Clinical and electromyographic study of lateral preference in mastication in patients with longstanding peripheral facial paralysis.

Peripheral facial paralysis (PFP) usually affects the facial nerve in part or in whole on one side of the face. Most patients with acute PFP find it difficult to chew on the paralyzed side, especially due to compromised buccinator function. In addition, the sagging of the ipsilateral lip commissure tends to compromise lip competence. The purpose of this study was to evaluate the impact of long-standing PFP upon mastication, relating to clinical mastication sidedness as determined by clinical and electromyographic activity of the masseters. The study included 27 male and female subjects aged 16-69 years with permanent natural dentition and long-standing PFP. Patients answered questions on their mastication habits before and after onset of PFP and were submitted to clinical myofunctional examination and electromyographical tests of the masseters during clenching and habitual mastication. According to the anamnesis, 77.8 % claimed to prefer chewing on the unaffected side. Clinically, 70% presented a lateral preference in mastication. In the clinical evaluation the buccinators and orbicularis oris differed significantly (p = 0.025) between the healthy and the paralyzed side. Only 22.2% of the patients showed increased thickness of the contralateral masseters. No statistically significant electromyographic difference was observed between the masseters on the affected and unaffected side. Conclusions In general indicated that subjects with flaccid-stage PFP for 6 months or longer preferred to masticate on the unaffected side. No significant clinical or electromyographic differences were found in masseter activity between the affected and unaffected side in this patient sample.