The brain is covered by layers of membranes, known collectively as meninges, which function to protect the central nervous system and regulate the fluid pressure within the skull. There are three layers of meninges: the inner pia mater, the arachnoid layer, and the outer dura mater, which together form a barrier. Disruption or damage to the barrier can occur as a result of a number of diseases, and this can either leave the brain more exposed, or put the brain under pressure, either of which can result in brain damage.
Meningitis is an infection of the meninges by bacteria or viruses. According to the University of Maryland, viral meningitis is more common and less severe, and may cause headaches, fatigue and depression. Bacterial meningitis is less common and more severe--it is potentially fatal. The University of Maryland reports that several types of bacteria can cause bacterial meningitis, but it is usually caused by one of three types of bacteria.
Meningitis is diagnosed by spinal tap, which helps doctors look for infection within the spinal fluid; by body and brain imaging; or by blood test. Once diagnosed, bacterial meningitis is treated with antibiotics, and viral meningitis is treated with medication to ease the symptoms of the disease.
The meninges can develop tumors, which are called meningiomas. According to Massachusetts General Hospital, meningiomas are usually benign tumors, which means they are noncancerous and do not metastasize to other parts of the body. Meningiomas grow outside of the brain, but they can put pressure on brain tissue as the tumor grows inside the skull.
According to the University of California Los Angeles, meningiomas account for around 20% of all tumors of the head, and 10% of tumors originating from the spine. Common symptoms of meningiomas are headaches, vision problems, and muscle weakness or paralysis. Depending where the meningioma occurs, and which parts of the brain are under pressure from the tumor, patients with meningiomas may also display other symptoms. UCLA states that the most common treatments for meningiomas are surgery and radiotherapy.
Hematomas and Hemorrhages
Hematomas, a result of hemorrhage, are collections of blood that pool outside of blood vessels. Hematomas can occur between the layers of meninges, increasing the fluid pressure within the skull and putting pressure on the brain.
According to Michigan State University, there are three types of meningeal hematomas. Epidural hematoma occurs from tearing of the meningeal artery; blood pools between the dura mater and the skull. Subdural hematomas arise from accumulation of blood between the arachnoid and dura mater layers. Subarachnoid hematomas occur when blood accumulates between the arachnoid layer and pia mater. Hematomas may be treated by removing blood or blood clots to relieve pressure within the skull.