Surgical Evacuation Thresholds for Subdural Hematomas
For acute subdural hematomas, surgical evacuation is indicated when thickness is ≥10 mm or midline shift is ≥5 mm, regardless of the patient's Glasgow Coma Scale score. 1
Anatomical Location Considerations
Supratentorial Subdural Hematomas
- Thickness ≥10 mm: Requires surgical evacuation regardless of GCS 1
- Midline shift ≥5 mm: Requires surgical evacuation regardless of GCS 1
- Smaller hematomas with neurological deterioration: Surgery indicated if:
- GCS decreases by ≥2 points from time of injury to admission
- Patient presents with asymmetric or fixed/dilated pupils
- Intracranial pressure exceeds 20 mmHg 1
Cerebellar Hemorrhages
- Size >3 cm in diameter: Surgical evacuation recommended 2
- Presence of brainstem compression: Immediate surgical evacuation indicated 2
- Hydrocephalus: Immediate surgical evacuation indicated 2
- Compressed basal cisterns: Surgical evacuation indicated 2
Timing Considerations
The timing of surgery is critical for optimal outcomes:
- For acute subdural hematomas meeting surgical criteria, evacuation should be performed as soon as possible 1
- In elderly patients with good neurological exam, delayed intervention may be considered with close neuromonitoring 3
- Ultra-early craniotomy (within 4 hours from onset) may increase risk of rebleeding 2
Surgical Approach
When surgical evacuation is indicated:
- Craniotomy with or without bone flap removal and duraplasty is recommended for comatose patients (GCS <9) 1
- Minimally invasive approaches may be considered for specific cases, with several studies suggesting better outcomes compared to standard craniotomies 2
- Decompressive craniectomy may be considered for patients with elevated ICP refractory to medical management 2
Risk Factors for Hematoma Progression
For initially non-operative subdural hematomas, monitor closely for progression if:
- Large initial hematoma volume 4
- Significant midline shift on initial CT scan 4
- These patients may require delayed surgical evacuation (median 17 days after trauma) 4
Special Considerations
- Ventricular catheter placement alone is insufficient for cerebellar hemorrhages with compression or hydrocephalus 2
- Monitor for contralateral hematoma formation after surgical evacuation, especially in elderly patients 5
- The ratio between maximal hematoma thickness and midline shift (H/MS ratio) can be a prognostic tool, with values ≤0.79 associated with poorer outcomes 6
Monitoring After Decision Not to Operate
For patients not meeting surgical criteria initially:
- Implement close neurological monitoring
- Serial CT scans to evaluate for hematoma progression
- Approximately 35% of initially non-operative acute subdural hematomas may eventually require surgical evacuation 4
The decision for surgical evacuation must be made promptly when criteria are met, as delays can significantly impact mortality and functional outcomes. While guidelines provide clear thresholds, the individual patient's clinical condition and trajectory remain important considerations in the surgical decision-making process.