Morphometric properties of the facial canal in children: A retrospective computed tomography study

Comparison of cone beam-computed and micro-computed tomography data for measuring facial canal dehiscence

BACKGROUND

Selecting the correct imaging technique for critical anatomical structures is essential in descriptive studies and for supporting clinical applications. Facial canal dehiscence poses a significant risk for iatrogenic facial nerve injuries during middle ear surgeries. Accurate imaging is critical for surgical planning and minimizing complications. Detection of facial canal openings in the clinic is performed using imaging methods such as high-resolution computed tomography (HRCT). Studies have shown that the sensitivity of this method is approximately 66%. A high-resolution, 3D imaging method was used to measure the sensitivity of HRCT in the most accurate way.

AIMS/OBJECTIVES

This study aimed to compare two radiological methods for measuring facial canal dehiscence. Specifically, we compared cone-beam computed tomography (CBCT) with high-resolution micro-computed tomography (micro-CT).

MATERIALS AND METHODS

Thirty-six temporal bone specimens without external defects were used. The specimens were scanned using both CBCT and micro-CT. The presence of facial canal dehiscence in the tympanic segment of the facial nerve (FN) was evaluated. A paired sample t-test was used for statistical analysis, with significance set at p < 0.05.

RESULTS

Facial canal dehiscence was detected in 10 bones on micro-CT images, while 26 bones appeared intact. In contrast, CBCT images showed dehiscence in 25 bones, with 11 bones intact. Additionally, the mean dehiscence width was 3.469 mm (range: 1.577-8.921 mm) in micro-CT images, compared to 1.279 mm (range: 0.670-9.354 mm) in CBCT images. In the 10 bones where dehiscence was identified by both methods, the average width of the dehiscence measured 5.347 mm (range: 1.840-9.354 mm) in the CBCT images. The difference in measurements between CBCT and micro-CT was statistically significant (p < 0.05).

CONCLUSIONS AND SIGNIFICANCE

The low resolution of CBCT was insufficient for visualizing the thin bony tissue lining the facial canal. These findings suggest that the frequency of facial canal dehiscence measured in preoperative CBCT images may be overestimated compared to actual anatomical conditions. These findings provide critical insights for preoperative evaluation and surgical planning in middle ear procedures.

An evaluation of morphometry and dehiscence of facial canal: a systematic review and meta-analysis of observational studies

INTRODUCTION

The facial canal (FC) is an extensive bony canal that houses the facial nerve and occupies a central position in the petrous part of temporal bone. It is of utmost significance to otologists due to its dehiscence and relationship to the inner or middle ear components. The main objectives of current investigation are to detect variations in the reported values ​​of FC anatomy that may occur due to different methodology and to elucidate the influence of age and ethnic factors on the morphological features of FC.

METHODS

The methodology is adapted to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Pooled weighted estimation was performed to calculate the mean length, angle, and prevalence of dehiscence.

RESULTS

The cross-sectional shape of FC varied from circular to ellipsoid index and is 1.45 [95% CI, 0.86-2.6]. The mean length of the FC is 34.42 mm [95% CI, 27.62-40.13 mm] and the mean width or diameter is 1.35 mm [95% CI, 1.013-1.63 mm]. The length of the FC in fetuses and children is 21.79 mm [95% CI, 18.44-25.15 mm], and 26.92 mm [95% CI, 23.3-28.3 mm], respectively. In meta-regression, age is observed as a predictor and accounts for 36% of the heterogeneity. The prevalence of FC dehiscence in healthy temporal bones is 29% [95% CI, 20-40%].

CONCLUSION

The different segments of the FC exhibit significant variability and an unusually high incidence of dehiscence, which could potentially have clinical implications for the etiopathogenesis of facial nerve dysfunction.

Morphometric properties of the fallopian canal: comparison of two nations with different ethnic origins

PURPOSE

To determine the widths of fallopian canal segments (labyrinthine segment, geniculate ganglion, tympanic segment mastoid segment and stylomastoid foramen), in two nations with different ethnic origins, and to analyze the differences in between.

METHODS

We retrospectively analyzed temporal computerized tomographies of 102 individuals including 38 Turks and 64 Syrians. The widths of right and left labyrinthine (LS), tympanic (TS), mastoid (MS), geniculate ganglion (GG) and stylomastoid foramen (SF) segments of the fallopian canal were measured.

RESULTS

The narrowest segment was LS (right: 1.04 ± 0.23 mm, left: 1.03 ± 0.22 mm) and the widest segment was SF (right: 1.82 ± 0.41 mm, left: 1.85 ± 0.35 mm). From the widest to the narrowest, the widths of the FC segments were sorted as SF > GG > MS > TS > LS. The widths of the fallopian canal segments were similar between right and left sides, and between males and females (p > 0.05). Our results indicated that both right and left GG were significantly wider in Turks (p < 0.001 for both), however right LS (p < 0.001) and left TS (p = 0.005) were significantly wider in Syrian refugees. Two groups did not show any differences for the widths of other FC segments (p > 0.05).

CONCLUSIONS

Nations of different ethnic origins may have differences concerning the widths of some segments of the fallopian canal. Further studies with a larger sample size including clinical data of the patients are needed to clarify our findings, and to determine whether these differences have any clinical implications.

Radioanatomic Assessment of the Geniculate Ganglion Dehiscence and Dimension: A Cadaveric Study

OBJECTIVE

The main aim of this study placed on cadavers was to compare the data related to geniculate ganglion (GG) dehiscence and dimension obtained from computed tomography (CT) with dissection values.

METHODS

This study was conducted on 20 temporal bones obtained from 10 cadavers (4 female, 6 male) aged between 45 and 92 (71.50 ± 15.98) years. All the measurements related to GG dimension were performed with a CT scanner and microdissection.

RESULTS

The size of GG including its area, length, and width did not show statistically significant differences in terms of sex, side, and assessment method (CT and cadaveric dissections). The dehiscent GG was observed in 6 (30%) and 5 (25%) out of 20 temporal bones in CT and cadaveric dissections, respectively. The presence and absence of GG dehiscence in CT and dissection were similar in 75%.

CONCLUSIONS

Our findings based on dissection data suggest that radiologic evaluation of dehiscent GG detection might be erroneous by 25%, which highlights that surgeons should be careful when lifting the dura to prevent GG injury during middle cranial fossa surgical approaches. On the other hand, there was no statistical difference between CT and dissection measurements related to GG dimension.