Cranial Nerve Coactivation and Implication for Nerve Transfers to the Facial Nerve

Abstract

In reanimation surgery, effortless smile can be achieved by a nonfacial donor nerve. The underlying mechanisms for this smile development, and which is the best nonfacial neurotizer, need further clarification. The aim of the present study was therefore to further explore the natural coactivation between facial mimic muscles and muscles innervated by the most common donor nerves used in smile reanimation. The study was conducted in 10 healthy adults. Correlation between voluntary facial muscle movements and simultaneous electromyographic activity in muscles innervated by the masseter, hypoglossal, and spinal accessory nerves was assessed. The association between voluntary movements in the latter muscles and simultaneous electromyographic activity in facial muscles was also studied. Smile coactivated the masseter and tongue muscles equally. During the seven mimic movements, the masseter muscle had fewer electromyographically measured coactivations compared with the tongue (two of seven versus five of seven). The trapezius muscle demonstrated no coactivation during mimic movements. Movements of the masseter, tongue, and trapezius muscles induced electromyographically recorded coactivation in the facial muscles. Bite resulted in the strongest coactivation of the zygomaticus major muscle. The authors demonstrated coactivation between voluntary smile and the masseter and tongue muscles. During voluntary bite, strong coactivation of the zygomaticus major muscle was noted. The narrower coactivation pattern in the masseter muscle may be advantageous for central relearning and the development of a spontaneous smile. The strong coactivation between the masseter muscle and the zygomaticus major indicates that the masseter nerve may be preferred in smile reanimation.

Masseteric nerve vs. hypoglossal nerve: choice of donor nerve in the reanimation of short-term facial palsy

“…Apoyando este hallazgo, se ha visto que en pacientes operados de parálisis facial empleando una mioplastia de elongación de músculo temporal, el cual está inervado por otra rama motora del nervio mandibular (V 3 ), dichas áreas del córtex correspondientes a la sonrisa y al apretado de dientes se tornan en una tras la cirugía (42). Por otro lado, existe una importante coactivación del músculo masetérico y del cigomático mayor, sugiriendo esto también que el masetérico podría ser preferible a otros nervios no faciales como el hipogloso (43), cuyo núcleo se encuentra, además, más alejado del facial que el del V par, como ya se ha mencionado previamente. La proximidad de los centros corticales es un importante factor a través del cual se ha hipotetizado que podría haber una adaptación cerebral mediante la reorganización de conexiones nerviosas horizontales latentes del VII al V par craneal.…”

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“…La expresión "democratizar la protonterapia" tiene su origen (comunicada en 2022) en la iniciativa del Instituto Nacional del Cáncer Norteamericano denominada Cancer Moonshot. (43). Otras iniciativas promueven sinergias entre Agencias de Salud y organismos internacionales transcontinentales (América, Europa y África).…”

Paediatric facial paralysis: An overview and insights into management

“…Complete recovery of function is unlikely; however, this should allow the restoration of tone and activity to restore baseline function. 7 If restoring facial nerve continuity is not possible, then a nerve transfer is an option utilising either a cross-facial nerve graft (CFNG) from the contralateral facial nerve, [21][22][23] the hypoglossal nerve (hemi-tongue function) or the masseteric nerve (muscle of mastication) both of which show synergistic contraction during smiling. [22][23][24] These reconstructions however mean that another muscle is weakened to create facial muscle movement.…”