The present study was approved by the local institutional review board (KEK-BE 2016-00887).
1. Preparation of the Specimen
<ol>
	<li>Position a vacuum mattress on the dissection table and cover it with a sterile blanket. Lay the anatomical specimen in a surgical position on the mattress with the head slightly rotated to the contralateral side.</li>
	<li>Retract the tragus with a flexible hook to the contralateral side.</li>
	<li>Cover the specimen with a blanket sparing the external ear, just as in the operating room. 
	NOTE: Please see the Table of Materials for a complete list of equipment required.</li>
</ol>
2. Getting Started
<ol>
	<li>Adopt a comfortable standing or sitting position and adjust the endoscope screen. This is an important issue to prevent hardening of the neck muscles and therefore faster exhaustion.</li>
	<li>Perform the white balancing in your camera menu and apply a drop of anti-fog solution on the endoscope tip.</li>
	<li>Hold the surgical instruments in your dominant hand and the endoscope in the other hand.&#160;</li>
	<li>Introduce the 0&#176;, 3 mm diameter, and 15 cm length endoscope into the EAC. As a first task, clean the EAC thoroughly from eventually present ear wax using the suction tube. Rinse the EAC with water. Cut the hair inside the EAC with a pair of small scissors to prevent the endoscope from becoming dirty during every passage.</li>
	<li>Once the EAC is clean, inspect the tympanic membrane (TM). Identify: 
	-&#160;Malleus with short process, manubrium and umbo 
	-&#160;Annulus of tympanic membrane 
	-&#160;Pars flaccida (Shrappnel membrane)</li>
</ol>
3. Elevation of the Tympano-Meatal Flap (TMF)
Note: In endoscopic ear surgery, the TMF is performed slightly smaller and in a triangular shape. The reason is the limited space inside the EAC.
<ol>
	<li>Incise the EAC skin superiorly, slightly anterior to the short process of the malleus using a sickle or a round knife.</li>
	<li>Extend the incision to the posterior superior portion of the EAC and prolong the incision to the anterior and inferior border of the TM to configure a triangular shaped flap.</li>
	<li>With the 45&#176; angled round knife, expose the bone and elevate the skin until reaching the annulus. It is important to strictly adhere to the bone.</li>
	<li>Elevate the annulus with the round knife to access the tympanic cavity (TC). The mucosa of the TC is slightly more transparent than the skin and is incised at the level of the chorda tympani using a hook.</li>
	<li>Mobilize the annulus inferiorly and anteriorly using the Thomassin dissector.</li>
	<li>Identify superiorly the posterior lateral ligament of the malleus (PLML). This ligament represents the inferior limit of the Prussak space. Grasp the ligament with the Hartmann forceps and pull it gently anteriorly in the direction of the umbo until uncovering the short process of the malleus.</li>
	<li>Gently dissect the anterior Prussak space until reaching the anterior superior insertion of the annulus. Now identify: 
	-&#160;Annulus 
	-&#160;Chorda tympani 
	-&#160;Posterior malleolar ligament 
	-&#160;Lateral malleolar ligamental fold 
	-&#160;Anterior malleolar ligamental fold 
	-&#160;Prussak space</li>
</ol>
4. Detachment of the TMF from the Handle of the Malleus
<ol>
	<li>From the short process of the malleus, continue the dissection and incise the periostium of the malleolar handle towards the umbo with a needle dissector. It is important to detach the TM in the right plane to prevent accidental perforations.</li>
	<li>Detach the TM completely from the manubrium. A dry cottonoid may be helpful, since it facilitates the identification of the correct layer and its dissection.</li>
	<li>Once the umbo is reached, cut the remaining fibrous layer of the TM using a micro-scissor.</li>
	<li>Now position the whole flap on the anterior wall of the EAC to allow free access to the TC. Identify: 
	-&#160;Fibrous layer of tympanic membrane 
	-&#160;Anterior superior annulus 
	-&#160;Malleus short process, manubrium and umbo 
	-&#160;Chorda tympani anterior to the malleus</li>
</ol>
5. Middle Ear Exploration
NOTE: This part of the dissection aids in the recognition and rehearsal of the middle ear anatomy. Each subdivision of the TC should be explored separately using 0&#176; and 45&#176; endoscopes. Eventually present folds or adherences should carefully be removed.
<ol>
	<li>Epitympanum. Identify: 
	-&#160;Malleus: Neck, short process, manubrium and umbo 
	-&#160;Incus: Body, long process, lenticular process, incudostapedial joint 
	-&#160;Epitympanic diaphragm: anterior and lateral malleolar ligaments, lateral incudomalleolar ligamental fold 
	-&#160;Anterior and posterior spine 
	-&#160;Chorda tympani 
	-&#160;Tympanic isthmus and ventilation patterns to the antrum 
	-&#160;Cochleariform process 
	-&#160;Tensor tympani muscle, tendon and bony canal 
	-&#160;Tensor fold</li>
	<li>Mesotympanum. Identify: 
	-&#160;Stapes: Capitulum, anterior and posterior crus, footplate 
	-&#160;Tendon of stapedial muscle 
	-&#160;Pyramidal eminence 
	-&#160;Promontory bone 
	-&#160;Jacobson nerve with inferior tympanic artery</li>
	<li>Retrotympanum: If adherences are present they should be thoroughly removed. Changing the position of the surgeon to the contralateral side facilitates accessing the retrotympanum by angulated optics (45&#176;). Identify: 
	-&#160;Facial recess 
	-&#160;Posterior sinus 
	- Ponticulus 
	-&#160;Sinus tympani 
	-&#160;Subiculum 
	-&#160;Styloid eminence 
	-&#160;Subtympanic sinus 
	-&#160;Fustis bone 
	-&#160;Area concamerata 
	-&#160;Round window niche with tegmen, anterior and posterior pillar 
	-&#160;Round window membrane 
	-&#160;Subcochlear canaliculus 
	-&#160;Finiculus</li>
	<li>Hypotympanum 
	-&#160;Hypotympanic cells 
	-&#160;Estimate localization of the JVB if not visible</li>
	<li>Protympanum. Identify: 
	-&#160;Protiniculus 
	-&#160;Internal carotid artery 
	-&#160;Eustachian tube (ET)</li>
	<li>Disarticulate the incudostapedial joint and remove the incus. With a curette remove the scutum. Identify: 
	-&#160;Tympanic segment of the facial nerve 
	-&#160;Lateral semicircular canal 
	-&#160;Antrum 
	-&#160;COG or transverse crest 
	-&#160;Tegmen tympani</li>
	<li>Cut the tendon of the tensor tympani muscle and remove the malleus. Identify: 
	- Anterior Epitympanum 
	- Geniculate ganglion</li>
</ol>

