The Feasibility of Retrofacial Approach for Cochlear Implantation

Impact of Sigmoid Sinus Anatomy on Assessing the Feasibility of the Retrofacial Access to the Entire Jugular Fossa Before Surgery

BACKGROUND AND OBJECTIVES

The jugular fossa (JF) is a challenging area for surgical approaches because of its complex anatomy and proximity to neurovascular structures. The study evaluates the feasibility of the neuronavigated microsurgical transmastoid extended infralabyrinthine extradural retrofacial approach (mTEIER-A) in human head specimens for accessing the entire intraosseous JF in relation to the position of the sigmoid sinus (SS), horizontal angle of attack, and size of the SS.

METHODS

The mTEIER-A was performed on human head specimens. Before dissection, the position of the SS, horizontal angle of attack, and size of the SS were measured on tilted axial high resolution computed tomography scans; after dissection, access to the lateral aspect of the JF on dissected human head specimens and on postoperative high-resolution computed tomography scans was examined. The position of the SS was classified relative to a predefined reference line, and the feasibility of retrofacial access was documented.

RESULTS

SS positions located medial to the reference line (P1) and horizontal angles >12.5° significantly enhance retrofacial access to the lateral aspect of the JF, whereas the size of the SS has a limited impact.

CONCLUSION

Depending on the position of the SS and the horizontal angle of access, mTEIER-A provides sufficient retrofacial access to the lateral aspect of the JF. These findings emphasize the need for precise preoperative planning and suggest that mTEIER-A could minimize the need for more invasive approaches, potentially reducing related morbidity. Further clinical studies are recommended to validate these findings.

Evaluation of subarcuate canal on CT images in the perspective of clinical basis

OBJECTIVES

The aim of our study to contribute to the field of morphometrics by including measurements of the SAC and SAF and their distances from surrounding structures, particularly for surgeons involved in retrosigmoid approach for internal acoustic meatus tumor surgery and cerebellopontine angle surgery. Although there is limited information in the literature regarding the role of the subarcuate fossa (SAF) and subarcuate canal (SAC), it has been suggested that the SAC may be a potential pathway for infection from the middle ear to the posterior cranial fossa, and cerebellar abscesses may have this origin.

METHODS

For the images of our study, computerized tomography images of 118 individuals (59 females and 59 males) between the ages of 18-65 who applied to Bayındır Health Group.

RESULTS

The width of the cranial opening of the subarcuate canal was determined as 44 ± 0.54 mm, width of the labyrinth opening of the subarcuate canal was determined as 60 ± 0.42 mm, Length of the subarcuate canal was determined as 8.79 ± 2.31 mm, width of the subarcuate canal was determined as 5.54 ± 1.75 mm, and depth of subarcuate fossa was determined as 1.67 ± 0.69 mm. The distance of the cranial opening of the subarcuate canal to the superior semicircular canal (SSC-SAC/C) was measured as 5.33 ± 1.81 mm, The distance of the labyrinth opening of the subarcuate canal to the superior semicircular canal (SSC-SAC/L) was measured as 3.90 ± .98 mm, length of the petrous part of the temporal bone medial to the anterior semicircular canal measured from the apex to the SSCD (PLM) was measured as 33.56 ± 0.42 mm. No statistically significant differences were found between the right and left sides.

CONCLUSIONS

The morphometric measurements obtained in this study can provide useful information for neurosurgeons, neurotologist and otolaryngologists involved in retrosigmoid approach for internal acoustic meatus tumor surgery and cerebellopontine angle surgery, and for patients undergoing cochlear implant planning with a retrofacial approach.

Sinus tympani revisited for planning retrofacial approach-radiologic study in pneumatized temporal bones and its surgical implications

BACKGROUND AND PURPOSE

Retrofacial approach (RFA) is an access route to sinus tympani (ST) and it is used in cholesteatoma surgery, especially when type C ST is encountered. It may also be used to gain an access to stapedius muscle to assess the evoked stapedius reflex threshold. The primary object of this study was to evaluate the morphology of sinus tympani and its relationship to facial nerve (FN) and posterior semicircular canal (PSC) in context of planning retrofacial approach in pneumatized temporal bones.

METHODS

CBCT of 130 adults were reviewed. The type of sinus tympani was assessed according to Marchioni's classification. Width of entrance to sinus tympani (STW), depth of ST (STD), distance between the posterior semicircular canal and facial nerve (F-PSC), distance between the latter plane to the floor of ST at the right angle (P-ST) were measured at level of round window (RW) and pyramidal ridge (PR).

RESULTS

All of the bones were well-aerated and classified in Dexian Tan pneumatization group 3 or 4. Type B of ST is dominant (70.8%) in adult population with no history of inflammatory otologic diseases, followed by type C (22.7%) and then type A (6.5%). The depth of ST (STD) presented significant deviations (ANOVA, p < 0.05) among all three types. STW reaches greater values on the level of PR. F-PSC does not correlate with type of ST. In over 75% of examined type C sinus tympani the distance P-ST was less than 1 mm.

