Nerve conduction velocity (NCV) is a test of the speed of electrical signals through a nerve.
Alternative NamesNCV
How the test is performedPatches called surface electrodes, similar to those used for ECG, are placed on the skin over nerves at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve.
The nerve's resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to determine the speed of the nerve signals.
Electromyography(recording from needles placed into the muscles) is often done at the same time as this test.
How to prepare for the testNormal body temperature must be maintained (low body temperature slows nerve conduction).
Tell your doctor if you have a cardiac defibrillator or pacemaker, as precautions may need to be taken.
How the test will feelThe impulse may feel like an electric shock. Depending on how strong the stimulus is, you will feel it to varying degrees, and it may be uncomfortable. You should feel no pain once the test is finished.
Often, the nerve conduction test is followed by electromyography (EMG), which involves needles being placed into the muscle and you contracting that muscle. This can be uncomfortable during the test, and you may have muscle soreness after the test at the site of the needles.
Why the test is performedThis test is used to diagnose nerve damage or destruction. Occasionally, the test may be used to evaluate diseases of nerve or muscle, including myopathy, Lambert-Eaton syndrome, or myasthenia gravis.
Normal ValuesNCV is related to the diameter of the nerve and the degree of myelination (the presence of a myelin sheath on the axon) of the nerve. Newborn infants have values that are approximately half that of adults, and adult values are normally reached by age 3 or 4.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results meanMost often, abnormal results are due to some sort of nerve damage or destruction, including:
The nerve damage or destruction may be due to many different conditions, including:
Any peripheral neuropathy can cause abnormal results, as can damage to the spinal cord and disk herniation (herniated nucleus pulposus) with nerve root compression.
What the risks areThere are no risks.
Special considerationsAn NCV test shows the condition of the best surviving nerve fibers, so in some cases the results may be normal even if there is nerve damage.
ReferencesGriggs RC, Jozefowicz RF, Aminoff MJ. Approach to the patient with neurologic disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 418.
A nerve conduction velocity test is a medical procedure used to assess how quickly electrical impulses travel through nerves. It helps diagnose conditions that affect the nervous system, such as nerve damage, neuropathy, and carpal tunnel syndrome, by measuring the speed of nerve signals. The test involves placing electrodes on the skin to stimulate the nerve and recording the response to determine the speed of conduction.
The slowest conduction velocity occurs in unmyelinated C fibers, which are responsible for transmitting dull, aching pain signals in the body. These fibers conduct nerve impulses at a speed of around 0.5 to 2 meters per second.
I believe you're fishing for "resistance" as the answer, but it's not correct to say that it "slows down" conduction. The current that flows in a high-resistance conductor flows just as fast as it does through a copper bar, but in doing so, it loses more energy to the conductor, which shows up as heating of the conductor.
An increase in body temperature can lead to faster conduction speed of electrical impulses in the body due to improved nerve function and reduced resistance in the nerve fibers. Conversely, a decrease in body temperature can slow down conduction speed as nerve function is impaired.
Saltatory conduction refers to the propagation of action potentials along myelinated axons from one node of Ranvier to the next node. It increases the conduction velocity of action potentials.
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It measures the ability of the nerve to conduct electrical signals
velocity proportional to square root of diameter
For unmyelinated nerves there is a relationship between axon diameter and conduction velocity. Larger diameter nerves conduct faster. For myelinated nerves the a larger diameter nerve will conduct faster between the nodes of ranvier where the action potential is propagated. Conduction is said to be saltatoryas it jumps from node to node.
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A nerve conduction velocity test is a medical procedure used to assess how quickly electrical impulses travel through nerves. It helps diagnose conditions that affect the nervous system, such as nerve damage, neuropathy, and carpal tunnel syndrome, by measuring the speed of nerve signals. The test involves placing electrodes on the skin to stimulate the nerve and recording the response to determine the speed of conduction.
Nerve conduction velocity studies are diagnostic tests that measure the speed at which electrical impulses travel along nerves. They help to evaluate nerve damage, identify specific nerve disorders, and determine the extent and location of nerve injury. These tests are commonly used to diagnose conditions like carpal tunnel syndrome, peripheral neuropathy, and nerve injuries.
Heavily myelinated, large diameter fibers
Nerve Conduction Velocity scans costs Rs1500/-What_is_the_cost_of_a_Nerve_Conduction_Test
A nerve conduction velocity test is a diagnostic procedure used to evaluate the function of nerves by measuring how quickly electrical impulses travel along them. It is commonly used to diagnose nerve damage or disorders such as carpal tunnel syndrome or peripheral neuropathy.
Nerve conduction is the same in both directions. The rate of conduction is mediated by the physical properties of the nerve and the voltage sensitive channels so as long as the diameter is constant the spread of the action potential would be the same in either direction.
The factors affecting nerve conduction velocity are as follows:(i) Axon diameter:An axon with a larger diameter conducts faster. In an unmyelinated fiber, the speed of propagation is directly proportional to the square root of the fiber diameter (D), i.e.,Conduction velocity a D(ii) Myelination and saltatory conduction:Myelination speeds up conduction. Thus, the action potential travels electrotonically along the long myelinated segments, and fresh action potentials are generated only at the nodes. This is called saltatory conduction. In a myelinated neuron, the conduction velocity is directly proportional to the fiber diameter (D).(iii) Temperature:A decrease in temperature slows down conduction velocity, (iv) Resting membrane potential. Effect of RMP changes on conduction velocity is quite variable. Usually, any change in the RMP in either direction (hyper polarization or depolarization) slows down the conduction velocity.