Subdural Hematoma (SDH) - Management

Classification (by time to presentation)

Imaging

General Principles

• SDH results from tearing of bridging veins traversing the subdural space (between inner dura leaf and arachnoid)
• Key rule: "It could always be a subdural" - image any comatose or confused patient even without focal signs
• Reverse anticoagulation promptly in patients on warfarin/NOACs - continued venous leakage is particularly dangerous
• Prognostic factors for acute SDH: age, time from injury to treatment, pupillary abnormalities, coma (immediate vs. lucid interval), hematoma volume

Acute SDH - Treatment

Conservative (observation)

• Thin crescentic clots without symptoms or signs of raised ICP
• Small SDH causing no symptoms - follow serial CT; most self-absorb
• Asymptomatic patient with small volume, no midline shift

Surgical - Indications

• SDH ≥10 mm thickness OR any midline shift with neurological deterioration
• Coma, hemiparesis, unilateral pupillary dilation (signs of herniation)
• Rapidly deteriorating/comatose patient = emergency craniotomy
• GCS <8 with acute SDH - surgical mortality is 40-60%

Surgical Technique

1. Burr holes - sufficient for early clots before full organization; blood/clot extruded, gentle suction
2. Craniotomy - required for larger hematomas, especially if several hours old with clot formation; also allows bleeding point control
3. Craniectomy (decompressive) probably adds little benefit to craniotomy alone

Key: The interval between loss of consciousness and surgical drainage is the most important determinant of outcome. - Adams & Victor's Principles of Neurology, 12th Ed.

Chronic SDH - Treatment

Conservative

• Small collections causing no mass effect on imaging + minimal symptoms
• Serial imaging with clinical observation is a reasonable approach
• Oral corticosteroids (e.g., prednisone) - reduce vasogenic edema from the leaky hematoma membrane; can cause significant reduction and even resorption (as illustrated in Plum & Posner's series showing near-complete resorption at 2 months)
• Mild hydration + flat head of bed - encourages brain re-expansion

Surgical - Indications

• Chronic SDH >1 cm or any symptomatic SDH
• Neurological deterioration, increasing mass effect

Surgical Technique - Burr Hole Drainage (first-line)

1. Single burr hole over the dependent edge of collection
2. Copious irrigation until fluid runs clear
3. Second anterior burr hole if collection not draining adequately (membrane compartmentalization)
4. Convert to craniotomy if:
   • SDH too congealed for irrigation drainage
   • Complex membranes prevent effective drainage
   • Persistent hemorrhage beyond reach of bipolar cautery

Post-operative measures

• Subdural drain left in place for 1-2 days - shown to reduce recurrence risk
• Flat head of bed + mild hydration to encourage brain expansion
• High inspired oxygen - helps draw nitrogen out of residual cavity
• Follow-up CT at 1 month to document resolution
• Note: corticosteroid use post-operatively has been associated with higher morbidity without benefit per Schwartz's Surgery

Anticoagulation Reversal (Critical Step)

Middle Meningeal Artery Embolization (MMAE) - Emerging Therapy

• In nonsurgical chronic SDH patients: MMAE significantly reduced progression (RR 0.36, 95% CI 0.22-0.60, p<0.001)
• In surgical patients: MMAE did not significantly reduce recurrence
• No effect on functional outcome

Tranexamic Acid (TXA) in Chronic SDH

Special Populations

• Elderly/atrophied brain: High risk; even minor or forgotten trauma causes SDH; bilateral in ~20%
• Anticoagulated patients: Highest priority reversal; acute SDH especially dangerous
• Alcoholics / hemodialysis patients: Chronic SDH risk factors; coagulopathy must be corrected
• Infants <2 years: High risk; bifrontal chronic SDH possible without significant trauma history (non-accidental injury must be considered)
• Posterior fossa SDH: Headache, vomiting, CN palsies, ataxia - often missed on CT; low threshold for MRI

Non-Surgical (Conservative) Management of Subdural Hematoma

When to Manage Conservatively

1. Observation + Serial Imaging

• Clinical observation combined with serial CT is a reasonable approach for patients with few symptoms and small chronic subdural collections that do not cause mass effect
• Many small SDHs self-absorb; follow-up CT at 4-6 weeks documents resolution
• Any neurological deterioration on observation = triggers surgical re-evaluation
• Harrison's Internal Medicine 22e, Goldman-Cecil Medicine

2. Corticosteroids

• Oral prednisone rapidly and effectively reverses symptoms in chronic SDH
• Plum & Posner document a case series where bilateral SDH (11.5 mm + 8 mm) treated with oral prednisone showed near-complete resorption by 2 months on serial imaging
• The DUBS trial (Hutchinson et al., NEJM 2020) found dexamethasone reduced the need for surgery in chronic SDH but was associated with more adverse events (diabetes, infection)
• Current consensus: corticosteroids are not routinely recommended post-operatively (higher morbidity without benefit), but may be used for conservative management of small symptomatic chronic SDH

Note: Goldman-Cecil states corticosteroids are "not beneficial" as routine treatment, while Plum & Posner support their use for the edema component - the evidence is mixed, and patient selection matters.

3. Reversal of Anticoagulation / Antiplatelet Agents

• Coexisting electrolyte disturbance and infection must also be excluded and corrected
• Bailey & Love's Surgery 28e

4. ICP Management (Raised Intracranial Pressure)

• Head of bed elevation 30°
• Avoid hypotonic fluids - use isotonic/slightly hypertonic solutions
• Osmotic agents (mannitol, hypertonic saline) - used cautiously; note that rapid osmotic diuresis in elderly patients can paradoxically worsen SDH by causing brain shrinkage and further tearing of bridging veins
• Avoid hypercarbia - maintain normal PaCO₂; short-term hyperventilation as bridge therapy only
• Seizure prophylaxis - prophylactic AEDs are not routinely recommended in chronic SDH

5. Positioning

• Flat head of bed (after drainage, or in non-operative management) encourages brain re-expansion into the subdural space
• Mild hydration helps expand the brain
• High inspired oxygen may facilitate nitrogen washout from the residual cavity, promoting collapse and resorption

6. Tranexamic Acid (TXA) - Antifibrinolytic

• 4 RCTs, 148 patients
• Trend toward earlier and more complete resolution after burr hole drainage
• No statistically significant reduction in recurrence or post-operative volume
• Safe profile - no significant adverse events

7. Middle Meningeal Artery Embolization (MMAE) - Emerging

• MAGIC-MT trial (Liu et al., NEJM 2024, PMID 39565989): 722 patients - MMAE did not significantly reduce 90-day symptomatic recurrence/progression (6.7% vs 9.9%, p=0.10) but reduced serious adverse events (6.7% vs 11.6%, p=0.02)
• EMBOLISE trial (Fiorella et al., NEJM 2025, PMID 39565980): also assessed MMAE
• Meta-analysis (Gillespie et al., Acta Neurochir 2025, PMID 40493076): In non-surgical patients, MMAE significantly reduced progression (RR 0.36, 95% CI 0.22-0.60, p<0.001); in surgical patients - not significant

8. Statins

• Proposed to reduce neuroinflammation and membrane neovascularization
• Currently under investigation; not recommended for routine use
• Goldman-Cecil Medicine

Summary Table