CONCLUSIONS

The qualitative classification of the sinus tympani into types A, B and C, introduced by Marchioni is justified by statistically significant differences of depth between individual types of tympanic sinuses. The STW distance reaches greater values inferiorly-it may suggest that RFA should be performed in infero-superior manner rather than opposite direction. Preoperative assessment of temporal bones CT scans gives very important information about size of sinus tympani and distance between FN and PSC.

Cochlear Implantation: The use of OTOPLAN Reconstructed Images in Trajectory Identification

OBJECTIVES

This study aimed to define the best electrode trajectory line in cochlear implant (CI) surgery using the OTOPLAN (otology planning software) reconstructed 3D model and to investigate the surgical distance of the retro-facial approach as a direct access to the round window.

METHODS

Computed tomography (CT) scans of the normal temporal bone were included for analysis in this study. OTOPLAN reconstruction was used to build 3D models with specific ear structures for study analysis.

RESULTS

Twenty-five scans were included; the average age at the time of CT scan was 6.8±12 years. Twelve scans (48%) were right-sided and thirteen (52%) were left-sided. The best trajectory line to the round window was identified in all scans. The retro-facial approach was the optimal approach for 52% of cases (13/25). In all scans, the safe distance from the facial nerve were in favor of the retro-facial approach (P = 0.0011).

CONCLUSION

The OTOPLAN reconstructed imaging provided a good analysis of the retro-facial approach and helped in planning the surgical trajectory line towards the round window. Additionally, calculation of the surgical distance can help the surgeon compare the retro-facial approach to the standard facial recess for preoperative planning. These findings may help in robotic surgery.

Accessing the stapedius muscle via novel surgical retrofacial approach during cochlear implantation surgery: Intraoperative results on feasibility and safety

Human stapedius muscle (SM) can be directly and safely accessed via retrofacial approach, opening new approaches to directly measure the electrically evoked stapedius reflex threshold (eSRT). The measurement of the SM activity via direct surgical access represents a potential tool for objective eSRT fitting of cochlear implants (CI), increasing the benefit experienced by the CI users and leading to new perspectives in the development of smart implantable neurostimulators. 3D middle-ear reconstructions created after manual segmentation and related SM accessibility metrics were evaluated before the CI surgery for 16 candidates with assessed stapedius reflex. Retrofacial approach to access the SM was performed after facial recess exposure. In cases of poor exposition of SM, the access was performed anteriorly to the FN via drilling of the pyramidal eminence (PE). The total access rate of the SM via both the retrofacial and anterior approach of the FN was 100%. In 81.2% of cases (13/16), the retrofacial approach allowed to access the SM on previously categorized well exposed (8/8), partially exposed (4/5), and wholly concealed (1/3) SM with respect to FN. Following intraoperative evaluation in the remaining 18.8% (3/16), the SM was accessed anteriorly via drilling of the PE. Exposure of SM with respect to the FN and the sigmoid sinus’s prominence was a predictor for the suitable surgical approach. The retrofacial approach offers feasible and reproducible access to the SM belly, opening direct access to electromyographic sensing of the eSRT. Surgical planner tools can quantitatively assist pre-surgical assessment.

On the radiologic anatomy of pediatric sinus tympani: HRCT study

OBJECTIVE

Sinus tympani (ST) is considered the most constant among retrotympanic recesses but it is of great anatomical variability in shape and relation to mastoid portion of facial nerve. ST is difficult to access when clearing the cholesteatoma or serving as a window for cochlear implantation. The objective was to describe morphology of ST and assess feasibility of retrofacial approach in children under 5 years old.

METHODS

HRCT images of 150 children were reviewed. The type of sinus tympani was assessed according to Marchioni's classification. Width of entrance to sinus tympani (STW), depth of ST (STD), distance between the posterior semicircular canal and facial nerve (F-PSC), distance between the latter plane to the floor of ST at the right angle (P-ST) were measured. Width (HS-SS) and length (ML) of mastoid process were also measured.

RESULTS

From 300 temporal bones analyzed, the most common type of ST was type B (59.3%), followed by type C (34.3%) and type A (6.3%). The average depth of ST was 3.38±1.04 mm (1.32-8.24 mm) and mean value of F-PSC (width of retrofacial approach) was 4.91±0.75. The depth of ST (STD) presented significant deviations (ANOVA, p<0.05) among all three types. The value of ML increased with age (very high correlation).

CONCLUSION

Deep tympanic sinus (type C) is more frequent in children than in adult populations and it may suggest that pneumatization may affect the development of tympanic sinus final shape. Retrofacial approach can be used in selected pediatric patients after HRCT analysis.

Accessing the Stapedius Muscle Via Novel Surgical Retrofacial Approach: A Cadaveric Feasibility Study

HYPOTHESIS

Despite the complete embodiment of the stapedius muscle (SM) into the pyramidal eminence, it is possible to safely gain access to the SM belly via a retrofacial approach. This presents a novel approach to directly measure the electrically evoked stapedius reflex threshold (eSRT).

