The principle of selective reinnervation is to use the ipsilateral proximal facial nerve to power eye closure and the ipsilateral masseteric nerve to power the smile.
Smiling and biting are synchronous actions. Patients can learn to perform both activities naturally at the same time. This is a distinct advantage over other nerve input options, such as hypoglossal or spinal accessory.
With ongoing practice and physiotherapy, some patients can learn to smile spontaneously. This may occur due to cortical adaptation.
General considerations regarding nerve repair techniques can be found here.
2. Proximal facial nerve to power eye closure
This technique is most commonly performed immediately following tumor ablation of the parotid gland, but it can be used whenever the proximal trunk of the facial nerve is available in order to limit synkinesis.