Traumatic subarachnoid hemorrhage

Subarachnoid hemorrhage caused by blunt or penetrating head trauma. For non-traumatic SAH, see Aneurysmal subarachnoid hemorrhage.

Background

• Bleeding into the subarachnoid space due to traumatic disruption of pial/cortical vessels
• Most common CT finding after moderate-to-severe traumatic brain injury and a frequent finding in mild traumatic brain injury with a positive head CT
• Mechanism: tearing of small subarachnoid/cortical vessels from acceleration–deceleration or direct impact; rarely from traumatic dissection or aneurysm rupture provoked by trauma
• Often co-exists with other intracranial injuries: cerebral contusion, traumatic intracerebral hemorrhage, subdural hemorrhage, epidural hemorrhage, diffuse axonal injury
• Isolated traumatic SAH (tSAH) in mild TBI generally has a benign course with low risk of neurosurgical intervention

Clinical Features

• History of head trauma (witnessed or suspected)
• Headache, nausea, vomiting
• Altered mental status proportional to severity of underlying TBI (GCS often 13–15 in isolated tSAH)
• Scalp injury, skull tenderness, signs of basilar skull fracture (Battle sign, raccoon eyes, hemotympanum, CSF oto-/rhinorrhea)
• Focal neurologic deficits if associated parenchymal injury
• Post-traumatic seizure
• Distinguishing from aneurysmal SAH: trauma history is key; if mechanism is unclear or syncope/collapse preceded the fall, consider aneurysmal subarachnoid hemorrhage as the inciting event

Differential Diagnosis

Head trauma

• Traumatic brain injury
  • Intracranial hemorrhage
    • Intra-axial
      • Traumatic intracerebral hemorrhage
    • Extra-axial
      • Epidural hemorrhage
      • Subdural hemorrhage
      • Subarachnoid hemorrhage
  • Moderate-to-severe traumatic brain injury
    • Elevated intracranial pressure
  • Mild traumatic brain injury
    • Clinical decision rules for head CT in trauma
    • Post-concussive syndrome
• Orbital trauma
• Maxillofacial trauma
• Scalp laceration
• Skull fracture
  • Basilar skull fracture
  • Skull fracture (peds)
• Pediatric head trauma
  • PECARN head trauma rule
• Aneurysmal subarachnoid hemorrhage (consider if collapse preceded the fall)
• Traumatic intracerebral hemorrhage
• Subdural hemorrhage
• Epidural hemorrhage
• Cerebral contusion
• Diffuse axonal injury
• Concussion

Evaluation

Non-Contrast CT Head

• First-line imaging for any patient meeting trauma head CT criteria (Canadian CT Head Rule, New Orleans Criteria, NEXUS II, PECARN for pediatrics)
• Hyperdense blood in sulci, fissures, or cisterns; convexity SAH most common in trauma (vs basal cisterns in aneurysmal SAH)
• Evaluate for associated injuries: contusion, ICH, SDH, EDH, skull fracture, midline shift, herniation

CT Angiography

• Consider if pattern is atypical for trauma (e.g., predominantly basal cistern blood), unclear mechanism, or to exclude blunt cerebrovascular injury per institutional protocol

Labs

• CBC, BMP, coagulation studies (PT/INR, PTT)
• Type and screen if surgical intervention possible
• Consider ethanol/toxicology if altered

Management

ED Management

• ABCs, c-spine precautions, full trauma evaluation
• Avoid hypoxia (SpO₂ ≥90%) and hypotension (SBP ≥90–110 mmHg by age) — secondary insults worsen outcomes
• Reverse anticoagulation/antiplatelet agents per anticoagulation reversal protocols
• Treat elevated intracranial pressure if signs of herniation: head of bed 30°, hyperosmolar therapy (hypertonic saline or mannitol), brief hyperventilation as bridge
• Seizure: treat with benzodiazepines acutely; levetiracetam for early post-traumatic seizure prophylaxis in moderate-severe TBI
• Analgesia: acetaminophen; avoid NSAIDs/ketorolac
• Nimodipine is NOT routinely indicated for traumatic SAH (in contrast to aneurysmal SAH)
• Tranexamic acid within 3 hours of injury for moderate TBI (GCS 9–15) per CRASH-3

Disposition

• Neurosurgical consultation for any traumatic intracranial hemorrhage at non-trauma centers; transfer per local protocol
• Repeat head CT generally at 6 hours (or sooner if neurologic change) for traumatic ICH
• Risk-stratification of mild TBI with isolated tSAH may use the Modified brain injury guideline (mBIG) to guide neurosurgical consultation, repeat imaging, and admission level

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

• Subarachnoid hemorrhage
• Aneurysmal subarachnoid hemorrhage
• Head trauma
• Traumatic brain injury
• Mild traumatic brain injury
• Traumatic intracerebral hemorrhage
• Subdural hemorrhage
• Epidural hemorrhage
• Cerebral contusion
• Diffuse axonal injury
• Modified brain injury guideline (mBIG)