Pia Mater - Pathology

Pathology

Meningitis is the inflammation of the pia and arachnoid mater. This is often due to bacteria that have entered the subarachnoid space, but can also be caused by viruses, fungi, as well as non-infectious causes such as certain drugs. It is believed that bacterial meningitis is caused by bacteria that enter the central nervous system through the blood stream. The molecular tools these pathogens would require to cross the meningeal layers and the blood–brain barrier are not yet well understood. Inside the subarachnoid, bacteria replicate and cause inflammation from released toxins such as hydrogen peroxide (H₂O₂) . These toxins have been found to damage the mitochondria and produce a large scale immune response. Headache and meningismus are often signs of inflammation relayed via trigeminal sensory nerve fibers within the pia mater. Disabling neuropsychological effects are seen in up to half of bacterial meningitis survivors. Research into how bacteria invade and enter the memingeal layers is the next step in prevention of the progression of meningitis.

A tumor growing from the meninges is referred to as a meningioma. Most meningiomas grow from the arachnoid mater inward applying pressure on the pia mater and therefore the brain or spinal cord. While meningiomas make up 20% of primary brain tumors and 12% of spinal cord tumors, 90% of these tumors are benign. Meningiomas tend to grow slowly and therefore symptoms may arise years after initial tumor formation. The symptoms often include headaches and seizures due to the force the tumor creates on sensory receptors. The current treatments available for these tumors include surgery and radiation.