Chronic Subdural Hematoma — Delayed Brain Bleeding, Symptoms, and Treatment

Most families only need the Quick Summary + the Treatment and Prognosis sections. The rest is for deeper understanding.

Definition

A chronic subdural hematoma (cSDH) is a slowly developing collection of blood and blood-breakdown products in the subdural space, typically surrounded by vascularized membranes that may contribute to its persistence and gradual enlargement. It most commonly develops after a minor or even forgotten head injury, although it can also occur without a clearly recognized trauma.

Unlike acute bleeding, chronic subdural hematomas grow over time.

Image: Preoperative Brain CT Scan The scan shows a crescent-shaped, low-density hematoma (a subdurah collection of old blood or chronic subdural hematoma) in the right frontotemporoparietal area. This has caused compression of the lateral ventricle (squeezing of the brain’s fluid-filled chambers) and a 0.8 cm midline shift to the left.

Incidence and Age Distribution

Chronic subdural hematoma is one of the most common neurosurgical conditions in the elderly.

The reported incidence ranges from approximately 8–15 cases per 100,000 people per year in the general population, but increases significantly with age — reaching 60–80 cases per 100,000 per year in individuals over 65 years, and even higher in those over 80.

The average age of affected patients is typically between 70 and 80 years. Although chronic subdural hematoma is primarily a disease of the elderly, approximately one-third of patients are younger than 65 years. In this younger population, risk factors such as alcohol dependence, anticoagulant use, and head trauma are more frequently involved.

Due to population aging and widespread use of anticoagulant and antiplatelet medications, the incidence of chronic subdural hematoma continues to rise worldwide.

Why Chronic Subdural Hematomas Form

With aging or chronic alcohol use, brain atrophy increases tension on the bridging veins that run from the brain surface to the dura mater. These veins become stretched and more vulnerable to minor tears, allowing slow venous bleeding to occur even after trivial or forgotten head trauma.

Brain atrophy also enlarges the subdural space. This enlargement is crucial: it allows a relatively larger volume of blood to accumulate without immediately producing symptoms. In a younger brain with minimal extra space, a small venous bleed is more likely to be rapidly resorbed before it becomes clinically significant. In contrast, in an atrophic brain, the same amount of bleeding may persist long enough to avoid early symptoms yet remain present within the subdural space. This asymptomatic persistence is a key step in the development of a chronic subdural hematoma. When blood remains in the subdural space, it can trigger inflammatory and vascular changes. Over time, biologically active membranes form around the collection. These membranes contain fragile new blood vessels that may leak repeatedly, contributing to gradual enlargement of the hematoma.

Coagulation abnormalities — common in elderly patients, alcohol-dependent individuals, and those taking anticoagulant or antiplatelet medications — further increase both the likelihood of initial bleeding and the risk that the collection will continue to grow rather than resolve spontaneously.

This happens especially in:

• Older adults, as they often develop brain atrophy (shrinkage)
• Alcohol-dependent patients as they often develop brain atrophy too
• Patients with brain atrophy
• People with large subarachnoid spaces
• Patients taking blood thinners or antiplatelet drugs
• Patients with clotting disorders
• People with achnoid cysts
• Patients with low intracranial pressure
  (for example from over-drainage of a VP shunt)

How the Hematoma Grows (Pathophysiology)

Once bleeding starts:

1. A thin clot forms in the subdural space
2. The clot becomes surrounded by a fibrous membrane
3. That membrane produces inflammatory and angiogenic factors
4. Fragile capillaries grow into the membrane
5. These vessels leak fluid and blood
6. The hematoma expands
7. Pressure on the brain increases

This is why chronic subdural hematomas often worsen weeks after the injury, not immediately.

Typical Location

Chronic subdural hematomas usually lie over the convex surface of the brain.

They can be:

• Unilateral (most common)
• Bilateral (less common)

When bilateral, one side is usually larger and more symptomatic.

Effect on the Brain

As the hematoma enlarges, it:

• Compresses the brain – This means the pressure is squeezing healthy brain tissue, which can lead to permanent damage if not relieved.
• Shifts midline structures – This indicates that the pressure is so high it is pushing the brain out of its normal position, a sign of severe imbalance inside the skull.
• Can cause subfalcine herniation – This occurs when one part of the brain is pushed under a rigid internal membrane, potentially cutting off vital blood flow.
• In severe cases, transtentorial herniation – This is a life-threatening emergency where the brain is pushed downward toward the brainstem, risking the loss of basic functions like breathing.

