A 32-year-old man is brought to the emergency department 2 hours after a motor vehicle accident with a severe blow to the left temporal region. On examination, he is drowsy (GCS 13), has a left-sided dilated pupil (7 mm), and shows weakness of the right limbs. A CT head is ordered. Which of the following is the MOST likely diagnosis based on the clinical presentation?

Explanation

## Clinical Diagnosis: Acute Epidural Hematoma ### Key Clinical Features **Key Point:** The classic triad of acute epidural hematoma is: 1. Temporal bone injury (mechanism) 2. Ipsilateral dilated pupil (blown pupil due to CN III compression) 3. Contralateral motor weakness (from uncal herniation compressing the cerebral peduncle) ### Mechanism & Pathophysiology Acute epidural hematoma results from **tearing of the middle meningeal artery** (or its branches) as it runs in grooves along the inner surface of the temporal bone. The hematoma accumulates between the dura mater and the inner table of the skull. ```mermaid flowchart TD A[Temporal bone trauma]:::outcome --> B[Laceration of middle meningeal artery]:::outcome B --> C[Arterial bleeding in epidural space]:::outcome C --> D[Mass effect on brain]:::outcome D --> E{Uncal herniation?}:::decision E -->|Yes| F[Ipsilateral pupil dilation<br/>CN III compression]:::urgent E -->|Yes| G[Contralateral motor weakness<br/>Cerebral peduncle compression]:::urgent E -->|Yes| H[Brainstem signs<br/>Deterioration]:::urgent ``` ### Why This Case Fits Epidural Hematoma 1. **Temporal location**: Blow to left temporal region → classic site for middle meningeal artery injury 2. **Ipsilateral blown pupil (7 mm)**: Indicates uncal herniation with compression of the oculomotor nerve (CN III) on the same side 3. **Contralateral motor weakness**: Right-sided weakness with left-sided lesion = compression of left cerebral peduncle as the uncus herniates medially 4. **Lucid interval**: Patient was conscious enough to be brought to ED (typical of epidural — often a period of relative stability before rapid deterioration) 5. **GCS 13**: Mild-to-moderate depression of consciousness, consistent with early herniation ### Imaging Characteristics **High-Yield:** On CT head, acute epidural hematoma shows: - **Lens-shaped (biconvex) collection** between skull and dura - Hyperdense (acute blood) - Does NOT cross suture lines (because dura is adherent to bone at sutures) - Often associated with skull fracture (especially temporal) ### Management Principle Acute epidural hematoma with signs of herniation (blown pupil, motor deficit) is a **neurosurgical emergency** requiring **immediate craniotomy and evacuation**. Mortality is high if herniation is allowed to progress. **Clinical Pearl:** The "talk and die" syndrome is classically associated with epidural hematoma — patient may be initially conscious, then deteriorate rapidly if not evacuated urgently. [cite:Harrison 21e Ch 434]