Subdural hemorrhage

Background

• Bleeding between the dura mater and arachnoid membrane, typically from bridging vein rupture
• Three types by timing:
  • Acute (<3 days) — hyperdense (white) on CT
  • Subacute (3-21 days) — isodense (may be difficult to see)
  • Chronic (>21 days) — hypodense (dark) on CT
• Most common in elderly and anticoagulated patients
• Acute SDH mortality: 50-90% (highest of all traumatic intracranial lesions)
• May occur with minimal or no trauma in the elderly and anticoagulated

Risk Factors

• Advanced age (cerebral atrophy stretches bridging veins)
• Anticoagulation / antiplatelet therapy
• Chronic alcohol use (cerebral atrophy, coagulopathy)
• Coagulopathy or thrombocytopenia
• Prior falls or head trauma (even minor)
• CSF shunt (overdrainage)

Clinical Features

Acute SDH

• Headache, altered mental status, decreasing GCS
• Ipsilateral fixed/dilated pupil (uncal herniation)
• Contralateral hemiparesis
• May present with coma from onset
• Associated with high-energy mechanism or fall in anticoagulated patients

Chronic SDH

• Insidious onset over weeks to months
• Headache, cognitive decline, confusion, personality changes
• Gait disturbance, falls
• Fluctuating neurologic symptoms (may mimic stroke or dementia)
• History of trauma often absent or trivial

Differential Diagnosis

• Epidural hemorrhage
• Traumatic subarachnoid hemorrhage
• Intracerebral hemorrhage
• Ischemic stroke
• Meningitis
• Dementia (chronic SDH)

Evaluation

• Non-contrast CT head — test of choice
  • Acute: hyperdense, crescent-shaped collection crossing suture lines
  • Chronic: hypodense, crescent-shaped; may have mixed density if rebleeding
  • Evaluate for midline shift, mass effect, herniation
• Labs: CBC, coagulation studies (PT/INR, PTT), type and screen
• If on anticoagulation: specific reversal levels (e.g., anti-Xa for DOACs)

Management

Acute SDH

• ABCs — intubate if GCS <=8
• Emergent neurosurgical consultation
• Reverse anticoagulation immediately:
  • Warfarin: 4-factor PCC (25-50 units/kg) + Vitamin K 10 mg IV
  • Dabigatran: Idarucizumab 5 g IV
  • Rivaroxaban/Apixaban: Andexanet alfa or 4-factor PCC
  • Antiplatelet agents: platelet transfusion if surgical candidate
• ICP management: head of bed elevation, osmotherapy (Mannitol or Hypertonic saline)
• Surgical indications: clot thickness >10 mm, midline shift >5 mm, GCS drop >=2 points

Chronic SDH

• Neurosurgical consultation for possible burr hole drainage
• Reverse anticoagulation
• Many small, asymptomatic chronic SDH may be observed with serial imaging
• Symptomatic chronic SDH: typically surgical (burr hole or craniotomy)

Disposition

• All acute SDH: admit, neurosurgical evaluation, ICU for operative or declining patients
• Chronic SDH: admit if symptomatic, new, or enlarging; small stable chronic SDH may have outpatient neurosurgery follow-up

Modified brain injury guideline (mBIG)

For adults with mild traumatic brain injury (GCS 13–15) and traumatic intracranial hemorrhage on CT (including acute SDH), the Modified brain injury guideline (mBIG) stratifies risk to guide neurosurgical consultation, ICU admission, and safe discharge:

Scope: mBIG applies ONLY to traumatic intracranial hemorrhage in adults with mild traumatic brain injury (GCS 13–15). It is not applicable to spontaneous/aneurysmal subarachnoid hemorrhage, spontaneous intracerebral hemorrhage, or any non-traumatic intracranial hemorrhage.

mBIG 1 (lowest risk)

All of the following must be true:

• GCS 15
• No loss of consciousness (LOC)
• No seizure
• No emesis
• Isolated SDH ≤4 mm, isolated EDH ≤4 mm, isolated tSAH ≤4 mm, cerebral contusion ≤2 cm, or intraventricular hemorrhage ≤2 mm
• No herniation or significant mass effect on CT
• Neurologically intact

Disposition: No neurosurgical consultation required; observation in non-monitored setting acceptable; repeat CT imaging not required if clinically stable; may be appropriate for discharge with reliable follow-up.

mBIG 2 (intermediate risk)

Meets any of the following (but does not meet mBIG 3 criteria):

• GCS 13–14, OR
• LOC, OR
• Isolated seizure, OR
• Emesis, OR
• CT findings larger than mBIG 1 thresholds but without herniation/significant mass effect

Disposition: Neurosurgical consultation warranted; admission to step-down or monitored unit; repeat head CT in 4–6 hours or per neurosurgical guidance.

mBIG 3 (highest risk)

Any of the following:

• GCS <13 (note: if GCS <13, patient may not strictly qualify as "mild TBI" — manage per moderate-to-severe traumatic brain injury pathway)
• Any herniation on CT
• Significant mass effect (midline shift >5 mm, cisternal effacement)
• Bilateral or mixed intracranial hemorrhage pattern with neurologic decline
• Neurovascular injury identified

Disposition: Emergent neurosurgical consultation; ICU admission; operative intervention frequently required.

See Also

• Epidural hemorrhage
• Head trauma (main)
• Traumatic subarachnoid hemorrhage
• Anticoagulation reversal
• Modified brain injury guideline (mBIG)