Assessment of jugular bulb variability based on 3D surface models: quantitative measurements and surgical implications.

PURPOSE: High-riding jugular bulbs (JBs) among other anatomical variations can limit surgical access during lateral skull base surgery or middle ear surgery and must be carefully assessed preoperatively. We reconstruct 3D surface models to evaluate recent JB classification systems and assess the variability in the JB and surrounding structures. METHODS: 3D surface models were reconstructed from 46 temporal bones from computed tomography scans. Two independent raters visually assessed the height of the JB in the 3D models. Distances between the round window and the JB dome were measured to evaluate the spacing of this area. Additional distances between landmarks on surrounding structures were measured and statistically analyzed to describe the anatomical variability between and within subjects. RESULTS: The visual classification revealed that 30% of the specimens had no JB, 63% a low JB, and 7% a high-riding JB. The measured mean distance from the round window to the jugular bulb ranges between 3.22 ± 0.97 mm and 10.34 ± 1.41 mm. The distance measurement (error rate 5%) was more accurate than the visual classification (error rate 15%). The variability of the JB was higher than for the surrounding structures. No systematic laterality was found for any structure. CONCLUSION: Qualitative analysis in 3D models can contribute to a better spatial orientation in the lateral skull base and, thereby, have important implications during planning of middle ear and lateral skull base surgery.

Novel Multiportal Approach to the Internal Auditory Canal for Hearing-Preserving Surgery: Feasibility Assessment in Dissections.

OBJECTIVE: State-of-the-art, minimally invasive endoscopic transcanal surgery of the internal auditory canal (IAC) sacrifices the cochlea with complete hearing loss. With a combination of the transcanal infracochlear and transmastoid retrolabyrinthine approaches, we aim to preserve hearing and enable minimally invasive surgical treatment of vestibular schwannoma. In this study, we investigate the anatomical indications and the feasibility of both approaches in dissections, in human whole head specimens. METHODS: We operated whole head anatomical specimens with a four-handed technique, using the retrolabyrinthine approach as the main surgical corridor and the infracochlear approach for endoscopic visualization. We tested 4 different powered surgical systems. We collected intraoperative data on the size of the access windows, the surgical freedom, and the exposed area of the IAC. Finally, we evaluated the outcome in postoperative computed tomography scans. RESULTS: Six out of 14 sides were anatomically suitable and qualified for the surgery based on preoperative computed tomography. In all attempted sides, the IAC could be reached and opened, leaving the ossicular chain and the labyrinth intact. 51%-75% of the length and 22%-40% of the circumference of the IAC could be exposed. All tested instruments were beneficial at different stages of the surgery. The four-handed technique enabled good maneuverability of the instruments. CONCLUSIONS: The combined multiportal approach to the IAC is feasible with a good surgical exposure and full anatomical preservation of hearing. State-of-the-art surgical instruments in specimens with suitable anatomy are sufficient to perform this approach.

Hearing-Preserving Approaches to the Internal Auditory Canal: Feasibility Assessment from the Perspective of an Endoscope.

OBJECTIVE: Minimally invasive transcanal transpromontorial endoscopic approaches to the internal auditory canal sacrifice the cochlea. Two hearing-preserving approaches, the exclusively endoscopic transcanal infracochlear approach and the endoscope-assisted transmastoid retrolabyrinthine approach, have been controversially discussed in the literature. In this study, we examine the feasibility of these 2 approaches by means of three-dimensional surface models, a population-based analysis of the available surgical space, and dissections in human whole-head specimens. METHODS: We reconstructed three-dimensional surface models based on clinical high-resolution computed tomography scans of 53 adult temporal bones. For both approaches, we measured the maximal extensions and the area of the surgical access windows located between landmarks on the surrounding anatomic structures. We then identified the limiting extensions and derived the cumulative distribution to describe the available surgical space. Dissections were performed to validate the corridors and landmark selection. RESULTS: The limiting extension for the infrachochlear approach is 7.0 ± 2.7 mm from the round window to the dome of the jugular bulb. The limiting extension for the retrolabyrinthine approach is 6.4 ± 1.5 mm from the dura of the posterior fossa to the facial nerve. The cumulative distribution shows that 80% of the cohort have access window extensions ≥3 mm for both approaches. CONCLUSIONS: This study shows that in a high percentage of the measured cohort, the access windows are sufficiently large for endoscopic approaches to the internal auditory canal. With appropriate instrumentation, these hearing-preserving minimally invasive approaches may evolve into alternatives to surgical treatment.

Assessment of Tumor Volume Dynamics and Outcome After Radiosurgery for the Treatment of Vestibular Schwannoma: A Single-Center Experience.

