## Extradural Hematoma: Anatomy and Most Common Site **Key Point:** The **temporal region** is the most common site of extradural hematoma (EDH), accounting for 50–70% of cases, due to injury to the **middle meningeal artery (MMA)** — the dominant source of bleeding in the epidural space. ### Vascular Anatomy of the Epidural Space | Artery | Location | Frequency of EDH | |--------|----------|------------------| | **Middle meningeal artery (MMA)** | Temporal region, grooves in temporal bone | **50–70%** (most common) | | Anterior meningeal artery | Frontal region | ~15% | | Posterior meningeal artery | Occipital/posterior fossa | ~10% | | Dural venous sinuses | Midline (superior sagittal sinus) | ~5% | ### Why the Temporal Region? 1. **Vulnerable anatomy:** The MMA runs in grooves along the inner surface of the temporal bone; these grooves are easily fractured by blunt trauma. 2. **High-pressure arterial source:** The MMA is a branch of the external carotid artery — high-pressure bleeding accumulates rapidly in the epidural space. 3. **Mechanism:** Temporal bone fractures (especially linear fractures crossing the MMA groove) lacerate the artery, causing acute arterial bleeding. **Clinical Pearl:** Extradural hematoma classically presents with the **"talk and die" syndrome** — initial loss of consciousness, followed by a lucid interval (patient talks and appears well), then rapid deterioration as the hematoma expands and causes uncal herniation. This is a neurosurgical emergency requiring urgent evacuation. ### Imaging Features of EDH - **Shape:** Lens-shaped (biconvex) — bounded by dural attachments - **Density:** Hyperdense (acute blood) - **Location:** Follows the dura; does NOT cross the midline (unlike subdural, which can cross) - **Borders:** Sharp, well-demarcated **High-Yield:** **Lens-shaped = Extradural; Crescent-shaped = Subdural.** This is the single most important radiological distinction on exam. **Mnemonic:** **MMA-TED** = **M**iddle **M**eningeal **A**rtery → **T**emporal **E**xtradural **D**ural hematoma. ### Why Not the Other Sites? - **Frontal region (anterior cerebral artery):** Anterior meningeal artery is smaller and less frequently injured; accounts for only ~15% of EDH. - **Occipital region (posterior cerebral artery):** Posterior meningeal artery is small; posterior fossa EDH is rare (~10%) and usually from venous sources. - **Parietal region (superior sagittal sinus):** Venous bleeding is slower and less likely to cause acute EDH; accounts for only ~5% of cases.
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