<ol>
	<li>Presutti, L., Marchioni, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Endoscopic Ear Surgery. , (2015).</li><li>Weiss, M. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surgery+for+recurrent+and+residual+cholesteatoma.">Surgery for recurrent and residual cholesteatoma.</a> Laryngoscope. 102, 145-151 (1992).</li><li>Pickett, B. P., Cail, W. S., Lambert, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sinus+tympani:+anatomic+considerations,+computed+tomography,+and+a+discussion+of+the+retrofacial+approach+for+removal+of+disease.">Sinus tympani: anatomic considerations, computed tomography, and a discussion of the retrofacial approach for removal of disease.</a> Am J Otol. 16, 541-550 (1995).</li><li>James, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscope+or+microscope-guided+pediatric+tympanoplasty?+Comparison+of+grafting+technique+and+outcome.">Endoscope or microscope-guided pediatric tympanoplasty? Comparison of grafting technique and outcome.</a> Laryngoscope. , (2017).</li><li>Tarabichi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscopic+management+of+limited+attic+cholesteatoma.">Endoscopic management of limited attic cholesteatoma.</a> Laryngoscope. 114 (7), 1157-1162 (2004).</li><li>Bonali, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+variants+of+the+retro-+and+hypotympanum:+an+endoscopic+anatomical+study.">The variants of the retro- and hypotympanum: an endoscopic anatomical study.</a> Eur Arch Otorhinolaryngol. , (2017).</li><li>Bennett, M. L., Zhang, D., Labadie, R. F., Noble, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+Middle+Ear+Visualization+With+Endoscopy+and+Microscopy.">Comparison of Middle Ear Visualization With Endoscopy and Microscopy.</a> Otol Neurotol. 37 (4), 362-366 (2016).</li><li>Anschuetz, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Ovine+Model+for+Exclusive+Endoscopic+Ear+Surgery.">An Ovine Model for Exclusive Endoscopic Ear Surgery.</a> JAMA Otolaryngol Head Neck Surg. 143 (3), 247-252 (2017).</li><li>Wang, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+costs+and+quality+of+operative+training+for+residents+in+tympanoplasty+type+I.">The costs and quality of operative training for residents in tympanoplasty type I.</a> Acta Otolaryngol. 129, 512-514 (2009).</li><li>Dedmon, M. M., Kozin, E. D., Lee, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+Temporal+Bone+Model+for+Transcanal+Endoscopic+Ear+Surgery.">Development of a Temporal Bone Model for Transcanal Endoscopic Ear Surgery.</a> Otolaryngol Head Neck Surg. 153 (4), 613-615 (2015).</li><li>Barber, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D-printed+pediatric+endoscopic+ear+surgery+simulator+for+surgical+training.">3D-printed pediatric endoscopic ear surgery simulator for surgical training.</a> Int J Pediatr Otorhinolaryngol. 90, 113-118 (2016).</li></ol>

