Facial canal dehiscence: histologic study and computer reconstruction

Intratemporal Facial Nerve Anatomy and its Variations in 30 Cases of Cadaveric Temporal Bones

It is important for the ENT surgeon to be familiar with the anatomy of the facial nerve and to prevent iatrogenic injury to nerve as it shows variations in its intratemporal course. Present study was done to delineate the intratemporal course of facial nerve and observe its variations. Thirty wet cadaveric temporal bones were dissected in the temporal bone dissection laboratory in the Department of Otorhinolaryngology and Head Neck Surgery, Government Medical College, Patiala. The length of intratemporal segments of facial nerve, its relationship with important bony landmarks, and the presence of any anomaly or variations in its course were observed. The mean length of labyrinthine, tympanic and mastoid segment was found to be 4.28 ± 0.605 mm, 10.40 ± 1.416 mm and 12.34 ± 0.915 mm respectively in the dissected specimens. The first and second genu angle varied between 50°-90° and 90°-120° respectively. Facial canal dehiscence was present at the level of first genu in 10% of cases and at the level of tympanic segment in 33%. Distance between chorda tympani origin and stylomastoid foramen varied between 4 and 6 mm with mean value of 5.31 ± 0.603 mm. Chorda-facial angle was found to be in the range of 20° to 31° with mean of 25.30° ± 2.90°. The tympanomastoid segment of facial nerve has variations in length and in its relations with various middle ear structures. The facial canal, as it traverses the temporal bone, may display bony dehiscence, variations, and anomalies in its natural course, having its own clinical and surgical significance.

Intratympanic corticosteroid for Bell's palsy and Ramsay Hunt syndrome: Systematic review and meta-analysis

OBJECTIVE

This study aimed to reveal the efficacy and safety of intratympanic steroid therapy (ITST) in patients with Bell's palsy and Ramsay Hunt syndrome.

METHODS

A literature search was conducted in PubMed, Embase, Ichushi-Web, and Cochrane Central Register of Controlled Trials. Published randomized controlled trial and observational studies, which compared the combination of intratympanic corticosteroids with systemic corticosteroid versus systemic corticosteroid for Bell's palsy and Ramsay Hunt syndrome, were included for meta-analysis. The primary outcome was non-recovery at the end of the study follow-up. Data was analyzed using Review Manager software, and pooled odds ratio with 95% CI were calculated.

RESULTS

Three randomized controlled trial and two cohort studies met the eligible criteria, and 350 individuals included for meta-analysis. The timing of intratympanic corticosteroid was varied from once or twice a week to consecutive 10-days. Patients treated with combination of systemic corticosteroids and intratympanic corticosteroids were likely to achieve recovery of normal facial function (OR = 0.36 [95% CI 0.12-1.14]). The subgroup analysis of the timing revealed that daily ITST reduced non-recovery (OR = 0.14 [95% CI 0.04-0.50). However, non-daily ITST did not reduced non-recovery (OR 0.93 [95% CI 0.37-2.34]).

CONCLUSION

Intratympanic corticosteroid have a potential to reduce non-recovery in patients with Bell's palsy and Ramsay Hunt syndrome. The methods of intratympanic corticosteroid varied among included studies. Further well-designed randomized controlled trial is needed to confirm the effectiveness and to identify an adequate method of intratympanic corticosteroid in these patients.

Facial Nerve Dehiscence and Cholesteatoma: A Comparison between Decades

OBJECTIVES

To evaluate the incidence of facial canal dehiscence (FCD) and other intraoperative findings over the last 20 years as well as correlation with the Japanese Otological Society/European Academy of Otology and Neurotology classification in patients with cholesteatoma.

MATERIALS AND METHODS

A total of 469 patients operated from 1998 to 2018 were selected and divided into 2 groups of 10 years each.

RESULTS

Dehiscence was significantly higher in patients with a history of pathology longer than 5 years (22.7%). Higher values were observed in revision surgery, 44.4% in the first period and 41.7% in the second. The tympanic segment was the one most frequently involved, affecting 92% of patients in the first period and 97% of patients in the second. Dehiscence occurred significantly more often in patients with a semicircular canal fistula, 14.8% in the first decade and 8.8% in the second. The incidence of FCD was significantly higher in patients with primary cholesteatoma (especially in those with combined pars tensa-flaccida) than in those with a secondary acquired one, 31.5% vs 7.4% in the first period, 21.1% vs 7.4% in the second, and in those with a stage III disease, 42% in the first period, 33.3% in the second.

CONCLUSION

Patients with a shorter history of cholesteatoma as well as those not previously operated had a lower incidence of FCD. The tympanic tract of the facial nerve remains the most frequent site of dehiscence, while the association between dehiscence and fistula of the semicircular canal remains strong. Patients with combined pars tensa-pars flaccida and stage III cholesteatoma have a higher incidence of FCD.

Improved image quality of temporal bone CT with an ultrahigh-resolution CT scanner: clinical pilot studies

Purpose

Ultrahigh-resolution CT (UHRCT) with slice collimation of 0.25 mm × 160 and matrix size of 1024 × 1024 has become clinically available. We compared the image quality of temporal bone CT (TBCT) between UHRCT and conventional multidetector CT (MDCT).

