Temporal bone dissection: a possible route for prion transmission?

Recent advances in Otology: Current landscape and future direction

Hearing is an essential sensation, and its deterioration leads to a significant decrease in the quality of life. Thus, great efforts have been made by otologists to preserve and recover hearing. Our knowledge regarding the field of otology has progressed with advances in technology, and otologists have sought to develop novel approaches in the field of otologic surgery to achieve higher hearing recovery or preservation rates. This requires knowledge regarding the anatomy of the temporal bone and the physiology of hearing. Basic research in the field of otology has progressed with advances in molecular biology and genetics. This review summarizes the current views and recent advances in the field of otology and otologic surgery, especially from the viewpoint of young Japanese clinician-scientists, and presents the perspectives and future directions for several topics in the field of otology. This review will aid next-generation researchers in understanding the recent advances and future challenges in the field of otology.

Droplet and Aerosol Generation With Mastoidectomy During the COVID-19 Pandemic: Assessment of Baseline Risk and Mitigation Measures With a High-performance Cascade Impactor

HYPOTHESIS

Aerosols are generated during mastoidectomy and mitigation strategies may effectively reduce aerosol spread.

BACKGROUND

An objective understanding of aerosol generation and the effectiveness of mitigation strategies can inform interventions to reduce aerosol risk from mastoidectomy and other open surgeries involving drilling.

METHODS

Cadaveric and fluorescent three-dimensional printed temporal bone models were drilled under variable conditions and mitigation methods. Aerosol production was measured with a cascade impactor set to detect particle sizes under 14.1 μm. Field contamination was determined with examination under UV light.

RESULTS

Drilling of cadaveric bones and three-dimensional models resulted in strongly positive aerosol production, measuring positive in all eight impactor stages for the cadaver trials. This occurred regardless of using coarse or cutting burs, irrigation, a handheld suction, or an additional parked suction. The only mitigation factor that led to a completely negative aerosol result in all eight stages was placing an additional microscope drape to surround the field. Bone dust was scattered in all directions from the drill, including on the microscope, the surgeon, and visually suspended in the air for all but the drape trial.

CONCLUSIONS

Aerosols are generated with drilling the mastoid. Using an additional microscope drape to cover the surgical field was an effective mitigation strategy to prevent fine aerosol dispersion while drilling.

Use of a novel drape 'tent' as an infection prevention control measure for mastoid surgery

BACKGROUND

Mastoid surgery is an aerosol-generating procedure that involves the use of a high-speed drill, which produces a mixture of water, bone, blood and tissue that may contain the viable coronavirus disease 2019 pathogen. This potentially puts the surgeon and other operating theatre personnel at risk of acquiring the severe acute respiratory syndrome coronavirus-2 from contact with droplets or aerosols. The use of an additional drape designed to limit the spread of droplets and aerosols has been described; such drapes include the 'Southampton Tent' and 'OtoTent'.

OBJECTIVES

To evaluate the use of a novel drape 'tent' that has advantages over established 'tent' designs in terms of having: (1) a CE marking; (2) no requirement for modification during assembly; and (3) no obstruction to the surgical visual field.

RESULTS AND CONCLUSION

During mastoid surgery, the dispersion of macroscopic droplets and other particulate matter was confined within the novel drape 'tent'. Use of this drape 'tent' had no adverse effects upon the surgeon's manual dexterity or efficiency, the view of the surgical field, or the sterility. Hence, our findings support its use during mastoid surgery in the coronavirus disease 2019 era.

American Neurotology Society, American Otological Society, and American Academy of Otolaryngology - Head and Neck Foundation Guide to Enhance Otologic and Neurotologic Care During the COVID-19 Pandemic

