SUBDURAL HEMATOMA (ACUTE)

Under the dura

A Subdural Hematoma is the other common type of a traumatic brain bleed.  The blood collects between the dura and subarachnoid mater, which is more “central” than to the epidural space. 

An Acute subdural bleed can occur following a major head injury. Vessels will shear. They will probably pass out, slowly get worse and then die. No lucid period here. Bleeding here is usually venous, and therefore slower than epidurals (arterial bleeding). 

The prognosis is very poor (50% to 90% mortality). Surgical drainage is kinda ineffective. Treat their raised ICP the best you can, hyperventilate (to vasoconstrict the cerebral arteries), put them in reverse trendelenburg and give them 3% IV normal saline or Mannitol.

SUBDURAL HEMATOMA (CHRONIC)

A Chronic Subdural Hematoma is similar to the acute SH, but it involves minor trauma (fall) that shears the bridging veins of a patient who is elderly or alcoholic. The bridging veins are the veins that exit the top of the cerebrum and drain into the dural sinuses. 

The principle here is that our veins stay the same size our entire adult lives. If you get old and demented, or if you are an alcoholic for decades, then you will lose brain tissue. Your brain shrinks. But the vessels stay the same size. So if you have a big robust brain that fills the skull, the veins that exit the brain at the very top don’t have a very far way to go to reach the sinuses. But in alcoholism and dementia, the brain is atrophied, and the veins are much further from the sinuses. Those veins (called bridging veins) are exposed and vulnerable. Injuries usually involve sudden acceleration/deceleration. If they are sitting in a car, and then come to a sudden halt, the momentum carries the head forward then suddenly STOPS. The skull stops, but momentum carries the brain and CSF forward. That movement can cause the bridging veins to shear. 

The injury to the bridging veins is usually pretty small. So the bleeding will occur slowly over days and weeks, which gives the brain time to compensate; therefore, you usually don’t see a huge  midline shift. Instead these patients will have headaches and progressively worsening cognitive function (which is often missed due to concomitant dementia). The bleeding usually stops by itself.