Materials and methods

We retrospectively enrolled 20 patients who underwent TBCT by MDCT (matrix size, 512 × 512) and subsequently by UHRCT (matrix size, 1024 × 1024). Two independent reviewers subjectively graded delineation of normal stapes, oval window, facial nerve canal, incudostapedial joint, and tympanic tegmen. We also quantified image noise in the cerebellar hemisphere. Between MDCT and UHRCT, we compared mean subjective grades using the Wilcoxon signed-rank test and the image noise using paired t test.

Results

Grades were significantly higher with UHRCT than with MDCT for all the anatomies (P < 0.001), whereas noise was significantly higher with UHRCT than with MDCT (P = 0.002).

Conclusion

For TBCT, UHRCT shows better delineation of the fine anatomical structures compared with MDCT.

Intratympanic Steroid Treatment of Bell's Palsy in Patients with Comorbid Disease: A Preliminary Report

OBJECTIVES

This study evaluated the efficacy of intratympanic steroid injection (ITSI)as initial treatment and therecovery speed for Bell's palsy (BP)inpatients with diabetes mellitus (DM)and/or hypertension (HT).

MATERIALS AND METHODS

In total,90 patients with comorbid diseases diagnosed with BP received either ITSI (study group, n=61) or systemic steroid treatment (SST) (control group, n=29).The facial nerve function was assessed using the House-Brackmann (HB) grading system for up to 6 months or until complete recovery from BP. To investigate a relationship with the complete recovery time from BP, hematologic and baseline characteristic parameters were analyzed.

RESULTS

The complete recovery rate of the ITSI and SST groups was 47.5% and 44.8% at the 1st month, 70.5% and 89.7% at the 3rd month, and 96.7% and 100% at the 6th month of the study, respectively. Lymphocyte and neutrophil values were significantly associated with the complete recovery time from BP. No major adverse events from ITSI itself were noticed during the procedure and during the follow-up of the treatment.

CONCLUSION

Both treatment types have no superiorities over each other in initial treatment for BP in patients with comorbid diseases. ITSI is effective and safe and may avoid the unwanted side effects associated with systemic steroids inthese patients.

Does Mastoid Pneumatization Affect Facial Canal Dimensions and Distances of Facial Tympanic Segment-Scutum and Lateral Semicircular Canal-Scutum?

OBJECTIVES

In the present study, we investigated whether mastoid pneumatization affects facial canal dimensions and distances of facial tympanic segment and scutum, and lateral semicircular (LSS) canal and scutum.

METHODS

One hundred sixty-one temporal multidetector computed tomography scans were reviewed. Patients with unilateral sclerotic mastoid pneumatization (no aeration) (group 1, n = 81) and unilateral total mastoid pneumatization (100.0% aeration) (group 2, n = 80) were included. Facial canal dimensions at the labrythine, tympanic, and mastoid segments; facial canal dehiscence and length; and facial tympanic segment-scutum and LSS canal-scutum distances were evaluated.

RESULTS

In the present study, facial canal dimensions of labyrinthine, tympanic, and mastoid segments in total pneumatized mastoid group were significantly lower than sclerotic mastoids on axial and coronal images (P < 0.05). Facial tympanic segment and scutum distance of the sclerotic mastoid group was significantly lower than those of the total pneumatized mastoid group (P < 0.05). However, LSS canal-scutum distance was not different between both groups (P > 0.05). The LSS canal-scutum distance of the females was lower than those of the males (P < 0.05). Facial canal dehiscence ratio was 11.3% and 11.1% in sclerotic and total pneumatized mastoids, respectively. The mean ± SD length of the dehiscence was 2.46 ± 1.29 mm in pneumatized mastoids and 1.92 ± 0.68 mm in sclerotic mastoids.

CONCLUSIONS

In cholesteatoma cases, scutum erosion may occur. Because facial tympanic segment and scutum distance decreased in sclerotic mastoids compared with completely pneumatized ones, maximum care must be taken in the operations for avoiding to damage facial canal and nerve. Revision cases may be more difficult because of distorted anatomy. However, in pneumatized mastoids, the mean length of the facial canal was more than 2 mm, which must be kept in mind during operations.

Percutaneous Threshold of Facial Nerve Stimulation Predicts Facial Canal Dehiscence

Iatrogenic facial nerve (FN) injury is one of the most feared complications of otologic surgery. Dehiscence of the bony covering of the FN within the temporal bone increases FN vulnerability to accidental injury. High-resolution computed tomography (HRCT) of the temporal bone is used preoperatively to assess middle ear and mastoid anatomy; however, it is unreliable for detecting facial canal dehiscence. In this study, our aim was to determine if preoperative percutaneous FN stimulation could predict middle ear facial canal dehiscence. Between January 2015 and February 2017, we performed preoperative HRCT and percutaneous FN stimulation on adult patients who underwent otologic surgery at our institution. Stimulation was performed with a monopolar probe placed on the skin over the stylomastoid foramen. Electrical stimuli ranged from 0 to 40 milliamperes (mA). Recordings were made from ipsilateral facial muscles. Dependent variables included threshold to compound muscle action potential (CMAP), threshold to maximum amplitude of CMAP, and maximum amplitude of CMAP for each muscle. A retrospective chart review was performed. Seventy patients met inclusion criteria. Of the 24 with an intraoperatively confirmed dehiscence, 10 were identified preoperatively by the attending surgeon on HRCT. Averages of the lowest recorded threshold to CMAP (5.1mA v. 9.1mA), and an average of the threshold to CMAP (8.9 mA. 11.8 mA) of dehiscent versus non-dehiscent nerves were significantly different (p < .05). In conclusion, percutaneous FN stimulation is a simple and cost-effective tool that can give the surgeon important preoperative information about FN anatomy.

