Macro NAP Probe It electrically evokes nerve action potentials (NAP) by stimulation and record it to identify lesions of the larger peripheral nerves (e.g. the sciatic nerve or those in the brachial plexus). Micro NAP Probe This probe creates stimulation for precise identification during functional neurosurgery, traumatic and compressive lesions of peripheral nerves. It is also used to carry out root SEP's.