Nerve Conduction Velocity (NCV)
MDI Performs NCV Tests In Your Offices
In-office Nerve Conduction Velocity Tests (NCV) measure how quickly electrical impulses move along a nerve. It is often performed at the same time as an electromyogram in order to exclude or detect muscle disorders and it is called a nerve conduction study. A healthy nerve conducts signals with greater speed and strength than a damaged nerve. The speed of the nerve conduction is influenced by the myelin sheath (the insulating coating that surrounds the nerve).
The in-office nerve conduction velocity tests are used to diagnose nerve damage or dysfunction and confirm a particular diagnosis.
In-office nerve conduction velocity tests can usually differentiate injury to the nerve fiber (axon) from injury to the myelin sheath, yielding data paramount in diagnostic and therapeutic strategies. If a response is much slower than normal, damage to the myelin sheath is implied. If the nerve’s response shows decreased amplitude but with relatively normal speed of conduction, damage to the nerve axon is implied.
Information about the impulse after nerve stimulation can be recorded, including latency (time to get from stimulus to recording), the distance traveled and the nerve conduction velocity (NCV). These measures are sensitive indicators of nerve damage and look specifically at the integrity of the myelination of the nerve. The amplitude of the muscle contraction can be determined providing information about the number of neurons that are functioning within the nerve.
Why Order In-Office Nerve Conduction Velocity Tests?
- Isolation of a Specific Site of Injury or Neuropathy to Specific Locations as in carpal tunnel or tarsal tunnel studies. The conduction above and below the tunnel may be normal, while abnormal across the tunnel itself.
- Entrapment and Injuries Identified as in brachial plexopathies, ulna and median entrapments, radial injuries at the spiral groove in the humerus, lumbosacral plexopathies, entrapment of sciatic nerve at the piriformis, the common peroneal nerve at the fibular head, the plantar nerve at the tarsal tunnel, the intermediate dorsal cutaneous nerve branches under the annular ligaments and the anterior tarsal tunnel of the foot.
- Peripheral Neuropathies Identified as in disorders that affect the sensory, motor and autonomic nerves due to various etiologies such as diabetes, alcoholism, autoimmune neuropathies, toxin exposure, metabolic abnormalities, vitamin deficiency or adverse effects of drugs.
- Hereditary Motor-Sensory Neuropathy (HMSN) identified as in Charcot-Marie-Tooth (CMT) presenting as a chronically demyelinating motor-sensory neuropathy causing progressive distal muscle atrophy and weakness, often with gait disturbance and deformity of the feet and hands.
- Differential Diagnosis as in medial cord injury, the ulnar and median nerves are involved along the entire length with sparing of C5-C6 muscles and the paraspinal muscles. A C-7-C8 root injury also affects the median innervated and ulnar-innervated muscles, but the paraspinals are involved. S1 involvement in the lower extremity may be a reason for abnormal nerve conduction studies.
- Acute Injury First Study nerve conduction abnormalities are present immediately even though it takes one to three weeks to become recordable in the muscles. Therefore, it is helpful in the immediate determination of the extent of the injury. In fact, in severe nerve lesions where there is Wallerian degeneration and deficit along the entire length of the nerve, the site of injury no longer can be localized, so you no longer can objectify the gravity of the immediate injury.
- Acute Injury Second Studies are helpful, therefore, in cases of potential liability to determine what changes have occurred and to differentiate preexisting injury from recent trauma assuming you did a first study.
- Altered Skin Sensations.
- Weakness, Twitching, Spasm, Paralysis, Pain, Numbness, Tingling.
- Myositis, Fasiculation, Myopathy.
- Neuromuscular Conditions as Myasthenia Gravis, Amyotrophic Lateral Sclerosis (ALS), etc.
- Trauma, Edema, Cramps, Ataxic Gait, Altered Gait.
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