Association between facial nerve second genu angle and facial canal dehiscence in patients with cholesteatoma: evaluation with temporal multidetector computed tomography and surgical findings

Introduction

Otitis media, mastoiditis or the pressure effect of tumorous lesions such as cholesteatoma can be the cause of facial canal dehiscence and facial nerve paralysis. The most common segment involved in dehiscence is the tympanic segment and the second most common is the lateral aspect of the facial canal in the oval window area.

Objective

To determine the prevalence of the facial canal dehiscence and the relationship between the angle at the second genu of the facial nerve and facial canal dehiscence.

Methods

We evaluated the surgical findings in 113 patients who underwent surgery for cholesteatoma. Facial canal dehiscence was detected in 62 of the 113 patients. Patients were divided into two groups: Group 1, with dehiscence of the facial canal and Group 2, without dehiscence of the facial canal.

Results

The mean angles at the second genu of the facial nerve in Groups 1 and 2 were 117.8° ± 9.63° and 114° ± 9.9°, respectively. There was a statistically significant difference between the mean angles at the second genu for the two groups (p = 0.04).

Conclusion

In patients with dehiscence of the facial canal, the angle at the second genu was found to be wider than those without dehiscence.

Round and Oval Window Anatomic Variability: Its Implication for the Vibroplasty Technique

OBJECTIVE

The objective of this study is to evaluate the anatomical variability of round and oval window regions and its relationship with their closest structures, to determine its implication on the fitting and stabilization of the middle ear implant Vibrant Soundbridge.

METHODS

Variations of the anatomy of round and oval window regions were assessed in a total of 85 human dissected temporal bones. Afterward, we evaluated the adaptation and subsequent stabilization of the floating mass transducer (FMT) of the Vibrant Soundbridge in 67 cases in round window (RW) and in 22 cases in oval window (OW), and the influence that the variability of the different anatomical features examined had on this stabilization. We also assessed access and surgeon's view of the RW niche through the facial recess approach.

RESULTS

Stabilization of the FMT in the RW was achieved in 53 (79%) of the 67 cases; we found that the less favorable anatomical conditions for stabilization were: membrane smaller than 1.5 mm, presence of a high jugular bulb and a narrow or very narrow RW niche. Frequently, two or more of these conditions happened simultaneously. In seven cases (22%) access to the RW through facial recess approach did not allow positioning the FMT in place. OW stabilization succeeded in 18 (82%) of the 22 cases.

CONCLUSION

Round and oval window vibroplasty are difficult surgical techniques. To place the FMT directly on the OW may be easier as we do not have to drill the niche. In both regions there are some anatomical conditions that hinder fitting the FMT and even make it impossible. Once fitted, the main problem is to achieve good stabilization of the device.

Recurrent unilateral facial nerve palsy in a child with dehiscent facial nerve canal

Objective:

The dehiscent facial nerve canal has been well documented in histopathological studies of temporal bones as well as in clinical setting. We describe clinical and radiologic features of a child with recurrent facial nerve palsy and dehiscent facial nerve canal.

Methods:

Retrospective chart review.

Results:

A 5-year-old male was referred to the otolaryngology clinic for evaluation of recurrent acute otitis media and hearing loss. He also developed recurrent left peripheral FN palsy associated with episodes of bilateral acute otitis media. High resolution computed tomography of the temporal bones revealed incomplete bony coverage of the tympanic segment of the left facial nerve.

Conclusions:

Recurrent peripheral FN palsy may occur in children with recurrent acute otitis media in the presence of a dehiscent facial nerve canal. Facial nerve canal dehiscence should be considered in the differential diagnosis of children with recurrent peripheral FN palsy.

Micro-CT study of the dehiscences of the tympanic segment of the facial canal

PURPOSE

To depict the anatomy of the tympanic segment of the facial canal using a 3D visualization technique, to detect dehiscences, and to evaluate their frequency, location, shape, and size.

METHODS

Research included 36 human temporal bones (18 infant and 18 adult samples) which were scanned using a Nanotom 180N device. The final resolution of the reconstructed object was 18 µm. Obtained micro-CT data were subsequently processed by the volume rendering software.

RESULTS

The micro-CT study allowed for the 3D visualization of the tympanic segment of the facial canal and detects dehiscences in the studied material in both infants and adults. Most of the dehiscences (66.7 %) involved the inferior wall of the tympanic segment in infants as well as in adults, and were located above and backward to the oval window. The most frequent dehiscence shape was elliptic (66.7 % in infants; 50 % in adults). Furthermore, we observed dehiscences of fusiform and trapezoidal shape in infants. Length of the dehiscences in most cases ranged from 0.5 to 1.4 mm (50 % in infants; 75 % in adults).

CONCLUSIONS

Volumetric reconstructions demonstrated the course of the tympanic segment of the facial canal and its relationship with the tympanic cavity. Knowledge about the size and location of any dehiscence within the tympanic segment of the facial canal is necessary due to the surgical significance of this region. If a dehiscence occurs, there is an increased risk of injury to the facial nerve during the operations or spread of inflammation from the middle ear.

Delayed facial palsy after tympanomastoid surgery: A report of 15 cases

OBJECTIVE

To analyze potential etiology and outcomes of delayed facial palsy (DFP) after tympanomastoid surgery.

