key: cord-0695081-viqqjhfp
authors: Lee, Daniel J.; Ridge, Sarah E.; Shetty, Kunal R.
title: Heads-Up Surgery: Endoscopes and Exoscopes for Otology and Neurotology in the Era of the COVID-19 Pandemic
date: 2020-09-29
journal: Otolaryngol Clin North Am
DOI: 10.1016/j.otc.2020.09.024
sha: bc40a313f2dd59adf727b8b21c4a367927150313
doc_id: 695081
cord_uid: viqqjhfp

A new era of surgical visualization and magnification is poised to disrupt the field of otology and neurotology. The once revolutionary benefits of the binocular microscope are now shared with rigid endoscopes and exoscopes. These two modalities are complementary. The endoscope improves visualization of the hidden recesses through the external auditory canal or canal up mastoidectomy. The exoscope provides an immersive visual experience and superior ergonomics compared to binocular microscopy. Endoscopes and exoscopes are poised to disrupt the standard of care for surgical visualization and magnification in otology and neurotology.

The field of otology and neurotology requires dissection at high magnification to ensure successful management of middle ear and mastoid disease, and preservation of anatomic structures. The ideal method of visualization should provide an unobstructed wide field of view and excellent ergonomics. While the binocular microscope remains the cornerstone for surgical illumination and magnification, advances in video technology have enabled the use of heads-up techniques offered by endoscopes and exoscopes (Fig.1) . The endoscope is ideal when utilizing small surgical corridors to access the hidden recesses of the middle ear. The digital extracorporeal scope or "exoscope" is complementary to the endoscope and was designed to replace the operating microscope. The exoscope can be used for transcanal, transmastoid and craniotomy procedures requiring two-handed dissection. When compared to the microscope, these two heads-up modalities provide an immersive surgical view, greater depth of field, improved ergonomics, and enhanced compatibility with personal protective equipment (PPE).

The traditional binocular microscope greatly advanced the field of otology and neurotology by providing a stable, illuminated, magnified, and three-dimensional view of ear and skull base anatomy. The ability to perform two-handed dissection under high magnification facilitated more accurate manipulation of delicate ear structures, leading to the refinement of procedures such as the tympanoplasty and stapedectomy. 1 The surgical microscope consists of a binocular head with two adjustable eyepieces, an objective lens, and an illuminator (Fig.1) . This system is attached to a suspension arm and a J o u r n a l P r e -p r o o f stand, making the system bulky. Improvements in microscopic technology have also taken a toll on the "stack height" of the binocular head, compromising ergonomics for the user (Fig.2A) . The "stack" obstructs the view of the surgical field for OR personnel and requires a static posture with the neck flexed and arms stretched forward ( Fig.2A ). The optical system is also far from the surgical field and magnification and illumination are needed to maximize image quality.

However, field of view and depth of field decrease as magnification increases, and anatomic boundaries can obstruct light transmission. Consequently, the microscope has a shallow depth of field and narrow field of view, necessitating soft tissue and bony dissection to overcome these limitations. These constraints necessitate frequent adjustments intraoperatively. A 2015 study found that neurosurgeons used the microscope handgrip controls to change focal length, zoom or position an average of once every 114 seconds, which accounted for 8% of the total case time.

Remarkably, surgeons modified a number of behaviors in order to prevent loss of alignment and further need for microscopic readjustment, such as avoiding looking away from the oculars during hand-offs, maintaining unergonomic body postures, and even operating using a nonfocused view or at the edge of the field of view. 2

The endoscope has become an essential tool in many otolaryngologic disciplines, including rhinology. In otology and neurotology, endoscopes have advanced from an observational instrument ("otoendoscopy") to an operative one ("endoscopic ear surgery" or EES) at a growing number of centers. Although there has been a rapid increase in the adoption of EES within the last decade, 3 the endoscope continues to generate debate amongst surgeons as a primary modality for performing middle ear surgery. Interestingly, many of the arguments raised against EES J o u r n a l P r e -p r o o f match those made by rhinologists when the Hopkins rod telescope was introduced for sinus surgery. [4] [5] [6] The most common endoscope used in EES is the Hopkins rod telescope (Fig.1) . The endoscope can be used with the naked eye or coupled to a standard definition, high definition (HD), or 4K video camera. A flexible fiberoptic cable is attached to the endoscope to provide radiant energy from a halogen, xenon, or light-emitting diode (LED) light source. The system integrates with proprietary components that enable transmission of a live video feed to a monitor (mounted on a tower or surgical boom) as well as recording of imaging data for documentation. 7

This feature allows all participants to 1) share an operative view with the surgeon, improving both teaching and coordination with OR personnel and 2) allows the surgeon to sit comfortably in an ergonomic heads-up posture.

