Introduction: While there is great interest in selective neurectomy (SN) for patients with synkinesis, outcomes can be inconsistent. Objective: To examine the relationships between intraoperative facial nerve branch transection and both postoperative outcome and functional deficits. Methods: SN cases, with minimal follow-up of 4 months, were retrospectively identified between 2019 and 2021; outcome was assessed using FaCE instrument, eFACE and Emotrics. Correlations between intraoperative facial nerve branch preservation or transection, and functional outcome and new functional deficits were examined. Results: Fifty-six cases were performed: 88% were females, and median age was 53 years (range 11-81). Mean follow-up was 19.5 months (range 4-42). Oral commissure excursion improved in patients where all smile branches were preserved, no vertical vector smile branches were transected, and more than three smile antagonist branches were transected. A linear trend between smile antagonist branch sacrifice and favorable smile outcome was found. Lower lip movement was improved in patients in whom more than half of the identified lower lip branches were transected. Thirty percent of patients experienced untoward postoperative functional deficits, from which 47% recovered with interventions. Conclusions: Several correlations between SN intra-operative decisions and outcome were identified; new or worsening functional deficit rate can be high. However, chemodenervation or fillers can help diminish these deficits.