A 35-year-old man is brought to the emergency department after a motor vehicle collision. He was initially alert and conversant at the scene. Within 30 minutes, he developed severe headache, vomiting, and loss of consciousness. On examination, he has a right temporal hematoma, right-sided hemiparesis, and a fixed dilated right pupil. CT head shows a lens-shaped hyperdense collection in the right temporal region that does not cross the midline but respects the suture lines. What is the most likely diagnosis?

Explanation

## Classic Presentation of Epidural Hematoma This case exemplifies the **'talk-and-die' syndrome**—a pathognomonic presentation of acute epidural hematoma (aEDH) characterized by a lucid interval followed by rapid neurological deterioration. ### Diagnostic Features | Feature | This Case | Epidural Hematoma Signature | |---------|-----------|-----------------------------| | **Mechanism** | Motor vehicle collision (blunt trauma) | Tearing of middle meningeal artery (MMA) | | **Onset** | Lucid → loss of consciousness in 30 min | Rapid (minutes to hours) | | **Imaging shape** | Lens-shaped (convex) | Convex, respects suture lines | | **Location** | Temporal region | Temporal (MMA territory) | | **Pupillary sign** | Fixed dilated right pupil (ipsilateral) | Uncal herniation from mass effect | | **Hemiparesis** | Right-sided (contralateral to lesion) | From brainstem compression | **Key Point:** The **lens-shaped (convex)** collection that **respects suture lines** is the hallmark of epidural hematoma. The dura is tethered to the inner table of the skull at suture lines, preventing the hematoma from crossing them. ### Pathophysiology: Why the Rapid Deterioration? 1. **Arterial bleeding** (middle meningeal artery) → high-pressure system 2. Rapid accumulation of blood between dura and inner table of skull 3. Mass effect compresses brain tissue 4. Uncal herniation → ipsilateral CN III palsy (dilated pupil) 5. Brainstem compression → contralateral hemiparesis and loss of consciousness **Mnemonic: LUCID INTERVAL** — **L**oss of consciousness → **U**ncal herniation → **C**ranial nerve III palsy → **I**ncreased intracranial pressure → **D**eteriorating consciousness. ### Clinical Pearl: The Temporal Location The **temporal region** is the most common site for epidural hematoma because the middle meningeal artery runs in grooves along the inner table of the temporal bone. Trauma to the temporal region (e.g., from a motor vehicle collision striking the side of the head) tears the MMA, leading to rapid epidural bleeding. **High-Yield:** The **30-minute interval** from alert to unconscious is classic for epidural hematoma. In subdural hematoma, deterioration is slower (hours to days) because bleeding is venous (low-pressure). ### Why Uncal Herniation Occurs The expanding epidural mass displaces the brain medially, forcing the uncus of the temporal lobe through the tentorial notch. This compresses the ipsilateral oculomotor nerve (CN III), causing pupillary dilation and loss of accommodation on the side of the hematoma.