Lumbar Spinal Stenosis
What is the anatomy of the lumbar spine?
What is stenosis of the lumbar spine?
Stenosis of the lumbar spine refers to narrowing of the canal in the lumbar spine through which the nerves travel. Rather than the nerves having space and being surrounded by CSF (or spinal fluid) the nerves are essentially squashed together. The degree of spinal stenosis can vary from being mild to severe.
The cause of the stenosis varies. In the majority of cases, it is an accumulation of degenerative or wear and tear changes that narrows the spinal canal from each side. It typically occurs at the level of each disc and may involve multiple levels as well. In most degenerative cases, it is due to a broad bulge of the intervertebral disc, thickening of the ligaments in the spine (ligamentum flavum) and overgrowth of the facet joints on each side due to arthritic change. This normally progresses slowly over time and may be associated with the gradual onset of symptoms.
Other potential causes include a large central disc protrusion that may compress all of the nerves passing by that disc in the lumbar spine. Synovial cysts, which are pockets of degenerative material that originates from the facet joints on each side and which protrude into the spinal canal, may also cause stenosis.
What are the symptoms of stenosis?
The most common symptom of lumbar spinal stenosis is termed neurogenic claudication. This means pain, pins and needles or numbness that occurs in one or both legs that typically occur with standing in the one spot or walking for a distance. The distance may become shorter and shorter over time until the symptoms occur even at rest which is a concerning sign. The symptoms of neurogenic claudication are usually relieved by sitting for a period before the person can stand or walk for a similar distance again.
In some cases, spinal stenosis affects only one nerve in particular in which case it causes a ‘pinched nerve’ or radiculopathy. This type of pain is commonly referred to as sciatica.
If lumbar stenosis is more severe, it may cause a condition known as cauda equina syndrome which is where multiple nerve roots in the lumbar spine are compressed so as to cause weakness of the lower limbs, numbness in the areas around the perineum, that is the anus and genitals, as well as bladder and bowel dysfunction and incontinence. When this occurs, it requires urgent neurosurgical treatment.
What are the treatment options for lumbar canal stenosis?
The options depend on the nature and severity of symptoms. Patients with weakness, bladder / bowel dysfunction, or other features of cauda equina syndrome require urgent surgery to relieve the pressure on the nerve roots.
When symptoms are mild, then conservative management such as physiotherapy may be appropriate. Cortisone injections are often used but their effectiveness in the setting of spinal stenosis may be limited as the main issue is usually mechanical compression rather than inflammation. Cortisone will not relieve the mechanical compression of the nerve roots.
If the symptoms are significant for the patient in terms of their day-do-day life and function, then surgery may be appropriate. Depending on the underlying cause of the stenosis, surgery is usually in the form of a laminectomy with or without discectomy. This procedure is a common neurosurgical operation performed through an incision in the skin of the back. The bone covering the nerves, that is the lamina, is removed along with the thickened ligaments. If there is a significant disc protrusion then that may also require removal. Once the nerves are satisfactorily decompressed the incision is closed.
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