: This combined American Neurotology Society, American Otological Society, and American Academy of Otolaryngology - Head and Neck Surgery Foundation document aims to provide guidance during the coronavirus disease of 2019 (COVID-19) on 1) "priority" of care for otologic and neurotologic patients in the office and operating room, and 2) optimal utilization of personal protective equipment. Given the paucity of evidence to inform otologic and neurotologic best practices during COVID-19, the recommendations herein are based on relevant peer-reviewed articles, the Centers for Disease Control and Prevention COVID-19 guidelines, United States and international hospital policies, and expert opinion. The suggestions presented here are not meant to be definitive, and best practices will undoubtedly change with increasing knowledge and high-quality data related to COVID-19. Interpretation of this guidance document is dependent on local factors including prevalence of COVID-19 in the surgeons' local community. This is not intended to set a standard of care, and should not supersede the clinician's best judgement when managing specific clinical concerns and/or regional conditions.Access to otologic and neurotologic care during and after the COVID-19 pandemic is dependent upon adequate protection of physicians, audiologists, and ancillary support staff. Otolaryngologists and associated staff are at high risk for COVID-19 disease transmission based on close contact with mucosal surfaces of the upper aerodigestive tract during diagnostic evaluation and therapeutic procedures. While many otologic and neurotologic conditions are not imminently life threatening, they have a major impact on communication, daily functioning, and quality of life. In addition, progression of disease and delay in treatment can result in cranial nerve deficits, intracranial and life-threatening complications, and/or irreversible consequences. In this regard, many otologic and neurotologic conditions should rightfully be considered "urgent," and almost all require timely attention to permit optimal outcomes. It is reasonable to proceed with otologic and neurotologic clinic visits and operative cases based on input from expert opinion of otologic care providers, clinic/hospital administration, infection prevention and control specialists, and local and state public health leaders. Significant regional variations in COVID-19 prevalence exist; therefore, physicians working with local municipalities are best suited to make determinations on the appropriateness and timing of otologic and neurotologic care.

Demonstration and Mitigation of Aerosol and Particle Dispersion During Mastoidectomy Relevant to the COVID-19 Era

Supplemental Digital Content is available in the text

Background:

COVID-19 has become a global pandemic with a dramatic impact on healthcare systems. Concern for viral transmission necessitates the investigation of otologic procedures that use high-speed drilling instruments, including mastoidectomy, which we hypothesized to be an aerosol-generating procedure.

Methods:

Mastoidectomy with a high-speed drill was simulated using fresh-frozen cadaveric heads with fluorescein solution injected into the mastoid air cells. Specimens were drilled for 1-minute durations in test conditions with and without a microscope. A barrier drape was fashioned from a commercially available drape (the OtoTent). Dispersed particulate matter was quantified in segments of an octagonal test grid measuring 60 cm in radius.

Results:

Drilling without a microscope dispersed fluorescent particles 360 degrees, with the areas of highest density in quadrants near the surgeon and close to the surgical site. Using a microscope or varying irrigation rates did not significantly reduce particle density or percent surface area with particulate. Using the OtoTent significantly reduced particle density and percent surface area with particulate across the segments of the test grid beyond 30 cm (which marked the boundary of the OtoTent) compared with the microscope only and no microscope test conditions (Kruskall–Wallis test, p = 0.0066).

Conclusions:

Mastoidectomy with a high-speed drill is an aerosol-generating procedure, a designation that connotes the potential high risk of viral transmission and need for higher levels of personal protective equipment. A simple barrier drape significantly reduced particulate dispersion in this study and could be an effective mitigation strategy in addition to appropriate personal protective equipment.

Aerosol Dispersion During Mastoidectomy and Custom Mitigation Strategies for Otologic Surgery in the COVID-19 Era

Objective

To investigate small-particle aerosolization from mastoidectomy relevant to potential viral transmission and to test source-control mitigation strategies.

Study Design

Cadaveric simulation.

Setting

Surgical simulation laboratory.

Methods

An optical particle size spectrometer was used to quantify 1- to 10-µm aerosols 30 cm from mastoid cortex drilling. Two barrier drapes were evaluated: OtoTent1, a drape sheet affixed to the microscope; OtoTent2, a custom-structured drape that enclosed the surgical field with specialized ports.

Results

Mastoid drilling without a barrier drape, with or without an aerosol-scavenging second suction, generated large amounts of 1- to 10-µm particulate. Drilling under OtoTent1 generated a high density of particles when compared with baseline environmental levels (P < .001, U = 107). By contrast, when drilling was conducted under OtoTent2, mean particle density remained at baseline. Adding a second suction inside OtoTent1 or OtoTent2 kept particle density at baseline levels. Significant aerosols were released upon removal of OtoTent1 or OtoTent2 despite a 60-second pause before drape removal after drilling (P < .001, U = 0, n = 10, 12; P < .001, U = 2, n = 12, 12, respectively). However, particle density did not increase above baseline when a second suction and a pause before removal were both employed.