Endoscopes have a short focal length and deliver light through small openings, bypassing visual obstructions (Fig.1 ). This makes the endoscope an ideal choice for transcanal dissection, especially in patients with small or tortuous canals. Additionally, the wide-angle view, angled optics, and high contrast light source allow surgeons to "look around corners", 8 gaining visual access to hidden recesses (Fig.3) . Importantly, this reduces the need for soft tissue retraction and bony dissection. 3 Finally, mastoidectomy is an aerosol generating procedure (AGP) 9,10 and surgical aerosols can carry viral pathogens. 11 Endoscopes play an important role in risk mitigation during the era of the COVID-19 pandemic, reducing the need for mastoidectomy.

Transcanal endoscopic ear surgery (TEES) is an ideal approach for the management of cholesteatoma, as the pathology can be followed along the anatomical growth pattern from the tympanic membrane to the tympanic cavity and hidden recesses. 3 A "scope holder" is not recommended as motion parallax creates a sense of depth perception. TEES diminishes the need J o u r n a l P r e -p r o o f for a canal wall up mastoidectomy in some cases 12 and facilitates en bloc removal of cholesteatoma, with an improved chance of ossicular preservation 13 and decreased rates of residual and recurrent disease. 14 In studies comparing TEES to microscopic surgery for cholesteatoma, results have shown comparable or improved rates of control, 15 improved quality of life, decreased surgical morbidity, shorter healing time, and less postoperative pain due to avoidance of postauricular incisions. 16 TEES for tympanoplasty results in similar outcomes compared to microscopic approaches. 17,18 Endoscopic-assisted stapedectomy in some series was associated with decreased chorda tympani injury and postoperative pain along with comparable audiological outcomes and operative times. 17

In cases where a postauricular approach cannot be avoided, an endoscopic-assisted transmastoid approach can be used (Fig.4) . Transmastoid endoscopic ear surgery (TMEES) requires a smaller mastoidectomy compared to a traditional microscopic transmastoid approach.

In the treatment of extensive cholesteatoma extending to the antrum, the use of TMEES has been shown to decrease the need for a canal wall down mastoidectomy. 15 The endoscope is an invaluable tool for the management of neurotology patients.

"Underwater" endoscopic-assisted dissection can be used with a transmastoid approach for the management of superior canal dehiscence. 19 Angled endoscopes aid in the identification of subtle superior canal defects located along a downsloping tegmen following middle fossa craniotomy that otherwise escape detection when using the microscope. 20 Fully endoscopic resection of vestibular schwannomas has been reported to be a safe and effective means for hearing preservation, and requires a smaller cranial opening and less manipulation of the cerebellum and other structures. 21 Finally, the endoscope can be utilized to visualize the posterior fossa using a transmastoid craniotomy ( Disadvantages of endoscopic surgery include lack of true depth perception (some systems are now available with 4K 3D), one-handed dissection, steep learning curve, and fewer opportunities for training (especially during residency and fellowship) compared to the microscope. 8 Special consideration for safe EES include conservative use of antifog solution (shown to be ototoxic in animal models) and avoidance of thermal injury. One may prevent excess antifog solution from entering the middle ear by wiping the endoscope with saline after application. 22 Endoscopes have the potential to cause thermal damage to middle ear structures, 23 but injury can be avoided by maintaining light intensity at 50%, using suction and irrigation for rapid cooling, keeping the endoscope tip at least 8 mm away from tissues, and removing the endoscope frequently. [24] [25] [26] Exoscopes The extracorporeal video microscope or exoscope is a recent addition to the microsurgical armamentarium and was designed to replace the operative microscope. 27 Most of the initial experiences with exoscopes are documented in the neurosurgical literature. The exoscope consists of an HD or 4K video camera with optical and/or digital zoom and a fiberoptically delivered or light emitting diode (LED) light source. This system is suspended above the surgical field with a manually-actuated articulating holder or robotic arm, which transmits a twodimensional (2D) or three-dimensional (3D) image to a high resolution monitor placed at eye level directly across from the surgeon (Fig.2B) .

