Subdural hematoma

Subdural hemorrhage can be broken down. Sub means below, “dural” which refers to the outermost protective layer of the brain, which is called dura mater, and “hemorrhage” refers to bleeding. So, a subdural hemorrhage is when there’s bleeding below the dura mater.

OK - let’s start with some basic brain anatomy. The brain is protected by 3 thin layers of tissue called the meninges which covers the brain and spinal cord.

The inner layer of the meninges is the pia mater, the middle layer is the arachnoid mater, and the outer layer is the dura mater. The pia and arachnoid maters, are also called leptomeninges.

Between the leptomeninges, there’s the subarachnoid space, which houses cerebrospinal fluid, or CSF.

CSF is a clear, watery liquid which is pumped around the spinal cord and brain, cushioning them from impact and bathing them in nutrients. The outer membrane, the dura mater consists of two layers.

The internal layer of the dura mater lies above the arachnoid mater - the two are separated by the subdural space. The external layer of the dura mater adheres to the inner surface of the skull.

These two layers of the dura mater travel together, but at certain spots, the internal layer of the dura mater separates from the external one to form the meningeal folds.

The meningeal folds help divide the sections of the brain like the falx cerebri which separates the two hemispheres of the cerebrum, and the tentorium, which covers the cerebellum and separates it from the cerebrum. The subdural space plays a major role in venous blood drainage in the brain.