Of the peripheral nerve branches, the MMB is the most vulnerable to injury. Many studies have reported that the MMB is most commonly involved in CPSP (Emodi et al., 2010; Al-Aroomi et al., 2021). Injury to this nerve can cause considerable cosmetic and functional deformities (difficulty in eating, drinking, and speaking) (Stodulski et al., 2015). Moreover, paresis of the MMB requires a longer time to recover compared with the other branches (Nakamura et al., 2017). Therefore, minimizing damage to the MMB is one of the primary objectives of parotidectomy. In in most cases of CPSP, a very long section of MMB must be dissected in a retrograde direction regardless of location and size of the tumor. This is clearly the main reason why the MMB is most commonly involved in CPSP, and why CPSP carries a higher rate of postoperative facial palsy. But the most effective method for minimizing damage to the MMB during PSP has not, to our knowledge, been described.

In the MPSP described in this study, the MMB is dissected in an anterograde direction or not dissected, with the extent of the MMB dissection governed by the location and size of the tumor. The study was undertaken to determine whether the MPSP can reduce the risk of injury to the MMB of the facial nerve, and the rate of postoperative facial palsy compared with CPSP.