User:Swk152419/Arachnoiditis

Background and Anatomy
Arachnoiditis is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the central nervous system. The most outer layer of the meninges is the dura mater (Latin for hard) and adheres to inner surface of the skull and vertebrae. The arachnoid is under or "deep" to the dura and is a thin membrane that adheres directly to the surface of the brain and spinal cord.

Etiology
Arachnoiditis has been described as having many different etiologies. As an infectious source, tuberculosis, syphilis  , candida , mycosis , and HIV. As a mechanical source, spinal and cranial surgery, trauma , and disc herniation. Prior disease including ankylosing spondylitis, autoimmune vasculitis , and Guillain-Barré syndrome have been known to cause arachnoiditis. Chemical causes include morphine, myelograms with oil-based radiographic contrast agents , phenolic solutions , chlorhexidine , epidural injection of steroids and antibiotics , blood in subarachnoid hemorrhage , epidural blood patches and anesthetics. Oftentimes, the precise cause of arachnoiditis is not know due to the variable latency from cause to symptom onset. With growing incidence of spine surgery, a common cause of arachnoiditis is lumbar spine procedures.

Pathogenesis
The above etiologies can cause inflammation of the arachnoid, leading to arachnoiditis. This inflammation is enough to cause pain and even potentially neurological deficits - symptoms caused by nerves not communicating properly with the body's mechanisms for sensation and movement. The inflammation can lead to the formation of scar tissue and adhesion that can make the spinal nerves "stick" together, a condition where such tissue develops in and between the leptomeninges - between dura and arachnoid or pia and arachnoid. This condition can be very painful, especially when progressing to adhesive arachnoiditis. Adhesive arachnoiditis occurs when inflammation leads to recruitment of cells to the area and fibrous exudate, and ensuing deposition of collagen forms bands that could cause ischemia or even atrophy of the spinal cord or nerve roots. Chronic inflammation could lead to arachnoiditis ossificans, in which the inflammed arachnoid becomes ossified, or turns to bone, and is thought to be a late-stage complication of the adhesive form of arachnoiditis. More serious complications can occur, including spinal cord swelling, myelomalacia, cauda equina syndrome, and hydrocephalus.

Signs and Symptoms
Arachnoid inflammation can lead to many painful and debilitating symptoms which can vary greatly in each case, and not all people experience all symptoms. Chronic pain is common, including neuralgia, while numbness and tingling of the extremities can occur with spinal cord involvement, and bowel, bladder, and sexual functioning can be affected if the lower part of the spinal cord is involved. While arachnoiditis has no consistent pattern of symptoms, it frequently affects the nerves that supply the legs and lower back. Many patients experience difficulty sitting for long (or even short) periods of time due to discomfort or pain.