The exoscope has distinct advantages over the traditional binocular microscope. These include a large field of view, a longer focal length creating ample working space, and the ability to easily J o u r n a l P r e -p r o o f adjust the surgical view without anatomical constraints. 28 The microscope and the exoscope are external to the body cavity and can provide 3D visualization of the surgical field (Fig.1) .

However, the exoscope utilizes an external video monitor, which allows the surgeon to assume a heads-up posture and allows others to share the surgeon's view. 29 A 2019 systematic review found that the exoscope was equivalent or superior to the microscope in terms of image quality, magnification, lighting, focal length, and depth of field. When a 3D exoscope was used, stereopsis was also found to be equivalent or superior. The exoscope was also reported to be less expensive, more comfortable to use, more manageable and maneuverable, less obstructive of the surgical field, and better for teaching. 30 Following the initial studies which demonstrated its efficacy and safety in microneurosurgery, the exoscope has been adopted by various otolaryngologic subspecialties. 28, 31, 32 Reports have demonstrated successful use of the exoscope in cochlear implantation, mastoidectomies, vestibular schwannoma resections, temporal lobe encephaloceles, and cholesteatomas. 27, [33] [34] [35] A disadvantage with exoscopes is lack of training opportunities. With experience, however, there does not appear to be significant differences in operating time or complication rates when comparing the exoscope to the microscope. 31, 35 Other disadvantages include reduced image resolution at higher magnifications and decreased illumination in narrow surgical corridors, 27 supporting the idea that the exoscope is best suited for large surgical corridors.

In conclusion, exoscopes offer superior depth of field and ergonomics compared to microscopes at a competitive cost. Finally, a heads-up approach is compatible with full PPE (Fig.5) . Future developments will include 1) a more compact working head, 2) greater optical zoom capability, and 3) improved focused illumination.

Ergonomics is the study of work-related efficiency and safety. Surgical ergonomics include optimization of operating room layout and body mechanics to decrease musculoskeletal pain and disability. Poor ergonomics can affect cost, efficiency, performance, and patient safety. 36 Survey studies show that 47-74% of otolaryngologists report work-related musculoskeletal pain attributable to poor ergonomics. 37 Among the otolaryngology subspecialties, neck and back pain have been commonly associated with otologists or those performing otologic surgery. 38, 39 This phenomenon is likely due to frequent use of the operating microscope, which requires the surgeon to maintain a static heads-down position with the neck flexed and arms stretched forward in order to maintain a proper view through the rigid binocular eyepiece ( Fig.2A) . In fact, cervical and thoracic pain have been associated with 3 or more hours of microscope usage per week. 40 In contrast to the heads-down posture assumed during microscope use, the endoscope and exoscope utilize a video monitor placed at eye-level, directly across from the user. Such eyelevel displays are inspired by the heads-up display (HUD) system developed for military aviation, which present data on transparent displays directly in front of the pilot. 41 HUD technology and eye-level displays have been adapted for the operating room, allowing the surgeon to view the surgical field while maintaining proper natural neck joint alignment (Fig.2B) . This posture avoids stress on the cervical and thoracic spine. 40 Three-dimensional heads-up systems have been associated with a significant increase in the surgeon's rating of ergonomic comfort 42 and decrease in back and eye strain 43 and may reduce asthenopia and subsequent difficulties in concentration that can accompany prolonged microscopic ocular use.