OBJECTIVE: To assess the factors affecting early local and audiometric outcomes in vestibular schwannoma (VS) patients treated with stereotactic radiosurgery (SRS). STUDY DESIGN: A retrospective review of medical records. SETTING: Tertiary referral center. PATIENTS: Records of all adult patients who underwent SRS between 2010 and 2016 for the treatment of VS were retrospectively reviewed. Patients treated with microsurgery or multi-fractionation schemes, and those who had neurofibromatosis type 2, were excluded. INTERVENTION: SRS, tumor volume/size measurements. MAIN OUTCOME MEASURES: The impact of tumor volume dynamics on the early local and hearing-related outcomes, together with the factors that influence them following SRS, and comparison of different tumor size measurement methods. RESULTS: From 2010 to 2016, 53 patients underwent single fraction SRS of 12 Gy. Median follow-up time was 32 months (range, 6-79). At the last follow-up, only one patient had clinical progression. Age less than or equal to 65 years (p = 0.04; odds ratio [OR]: 0.17; 95% confidence interval [CI]: 0.03-0.93) and baseline pure-tone average (PTA) level less than or equal to 30 dB (p = 0.03; OR: 0.90; 95% CI: 0.84-0.96) were associated with maintenance of serviceable hearing. On multivariate analysis, PTA remained significant (p = 0.01; OR: 0.04; 95% CI: 0.003-0.45). In patients with a loss of serviceable hearing, the mean volume increase tended to be higher than in the patients whose hearing was maintained. The linear measurement method underestimated, and the A × B × C/2 equation overestimated, the radiological progression compared with 3D-volumetric delineations. CONCLUSION: During the median observation period of almost 3 years, we reported our early outcome results. Tumor volume increase may have an impact on serviceable hearing loss after SRS. Currently there is no widely accepted method for the evaluation of post-SRS response. Linear measurement and the A × B × C/2 equation produce less reliable estimates of radiological progression compared with 3D-volumetric delineations. Accurate volume measurements with 3D delineations should be considered as part of clinical routine for assessing progression and deciding on salvage therapies.

Epinephrine Use in Endoscopic Ear Surgery: Quantitative Safety Assessment.

INTRODUCTION: The management of bleeding in exclusive endoscopic ear surgery (EES) is largely dependent on epinephrine use. However, to date its suitability and safety have not been assessed. The aim of the present study would be to assess the safety profile of topical application and/or local infiltrationof diluted epinephrine during EES regarding the intra- and postoperative periods. We hypothesize that epinephrine may be safely used during EES. METHODS: Retrospective analysis of 90 EES cases performed at the University Hospital of Modena, Italy. Patient's charts and video recordings of the operations were assessed. RESULTS: Epinephrine was used in all cases for hemostatic purposes as following: (1) diluted epinephrine (1:200,000) injection: mean 1.2 mL (range: 0-3.5) corresponding to 0.006 mg (range 0-0.018), and (2) topical application (1:1,000) directly in the surgical field: mean 7 cottonoids (range: 0-18) corresponding to mean 0.56 mg (range: 0-1.44). No major cardiovascular adverse effects were assessed. Only 2 intraoperative hypertensive events were recorded. One sensorineural hearing loss was observed in a case of cholesteatoma involving the stapes; no facial palsy occurred during the study period. CONCLUSION: The combined use of local injection and topical epinephrine is a safe and effective strategy to control bleeding in exclusive EES, when used within the dilutions and quantities reported in this study.

Comparison of 3- vs 2-Dimensional Endoscopy Using Eye Tracking and Assessment of Cognitive Load Among Surgeons Performing Endoscopic Ear Surgery.

IMPORTANCE: Endoscopic ear surgery (EES) is an emerging technique to treat middle ear diseases; however, the interventions are performed in 2-dimensional (2D) endoscopic views, which do not provide depth perception. Recent technical developments now allow the application of 3-dimensional (3D) endoscopy in EES. OBJECTIVE: To investigate the usability, advantages, and disadvantages of 3D vs 2D endoscopy in EES under standardized conditions. DESIGN, SETTING, AND PARTICIPANTS: This cohort study conducted at a tertiary academic medical center in Bern, Switzerland, included 16 residents and consultants of the Department of Otorhinolaryngology, Head & Neck Surgery, Inselspital, Bern. INTERVENTIONS: Each participant performed selected steps of a type I tympanoplasty and stapedotomy in 3D and 2D views in a cadaveric model using a randomized, Latin-square crossover design. MAIN OUTCOMES AND MEASURES: Time taken to perform the EES, number of attempts, and accidental damage during the dissections were compared between 3D and 2D endoscopy. Eye tracking was performed throughout the interventions. Cognitive load and subjective feedback were measured by standardized questionnaires. RESULTS: Of the 16 surgeons included in the study (11 inexperienced residents; 5 experienced consultants), 8 were women (50%); mean age was 36 years (range, 27-57 years). Assessment of surgical time revealed similar operating times for both techniques (181 seconds in 2D vs 174 seconds in 3D). A total of 64 surgical interventions were performed. Most surgeons preferred the 3D technique (10 for 3D vs 6 for 2D), even though a higher incidence of eye strain, measured on a 7-point Likert scale, was observed (3D, 2.19 points vs 2D, 1.44 points; mean difference , 0.74; 95% CI, 0.29-1.20; r = 0.67). Eye movement assessment revealed a higher duration of fixation for consultants in 2D (0.79 seconds) compared with 3D endoscopy (0.54 seconds), indicating a less-efficient application of previously acquired experiences using the new technique. Residents (mean [SD], 49.02 [16.4]) had a significantly higher workload than consultants (mean [SD], 27.21 [12.20]), independent of the used technique or task. CONCLUSIONS AND RELEVANCE: Three-dimensional endoscopy is suitable for EES, especially for inexperienced surgeons whose mental model of the intervention has yet to be consolidated. The application of 3D endoscopy in clinical routines and for educational purposes may be feasible and beneficial.

