Subdural Hematoma: Symptoms, Causes & Emergency Treatment

What Is a Subdural Hematoma?

A subdural hematoma is a collection of blood that forms between the brain and the protective membrane (dura mater) that covers it. This bleeding typically results from torn bridging veins and creates pressure on the brain, leading to neurological symptoms. The condition can be life-threatening if not promptly diagnosed and treated.

The brain is surrounded by three protective layers called meninges. The outermost layer, the dura mater, sits directly beneath the skull. A subdural hematoma occurs when blood accumulates in the space between the dura mater and the next layer (arachnoid mater), creating a blood clot that presses against the brain tissue. This pressure can disrupt normal brain function and, in severe cases, cause permanent brain damage or death.

Unlike an epidural hematoma, which occurs between the skull and the dura mater and is typically caused by arterial bleeding, subdural hematomas usually result from venous bleeding. The veins that bridge between the brain surface and the dural sinuses are particularly vulnerable to tearing during head trauma. Because venous blood flows more slowly than arterial blood, subdural hematomas may develop gradually, especially in chronic cases.

The condition affects approximately 1-5.3 people per 100,000 annually, with incidence increasing significantly in those over 65 years of age. This age-related increase occurs because the brain naturally shrinks with age, stretching the bridging veins and making them more susceptible to injury. Additionally, older adults are more likely to take blood-thinning medications, which increase bleeding risk.

Acute vs. Chronic Subdural Hematoma

Subdural hematomas are classified based on how quickly symptoms develop after the initial injury. Understanding this distinction is crucial because it affects both the urgency of treatment and the likely outcomes.

Acute subdural hematoma develops within 72 hours of a significant head injury, such as a car accident, fall from height, or assault. Symptoms appear rapidly and can progress quickly to unconsciousness. This form is considered a neurosurgical emergency and often requires immediate surgical intervention. Acute SDH has higher mortality rates due to the severe underlying brain injury often associated with it.

Chronic subdural hematoma develops over weeks to months, often following minor head trauma that may go unnoticed or be forgotten by the patient. The blood accumulates slowly, and the body may partially break down older blood while new bleeding continues. Symptoms are typically milder initially but progressively worsen. Chronic SDH is more common in elderly patients and has a better prognosis when properly treated.

A third category, subacute subdural hematoma, describes bleeding that becomes symptomatic between 3 days and 3 weeks after injury. This intermediate form shares characteristics of both acute and chronic presentations.

What Are the Symptoms of Subdural Hematoma?

Subdural hematoma symptoms include persistent headache, confusion, drowsiness, personality changes, weakness on one side of the body, slurred speech, and in severe cases, seizures and loss of consciousness. Symptoms may appear immediately after injury or develop gradually over weeks.

The symptoms of subdural hematoma vary considerably depending on whether the condition is acute or chronic, the size of the blood collection, and the rate at which it is expanding. Understanding these warning signs is critical for seeking timely medical care, as early intervention significantly improves outcomes.

In acute subdural hematoma, symptoms typically develop rapidly after the head injury. The patient may initially lose consciousness at the time of injury, then temporarily recover (a "lucid interval"), before deteriorating again as the hematoma expands. This pattern, while not universal, is a classic presentation that requires immediate emergency evaluation.

In chronic subdural hematoma, symptoms develop insidiously over weeks to months. Patients and family members may attribute early symptoms to normal aging, depression, or dementia, which can delay diagnosis. The gradual onset often means the hematoma has grown quite large by the time medical attention is sought.

Common Signs and Symptoms

• Headache: Often persistent and worsening, may not respond well to typical pain relievers. In chronic SDH, headaches may be mild initially but progressively intensify
• Confusion and disorientation: Difficulty with memory, concentration, and processing information. May appear similar to dementia in elderly patients
• Drowsiness and fatigue: Excessive sleepiness, difficulty staying awake, or unusual tiredness that doesn't improve with rest
• Nausea and vomiting: Particularly concerning if it begins or worsens hours to days after head injury
• Weakness on one side: Hemiparesis affecting arm, leg, or face on one side of the body due to pressure on motor areas
• Speech difficulties: Slurred speech, difficulty finding words, or problems understanding spoken language
• Personality or behavioral changes: Irritability, apathy, inappropriate behavior, or mood swings
• Seizures: Convulsions or unusual movements, which may occur as brain tissue becomes irritated
• Visual disturbances: Double vision, blurred vision, or unequal pupil sizes
• Loss of consciousness: Ranges from brief episodes to prolonged coma in severe cases

Symptoms in Elderly Patients

Subdural hematomas present particular diagnostic challenges in elderly patients because symptoms often mimic other common conditions. Cognitive changes may be attributed to dementia, balance problems to general frailty, and fatigue to depression or medication effects. Healthcare providers should maintain a high index of suspicion for subdural hematoma in any elderly patient with progressive neurological symptoms, even without clear history of head trauma.

