Neurology & Pain Management Coding Alert

Question: What's the difference between M-waves and F-waves? How are they coded?

California Subscriber
Answer: The M-wave is the compound motor action potential (CMAP) that is recorded when a motor nerve is stimulated and the response is obtained from the appropriate muscle. It is obtained as an integral part of a motor nerve conduction study (95900, Nerve conduction, amplitude and latency/velocity study, each nerve; motor, without F-wave study). A single unit of 95900 is reported for each separate motor nerve tested.
 
The F-wave is a late response that occurs after an M-wave response. It is used to assess the proximal segments of the motor nerve function and is used in the evaluation of plexopathy, radiculopathy, polyradiculoneuropathy, and other proximal or multifocal disorders. An F-wave motor nerve conduction study is reported using 95903 ( motor, with F-wave study). A single unit is billable for each separate motor nerve tested.
 
You are "unbundling" if you bill 95900 and 95903 when the F-wave and motor conduction studies are performed on the same nerve. Only 95903 should be reported. If F-wave and motor conduction studies are performed on different nerves, 95900 and 95903 may be billed together. To clarify this, the American Academy of Neurology suggests submitting documentation specifying the number of nerves tested. CMS recommends appending modifier -59 (Distinct procedural services) to the second and subsequent codes to indicate a different anatomical area. Also, all nerve conduction studies (95900-95904) are modifier -51 (Multiple procedures) exempt.