Assessment of Middle Ear Anatomy Teaching Methodologies Using Microscopy versus Endoscopy: A Randomized Comparative Study.

Teaching methodologies for the anatomy of the middle ear have not been investigated greatly due to the middle ear's highly complex structure and hidden location inside of the temporal bone. The aim of this randomized study was to quantitatively compare the suitability of using microscope- and endoscope-based methods for teaching the anatomy of the middle ear. We hypothesize that the endoscopic approach will be more efficient compared to the microscopic approach. To answer the study questions, 33 sixth-year medical students, residents and otorhinolaryngology specialists were randomized either into the endoscopy or the microscopy group. Their anatomical knowledge was assessed using a structured anatomical knowledge test before and after each session. Each participant received tutoring on a human cadaveric specimen using one of the two methods. They then performed a hands-on dissection. After 2-4 weeks, the same educational curriculum was repeated using the other technique. The mean gains in anatomical knowledge for the specialists, residents, and medical students were +19.0%, +34.6%, and +23.4%, respectively. Multivariate analyses identified a statistically significant increase in performance for the endoscopic method compared to the microscopic technique (P < 0.001). For the recall of anatomical structures during dissection, the endoscopic method outperformed the microscopic technique independently of the randomization or the prior training level of the attendees (P < 0.001). In conclusion, the endoscopic approach to middle ear anatomy education is associated to an improved gain in knowledge as compared to the microscopic approach. The participants subjectively preferred the endoscope for educational purposes.

Facial sinus endoscopic evaluation, radiologic assessment, and classification.

OBJECTIVES: To describe facial sinus anatomy from an endoscopic perspective and present a radiologic classification. METHODS: Facial sinus was studied by endoscopy and high-resolution computed tomography (HRCT) scan in 39 temporal bones that underwent exclusive transcanal endoscopic approach. A radiomorphologic classification based on the relationship between the facial sinus and the mastoid portion of the facial nerve is created as follows. In type A facial sinus, the pneumatization of the facial sinus did not extend medially or posteriorly to the mastoid portion of the facial nerve. In type B facial sinus, the pneumatization extended posteriorly to the mastoid portion of the facial nerve. In type C facial sinus, the pneumatization extended posteriorly and medially to the mastoid portion of the facial nerve. RESULTS: In all the specimens that underwent HRCT (n = 31), facial sinus could be identified, and its depth classified, in relation to the facial nerve. In this group, 58% type A, 29% type B, and 13% type C facial sinuses were identified. In all the specimens (n = 39), the facial sinus could be assessed by means of an exclusive endoscopic transcanal approach, and anatomical variants of the chordiculus, previously known as chordal ridge, could be described: ridge (39%), bridge (18%), incomplete (15%), and absent (28%). CONCLUSION: Endoscopic exploration of the retrotympanum guarantees a very good exposure of the facial sinus, allowing detailed anatomic descriptions of its conformation and relationships with other structures. Improvement in our knowledge of its anatomy might decrease the possibility of residual disease during cholesteatoma surgery. Angled endoscopes (e.g. 45 °, 70 °) can guarantee a better view of the facial sinus. LEVEL OF EVIDENCE: NA. Laryngoscope, 128:2397-2402, 2018.

Population Statistics Approach for Safety Assessment in Robotic Cochlear Implantation.

HYPOTHESIS: Descriptive statistics with respect to patient anatomy and image guidance accuracy can be used to assess the effectiveness of any system for minimally invasive cochlear implantation, on both an individual patient and wider population level. BACKGROUND: Minimally invasive cochlear implantation involves the drilling of a tunnel from the surface of the mastoid to cochlea, with the trajectory passing through the facial recess. The facial recess anatomy constrains the drilling path and places prohibitive accuracy requirements on the used system. Existing single thresholds are insufficient for assessing the effectiveness of these systems. METHODS: A statistical model of the anatomical situation encountered during minimally invasive drilling of the mastoid for cochlear implantation was developed. A literature review was performed to determine the statistical distribution of facial recess width; these values were confirmed through facial recess measurements on computed tomography (CT) data. Based on the accuracy of a robotic system developed by the authors, the effect of variation of system accuracy, precision, and tunnel diameter examined with respect to the potential treatable portion of the population. RESULTS: A facial recess diameter of 2.54 ±â€Š0.51 mm (n = 74) was determined from a review of existing literature; subsequent measurements on CT data revealed a facial recess diameter of 2.54 ±â€Š0.5 mm (n = 23). The developed model demonstrated the effects of varying accuracy on the treatable portion of the population. CONCLUSIONS: The presented model allows the assessment of the applicability of a system on a wider population scale beyond examining only the system's ability to reach an arbitrary threshold accuracy.