Additionally, elderly patients may not recall minor head injuries that occurred weeks earlier. A seemingly insignificant bump to the head or minor fall can trigger chronic subdural bleeding in someone with age-related brain atrophy or those taking anticoagulant medications.

What Causes Subdural Hematoma?

Subdural hematoma is primarily caused by head trauma that tears the bridging veins between the brain and the dura mater. In elderly patients, even minor bumps can cause bleeding due to age-related brain shrinkage. Other causes include blood-thinning medications, alcohol abuse, and rarely, spontaneous bleeding without trauma.

The underlying mechanism of subdural hematoma involves damage to the veins that bridge between the brain's surface and the venous sinuses within the dura mater. When the head experiences sudden acceleration or deceleration forces, these bridging veins can stretch and tear. Because the brain floats within cerebrospinal fluid, it moves slightly within the skull during impact, putting strain on these connecting vessels.

The severity of trauma needed to cause subdural bleeding varies significantly between individuals. Young healthy adults typically require substantial force, such as that experienced in motor vehicle accidents or significant falls. In contrast, elderly individuals with brain atrophy may develop subdural hematomas from seemingly trivial impacts that they might not even remember.

Major Risk Factors

Advanced Age: As we age, the brain undergoes a natural shrinking process called cerebral atrophy. This shrinkage increases the distance between the brain surface and the skull, stretching the bridging veins and making them more vulnerable to tearing. Studies show that the incidence of subdural hematoma increases dramatically after age 65, with some research suggesting rates 7-10 times higher in those over 70 compared to younger adults.

Blood-Thinning Medications: Anticoagulants (such as warfarin, apixaban, rivaroxaban) and antiplatelet drugs (such as aspirin, clopidogrel) significantly increase the risk of subdural hematoma and its severity. These medications impair the blood's ability to clot, allowing even small tears to bleed more extensively. Patients on these medications should be especially vigilant about head injuries and should seek medical evaluation promptly after any impact.

Alcohol Use Disorder: Chronic heavy alcohol consumption increases subdural hematoma risk through multiple mechanisms: it causes brain atrophy (similar to aging), impairs liver function which affects blood clotting, and increases the likelihood of falls. Additionally, intoxicated individuals may not accurately recall head injuries or may dismiss symptoms as hangover effects.

History of Falls: Recurrent falls, common in elderly populations and those with balance disorders, create cumulative risk. Each head impact, even if minor, can cause microscopic damage to bridging veins that may eventually lead to symptomatic bleeding.

Less Common Causes

While trauma accounts for the vast majority of subdural hematomas, several other conditions can lead to this type of bleeding:

• Coagulation disorders: Inherited or acquired conditions affecting blood clotting, including hemophilia and liver disease
• Intracranial hypotension: Low cerebrospinal fluid pressure, often from spinal procedures or spontaneous CSF leaks
• Cerebrospinal fluid shunts: Devices used to drain excess CSF can overdrain, increasing subdural space
• Brain tumors: Some tumors can bleed into the subdural space
• Vascular malformations: Abnormal blood vessel formations that are prone to bleeding

When Should You Seek Emergency Medical Care?

Seek emergency medical care immediately if you experience loss of consciousness, severe worsening headache, repeated vomiting, confusion, weakness on one side, seizures, or progressive drowsiness after any head injury. Those on blood thinners should be evaluated after any head impact.

Recognizing when subdural hematoma symptoms require emergency attention can be life-saving. While not every bump to the head leads to serious bleeding, certain warning signs indicate the need for urgent medical evaluation. The challenge lies in distinguishing concerning symptoms from normal post-injury discomfort, particularly in the hours and days following head trauma.

The decision to seek emergency care should be influenced by both the severity of symptoms and the presence of risk factors. Someone taking anticoagulant medication who sustains even a minor head injury should have a lower threshold for seeking evaluation compared to a young healthy individual with the same injury.