This pressure — not the blood itself — causes the neurological symptoms.

Image: Brain Herniations — A large chronic subdural hematoma creates a mass effect, pushing parts of the brain into narrow spaces where they normally do not belong. In these tight areas, the pressure can compromise vital parts of the brain, including the brainstem, which controls breathing and consciousness. Among the different types of herniation, transtentorial (uncal) herniation is the most clinically significant pattern because it is the one most often associated with sudden deterioration.

When Symptoms Appear

Symptoms usually begin 10 days to several weeks or months after the injury.

Many patients do not remember the trauma.

Some patients remain asymptomatic until the hematoma becomes very large, and then deteriorate rapidly and require urgent surgery.

Symptoms

Symptoms depend on size and brain compression and may include:

• Headache
• Confusion
• Memory problems
• Personality or behavior change
• Drowsiness
• Speech difficulty
• Weakness on one side of the body
• Balance problems
• Seizures
• Reduced level of consciousness

In some cases, patients may have had some of these conditions prior to the injury, and it may take some time before a worsening of symptoms or the first new signs become noticeable.

Diagnosis

CT scan

The primary test. It shows:

• Hematoma size
• Brain compression
• Midline shift

An experienced neurosurgeon can also judge whether the hematoma is liquefied enough for minimally invasive drainage instead of craniotomy.

MRI

Helpful when CT findings are unclear or when membranes and stages of blood breakdown must be assessed.

Blood tests

Very important because many patients have:

• Clotting disorders
• Low platelets
• Blood-thinning medications

Whenever feasible, coagulation abnormalities should be corrected or optimized to a safe range before surgery in order to minimize perioperative bleeding risk.

Treatment — When to Operate and When to Observe

The key question in chronic subdural hematoma is whether surgery is needed at all, and how urgently it should be performed. In many patients, surgery is not required at all, and careful observation is the safest approach.

Conservative (Non-Surgical) Treatment

In selected patients with small hematomas and no significant neurological symptoms or brain compression, conservative management may be appropriate.

Approximately 20–30% of carefully selected chronic subdural hematomas may resolve without surgery under close monitoring.

Conservative management may include:

• Careful monitoring
• In selected cases, short courses of corticosteroids may be considered, although their role remains controversial and individualized.
• Adjustment or discontinuation of blood-thinning drugs
• In selected neurologically stable patients, middle meningeal artery (MMA) embolization may be considered as an adjunctive treatment to reduce the risk of recurrence (see detailed explanation below).

Surgery

The choice of surgical technique in chronic subdural hematoma depends on whether the hematoma is liquefied, septated, recurrent, and how fragile the patient is.

Larger or symptomatic hematomas require surgical evacuation. The key decision in chronic subdural hematoma is not only how to operate, but whether surgery is needed at all and how urgently it should be performed.
Surgery may be urgent, but in many cases surgery can be delayed briefly to stabilize clotting.

Surgical Techniques

1. Burr-hole drainage (most common)
2. Twist-drill drainage (less invasive option)
3. Craniotomy (rarely required)

Burr-hole drainage

If the hematoma is liquefied, it can be removed using:

• One or two burr holes
• Irrigation (washing out the blood), drainage, or most commonly, a combination of both.

Image: Chronic Subdural Hematoma Surgery The image on the left shows a trepanation (the creation of small holes in the skull, known as burr holes) and the hematoma before evacuation and irrigation. The image on the right shows the hematoma after removal, with a drain placed in the remaining cavity, which will stay in place for 2 days.

Drains may be:

• One or two
• Passive drainage into collection bags

The operation can be done under:

• General anesthesia
• Or local anesthesia with sedation

Bilateral hematomas are usually treated on both sides, often in one session.

Post-operative Care

After surgery:

• Patients usually wake up immediately if they were awake before
• They lie flat for 1–2 days
• Receive supplemental oxygen

This:

• Helps the brain re-expand – This ensures that the brain fills the space previously occupied by the hematoma, preventing fluid from collecting in the empty gap.
• Reduces recurrence – Keeping the patient flat and well-oxygenated helps stabilize the brain’s position and significantly lowers the risk of the bleeding coming back.
• Reduces pneumocephalus (air in the skull) – This helps the body naturally absorb any air trapped inside the skull during surgery, which is essential for reducing headaches and pressure.