Conclusions

Mastoidectomy without a barrier, even when a second suction was added, generated substantial 1- to 10-µm aerosols. During drilling, large amounts of aerosols above baseline levels were detected with OtoTent1 but not OtoTent2. For both drapes, a second suction was an effective mitigation strategy during drilling. Last, the combination of a second suction and a pause before removal prevented aerosol escape during the removal of either drape.

Morphological validation of a novel bi-material 3D-printed model of temporal bone for middle ear surgery education

Background

A new model of 3D-printed temporal bone with an innovative distinction between soft and hard tissues is described and presented in the present study. An original method is reported to quantify the model's ability to reproduce the complex anatomy of this region.

Methods

A CT-scan of temporal bone was segmented and prepared to obtain 3D files adapted to multi-material printing technique. A final product was obtained with two different resins differentiating hard from soft tissues. The reliability of the anatomy was evaluated by comparing the original CT-scan and the pre-processed files sent to the printer in a first step, and by quantifying the printing technique in a second step. Firstly, we evaluated the segmentation and mesh correction steps by segmenting each anatomical region in the CT-scan by two different other operators without mesh corrections, and by computing distances between the obtained geometries and the pre-processed ones. Secondly, we evaluated the printing technique by comparing the printed geometry imaged using µCT with the pre-processed one.

Results

The evaluation of the segmentation and mesh correction steps revealed that the distance between both geometries was globally less that one millimeter for each anatomical region and close to zero for regions such as temporal bone, semicircular canals or facial nerve. The evaluation of the printing technique revealed mismatches of 0.045±0.424 mm for soft and -0.093±0.240 mm for hard tissues between the initial prepared geometry and the actual printed model.

Conclusions

While other reported models for temporal bone are simpler and have only been validated subjectively, we objectively demonstrated in the present study that our novel artificial bi-material temporal bone is consistent with the anatomy and thus could be considered into ENT surgical education programs. The methodology used in this study is quantitative, inspired by engineer sciences, making it the first of its kind. The validity of the manufacturing process has also been verified and could, therefore, be extended to other specialties, emphasizing the importance of cross-disciplinary collaborations concerning new technologies.

A review of simulation applications in temporal bone surgery

Background

Temporal bone surgery is a technically challenging and high-risk procedure in an anatomically complex area. Safe temporal bone surgery emphasizes a consummate anatomic understanding and technique development that requires the guidance of an experienced otologic surgeon and years of practice. Temporal bone simulation can augment otologic surgical training and enable rehearsal of surgical procedures.

Objectives

The purpose of this article is to provide an updated review of temporal bone simulation platforms and their uses.

Data Sources

PubMed literature search. Search terms included temporal bone, temporal bone simulation, virtual reality (VR), and presurgical planning and rehearsal.

Discussion

Various simulation platforms such as cadaveric bone, three-dimensional (3D) printed models, and VR simulation have been used for temporal bone surgery training. However, each simulation method has its drawbacks. There is a need to improve upon current simulation platforms to enhance surgical training and skills assessment, as well as a need to explore other clinically significant applications of simulation, such as preoperative planning and rehearsal, in otologic surgery.

Conclusions

There is no replacement for actual surgical experience, but high-fidelity temporal bone models such as those produced with 3D printing and computer simulation have emerged as promising tools in otolaryngologic surgery. Improvements in the fidelity of both 3D printed and VR simulators as well as integration of a standardized assessment format would allow for an expansion in the use of these simulation platforms in training and assessment.

Level of Evidence

5.

Direct cost comparison of totally endoscopic versus open ear surgery

OBJECTIVE

Totally endoscopic ear surgery is a relatively new method for managing chronic ear disease. This study aimed to test the null hypothesis that open and endoscopic approaches have similar direct costs for the management of attic cholesteatoma, from an Australian private hospital setting.

