Sciatica is a disorder involving pain in the buttock that may radiate down the leg and is characterized by:
- Deep, sharp pain in the buttock and/or leg that is worse when sitting and bending forward at the waist
- Sometimes accompanied by lower back pain
- Burning or tingling sensation down the leg and sometimes foot
- Weakness, numbness, or difficulty moving the leg or foot
- Constant or intermittent symptoms
WHAT CAUSES SCIATICA?
Sciatica is caused by compression of the sciatic nerve or neurons that comprise the sciatic nerve. The neurons (individual nerve cells) originate in the brain and travel down the spinal cord; branch out from between the lumbar vertebrae and sacrum as nerve roots and finally combine in the buttock region to form the sciatic nerve.
This means that compression of nerve tissue anywhere along this path is capable of producing sciatica. In fact, although rare, brain tumors can produce sciatica symptoms.
The three most common compression sites for sciatica are in the central canal of the lumbar region of the spinal column, the lateral canals, and under the piriformis muscle of the pelvis.
Central canal stenosis
Stenosis, or narrowing of a spinal canal is often the source of compression especially in older patients. Stenosis occurs with degenerative joint disease, where bone spurs occlude the canal, pinching or rubbing against nerve tissue, as shown in the model above. This is the top view of an L4 vertebra , showing narrowing of the central canal due to spondylosis, or vertebral bone degeneration. Notice how the bone contacts the nerves (yellow structure in the canal). This contact fires the nerves, causing shooting pain and/or numbness and tingling down the legs.
Thickened ligaments can also be a source of stenosis. For a person with stenosis, bending the spine in certain directions may exacerbate or alleviate sciatica.
A bulging disc can also cause stenosis and produce sciatica by narrowing the lateral canal and pressing against a nerve root. This is also called lumbar radiculopathy.
Piriformis syndrome is a less common form of sciatica and occurs when the sciatic nerve is pinched by the piriformis muscle, a deep pelvic muscle that externally rotates the hip.
Rare, red flag causes of sciatica are brain tumors, spinal tumors and pelvic masses; and maybe even viral infections of the sciatic nerve. Check with your doctor to make sure none of these apply to you.
Seek immediate medical attention if you have progressive lower extremity weakness and/or loss of bladder or bowel control.
DIAGNOSING SCIATICA
Sciatica from spinal stenosis is diagnosed by X-ray or lumbar MRI. Simple muscle strength and sensory nerve tests can be done to determine if the nerve is not functioning 100%. But basically, if you have nerve pain down your leg, it is fair to assume the nerve is compromised somewhere.
If you know the source of your sciatica after being diagnosed and informed by your doctor, you should have a better idea of your prognosis, or chance of eliminating it.
If you aren’t able to see a doctor for your condition for whatever reason, asking yourself a few questions may help you identify what is causing your sciatica:
- Did you experience sharp, low back pain at the same time as your sciatica? If so, this points to lumbar radiculopathy (sciatica from nerve root compression) by lumbar disc herniation.
- Are you over 50, had a heavy labor job most of your life; have a history of accidents or injuries to your spine or engaged in a high impact sport for many years? If so, this points to central or lateral canal stenosis from degenerative joint disease of the spine.
- Do you sit long hours and/or do squats or other activities that strain the buttock muscles? If so, this points to sciatica from piriformis syndrome.
These aren’t definitive assessments, of course.
The likelihood of being able to self-resolve sciatica depends on what is causing it:
Sciatica caused by central canal stenosis from degenerative joint disease has the worst prognosis. These cases eventually require spinal decompression surgery.
Sciatica caused by lateral canal stenosis has a better chance of recovery. Certain exercises and manual procedures may be able to widen the opening and remove pressure from the nerve root.
Sciatica caused by piriformis syndrome has the best chance of recovery. Manual techniques such as stretching, posture correction and hip mobilization can often correct the problem.
