Origins of the sciatic nerve
Like a telephone cable that is made up of phone lines from many homes, the sciatic nerve is made up of five different nerves in the low back that combine together in the mid-buttock. The sciatic nerve runs from the back, under the buttock, and downward through the hip area into each leg.
Sciatica is a term which refers to a burning, stinging, and/or numbing pain that is felt along the course of the sciatic nerve.
It is possible to have sciatica without any low back pain, and having low back pain does not mean you have sciatica.
Sciatica is caused either by irritation of the sciatic nerve, or by irritation of one of the nerves that make up the sciatic nerve. Irritation of these delicate nerve roots may only cause lower back pain, or it may also ‘ignite’ the entire sciatica nerve into a pain state!
Several different types of spinal disorders can lead to compression and irritation of the spine nerve roots that lead to the sciatic nerve. The six most common are: bulging/herniated disc; lumbar spine stenosis; spondylolisthesisl trauma; piriformis syndrome; and spinal tumors.
Lumbar bulging or herniated disc
It is common to compare the anatomy of a disc to a jelly doughnut. There is an inner gel like core (Nucleus Pulposus) that is held in place by a surrounding fibrous outer wall (Annulus Fibrosus). A bulging disc is when the gel-like center remains contained within the outer wall of the disc. A herniated disc occurs when the nucleus breaks through the wall of the annulus.
When a disc bulges, the bulging disc can compress delicate nerve root tissue and cause sciatica. The consequences of a herniated disc are worse. Not only does the herniated nucleus cause direct compression of the nerve root, but the disc material itself causes chemical irritation.
Lumbar spinal stenosis
Between the vertebral bones that make up the spine are openings called foramen. The foramen are the doorway for the nerves to exit the spine to travel to the rest of the body.
When these passageways become narrow or clogged causing nerve compression, the term foraminal stenosis is used.
This condition most often affects older individuals. The pain is usually brought on by activities such as standing or walking and relieved by sitting down.
Spondylolisthesis is characterized by one vertebra slipping forward over an adjacent vertebra. Since the spinal nerves exit the spine by the doorways between the vertebra (foramen), this slippage slams the door shut! This displacement can cause spinal nerve compression and often causes sciatic leg pain.
Sciatica can result from direct nerve compression caused by external forces to the lumbar or sacral spinal nerve roots. The impact may injure the nerves or occasionally fragments of broken bone may compress the nerves.
Piriformis syndrome is named for the piriformis muscle and the pain caused when this muscle compresses the sciatic nerve.
The piriformis muscle is located in the buttock, and is directly about the sciatic nerve. In fact, up to 10% of the population has an anatomical variant were the sciatic nerve travels through the piriformis muscle. Piriformis syndrome develops when muscle spasms develop in the piriformis muscle thereby compressing and irritating the sciatic nerve.
It can mimic sciatica due to a disc herniation. Piriformis syndrome will not show up on X-ray or MRI.
Spinal tumors are abnormal growths that are either benign or malignant. Fortunately, spinal tumors are rare. However, when a spinal tumor develops in the lumbar region, there is a risk for sciatica to develop as a result of nerve compression.
If you think you may be suffering from sciatica, contact your chiropractor. The first step toward relieving pain is a proper diagnosis.