Making the Diagnosis
Your doctor can usually diagnose neuropathy from the pattern of symptoms
and the neurological examination. Electromyography (EMG), a technique
that measures electrical activity in the muscles, may provide more information
about the neuropathy. In this technique, small needles are put into the muscle.
Every time the muscle contracts, it creates electricity. The electrical signals
are recorded as spikes on a screen and are also played back as sound. People
with neuropathy have abnormal electrical activity in their muscles because of
the damaged nerves that control those muscles. Nerve conduction studies can
also be used. They measure how quickly electrical signals travel through the
nerves that control movement (motor nerves) or sensation (sensory
nerves).
It's also important for the doctor to find out what is causing the neuropathy.
Blood tests can sometimes tell if it's due to metal poisoning, diabetes,
a vitamin deficiency, kidney failure, or a genetic disease. Urine tests may
diagnose heavy metal poisoning or cancer. Unfortunately, none of these tests
can diagnose Guillain-Barré syndrome. In suspected Guillain-Barré
syndrome patients, lab tests are done mainly to rule out other possible diseases.
Sometimes a small amount of spinal fluid is removed through a very fine needle
(lumbar puncture) to look for increased amounts of protein or abnormal cells.