Predictive role of gnathological techniques for the treatment of persistent idiopathic facial pain (PIFP).

INTRODUCTION/BACKGROUND: Persistent idiopathic craniofacial pain (PIFP) is a heterogeneous group of pain syndromes whose main characteristic is the daily presence of persistent pain for at least 3 months. The pathophysiology of PIFP is still not entirely known and probably related to biological and psychological factors. Although PIFP has been attributed to the central neuron activity, the importance of masticatory muscles as a possible pathogenic mechanism was recently demonstrated. The main purpose of our paper was to identify the physiological rest position of the mandible with minimal tonus of both the elevator and depressor muscles and the neuromuscular trajectory of mouth closing obtained by transcutaneous electrical stimulation (TENS) and maintained with the use of an occlusal device, known as orthotic. MATERIALS AND METHODS: The VAS scale for facial pain and the migraine disability assessment score (MIDAS) index for patient quality of life were evaluated at the beginning of the study for the 38 subjects that came to our attention. Our research included two phases. The first phase consisted of kinesiographic and electromyographic (EMG) examinations of the masticatory muscles and a 45-min application of TENS in order to deprogram the muscular activity. Kinesio-electromyographic examinations were repeated in the second phase. The main evaluated parameter was jaw deflection or deviation on the sagittal and frontal planes before and after TENS during patient tooth occlusion. Patients that showed a significant modification of this parameter were treated with orthotics for 12 months. RESULTS: The results of a 12-month follow-up show a sharp reduction of the VAS (pre-orthotic 9.05, range 8-10, SD 0.8; post-orthotic 5.87, range 1-5, SD 0.7) and an improvement in the quality of life (MIDAS). CONCLUSIONS: Our study demonstrated the usefulness of TENS as a screening method for the application of orthotics. This non-invasive and/or non-painful procedure could be a useful complementary treatment in this patient population. The results of the study also confirm the role of masticatory muscle dynamics as a possible pathogenic mechanism in patients with PIFP.

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

INTRODUCTION: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.