The COVID-19 pandemic has impacted personal protective equipment (PPE) requirements and safety recommendations for medical providers globally. Enhanced protection is of particular importance for otolaryngologists, who are at increased risk of nosocomial spread when performing aerosol generating procedures (AGPs) on the upper aerodigestive tract, which has a high SARS-CoV-2 viral load in infected individuals. 44, 45 It is not yet known if the respiratory mucosa that lines the middle ear and mastoid cells also demonstrates high viral loads, but this seems likely due to its continuity with the nasopharynx and previous reports of unspecified coronavirus present in cases of otitis media. 46 Indeed, SARS-CoV-2 has been isolated from the middle ear and mastoid in a cadaveric specimens from individuals with COVID-19 47 and other respiratory viruses, including previous strains of coronavirus, have been previously identified in middle ear fluid samples. 48, 49 Suctioning, cautery, and drilling on these areas with the potential for high viral loads are therefore considered to be high risk AGPs, including mastoidectomies. 44, 9, 10 While personal respirator masks can prevent inhalation of aerosol particles, a face shield should be used to prevent ocular exposure to viral particles when performing an AGP.

Otolaryngologists are therefore recommended to wear an N95 or FFP2/3 mask in combination with a face shield, goggles, or powered air-purifying respirator (PAPR) hood when operating on high risk or COVID-19 positive patients. However, eye or face PPE often interferes with a surgeon's ability to use binocular eyepieces. 50, 51 Endoscopes and exoscopes are ideal alternatives to the microscope due to 1) full compatibility with eye covering PPE and 2) the decreased need for mastoidectomies when performing EES. 45 J o u r n a l P r e -p r o o f A barrier drape or "Ototent" has been shown to reduce both large and small particle dispersion during bony dissection with powered instrumentation (Fig.5) . 9 A recent report described the use of a draping method with a 3D exoscope during mastoidectomy. They found that the 3D image was obscured when looking through 3D glasses under a face shield, but that the image was restored when the glasses placed on the outside. 52 They reported a minimal learning curve, improved ergonomics, and similar surgical time, and recommend the use of transmastoid exoscopic and transcanal endoscopic approaches to safely perform surgery while wearing the necessary PPE.

The binocular microscope revolutionized modern surgery, transformed the field of otology and neurotology, and remains the cornerstone of otologic and neurotologic surgery. Despite its historical importance, the traditional operating microscope has several significant drawbacks when compared to the modern endoscope and exoscope. Microscopic surgery is performed using a heads-down posture that has been associated with musculoskeletal pain and disability, and the microscopic view is limited by the size and shape of small surgical corridors.

The endoscope and exoscope are ergonomically superior to the operating microscope, overcoming many of its limitations and yielding comparable or improved outcomes. The endoscope improves access through small surgical corridors, while the exoscope is best suited for large surgical corridors, making them complementary modalities. In the midst of the current COVID-19 pandemic, heads-up surgery is favorable due to compatibility with face covering PPE. The endoscope provides additional protection by reestablishing the external auditory canal as a minimal access surgical corridor, thereby avoiding aerosol generating mastoidectomies. In contrast, the foramen of Luschka and root entry zones of cranial nerves IX, X, and XI cannot be visualized microscopically using this same approach without sacrificing the posterior canal.

The history of the microscope for use in ear surgery

Analysis of disruptive events and precarious situations caused by interaction with neurosurgical microscope

Laryngoscope particle dispersion during mastoidectomy relevant to the COVID-19 era

Aerosol Dispersion During Mastoidectomy and Custom Mitigation Strategies for Otologic Surgery in the COVID-19 Era. Otolaryngol -Head Neck Surg (United States)

Surgical smoke and infection control

Principles of Pediatric Endoscopic Ear Surgery

Endoscopic exclusive transcanal approach to the tympanic cavity cholesteatoma in pediatric patients: Our experience

Comparison of endoscopic and microscopic ear surgery in pediatric patients: A meta-analysis

Outcomes in Endoscopic Ear Surgery

Can endoscopic ear surgery replace microscopic surgery in the treatment of acquired cholesteatoma? A contemporary review

Comparison of the efficacy of endoscopic tympanoplasty and microscopic tympanoplasty: A systematic review and meta-analysis

Underwater Endoscopic Repair of Superior Canal Dehiscence

Endoscopic-assisted repair of superior canal dehiscence syndrome

Endoscopic resection of vestibular schwannomas

Staying safe during endoscopic ear surgery

Thermal effects of endoscopy in a human temporal bone model: Implications for endoscopic ear surgery

Endoscopic ear surgery: A hot topic?