Immediate Emergency Situations

Call your local emergency number or go to the emergency room immediately if any of the following occur after a head injury:

• Loss of consciousness: Even brief unconsciousness at the time of injury or afterward warrants emergency evaluation
• Worsening condition: Symptoms that progressively worsen over hours, such as increasing headache, growing confusion, or deepening drowsiness
• Repeated vomiting: Multiple episodes of nausea and vomiting, especially beginning hours after injury
• Seizures: Any convulsive activity or unusual movements following head trauma
• Clear fluid from nose or ears: May indicate skull fracture with CSF leak
• Raccoon eyes or Battle's sign: Bruising around both eyes or behind the ears, which may take a day to appear
• Unequal pupils: One pupil larger than the other, especially if not responding normally to light
• One-sided weakness: Difficulty moving arm or leg on one side, facial drooping
• Slurred or incoherent speech: Difficulty speaking clearly or making sense

When to Seek Urgent (Non-Emergency) Care

Contact your healthcare provider or visit an urgent care facility if you experience the following symptoms more than a week after a head injury:

• Persistent mild headache that doesn't improve
• Increased fatigue or difficulty concentrating
• Mild dizziness or balance problems
• Memory difficulties not present before the injury
• Mood changes or irritability

How Is Subdural Hematoma Diagnosed?

Subdural hematoma is primarily diagnosed using CT (computed tomography) scan, which can rapidly visualize blood collections within the skull. MRI may be used for chronic or small hematomas. Diagnosis also involves neurological examination to assess consciousness, pupil response, motor function, and speech.

The diagnosis of subdural hematoma relies on a combination of clinical assessment and imaging studies. When a patient presents with symptoms suggestive of intracranial bleeding, the diagnostic process must be efficient, as delays in identifying and treating subdural hematomas can result in permanent neurological damage or death.

Emergency physicians and neurologists use standardized assessment tools, such as the Glasgow Coma Scale (GCS), to evaluate consciousness levels and track changes over time. This 15-point scale assesses eye opening, verbal responses, and motor responses, providing an objective measure that can be communicated between healthcare providers and monitored for deterioration.

CT Scan (Computed Tomography)

CT scanning is the gold standard for diagnosing subdural hematoma in emergency settings. This imaging technique uses X-rays to create detailed cross-sectional images of the brain and skull. A CT scan can be completed in minutes, making it ideal for urgent situations where rapid diagnosis is essential.

On CT images, acute subdural hematomas appear as bright (hyperdense) crescent-shaped collections along the inner surface of the skull. As blood ages over days to weeks, it transitions through various densities—becoming isodense (same density as brain) and eventually hypodense (darker) in chronic hematomas. This progression helps clinicians estimate the age of bleeding and differentiate between acute and chronic presentations.

CT also reveals secondary effects of subdural hematoma, including midline shift (displacement of brain structures to the opposite side), effacement of brain sulci (flattening of brain surface grooves), and compression of the ventricles (fluid-filled brain cavities). These findings help determine the urgency of surgical intervention.

MRI (Magnetic Resonance Imaging)

MRI provides more detailed images of brain tissue and may be used when CT findings are unclear or when chronic subdural hematoma is suspected. MRI is particularly useful for detecting small or isodense hematomas that may be difficult to see on CT. However, MRI takes longer to perform and is less readily available in emergency settings, making CT the preferred initial study.

MRI can also better characterize the age of blood products and identify associated brain injuries, which helps with treatment planning and prognosis estimation.

Neurological Examination

A thorough neurological examination accompanies imaging studies and includes assessment of:

• Level of consciousness: Using the Glasgow Coma Scale and observing alertness, orientation, and appropriate responses
• Pupil response: Checking size, symmetry, and reaction to light; asymmetric or non-reactive pupils suggest brainstem compression
• Motor function: Testing strength in all limbs, looking for asymmetry that indicates lateralized brain injury
• Sensory function: Evaluating ability to feel light touch and other sensations
• Speech and language: Assessing clarity, comprehension, and ability to follow commands
• Cranial nerves: Testing eye movements, facial symmetry, and other functions

How Is Subdural Hematoma Treated?

Subdural hematoma treatment depends on size, symptoms, and patient condition. Small asymptomatic hematomas may be monitored with repeat CT scans, while larger or symptomatic ones typically require surgical drainage through craniotomy or burr hole procedures. Treatment also addresses underlying causes like blood thinner reversal.

Treatment decisions for subdural hematoma are individualized based on multiple factors including the hematoma's size and location, the patient's neurological status, the type of hematoma (acute vs. chronic), and the patient's overall health and wishes. The primary goals are to relieve pressure on the brain, prevent further bleeding, and optimize conditions for neurological recovery.

