Subdural Hematoma (SDH)

A subdural hematoma (SDH) is a collection of blood between the dura mater and the arachnoid mater, which are layers of the meninges covering the brain. It usually results from a head injury causing tears in the veins that bridge the cerebral cortex and the dura.

This bleeding leads to the accumulation of blood within the subdural space, which can compress the brain tissue and increase intracranial pressure.

Types of Subdural Hematoma

1. Acute Subdural Hematoma:
   • Occurs within 72 hours of head trauma.
   • Typically results from severe head injury, causing rapid bleeding and neurological deterioration.
   • High morbidity and mortality rate if not promptly treated.
2. Subacute Subdural Hematoma:
   • Develops between 3 days and 2 weeks after the initial injury.
   • Bleeding is slower than in the acute type, but still requires medical intervention.
   • Symptoms can gradually worsen over days to weeks.
3. Chronic Subdural Hematoma:
   • Occurs more than 2 weeks after the initial head injury.
   • More common in older adults, particularly those with brain atrophy, or in people on anticoagulant therapy.
   • Symptoms develop slowly and can mimic other conditions such as dementia or stroke.

Pathophysiology

Subdural hematomas are often caused by damage to the bridging veins that traverse the subdural space. When these veins tear, blood accumulates and can compress the underlying brain tissue. The severity of symptoms depends on the rate of bleeding, the size of the hematoma, and the patient’s ability to compensate for the increased intracranial pressure. In chronic subdural hematomas, blood may undergo liquefaction over time, leading to osmotic fluid shifts that further expand the hematoma.

Risk Factors

• Age: Older adults are at higher risk due to brain atrophy, which increases the tension on bridging veins.
• Anticoagulation Therapy: Use of blood thinners (e.g., warfarin, aspirin) increases bleeding risk.
• Alcohol Abuse: Chronic alcoholics have a higher incidence due to frequent falls and associated brain atrophy.
• Head Trauma: Direct trauma to the head, especially from falls, assaults, or motor vehicle accidents.
• Medical Conditions: Disorders like coagulopathies, epilepsy, or a history of previous head injuries.

Clinical Features

Symptoms of subdural hematoma vary depending on the type:

1. Acute Subdural Hematoma:
   • Sudden onset of headache.
   • Altered level of consciousness (confusion, drowsiness, or coma).
   • Focal neurological deficits such as weakness, numbness, or slurred speech.
   • Seizures.
   • Signs of increased intracranial pressure (ICP), including vomiting, papilledema, or pupil dilation.
2. Subacute Subdural Hematoma:
   • Gradually worsening headache.
   • Drowsiness or confusion.
   • Mild neurological deficits that progressively worsen.
3. Chronic Subdural Hematoma:
   • Insidious onset of symptoms, often mistaken for other conditions like dementia or stroke.
   • Progressive headache.
   • Cognitive changes such as memory loss, confusion, or apathy.
   • Weakness or difficulty walking.
   • Behavioral changes, including irritability or personality changes.

Diagnostic Evaluation

1. History and Physical Examination:
   • Obtain a detailed history of head trauma, anticoagulant use, or symptoms indicative of increased ICP.
   • Perform a neurological exam to assess for any deficits.
2. Imaging Studies:
   • Non-Contrast Head CT Scan: The preferred initial imaging modality. It can reveal a crescent-shaped, hyperdense (acute) or hypodense (chronic) lesion along the brain’s convexity.
   • Magnetic Resonance Imaging (MRI): Provides more detailed imaging, especially for subacute or small chronic subdural hematomas.
3. Additional Tests:
   • Coagulation Profile: Evaluate if the patient is on anticoagulants or has coagulopathies.
   • Electrolytes and Complete Blood Count (CBC): To assess for other contributing factors, such as anemia.

Management

Treatment of subdural hematoma depends on the size, type, symptoms, and patient’s overall health:

1. Acute Subdural Hematoma:
   • Emergency Surgery: Indicated for large hematomas causing significant mass effect or neurological decline. The most common procedures include:
     • Craniotomy: Surgical removal of the hematoma via a bone flap, allowing direct access to the bleed.
     • Burr Hole Evacuation: Involves drilling small holes in the skull to drain the hematoma, typically used for smaller collections.
   • Medical Management: Stabilization of the patient’s airway, breathing, and circulation (ABCs). Administer intravenous mannitol or hypertonic saline to reduce intracranial pressure.
2. Subacute Subdural Hematoma:
   • Monitoring: In asymptomatic or minimally symptomatic cases, serial imaging may be done to monitor for changes in size.
   • Surgical Intervention: Consider surgery if the hematoma enlarges or symptoms worsen.
3. Chronic Subdural Hematoma:
   • Burr Hole Evacuation: Often the treatment of choice, as chronic hematomas are typically more liquefied and can be drained easily.
   • Non-Surgical Management: In some cases, especially with small hematomas and minimal symptoms, close observation with regular imaging can be sufficient.
4. Supportive Care:
   • Anticoagulant Reversal: If the patient is on anticoagulants, reversal agents (e.g., vitamin K, fresh frozen plasma) should be administered.
   • Seizure Prophylaxis: Considered in cases with cortical irritation, as seizures are more likely in patients with significant brain compression.
   • ICU Monitoring: Patients with significant head trauma or elevated ICP may require intensive care monitoring.

Complications

• Increased Intracranial Pressure: Can lead to brain herniation and death if not managed promptly.
• Rebleeding: More common in chronic subdural hematoma, necessitating repeat surgery.
• Seizures: Due to cortical irritation from the hematoma.
• Cognitive Impairment: Long-term neurological deficits or cognitive decline, especially in older adults.

Prognosis

• Acute Subdural Hematoma: Has a poor prognosis if not treated promptly. Mortality rates are high, particularly in cases of severe head injury.
• Chronic Subdural Hematoma: Prognosis is generally better with appropriate management, though some patients may experience long-term neurological issues.
• Factors Influencing Outcome: Age, comorbid conditions, the extent of the hematoma, time to treatment, and initial neurological status.

Follow-Up and Rehabilitation

• Regular Imaging: Follow-up CT scans or MRIs to monitor for recurrence or resolution.
• Physical Therapy: For patients with neurological deficits.
• Cognitive Rehabilitation: May be needed for those with cognitive impairments.
• Monitoring for Recurrent Hematoma: Particularly important in older adults and those with ongoing risk factors like anticoagulation.