The role of electrophysiological investigations of masticatory muscles in patients with persistent idiopathic facial pain

The authors tried to establish whether there is any electrophysiological difference of masticatory muscle activity between patients with persistent idiopathic facial pain (PIFP) and healthy subjects. Twenty-eight PIFP patients (6 men and 22 women, mean age 40 years) and 28 normal subjects (12 men and 16 women, mean age 40 years) underwent EMG of temporal and masseter muscles before and after transcutaneous electric nerve stimulation (TENS). After TENS stimulation, the mean amplitude difference was found to be smaller than the baseline before TENS in the PIFP patients compared with healthy subjects. The peculiar behavior of masticatory muscles after TENS could be relevant in order to explain the well-known improvement of pain reported by some PIFP patients after orthosis positioning.