A<unk>  <unk>  is a test commonly used to evaluate the function, especially the ability of electrical<unk> , of the motor and sensory<unk> s of the human body.<unk><unk>  velocity (NCV) is a common measurement made during this test. The term NCV often is used to mean the actual test, but this is improper use of the term since velocity is only one measurement out of the entire test.<unk> es are used mainly for evaluation of paresthesias (numbness, tingling, burning) and/or weakness of the arms and legs. The type of<unk>  is determined by the problem. Some of the common disorders which can be diagnosed by<unk> es.
Peripheral neuropathy
Carpal tunnel syndrome
Ulnar neuropathy
Guillain-Barré syndrome
Facioscapulohumeral muscular dystrophy
The<unk>  consists of the following components:
Motor<unk> 
Sensory<unk> 
F-wave<unk> 
H-reflex<unk> 
Motor<unk>  are performed by electrical stimulation of a peripheral<unk>  and recording from a muscle supplied by this<unk> . The time it takes for the electrical impulse to travel from the stimulation to the recording site is measured. This value is called the latency and is measured in milliseconds (ms). The size of the response - called the amplitude - is also measured. Motor amplitudes are measured in millivolts (mV). By stimulating in two or more different locations along the same<unk> , the NCV across different segments can be determined. Calculations are performed using the distance between the different stimulating electrodes and the difference in latencies.
Sensory<unk>  are performed by electrical stimulation of a peripheral<unk>  and recording from a purely-sensory portion of the<unk> , such as on a finger. Like the motor<unk> es, sensory latencies are also measured in ms. Sensory amplitudes are measures in microvolts (ųV). The sensory NCV is calculated based upon the latency and the distance between the stimlating and recording electrode.
F-wave<unk>  uses stimulation of a motor<unk>  and recording of action potentials from a muscle supplied by the<unk> . This is not a reflex, per se, in that the<unk>  potential travels from the site of the stimulating electrode in the limb to the spinal cord and back to the limb in the same<unk>  that was stimulated. The F-wave<unk>  evaluates<unk>  velocity of<unk> s between the limb and spine, whereas the motor and sensory<unk> es evaluate<unk>  in the limb itself.
H-reflex<unk>  uses stimulation of a<unk>  and recording the reflex electrical discharge from a muscle in the limb. This also evaluates<unk>  between the limb and the spinal cord, but in this case, the afferent impulses (those going towards the spinal cord) are in sensory<unk> s while the efferent impulses (those coming from the spinal cord) are in motor<unk> s.
In 1998 a small-pain-fibers (spf-NCS) method was cleared by the FDA. This method uses an electrical stimulus with a neuroselective frequency to determine the minimum voltage causing<unk> . Rather than comparing the data with population averages on a bell-shaped curve, which at best has about 65% sensitivity, the patient is his own control. In a three year LSU Pain Center<unk>  it was found that the<unk>  requiring the greatest voltage to cause<unk>  of the A-delta (Fast Pain) fibers identified<unk>  root pathology with 95% sensitivity. Besides being painless, the test is fast. A new version, uses a potentiometer to objectively measure the amplitude of the action potential at a distant site along the<unk>  being tested. The previous version relied on the patient reporting a sensation when the<unk>  fired. The spf-NCS does not require myelin loss to detect function change, so velocity is not measured.
Nerve conduction study
Electromyography
Amyotrophic lateral sclerosis CT scan
Peripheral neuropathy CT
Electrophysiology
Transverse myelitis CT
Genetic testing
Erythrocyte sedimentation rate