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At each vertebral level, a pair of nerves
exit the spinal canal on the right and left sides. These nerves carry signal
away from the spinal cord to activate muscles, and carry information toward
the brain about sensation, including pain sensation. The nerves can become
irritated anywhere in their course.
Chronic pressure, or entrapment, can cause irritation to the nerve that will
cause it to produce severe pain. This is what happens when someone has a
disc herniation, or "slipped" disc. Sometimes it is necessary to identify
exactly what nerve root is conducting the pain impulses.
A technique for accomplishing this is
called a selective nerve block. Under X-ray control, the physician places a
needle close to a specific nerve and injects a very small amount of
medication, including local anesthetic. The patient then observes whether
their typical pain is relieved or not. This technique can be very useful in
resolving complex diagnostic problems.
(photo show model of nerves exiting spinal
column)
This procedure involves injecting a therapeutic steroid and local anesthetic
into the sheath surrounding the nerve root. This is done to decrease
inflammation and your pain temporarily and to define it more precisely. Pain
relief from this injection may vary from minimal to long term, depending on
the specific symptoms.
This procedure will take 15-30 minutes per level. You will remain awake
throughout the test. You will be asked to lie in a prone position (face
down) on a table in the fluoroscopy suite. Your back will be cleansed with
an antiseptic (usually iodine) solution and the area will be numbed. The
radiologist will use fluoroscopy (x-ray) to guide the placement of a thin
needle to the area of the nerve that causes pain. After correct needle
placement is confirmed by x-rays, a small amount of local anesthetic and
steroid will be injected. During the injection, you may feel pressure or
pain.
Due to the effects of certain medications, your driving reflexes may be
impaired. You will need someone to drive you home after the procedure.
Please make the necessary arrangements.
PLEASE NOTIFY A TECHNOLOGIST IF THERE IS A CHANCE THAT YOU
MAY BE PREGNANT !
FREQUENTLY ASKED QUESTIONS
Q. Why is a Selective Nerve Block performed?
A. A selective nerve block may be performed to help diagnose and/or
treat radicular pain (pain related to irritation and inflammation of a nerve
serving a particular area of the body). You may need these injections to
decrease your pain so that appropriate physical therapy and exercises can be
performed for your long-term treatment. Also the nerve blocks allow
identification of target sites to direct future care.
Q. Are there any special preparations / restrictions?
A. Ideally, blood thinners should be stopped 48-72 hours prior to the
procedure and any pain medications should be stopped 8 hours prior to the
test. You should not have anything to eat or drink after midnight the night
before the procedure unless otherwise instructed by your physician. You will
not be able to drive home after your procedure.
Q. How will I feel after the procedure?
A. You may experience numbness and/or relief from your symptoms for up
to 6 hours after the injection. Your usual symptoms may then return and may
possibly be worse than usual for a day or two.
Q. When will the pain relief medication take effect?
A. It may take 3-7 days before you will be able to feel any effects from
the medication. If there is no change in your symptoms after 2 weeks, your
doctor may want to investigate other possible sources for your pain.
Q. Are there any side effects?
A. Possible side effects of the steroid medications include headaches,
mild fluid retention, increased blood sugar levels, hiccups, flushing,
palpitations, difficulty sleeping. These side effects occur in only about 5%
of patients and commonly disappear within 1-3 days after the injection.
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