The authors declare no conflict of interest. LA holds a research fellowship by the Bangerter-Rhyner Foundation, Bern, Switzerland and by Karl Storz GmbH, Tuttlingen, Germany. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

The proposed dissection manual is useful for performing a complete anatomical dissection of the middle ear. Exhibiting a thorough knowledge of middle ear anatomy is a fundamental prerequisite for any middle ear surgical intervention. Cadaveric dissection allows training the handling of the camera and the surgical instruments in the EAC. For a novice in EES, the coordination between the eye and the instrument as well as the correct handling of the endoscope (no bending, maneuvering between important anatomical structures as the ossicles in a limited space and the two-dimensional image) are critical steps to get started with this emerging surgical technique. 
The main limitation of this model as compared to the real surgical situation is the lack of bleeding. This applies for any cadaveric dissection model. Recently, Dedmond et al. described a temporal bone model, where bleeding was simulated during the elevation of the TMF. This model may in fact be a good option for advanced surgeons already used to EES. In our experience, the initial familiarization with EES should be as easy as possible, since the handling of the instruments is already a challenging task. The cadaveric dissection is considered the gold standard for surgical education. However, it is subject to high costs and ethical regulations. In comparison, synthetic or animal models may overcome these issues8,11. However, in synthetic models the tactile feeling for the tissues is difficult and the resolution of 3D printing is not yet able to provide all details an anatomical specimen can. In contrast, the animal model provides excellent tissue properties but has a different anatomy. We can consider the cadaveric model the sole suitable model for anatomical teaching, whereas synthetic and animal models provide cheap alternatives for surgical training.
Compared to the microscopic technique for middle ear dissection, the endoscope allows the observation and preparation of the delicate middle ear structures through a natural orifice, the EAC. Hence, no bone has to be removed for access purposes and the middle ear can be studied in its natural state. Moreover, the endoscope allows a very close observation of any anatomical structure and thus also magnification without losing illumination. Of course, the endoscopic approach does not teach mastoidectomy, which may be performed on the same specimen after endoscopic dissection. The endoscopic technique for ear surgery is internationally spreading and therefore the need for suitable surgical training will increase.

The middle ear is located in the center of the temporal bone and bears a highly complex anatomy. The most contiguous structures are the facial nerve (FN), the cochlea (CO), the ossiculary chain (OC), the jugular vein bulb (JVB), and the internal carotid artery (ICA). The middle ear cleft is anatomically divided in five parts: the epitympanum is located superiorly, and is interconnected by the antrum to the mastoid air cell system (MACS); the retrotympanum posterior is a system of bony bridges and more or less shallow sinuses; inferiorly lies the hypotympanum; anteriorly is the protympanum with its connection to the Eustachian tube; and in the center, lies the mesotympanum1.
The physiological access through the external auditory canal (EAC) is narrow. Therefore, the standard surgical approach to the middle ear requires a retroauricular incision and the drilling of the MACS. These kinds of interventions are performed using an operating microscope. Its introduction was a milestone in otologic surgery, since it allowed the treatment of the microscopic middle ear structures. However, the microscope has a forced straight view and some areas, especially the sinus tympani, are difficult to access. This bears the risk of residual disease especially during cholesteatoma surgery2,3. Moreover, healthy tissues of the EAC, MACS, and middle ear have to be removed simply for access purposes. This not only extends the operating time, but also accounts for more surgical morbidity and a prolonged healing time4.
Recent advances led to the introduction of the endoscope as a powerful tool for ear surgery. The endoscope was first used to assist the conventionally operating surgeon to visualize the hidden areas of the middle ear. Technical and surgical refinements allowed the introduction of the endoscope as the main operating tool5. The main advantages of the endoscope are the panoramic and wide-angled views of the middle ear. For instance, the otherwise hidden retro- and hypotympanum may be accessed using an exclusive endoscopic transcanal approach without a canaloplasty6. A recent study showed superior visibility of all middle ear compartments using the endoscope when compared to the microscopic technique7. The use of angled endoscopes (30&#176; and 45&#176;) further improves visibility and allows dissection with a view of the most hidden areas of the middle ear.
However, endoscopic ear surgery (EES) is a one-handed surgical technique, as the second hand generally holds the endoscope. This issue and the narrow space inside the EAC require training to improve the surgeon&#39;s skills to safely apply the technique in patients. In general, the gold standard for surgical training is considered to be cadaveric dissection. In cases of unavailability of cadaveric specimens or local ethical issues, an animal model for the training of endoscopic ear surgery has recently been described8. Surgical training is considered an important factor in the education of trainees in a novel technique9.
Despite the importance of surgical training, a concise description of the important considerations on how to perform cadaveric dissection is still lacking in the literature. The aim of this article is to describe the methodology of exclusively endoscopic cadaveric middle ear dissection. Moreover, we aim to provide a comprehensive guide to endoscopic middle ear anatomy.

