What causes slow nerve conduction?
Nerve conduction velocities also tend to decrease as a person gets older. Slower conduction velocities may also be caused by injury or damage to a nerve (such as carpal tunnel syndrome) or group of nerves (such as Guillain-Barré syndrome or post-polio syndrome).
What can affect EMG results?
Electromyography
- Are taking any drugs. Certain drugs that act on the nervous system (such as muscle relaxants) can interfere with electromyography results.
- Have had bleeding problems or are taking blood thinning drugs, such as warfarin (Coumadin®) or heparin.
- Have a pacemaker.
How does EMG detect nerve damage?
Electromyography (EMG) measures muscle response or electrical activity in response to a nerve’s stimulation of the muscle. The test is used to help detect neuromuscular abnormalities. During the test, one or more small needles (also called electrodes) are inserted through the skin into the muscle.
What is a bad EMG?
An abnormal EMG result may be a sign of a muscle or nerve disorder, such as: Polymyositis. This is an inflammatory muscle disease that causes decreased muscle power. Muscular dystrophy. This is a chronic genetic disease that slowly impairs how muscles work.
Can an EMG rule out neuropathy?
EMG and NCS are tests that measure the electrical activity of the muscles and nerves of the body, usually to an arm or a leg. The tests can help identify nerve injury or muscle disease such as carpal tunnel syndrome, a pinched spinal nerve, peripheral neuropathy, myositis, or ALS.
Can EMG results be wrong?
Abnormal EMG results may indicate muscle damage or a problem with the nerves that control the muscle.
Can an EMG rule out ALS?
Nerve conduction studies and needle electromyography (EMG) are useful for confirming the diagnosis of ALS and for excluding peripheral conditions that resemble ALS. Laboratory tests are performed primarily to rule out other disease processes; results generally are normal in ALS.
What are the results of an EMG test?
On the other hand, the muscle may show abnormal electrical activity during contraction. This shows up as an abnormal action potential pattern with changes in the size or shape of the wave. Abnormal EMG results may indicate muscle damage or a problem with the nerves that control the muscle. How Do Doctors Use the EMG Results?
What does an abnormal EMG mean for a muscle?
First, the muscle may show electrical activity at rest. On the other hand, the muscle may show abnormal electrical activity during contraction. This shows up as an abnormal action potential pattern with changes in the size or shape of the wave. Abnormal EMG results may indicate muscle damage or a problem with the nerves that control the muscle.
How does a nerve conduction study ( EMG ) work?
An EMG is a nerve conduction study that evaluates a muscle’s response to the nerve that controls it. It does this by measuring the electrical activity in the muscle at rest, with a slight contraction, and with a forceful contraction. This helps your doctor know whether the problem is in the muscle itself or in the nerves that control the muscle.
How long does it take for nerve damage to show up on EMG?
As noted earlier, it takes between 1 and 4 weeks after a nerve injury before they can be identified. These early denervation potentials will be large in size on the EMG screen. Months later, the fibrillation potentials and positive sharp waves become smaller.