METHODS

Fifteen cases of DFP out of 1582 cases after tympanomastoid surgery were reviewed, and the potential causes and outcomes were analyzed.

RESULTS

9 out of 15 patients (60%) had fallopian canal dehiscence and facial nerve exposure in contrast to 323 of 1567 patients (20.6%) without DFP, with significant difference (P<0.01). Chorda tympani was cut or overstretched in 4 cases. There were two cases with herpes labialis and IgM antibody against varicella-zoster virus. All patients fully recovered within two months.

CONCLUSION

Fallopian canal dehiscence and facial nerve exposure was a risk factor of DFP after tympanomastoid surgery, and chorda tympani injury and viral reactivation may be triggering factors of DFP. The outcomes DFP after tympanomastoid surgery were excellent.

Intratympanic steroid injection for Bell's palsy: preliminary randomized controlled study

OBJECTIVE

To investigate adjuvant effect and safety of intratympanic steroid for the treatment of Bell's palsy.

STUDY DESIGN

Prospective, investigator blinded, randomized study.

SETTING

Tertiary referral center.

PATIENTS

Patients who received treatment for Bell's palsy from December 2007 to March 2011 were randomly divided into two groups. The control group (n = 17) was treated with systemic steroid plus antiviral agent, and intratympanic steroid injection group (IT group, n = 14) received intratympanic steroid injection combined with medications. Facial functions were evaluated on a regular basis up to 6 months.

INTERVENTION

Intratympanic steroid injection.

MAIN OUTCOME MEASURES

Facial nerve functions of initial presentation and follow-up were evaluated with House-Brackmann (H-B) system. Primary outcome was complete recovery rate of 6 months. Secondary outcomes included improvement of H-B grade within 3 weeks, time of first improvement in facial function, and cumulative recovery rate. In addition, subgroup analysis of H-B grade over than IV was performed.

RESULTS

Complete recovery rate was not different between groups. Time of first improvement was shorter in IT group (p = 0.043). And IT group had a better cumulative recovery rate (p = 0.041) and showed the significant improvement in H-B grade within 3 weeks compared with control group (p = 0.045). In severe facial palsy, complete recovery rate of IT group and control group were 80% and 50% (p = 0.16), and IT groups showed the significant facial improvement within 3 weeks (p = 0.025). And there were no major adverse effects of intratympanic injection.

CONCLUSION

Intratympanic steroid injection might be a safe and useful adjuvant treatment modality for Bell's palsy.

Facial Nerve Paralysis in Patients With Chronic Ear Infections: Surgical Outcomes and Radiologic Analysis

Objectives

The purpose of this study was to investigate the clinical features, radiologic findings, and treatment outcomes in patients of facial nerve paralysis with chronic ear infections. And we also aimed to evaluate for radiologic sensitivities on facial canal, labyrinth and cranial fossa dehiscences in middle ear cholesteatomas.

Methods

A total of 13 patients were enrolled in this study. Medical records were retrospectively reviewed for clinical features, radiologic findings, surgical findings, and recovery course. In addition, retrospective review of temporal bone computed tomography (CT) and operative records in 254 middle ear cholesteatoma patients were also performed.

Results

Of the 13 patients, eight had cholesteatomas in the middle ear, while two patients exhibited external auditory canal cholesteatomas. Chronic suppurative otitis media, petrous apex cholesteatoma and tuberculous otitis media were also observed in some patients. The prevalence of facial paralysis in middle ear cholesteatoma patients was 3.5%. The most common involved site of the facial nerve was the tympanic segment. Labyrinthine fistulas and destruction of cranial bases were more frequently observed in facial paralysis patients than nonfacial paralysis patients. The radiologic sensitivity for facial canal dehiscence was 91%. The surgical outcomes for facial paralysis were relatively satisfactory in all patients except in two patients who had petrous apex cholesteatoma and requiring conservative management.

Conclusion

Facial paralyses associated with chronic ear infections were observed in more advanced lesions and the surgical outcomes for facial paralysis were relatively satisfactory. Facial canal dehiscences can be anticipated preoperatively with high resolution CTs.

Relationships between facial canal dehiscence and other intraoperative findings in chronic otitis media with cholesteatoma

OBJECTIVE

We investigated the relationship between facial canal dehiscence and intraoperative middle ear and mastoid findings in patients operated on for cholesteatoma.

METHODS

We examined retrospectively 334 patients who had been operated on for cholesteatoma in Izmir Katip Celebi University, Ataturk Research and Training Hospital, ENT Clinic, between April 1997 and April 2010. The patients were examined for facial canal dehiscence according to age, gender, side of the ear, surgery type, first or revision surgery, localization of the facial canal dehiscence, spread of the cholesteatoma, with the presence of lateral semi-circular canal (LSCC) fistula and any defect in the ossicle chain, and destruction in the posterior wall of the external auditory canal(EAC).

RESULTS

Of the patients, 23.6% had facial canal dehiscence and detected most commonly in the right ear 28.9% and tympanic segment, 83.5%. Facial canal dehiscence was found to be 24.2-fold more common in patients with LSCC fistula and 4.1-fold more common in patients with destruction in the posterior wall of the (EAC). In patients located cholesteatoma in tympanic cavity+antrum and the tympanic cavity+all mastoid cells and with incus and stapes defect, increased incidence of dehiscence. Age, first or revision operation and canal wall down tympanoplasty (CWDT) or canal wall up tympanoplasty (CWUT) did not affect the incidence of dehiscence.

