Have you ever bumped your head and developed a “goose-egg?” It’s truly amazing how fast that big bruise under the skin grows. That bruise, or hematoma, is from a broken blood vessel, usually a vein. The pressure from the swelling helps with clotting, along with the blood’s own clotting factors. This types of hematoma typically takes a week or more to go away. And, if it’s on the forehead, it’s often followed by one or two “black eyes.” That’s because the blood tends to spread along the tissue planes, and gravity notoriously pulls everything downward causing it to pool in the eye sockets, where the blood cells degrade and their components are reabsorbed by the body. Recycling at its best!
A subdural hematoma is that same “goose-egg”, but it happens under the skull and between the coverings of the brain. So what makes it so special that it causes a brain injury? A little lesson in anatomy will help.
Anatomy of the Brain Coverings
A subdural hematoma is a blood collection from broken blood vessels that occurs below the dura mater and above the arachnoid and pia mater; therefore the blood collection becomes “trapped” between the coverings of the brain. Depending on how bad the bleeding is, there can be a fairly large collection of blood. Where can it expand? It can expand along the planes of these coverings, but since the hard skull is on the surface, the “goose-egg” effect occurs inward, compressing the brain and all of the neurologic tracts within the brain. This pressure leads to loss of blood circulation, oxygen and glucose delivery and ultimately death of that brain tissue. The brain then responds by becoming swollen, increasing the pressures in the brain/cranium and causing even more damage. Depending on the location of the subdural hematoma,the person affected will react in a specific way.
What Causes a Subdural Hematoma?
Some are spontaneous, but these are relatively rare. There is usually a fall or injury to the head that preceeds the development of a subdural hematoma. Interestingly, the fall can be minor without direct trauma to the head in an elderly person or someone on blood thinners. Looking at the diagram above, small blood vessels supply the meninges with the necessary circulation. As some brains age, they shrink, especially in individuals with dementia. As the brain shrinks, the blood vessels are stretched to continue to supply the various coverings with circulating nutrients. The stretching makes the vessels more fragile, and the brain shrinkage allows more room to move around when “shaken” or “dropped”. Thus, a shearing effect occurs, breaking those vessels and allowing for bleeding to occur. The addition of blood thinners to prevent clotting can cause a tiny injury to become a huge hemorrhage. Obviously, the bleeding becomes even more profuse when a person is over-anticoagulated, either incidentally or inadvertantly. A direct blow to the head, either related to a fall or simply bumping one’s head, can provide enough impact to cause damage both externally and internally; external hematomas are an obvious sign to a medical provider to consider internal injuries.
What are the Signs and Symptoms of Subdural Hematomas?
According to the NIH website, signs/symptoms of subdural hematomas in adults include the following:
- Confused speech
- Difficulty with balance or walking
- Lethargy or confusion
- Loss of consciousness
- Nausea and vomiting
- Slurred speech
- Visual disturbances
Also, according to the NIH website, signs/symptoms of subdural hematomas in infants include the following:
- Bulging fontanelles (the “soft spots” of the baby’s skull)
- Feeding difficulties
- Focal seizures
- Generalized tonic-clonic seizure
- High-pitched cry
- Increased head circumference
- Increased sleepiness or lethargy
- Persistent vomiting
- Separated sutures (the areas where growing skull bones join)
How are Subdural Hematomas Diagnosed?
According to an emedicine article, the best diagnostic tool for identification of an acute subdural hematoma is a non-contrast CT scan of the head; the blood collection has a typical appearance that is easily recognizable. It becomes more complicated in subacute and chronic subdural hematomas; a contrast head CT or a brain MRI might be more accurate.
How are Subdural Hematomas Treated?
It depends on the size and acuity as well as the presenting condition of the patient. A patient with obvious brain injury and neurologic deterioration requires emergent surgical and medical treatment; the surgical interventions can range from a “burr hole” to relieve the pressure to a full-blown craniotomy to evacuate the hematoma and control additional bleeding. Sometimes, secondary surgeries are required. Some small hematomas can be monitored in patients without neurologic compromise, and these can potentially resolve on their own or become chronic. If a patient with a subdural hematoma is over-anticoagulated (too much Coumadin), it is often necessary to reverse the anticoagulation before performing surgery to prevent additional hemorrhage; however, this delay can often cause additional permanent brain injury and functional deterioration of the patient.
Medical therapies include controlling blood pressure, controlling intracerebral pressure, preventing seizures from occurring (due to irritation of the meninges and brain), supporting heart and lung function, and managing fluid and electrolyte levels.
What is the Prognosis for Subdural Hematoma?
Since there is such a wide range of presentations and since each patient provides a unique set of circumstances, prognoses vary greatly, but overall, morbidity and mortality rates are extremely high. According to the emedicine article, the overall mortality of a simple subdural hematoma (without brain injury) is about 20%; the overall mortality rate for a complicated subdural hematoma (brain injury present) is about 50%! Even with successful evacuation, a patient runs the risk of recurrent bleeding, infection, chronic seizure disorder and permanent neurologic functional loss (depending on location).
If you are caring for an elderly person, do everything possible to prevent falls!
Monitor anticoagulant levels diligently. Be aware of potential interactions with specific foods and “new” medications.
If a fall occurs, seek evaluation as soon as possible; earlier interventions generally have better outcomes.
If evaluated and discharged, continue to observe the patient for changes in behavior, cognition and function for up to 1 week after the initial injury; seek treatment emergently if any changes are observed.
Avoid alcohol and narcotics which can both aggravate a potential condition and mask its presentation.