<table><tbody><tr><td>Endoscopes: 3mm diameter, 15cm length, 0&amp;deg; and 45&amp;deg;</td><td>Karl Storz</td><td></td><td></td></tr><tr><td>Otologic dissectors, round knifes, hooks, curette, microscissors (Bellucci) and microforceps (Hartmann)</td><td>Karl Storz</td><td></td><td></td></tr><tr><td>Straight and curved suction tubes</td><td>Karl Storz</td><td></td><td></td></tr><tr><td>Flexible hook</td><td></td><td></td><td></td></tr><tr><td>Scissors</td><td></td><td></td><td></td></tr><tr><td>Video Equipment&lt;br/&gt; - HD-scree&lt;br/&gt; - 3-CCD camera&lt;br/&gt; - Xenon light source</td><td>Karl Storz</td><td></td><td></td></tr><tr><td>Cadaveric Head</td><td>-</td><td></td><td></td></tr><tr><td>Vacuum matress</td><td></td><td></td><td></td></tr><tr><td>Aspirator</td><td></td><td></td><td></td></tr><tr><td>Consumables&lt;br/&gt; - Water to rinse&lt;br/&gt; - Antifog solution&lt;br/&gt; - Cotton pads&lt;br/&gt; - Cottonoid pledges&lt;br/&gt; - Gown&lt;br/&gt; - Gloves&lt;br/&gt; - Mask</td><td></td><td></td><td></td></tr></tbody></table>

discovering middle ear anatomy by transcanal endoscopic ear surgery: a dissection manual

The middle ear is located in the center of the temporal bone and bears a highly complex anatomy. The recently introduced exclusively endoscopic transcanal approach to the middle ear is a minimally invasive technique sparing the bone and mucosa of the mastoid bone, since the middle ear is accessed through the external auditory canal. This emerging method has several advantages over the traditional (microscopic) approaches to the middle ear such as the panoramic wide-angle views of the anatomy, the possibility to approach and magnify tiny structures, and the possibility of looking around the corner using angled endoscopes.
The cadaveric dissection method presented here consists of an overview on the technical requirements and a precise description of a step-by-step protocol to discover the anatomy of the middle ear. Each step and anatomical structure is carefully described in order to provide a comprehensive guide to endoscopic ear anatomy. In our opinion, this is particularly important to any novice in endoscopic ear surgery as it provides thorough anatomical knowledge and may improve surgical skills.

