F.03 Timing of incidence and recovery of delayed facial palsy after vestibular schwannoma resection: insight into mechanisms

Abstract

Background: Delayed facial palsy (DFP) after resection of vestibular schwannomas (VS) is described as worsening of facial nerve function after a normal postoperative result. Several mechanisms have been postulated to explain this phenomenon, although none satisfactorily explain all of its features. Furthermore, systematic documentation of recovery rates is lacking. Methods: 403 consecutive cases of VS resection between 2001 and 2015 were reviewed. Patients with preoperative facial palsy were excluded. Patients developing significant facial palsy (HB grade ≥ 3) were categorized into groups based on timing of onset: immediate facial palsy (IFP), “early-onset” DFP (within 48 h), and “late-onset” DFP (after 48 h). IFP patients were subdivided into “minor” (HB grade 3) and “major” (HB grade≥4) groups. These groups were compared with respect to demographics, intraoperative data, and recovery. Results: The late-onset DFP group demonstrated the quickest recovery to HB≤2 (2.9 weeks), followed by the minor IFP group (8.5 weeks), then the early-onset DFP group (53 weeks). Major IFP group exhibited the poorest recovery with only 32% recovering to HB grade≤2 within one year. Conclusions: The bimodal distribution in recovery time in delayed facial palsy patients implies separate underlying phenomena. We propose that a delayed demyelination of the facial nerve occurs in late-onset DFP, and best explains the uniformly rapid recovery observed.