Figure 1 Compound muscle action potentials in the orbicularis oculi (O. oculi; upper traces) muscle and abnormal muscle responses (AMR) in the orbicuralis oris (O. oris; lower traces) muscle recorded after supramaximum stimulation at the zygomatic branch of the facial nerve (A), its subthreshold stimulation (B), and paranasal skin stimulation (C). Four successive recordings were superimposed. AMR usually consisted of two components (A2); the early constant component (AMR1) and late variable component (AMR2), but some patients only had either AMR1 (A1) or AMR2 (A3). Note that after motor subthreshold or skin stimulation, there was no compound muscle action potential in the O. oculi and O. oris by direct stimulation.