Hemorrhage Types by Compartment
| Type | Location | Key Features |
|---|---|---|
| Epidural | Epidural space | Biconvex (lenticular); crosses falx/tentorium but does NOT cross sutures; associated with temporal bone fracture and MMA injury |
| Subdural | Between dura and arachnoid | Crescent-shaped; crosses sutures but does NOT cross falx; bridging vein injury |
| Subarachnoid | Subarachnoid space | Follows cisterns and sulci; causes: aneurysm, trauma, AVM |
| Intraparenchymal | Brain parenchyma | Hypertensive pattern: basal ganglia, thalamus, pons, cerebellum; amyloid angiopathy: cortical/subcortical |
| Intraventricular | Ventricles | Often extension from parenchymal bleed; risk of obstructive hydrocephalus |
Blood Product Evolution on MRI
| Stage | Timing | T1 Signal | T2 Signal | Predominant Species |
|---|---|---|---|---|
| Hyperacute | <24h | Iso / ↓ | ↑ | Oxyhemoglobin |
| Acute | 1–3 days | Iso | ↓ | Deoxyhemoglobin |
| Early subacute | 3–7 days | ↑ | ↓ | Intracellular methemoglobin |
| Late subacute | 1–2 weeks | ↑ | ↑ | Extracellular methemoglobin |
| Chronic | Weeks–months | ↓ | ↓ | Hemosiderin |
The key practical rule: T2 hypointensity (dark) = deoxyhemoglobin (acute) or hemosiderin (chronic). T1 hyperintensity (bright) = methemoglobin (subacute). Hemosiderin persists indefinitely and is best seen on GRE/SWI sequences.
ABC/2 Volume Calculation
Used for intraparenchymal hemorrhage (IPH) volume estimation:
Volume (mL) = (A × B × C) ÷ 2
- A — longest diameter on the slice with largest hemorrhage (cm)
- B — diameter perpendicular to A on same slice (cm)
- C — number of slices with hemorrhage × slice thickness (cm)
Volume >30 mL is generally associated with worse prognosis. Volume >60 mL in the posterior fossa may indicate need for surgical decompression.
Reporting Checklist — Intracranial Hemorrhage
- Hemorrhage type: EDH / SDH / SAH / IPH / IVH (specify all present)
- Location: lobe / fossa / cistern / ventricle (be specific)
- Volume: ABC/2 method for IPH (report in mL)
- Midline shift: measure in mm, specify direction
- Herniation pattern: subfalcine / uncal / transtentorial / tonsillar / none
- Hydrocephalus: present / absent; obstructive vs communicating
- Effacement of basal cisterns: patent / partially effaced / obliterated
- Underlying lesion: AVM / tumor / cavernoma / aneurysm / none identified
- Prior hemorrhage or evolving change (compare to prior exam if available)