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Home > Patients & Visitors > Health Library > Nerve Function Tests for Evaluating Low Back Problems
The nerves that carry messages to and from your legs come from your
low back. By checking your muscle strength, your reflexes, and your
sensation (feeling), your doctor can tell whether there is pressure on a
nerve root coming from your spinal column. He or she
can often also tell which nerve root is involved.
Muscle strength tests can detect true muscle weakness, which is one
sign of pressure on a nerve root. (Sometimes leg weakness is actually due to
pain, not pressure on a nerve.) Most people who have
herniated discs that cause symptoms also have some
nerve root compression.
Specific muscles receive impulses from specific nerves, so finding
out which muscles are weak shows your doctor where nerve roots are being
See a picture of the
lumbosacral region, from which nerve root compression
Muscle strength tests include:
Just as your muscles receive signals through certain nerves, other
nerves carry signals back to your spinal cord from specific sections of your
skin and other tissues. Testing your sense of feeling helps your doctor find
out what nerve root may be compressed.
Your sense of feeling may be tested in several ways. Your doctor will
probably ask you to close your eyes during this testing, because it's easy to
imagine the feeling if you can see the test being done. Testing may include
touching your skin lightly with a cotton ball or pricking your skin lightly
with a pin.
Tendons attach the muscles to the bones. Reflexes are little movements of the muscle when the tendon is tapped. A reflex can be decreased or absent if there is a problem with the nerve supply. To test your reflexes, your doctor will use a rubber hammer to tap firmly on the tendon. If
certain reflexes are decreased or absent, it will show what nerve might be
compressed. Not all nerve roots have a reflex associated with
December 14, 2011
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Robert B. Keller, MD - Orthopedics
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