The treatment approach represents a continuum from conservative observation to emergency surgical intervention. Understanding these options helps patients and families participate in informed decision-making and set realistic expectations for recovery.

Conservative (Non-Surgical) Management

Not all subdural hematomas require surgery. Small hematomas that cause minimal symptoms may be managed conservatively with careful monitoring. This approach is particularly applicable to chronic subdural hematomas in patients who are poor surgical candidates or when the bleeding is limited.

Conservative management includes:

• Close monitoring: Frequent neurological assessments to detect any deterioration
• Serial CT scans: Repeat imaging to track hematoma size and evolution
• Medication adjustments: Holding or reversing anticoagulants and antiplatelet drugs
• Symptom management: Medications for headache, nausea, and seizure prevention
• Blood pressure control: Maintaining appropriate blood pressure to prevent expansion

With conservative management, the body gradually reabsorbs the blood over several weeks to months. Regular follow-up ensures any clinical deterioration is promptly identified, allowing for surgical intervention if needed.

Surgical Treatment Options

Burr Hole Drainage: This minimally invasive procedure involves drilling one or two small holes through the skull and inserting a tube to drain the accumulated blood. It is the most common surgical treatment for chronic subdural hematoma because it can be performed under local anesthesia with sedation, making it suitable for elderly patients who may not tolerate more extensive surgery. The procedure typically takes 30-60 minutes, and patients often experience rapid improvement in symptoms.

Craniotomy: This more extensive procedure involves removing a larger section of skull bone to directly access and evacuate the hematoma. Craniotomy is typically required for acute subdural hematomas with solid clot that cannot be easily drained through burr holes, or when there is underlying brain injury requiring direct visualization. The bone flap is usually replaced at the end of the procedure, though in cases of severe brain swelling, it may be left off temporarily (decompressive craniectomy).

Subdural Drain Placement: Often used in conjunction with burr holes or craniotomy, a drain catheter may be left in place for several days to allow continued drainage of residual blood and fluid. This reduces the risk of hematoma recurrence.

Post-Operative Care and Recovery

Following surgical treatment, patients are typically monitored in an intensive care or neurosurgical unit. Post-operative care includes:

• Frequent neurological assessments
• Pain management
• Prevention of complications (blood clots, infection, seizures)
• Physical and occupational therapy as appropriate
• Follow-up imaging to confirm hematoma resolution
• Gradual resumption of normal activities

What Is the Prognosis and Recovery Time?

Prognosis for subdural hematoma varies widely based on type, size, treatment timeliness, and patient factors. Chronic subdural hematomas generally have good outcomes with treatment, while acute traumatic SDH carries higher mortality. Recovery ranges from weeks to months, with some patients experiencing long-term effects.

The outcome following subdural hematoma depends on numerous factors, and generalizations can be misleading. However, understanding the typical trajectory helps patients and families prepare for what lies ahead and recognize that recovery is often a gradual process requiring patience and appropriate support.

Chronic subdural hematoma typically has favorable outcomes when properly treated. Studies report mortality rates of less than 5% with surgical treatment, and the majority of patients experience significant improvement in symptoms. However, recurrence occurs in approximately 10-20% of cases, sometimes requiring repeat procedures.

Acute subdural hematoma carries a more guarded prognosis, with mortality rates historically ranging from 40-60%, though modern neurosurgical care has improved outcomes in many centers. The prognosis depends heavily on the patient's neurological status at presentation, the speed of surgical intervention, and the presence of associated brain injuries.

Factors Affecting Recovery

• Age: Younger patients generally recover more completely than elderly patients
• Initial neurological status: Patients who present with better Glasgow Coma Scale scores have better outcomes
• Time to treatment: Faster surgical intervention generally improves outcomes, especially in acute SDH
• Hematoma size and midline shift: Larger hematomas with significant brain displacement have worse outcomes
• Associated brain injuries: Concurrent contusions or diffuse axonal injury worsen prognosis
• Medical comorbidities: Other health conditions affect ability to tolerate surgery and recover

Long-Term Effects

While many patients recover well from subdural hematoma, some experience persistent symptoms that may last months or become permanent:

• Cognitive difficulties including memory and concentration problems
• Headaches that gradually improve over months
• Fatigue and reduced stamina
• Mood changes including depression and anxiety
• Seizures, which may require long-term medication
• Motor or sensory deficits in cases of significant brain injury

Rehabilitation services, including physical therapy, occupational therapy, and speech therapy, play important roles in optimizing recovery. Neuropsychological evaluation may help identify specific cognitive deficits and guide rehabilitation strategies.

