Paralleling the introduction of endoscopes for sinus surgery more than two decades ago, otology is facing a similar paradigm shift in the use of endoscopes to perform ear surgery. The wide-angle and high-resolution image provided by endoscopes allows for improved visualization of the tympanic cavity using minimally invasive surgical portals. Incorporating endoscopic ear surgery into otologic practice is challenging. A graduated and step-wise introduction of EES to otologic surgery is recommended to ensure safe and successful implementation.
Key points
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Endoscopes allow for improved transcanal visualization of the tympanic cavity because the light source is located at the distal tip of the instrument, and angled optics offer a wide perspective of the operative field.
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For the right-handed surgeon, the authors recommend starting with left-sided transcanal endoscopic ear surgery (EES) cases because (1) the endoscope trajectory is ideal for visualizing disease in the posterosuperior mesotympanum and epitympanum, (2) the dissection instruments do not rest against the anterior canal wall, and (3) the camera hand can be rested against the patient’s shoulder and bed.
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Until greater proficiency is achieved, the surgeon should always use the dominant hand for dissection.
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Room set-up and equipment position are crucial when beginning EES. To optimize ergonomics, a surgical chair with armrests should be used, and the video tower or boom-mounted video screen should be placed directly across from the surgeon and as close to eye level as possible.
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Essential equipment for EES includes a xenon, halogen, or light-emitting diode light source, rigid endoscopes (ideally, 14 cm in length and 3 mm in diameter), a high-definition (HD) 3-chip camera, and HD video monitor.
Introduction
Otologic surgery has progressed rapidly over the past century. Before the 1920s, ear surgery was completed either with loupes or without microscopic assistance. With the refinement of the binocular operating microscope in the 1950s, otologic surgery entered its modern era. Until the 1990s, visualization of the tympanic cavity by surgeons was performed exclusively with operative microscopy (except by a handful of surgeons beginning in the 1960s), and approaches to the middle ear and mastoid were constrained by the surgeon’s line of sight. Although modern microscopes provide excellent views of the surgical field, visualization of deeper recesses of the middle ear is limited. The optical properties of a microscope require an adequate amount of light to reach the surgical plane. Accordingly, microscope-based operative approaches frequently necessitate soft tissue retraction and/or bony drilling, such as mastoidectomy, to adequately visualize and access abnormality.
In contrast to microscopes, endoscopes allow for improved visualization because the light source is located at the distal tip of the instrument, and angled optics offer a wide perspective of the operative field. The use of endoscopy to visualize the middle ear was introduced in the late 1960s; however, poor image resolution in comparison to the operative microscope limited its application ( Fig. 1 ). With the introduction of 3-chip camera systems and high-definition (HD) video systems, endoscopes now provide ultrahigh resolution images of the middle ear never previously seen. Advocates of endoscopic ear surgery (EES) espouse its wide-field view, magnification, and the ability to look around corners. Furthermore, transcanal endoscopic ear surgery (TEES) approaches transform the external auditory canal into a minimally invasive surgical portal to access middle ear (and inner ear) disease ( Fig. 2 ). It is important to emphasize that the endoscope is not meant to replace the microscope in all patients, but may serve a specialized purpose in select cases.
Initially, endoscopes were used in the ear predominately as an adjunct to microscopes for diagnostic purposes. The improved image clarity, wide-angle view, and superior illumination of endoscopes afforded visualization of the middle ear cavity through transtympanic or transmastoid approaches with relative ease. Consequently, early studies on the application of endoscopes in middle ear surgery focused on the microanatomy of the middle ear. In the 1990s, as an extension of these anatomic studies, investigators examined the application of endoscopes as observational tools in cholesteatoma procedures to evaluate for residual or recurrent disease. Recent studies from the past 10 years have demonstrated that the endoscope may be a reasonable alternative to the microscope to perform otologic surgery. Endoscopes revolutionized sinus surgery and may have a similar impact on otology for the following reasons:
- 1.
Visualization of middle ear anatomy is vastly improved with the endoscope. The wide-angle and high-resolution image provided by the endoscope allows for improved visualization of the ear during surgery. This enhanced surgical view invites a more robust understanding of all middle ear structures and their spatial relationships.
- 2.
The endoscope expands the surgical reach of a transcanal approach to access complex middle disease. EES transforms the external auditory canal into a minimally invasive portal for middle ear surgery (and inner ear surgery in selected cases).
Drawbacks of EES include a more challenging one-handed dissection and limited instrumentation. Modification of operative techniques and new instrumentation are needed to lower the barrier of adoption of EES.
In this review, the following are summarized: (1) surgical indications for EES, (2) proper surgical ergonomics, (3) necessary EES instrumentation, and (4) pearls and pitfalls associated with incorporating EES into your clinical practice.
