**1. Introduction**

The face has a unique nervous system. The nervous system of the face is a single synergistic system that combines both hemifaces [1–5]. Clinical observations show that pathological processes in the face are most often unilateral (Bell's palsy, trigeminal neuralgia, hemifacial spasm, etc.) [2–7]. However, in recent years, the question of the influence of the contralateral conditionally healthy hemiface in the pathological

process has been actively studied [1–4, 8]. The lesion of the muscles of facial expression in facial neuropathy is also considered as a bilateral process, which involves the nervous system of both hemifaces. Besides the weakness of the muscles innervated by the facial nerve on the affected hemiface, there is an absolute hypertonicity of the muscles of facial expression of the healthy hemiface [1–4, 9]. Normally, in facial neuropathy the healthy hemiface is used for the comparison. However, a special functional state of the contralateral side, manifested by increased muscle tone, is one of the causes of facial expression asymmetry (static and dynamic) [3, 8–10]. An EMG analysis of the muscle tone of the face in the "healthy" hemiface revealed a statistically significant increase in bioelectrical activity (BEA) in patients with facial nerve neuropathy in comparison to the control group (p < 0.05) [1, 11]. The data obtained allow us to assert that the true over action of muscles of facial expression is formed on the "healthy" side. Activation of the contralateral side is a maladaptive response and requires therapy [1–4, 8–10]. We have used the method to influence muscle hypertonicity of the healthy hemiface in neuropathy of the facial nerve using local injections of botulinum toxin type A. Synkinesis (Greek. *syn* – together and *kinesis* – movement) is the most common complication of the facial neuropathy. Joint movements, in the form of involuntary contractions of the facial muscles that occur when performing basic facial expressions, are observed [12–14]. A patient's quality of life significantly reduces due to the synkinesis. The treatment of synkinesis is very difficult due to the lack of a positive effect of a traditional pharmacotherapy. A local injection of botulinum toxin type A in the area of synkinesis can bring a good but temporary effect [11, 14]. However, the weakness of muscles of facial expression, which develops at the same time, causes a significant frustration in patients and creates discomfort. A joint work of neurologists and plastic surgeons allowed us to propose a method for correcting synkinesis using monofilament mesothreads, which are commonly used in esthetic practice.
