Lumbar canal stenosis is a narrowing of the spinal canal in the lower back. This pathology of degenerative origin causes low back pain as well as pains and disorders of the lower limbs due to the compression of the nerve roots. Linked to aging, it appears most often in people over 50, but similar symptoms can affect young adults born with a narrow spinal canal.

Definition

The spine, or rachis, is formed by 24 vertebrae with holes in the back. Their stacking forms the spinal canal, through which the spinal cord travels.

Lumbar canal stenosis is defined as a narrowing of this cavity at the level of the lumbar vertebrae, located between the last dorsal vertebra and the sacrum and numbered from L1 to L5 from top to bottom. In the lumbar canal, the terminal part of the spinal cord extends into the “ponytail”, a bundle of nerve roots. It is at this level that the innervation of the lower body begins (sciatic and crural nerves, innervation of the pelvis and perineum, etc.).

When the lumbar canal becomes too narrow, nerve roots and small vessels are compressed, resulting in pain and other neurological manifestations.

Causes

With aging, the spine is the site of degenerative processes.

Osteoarthritis is the main cause of the narrowing of the lumbar canal: the wear and tear of the cartilages and the collapse of the inter-vertebral discs results in the reactional formation of bony growths called “parrot beaks” at the joints. There is also the thickening of the ligaments that unite the vertebrae and close the canal.

Other causes can intervene in lumbar stenosis: vertebral slips (degenerative spondylolisthesis), herniated discs, osteoporosis fractures …

Stenosis can appear early in people who inherited a narrow “constitutional” (or congenital) lumbar canal at birth. Initially, it is often localized at the level of the L4 / L5 joint, but can later spread to other floors of the lumbar canal.

Diagnostic

X-rays are used to explore the overall appearance of the spine and to detect slips of the vertebrae.

The diagnosis is based on imaging tests that visualize cross sections of the spine:

• the scanner (computed tomography) can visualize the bone and the lesions of osteoarthritis. It gives a picture of the shape of the lumbar canal, which can be reduced to a simple slit in cases of severe stenosis;
• Complementary, MRI allows the study of nerve structures, intervertebral discs or ligaments.

Saccoradiculography (or CT myelography) may be offered when symptoms only appear when standing. This radiological examination is the only one that can be performed in this position. It is performed after injection of a contrast product into the spinal canal

The electromyogram will, if necessary, allow us to study the electrical activity of the nerves.

The people concerned

In people over 50, spinal stenosis is the leading cause of low back pain and inflammation of the spinal nerves (radiculitis). After 65 years, it is estimated that about one in 1000 people have a narrow or narrowed back canal.

Risk factors

Different pathologies such as hyperparathyroidism, Paget’s disease or ankylosing spondylitis are likely to accentuate the narrowing of the lumbar canal.

The symptoms are mainly related to the compression of the nerve roots, which causes their irritation and inflammation.

Difficulty walking

The gradual onset of difficulty in walking is characteristic of the disease. Over the years, pains and weaknesses in the leg appear after shorter and shorter walking time. People then limp (intermittent neurogenic claudication) and are forced to stop or sit down. Leaning forward can help open up the lumbar canal and improve symptoms.

Root pain

Irradiation of pain along the path of nerves whose roots are compressed is common. These pains can be sciatica (extending from the buttock and the back of the thigh to the calf and the foot) or cruralgia (reaching the front part of the thigh and the leg).

Lower back pain

Lower back pain is often present. Sometimes very disabling, this low back pain is not specific to ductal stenosis but results from the degenerative process affecting the spine.

Other symptoms

• Sensory disorders: numbness, tingling, tingling in the legs …
• Only in severe forms of the disease: loss of feeling, permanent weakness or paralysis of the lower limbs.
• Exceptionally, malfunction of the bladder or anal sphincter resulting from strong compression of the “ponytail”.

Medical treatment

The therapeutic arsenal aims to reduce pain and especially to preserve the autonomy of patients by increasing their walking perimeter. The treatment is based both on drugs (analgesics, anti-inflammatory drugs), on rehabilitation and possibly on external restraint (wearing a lumbar corset). It can be effective for months or even years.

Corticosteroid infiltrations in the spinal cord of corticosteroids may be considered to temporarily calm severe inflammatory pain. 

Surgical treatment

About 10% of patients will be offered conventional or minimally invasive surgery on one or more vertebrae as the disease progresses. This intervention is considered when symptoms worsen and functional discomfort and pain become very debilitating despite medical treatment. 

Different options are possible to free the nerve structures. The surgeon may in particular choose to enlarge the lumbar canal by cutting back on the bone lesions of osteoarthritis or on the thickened ligament.

More complex procedures are sometimes performed. Arthrodesis (an operation consisting in “welding” several vertebrae together) may in particular be necessary in the event of instability or slippage of the vertebrae. 

Re-education

Rehabilitation plays a key role in the treatment of lumbar spinal stenosis. It should aim at strengthening the muscles that stabilize the spine and resuming a certain physical activity, essential to maintaining autonomy.

Massages are ineffective. As for spinal manipulations, they can be dangerous when the spine is fragile. The physiotherapist will therefore focus his intervention on learning correct postures and movements that open the lumbar canal by tilting the pelvis forward while walking.

Exercise cycling is beneficial because the position of the back also promotes the opening of the lumbar canal. Losing weight can help.