Subdural Hemorrhage (Subdural Hematoma)

What a subdural hematoma is

The brain is wrapped in three layers. The outermost, the dura, is tough and lines the skull. Small bridging veins cross the space beneath it to reach the brain. When the head is jolted, these veins can stretch and tear. Blood collects in the subdural space, forming a hematoma that presses on the brain.

Because veins bleed more slowly than arteries, symptoms can appear immediately or develop over days or weeks. This differs from an epidural hematoma, which is usually arterial, lies above the dura and causes rapid deterioration, often after a lucid interval.

Types of subdural hematoma

A subacute hematoma falls in between, appearing 3 days to 3 weeks after injury.

Causes and risk factors

• Head injury: the main cause. In older people the injury can be minor, such as bumping the head on a cupboard.
• Older age: the brain shrinks with age, which stretches bridging veins and makes them easier to tear. See falls.
• Blood thinners: warfarin, apixaban, rivaroxaban and others, as well as aspirin and clopidogrel.
• Heavy alcohol use: causes brain shrinkage, falls and bleeding tendency.
• Low pressure in the spinal fluid: after a spinal tap, a spinal fluid leak or shunt overdrainage.
• Bleeding disorders and low platelets.
• Infants: birth trauma, and abusive head trauma (shaken baby syndrome).

Symptoms

Acute subdural hematoma

• loss of consciousness or rapidly worsening drowsiness
• confusion, agitation
• severe headache and vomiting
• weakness on one side, unequal pupils
• seizures
• slow breathing and coma in severe cases

Chronic subdural hematoma

Symptoms build up gradually over days to weeks, and the original injury may be forgotten:

• persistent or worsening headache
• confusion, poor concentration and memory problems
• personality change, apathy or sleepiness
• unsteadiness, balance problems and falls
• weakness or clumsiness on one side
• difficulty speaking
• seizures

Because these symptoms develop slowly, chronic subdural hematoma can be mistaken for dementia, stroke or normal pressure hydrocephalus. Unlike dementia, it is treatable.

In babies

Signs include irritability, poor feeding, vomiting, drowsiness, seizures, a bulging soft spot and a head that is growing faster than expected. Doctors look for other signs of injury, such as bleeding at the back of the eyes, when abuse is possible.

How it is diagnosed

• CT scan of the head: the main test. Fresh blood appears bright white. Older blood looks darker, matching the age of the bleed.
• MRI: for small or subacute bleeds and in infants.
• Blood tests: blood count, platelets and clotting tests, especially in people on blood thinners.
• Neurological exam: consciousness (Glasgow Coma Scale), pupils, strength and speech.

Treatment

Immediate care

• Reversing blood thinners with specific antidotes, vitamin K or clotting factors.
• Controlling blood pressure, seizures and pressure inside the skull.

Surgery

• Craniotomy: a section of skull is removed to evacuate a thick, clotted acute hematoma and stop bleeding. The bone is replaced, or sometimes left out temporarily if the brain is very swollen.
• Burr hole drainage: one or two small holes are drilled to drain the liquid blood of a chronic hematoma. A drain is usually left in for 1 to 2 days, which reduces the chance of it returning.
• Middle meningeal artery embolization: a catheter procedure that blocks the artery feeding the hematoma's membranes. Recent trials show it reduces recurrence when added to surgery, and it is used in selected patients.

Watchful waiting

Small hematomas that cause few or no symptoms can be monitored with repeat scans, as the body often reabsorbs them over weeks.

Recovery and outlook

• Acute subdural hematoma: often occurs alongside other brain injuries (traumatic brain injury). Outcome depends on the person's condition before surgery, age and other injuries. Many survivors need rehabilitation for movement, speech, memory and mood.
• Chronic subdural hematoma: most people improve markedly after drainage, often within days. About 1 in 10 to 1 in 5 have a recurrence that needs further treatment, usually within the first few months.
• Doctors decide carefully when to restart blood thinners, balancing bleeding and clot risks.

Prevention

• Prevent falls: remove trip hazards, use good lighting and handrails, review medicines that cause dizziness, and treat vision and balance problems.
• Wear a helmet for cycling, motorcycling, skiing and contact sports.
• Wear a seat belt.
• Limit alcohol.
• If you take blood thinners, seek assessment after any head injury.
• Never shake a baby. If you feel overwhelmed, put the baby safely in the crib and step away.

Frequently asked questions

What is the difference between acute and chronic subdural hematoma?

An acute subdural hematoma follows a significant head injury and causes symptoms within hours to 3 days, often with rapid loss of consciousness. A chronic subdural hematoma develops slowly, over 3 weeks or more, usually in older adults after a minor fall, causing gradual headache, confusion and weakness.

What are the symptoms of a subdural hematoma in the elderly?

In older adults, symptoms are often gradual: headache, confusion, memory problems, personality changes, drowsiness, unsteadiness, falls and weakness on one side. These can be mistaken for dementia or a stroke. Any older person with these changes after a fall should have a CT scan.

Can a subdural hematoma heal on its own?

Small subdural hematomas that cause few symptoms can be reabsorbed by the body over several weeks, and doctors monitor them with repeat scans. Larger hematomas, or those causing symptoms, usually need surgery to drain the blood and relieve pressure on the brain.

How long does it take to recover from a subdural hematoma?

After drainage of a chronic hematoma, many people improve within days and return to normal activities over a few weeks. Recovery from an acute subdural hematoma with brain injury can take months of rehabilitation, and some people have lasting problems.

Is a subdural hematoma the same as a stroke?

No. A stroke is caused by a blocked artery or bleeding within the brain tissue. A subdural hematoma is bleeding on the surface of the brain, usually from injury. Both can cause weakness and speech problems, and a CT scan quickly tells them apart.