Abstract
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.
1
Introduction
Cholesteatoma is the accumulation of stratified squamous epithelium showing keratinization in the middle ear or in other pneumatized areas of temporal bone. Most cases with facial paralysis due to chronic otitis media have cholesteatoma in the middle ear . Damage that may occur to the facial nerve is the biggest fear of the otologic surgeon. The likelihood of facial nerve damage during the operation can be minimized by better understanding ear anatomy and increased surgical experience.
In histological studies of the temporal bones of normal humans, the prevalence of facial canal dehiscence has been reported to be 25–57% . Although progress in otologic surgery is encouraging, the incidence of iatrogenic facial nerve damage due to cholesteatoma-related bone erosion and anatomical variations in the facial nerve was 0.6–3.6%; the corresponding rates were 4–10% in patients who underwent revision operations .
Although facial canal dehiscence is generally detected in the tympanic segment and at the level of fenestra ovalis, it may also be observed at the level of geniculate ganglion and in the mastoid segment. In the presence of dehiscence, the facial nerve may be damaged during the dissection of the cholesteatoma from the middle ear cavity, epitympanum, and mastoid cavity . In this study, we sought to report results that will facilitate determination of the incidence of facial canal dehiscence and the localization of the dehiscence and avoidance of damage to the facial nerve in patients operated on for cholesteatoma.
2
Materials and methods
We examined retrospectively 334 patients with cholesteatoma who had been operated on for chronic otitis media in Izmir Katip Celebi University, Atatürk Research and Training Hospital, Ear, Nose, and Throat Clinic between April 1997 and April 2010. To avoid repetition of the same data in ears that had been operated on more than once, the data for one ear were included in the study. Of the patients, seven had undergone bilateral operations. 134 of all the patients of the computed tomography (CT) in the temporal bone investigated in terms of facial canal dehiscence.
Based on the patient files, age, gender, the side of the operated ear, and type of surgery and findings were determined. The data were examined in terms of the presence or absence of facial canal dehiscence, the localization and incidence of cholesteatoma, lateral semi-circular canal (LSCC) fistula, condition of the ossicle chain, the presence or absence of destruction in the posterior wall of the external auditory canal, and the presence of pre- and post-operative facial paralysis. Subjects were classified according to whether they underwent a first or a revision operation. The procedures applied during the operation were classified as canal wall down tympanoplasty (CWDT) and canal wall up tympanoplasty (CWUT). The ages of the patients were classified as below or above 18 years.
In the patients with facial canal dehiscence, the localization of the dehiscence was classified as being in the tympanic segment, in the mastoid segment, or in the tympanic + mastoid segments, based on the operation reports. The localization of the cholesteatoma was classified as attic + antrum, attic + meso-hypotympanum (tympanic cavity), tympanic cavity + antrum, or tympanic cavity + all mastoid cells. Patients in whom defects of the ossicle chain were identified were classified as having an incus defect, incus + malleus defect, defect of incus + stapes suprastructure, or defects in all ossicles.
Statistical analyses were performed using the SPSS software (ver. 15 for Windows). Chi-squared and Fisher’s exact tests were used to detect significant differences between frequencies. The t -test was used to detect significant differences between mean values. To determine the likelihood of simultaneous observation of two parameters, the odds ratio was calculated. P values < 0.05 were considered to indicate statistical significance.
2
Materials and methods
We examined retrospectively 334 patients with cholesteatoma who had been operated on for chronic otitis media in Izmir Katip Celebi University, Atatürk Research and Training Hospital, Ear, Nose, and Throat Clinic between April 1997 and April 2010. To avoid repetition of the same data in ears that had been operated on more than once, the data for one ear were included in the study. Of the patients, seven had undergone bilateral operations. 134 of all the patients of the computed tomography (CT) in the temporal bone investigated in terms of facial canal dehiscence.
Based on the patient files, age, gender, the side of the operated ear, and type of surgery and findings were determined. The data were examined in terms of the presence or absence of facial canal dehiscence, the localization and incidence of cholesteatoma, lateral semi-circular canal (LSCC) fistula, condition of the ossicle chain, the presence or absence of destruction in the posterior wall of the external auditory canal, and the presence of pre- and post-operative facial paralysis. Subjects were classified according to whether they underwent a first or a revision operation. The procedures applied during the operation were classified as canal wall down tympanoplasty (CWDT) and canal wall up tympanoplasty (CWUT). The ages of the patients were classified as below or above 18 years.
In the patients with facial canal dehiscence, the localization of the dehiscence was classified as being in the tympanic segment, in the mastoid segment, or in the tympanic + mastoid segments, based on the operation reports. The localization of the cholesteatoma was classified as attic + antrum, attic + meso-hypotympanum (tympanic cavity), tympanic cavity + antrum, or tympanic cavity + all mastoid cells. Patients in whom defects of the ossicle chain were identified were classified as having an incus defect, incus + malleus defect, defect of incus + stapes suprastructure, or defects in all ossicles.
Statistical analyses were performed using the SPSS software (ver. 15 for Windows). Chi-squared and Fisher’s exact tests were used to detect significant differences between frequencies. The t -test was used to detect significant differences between mean values. To determine the likelihood of simultaneous observation of two parameters, the odds ratio was calculated. P values < 0.05 were considered to indicate statistical significance.
3
Results
Of the total of 334 subjects enrolled in the study, 192 (57.5%) were male and 142 (42.5%) were female. Their mean age was 33.1 (range, 6-69) years.