CONCLUSIONS

That the likelihood of facial canal dehiscence occurrence is increased in patients with LSSC fistulas, destruction in the posterior wall of the EAC, or a stapes defect is important information for surgeons.

Analysis of differences in facial nerve dehiscence and ossicular injury in chronic otitis media and cholesteatoma

CONCLUSION

Facial nerve dehiscence (FND) and ossicular injury occurred more frequently in patients with cholesteatomatous than non-cholesteatomatous otitis media.

OBJECTIVE

FND and ossicular injury commonly occur intraoperatively in patients with otitis media, both with and without cholesteatoma. This study was designed to analyze differences in FND and ossicular injury between patients with cholesteatomatous and non-cholesteatomatous otitis media.

METHODS

Patients who underwent tympanomastoidectomy due to otitis media from January 2010 to July 2012 were analyzed retrospectively. Clinical features (age, sex, bacteria, and severity of preoperative hearing loss) and intraoperative findings (FND and state of ossicular injury) were compared in patients with cholesteatomatous and non-cholesteatomatous otitis media.

RESULTS

Of 212 patients with otitis media, 148 (69.8%) had non-cholesteatomatous and 64 (30.2%) had cholesteatomatous otitis media. Of these groups, 88.6% and 88%, respectively, had positive bacterial cultures. Facial nerve dehiscence was detected in 41 patients (27.7%) with non-cholesteatomatous and 41 (64.0%) with cholesteatomatous otitis media. Dehiscence of the tympanic segment was most frequently observed in both groups. Ossicular injury was detected in 52 (35.1%) and 51 patients (78.1%), respectively. Erosion was most frequent in the incus, followed by the stapes and malleus.

Facial nerve canal dehiscence in chronic otitis media without cholesteatoma

The information on incidence of the facial nerve canal dehiscence in chronic otitis media is important for surgeons. The purpose of this study is to disclose the histopathologic findings of facial nerve canal dehiscence in human temporal bones with chronic otitis media. We divided the human temporal bones into two groups (age 4 years, and under 4 years of age). We evaluated the incidence and the area of the facial nerve canal dehiscence in chronic otitis media under light microscopy. Age-matched normal control temporal bones were also examined. In the age group of 4 years, 68.9 % of temporal bones with chronic otitis media and 71.9 % of controls had the facial nerve canal dehiscence. There was no significant difference between them (P = 0.61). The area of the dehiscence in temporal bones with chronic otitis media was not statistically different from controls (P = 0.53). In the age group under 4 years, 88.2 % of temporal bones with chronic otitis media and 76.5 % of controls had the dehiscence. No significant difference was found between them (P = 0.66). The area of the dehiscence in temporal bones with chronic otitis media was not statistically different from controls in the age group under 4 years (P = 0.43). In chronic otitis media, the incidence of facial nerve canal dehiscence was high and was not statistically different from controls. These results suggest that there is no association between chronic otitis media and the presence of facial nerve canal dehiscence.

Facial paralysis during air travel: case series and literature review

OBJECTIVE

We report three cases of recurrent, unilateral facial palsy associated with air travel.

METHOD

The three cases are presented, along with a brief literature review concerning barotrauma and its association with air travel and facial palsy.

RESULTS

All three patients experienced unilateral facial paralysis during air travel, accompanied by additional symptoms which varied between cases. Symptoms resolved spontaneously in all cases. Two patients received ventilation tube insertion to prevent further recurrence. Computed tomography scanning revealed no bony defect in two patients, while the third exhibited dehiscence of the facial canal which may have contributed to the condition.

CONCLUSION

Available evidence suggests that eustachian tube dysfunction can contribute to increased pressure within the middle ear, leading to neuropraxia of the facial nerve. Cases of facial paralysis associated with air travel are under-reported. Since there is no evidence-based management protocol for this condition, further investigation of its pathology is encouraged in order to improve our understanding.

The dehiscent facial nerve canal

Accidental injury to the facial nerve where the bony canal defects are present may result with facial nerve dysfunction during otological surgery. Therefore, it is critical to know the incidence and the type of facial nerve dehiscences in the presence of normal development of the facial canal. The aim of this study is to review the site and the type of such bony defects in 144 patients operated for facial paralysis, myringoplasty, stapedotomy, middle ear exploration for sudden hearing loss, and so forth, other than chronic suppurative otitis media with or without cholesteatoma, middle ear tumors, and anomaly. Correlation of intraoperative findings with preoperative computerized tomography was also analyzed in 35 patients. Conclusively, one out of every 10 surgical cases may have dehiscence of the facial canal which has to be always borne in mind during surgical manipulation of the middle ear. Computerized tomography has some limitations to evaluate the dehiscent facial canal due to high false negative and positive rates.

The value of preoperative CT scan of tympanic facial nerve canal in tympanomastoid surgery

CONCLUSIONS

The combined analysis of axial, coronal, and sagittal planes can increase the positive rate of diagnosis for dehiscence of the facial nerve canal.

OBJECTIVE

The aim of this study was to evaluate the diagnostic value of high resolution computed tomography (HRCT) scanning of the condition of the tympanic portion of the facial nerve canal in patients with chronic otitis media.

