A 68-year-old man with chronic alcoholism presents with a 3-week history of progressive headache, confusion, and gait disturbance following a minor head trauma he barely remembers. CT head shows a crescent-shaped hypodense collection over the cerebral convexity. Which of the following is NOT a characteristic feature of subdural hematoma?

Explanation

## Subdural vs Extradural Hematoma: Key Distinguishing Features ### Subdural Hematoma Characteristics **Key Point:** Subdural hematomas result from tearing of bridging veins that traverse the subdural space between the brain surface and dural venous sinuses. These are typically venous bleeds with slower accumulation. **High-Yield:** In elderly patients and chronic alcoholics, brain atrophy creates larger subdural spaces, allowing blood to accumulate slowly. This permits a **chronic subdural hematoma** to develop over weeks to months, often following trivial head trauma that the patient may not even recall. ### Why Option A Is Incorrect (NOT a feature of subdural hematoma) **Warning:** The statement "crosses the midline and extends across multiple lobes" is **NOT true** for subdural hematoma. Subdural hematomas are **limited by dural reflections** (falx cerebri, tentorium cerebelli). The falx cerebri acts as a barrier at the midline, preventing a unilateral subdural collection from crossing to the contralateral side. While subdural hematomas can cross cranial suture lines (unlike extradural hematomas), they **cannot cross the midline** due to the dural attachment of the falx. This is in contrast to extradural (epidural) hematomas, which are limited by cranial sutures but can, in rare cases, cross the midline if the dural attachment is disrupted. ### Temporal Classification of Subdural Hematoma | Timing | Presentation | CT Appearance | Clinical Context | |--------|--------------|---------------|------------------| | **Acute** | < 72 hours | Hyperdense | Severe trauma, rapid deterioration | | **Subacute** | 3–20 days | Isodense (mixed density) | Intermediate presentation | | **Chronic** | > 20 days | Hypodense | Trivial trauma, elderly/alcoholics | **Clinical Pearl:** The vignette describes a **chronic subdural hematoma** — the patient had minor trauma 3 weeks ago and now presents with insidious neurological decline. This is the classic presentation in elderly and alcoholic patients. ### Comparison: Extradural vs Subdural | Feature | Extradural | Subdural | |---------|-----------|----------| | **Vessel torn** | Middle meningeal artery (arterial) | Bridging veins (venous) | | **Shape on CT** | Lens-shaped (biconvex) | Crescent-shaped (concave) | | **Crosses sutures?** | No (limited by dural attachments at sutures) | Yes (crosses sutures freely) | | **Crosses midline?** | Rarely | **No** (limited by falx cerebri) | | **Typical onset** | Acute (hours) | Acute, subacute, or chronic | | **Lucid interval** | Common | Less common | | **Risk factors** | Young, severe trauma | Elderly, minor trauma, coagulopathy, alcoholism | **Mnemonic:** **BEAT** for Extradural — **B**iconvex (lens), **E**pidural location, **A**rterial (middle meningeal), **T**ypically acute. **Mnemonic:** **CRESCENT** for Subdural — **C**rescent shape, **R**ecurrent (chronic form), **E**lderly/alcoholics, **S**low venous bleed, **C**rosses sutures (not midline), **E**ncompasses ipsilateral hemisphere, **N**ot limited by sutures, **T**rivia can cause it. ### Clinical Pearls **High-Yield:** Chronic subdural hematoma is a **great imitator** — it can mimic dementia, Parkinson's disease, or stroke. Always ask about head trauma (even trivial) in elderly patients with insidious cognitive or motor decline. (Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.; Harrison's Principles of Internal Medicine, 21st ed.) **Tip:** On exam, remember that subdural hematomas are **NOT** limited by suture lines (they can spread freely over the hemisphere) but ARE limited by dural reflections such as the falx cerebri — so they do NOT cross the midline.