In 79 of the 334 subjects (23.6%), facial canal dehiscence was detected perioperatively. Of these 79 subjects, 66 had dehiscence in the tympanic segment (83.5%), 9 had dehiscence in the mastoid segment (11.4%), and 4 in the tympanic + mastoid segments (5.1%). The difference between the localization of the dehiscence was statistically significant (chi squared test, P < 0.001).
Of the 334 subjects, 61 were aged below 18 years and 273 were aged above 18 years at the time of the operation. The incidence of facial canal dehiscence was 21.3% ( n = 13) in subjects aged below 18 years, 24.2% ( n = 66) in subjects aged 18 years and above, and 23.6% in all subjects. Thus, the age groups showed no statistically significant difference in terms of facial canal dehiscence (chi-squared test, P = 0.634).
Of the 334 subjects enrolled, 173 had operations on their right ear and 161 on their left ear. While facial canal dehiscence was observed in 50 of 173 operations performed on the right ear (28.9%), it was detected in 29 of 161 operations performed on the left ear (18%; this difference was statistically significant: chi-squared test, P = 0.019).
In our study, 329 subjects were operated on using a canal-wall-down technique and 14 using a canal-wall-up technique. The difference between the canal-wall-down (23.5%, n = 75) and canal-wall-up (28.5%, n = 4) techniques in terms of the incidence of facial canal dehiscence was not statistically significant (Fisher’s exact test, P = 0.748).
While 311 subjects (93%) were operated on for the first time, 23 (7%) underwent revision procedures. First operations in the subjects who had revision operations had been performed at other institutions. While 72 of the subjects who were operated on for the first time (23.2%) had facial canal dehiscence, seven of those who underwent revision operations (30.4%) showed facial canal dehiscence. This difference was not statistically significant (chi-squared test, P = 0.428).
The cholesteatoma was located in the attic in 32 (9.5%) subjects, in the attic + antrum in 113(33.8%) subjects, in the attic + meso-hypotympanum (tympanic cavity) in 55 (16.4) subjects, in the tympanic cavity + antrum in 105 (31.4%) subjects, and in the tympanic cavity + all mastoid cells in 29 (8.6%) subjects. In subjects in whom the cholesteatoma was located in the tympanic cavity + antrum and the tympanic cavity + all mastoid cells, the incidence of facial canal dehiscence was high. However, the difference between cholesteatoma localization in terms of the incidence of dehiscence was not statistically significant (chi-squared test, P < 0.001).
In our study, lateral semi-circular canal fistula was detected in 26 patients (7.8%), 22 of whom showed facial canal dehiscence (84.6%). The incidence of LSCC fistula was 7.8% among the 334 subjects, 27.8% among those with facial canal dehiscence, and only 1.6% among those in whom facial canal dehiscence was not detected. The correlation between LSCC fistula and facial canal dehiscence was statistically significant (chi-squared test, P < 0.001). For the concomitance of LSCC fistula and facial canal dehiscence, the odds ratio was 24.2; that is, the incidence of facial nerve dehiscence in subjects with LSCC fistula was 24.2-fold more common ( Table 1 ).
| LSSC fistula | Facial canal dehiscence | Total | P value | |
|---|---|---|---|---|
| Absence | Presence | |||
| Absence | 251 | 57 | 308 | < 0.001 |
| Presence | 4 | 22 | 26 | |
| Total | 255 | 79 | 334 | |
Among the 26 subjects found to have LSCC fistulas, 12 had the cholesteatoma localized in the tympanic cavity + all mastoid cells and 11 in the tympanic cavity + antrum. In subjects in whom the cholesteatoma was localized only in the attic, no LSCC fistulas were identified. Cholesteatoma was localized in the attic + antrum in two subjects and in the attic + meso-hypotympanum (tympanic cavity) in one subject. Of our subjects, 310 (93%) had a defect in the ossicle chain, and of 24 subjects with an intact ossicle chain, 6 had cholesteatoma localized in the attic + antrum, 15 in the attic + antrum, and 3 in the attic + meso-hypotympanum (tympanic cavity). In subjects in whom cholesteatoma was limited to the attic or attic + antrum, cholesteatoma was more common and was found to be intact, with statistical significance, compared to other subjects (Fisher’s exact test, P < 0.001) ( Table 2 ). While only 1 of 24 subjects (4.2%) with an intact ossicle chain had facial canal dehiscence, 78 of 310 subjects with ossicle chain defects (25.2%) showed facial canal dehiscence. Of 78 subjects who showed facial canal dehiscence in the presence of an ossicle chain defect, 8 had isolated incus defects, 8 had incus + malleus defects, 33 had incus + stapes suprastructure defects, and 29 had erosion in all ossicles. In the subjects in whom the stapes was affected, the incidence of facial canal dehiscence was high. There was a statistically significant difference between the incidences of facial canal dehiscence according to ossicle chain defect localization (chi-squared test, P < 0.001) ( Table 2 ).
| Ossicular chain defect | Facial canal dehiscence | total | P value | |
|---|---|---|---|---|
| Absence | Presence | |||
| Isolated incus | 61 | 8 | 69 | < 0.001 |
| Incus + malleus | 60 | 8 | 68 | |
| Incus + stapes suprastructure | 73 | 33 | 108 | |
| All ossicles | 36 | 29 | 65 | |
| Total | 232 | 78 | 310 | |
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