Drains are usually removed after 2 days.

Some surgeons obtain a control CT scan; others do not if the patient is neurologically well and significant drainage has occurred.

Early CTs often still show residual fluid — this is not dangerous if the brain is decompressed.
Removing 50% of the volume is often sufficient.

Twist-Drill Drainage

Twist-drill drainage is a minimally invasive technique used in selected patients with chronic subdural hematoma.

Instead of creating a larger burr hole, the surgeon makes a very small opening in the skull using a narrow twist drill. A soft catheter is then inserted into the subdural space to allow slow drainage of the liquefied hematoma.

This procedure is typically performed under local anesthesia.
In carefully selected, neurologically stable patients — particularly very elderly or medically fragile individuals — it may be performed in a monitored hospital setting without transferring the patient to a full operating theater.

Advantages:

• Less invasive
• Can avoid general anesthesia
• Shorter procedural time

Limitations:

• Slightly higher recurrence rate compared to burr-hole drainage
• Less effective in septated or organized hematomas

For this reason, twist-drill drainage is generally reserved for selected cases rather than being the standard first-line surgical technique. Postoperative care after twist-drill drainage is generally similar to that following burr-hole surgery.

When Craniotomy Is Needed

Craniotomy is rare and reserved for:

• Septated (compartmentalized) hematomas – This means the blood is trapped in several separate „pockets“ or compartments. A simple drain cannot reach them all, so a craniotomy is necessary to open and clean each pocket directly. This is rare.
• Multiple recurrences – If the hematoma keeps coming back after being drained, a craniotomy is performed to find the underlying cause, stop any persistent slow leaks, and ensure the space is thoroughly cleared.

In those cases, the surgeon may remove the thick outer capsule to prevent further bleeding.

Recurrence and Modern Treatment

If the hematoma recurs, an effective modern option is:

Middle Meningeal Artery (MMA) Embolization

This is a modern, minimally invasive procedure used to treat chronic or recurring subdural hematomas by „cutting off“ their blood supply.

The goal: By cutting off the „fuel supply“ to the membrane, the procedure prevents the hematoma from refilling (re-accumulation) and allows the body to naturally absorb the remaining blood over time.

How it is performed: The doctor inserts a thin, flexible tube called a catheter into an artery in the groin (leg). Using real-time X-ray guidance, the catheter is carefully advanced through the vascular system all the way up to the small arteries in the head that „feed“ the hematoma membrane. Tiny particles or a special medical „glue“ are injected through the catheter to permanently block these small vessels.

Seizures and Epilepsy in Chronic Subdural Hematoma

Chronic subdural hematoma can be associated with epileptic seizures and the development of epilepsy.
The mechanism is not the hematoma itself, but prolonged cortical irritation, inflammatory membrane formation, and hemosiderin deposition on the brain surface.

Seizures may occur before diagnosis, after surgical evacuation, or weeks to months later.
In elderly patients, epileptic seizures are often subtle and may be misinterpreted as confusion or transient neurological events.

Surgical evacuation usually reduces seizure risk, but in some cases, persistent cortical changes may lead to chronic epilepsy requiring long-term management.

Prognosis

When chronic subdural hematoma is recognized and treated before severe brain compression or prolonged neurological decline, the prognosis is often good, even in elderly patients. Outcome depends mainly on preoperative neurological status, age, frailty, anticoagulant use, recurrence risk, and associated brain injury.

Red Flags — When to Seek In-Person Medical Evaluation for Chronic Subdural Hematoma

Patients and family members should seek urgent in-person medical evaluation with brain imaging (CT or MRI) if a person with known or suspected chronic subdural hematoma develops sudden or worsening confusion, increasing drowsiness, new weakness or speech difficulty, severe or rapidly worsening headache, seizures, repeated vomiting, or a sudden neurological decline after a period of apparent stability. These signs may indicate dangerous brain compression and require immediate hospital assessment.

Frequently Asked Questions About Chronic Subdural Hematoma