What is lumbar stenosis?

Lumbar spinal canal stenosis is characterized by the narrowing of the central space in the spine that contains the nerve roots in the lumbar region, which consists of 5 of the 33 vertebrae in the spinal column.

The reduction in the diameter of the spinal canal, caused by the enlargement of bony structures and ligaments—a process known as hypertrophy—leads to compression of the lumbar nerve structures and may result in various symptoms.

Types

Lumbar stenosis can be divided into primary (congenital), which is rare and affects about 9% of patients, or secondary (acquired), which is related to the thickening of the structures surrounding the dural sac. This form is frequently observed in patients over the age of 50 and is the most common cause of spinal surgery in individuals over 60.

The five lumbar vertebrae are numbered L1 to L5, and the intervertebral spaces where the discs are located are referred to as L1-2, L2-3, L3-4, etc. The L3-4 and L4-5 spaces are the most commonly affected sites of stenosis.

Lumbar stenosis can also be classified based on the location of the narrowing, either in the center of the spinal canal (central stenosis) or in the lateral (foraminal) space, which is the bony passage through which the nerve roots exit the spine toward the legs.

Symptoms

Lumbar stenosis presents symptoms depending on the location of neural tissue compression. There may be lower back pain, as well as pain and discomfort when standing, especially when the spine is extended, such as when walking. Typically, symptoms disappear or lessen when the patient sits down for a few minutes.

The dynamic nature of lumbar stenosis explains this characteristic well. In the upright (standing) position, the spinal canal naturally narrows due to the posture and curvature of the spine. In contrast, when sitting, the spinal canal widens, which helps relieve symptoms.

As a slowly progressive degenerative disease, the symptoms also tend to progress gradually. Initially, patients may experience difficulty walking long distances, without pain while resting, which over time evolves into pain during increasingly shorter walks, until even standing becomes severely limited by pain.

In more severe cases, a set of signs and symptoms may appear that are part of cauda equina syndrome, which is considered a medical emergency and will be addressed in a separate text.

Causes

Degeneration of the spinal column is directly associated with the natural aging process of the human body. Its incidence increases in proportion to the rising life expectancy of the population. In a healthy spine, its structures — vertebrae, intervertebral discs, joints, ligaments, and muscles — work synchronously to absorb and distribute loads, while also allowing mobility between segments.

Over time, essential components for these functions, such as collagen and water, undergo changes in their proportions within the tissues, affecting the biomechanical properties of the spine. As a result, in addition to an increased risk of disc protrusions and herniations, the tissues surrounding the dura mater and nerve roots — especially the ligamentum flavum and facet joints — tend to enlarge and hypertrophy, occupying previously free spaces and compressing nerve structures.

Lumbar stenosis is a dynamic condition, meaning it depends on the position of the lumbar spine. In extension, such as when standing, the spinal canal naturally narrows due to the posture and curvature of the spine. On the other hand, when sitting, the spinal canal “opens” as a result of lumbar straightening. This explains much of the symptoms and why many patients are able to perform long and intense activities like cycling while seated, but cannot walk short distances when standing upright.

Diagnosis

The diagnosis of lumbar stenosis should follow a thorough clinical evaluation, primarily considering the patient’s complaints and the physical examination, which is essential for guiding complementary tests. Magnetic resonance imaging (MRI) is the main complementary exam in these cases, as it not only shows the location and possible causes of the stenosis but also provides a comprehensive assessment of the tissues surrounding the spine. However, dynamic X-rays (which assess the spine while standing under the influence of gravity and in different positions) and computed tomography (CT) can also be very useful.

Some conditions may present with symptoms very similar to those of lumbar stenosis. These include vascular claudication (blockage of the arteries in the legs), peripheral neuropathies, and osteoarthritis of other joints such as the hips and knees. These differential diagnoses must be ruled out or identified through a careful evaluation of the patient.

Treatment

The treatment plan should be individualized for each patient based on their symptoms. Except in emergency cases involving acute and/or progressive neurological deficits — such as significant muscle weakness or sphincter dysfunction (loss of bladder or bowel control) — the initial approach should be as non-invasive as possible, using conservative measures such as physical therapy, hydrotherapy, acupuncture, and medication.

Patients who continue to experience persistent pain and/or functional limitations, such as reduced mobility and independence, may be candidates for surgical treatment. This typically involves decompression of the spinal canal and foramina, relieving pressure on the neural tissues. In a minority of cases, this procedure may be combined with spinal fusion (arthrodesis).

Prevention

There is currently no scientific evidence in the medical literature supporting specific measures to prevent the development of spinal canal stenosis. However, maintaining lumbar and abdominal muscle balance and tone through regular practice of targeted exercises helps prevent mechanical overload of spinal structures, thereby reducing symptoms of pain in the lower back and the spine as a whole.

By Einstein Editorial Board