To Estimate Prognosis
By sampling nerves and muscles in different areas, and comparing to known values, we can estimate the potential for recovery.
In general, the presence of slowed nerve conduction or conduction block is viewed as a positive prognostic factor, as this implies a mostly demyelinating lesion capable of myelin sheath repair. On needle EMG, the presence of motor unit recruitment is similarly a positive sign, as this implies axonal continuity to the target muscle, capable of further reinnervation.
For specific nerves, there is data surrounding the size of compound muscle action potentials with the ability to recover full strength. Similarly, nerve conduction velocities and distal onset latencies can be used to estimate prognosis.