Introduction
Otologic surgery has progressed rapidly over the past century. Before the 1920s, ear surgery was completed either with loupes or without microscopic assistance. With the refinement of the binocular operating microscope in the 1950s, otologic surgery entered its modern era. Until the 1990s, visualization of the tympanic cavity by surgeons was performed exclusively with operative microscopy (except by a handful of surgeons beginning in the 1960s), and approaches to the middle ear and mastoid were constrained by the surgeon’s line of sight. Although modern microscopes provide excellent views of the surgical field, visualization of deeper recesses of the middle ear is limited. The optical properties of a microscope require an adequate amount of light to reach the surgical plane. Accordingly, microscope-based operative approaches frequently necessitate soft tissue retraction and/or bony drilling, such as mastoidectomy, to adequately visualize and access abnormality.
In contrast to microscopes, endoscopes allow for improved visualization because the light source is located at the distal tip of the instrument, and angled optics offer a wide perspective of the operative field. The use of endoscopy to visualize the middle ear was introduced in the late 1960s; however, poor image resolution in comparison to the operative microscope limited its application ( Fig. 1 ). With the introduction of 3-chip camera systems and high-definition (HD) video systems, endoscopes now provide ultrahigh resolution images of the middle ear never previously seen. Advocates of endoscopic ear surgery (EES) espouse its wide-field view, magnification, and the ability to look around corners. Furthermore, transcanal endoscopic ear surgery (TEES) approaches transform the external auditory canal into a minimally invasive surgical portal to access middle ear (and inner ear) disease ( Fig. 2 ). It is important to emphasize that the endoscope is not meant to replace the microscope in all patients, but may serve a specialized purpose in select cases.
Initially, endoscopes were used in the ear predominately as an adjunct to microscopes for diagnostic purposes. The improved image clarity, wide-angle view, and superior illumination of endoscopes afforded visualization of the middle ear cavity through transtympanic or transmastoid approaches with relative ease. Consequently, early studies on the application of endoscopes in middle ear surgery focused on the microanatomy of the middle ear. In the 1990s, as an extension of these anatomic studies, investigators examined the application of endoscopes as observational tools in cholesteatoma procedures to evaluate for residual or recurrent disease. Recent studies from the past 10 years have demonstrated that the endoscope may be a reasonable alternative to the microscope to perform otologic surgery. Endoscopes revolutionized sinus surgery and may have a similar impact on otology for the following reasons:
- 1.
Visualization of middle ear anatomy is vastly improved with the endoscope. The wide-angle and high-resolution image provided by the endoscope allows for improved visualization of the ear during surgery. This enhanced surgical view invites a more robust understanding of all middle ear structures and their spatial relationships.
- 2.
The endoscope expands the surgical reach of a transcanal approach to access complex middle disease. EES transforms the external auditory canal into a minimally invasive portal for middle ear surgery (and inner ear surgery in selected cases).
Drawbacks of EES include a more challenging one-handed dissection and limited instrumentation. Modification of operative techniques and new instrumentation are needed to lower the barrier of adoption of EES.
In this review, the following are summarized: (1) surgical indications for EES, (2) proper surgical ergonomics, (3) necessary EES instrumentation, and (4) pearls and pitfalls associated with incorporating EES into your clinical practice.
Indications for endoscopic ear surgery
The application of the endoscope to perform otologic surgery is currently debated, and indications are being refined ( Table 1 ). Over the past decade, a handful of surgeons (mostly outside the United States) has used the endoscope as an instrument not only for observation but also as the sole instrument for visualization of the middle ear during operative dissection, similarly to the way paranasal sinus surgery is currently performed. Widespread acceptance of EES will rely on rigorous and prospective clinical outcomes, as well as standardization of surgical approaches, instrumentation, and nomenclature. At the Massachusetts Eye and Ear Infirmary (MEEI), a system to classify the use of endoscopy during otologic surgery (class 0–3; 0, no endoscope; 3, TEES) is being developed. The classification system and subsequent modifications are examples of how to standardize operative descriptions and analyze clinical outcomes across large cohorts of patients and multiple institutions ( Table 2 ).
| Endoscope | Microscope | |
|---|---|---|
| Number of hands Available for dissection | One-handed | Two-handed |
| Typical surgical approach | Transcanal (can be postauricular for combined cases as well as via the antrum following canal up mastoidectomy) | Transcanal with speculum ± endaural incision or postauricular |
| Resolution | High | High |
| Binocular vision | No | Yes |
| Field of view | Wide | Narrow |
| Ability to look around corners | Yes (0–70°) | No |
| Portal needed for visualization | Narrow | Wide |
| Description | TEES Vs. Non-TEES | |
|---|---|---|
| Class 0 | Operative microscope alone | Non-TEES |
| Class 1 | Endoscope used for inspection/observation only; no dissection | |
| Class 2a | Mixed microscopic/endoscopic dissection; minority of dissection with endoscope | |
| Class 2b | Mixed microscopic/endoscopic dissection; majority of dissection with endoscope | |
| Class 2m | Endoscope-only case transitioned to microscopic case requiring mastoidectomy | |
| Class 3 | Endoscope only (no operative microscope) | TEES |
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