Sciatica is a set of symptoms; the term is used to describe a number of unpleasant effects that occur when any of the spinal nerve roots are irritated or compressed (these nerve roots give rise to the left and right sciatic nerves). Such symptoms are often caused by herniated spinal discs, but also may be the result of spinal stenosis (narrowing of the spinal canal). For many sciatica sufferers, this condition causes serious pain and immobility. Because the sciatic nerves run from the lower back, exit the spine, and reach down the legs to the toes, compression of the nerves can lead to pain, numbness, and weakness in any of these areas.
The sciatic nerves are responsible for sending signals from the brain to the lower muscles of the legs. They also gather sensory information from the lower extremities and send this information to the brain. Hence, when the sciatic nerve is unable to function properly, these operations are compromised, and symptoms such as muscle weakness or numbness occur.
This type of pain is known as radiculopathy, a term that refers to pain that travels down the path of a single spinal nerve root. In order to alleviate the symptoms of sciatica, compression on the nerve roots or on the sciatic nerve itself, must be addressed.