Subdural Hematoma

Understanding Subdural Hematoma

A subdural hematoma (SDH) is bleeding between the brain and its outer covering (dura mater), usually caused by head trauma. Before we examine how this condition appears on imaging, let's understand why prompt evaluation is critical.

Here's how accurate non-contrast CT is at detecting subdural hematomas:

Think of a subdural hematoma like a bruise between the layers of your skull—when veins bridging the brain surface tear, blood accumulates and can press on the brain. Like a bruise, the appearance changes over time as blood breaks down.

What Is a Subdural Hematoma?

Subdural hematoma is bleeding into the subdural space, between the dura mater (outer membrane) and arachnoid mater (middle membrane) surrounding the brain. This usually results from tearing of bridging veins.

Common causes:

| Type | Timeframe | Typical Cause | |------|-----------|---------------| | Acute SDH | 0-3 days | Head trauma, falls, assault | | Subacute SDH | 4-21 days | Evolving from acute, or delayed presentation | | Chronic SDH | 21+ days | Minor trauma (often forgotten), anticoagulation |

Why CT is essential:

• Rapid diagnosis in trauma setting
• Determines size and mass effect
• Guides surgical vs. medical management
• Detects underlying brain injury
• No contraindications (unlike MRI)

How SDH Appears on CT

Non-contrast CT of the head is the first-line imaging test for suspected subdural hematoma. The appearance changes predictably over time as blood breaks down.

Key Findings Pattern

When evaluating for subdural hematoma on CT, radiologists assess specific critical features:

When Your Doctor Orders This Test

Here's a typical scenario where urgent head CT is ordered for suspected subdural hematoma:

Common presenting symptoms:

• Headache (often persistent)
• Confusion or altered mental status
• Focal neurological deficit (weakness, speech difficulty)
• Decreased consciousness
• Seizures (in some cases)

Red flags requiring urgent evaluation:

• Rapidly declining mental status
• Unequal pupil size (anisocoria)
• Posturing (decorticate/decerebrate)
• Herniation signs

Differential Diagnosis

Several conditions can mimic or complicate subdural hematoma:

How Accurate Is CT for Subdural Hematoma?

Non-contrast CT is the gold standard for initial evaluation:

What Happens Next?

Management depends on size, symptoms, and neurological status:

Frequently Asked Questions

What's the difference between subdural and epidural hematoma?

Subdural hematoma is bleeding between the brain and dura (crescent-shaped, crosses sutures). Epidural hematoma is bleeding between dura and skull (lens-shaped, doesn't cross sutures). Epidural is usually arterial (rapid expansion), while subdural is venous (slower). Both can be life-threatening.

How long does it take to recover?

Recovery varies greatly. Small SDHs without surgery: weeks to months. Surgical cases: months of rehabilitation. Residual deficits (headache, cognitive changes, weakness) may persist. Chronic SDH patients often have good recovery with drainage.

Will I need surgery?

Not necessarily. Small SDHs without significant mass effect or neurological decline can be managed with observation and medical management (reversing anticoagulation, monitoring). Surgery is needed for: large SDHs causing shift, neurological deterioration, or failure to improve with medical management.

Can subdural hematoma recur?

Yes, especially with chronic SDH. Recurrence rate after drainage is approximately 10-20%. Risk factors include: brain atrophy, continued anticoagulation, inadequate drainage, and bleeding diathesis. Close monitoring and repeat imaging are important.

How can I prevent subdural hematoma?

Primary prevention: prevent head trauma (fall precautions, wear helmets, avoid risky activities). If on anticoagulation: use caution, regular monitoring, consider falls risk. For elderly: home safety modifications, vision checks, medication review (reduce sedating drugs). Address alcohol abuse if present.

References

Medical Disclaimer: This information is for educational purposes. Subdural hematoma can be a life-threatening emergency requiring immediate neurosurgical evaluation.