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Nerve conduction velocity test-- A test that measures the time it takes a nerve impulse to travel a specific distance over the nerve after electronic stimulation.
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Nerve conduction velocity?
DefinitionNerve conduction velocity (NCV) is a test of the speed of electrical signals through a nerve.Alternative NamesNCVHow 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:Axonopathy(damage to the long portion of the nerve cell)Conduction block (the impulse is blocked somewhere along the nerve pathway)Demyelination(damage and loss of the fatty insulation surrounding the nerve cell)The nerve damage or destruction may be due to many different conditions, including:Alcoholic neuropathyDiabetic neuropathyNerve effects of uremia (from kidney failure)Traumatic injury to a nerveGuillain-Barre syndromeDiphtheriaCarpal tunnel syndromeBrachial plexopathyCharcot-Marie-Tooth disease (hereditary)Chronic inflammatory polyneuropathyCommon peroneal nerve dysfunctionDistal median nerve dysfunctionFemoral nerve dysfunctionFriedreich's ataxiaGeneral paresisMononeuritis multiplexPrimary amyloidosisRadial nerve dysfunctionSciatic nerve dysfunctionSecondary systemic amyloidosisSensorimotor polyneuropathyTibial nerve dysfunctionUlnar nerve dysfunctionAny 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.
What is salutatory conduction?
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.
What is slowest conduction velocity?
Referring to cardiac pathways it is found in the AV node.
Which process conduction convection or radiation is used to remove heat from car raditor?
Its actually conduction - to the air passing through (due to the fan ... or the forward velocity of the car).
When does saltatory conduction occur?
Saltatory Conduction is a means by which action potentials are transmitted along myelinated nerve fibers. The cytoplasm of an axon is electrically conduction and because myelin inhibits charge leakage through the membrane, depolarization at one node of Ranvier is sufficient to elevate the voltage at a neighboring node to the threshold for action potential initiation. Therefore in myelinated axons, instead of axon propagating as waves but they occur at successive nodes and 'hop' along the axon. This means of travel is much faster than they would otherwise (120 m/sec compared to 35m/sec in unmyelinated nerve fibers). Another advantage of this is that energy is saved as sodium potassium pumps are only required at specific points along the axon. Sean Sinclair
Who invented the nerve conduction velocity test?
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What is the nerve conduction velocity test?
It measures the ability of the nerve to conduct electrical signals
What is a Nerve conduction velocity test?
A test that measures the time it takes a nerve impulse to travel a specific distance over the nerve after electronic stimulation.
What do nerve conduction velocity studies?
Nerve conduction velocity studies (NCV) are used to measure the speed with which an electrical signal is transferred along the nerve.
Does the nerve conduction velocity test produce shocks?
This test may cause mild tingling and discomfort similar to a mild shock from static electricity
What is the relationship between nerve size and conduction velocity?
velocity proportional to square root of diameter
What is the relationship between size of nerve and conduction velocity?
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.
Is the velocity of a nerve impulse greater than electrical conduction's?
yes
The velocity of nerve impulse conduction is greatest in?
Heavily myelinated, large diameter fibers
What is the cost of neurological testing?
Nerve Conduction Velocity scans costs Rs1500/-What_is_the_cost_of_a_Nerve_Conduction_Test
What is electrotonic conduction of a nerve?
is a test commonly used to evaluate function
If the position of a nerve was reversed and its conduction velocity recorded would it be the same as if it were not reversed?
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.
