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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.