METHODS

A retrospective direct cost comparison of totally endoscopic ear surgery and traditional canal wall up mastoidectomy for the management of attic cholesteatoma in a private tertiary setting was undertaken. Indirect and future costs were excluded. A direct cost comparison of anaesthetic setup and resources, operative setup and resources, and surgical time was performed between the two techniques.

RESULTS

Totally endoscopic ear surgery has a mean direct cost reduction of AUD$2978.89 per operation from the hospital perspective, when compared to canal wall up mastoidectomy.

CONCLUSION

Totally endoscopic ear surgery is more cost-effective, from an Australian private hospital perspective, than canal wall up mastoidectomy for attic cholesteatoma.

An Investigation of Potential Neurosurgical Transmission of Creutzfeldt-Jakob Disease: Challenges and Lessons Learned

In 2001, New York State health officials were notified about 2 patients with Creutzfeldt-Jakob disease who had undergone neurosurgical procedures at the same hospital within 43 days of each other. One patient had Creutzfeldt-Jakob disease at the time of surgery; the other patient developed Creutzfeldt-Jakob disease 6.5 years later. This investigation highlights the difficulties in assessing possible transmission of Creutzfeldt-Jakob disease.

Integration of high-resolution data for temporal bone surgical simulations

PURPOSE

To report on the state of the art in obtaining high-resolution 3D data of the microanatomy of the temporal bone and to process that data for integration into a surgical simulator. Specifically, we report on our experience in this area and discuss the issues involved to further the field.

DATA SOURCES

Current temporal bone image acquisition and image processing established in the literature as well as in house methodological development.

REVIEW METHODS

We reviewed the current English literature for the techniques used in computer-based temporal bone simulation systems to obtain and process anatomical data for use within the simulation. Search terms included "temporal bone simulation, surgical simulation, temporal bone." Articles were chosen and reviewed that directly addressed data acquisition and processing/segmentation and enhancement with emphasis given to computer-based systems. We present the results from this review in relationship to our approach.

CONCLUSIONS

High-resolution CT imaging ([Formula: see text] voxel resolution), along with unique image processing and rendering algorithms, and structure-specific enhancement are needed for high-level training and assessment using temporal bone surgical simulators. Higher-resolution clinical scanning and automated processes that run in efficient time frames are needed before these systems can routinely support pre-surgical planning. Additionally, protocols such as that provided in this manuscript need to be disseminated to increase the number and variety of virtual temporal bones available for training and performance assessment.

Biofouling of surgical power tools during routine use

Surgical power tools (SPTs) are frequently used in many surgical specialties such as dentistry, orthopaedics, ophthalmology, neurology, and podiatry. They have complex designs that may restrict access to cleaning and sterilization agents and frequently become contaminated with microbial and tissue residues following use. Due to these challenges, surgical power tools can be considered the weak link in the decontamination cycle and present a potential for iatrogenic transmission of infection. We aimed to review the existing literature on the decontamination of surgical power tools and associated iatrogenic transmission of infection. A search of the medical literature was performed using Ovid online using the following databases: Ovid Medline 1950-2014, Embase 1980-2014, and EBM Reviews Full Text--Cochrane DSR, ACP Journal Club, and Dare. Despite challenges to decontamination processes, reported episodes of iatrogenic infection directly linked to SPTs appear rare. This may reflect a true picture but more likely represents incomplete reporting, failure to investigate power tools, or lack of surveillance linking surgical site infections (SSIs) to power tools. Healthcare professionals should be aware of the complexities associated with the decontamination of different SPTs, and should review manufacturers' reprocessing instructions prior to purchase. More clarity is required in the manufacturers' validation of these reprocessing instructions. This particularly applies to the emerging surgical robot systems that present extreme challenges to decontamination between uses. Investigation of cross-infection incidents or SSI surveillance should include an element of assessment of SPT decontamination to further elucidate the contribution of SPTs to skin and soft tissue infections.

Cadaveric temporal bone dissection: is it obsolete today?

Introduction Traditionally, surgical training in otology, is imparted by dissecting harvested human cadaveric temporal bones. However, maintenance of a cadaveric temporal bone laboratory is expensive and carries risk of exposure to infection. In recent times, other modalities of training are gaining ground and are likely to eventually replace cadaveric temporal bone dissection altogether.

