Electromyography (EMG) is an important means of neurophysiological evaluation in facial palsy patients. Its diagnostic role is widely recognized, as it allows one to confirm a facial nerve injury and to assess its severity (Rubin DI, 2019; Lee DH, 2016) (see Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7)

This ability is due to the peculiar neuromuscular behaviour of facial muscles affected by facial palsy. Facial paresis patients maintain some degree of facial muscular contraction; early facial paralysis patients present with spontaneous action potentials (fibrillations), and chronic facial palsy patients are unresponsive to electrical stimulation due to the fibro-adipose substitution of muscular tissues. Furthermore, preoperative EMG also allows possible donor nerves (masseteric, hypoglossus, temporalis, spinal, contralateral branches of the facial nerve) functionality assessment, to determine a neurological mapping (Biglioli, 2015a; Guntinas-Lichius O, et al., 2020).

Although EMG studies allow for differentiating acute and chronic facial palsy according to fibrillation status, most studies and practices classify acute and chronic palsies on the basis of an 18- to 24-month cut-off and select treatment accordingly. That is not precise, and timing may shorten according to personal characteristics, previous palsy episodes, and duration of palsy onset (Heaton and Kobler, 2005; Jiang JL et al., 2000; Midrio M, 2006; Pond A et al., 2014).

Given the possibilities offered by EMG, as well as its relatively low cost and invasiveness, using time from paralysis onset as the only parameter for choosing how to restore facial movements is somehow limited. The presence of mimic muscle fibrillations suggests that mimic muscles are viable and able to restore movements in the presence of an adequate new motor stimulus (e.g. the association of masseteric and hypoglossal nerve and some distal branches of the contralateral facial nerve through one or two cross-face sural nerve grafts) (Biglioli F, et al., 2018). On the other hand, the absence of mimic muscle fibrillations implies the need for muscular transplantation to restore facial movements (Biglioli, 2015a; 2015b); this latter option provides solid results, although it is inferior to recent facial palsy techniques.

In this paper, the authors aim to demonstrate that EMG fibrillations add important criteria to the temporal one for selecting acute facial palsy patients for reanimation purposes. With this purpose, we conducted a prospective cohort study comparing triple innervation facial reanimation results in patients with EMG fibrillation treated <12 months, 12–18 months, and >18 months from paralysis onset.