Spinal stenosis or narrow lumbar canal

Definition

Stenosis of the lumbar canal (or "lumbar narrowed canal") is a degenerative disorder, occurring most often in the elderly or middle aged, after 50 years. It is also, and improperly, called "narrow lumbar canal". The lumbar spinal stenosis discovered in the elderly or old age is most often the result of the combination of the two pathologies: the congenital narrowness of the lumbar canal, which is decompensated over time by the anatomical changes caused by osteoarthritis, which achieves a narrow lumbar canal "narrowed". Osteoarthritis causes cartilage thinning and sagging intervertebral discs, causing contact between the bone surfaces and reaction thickening of the vertebral bone. The degeneration of the joints also causes ligament thickening, including yellow ligaments, which close the spinal canal.  These morphological changes in the vertebrae, discs, posterior intervertebral joints and ligaments encroach on the intra-canal space normally reserved for the dural sheath and the nerves of the ponytail. It follows naturally compression of these nerve elements, which causes pain in the lower back, buttocks and lower limbs, then sensory disorders and motor disorders.

Symptoms

Intermittent claudication

It is the specific symptom. These are patients complaining of unilateral or bilateral radiculalgia, with or without paresthesia or weakness of the lower limbs, appearing on the move immediately or after a certain time. These symptoms increase gradually, if walking continues, forcing the patient to stop. Leaning forward or sitting down relieves him quickly. At rest, the patient does not suffer, but low back pain is possible.

In less severe cases, intermittent claudication may be replaced by simple exercise radiculalgia. It is a pain of effort that does not force the patient to stop. Intermittent claudication is more common in central stenoses.

Physical signs

The clinical examination is not specific. The analgesic lateral inflection of the spine, very common in discopathy, is rare in stenoses.

Neurological signs:

The suffering of several roots is usual in the canal stenosis. Disorders of sensitivity often cover several territories. The abolition or frank reduction of Achilles and / or patella reflexes is usual. Motor disorders are rare and generally unobtrusive. The analysis of neurological signs should be done at rest and after exercise, motor disorders in particular may appear after walking.

Differential diagnosis

The most common differential diagnosis is vascular claudication. The latter occurs after a longer walking distance and usually starts at the calf to reach progressively by raising the entire lower limb. Classically, neurogenic claudication is more pronounced on descent because it forces the patient to reduce lumbar flexion. Vascular claudication, on the other hand, manifests itself more readily on the ascent.
Low back pain and projected pain related to disc and joint degeneration can appear when walking and disappear at rest, simulating a claudication.
Peripheral neuropathies, regardless of their etiology, can manifest as an exacerbation of symptoms during exercise or walking.
Coxopathies are often expressed by walking pain, disappearing at rest and whose topography can simulate crural and / or sciatic radiculalgia.

Diagnostic

It is based on clinical examination (see symptoms) and on radiological examinations:

• X-rays is irrelevant apart from the finding of a degenerative spondylolisthesis which is accompanied almost invariably by ductal narrowing. One will retain the too visible aspect of the joint space posterior on the front view of face and the brevity of the pedicels of profile, two inconstant signs.
• The CT-scan remains the simplest screening test. When a narrow channel is suspected, cuts should be made for each lumbar floor from L1 to S1.
• MRI allows, thanks to T2 sequences, to obtain myelographic images without injection. The determination of bone contours and stenosis is less good than with CT, but soft tissue is better defined. It will be systematically requested before surgery.
• Myelography is an examination that remains useful for the search for a dynamic stenosis. Usually, it is in extension of the lumbar spine that the stenosis increases. Rarely, when there is instability, the stenosis is increased in flexion. In some cases, the combination of myelography and scanner makes it possible to define the compression elements even more precisely.  This exam is particularly interesting in patient with multiple surgical procedure.
• The electromyogram sometimes makes it possible to objectify the root lesion and its topography. Its specificity is nevertheless low (20-40% depending on the series). This examination is only recommended in cases where there is no clear correlation between the clinic and the imaging. It can also be performed prognostically in case of surgical treatment (the worst results occurring in patients with normal EMG).

Treatment

As a first step, the treatment must be medical and conservative: drugs like NSAIDs and analgesics associated or not with the reeducation (physiotherapy, balneotherapy ...); infiltrations are possible, simple (epidural) or radioguidated. It is always through a purely medical treatment that we must begin.
We will always operate in the 3 cases: paralyzing sciatica, syndrome of the ponytail causing disorders to urinate,  hyperalgesic  sciatica  and resistant to medical treatment.
It will consist in a release of the medullary canal of the elements which stenoses it (the bone of the blades and articular, the joint capsule, the yellow ligamentum , and a herniated disk if present). A "laminectomy" is then performed (the blade is removed) with "partial arthrectomy" (part of the articular mass is removed), associated if necessary with a spinal "arthrodesis" (material is placed: screws and plates most often associated with a bone graft) in case of deformed or highly mobile spine, posterior articular pain. Several vertebral stages may be involved.