Objectives Other alternative methods of training are emerging. New technology like simulation and virtual reality as high-fidelity, safer alternatives, are making rapid strides as teaching tools. Other options are the use of animal temporal bones as teaching tools. The advantages of these are compared.

Data Synthesis None of these modalities can replicate the innumerable anatomical variations which are a characteristic feature of the human temporal bone. A novice surgeon not only needs exposure to surgical anatomy and it's variations but also needs to develop hand-eye coordination skills to gain expertise.

Conclusion Deliberate practice on human cadaveric temporal bones only, will confer both mastery in anatomy and surgical technique. The human cadaveric temporal bone is ideal simulator for training in otology.

Creutzfeldt–Jakob disease and ENT

Objective:

This review addresses Creutzfeldt–Jakob disease in the context of ENT, and aims to summarise the relevant history, pathophysiology and implications for contemporary practice.

Overview:

Creutzfeldt–Jakob disease is a rare, fatal, neurodegenerative disorder. It is a prion disease with four different subtypes that can only be definitively diagnosed post-mortem. The main implications for the ENT surgeon lie in the risk of iatrogenic transmission. The three facets of assessing individual patient risk are: patient history; tissue infectivity; and procedure infectivity.

Conclusion:

This is a controversial area in medicine, and ENT in particular. This review highlights a clinically applicable approach for everyday use.

Training and simulation in otolaryngology

This article focuses on key issues surrounding the needs and application of simulation technologies for technical skills training in otolaryngology. The discussion includes an overview of key topics in training and learning, the application of these issues in simulation environments, and the subsequent applications of these simulation environments to otolaryngology. Examples of past applications are presented, with discussion of how the interplay of cultural changes in surgical training in general along with the rapid advancements in technology have shaped and influenced their adoption and adaptation. The authors conclude with emerging trends and potential influences advanced simulation and training will have on technical skills training in otolaryngology.

Assessment of Air Quality During Mastoidectomy

Objectives. The Occupational Health and Safety Administration (OSHA) outlines specific requirements governing the use of respiratory protection for workers dealing with dust or other aerosolized compounds. Health care workers may be exposed to bone dust produced during otologic procedures, creating an occupational hazard. The purpose of this research was to quantify the total suspended particulate matter (TSPM) and respirable particulate matter (PM5) created during cortical mastoidectomy and investigate whether the concentration of aerosolized dust during mastoidectomy would require the use of a particulate respirator.

Study Design. Cadaveric study to assess air quality during cortical mastoidectomy.

Setting. Temporal bone laboratory.

Methods. A simple mastoidectomy was performed on 3 cadaveric temporal bones. Suspended particulate concentration was measured using gravimetric filter methodology for TSPM and PM5. Concentration of particulate exposure was compared between mannequins positioned near the surgical field with a standard surgical mask, surgical respirator, or controls.

Results. The average total particulate matter concentration during cortical mastoidectomy was 1.89 mg/m3. The average quantity of respirable particles was below detection levels. The calculated particulate exposure concentrations for TSPM and PM5 did not exceed OSHA’s requirement for respirator use. The particulate respirator prevented exposure to bone particulates compared with controls ( P = .028).

Conclusion. The concentration of bone dust produced during cortical mastoidectomy is below regulatory guidelines for use of particulate respirators. However, experimental studies show the use of a surgical respirator may decrease particulate exposure.

Review of temporal bone dissection teaching: how it was, is and will be

Objective:

We aimed to review the history of anatomical dissection, and to examine how modern educational techniques will change the way temporal bone dissection is taught to otolaryngology trainees.

Method:

Review of the literature using Medline, Embase and PubMed database searches.

Results:

Temporal bone anatomy has traditionally been taught using cadaveric specimens. However, resources such as three-dimensional reconstructed models and ‘virtual reality’ temporal bone simulators have a place in educating the otolaryngology trainee.

Conclusion:

We should encourage the use of fresh frozen cadaveric temporal bone specimens for future otologists. Artificial three-dimensional models and virtual reality temporal bone simulators can be used to educate junior trainees, thus conserving the scarce resource of cadaveric bones.