Width of the normal facial canal measured by high-resolution cone-beam computed tomography

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.

Evaluation of the relationship between tympanic plate morphology and degenerative bone changes of condyle and articular eminence

INTRODUCTION

This study aimed to evaluate the relationship between tympanic plate morphology and degeneration of temporomandibular joint (TMJ) condyle and articular eminence (AE).

MATERIAL AND METHODS

Cone beam computed tomography images of 700 patients (345 males, 355 females) were evaluated. The prevalence and location of tympanic plate pneumatization (TPP) and foramen tympanicum (FT) were recorded. Sagittal scans of the TMJs were classified according to the degenerative bone changes of condyle and AE (flattening, osteophytes, erosion, sclerosis, and subcortical cysts).

RESULTS

TPP was found in 106 of 700 patients (15.2%) while FT was found in 165 (23.2%) of the patients. TPP and FT were bilateral in 52 (49.1%) patients and 46 (27.9%) patients, respectively. The mean axial diameter of FT was 2.53mm and the mean sagittal diameter was 2.52mm. The most common degenerative changes for condyle and AE were flattening.

CONCLUSION

To know these structures is important for surgical operations in the region of TMJ and ear to prevent complications. CBCT is useful to evaluate these anatomical landmarks and the relationship between them and the degenerative bone changes of condyle and AE.

Evaluation of artifacts of cochlear implant electrodes in cone beam computed tomography

Purpose

Cone Beam Computed Tomography (CBCT) offers a valid alternative to conventional Computed Tomography (CT). A possible radiation dose reduction with the use of CBCT in postoperative imaging of CIs is of great importance. Whether the visualization of Cochlear Implant (CI) electrodes in CBCT correlates with the radiation dose applied was investigated in this study.

Methods

We compared the visualization quality of Contour Advance CIs to Straight CIs from Cochlear using CBCT with varying tube parameters on whole-head specimen.

Results

The internal diameter of the cochlea decreases from base to apex, resulting in a significantly different intracochlear positioning of the two tested CI models. While electrodes of the Contour Advance series are located close to the modiolus, thus closer to the spiral ganglion neurons, those of the Straight series are located further away. The artifact portion of the electrode amounts to 50–70% of the radiological diameter of the electrode. An increase in artifact portion from the base (electrode #1 approx. 50%) to the apex (electrode #20 approx. 70%) of the cochlea was observed. The visualization of electrodes in the medial and apical part of the cochlea is limited due to artifact overlapping. There was no correlation between the artifact size and the applied radiation dose.

Conclusion

The results indicate that a reduction of the radiation dose by up to 45% of the currently applied radiation dose of standard protocols would be possible. Investigations of the effects on subjective image quality still need to be performed.

Can MDCT Scan of the Temporal Bone Looking at Pneumatization Predict Surgical Vulnerability of the Facial Nerve?

OBJECTIVES

The aim of this study is to investigate the scutum-cochleariform process (CP) and scutum-promontorium distances according to the mastoid pneumatization condition.

METHODS

Two hundred temporal multidetector computed tomography scans (90 males and 110 females) were evaluated retrospectively. The scutum-CP and scutum-promontorium distances were measured. Facial canal dehiscence (FCD) in the tympanic segment and mastoid pneumatization were also evaluated.

RESULTS

The distances between scutum-CP and scutum-promontorium were not different between males and females and between right and left sides. Facial canal dehiscence in the tympanic segment was detected: 5.6% (right) and 7.8% (left) in males and 5.5% (right) and 10.0% (left) in females. Grade 4 (100%) pneumatization was detected mainly in 55.6% to 57.8% of the patients in both genders. Grade 0 (0%) pneumatization (sclerosis) was detected in 22.2% to 28.2% of both males and females. In more pneumatized mastoids, the scutum-CP and scutum-promontorium distances increased. In sclerotic mastoids, the scutum-CP and scutum-promontorium distances decreased. Facial canal dehiscence rates were not related to the mastoid pneumatization levels.

CONCLUSION

Cochleariform process is an important landmark to localize the tympanic segment of the facial canal. In sclerosed mastoids, scutum-CP and scutum-promontorium distances decreased. There was no relationship between FCD rates and mastoid pneumatization levels. It may be due to the development of FCD that occurs during the intrauterine period. In endoscopic and classic ear surgeries, mastoid pneumatization must be evaluated preoperatively to avoid facial nerve injuries.

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

PURPOSE

The main objective of the study was to examine the morphometric development of the facial canal in temporal bones aged from one to 18 years for pediatric otosurgeons and neurosurgeons.

METHODS

The study was performed on 41 patients including cochlear implantation cases (20 females and 21 males) with a mean age of 6.44 ± 5.79 years. All the measurements belonging to the facial canal including the length, width and angles of its segments were performed using the data of computed tomography assessment.

