Subdural hematoma is an intracranial blood clot inbetwixt the brain and its leather covering. 

Medical terminology often uses Latin or Greek.

In Latin, the leather covering the brain is called dura. Also in Latin, the word for UNDER is SUB. 

So, a clot under the dura is a subdural hematoma.

Of note, dura is short for dura mater, which translates into English as “tough mother”. This is a loan translation of the original medical term used by the ancient physicians who first described this structure as أم الدماغ الصفيقة .

A hematoma is a blood clot. Not fresh liquid blood, but more like a blood pudding or jello type substance that forms immediately when blood leaves an artery or vein. Clot formation depends on a functional blood clotting cascade, a complex interplay of chemicals and proteins, originally designed to prevent exsanguination.

By the time a clot forms, the active bleeding has usually stopped or slowed down already. In fact, the hematoma (clot) often acts like a plug, putting pressure onto the injured blood vessel, helping to stop the bleeding. 

Once the hematoma is sitting in the subdural space, it will continue to put some pressure onto the brain surface. In fact, the hematoma will over time swell and get larger from attracting fluid. Oftentimes, the orginal clot is too small to create brain problems. Over time however, like a sponge absorbing water, protein and cellular debris within the hematoma will act like a sponge, sucking up cerebrospinal fluid (CSF) which is the fluid the brain is immersed in, 

Any pressure on the brain (from a subdural hematoma, or a tumor, or infection) can cause the brain to not function properly, resulting in brain compression symptoms.

In situations when the hemorrhage does not stop, increased pressure on the brain will cause first coma, then death.

Such excessive hemorrhage may happen with severe brain trauma when several blood vessels have been torn during the impact. It may also happen, or get aggravated, by blood thinners or antiplatelet agents that prevent a clot to form, and cause ongoing hemorrhage once a blood vessel is injured.

 

Anything that makes blood vessels pop may cause a subdural hematoma.

Trauma (head injury) would do it. Pressure increases (Valsalva situations, e.g. heavy lifting or pushing hard when constipated) may do it. 

Symptoms of Subdural Hematoma include:

• Pain/headache
• Getting sleepy/drowsy
• Getting confused or irritated
• Unable to speak or understand language
• Losing consciousness
• Getting weaker in the arm and/or leg and/or face
• Losing balance and coordination, frequent falls

 

Symptoms of arm or leg weakness or numbness are usually opposite the area of bleeding, because brain nerves are criss-crossed.

Therefore, the left brain works the right side of our body, while the right brain controls the left side of our body. 

Dozens of small veins run between the brain  surface and the inside of the skull bone. These are called “bridging veins”. 

When we get older, the brain gets wrinkles like the skin does, and shrinks (called brain atrophy). When the brain shrinks away from the skull, the bridging veins get under stretch. Think puppet on a string. The brain is the puppet, the veins are the strings.

Any head bump (no matter how minor), or increased head pressure while lifting something, or pushing down during a difficult BM, may cause a bridging vein to pop. 

When the bridging vein pops, blood will spill inbetween the brain and its coverings. This spillage is low pressure because the veins are the drainage system and don’t have much pressure in them. This spillage often goes unnoticed, because the amount of blood oozing out is often relatively small, and without pressure, the sensory nerves do not notice it.

If the blood is fresh (hours, days) we call it “acute”.  It looks white and bright on a CT scan.

If the blood has been sitting there for a few weeks, we call it “subacute”.

 

On a computed tomography (CT) head scan, the subacute subdural hematoma looks some shade of grey.

The fresher or more recent the hemorrhage, the lighter the grey. The older or the more remote the hemorrhage event, the darker the grey.

If the hematoma has been there for a few months, it will dilute with cerebrospinal fluid (CSF) or brain fluid, turning into a thin liquid and we call it “chronic subdural hematoma”.

Most chronic subdural hematoma have been thinned out with cerebrospinal fluid to a degree that they can be drained out using a thin catheter such as a Jackson Pratt (JP) drain.

Sometimes, a skin forms on and around the original hemorrhage. Like skin on a pudding that has been sitting on the counter for a couple days, protein membranes form on the surface and inbetween the blood clot. 

Membranes or bubble formation can be identified on CT scan. If multiple membranes or septations are found, open skull surgery is usually needed to trim off the membranes, to properly drain and remove the subdural hematoma.

Relax. It is not bleeding. It is rarely ever an “active crime scene”. The bullets have been shot, the robbers have left. You have been robbed alright. Damage has been done. You called 911 and the team is working to prevent additional (secondary) problems.

Hemorrhage  usually only lasts for a few minutes, then stops.  If an intracranial hemorrhage does not stop, the brain will get irreversibly damaged and death is a frequent ultimate outcome.

The risks of ongoing bleeding are higher in anyone taking blood thinners (Coumadin, Eliquis, Pradaxa) or platelet aggregation inhibitors (Aspirin, Plavix). Patients taking these medications are at risk of potentially fatal brain hemorrhages, including subdural hematomas, in case of head trauma or stroke.

Bleeding can happen again. Some days, weeks or even months after the initial subdural hemorrhage, blood vessels can pop or ooze, spilling some more blood into the space between the brain and its coverings.

Usually, the amount of new bleeding is relatively small. If there is pre-existing pressure and brain shift from an older hematoma/blood clot, the additional hemorrhage can cause headaches or weakness or numbness or seizures.