addressed the sequence of evacuation based on hematoma thickness. In the absence of direct evidence, the decision should be guided by clinical factors rather than hematoma thickness alone.
Recommended Approach to Sequencing
Prioritize evacuating the side causing the most mass effect or neurological symptoms first, regardless of thickness. The following clinical algorithm should guide your decision:
Primary Decision Factors:
- Midline shift direction: Evacuate the side causing greater midline shift first 1
- Symptomatic lateralization: If focal deficits are present, evacuate the symptomatic side first 2
- Acute-on-chronic changes: If one side shows acute bleeding components, address that side first to prevent further deterioration 1
- Brainstem compression: If either side contributes more to brainstem compression, prioritize that side 3
Technical Considerations:
The thickness of the hematoma itself is not a validated predictor of outcome or surgical priority. The available evidence focuses on:
- Membrane thickness (not hematoma thickness) correlates with recurrence risk, with thicker membranes associated with higher recurrence rates 2
- Subdural drain placement significantly reduces recurrence rates (OR 0.39,95% CI 0.28-0.55) and mortality (OR 0.65,95% CI 0.43-0.97) regardless of which side is evacuated first 4
- Brain re-expansion at the end of evacuation is more important than initial hematoma characteristics 2
Practical Surgical Sequence
When both sides are equally symptomatic, evacuate the larger hematoma first to achieve maximal ICP reduction and allow better brain re-expansion. This approach is based on:
- Larger volume hematomas contribute more to elevated ICP 1
- Adequate brain re-expansion after evacuation reduces recurrence risk 2
- Earlier intervention (within 8 hours when possible) may improve outcomes 1
Critical Pitfalls to Avoid:
- Do not delay surgery to determine which side is "thinner" - timing of intervention is more important than sequence 1
- Do not rely solely on CT measurements - clinical examination and GCS score are stronger predictors of outcome than radiographic features 2
- Always use subdural drains bilaterally after evacuation, as this significantly reduces both recurrence and mortality 4
Post-Evacuation Management
After evacuating both sides:
- Monitor for adequate brain re-expansion on both sides, as persistent brain depth correlates with recurrence 2
- Maintain cerebral perfusion pressure >60 mmHg 5
- Continue drains until output is minimal and brain re-expansion is confirmed 4
The key determinant of outcome is not which side you evacuate first, but rather ensuring complete bilateral evacuation with adequate drainage and brain re-expansion. 4, 2