RESULTS

The numerical data of the facial canal segments were not different in terms of sexes or sides, statistically (p > 0.05). The width of the labyrinthine segment (p = 0.145), the length of the tympanic segment (p = 0.555), the first (p = 0.067) and second (p = 0.060) genu angles seemed to reach adult size at two years of age. In addition, the length of the labyrinthine segment (p = 0.064) and the width of the mastoid segment (p = 0.264) seemed to attain adult size at four years, while the width of the meatal foramen (p = 0.264) seemed to arrive adult size at seven years. However, the length of the mastoid segment and the width of the tympanic segment were developing independently of increasing age between 1 and 18 years.

CONCLUSION

Our data suggested that, contrary to the general acceptance in the literature, the dimension of the facial canal segments show remarkable changes during the transition from intrauterine life to adult life. The regression equations representing the facial canal growth dynamic in children may be useful for otosurgeons to estimate the size of its segments and to prevent iatrogenic injury during early childhood surgeries such as cochlear implantation.

Is there a relationship between mastoid pneumatisation and facial canal dimensions?

OBJECTIVE

To evaluate mastoid pneumatisation and facial canal dimensions.

METHOD

In this retrospective study, 169 multidetector computed tomography scans of temporal bone were reviewed. Facial canal dimensions were evaluated at the labyrinthine, tympanic and mastoid segments using axial and coronal multidetector computed tomography scans of temporal bone. Mastoid pneumatisation and facial canal dehiscence were evaluated. Facial canal dehiscence was measured if it was found to be present.

RESULTS

This study showed that facial canal dimensions decreased in pneumatised mastoids. Facial canal dimensions in females were smaller than in males. Facial canal dehiscence was detected in 5.9 per cent and 6.5 per cent of the patients on the right and left sides, respectively. No correlations were found between facial canal dehiscence and mastoid pneumatisation. The length of dehiscence was 1.92 ± 0.44 mm (range, 0.86-2.51 mm) on the left side. In older subjects, left facial canal dehiscence was detected more, and the length of the dehiscence increased.

CONCLUSION

This study concluded that during surgery, facial canal dehiscence should be kept in mind in order to avoid complications.

Possibility of differentiation of cochlear electrodes in radiological measurements of the intracochlear and chorda-facial angle position

Due to an increasing number of cochlear implantations, quality control has become more important. In addition to intraoperative biophysical measurements, radiological imaging is another possibility. An upcoming technique regarding this is Cone Beam CT (CBCT). Sixty-five data sets (35 Nucleus Contour Advance–Cochlear; 30 Flex Soft–MedEl) of postoperative imaging by CBCT (Accu-I-tomo F17, Morita, Kyoto, Japan) underwent further evaluation. Insertion angle, height of the cochlea, distance of the electrode to the medial or lateral wall, angle between chorda tympani and facial nerve and the precise position of the electrode cable in the facial-chordal angle were determined. The typical difference between the perimodiolar and lateral course of the electrodes could also be shown in radiological measurements. This demonstrates the accuracy and advantage of CBCT in visualisation of small structures with fewer metal artifacts. Furthermore, in 75% of patients, the angle of the chorda and facial nerve could be visualised. Significant differences in dependence of the electrode type for the relation of them to the facial nerve could be seen. In conclusion, CBCT achieves reliable visualisation and detailed imaging-based measurements of the intracochlear position of different cochlea electrodes. Additionally, clinically known differences can be reproduced. Even visualisation of the position of the electrode in the chorda-facial angle is possible. Therefore, CBCT is a useful tool in intra- and postoperative control of cochlear implants.

Clinically relevant human temporal bone measurements using novel high-resolution cone-beam CT

OBJECTIVE

To test the feasibility of measuring fine temporal bone structures using a newly established cone-beam computed tomography (CBCT) system.

MATERIALS AND METHODS

Six formalin-fixed human cadaver temporal bones were imaged using a high-resolution CBCT system that has 900 frames and copper + aluminum filtration. Fine temporal bone structures, including those of the facial nerve canal and vestibular structures, were identified and measured.

RESULTS

The fine structures of the middle ear, including the tympanic membrane, tendon of the tensor tympani, cochleariform process of the semicanal of the tensor tympani, pyramidal eminence, footplate of the stapes, full path of the facial nerve within the temporal bone, supralabyrinthine space, semicircular canals, pathway of the subarcuate canal, and full path of the vestibular aqueduct, were clearly demonstrated. The vestibular aqueduct has a midpoint width of 0.4 ± 0.0 mm and opercular width of 0.5 ± 0.1 mm (mean ± SD). The length of the internal acoustic meatus was 10.6 ± 1.2 mm (mean ± SD), and the diameter of the internal acoustic meatus was 3.7 ± 0.3 mm (mean ± SD).

CONCLUSION

This novel high-resolution CBCT system has potentially broad applications in the diagnosis of inner ear disease and in monitoring associated pathological changes, surgical planning, navigation for the ear surgery, and temporal bone training.