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Spinal stenosis is term used to describe a constriction of the spinal cord
or spinal canal nerves by a combination of bone, ligaments, and
bulging or herniated discs. There are two basic types of spinal
stenosis depending on whether the nerves in the spinal canal are
being compressed or whether the nerves exiting the spine are
compressed. The former is known as central spinal stenosis and the
latter is known as foraminal stenosis. It is possible for a person to
have both at the same time.

Central Spinal Stenosis usually occurs in patients in their 60s, 70s, and
80s, although it may occur at any age. It most often occurs in the
lumbar spine, less in the cervical spine, and only rarely in the thoracic
spine. The stenosis is usually of gradual onset and involves a
narrowing of the spinal canal due to bulging discs, thickening and
buckling of the ligaments in the spinal canal, and arthritis of the facet
joints which causes the joints to become much larger with bone
overgrowth. The onset of symptoms are gradual and usually occur
only while walking. Symptoms include weakness or tiredness in the
thighs and/or some aching pain in the thighs and legs which go away
within a few minutes of sitting down, then happen again when the
patient begins walking. Often those with central spinal stenosis will
bend over forwards at the waist during walking. Bending forward or
holding onto a shopping cart while walking enlarges the spinal canal
and takes pressure off the nerves that are being squeezed. Over
time, a person with central spinal stenosis may notice they can walk
less and less distance before experiencing severe pain or weakness.
Ultimately they may be able to walk only a few yards or hundred feet
before they must sit down to alleviate the pain and weakness. Usually
the pain which is experienced is not sharp and it does not transmit to
the feet. Surprisingly, there is often very little back pain in those with
central spinal stenosis. The diagnosis of spinal stenosis cannot be
made with plain xrays. It requires a MRI or CT scan of the spine to
determine spinal stenosis. Typically the lumbar spine
anterior-posterior diameter in the middle of the spine is normally
13-20mm but in spinal stenosis may be as little as 3mm. Generally,
anything less than 10mm is considered spinal stenosis.
Treatment for central spinal stenosis involves epidural steroid
injections and laminectomy surgery when the limitations on walking
become severe. Physical therapy, medications, and exercise do not
help with this condition.

Foraminal stenosis refers to a constriction of the area around the
nerve roots as they exit from the spine. This may be produced by
arthritis of the facet joints, foraminal disc herniations, soft tissue
entrapment (ligaments), etc. Often foraminal stenosis from the
lumbar spine results in leg and foot pain which may depend on the
position of the spine. Since the nerve is entrapped, the nerve may
become inflamed and painful. Epidural transforaminal injections may
be used as a treatment while definitive surgical therapies include
minimally invasive holmium YAG foraminoplasty in which a laser is
placed into the foramen and fired at high wattage resulting in the
vaporization of bone around the nerve root. Other surgical therapies
include open foraminotomy, facetectomy, and other decompression
procedures. Physical therapy and other conservative measures may
help with the symptoms of foraminal stenosis, but the only definitive
treatment is surgical. However, because of the proximity of the nerve
root to the overlying bone, the nerve may be injured during
procedures such as epidural steroid injections or surgery. This may
result in long term weakness to the leg or foot. Also surgery may
produce scar tissue around the nerve which may ultimately worsen the
situation. Therefore surgery is not undertaken lightly due to the
associated risks.