We dissected a total of five whole head specimens and 12 temporal bone specimens (n=22 sides) using the described instructions. The different regions of the TC were documented photographically and further analyzed. All regions were explored using 0&#176; and 45&#176; endoscopes. We conducted a complete exploration of all anatomical regions and identified all mentioned anatomical landmarks.
The anatomical structures are illustrated according to the progress of the dissection. Figure 1 illustrates the Prussak space and the malleolar ligaments, whereas Figure 2 demonstrates the anatomy after complete TMF elevation. The wide-angle view allows the visualization of the meso- and hypotympanum as well as parts of the epi-, retro-, and protympanum. In Figure 3, the superior retrotympanum is shown as it appears in a 45&#176; endoscope, while the surgeon is standing on the opposite side of the table. Figure 4 illustrates in detail the protympanum with a dehiscent ICA. After removal of the OC and transcanal atticotomy the epitympanum is inspected until the lateral semicircular canal and the antrum as shown in Figure 5.
No specimen required canaloplasty to perform complete exploration of the tympanic cavity. The identification of the anatomical structures was possible in all specimens using the 0&#176; and 45&#176; scope. However, the complete exploration of the retrotympanum, especially the facial recess and the sinus tympani, was not possible in 27% of the cases (n=6), since these bony bays were too deep to be completely explored.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56390/56390fig1.jpg" /> 
Figure 1. Left ear, 0&#176; endoscope: View of the Prussak space and the surrounding ligamental folds of the malleus. tm: tympanic membrane, an: annulus, u: umbo, sp: short process of malleus, amf: anterior malleolar fold, lmf: lateral malleolar fold, plm: posterior ligament of malleus, ct: chorda tympani, *: Prussak space <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56390/56390fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56390/56390fig2.jpg" /> 
Figure 2. Left ear, 0&#176; endoscope: View of the tympanic cavity after elevation of the tympano-meatal flap. The meso- and hypotympanum as well as parts of the epi-, retro- and protympanum are visualized. pr: promontory, jn: Jacobson nerve, hy: hypotympanum, fi: finiculus, sst: sinus subtympanicus, se: styloid eminence, pe: pyramidal eminence, st: stapedial tendon, isj: incudostapedial joint, fn: facial nerve, u: umbo, m: manubrium, sp: short process, n: neck of the malleus, ttm: tensor tympani muscle, ttf: tensor tympani fold, ica. Internal carotid artery&#160;&#160;<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56390/56390fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56390/56390fig3.jpg" /> 
Figure 3. Right ear, 45&#176; endoscope, contralateral position of the surgeon: The superior retrotympanum is illustrated using an angled endoscope. fn: facial nerve, s: stapes, st: stapedial tendon, ps: posterior sinus, fp: footplate, po: ponticulus, pe: pyramidal eminence, sit: sinus tympani, sub, subiculum, se: styloid eminence, sst: sinus subtympanicus, ap: anterior pillar, teg: tegmen, pp: posterior pillar, rw: round window, fu: fustis, tu: subcochlear tunnel &#160;<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56390/56390fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56390/56390fig4.jpg" /> 
Figure 4. Left ear, 45&#176; endoscope: Detailed view of the protympanum. Note the dehiscent carotid artery. et: Eustachian tube, ica: internal carotid artery, pro: protiniculus, co: cochlea, ttm: tensor tympani muscle &#160;<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56390/56390fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56390/56390fig5.jpg" /> 
Figure 5. Left ear, 0&#176; endoscope: After removal of the incus and malleolus and curettage of the scutum, a wide overview of the tegmen tympani and the antrum is illustrated here. Note the lateral semicircular canal and the tensor tympani muscle being in one line with the facial nerve crossing. teg: tegmen, cog: COG or transverse crest, gg: geniculate ganglion, cp: cochleariform process, ttm: tensor tympani muscle, lsc: lateral semicircular canal, fn: tympanic segment of facial nerve, s: stapes, co: cochlea, ica: internal carotid artery &#160;<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56390/56390fig5large.jpg" style="font-size: 14px;" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Discovering Middle Ear Anatomy by Transcanal Endoscopic Ear Surgery: A Dissection Manual at JoVE.com

Discovering Middle Ear Anatomy by Transcanal Endoscopic Ear Surgery: A Dissection Manual

The aim of this article is to describe the methodology of exclusively endoscopic cadaveric middle ear dissection. Moreover, we aim to provide a comprehensive guide to endoscopic middle ear anatomy.

The middle ear is located in the center of the temporal bone and bears a highly complex anatomy. The recently introduced exclusively endoscopic transcanal ...

discovering-middle-ear-anatomy-transcanal-endoscopic-ear-surgery

Nanyang Technological University

Research

JoVE Journal

Medicine

64.1K Views.  University of Bern. The aim of this article is to describe the methodology of exclusively endoscopic cadaveric middle ear dissection. Moreover, we aim to provide a comprehensive guide to endoscopic middle ear anatomy.

Video: Discovering Middle Ear Anatomy by Transcanal Endoscopic Ear Surgery: A Dissection Manual

An Endoscopic Transcanal Transpromontorial Approach for Vestibular Schwannomas using a Computer-Based Three-Dimensional Imaging System

A 2D monocular endoscope has been used in transcanal transpromontory vestibular schwannoma surgery instead of craniotomy. However, the absence of depth perception is the limitation of this approach. With the loss of depth perception, the surgeon will be not able to perform delicate and particularly complicated surgery. A binocular endoscope has been developed to provide stereoscopic vision with better depth perception for complicated anatomic structures and has been applied in some endoscopic surgeries. However, the diameter of the endoscope is a limitation in the performance of transcanal otologic surgeries. A small diameter endoscope facilitates easier surgery in a restricted space. A computer-based 3D imaging system can obtain 3D images in real-time using a small monocular endoscope. In this study, to evaluate the feasibility of a computer-based 3D imaging system for endoscopic lateral skull base surgery, we applied this 3D imaging system in a transcanal transpromontorial approach in two patients with vestibular schwannomas. The surgical procedure was completed without complication in these two cases. There was no mortality, perioperative complications, nor notable postoperative complications. Using this computer-based 3D imaging system, a better depth perception and stereoscopic vision was observed compared to a conventional 2D endoscope. The improvement in depth perception offers superior management of the complicated surgical anatomy.

