European Journal of Cardiovascular Medicine

Facial nerve paralysis has emotional, psychological, and clinical effects on the subjects along with its association with cosmetic deformity. Common causes of paralysis are tumors, traumatic facial palsy, and Bell's palsy with common causes of traumatic facial paralysis being iatrogenic injuries, penetrating injuries, and TBF (temporal bone fracture) where injury can be from edema and bony fragment compression, loss of nerve continuity, or intraneural hematoma. The transverse segment and perigeniculate ganglion are the most common injury sites in TBF. Recovery of facial nerve function is determined by the mode, nature, and progression of facial nerve palsy. Traumatic facial nerve palsy can be immediate or delayed onset where immediate onset needs surgical intervention and delayed onset recovers spontaneously without surgery.¹

Facial nerve palsy severity is clinically assessed with HBG I-VI (House Brackmann grading) and the degree of injury is assessed with electrophysiological tests including nerve excitability test, maximum stimulation test, EMG (electromyography), and ENoG (electroneuronography). ENoG is useful for assessing nerve degeneration in 1^st 2-weeks after trauma and reveals>90% degeneration within 14 days as the threshold for assessing nerve decompression. EMG is used to assess nerve regeneration for >2 weeks of injury. The site of injury is assessed with Topodiagnostic tests including the stapedial reflex test and Schirmer's test.²

Subjects with complete, persistent, and immediate onset facial palsy (HBG-VI) particularly with poor electrodiagnostic testing with EMG and ENoG have lesser recovery chances if managed medically. However, till now, there is no consensus concerning the ideal surgical approach and ideal time for the surgery. There are controversies concerning the best surgical approach for the injured facial nerve injured segment. The site of facial nerve injury is the basis for selecting the preferred approach for the surgery. Different FND approaches are transcanal, transmastoid, and middle cranial fossa approaches. In the middle cranial fossa approach, FN exposure is possible in the proximal geniculate ganglion and labyrinth area without disturbing the hearing. However, it included temporal lobe resection and craniotomy. On the contrary, the transmastoid approach is indicated with a localized facial nerve injury to the distal tympanic segment, 3rd genu, and mastoid segment of the facial nerve.³

Traditionally, canal wall-up mastoidectomy with extended facial recess and atticotomy is a standard technique for transmastoid. This is an adequate procedure that needs the drilling of bone for good exposure. Microscopic or endoscopic transcanal approach allows direct access from the geniculate ganglion to 2^nd genu. Major benefits of the transcanal approach are enhanced surgical field view and the capacity to see around the corner.⁴ The present study aimed to assess the outcomes following TEA (transcanal endoscopic approach) for facial nerve decompression using the transcanal approach concerning the improvement in the facial nerve (FN) function and hearing level in lesions from tympanic segment and peri geniculate segment of the facial nerve.

The present retrospective study was aimed to assess the outcomes following TEA (transcanal endoscopic approach) for facial nerve decompression using the transcanal approach concerning the improvement in the facial nerve (FN) function and hearing level in lesions from tympanic segment and peri geniculate segment of the facial nerve. The study subjects were from the Department of ENT of the Institute. Verbal and written informed consent were taken from all the subjects before participation.

The study assessed 18 subjects from both genders that were post-traumatic cases of facial paralysis within the defined study period. For all the subjects, clinical data of the subjects presenting with traumatic nerve palsy involving the tympanic segment and peri-geniculate ganglion were assessed and reviewed. Facial nerve decompression via TEA was done in all the subjects. All included subjects had traumatic facial nerve palsy of immediate onset with HBG IV, V, and VI.

The study subjects having traumatic nerve palsy involving the tympanic segment and peri-geniculate ganglion were assessed endoscopically with TEA and were followed for 12 months postoperatively. The exclusion criteria for the study were subjects with facial nerve palsy involving the mastoid segment and subjects having traumatic nerve palsy and responding to systemic steroids. In all the subjects, demographic data were noted. In all the subjects, clinical history was noted concerning previous neurosurgical intervention, presence of any comorbidities, rapidity of onset of facial asymmetry, and mode of injury. The time gap between presentation to the otologist and the onset of facial asymmetry after trauma was assessed and recorded.

