Outcomes Of Total Transcanal Endoscopic Facial Nerve Decompression

Objective:The tympanic segment of facial nerve is a common site injured by temporal bone fracture,which inducing peripheral facial paralysis.And the traditional facial nerve decompression surgery performed for this kind of patients is through transmastoid approach.In this study,a less invasive exclusive endoscopic transcanal approach that could visualize the entire tympanic segment of facial nerve was performed and the indication,efficacy and features of this approach was discussed in order to provide a clinical reference of the treatment of this kind of facial nerve injury.Method: The clinical and surgery data of eleven patients who suffered peripheral facial nerve paralysis caused by temporal bone fracture in our hospital among Feb 2018 to April 2019 is retrospectively studied.Pre-and postoperative hearing levels and facial nerve function were compared and imaging,topognostic tests,neuroelectrophysiology,surgery videos and postoperative complications were analyzed to illustrate the essentials of total transcanal endoscopic facial nerve decompression for traumatic facial palsy.Results: The results of preoperative high resolution CT(HRCT)of all patients showed that the lines of bone fracture across mastoid and external auditory canal and extended to the tympanic segment of facial nerve without inner ear involved.The injured sites of facial nerve were located at the tympanic segment of facial nerve according to the results of HRCT,Schirmer’s test,acoustic stapedius reflex and taste test preoperatively and were confirmed intraoperatively.All the patients were graded HB-VI before surgery with ENo G≥95%.The recovery of facial nerve function were good(HB-I or II)among 90.9% cases(HB-I in seven cases and HBII in three)a year after surgery with only one case(9.1%)for HB-III.The facial nerve function improved among all cases(p=0.002).With the application of TORP in ten cases and PORP in one case for the reconstructions of ossicular chains,the average air-bone gap(ABG)was reduced from 27.5±10.1d B pre-operatively to 7.8±3.3d B postoperatively(p<0.001).The ABGs were below 10 d B in eight cases(72.7%)and the ABGs of all cases were below 20 d B a year after surgery.Incudostapedial joint dislocations were found in two cases and stapes neck fracture in one case,and the ABGs of them were all over 35 d B with 40.4d B in average.The ABGs in those cases without ossicular chain injurey were significantly lower with 22.4d B in average(p<0.01).Conclusions: Total transcanal endoscopic facial nerve decompression for traumatic facial palsy is feasible to visualize the facial nerve from the origin of labyrinthine segment to the pyramid segment.The effects of this minimally invasive approach were good both in recovery of facial nerve function and hearing level,especially when there is a damaged ossicular chain.Patient with ABG over 35 d B pre-operatively should be suspected that the ossicular chain was injured.