BACKGROUND

Objective fitting of maximum comfortable loudness levels for cochlear implant users can improve the benefit introduced by the device. Sensing SM activity via direct surgical access represents a potential tool for objective eSRT fitting.

METHODS

Eighteen human temporal bones (TBs) were used. Micro-computed tomography was performed for six TBs. Standard computed tomography for six TBs. Manual 3D-segmentation of the relevant middle and inner ear anatomy was performed on 12 TBs. Mastoidectomy and posterior tympanotomy allowed the access to middle ear of all 18 the TBs. Once identified the mastoidal segment of the facial nerve (FN), the retrofacial access to the SM was drilled.

RESULTS

The total access rate was 72.2%. Only in the first three cases the posterior semi-circular canal was hit. The SM access was identified posterior to the FN at a 4 ± 0.78 mm distance from the stapes' head, almost halfway to the chorda tympani's branching point along the FN direction. The drilling depth to access the SM posterior to the external surface of FN on average was 2 ± 0.30 mm. The exposure took on average of 5 to 8 minutes.

CONCLUSIONS

The retrofacial approach seems to offer a feasible and reproducible access to the SM belly opening an avenue to electromyographic sensing of eSRT.

A retrofacial approach of round window vibroplasty during Vibrant Soundbridge implantation for patients with congenital ear malformation

OBJECTIVE

To describe the specific retrofacial surgical approach for application of Vibrant Soundbridge (VSB) to the round window (RW) in patients with congenital ear malformation.

METHODS

Four patients with congenital ear malformation were implanted with VSB unilaterally through a retrofacial approach in present study. During the operation, the round window niche was identified through a retrofacial pathway and the floating mass transducer (FMT) was attached to the RW inferiorly.

RESULTS

Satisfied outcomes were confirmed after surgery. No intraoperative or postoperative surgical complications were observed in all patients.

CONCLUSION

When the facial nerve was aberrant or it was unable to access the RW through the classic facial recess pathway during the round window vibroplasty, the retrofacial approach could be a valid and feasible alternative approach.

The role of preoperative imaging for auditory implants in children

&lt;b&gt;Introduction:&lt;/b&gt; Preoperative imaging, besides audiological evaluation, plays a major role in evaluation of candidacy for auditory implants, and in particular cochlear implants. It is essential to assess whether the basic criteria necessary for implantation are met. Diagnostic imaging is crucial not only in determining candidacy, but also determining the feasibility of cochlear implantation as it allow to anticipate surgical difficulties which could preclude or complicate the implantation of the device. The aim of the study is to present the protocol for the evaluation of preoperative imaging studies with particular focus on the factors potentially affecting clinical decisions in children qualified for cochlear implantation. &lt;br&gt;&lt;b&gt;Material and method:&lt;/b&gt; Preoperative imaging studies of 111 children performed prior to cochlear implantation were analyzed: high-resolution computed tomography (HRCT) of temporal bones and MRI. The assessment was made according to the presented protocol. &lt;br&gt;&lt;b&gt;Results:&lt;/b&gt; Pathologies and anomalies identified during the assessment of preoperative imaging studies significantly altered clinical decisions in 30% of patients. In the study group, in 17% of patients inner ear malformations were identified. 2.7% of children were disqualified from a cochlear implantation due to severe congenital inner ear malformations. 9% of the patients have had bacterial meningitis. In 50% of them difficulties related to complete or progressive cochlear ossification occurred. In 4.5% of patients less common surgical approaches other than mastoidectomy with a posterior tympanotomy were applied. &lt;br&gt;&lt;b&gt;Discussion:&lt;/b&gt; Preoperative imaging allow for the identification of significant pathologies and anomalies affecting qualification decisions and further treatment. HRCT and MRI are complementary to each other for preoperative imaging. The two modalities in combination allow accurate and optimal evaluation of the anatomical structures prior to implantation. Inner ear malformations and cochlear ossification following meningitis are relatively frequently encountered in children qualified for a cochlear implant.

Location of the stapedius muscle with reference to the facial nerve in patients with unilateral congenital aural atresia: implication for active middle ear implants surgery

Background: Detailed investigations of the stapedial muscle (SM) in congenital aural atresia (CAA) patients have yet to be adequately conducted.Objectives: To assess image variations in the mastoid segment of the facial nerve (FN) and SM in CAA.Materials and methods: A total of nine patients comprising of 9 ears with unilateral CAA were studied. The courses of the FN and SM were evaluated from the basic point to 1 mm intervals between the mastoid portion of FN, and measured from the mean X and Y values in each group.Results: The atresia side of FN among the Y values showed significant differences compared to the contralateral side. In terms of the SM, there were no significant differences in both the X and Y values. The stapedial muscle of the CAA patients was located medially to the FN. Conversely, the distance from the PSC to the FN revealed no significant differences with regard to the X and Y values for each group.Conclusion: The current observations revealed that the SM is located more posterior to the FN in CAA patients, and this is mainly attributed to the laterally and anteriorly displaced FN.