Clinical examination also involved neurological examination, tuning fork tests, and ontological findings along with preoperative and postoperative facial nerve functions graded with the HBG system. Pure tone audiometry was done in all the subjects preoperatively and postoperatively where the postoperative hearing assessment was done by air-bone gap (ABG) in 0.5, 1, 2, and 4 KHz frequency. After surgery, facial muscle physiotherapy was done in all subjects along with Schirmer's test (top diagnostic test). Also, temporal bone HRCT was done to assess the ossicular chain status and injury site.

In surgical technique, all the subjects were managed under general anesthesia using an endoscope. A transcanal incision was given followed by raising the posterior tympanomeatal flap. For good exposure of the middle ear, the entire malleus was skeletonized from the tympanic membrane. The posterior bony canal wall was removed by posterior canaloplasty to get ease and good exposure for instrumentation. The incudistapedial joint was then disarticulated and removed from the head of the malleus and incus. Atticotomy was then done to expose the supra-labyrinthine and epitympanic region. Cog and Cochleariform processes were taken as vital landmarks to identify the geniculate ganglion.

Both cog and cochleariform processes were removed to increase exposure to the perigeniculate ganglion area. The site of the facial nerve injury was then carefully assessed. Fractured bony spicules that were impinging the facial nerve from granulation and supra labyrinthine cells were removed carefully with curette, pick, and diamond bur to expose the geniculate ganglion for proper exposure if a tympanic segment of the facial nerve, greater superficial petrosal nerve, and geniculate ganglion. Facial nerve decompression was done by an incision in the epineurium with a tenotome. Partial ossicular reconstruction was done with a titanium prosthesis or autologous incus. A small cartilaginous graft, earlier harvested from the tragus along with tragal cartilage was utilized for repairing the attic defect and to support the tympanomeatal flap followed by tympanomeatal flap repositioning. The external auditory canal was then filled with gel foam and normal saline.  

The data gathered were analyzed statistically using SPSS (Statistical Package for the Social Sciences) software version 24.0 (IBM Corp., Armonk. NY, USA) for assessment of descriptive measures, one-way ANOVA (analysis of variance), and chi-square test. The results were expressed as mean and standard deviation and frequency and percentages. The p-value of <0.05 was considered statistically significant.

The present retrospective study was aimed to assess the outcomes following TEA (transcanal endoscopic approach) for facial nerve decompression using the transcanal approach concerning the improvement in the facial nerve (FN) function and hearing level in lesions from tympanic segment and peri geniculate segment of the facial nerve. The present study retrospectively assessed subjects with post-traumatic facial nerve paralysis that were managed surgically using a transcanal endoscopic approach. During the study period, 18 subjects were taken. The mean age of the study subjects was 38.8±6.7 years with an age range of 20-50 years. There were 88.8% (n=16) male and 11.1% (n=2) female subjects in the study. The facial nerve injury site was geniculate ganglion in 55.5% (n=10) study subjects, was a tympanic segment in 22.2% (n=4) study subjects, and was both in 22.2% (n=4) study subjects respectively. Timing of surgery from the trauma was 25-35 days in 55.5% (n=10) study subjects, 35-55 days in 22.2% (n=4) study subjects, 55-75 years in 11.1% (n=2) study subjects, and >75 days in 11.1% (n=2) study subjects respectively (Table 1).

Table 1: Demographic and disease data in study participants

Table 2: Intra-operative findings in the study subjects

Table 3: HBG scores in study subjects preoperatively and postoperatively

Table 4: ABG scores in study subjects preoperatively and postoperatively

On assessing the intraoperative findings in the study subjects, it was seen that bony fragments were seen in 55.5% (n=10) study subjects where fibrosis, edema, and granulation were seen in 22.2% (n=4), 11.1% (n=2), and 11.1% (n=2) study subjects respectively. Edema was seen in 11.1% (n=2) study subjects, edema granulation was seen in 11.1% (n=2) study subjects, hematoma edema was seen in 11.1% (n=2) study subjects, and granulation in 22.2% (n=4) study subjects respectively (Table 2).

