Stenosis
is defined as narrowing. The term is commonly applied
to spinal anatomy to describe an abnormal reduction
in size of the various structures, which transmit nerves.
For example, spinal stenosis refers to an abnormal
narrowing of the spinal canal (Anatomy
fig.2) which holds the spinal cord or the nerves,
which flow from it in the low back (cauda equina).
Compression of the nerves as they pass through this
narrowing causes arm or leg symptoms such as numbness,
weakness, or pain. Symptoms from spinal stenosis, which
occur with activity, are defined as neurogenic claudication.
 Spinal
stenosis can be divided into two major categories:
congenital or degenerative (acquired). Congenital
spinal stenosis occurs because of abnormal formation
of one or various components of the spine which through
abnormal growth produces canal narrowing. This type
of stenosis is found inpatients with short stature.
Degenerative
stenosis is more common than congenital stenosis
and is found in older individuals. Age related changes
of the spine such as disc degeneration and arthritis
causes bone buildup in and around the canal and nerve
holes producing nerve compression. (Anatomy
fig.6). Because bone buildup occurs in areas
of the spine with high mobility, it is commonly found
in the neck and low back, and rarely found in the
thoracic spine.
Because
nerve compression from spinal stenosis occurs over
time, characteristically the symptoms are insidious
and rarely occur acutely with for example, an identifiable
traumatic event. The patient may notice that over
weeks or months he or she has noticed that with walking
the legs become tired or numb. The symptoms are not
quickly relieved with rest as is common with claudication
secondary to poor blood flow in the legs. Changes
in position of the spine can affect symptoms quickly-for
example, many patients admit that when they lean
on a shopping cart, the tiredness in their legs improves.
Forward flexion of the spine produces widening of
the spinal canal and nerve holes which relieves pressure
on the nerves and decreases symptoms.
 As
with most spinal problems, conservative measures
are useful to alleviate symptoms in the early stages
of the problem. Physical therapy may improve muscle
tone and fitness, but ultimately will not reverse
the narrowing and nerve compression, which is the
primary problem. During epidural injections, a needle
is introduced into the spine at or near the narrowing
and cortisone is placed on the nerves. The anti-inflammatory
effect of the steroids may reduce nerve swelling.
If the nerve swelling decreases, the relative relationship
of the nerve diameter to the bony hole becomes favorable,
thereby reducing symptoms. Traditionally, three epidurals
per year can be performed.
If
the symptoms become refractory to conservative treatments,
then surgery is indicated. Removal of bony narrowing
around nerves is called decompression. The operative
strategy will depend not only on the location of
the spinal narrowing, but the relative stability
and condition of the spine as a whole. If the stenosis
is associated with a spondylolisthesis,
then a fusion may have to be performed with the nerve
decompression. Curvature, or scoliosis of the spine,
may also complicate that treatment in that bony narrowing
relieved with surgery may recur quickly in a curved
spine because of asymmetric collapse on the concavity
of the curve. Stabilization may have to accompany
the decompression in these cases for long term and
sustained good results after surgery.
Decompression
can be done a number of ways. The most popular techniques
are laminectomy and laminotomy. Click on laminectomy or laminotomy for
explanations of these procedures. Every patient's
surgical treatment should be individualized according
to his or her anatomy and presentation.
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