METHODS

A total of 76 ears of 72 inpatients with chronic suppurative otitis media and with cholesteatoma or granulation tissues in the attic were examined by routine HRCT. The condition (including dehiscence) of the tympanic portion of the facial nerve canal observed by CT on multi-planar images and surgical findings were recorded.

RESULTS

The condition of the tympanic portion of the facial nerve canal observed by CT could be confirmed by surgical findings in 67/76 ears, but was not confirmed in 9/76 ears. Axial-transverse images could clearly show the position and length of dehiscence on the lateral wall of the facial nerve, while coronal images were superior to axial-transverse images in showing the bony circumference of the facial nerve, and sagittal images could show the inferior wall of the facial nerve canal more clearly than images on the former planes.

Facial nerve dehiscence and cholesteatoma

OBJECTIVES

We evaluated the incidence of facial nerve dehiscence in a group of patients with cholesteatoma who underwent otologic surgery.

METHODS

We performed a retrospective study in a tertiary referral hospital of 336 patients (298 adults, 38 children) with cholesteatoma who underwent surgery in the years 1998 to 2008. Using intraoperative findings, we assessed the incidence of facial nerve dehiscence in a group of patients with cholesteatoma. We quantified, in adult versus pediatric patients and in primary versus revision surgeries, the occurrence of facial nerve dehiscence, the predisposed anatomic sites, and the coexistence of semicircular canal fistula. In a selected group of 67 patients, preoperative 0.55-mm collimation computed tomography (CT) scans were compared with the intraoperative findings.

RESULTS

The frequency of facial nerve dehiscence in this group of patients was 27.1%. The dehiscence was detected in 29.5% of the adults, but in only 7.8% of the patients 16 years and younger. Dehiscence was present in 42.3% of the patients who underwent revision surgery. The most common site of dehiscence (92.3%) was the tympanic segment. The sensitivity and specificity of CT were 69% and 87%, respectively.

CONCLUSIONS

Dehiscence of the facial nerve was found in 27.1% of patients with cholesteatoma, with a significant difference between patients of pediatric and adult ages. A dehiscent facial nerve was more commonly seen during revision surgery and more frequent in patients older than 16 years. The site of dehiscence most frequently involved by cholesteatoma was the tympanic segment. The presence of a semicircular canal fistula increases the risk of facial nerve dehiscence. Finally, the results of preoperative CT scans are encouraging for the use of CT in predicting facial nerve dehiscence.

Incidence of dehiscence of the facial nerve in 416 cases of cholesteatoma

OBJECTIVE

To determine the incidence and location of dehiscence of the facial nerve in patients with cholesteatoma.

STUDY DESIGN

Prospective case series.

SETTING

Tertiary referral centers.

PATIENTS

Charts and operative details from 1,372 consecutive chronic ear cases performed by a single surgeon were reviewed for anatomic details regarding the facial nerve. The study group was limited to the 416 ears in which cholesteatoma was confirmed at the time of surgery.

MAIN OUTCOME MEASURES

Facial nerve dehiscence was graded as present or absent for both the tympanic and mastoid segments; the location of dehiscence in the tympanic segment was further characterized in regard to its relationship to the oval window and cochleariform process. Adherence of cholesteatoma to any area of dehiscence was also noted as was the presence of any coexisting inner ear fistula.

RESULTS

Dehiscence of the tympanic segment was present in 18.8% (78 of 416) of ears in the study group. There were five cases of mastoid dehiscence. Approximately 80% of nerves that were dehiscent involved the area just superior to the oval window, and 12% involved the nerve anterior to the cochleariform process. Adults in the study were more likely to have dehiscence than those 18 years and younger (p = 0.0003, chitest), and inner ear fistula was also more common in those with dehiscence (p = 0.0118, chitest). Case studies of cholesteatoma adherent to the facial nerve are reviewed.

CONCLUSION

This study represents the largest group of patients evaluated to date for dehiscence of the facial nerve in the setting of cholesteatoma. Dehiscence is common, especially in patients with cholesteatoma, and the careful surgeon can avoid damage to the facial nerve through understanding of this anatomic variation.

Diagnosis of the pathological exposure of the mastoid portion of the facial nerve by CT scanning

CONCLUSIONS

High resolution CT imaging can provide useful information about the pathological exposure of the mastoid portion of the facial nerve before mastoid surgery and can assess the injury site of the facial nerve after operation.

OBJECTIVES

To evaluate the diagnostic value of high resolution CT scanning of pathological exposure of the mastoid portion of facial nerve and provide valuable information for otologic surgery, and to analyse the cause of facial nerve paralysis after operation.

MATERIALS AND METHODS

Routine CT scanning was used to examine patients with chronic suppurative otitis media and external auditory canal cholesteatoma preoperatively by axial-transverse and coronal views. If there was any pathological exposure of the mastoid portion of the facial nerve on CT imaging, then this was compared with intraoperative findings. In addition, one patient who had suffered postoperative facial nerve paralysis was also examined by CT scanning to determine whether any pre-existing pathological exposure of facial nerve could be found.

RESULTS

Through routine CT scanning six patients with chronic suppurative otitis media and three patients with external auditory canal cholesteatoma were found to have pathological exposure of the mastoid portion of the facial nerve. Coronal views could more clearly show the size and the position of the exposure; the corresponding surgical findings (pathological exposure) for the facial nerve could be confirmed in all nine patients. CT imaging could also show that the patient who had suffered postoperative facial nerve paralysis did indeed have pre-existing pathological exposure of the mastoid portion of the facial nerve.

