Arachnoid mater

The arachnoid mater is one of three membranes that cover the brain and the spinal cord. The arachnoid is the middle layer — situated between the outermost layer, the dura mater, and the innermost layer, the pia mater. Tiny fibers extend off the arachnoid membrane and attach to the pia mater. Furthermore, the arachnoid membrane gets its name from its resemblance to a spider web.

Between the arachnoid mater and pia mater, in an area called the subarachnoid space, flows cerebrospinal fluid (CSF). Because the brain produces much more CSF than the body uses each day, a large amount of CSF is discarded and reabsorbed by the body. It is believed that discarded CSF escapes the subarachnoid space through arachnoid granulations, which are tiny protrusions of the arachnoid mater, then through the outermost dura mater and into the brain’s venous sinuses. The sinuses direct the excess CSF into the bloodstream for reabsorption. Another theory suggests that excess CSF is reabsorbed through the lymphatic system via cranial nerves and spinal nerve roots.

Within the cranium and along the spinal canal are pockets of CSF called arachnoid cisterns. Occasionally, arachnoid cysts form near these cisterns. These cysts usually form during infancy and may not produce symptoms until later in life. When arachnoid cysts form along the spinal cord, it can produce symptoms of radiculopathy. These symptoms are similar to those produced by spinal conditions such as sciatica, degenerative disc disease, herniated discs or bulging discs and can include:

  • Tingling or numbness in the shoulders, arms, hands, legs or feet
  • Muscle weakness
  • Radiating pain that begins in the neck or back and moves to the extremities

Cysts associated with the arachnoid mater often are asymptomatic and go undetected. The symptoms of radiculopathy, sometimes blamed on arachnoid cysts in the spine, more often are caused by conditions such as osteoarthritis, foraminal stenosis or spinal stenosis.

If conservative treatment of these symptoms has proven ineffective, a physician may present surgery as an option. Laser Spine Institute offers alternatives to traditional open spine surgery. Contact Laser Spine Institute to learn how a minimally invasive, outpatient procedure can help you rediscover a life without pain.