Here, we present a transcanal transpromontorial approach for vestibular schwannomas using a computer-based three-dimensional (3D) imaging system combined with a two-dimensional (2D) endoscope. This system provided stereoscopic vision, better depth perception and reduced visual fatigue. This 3D imaging system enabled the application of 3D vision technology in endoscopic lateral skull base surgery.

A 2D monocular endoscope has been used in transcanal transpromontory vestibular schwannoma surgery instead of craniotomy. However, the absence of depth ...

Endaural Endoscopic Atticoantrotomy (Retrograde Mastoidectomy) using a Constant Suction Bone-drilling Technique

Endoscopic middle ear surgery is a widely employed minimally invasive surgical technique to address middle ear and mastoid pathology. Bone drilling is the main technical challenge of endoscopic middle ear surgery. The accompanying video describes the detailed protocol of a constant-suction bone-drilling technique and the procedure of endaural exclusive endoscopic atticoantrotomy (retrograde mastoidectomy) using this technique. The main components of this bone-drilling technique include a soft and flexible suction tube, which is placed into the tympanic cavity to provide constant suction, and a soft sleeve, which is wrapped around the drill shaft to prevent the high-speed rotating shaft from damaging the lens of the endoscope. With these simple modifications, the traditional otological electrodrill can be used for drilling a tiny endaural incision in endoscopic middle ear surgery. Based on this bone-drilling technique, endaural endoscopic atticoantrotomy (retrograde mastoidectomy) can be successfully established for the removal of various amounts of bone, depending on the extent of the lesion. The short-term postoperative outcome seems promising.

Endaural Endoscopic Atticoantrotomy Retrograde Mastoidectomy using a Constant Suction Bone-drilling Technique

In this paper, we present the protocol and short-term outcomes of endaural exclusive endoscopic atticoantrotomy using a constant suction bone-drilling technique.

Endoscopic middle ear surgery is a widely employed minimally invasive surgical technique to address middle ear and mastoid pathology. Bone drilling is the ...

An Integrated (Microscopic/Endoscopic) Dissection Ear Surgery Course

Traditionally, otologic surgical training consisted of microscopic cadaveric dissections. However, during the last decades the endoscope has significantly changed the surgical perspective in the otologic field. Thus, the modern ear and lateral skull base surgeon should master the entire spectrum of endoscopic and microscopic approaches, with the aim of tailoring the procedure and guaranteeing the best possible functional outcome. This work proposes a step-by-step guided and illustrated dissection course, including indications for the setup of the cadaver lab and the integration of the microscope and endoscope to enhance the use of both instruments. The alternation of the endoscope and microscope allows the novice to train the correct handling of the instruments in the surgical field under both optical views. This aspect is of utmost importance since it is not advisable to start off a technique without practicing the other one, as both are important and complementary in the modern otologic surgery setting.

An Integrated Microscopic/Endoscopic Dissection Ear Surgery Course

Traditionally, otologic surgical training consisted of microscopic cadaveric dissections. However, during the last decades the endoscope has significantly ...

The Microscopic Transcanal Approach in Stapes Surgery Revisited

The microscopic transcanal (aka transmeatal) surgical approach was first described in the 60s, offering a minimally invasive means of reaching the external auditory canal, the middle ear, and epitympanon. Such an approach avoids a retroauricular or endaural skin incision; however, working through a narrow space needs angled microsurgical instruments and specific training in otologic surgery. The transcanal approach restricts the working space; however, it offers a binocular microscopic vision into the middle ear without extended skin incisions and thus, reducing post-operative pain and bleeding. In addition, this minimally invasive approach avoids scar tissue complications, hypoesthesia of the auricle, and potential protrusion of the pinna. Despite its numerous advantages, this method is still not routinely performed by otologic surgeons. Since this minimally invasive technique is more challenging, there is a need for extensive training in order for it to be widely adopted by otologic surgeons. This article provides step-by-step surgical instructions for stapes surgery and reports possible indications, pitfalls, and limitations using this microscopic transcanal technique.

This article describes the microscopic transcanal technique for stapes surgery, providing step-by-step surgical instructions for familiarizing surgeons with this approach.

The microscopic transcanal (aka transmeatal) surgical approach was first described in the 60s, offering a minimally invasive means of reaching the ...

