A 32-year-old man is brought to the trauma center after a motor vehicle collision with loss of consciousness. CT brain shows a lens-shaped hematoma that does not cross the midline and is confined between the skull and dura. What is the most common arterial source of this epidural hematoma?

Explanation

## Most Common Arterial Source of Epidural Hematoma **Key Point:** The middle meningeal artery (MMA) is the most common source of epidural hematoma, accounting for approximately 85–90% of cases. ### Anatomical Basis ```mermaid flowchart TD A[Head Trauma]:::urgent --> B{Location of fracture?}:::decision B -->|Temporal bone| C[Middle meningeal artery injury]:::outcome B -->|Parietal/occipital| D[Venous source or posterior MMA]:::outcome B -->|Frontal| E[Anterior meningeal artery]:::outcome C --> F[Epidural hematoma - lens shaped]:::outcome F --> G[Rapid accumulation - high mortality if untreated]:::urgent ``` ### Why Middle Meningeal Artery? 1. **Anatomical vulnerability:** - Runs in grooves along the inner table of the temporal bone - Relatively fixed course makes it susceptible to tearing with temporal fractures - High-pressure arterial source (unlike bridging veins) 2. **Fracture pattern:** - Temporal bone fractures are the most common site of epidural hematoma - MMA branches run directly beneath the temporal bone 3. **Clinical presentation:** - Rapid accumulation of blood (arterial pressure) - "Lucid interval" — initial unconsciousness, recovery, then rapid deterioration - Medical emergency requiring urgent surgical evacuation ### Distinguishing Features: Epidural vs Subdural | Feature | Epidural | Subdural | |---------|----------|----------| | **Vessel** | Middle meningeal artery (85–90%) | Bridging veins | | **Location** | Between skull and dura | Between dura and arachnoid | | **Shape** | Lens-shaped (biconvex) | Crescent-shaped | | **Crosses sutures?** | No (respects dural attachments) | Yes (crosses midline) | | **Trauma severity** | Usually significant | Often minor | | **Age group** | Young adults | Elderly, alcoholics | | **Onset** | Acute (hours) | Acute, subacute, or chronic | | **Lucid interval** | Classic (30–40% of cases) | Uncommon | | **Mortality** | High if untreated (5–10%) | Lower (2–5%) | **High-Yield:** The lens-shaped appearance that respects the dural attachments (does not cross suture lines) is the radiological hallmark of epidural hematoma and distinguishes it from subdural hematoma. **Mnemonic:** **EPIDURAL = Extra Dural = Arterial (MMA) = Lens-shaped = Emergency** **Clinical Pearl:** The "lucid interval" — initial loss of consciousness followed by apparent recovery, then rapid deterioration — is classic for epidural hematoma and represents the time lag between arterial bleeding and mass effect reaching critical threshold. This is a neurosurgical emergency. **Warning:** Do not confuse epidural (arterial, lens-shaped, respects sutures) with subdural (venous, crescent-shaped, crosses sutures). The imaging appearance is diagnostic. [cite:Harrison 21e Ch 445]