A 35-year-old man is brought to the emergency department 2 hours after a high-speed motor vehicle collision with loss of consciousness at the scene. He is now alert but restless. Blood pressure is 145/92 mmHg, heart rate 110/min. A linear skull fracture is noted over the left temporal bone. Non-contrast CT head shows a lens-shaped hyperdense collection between the skull and dura on the left side that does NOT cross the midline. The collection measures 8 mm at its thickest point. What is the most likely diagnosis and the immediate next step?

Explanation

## Clinical Presentation & Imaging Correlation **Key Point:** The lens-shaped (biconvex) hyperdense collection that does NOT cross the midline, in the setting of significant trauma and a skull fracture, is diagnostic of acute epidural hematoma. The 8 mm thickness and presence of mass effect (restlessness, tachycardia) mandate urgent surgical evacuation. ## Epidural Hematoma: Pathophysiology & Imaging ### Mechanism 1. High-impact trauma → skull fracture (especially temporal bone) 2. Tearing of middle meningeal artery (or its branches) 3. Arterial bleeding accumulates between skull and dura 4. Dura is adherent to skull at falx and tentorium → collection does NOT cross midline ### Imaging Features - **Shape:** Lens-shaped or biconvex (convex inner margin) - **Density:** Hyperdense on non-contrast CT - **Location:** Follows arterial distribution (usually temporal) - **Midline crossing:** NO (respects dural attachments) - **Associated findings:** Skull fracture (70–80% of cases) **High-Yield:** The lens shape is the key distinguishing feature. Think of a lens sitting between the skull and brain — it cannot spread beyond where the dura is adherent (falx, tentorium). ## Clinical Course: The Lucid Interval ```mermaid flowchart TD A[Head trauma + LOC]:::outcome --> B[Brief lucid interval<br/>patient appears well]:::outcome B --> C{Epidural hematoma<br/>expanding?}:::decision C -->|Yes| D[Rapid deterioration<br/>headache, confusion,<br/>pupillary changes]:::urgent D --> E[Herniation risk]:::urgent E --> F[EMERGENCY:<br/>Surgical evacuation]:::action C -->|No| G[Stable or slow expansion]:::outcome G --> H[Serial CT monitoring]:::action ``` **Clinical Pearl:** The classic lucid interval (50–80% of epidural cases) occurs because arterial bleeding is initially contained by the dura. As pressure rises, the patient deteriorates rapidly — this is a neurosurgical emergency. ## Management Thresholds for Epidural Hematoma | Criterion | Management | |-----------|-------------| | **Thickness >30 mm** | Surgical evacuation (regardless of GCS) | | **Midline shift >5 mm** | Surgical evacuation | | **GCS <9** | Surgical evacuation | | **Thickness 10–30 mm + GCS ≥9 + no midline shift** | Consider conservative management with serial CT (4–6 hourly) | | **Thickness <10 mm + GCS ≥9 + no midline shift** | Conservative management with serial CT | **In this case:** 8 mm collection, but patient is restless (early deterioration), tachycardic (sympathetic response to increased ICP), and has significant trauma. The risk of rapid expansion is high → **surgical evacuation is indicated**. ## Subdural vs Epidural: Quick Discriminator | Feature | Epidural | Subdural | |---------|----------|----------| | **Vessel torn** | Middle meningeal artery | Bridging veins | | **Shape** | Lens-shaped (biconvex) | Crescent-shaped (concave) | | **Crosses midline** | NO | YES | | **Skull fracture** | 70–80% | 20–30% | | **Lucid interval** | Classic (50–80%) | Rare | | **Presentation** | Acute (hours) | Acute, subacute, or chronic | | **Age group** | Younger (dura adherent) | Elderly (brain atrophy) | **Mnemonic:** **ELAND** = **E**pidural = **L**ens-shaped, **A**rterial, **N**o midline crossing, **D**ural adherence respects falx. [cite:Robbins 10e Ch 28; Neuroradiology: The Essentials Ch 3]