Repetitive nerve stimulation of the nasalis muscle: Technique and normal values

Abstract

A technique of repetitive nerve stimulation of the facial nerve with recording from the nasalis and orbicularis oculi muscles was developed and tested in 15 healthy subjects. Quality criteria were that the stimulus artifact should return to baseline before the onset of the compound muscle action potential (CMAP), and that the CMAP should begin with a negative phase, be biphasic in shape, and have an amplitude of over 1 mV. Repetitive nerve stimulation was only performed if all four criteria were met, which was the case in all 15 subjects for the nasalis muscle, but in only 5 subjects for the orbicularis oculi muscle. The largest observed decrement was 9% in area. Reptitive nerve stimulation of the nasalis muscle is thus feasible, but its diagnostic utility remains to be established in patients with disorders of neuromuscular transmission.

Sensitivity of repetitive facial‐nerve stimulation in patients with myasthenia gravis

“…The choice of frontalis was based on the historical routine use of this muscle in our laboratory. The choice of nasalis was based on the routine use of this muscle by another laboratory in Toronto, and also on the recent report of the technical superiority of RNS when recording over the nasalis muscle compared to the orbicularis in normal subjects 8…”

“…In addition, RNS sensitivities vary depending on the distribution of weakness (i.e., ocular vs. generalized MG) and severity of disease 3, 5, 7. One study in normal subjects demonstrated the technical superiority of repetitive stimulation of the facial nerve with recording over the nasalis muscle compared with recording over the orbicularis oculi muscle 8…”

“…3,5,7 One study in normal subjects demonstrated the technical superiority of repetitive stimulation of the facial nerve with recording over the nasalis muscle compared with recording over the orbicularis oculi muscle. 8 The main objective of this study was to determine the diagnostic yield of RNS of the facial nerve when responses were recorded over two different facial muscles in patients with ocular and generalized MG compared to the "gold standard," single-fiber electromyography (SFEMG).…”

Comparison Study of Branch Versus Main Trunk Repetitive Nerve Stimulation of Facial Nerve in Normal Subjects

“…Then, six repetitive electrical stimuli were administered at a frequency of 3 Hz (Han et al, 1998;Ruys-Van Oeyen and Van Dijk, 2002) to obtain six identical waveforms (Fig. The study was reviewed and approved by the institutional review board.…”

“…Volunteers were recruited by posting fliers in the EMG laboratory and in the departmental bulletin boards. The amplitudes of individual waveforms and those of the waveforms between the two sites of stimulation were compared (Han et al, 1998;Ruys-Van Oeyen and Van Dijk, 2002). Waveforms were recorded from the frontalis muscle using surface electrodes.…”