The term sciatica is not a medical diagnoses per se but the term for a collection of symptoms due to compression of the sciatic nerve or its nerve roots. The symptoms can include pain in the lower back that radiates (spreads) into the buttock, the back of the thigh and calf and sometimes the foot. In addition to pain unusual sensations of tingling and numbness may be felt in the same areas. The spinal cord runs within the spine from the base of the skull to the lower back. At each vertebrae a pair of nerves roots exit on both the left and right hand side. The nerve roots are numbered according to which level of the spine they emerge from. The sciatic nerve roots originate from the lower back at the levels L4, L5, S1, S2 and S3, passes through the lumboscaral plexus (a nerve network) and then combine to form a large thick nerve that passes through the buttock and runs down the back of the leg to the back of the knee. This nerve sends and receives information from the hip joint, the muscles on the back of the thigh (hamstrings), the skin down the back of the leg and gives of branches that supply all the structures of the leg and foot from the knee down.
Sciatica most commonly affects people between the age of 30 and 50 and can begin either suddenly due to a traumatic event or can develop slowly as a result of wear and tear of the lower back or tension of the muscles in the buttock and leg.
Causes of Sciatica
- Herniation of Lumbar disc (Slipped disc in lower back)
- Degeneration of lumbar disc
- Spinal stenosis
- Spondylolisthesis
- Piriformis syndrome
Herniation of lumbar disc
The spine consists of a serious of individual bones – the verterbrae separated by discs. A disc herniation (slipped disc) occurs when the gel like core (nucleus pulposus) is forced outwards through the surrounding fibrous annulus fibrosus. When a herniation occurs at the very bottom of the spine the gel like core of the disc can press onto the roots of the sciatic nerve causing sciatica. A herniation can be due to either a sudden traumatic event or occur slowly over time due to repetitive strain. The pinching of the nerve root is called a radiculopathy and is the most common cause of sciatica.
Degeneration of Lumbar Disc
As we grow older the discs degrade and lose their strength and shock absorbing capabilities. In the early stages of degeneration the disc behave like a flat tyre and excessive movement occurs at corresponding level of the spine which can pinch the sciatic nerve roots. Later on the disc can become flattend and frayed and also pinch the sciatic nerve roots.
Spinal stenosis
The spinal cord runs within the spine through the spinal canal. Spinal stenosis is defined as a narrowing of the spinal canal due to degenerative changes and is common amongst the 60+ age group. Degenerative changes include bony overgrowths, bulging discs, swollen soft tissues and enlarged spinal facet joints that can all compress the sciatic nerve roots causing sciatica.
Spondylolithesis
A spondylolisthesis is defined as the forward slippage of one vertebrae upon another. This most commonly occurs at the very base of the back and can cause compression of the sciatic nerve roots and therefore cause sciatica.
Piriformis syndrome
The sciatic nerve passes through or close to the piriformis muscle in the buttock. This small triangular muscle runs from the sacrum to the top of the thigh bone and is responsible for turning the leg outwards (externally rotating the leg). Excessive tension in this muscle can compress the sciatic nerve itself and cause sciatica. Piriformis syndrome is sometime called “wallet sciatica” as a wallet carried in the back pocket can compress the muscles in the buttocks and in turn pinch the sciatic nerve in the sitting position.
Symptoms of Sciatica
Sciatica usually affects people in the 30-50 age group and the severity and longevity of sciatica symptoms are variable, from severe and long lasting to mild, intermittent and short lived. Episodes of sciatica usually last for 2-12 weeks. Symptoms are usually one sided and include:
- Pain in the lower back, buttock, back of the thigh and calf and foot
- Burning, pins and needles or numbness in the same area
- Weakness and loss of full control of the leg
- Pain often aggravated by sitting
Symptoms that require urgent medical attention
If you experience
- Urinary or faecal incontinence
- Loss on sensation around the genitals, inner thighs
- Weakness throughout the legs
This is indicative of compression of the cauda equina and medical attention should be sought urgently.
Self help for sciatica
Professional help needs to be sought in order to ascertain the underlying cause of the individual case of sciatica in order to direct self help activities.
Sciatica treatment
We can:
- Take a case history and perform special tests to identify underlying cause of sciatica
- Improve mechanics of lower back to take the strain off the problem thus accelerating recovery
- Prescribe exercises to gently stretch and strengthen the back to provide a better healing environment and speed up recovery
- Massage and stretches to release the piriformis or other muscles that may be pinching the sciatic nerve to relieve symptoms
- Referral for steroid injection or surgery if above conservative treatment fails