Step-by-Step Stapedotomy through Transcanal Exclusive Endoscopic Approach

In recent years there has been an increasing trend in the use of the endoscope to treat a variety of middle ear pathologies, including otosclerosis. Several studies comparing traditional microscopic and endoscopic stapes surgery have reported similar hearing results and an overall low rate of complications. The endoscope has unraveled its full potential in demanding settings of stapes surgery, such as unfavorable anatomy of the oval window niche or revision cases. Reduced manipulation of the chorda tympani and low rate of post-operative dysgeusia are further benefits to mention for endoscopic stapes surgery.
Being a one-handed technique, management of bleeding, positioning, and crimping of the prosthesis may be challenging for novice endoscopic surgeons, so some training in endoscopic ear surgery is recommended before performing endoscopic stapedotomy. The problem of sharing the surgical field between the endoscope and the operating instruments could be easily overcome if proper instruments positioning is understood. One-handed bleeding control in the narrow space of the ear canal may represent an issue during the elevation of the tympano-meatal flap, possibly discouraging the surgeon since the preliminary steps of surgery. Following appropriate technique to raise the flap and the collaboration with the anesthesiology team in keeping the blood pressure low guarantee an adequate bleeding control in most cases.
The aim of this article is to describe the entire surgical procedure of a transcanal exclusive endoscopic stapedotomy, from operating room set up and patient positioning to post-operative care. A step-by-step description of the surgical maneuvers with technical hints is reported, to guide the surgeon across the procedure and allow any ear surgeon to perform stapes surgery endoscopically.

The aim of this article is to provide a step-by-step method for endoscopic stapes surgery from operating room setting and patient positioning to post-operative care. This work would represent a guide for any otologic surgeon who is willing to treat otosclerosis with endoscopic transcanal technique.

In recent years there has been an increasing trend in the use of the endoscope to treat a variety of middle ear pathologies, including otosclerosis. ...

Endoscopic Cholesteatoma Surgery

Implementation of endoscopes in cholesteatoma surgery resulted in considerable changes in the management of cholesteatoma in the last two decades. Compared to the microscopic approach with an excellent but straight-line view and limited illumination, the introduction of endoscopes provides a wide-angled panoramic view. Moreover, angled lenses allow the surgeon to visualize the middle ear and its hidden recesses through a transcanal, minimally-invasive approach. The endoscope enables the surgeon to remove limited cholesteatoma of the middle ear and its recesses using an exclusive endoscopic technique by taking advantage of these benefits. This reduces the rate of residual disease and sparing external incisions and excessive temporal bone drilling as in a transmastoid approach. Since transcanal endoscopic access is mainly a one-handed technique, it implies the need for specific procedures and technical refinements. This article describes a step-by-step guide as a surgical manual for endoscopic removal of epitympanic cholesteatoma. Different techniques for cholesteatoma dissection and bone removal for epitympanectomy, including curettage and powered instruments such as drills and ultrasonic devices with their outcomes, are discussed. This may offer ear surgeons insight into technical refinements and the latest technological developments and open the horizon for different techniques.

The present protocol describes a step-by-step guide for the complete endoscopic removal of epitympanic cholesteatoma with different techniques for cholesteatoma dissection and bone removal for epitympanectomy.

Implementation of endoscopes in cholesteatoma surgery resulted in considerable changes in the management of cholesteatoma in the last two decades. ...

Endolymphatic Duct Blockage as a Surgical Treatment Option for M&#233;ni&#232;re's Disease

Endolymphatic duct blockage is a relatively new treatment option for M&#233;ni&#232;re's disease, aiming to reduce vertigo attacks while sparing hearing and equilibrium. After a regular mastoidectomy, the posterior semicircular canal is identified, and Donaldson's line is determined. This is a line through the horizontal semicircular canal, crossing the posterior semicircular canal. The endolymphatic sac is usually found at this site under the posterior semicircular canal. The bone of the endolymphatic sac and the dura are thinned until the sac is skeletonized, after which the endolymphatic duct is identified. The duct is then blocked with a titanium clip. Using a computerized tomography (CT) scan, the position is confirmed. Follow-up visits take place 1 week, 6 weeks and 1 year after surgery. To this day, only one prospective trial assessing this method has been conducted, comparing this new method to endolymphatic sac decompression. Results of the duct blockage are promising, with 96.5% of the patients free of vertigo after 2 years. However, further research is required.

Endolymphatic duct blockage is a relatively new surgical method for patients suffering from M&#233;ni&#232;re's disease. Following a regular mastoidectomy, the endolymphatic duct is identified and ligated using a regular titanium hemoclip. The effectiveness of this procedure is currently being assessed in a randomized trial.

