The lumbar spine consists of 5 vertebral bodies. Nerves emerging from the spinal cord, leave the spine through these vertebrae. Inside the spine is a ring-shaped canal, which the nerves pass through. The narrowing of this canal leads to nerve compressions. And this is called lumbar spinal stenosis. It may occur in the cervical or lumbar vertebrae. It is a process, which develops due to the instability and hypermobility of the spinal joints (aka facet joints), as a result of intervertebral disc degeneration. As a result of the growth in the facet joints, the canal narrows in diameter and the nerves are compressed. Venous congestion and increased pressure emerges around the nerve. This causes the typical gait we call neurogenic claudication.
How Does It Occur Spinal Stenosis?
It has two types, which are congenital and acquired. But spinal shift with both congenital and degenerative spinal stenosis, also has types such as iatrogenic and post-traumatic. The most common type is caused by degenerative arthritis of the spine. In this arthritis, the cartilage tissue gets thinner and the joint capsule loosens. Mobility increases and osteophytes form. Even though the osteophytes restrict the movement of the mobile segment, the facet joint narrows the spinal canal. It is most commonly seen at the L4-5 level.
Spinal stenosis, can be separated into two forms, as central and lateral. In central stenosis, the dura and neural elements inside are compressed; whereas in the the lateral form, nerve roots are especially compressed in nerve exit holes called foramen. Foraminal height normally ranges from 20-23 mm. As for in canal stenosis, this range comes below 15 mm. The compression of neural vessels and nerves, venous congestion, and neuronal arterial ischemia, causes neurogenic claudication in patients.
What Symptoms of lumbar spinal stenosis?
In the degenerative type, symptoms begin to appear after the age of 50. It is more often in women than in men. In patients with canal stenosis in the lumbar spine, canal stenosis of the cervical spine can also be seen. Physical and clinical findings do not develop abruptly. Low back pain and leg pain (sciatica) are seen in 95% of the patients; as neurogenic claudication is seen in 91% of the patients. Neurogenic claudication usually affects both legs. Pain propagation depends on the region of the affected nerve. Leaning forward, sitting, and lying down reduces pain; whereas, standing for a long time and bending the waist backwards increases the complaints. In the later stages of the disease, sitting and lying down stops helping reduce pain. Pain also doesn't go away by resting, and urinary incontinence may occur. Neurologic examination is usually normal. But, the complaint of pain appearing when the patient walks, is diagnostic. A while after the patient is asked to walk, the pain starts to intensify and the patient prefers to walk tilted forward. When asked to sit down, the pain starts to diminish. Such an observation is very typical for these types of patients.
How Is It Diagnosed of Spinal Stenosis?
The diagnosis is easily made by measuring the diameter of the canal in Tomography or MR axial imaging. If the diameter of the canal is under 10 mm, it is definitive stenosis; and if the diameter is between 10-13 mm, it is called relative stenosis. The normal canal diameter is greater than 11.5 mm. Symptoms are not always associated with the canal diameter. The degree of the damage to the neural tissues is what is important. Height loss in the disc space or osteophytes may be seen in plain radiographs. Spinal shift may be determined.
Treatment Spinal Stenosis
Symptoms usually respond to conservative treatment. Even if the patient has low back pain, leg pain, and neurogenic claudication, conservative treatment is effective in most patients. Complaints usually wear off after initial treatments; such as baseline pain relievers, cold and heat therapies, epidural injections, physiotherapy, and bed rest. Back surgery is recommended if the pain is persistent. Power loss is the most important indicator that the patient is a candidate for surgery.
Surgical Treatment of Lumbar Spinal Stenosis
The diameter of the canal may be expanded by performing decompressive laminotomy or laminectomy. Fusion (using spinal implants) may or may not be done according to the surgeon's preference.