Avaliação eletromiográfica do músculo masseter em pessoas com paralisia facial periférica de longa duração Masseter muscle electromyographic assessment in subject with long lasting facial palsy

OBJETIVO: verificar a atividade elétrica do músculo masseter em pessoas com paralisia facial periférica de longa duração. MÉTODOS: participaram deste estudo seis sujeitos de ambos os sexos, com paralisia facial há pelo menos doze meses, sem queixas mastigatórias e sem disfunção temporomandibular e com pelo menos seis dentes em cada hemiarcada. Todos preencheram um questionário de anamnese e em seguida foram submetidos à eletromiografia de superfície dos masseteres de ambos os lados. As provas eletromiográficas foram: posição habitual com lábios fechados, apertamento dentário, mastigação habitual e unilateral à direita e à esquerda com uva passa. RESULTADOS: em todas as provas eletromiográficas não foram observadas diferenças significantes (p=0,05) entre os lados com e sem paralisia facial. CONCLUSÃO: observou-se com o presente estudo que a força do músculo masseter não sofre influência da paralisia facial de longa duração.<br>PURPOSE: to check the masseter electrical activity in long lasting facial paralysis patients. METHODS: six subjects, with facial paralysis for over a period of twelve months, males and females, took part in this study. Patients should not show any masticatory complaints or have any diagnoses of temporo-mandibular joint dysfunction, having at least six teeth in each half dental ridge. All subjects filled out a questionnaire regarding oral habits and were assessed by surface electromyography of the masseter muscle of both sides. Electromyographic records were taken with lips closed at rest, teeth tightness, besides usual mastication, and unilateral mastication on both sides with raisins. RESULTS: in all electromyographic tests there were no statistically significant differences (p=0.05) between both sides, with and without facial paralysis. CONCLUSION: it was observed that the strength of the masseter muscle is not under the influence of long lasting facial paralysis

Experimental Studies on Facial Nerve Regeneration

Insufficient recovery after injury of a peripheral motor nerve is due to (1) inappropriate pathfinding as a result of axonal regrowth to inappropriate targets, (2) excessive collateral axonal branching at the lesion site, and (3) polyinnervation of the neuromuscular junctions (NMJs). The rat facial nerve model is often used because of its simple and reliable readout to measure recovery of function (vibrissal whisking). Over the last decades scientists have concentrated their efforts to combat mostly NMJ polyinnervation, because it turned out to be very difficult to reduce collateral axonal branching and impossible to navigate thousands of axons toward the original fascicles. In the past, several groups of scientists concentrated their efforts to reduce the activity-dependent polyinnervation of NMJs by electrical stimulation of the muscles (square 0.1 msec pulses at 5 Hz). The results showed no recovery of functions and a severe reduction in the number of innervated NMJs to approximately one fifth of those observed in intact animals. More recent experiments, however, have shown that motor recovery improved significantly following mechanical stimulation of the denervated facial muscles (vibrissal and orbicularis oculi) and that restored functions could invariably be linked to reduced polyinnervation at the NMJ while the number of innervated NMJ remained the same. These results suggest that clinically feasible and effective therapies could be developed and tested in the near future. Anat Rec, 302:1287-1303, 2019. (c) 2019 Wiley Periodicals, Inc