Endolymphatic duct blockage is a relatively new treatment option for M&#233;ni&#232;re's disease, aiming to reduce vertigo attacks while sparing hearing ...

Surgical Treatment of an Endolymphatic Sac Tumor

Endolymphatic sac tumors (ELST) are low-grade papillary adenocarcinoma originating from the endolymphatic sac. Usually slow-growing, with local aggressiveness and a low risk of distant metastases, ELST can be sporadic but also frequently associated with von Hippel Lindau disease. The current treatment of ELST is primarily surgical resection. A 55-year-old woman accessed our otologic tertiary level referral center for a sudden worsening of hearing loss in her left ear and vertigo. A magnetic resonance (MRI) and computer tomography scan study subsequently showed a mass in the petrous bone; hence, the presence of an ELST was hypothesized. After embolization of the mass, the patient underwent surgical removal of the lesion. The resection of the mass was done through a translabirinthine approach, with an uneventful procedure. No residual disease remained after surgery. After 24 months of radiologic follow up with MRI, there are no signs of recurrence disease. This paper reports the management of this sporadic ELST, as well as the follow up results, providing clinicians this protocol for the handling of such a challenging otologic skull base surgery and rare disease.

Here, we discuss clinical and radiological features of endolymphatic sac tumors and report the methodology and results of a surgical removal in a case in care at our otologic referral center.

Endolymphatic sac tumors (ELST) are low-grade papillary adenocarcinoma originating from the endolymphatic sac. Usually slow-growing, with local ...

Robot-Assisted Transcanal Endoscopic Ear Surgery for Congenital Cholesteatoma

Congenital cholesteatoma accounts for 25% of cholesteatoma cases in children. Transcanal Endoscopic Ear Surgery (TEES) is ideal for these patients because it offers a wide endoscopic view of the middle ear and a minimally invasive approach. The two main limitations are the loss of one operative hand and a narrow external auditory canal in younger children. Here, we present the case of a 3-year-old patient with a Potsic stage III congenital cholesteatoma adherent to the incus and branches of the stapes. A robotic-assisted TEES procedure was performed, during which a robotic arm with 6 degrees of freedom held a 0&#176;, 2.9 mm wide endoscope, enabling the surgeon to work in a narrow environment with both hands. The procedure's duration was 2 h and 9 min, including 16 min for the installation and draping of the robotic arm. After a trans-canal approach, the cholesteatoma was dissected from the ossicles using both a needle (or sickle knife) and suction to stabilize the ossicles and limit the risk of hearing trauma. The cholesteatoma was debulked to reduce its size, allowing it to be pushed under the malleus anteriorly and then separated from other adherences before removal. A tragal cartilage graft was used to reinforce the tympanic membrane.

This protocol describes the removal of congenital cholesteatoma using minimally invasive transcanal endoscopic ear surgery with a two-handed approach and a robotic endoscope holder.

Congenital cholesteatoma accounts for 25% of cholesteatoma cases in children. Transcanal Endoscopic Ear Surgery (TEES) is ideal for these patients because ...

A Comprehensive Step-By-Step Guide for Exclusive Endoscopic Ossiculoplasty

Techniques of Endoscopic Ossiculoplasty

The utilization of endoscopes in modern otology has evolved from diagnostic purposes to the development of exclusive endoscopic ear surgery. This technique offers a panoramic view of the middle ear and provides an optimal magnification of the oval window region, the stapes' suprastructure, and the footplate, allowing great precision in prosthesis positioning during ossiculoplasty (OPL). Various techniques for ossicular chain reconstruction have been described in the literature. Either autologous or synthetic materials can be used for reconstruction. The use of a patient's own tissue minimizes the risk of implant rejection or extrusion of the prosthesis through the tympanic membrane. On the other hand, synthetic materials like titanium are light and rigid and do not require time-consuming prosthesis remodeling. The main objective of this article is to present a comprehensive step-by-step guide that serves as a surgical manual for exclusive endoscopic OPL. This guide will explain various forms of OPL using synthetic and autologous materials. The goal is to provide a comprehensive understanding of the various surgical techniques and support the integration into clinical practice.

Author Spotlight: Advancing Endoscopic Ossiculoplasty &#8211; Techniques, Innovations, and Practical Guidance for Clinical Integration

Exclusive Endoscopic ossiculoplasty (EEO) is a promising and minimally invasive approach for the treatment of conductive hearing loss due to ossicular chain disruptions and associated middle ear pathologies. Herein, step-by-step instructions and a discussion of various endoscopic ossiculoplasty techniques are presented.