Thermal effects of cold light sources used in otologic surgery. Eur Arch Oto-Rhino-Laryngology

The effect of light intensity on image quality in J o u r n a l P r e -p r o o f endoscopic ear surgery

Initial Experience with 3-Dimensional Exoscope-Assisted Transmastoid and Lateral Skull Base Surgery. Otolaryngol -Head Neck Surg (United States)

A high-definition exoscope system for neurosurgery and other microsurgical disciplines: Preliminary report

Operating microscopes: Past, present, and future. Neurosurg Focus

The Exoscope in Neurosurgery: An Innovative "Point of View". A Systematic Review of the Technical, Surgical, and Educational Aspects

Initial clinical experience with a high-definition exoscope system for microneurosurgery

Using a 4K-3D Exoscope for Upper Airway Stimulation Surgery: Proof-of-Concept

Repair of a Temporal Bone Encephalocele With the Surgical Exoscope

3D exoscopic surgery of lateral skull base. Eur Arch Oto-Rhino-Laryngology

The Use of the

Exoscope in Lateral Skull Base Surgery: Advantages and Limitations

Ergonomic considerations in endoscopic sinus surgery: Lessons learned from laparoscopic surgeons

Ergonomic hazards in otolaryngology

Work-related musculoskeletal symptoms among otolaryngologists by subspecialty: A national survey

Prevalence of back and neck pain amongst ENT consultants: National survey

Occupational injury in plastic surgeons

Heads-up Vitreoretinal Surgery: Emerging Technology in Surgical Visualization

The Preliminary Experiences with Three-Dimensional Heads-Up Display Viewing System for Vitreoretinal Surgery under Various Status

Assessment of three-dimensional highdefinition visualization technology to perform microvascular anastomosis

Aerosol-generating otolaryngology procedures and the need for J o u r n a l P r e -p r o o f enhanced PPE during the COVID-19 pandemic: a literature review

Prioritizing otological surgery during the COVID-19 Pandemic

High detection rates of nucleic acids of a wide range of respiratory viruses in the nasopharynx and the middle ear of children with a history of recurrent acute otitis media

SARS-CoV-2 Virus Isolated From the Mastoid and Middle Ear

Detection of rhinovirus, respiratory syncytial virus, and coronavirus infections in acute otitis media by reverse transcriptase polymerase chain reaction

Prevalence of various respiratory viruses in the middle ear during acute otitis media

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

The challenge of performing mastoidectomy using the operating microscope with Covid-19 personal protective equipment (PPE)

Exoscope and Personal Protective Equipment Use for Otologic Surgery in the Era of COVID-19. Otolaryngol Head Neck Surg

Brief history of endoscopic transsphenoidal surgery--from Philipp Bozzini to the First World Congress of Endoscopic Skull Base Surgery. Neurosurg Focus

Suggestions for determining the mobility of the stapes by means of an endotoscope for the middle ear

Fiberoptic Endotoscopes for Examining the Middle Ear

Effective photography in otolaryngology-head and neck surgery: endoscopic photography of the middle ear. Otolaryngol -Head Neck Surg

Thirty years of endoscopic sinus surgery: What have we learned? World J Otorhinolaryngol -Head Neck Surg

Paranasal sinuses: CT imaging requirements for endoscopic surgery

Endoscopic middle meatal antrostomy: Theory, technique, and patency

Otoendoscopy: application in the middle ear surgery

Endoscopic-guided otosurgery in the prevention of residual cholesteatomas

Transtympanic endoscopy of the middle ear

Comparison of endoscopic and surgical explorations for perilymphatic fistulas

Endoscope-assisted ear surgery

Endoscopic management of acquired cholesteatoma

Endoscopic middle ear surgery

Endoscopic management of cholesteatoma: Long-term results. Otolaryngol -Head Neck Surg

Otolaryngol Neck Surg

Box 1

Rhinologist David Kennedy and Simion Zinreich (radiologist) developed CT parameters for sinus imaging and originated Functional Endoscopic Sinus Surgery (FEES) at Johns Hopkins