Can needle-EMG correctly diagnose combinations of two damaged nerves?

It is accepted that when there is severe, focal nerve damage and an appropriate needle-EMG (nEMG) study is carried out, the electromyographer can infer the correct diagnosis. But is it a fact? This study will check the inference. In this theoretical study, all the possible combinations of two damaged nerve-segments were computed and converted into the expected nEMG findings. These nEMG findings were interpreted and the results compared with the known nerve damage. To facilitate the study, as multiple nEMG findings were analyzed, an automated diagnostic program was used. It was found that in the best of cases, only 64% of concurrent two-nerve damage could be correctly diagnosed by nEMG as one single diagnosis. The rest 36% manifest three types of possible errors: the diagnosis of only one of the two damaged nerve-segments; the diagnosis of a wrong nerve-segment and the diagnosis of one set of damaged nerve-segments, at times the wrong one, when multiple possibilities exist. Utilizing diagnostic programs or tables as ancillary support in the interpretation of nEMG data may function as a second opinion and help electromyographers in ascertaining their own impression.