Can Medications Increase Subdural Hematoma Risk?

Yes, blood-thinning medications significantly increase subdural hematoma risk. Anticoagulants (warfarin, DOACs) and antiplatelet drugs (aspirin, clopidogrel) impair clotting and can turn minor head injuries into serious bleeding events. Patients on these medications should take extra precautions and seek prompt evaluation after any head injury.

The relationship between blood-thinning medications and subdural hematoma is well-established and clinically significant. These medications, while essential for preventing strokes and blood clots in many patients, create a paradoxical risk: they protect against some types of dangerous clots while increasing the risk of dangerous bleeding.

Understanding this risk is crucial for patients who take these medications, as awareness can lead to both better prevention strategies and faster response to potential bleeding events. The key is not necessarily to avoid these medications (which are often medically necessary) but to take appropriate precautions and maintain vigilance for warning signs.

Types of Blood Thinners and Their Risks

Anticoagulants: These medications interfere with the coagulation cascade, the complex series of reactions that forms blood clots. Warfarin has been used for decades and works by inhibiting vitamin K-dependent clotting factors. Newer direct oral anticoagulants (DOACs) including dabigatran, apixaban, rivaroxaban, and edoxaban work through different mechanisms but similarly increase bleeding risk. Studies suggest anticoagulant use increases subdural hematoma risk by 3-7 times compared to non-users.

Antiplatelet Drugs: Aspirin and clopidogrel prevent platelets from clumping together, the first step in forming a blood clot. While their effect is different from anticoagulants, they also increase bleeding risk after head trauma. Combination therapy with multiple antiplatelet drugs or antiplatelet plus anticoagulant therapy carries the highest risk.

Precautions for Patients on Blood Thinners

• Take fall prevention seriously: remove tripping hazards, use proper lighting, consider assistive devices if balance is impaired
• Wear protective headgear during activities with fall or impact risk
• Keep medications properly managed to avoid over-anticoagulation
• Attend regular monitoring appointments (especially for warfarin users who need INR checks)
• Inform all healthcare providers about your blood thinner use
• Seek medical evaluation after any head injury, even if it seems minor
• Know the signs of subdural hematoma and act quickly if they develop

How Can You Prevent Subdural Hematoma?

Subdural hematoma prevention focuses on avoiding head injuries through fall prevention measures, wearing protective headgear during risky activities, managing blood thinner levels appropriately, and limiting alcohol consumption. For elderly individuals, home safety modifications and balance exercises are particularly important.

While not all subdural hematomas can be prevented, particularly those following severe trauma like motor vehicle accidents, many cases—especially chronic subdural hematomas in elderly individuals—result from preventable minor injuries. A comprehensive prevention strategy addresses multiple risk factors and lifestyle modifications.

Prevention is particularly important for high-risk groups: elderly individuals, those taking blood-thinning medications, and people with a history of falls or alcohol use disorder. For these individuals, even small reductions in fall risk can significantly decrease the likelihood of subdural hematoma.

Fall Prevention Strategies

Falls are the leading cause of subdural hematoma in older adults. Evidence-based fall prevention includes:

• Home modifications: Remove loose rugs and clutter, improve lighting, install grab bars in bathrooms, secure loose electrical cords
• Footwear: Wear well-fitting, non-slip shoes both indoors and outdoors
• Vision care: Regular eye exams and updated corrective lenses reduce fall risk
• Medication review: Work with healthcare providers to minimize medications that cause dizziness or drowsiness
• Exercise programs: Balance and strength training programs like Tai Chi have been shown to reduce falls in older adults
• Assistive devices: Use canes or walkers as recommended by healthcare providers

Protective Measures

• Wear seat belts in vehicles and use appropriate child safety seats
• Wear helmets during cycling, skateboarding, skiing, and other activities with fall risk
• Use appropriate protective equipment in contact sports
• Avoid driving under the influence of alcohol or medications that impair alertness

Managing Risk Factors

• Alcohol moderation: Limit alcohol consumption; excessive drinking increases fall risk and accelerates brain atrophy
• Blood thinner management: Attend all monitoring appointments and keep anticoagulation levels in therapeutic range
• Blood pressure control: Well-controlled blood pressure reduces the severity of any bleeding that occurs