Management of Iatrogenic Facial Nerve Palsy and Labyrinthine Fistula in Mastoid Surgery

A 6-year review of complications of mastoid surgery between June 1995 and June 2001 revealed five cases with serious iatrogenic complications from mastoid surgery, of which four were facial nerve palsy and two were labyrinthine fistula. One of these patients had concomitant facial nerve palsy and labyrinthine fistula. There were two cases of complete facial nerve palsy (House Brackmann grade VI) and two cases of incomplete palsy (House Brackmann grades IV and V). The second genu was the site of injury in three of the four cases. Of the four cases with facial nerve palsy, two patients had full recovery (House Brackmann grade I), one recovered only to House Brackmann grade III, and one was lost to follow-up. Both patients with labyrinthine fistula had postoperative vertigo and profound sensorineural hearing loss. The site of iatrogenic fenestration was the lateral semicircular canal in both cases.

CT and MR imaging of the normal and pathologic conditions of the facial nerve

Computed tomography (CT) and magnetic resonance imaging (MRI) are well established imaging modalities to examine the facial nerve as well as the course of the facial nerve itself. High spatial resolution is guaranteed not only in the x- and y-axis, but also in the z-axis using multislice spiral CT. With this technique, reformatted multiplanar images in oblique planes, avoiding additional examinations in the coronal plane, facilitate the delineation of the facial nerve canal. This is beneficial in patients with temporal bone trauma, malformation or osseous changes. MR has a superior soft-tissue contrast to CT that enables imaging of the facial nerve itself. Therefore the normal facial nerve as well as pathologic changes of the facial nerve is readily visualized from the brain stem to the parotid gland. This review article presents anatomy, pathology and imaging strategies in the diagnostics of the facial nerve.

Development of the fallopian canal in humans: a morphologic and radiologic study

AIMS

This study investigated the development of the fallopian canal with particular reference to the mode of ossification and dehiscences, sites of incomplete closure around the facial nerve.

BACKGROUND

The precise sequence of events surrounding ossification of the tissues around the facial nerve is uncertain. Incomplete ossification results in dehiscence of the adult structure, which places the nerve at increased risk of damage from disease processes in the middle ear and iatrogenic trauma during otologic surgery.

METHODS

Twenty-four temporal bones from 12-to 36-week human fetuses were resected. Eight temporal bones from 22-to 36-week fetuses were microsliced to produce 1.5-mm horizontal sections and radiographed. Sixteen temporal bones from 12-to 35-week fetuses were serially microtomed to produce 7-microm slices, which were stained with hematoxylin and eosin. Quantitative and qualitative analyses of these sections were performed to document patterns of closure of the primitive canal and dehiscence formation.

RESULTS

The tympanic part of the primitive fallopian canal, the facial sulcus, developed anteroposteriorly from the geniculate fossa to enclose the facial nerve. The mesenchyme that formed the facial sulcus underwent endochondral ossification, while the bone which capped or closed the sulcus developed in membrane. In the tympanic segment, permanent congenital dehiscences were elliptical and about 1 mm in length.

CONCLUSIONS

This study clarifies the mode of development of the fallopian canal, with particular reference to dehiscences, and provides a scientific basis for otologic practice.

Facial Nerve Monitoring in Middle Ear and Mastoid Surgery

HYPOTHESIS

Intraoperative electromyographic facial nerve monitoring, long accepted as the standard of care in surgery for acoustic neuroma and other cerebellopontine angle tumors, may be of aid in middle ear and mastoid surgery.

STUDY DESIGN

Retrospective series of 262 cases of middle ear/mastoid surgery in which monitoring was performed by a neurophysiologist.

METHODS

Neurophysiological monitoring events were classified as mechanical or electrical. The voltages producing facial nerve stimulation were compiled and compared with observed facial nerve dehiscence.

RESULTS

The most common use of monitoring was localization of the facial nerve by electrical stimulation (60%) or identification of mechanically evoked activity (39%). In 57 cases (36%), the first electrical stimulation event evoked a facial nerve response at less than 1 V threshold, indicating little or no bony covering. The minimum stimulation threshold throughout each of these cases was less than 1 V in 88 of the 159 cases (55%) in which stimulation was attempted. In contrast, the facial nerve was visibly dehiscent in only 35 cases (13%). Neurophysiological monitoring confirmed aberrant facial nerve course through the temporal bone in four cases resulting in cancellation of surgical treatment in two cases. Postoperative facial nerve function was preserved in all cases when present preoperatively.

CONCLUSIONS

An electrical stimulation threshold of less than 1 V is a more useful criterion of dehiscence than observation under the operating microscope. The absence of monitoring events allows safe dissection. Monitoring can help locate the facial nerve, guide the dissection and drilling, and confirm its integrity, thereby allowing more definitive surgical treatment while preserving neural function.

Distribution of psammoma bodies in the internal auditory canal and its extended areas in the human temporal bone

The internal auditory canal (IAC) and its extended areas of 27 normal human temporal bone specimens were investigated histologically for the distribution of psammoma bodies. A total of 145 +/- 25 (mean +/- SE) psammoma bodies were counted in series of every tenth 30-microm-thick section. Psammoma bodies were observed in the IAC and around the labyrinthine portion of the facial nerve (FN), the geniculate ganglion of the FN, and the posterior ampullary nerve in the singular canal. The number of psammoma bodies increases with age. We believe that psammoma bodies are a normal finding of aging in the IAC. The compression of the FN by psammoma bodies in the labyrinthine portion of the facial canal and the distribution of numerous psammoma bodies surrounding the posterior ampullary nerve in the narrow singular canal raise the questions of the involvement of psammoma bodies in the FN and in vestibular dysfunction and the presence of psammoma bodies in the subarachnoid space.

