A 32-year-old man is brought to the trauma centre 2 hours after a motor vehicle collision with severe head impact. He was initially conscious but rapidly deteriorated. On examination, he is comatose with a dilated right pupil and left hemiparesis. CT head (non-contrast) shows a lens-shaped hyperdense collection in the right frontoparietal region that does not cross the midline. The collection is bounded by the inner table of the skull and does not follow the brain contour. What is the most likely diagnosis?

Explanation

## Imaging Diagnosis: Epidural vs Subdural **Key Point:** The **lens-shaped (biconvex) morphology** and **failure to cross the midline** are pathognomonic for epidural hematoma. The collection is bounded by the inner table of the skull and dural attachments at suture lines. ## Comparative Imaging Features | Feature | Epidural Hematoma | Subdural Hematoma | |---------|-------------------|-------------------| | **Shape** | Lens-shaped (biconvex) | Crescent-shaped (concave to brain) | | **Crosses midline?** | No (respects suture lines) | Yes (follows brain surface) | | **Crosses suture lines?** | No (bounded by dura) | Yes (follows dural reflection) | | **Location** | Between skull and dura | Between dura and arachnoid | | **Typical vessel** | Middle meningeal artery (temporal) | Bridging veins | | **Density (acute)** | Hyperdense | Hyperdense | | **Age group** | Younger (firm dural adhesion) | Any age, elderly common | | **Symptom onset** | Rapid (hours) | Rapid (acute) or insidious (chronic) | ## Clinical Presentation: Uncal Herniation **High-Yield:** The **"talk and die" syndrome** is classic for epidural hematoma: 1. Initial loss of consciousness (impact) 2. **Lucid interval** (patient wakes up, seems fine) 3. Rapid deterioration (expanding hematoma compresses brain) 4. Coma and death if untreated This patient had **rapid deterioration within 2 hours**, consistent with acute epidural expansion. ## Signs of Uncal Herniation (Ipsilateral to Mass) 1. **Dilated ipsilateral pupil** (CN III compression) — **right pupil dilated** = right-sided mass ✓ 2. **Contralateral hemiparesis** (brainstem compression) — **left hemiparesis** = right-sided mass ✓ 3. **Coma** (midbrain compression) **Clinical Pearl:** The **ipsilateral dilated pupil + contralateral weakness** is the hallmark of uncal herniation from a unilateral supratentorial mass. ## Why Epidural, Not Subdural? ```mermaid flowchart TD A["Acute head trauma with rapid deterioration"]:::outcome --> B{"Shape on CT?"}:::decision B -->|"Lens-shaped, bounded by skull"|C["Epidural hematoma"]:::action B -->|"Crescent-shaped, follows brain"|D["Subdural hematoma"]:::action C --> E{"Crosses midline?"}:::decision D --> F{"Crosses midline?"}:::decision E -->|"No"|G["Confirm epidural"]:::outcome F -->|"Yes"|H["Confirm subdural"]:::outcome G --> I["Emergency burr hole/craniotomy"]:::action H --> I ``` **Mnemonic: EDH = **E**pidural = **D**ural-bounded = **H**igh-convexity (lens-shaped)** ## Management Epidural hematoma with uncal herniation is a **neurosurgical emergency** requiring immediate **burr hole evacuation** or **craniotomy**. Mortality without surgery approaches 100%; with urgent surgery, survival is > 80%.