5 Interesting Facts of Nerve Conduction Studies
1. Nerve conduction studies (NCS) and needle electromyography (EMG) are the most useful diagnostic tests in determining the presence, type, severity, and chronicity of a suspected neuromuscular disorder.
2. Although the information collected during NCS and needle EMG testing is more objective and quantitative than that obtained by a standard clinical examination, there are many important technical factors that contribute to the collection of accurate data. Selection of a reputable or accredited laboratory and experienced electrodiagnostic consultant will help ensure the most accurate data and reliable interpretation.
3. Sensory NCS are the most useful way to distinguish preganglionic (radiculopathy) from postganglionic (peripheral neuropathy or plexopathy) processes that cause numbness.
4. NCS can help distinguish between demyelinating and axonal neuropathies. Demyelinating neuropathies have moderate to severe slowing of the nerve conduction velocities with relatively preserved compound muscle action potential (CMAP)/sensory nerve action potential (SNAP) amplitudes. On the other hand, axonal neuropathies have reduced CMAP/SNAP amplitudes with relatively preserved conduction velocities.
5. On EMG, the motor unit action potentials (MUAPs) in neurogenic disorders have characteristic large amplitudes with long durations and reduced recruitment. The MUAPs in myopathic disorders have small amplitudes with short durations and early recruitment.