The flexible endaural tympanoplasty: pathology-guided, pathogenesis-oriented surgery for the middle ear

The flexible approach to tympanoplasty has been found to be adaptable to various forms of pathologic conditions found in the temporal bone, including inflammation and infection, congenital stenosis, benign and malignant tumors, and traumatic injuries. This approach finds its best indication among all pathologic conditions in the temporal bone, in the surgical treatment of otitis media, and its sequelae. A procedure conceived to treat this dynamic process must be adaptable to new circumstances and new findings and be ready to manage unexpected situations. The flexible tympanoplasty is a step-wise approach designed to explore the contents of the middle ear methodically and in the process disclose, confirm, and often treat disease.

Incidence of dehiscences in the fallopian canal

Fifty human temporal bones from necropsies were used to study the frequency of canal dehiscences in detail along the course of the facial nerve. Specifically, the study focused on bony dehiscences in the fallopian canal and vascular communications between the facial nerve and the surrounding bone. High frequency of dehiscences at the oval window (60%) and in the pyramidal segment (54%) were found. These dehiscence rates are in agreement with published reports. A 20% rate of dehiscences at the most anterior segment of the tympanic segment was noted and a non-reported high rate (20%) of multiple dehiscences along the course of the fallopian canal in the same temporal bone in specimens of newborns and young children. The significance of these findings in terms of clinical implications is discussed.

Postnatal development of the facial canal. An investigation based on cadaver dissections and computed tomography

The anatomy of the facial nerve canal in the adult and the prenatal development of this canal are well described in the literature. It is divided into three segments (the labyrinthine segment, the tympanic segment and the mastoid segment). However, little is known of the facial canal anatomy in the newborn and almost nothing in the child. Postnatal changes in the development of the facial canal are directly connected with the postnatal development of the temporal bone. Particularly the development of the mastoid process and the bony external ear canal contribute to the development of the third (mastoidal) portion of the facial canal. Therefore, most of the postnatal changes in the facial canal are observed in this segment. However, the second (tympanic) portion also shows some postnatal changes in its direction caused by the changes of the squamous bone. The most significant changes take place during the first four years after birth. Provided with the anatomical description of the entire facial canal in the child, it is also easy to identify the canal on computed tomography scans. In summary, the first and the second part of the facial canal in the child are almost similar to the adult in length and in width; the only change from the newborn to the adult is in the direction of the second part which is more horizontal in the adult than during early childhood. The most significant changes are the changes in the length of the mastoidal part, the change in the position of the stylomastoid foramen and the change of the divergence of the chorda tympani.

Facial canal dehiscence: a report of 1,465 stapes operations

We retrospectively reviewed 1,465 stapes operations for facial canal dehiscences. The incidence of facial canal dehiscence was found to be 11.4%. A facial canal dehiscence with protrusion of the facial nerve is more common than a dehiscence without protrusion. In addition, 3 cases (0.2%) had a herniation of the facial nerve. Our data suggests that heredity could be one of the factors associated with a facial canal dehiscence. If an operated ear shows a dehiscent facial canal, there is a 29% possibility that the contralateral ear also has a dehiscence. Bilaterality of facial canal dehiscence is, therefore, exceptional.

CT detection of facial canal dehiscence and semicircular canal fistula: comparison with surgical findings

OBJECTIVE

The purpose of this study was to determine the accuracy of high resolution CT (HRCT) in the detection of facial canal dehiscence and semicircular canal fistula, the preoperative evaluation of both of which is clinically very important for ear surgery.

MATERIALS AND METHODS

We retrospectively reviewed the HRCT findings in 61 patients who underwent mastoidectomy at Yamagata University between 1989 and 1993. The HRCT images were obtained in the axial and semicoronal planes using 1 mm slice thickness and 1 mm intersection gap.

RESULTS

In 46 (75%) of the 61 patients, the HRCT image-based assessment of the facial canal dehiscence coincided with the surgical findings. The data for the facial canal revealed sensitivity of 66% and specificity of 84%. For semicircular canal fistula, in 59 (97%) of the 61 patients, the HRCT image-based assessment and the surgical findings coincided. The image-based assessment in the remaining two patients, who both had massive cholesteatoma, was false-positive.

CONCLUSION

HRCT is useful in the diagnosis of facial canal dehiscence and labyrinthine fistula, but its limitations should also be recognized.

Computer-aided three-dimensional reconstruction and measurement of facial canal dehiscence

Location, shape and dimensions of the dehiscence in the facial canal to the middle ear space were studied in 20 temporal bones obtained from 19 individuals aged 1 day to 72 years at death by using our computer reconstruction and measurement method. The most frequent site of dehiscence was the oval window area (70%), particularly in its posterior half and on the inferior to inferomedial aspect of the canal. The shape of the dehiscence tended to be oval in the oval window area, but rather irregular in the other areas. The dehiscence ranged from 0.4 to 2.64 mm in length, from 0.12 to 1.59 mm in width, and from 0.03 to 1.87 mm2 in surface area. Proximity of these dehiscences to the field of otological surgery is stressed.