It was seen that for HBG scores in study subjects preoperatively and postoperatively, HBG scores preoperatively were IV in 8 subjects and V in n=10 study subjects. At 1 week postoperatively, HBG scores were III and IV in 12 and 6 study subjects respectively. At 6 months postoperatively, HBG scores of I, II, and III were seen in 4, 10, and 4 study subjects respectively. At 1-year postoperative follow-up, HBG scores were I, II, and III in n=8, 6, and 4 study subjects respectively (Table 3).

The study results showed that for preoperative and postoperative ABG (air-bone gap) in the study subjects, preoperative ABG of 0-20, 20-25, 25-30, and 30-35 were seen in 11.1% (n=2), 33.3% (n=6), 11.1% (n=2), and 44.4% (n=8) study subjects respectively. For postoperative ABG, a significant reduction was seen as 0-20 ABG in 77.7% (n=14), 20-25 in 11.1% (n=2), 25-30 in 11.1% (n=2), and 30-35 dB in 0 study subjects (Table 4).

The present study retrospectively assessed subjects with post-traumatic facial nerve paralysis that were managed surgically using a transcanal endoscopic approach. During the study period, 18 subjects were taken. The mean age of the study subjects was 38.8±6.7 years with an age range of 20-50 years. There were 88.8% (n=16) male and 11.1% (n=2) female subjects in the study. The facial nerve injury site was geniculate ganglion in 55.5% (n=10) study subjects, was a tympanic segment in 22.2% (n=4) study subjects, and was both in 22.2% (n=4) study subjects respectively. Timing of surgery from the trauma was 25-35 days in 55.5% (n=10) study subjects, 35-55 days in 22.2% (n=4) study subjects, 55-75 years in 11.1% (n=2) study subjects, and >75 days in 11.1% (n=2) study subjects respectively. These data were similar to the studies of Lee PH et al⁵ in 2018 and Anschuetz L et al⁶ in 217 where authors assessed subjects with demographic and disease data comparable to the present study.

The study results showed that on assessing the intraoperative findings in the study subjects, it was seen that bony fragments were seen in 55.5% (n=10) study subjects where fibrosis, edema, and granulation were seen in 22.2% (n=4), 11.1% (n=2), and 11.1% (n=2) study subjects respectively. Edema was seen in 11.1% (n=2) study subjects, edema granulation was seen in 11.1% (n=2) study subjects, hematoma edema was seen in 11.1% (n=2) study subjects, and granulation in 22.2% (n=4) study subjects respectively. These results were consistent with the findings of Ferri G. et al⁷ in 2019 and Kahinga AA et al⁸ in 2018 where intraoperative findings similar to the present study in subjects with traumatic facial nerve palsy were reported by the authors in their respective studies.

Concerning HBG scores in study subjects preoperatively and postoperatively, HBG scores preoperatively were IV in 8 subjects and V in n=10 study subjects. At 1 week postoperatively, HBG scores were III and IV in 12 and 6 study subjects respectively. At 6 months postoperatively, HBG scores of I, II, and III were seen in 4, 10, and 4 study subjects respectively. At 1-year postoperative follow-up, HBG scores were I, II, and III in n=8, 6, and 4 study subjects respectively. These findings agreed with the results of Hato N et al⁹ in 2011 and Hai‑Jin Y et al¹⁰ in 2001 where HBG scores reported by the authors in their study subjects were consistent with the results of the present study.

It was seen that for preoperative and postoperative ABG (air-bone gap) in the study subjects, preoperative ABG of 0-20, 20-25, 25-30, and 30-35 were seen in 11.1% (n=2), 33.3% (n=6), 11.1% (n=2), and 44.4% (n=8) study subjects respectively. For postoperative ABG, a significant reduction was seen as 0-20 ABG in 77.7% (n=14), 20-25 in 11.1% (n=2), 25-30 in 11.1% (n=2), and 30-35 dB in 0 study subjects. These results were in line with the studies of Xie S et al¹¹ in 2016 and Cannon RB et al¹² in 2015 where a significant reduction in ABG values after surgery for facial nerve palsy as seen in the present study was reported by the authors in their respective studies

The present study, considering its limitations, concludes that TEA for facial nerve decompression is a direct approach in lesions confined to the peri-geniculate ganglion and tympanic segment of the facial nerve without involving the mastoid segment of the facial nerve. It needs accurate surgical site assessment, proper visualization, and minimal bone drilling are its advantages.

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