A 68-year-old man with hypertension presents to the emergency department 3 days after a fall from standing height at home. He complains of progressive headache and confusion. On examination, he is drowsy with a blood pressure of 160/95 mmHg and a right-sided hemiparesis. Non-contrast CT head shows a crescent-shaped hyperdensity along the cerebral convexity that crosses the midline. What is the most likely diagnosis?

Explanation

## Clinical Presentation & Imaging Features **Key Point:** The 3-day delay between trauma and symptom onset is a hallmark of subdural hematoma, particularly in elderly patients with cerebral atrophy and fragile bridging veins. **High-Yield:** The crescent-shaped (concave) hyperdensity that **crosses the midline** is pathognomonic for subdural hematoma. This occurs because subdural blood strips the dura from the brain surface and can extend across the falx cerebri. ## Pathophysiology Subdural hematomas result from tearing of **bridging veins** that traverse the subdural space. In elderly patients, brain atrophy increases the distance these veins must travel, making them more vulnerable to stretch injury even from minor trauma (e.g., standing fall). The venous bleeding is slow, allowing a lucid interval before mass effect develops. ## Imaging Characteristics: Subdural vs Epidural | Feature | Subdural Hematoma | Epidural Hematoma | |---------|-------------------|-------------------| | **Shape** | Crescent (concave) | Lens-shaped (convex) | | **Crosses midline** | Yes (crosses falx) | No (limited by dural attachments) | | **Crosses suture lines** | Yes | No (stops at suture lines) | | **Typical vessel injured** | Bridging veins | Middle meningeal artery | | **Onset of symptoms** | Delayed (hours to days) | Rapid (minutes to hours) | | **Age group** | Elderly, chronic alcoholics | Younger patients | | **Trauma severity** | Minor/trivial | Usually significant | | **Lucid interval** | Common | Characteristic | **Clinical Pearl:** Progressive deterioration over 3 days with initial lucidity is typical of subdural hematoma. Epidural hematoma presents acutely with rapid deterioration. ## Why This Patient Has Subdural Hematoma 1. **Age & mechanism:** Elderly patient with trivial trauma (standing fall) 2. **Timing:** 3-day delay before symptom progression 3. **Imaging:** Crescent shape crossing midline 4. **Hypertension:** Risk factor for bridging vein rupture **Mnemonic:** **SUBDURAL = Slow, Bridging veins, Delayed presentation, Crescent (concave), Crosses midline** ```mermaid flowchart TD A[Head trauma]:::outcome --> B{Age & mechanism?}:::decision B -->|Elderly, minor trauma| C[Bridging vein injury]:::outcome B -->|Young, severe trauma| D[Meningeal artery injury]:::outcome C --> E[Slow venous bleeding]:::outcome D --> F[Rapid arterial bleeding]:::outcome E --> G[Delayed symptoms<br/>hours to days]:::outcome F --> H[Acute symptoms<br/>minutes to hours]:::outcome G --> I[Crescent, crosses midline]:::outcome H --> J[Lens-shaped, respects sutures]:::outcome I --> K[Subdural hematoma]:::action J --> L[Epidural hematoma]:::action ```