This research has been conducted in accordance with ethical principles, including the World Medical Association Declaration of Helsinki (2002) and the institutional human research ethics committee&#39;s guidelines (Comitato Etico dell&#39;Area Vasta Emilia Nord). The local ethical committee does not perform a formal ethical assessment for case reports.
1. Preparation of the patient
<ol>
	<li>After oro-tracheal intubation and general anesthesia, position the patient supine with the head tilted toward the opposite side of the affected ear, and the chin slightly hyperextended. Pull down the same-side shoulder as much as possible, to create a wide angle between the head and the shoulder allowing easier access to the ear.</li>
	<li>Using a 5 mL syringe with G25 0.50 x 42 mm needle, inject around 1-2 mL of local anesthetic diluted with a vasoconstrictor agent (e.g., 2% mepivacaine and epinephrine 1:200,000) in the four main points of the EAC skin (posterior wall, superior and inferior angle, retrotragal region).</li>
</ol>
2. Preparation of the sterile surgical site
<ol>
	<li>Use an iodopovidone-soaked gauze to sterilize the whole external ear, to create an aseptic field.</li>
	<li>Ensure that iodopovidone enters the EAC and reaches the tympanic membrane.</li>
</ol>
3. Preparation of the operating room and surgical instruments
<ol>
	<li>Place the endoscopic tower or a high-resolution monitor when available, in front of the surgeon, at his/her eye level, at adequate distance to keep a comfortable position of the head and neck during the surgery.</li>
	<li>Connect a 3 mm diameter, 14&#160;cm length, 0&#176; rigid endoscope to the high-definition digital camera and xenon light source. Keep the light source at 50% intensity to prevent heat damage to the inner ear.</li>
	<li>Perform white balance by pushing the central button on the camera head and adjust the focus by turning its gray wheel before starting the surgery.</li>
	<li>Prepare a quality de-misting (anti-fog) solution to clean the endoscope tip. Dip a cotton pad in this solution and place it close to the external ear. 
	&#8203;NOTE: The standard otological instruments set for stapes surgery is prepared on the instrument table, as shown in Figure 1.</li>
</ol>
4. Surgical steps
NOTE: Hold the endoscope with the non-dominant hand, leaning it against the posterior wall of the EAC, and the surgical instruments with the dominant one. Surgical instruments, if any, should be introduced in the EAC before the endoscope and moved toward the middle ear under endoscopic vision, to prevent accidental damage to the external and middle ear structures. It is advisable to keep any working instrument above the endoscope and stabilize its movement keeping the fourth and fifth fingers on the patient&#39;s head (Figure 2).
<ol>
	<li>Under direct endoscopic vision, perform anesthesia by slowly injecting another 1-2 mL of local anesthetic diluted with a vasoconstrictor agent (e.g., 2% mepivacaine and epinephrine 1:200,000) in the subperiosteal plane of the posterior wall of the EAC.</li>
	<li>Use scissors to cut hair of the most lateral part of the EAC, to avoid contaminating the tip of the endoscope at each in and out passage of the canal.</li>
	<li>Use the monopolar (molecular resonance hook) with 15 W power to delineate the tympano-meatal flap (TMF) incision from 5 to 12 o&#39;clock, about 8 to 10 mm far from the annulus (modified Rosen incision).</li>
	<li>Use the round knife to perform the actual skin incision following the previously marked line and raise the TMF with the help of epinephrine-soaked cottonoids.</li>
	<li>Once the annulus is identified as a white thickening of the tympanic membrane, continue the dissection under it. Detach the pars flaccida from the short process of the malleus with Hartmann forceps, keeping the pars tensa adherent to the umbus. 
	NOTE: During this step, identify the chorda tympani as a whitish string emerging from the chordal eminence, and leave it untouched.</li>
	<li>Remove the posterior wall of the EAC and the scutum through the curette to achieve a good exposure of the oval window region. In some cases, even if the oval window region is fully exposed, some curettage is necessary to create a favorable working area on the stapes. Displace the chorda tympani medially with a hook to further expose the footplate. 
	NOTE: Take some time to inspect the middle ear anatomy to check the important anatomical landmarks, such as the facial nerve, which could be dehiscent and/or prolapsed onto the footplate, as in the present case.</li>
	<li>Check the ossicular chain by gently pushing the stapes and the malleus with a hook, and confirm stapes fixation.</li>
	<li>Use the microdrill with a 0.6 mm diamond burr to perform posterior crurotomy. Then, create a hole in the mid or posterior portion of the footplate.</li>
	<li>Cut the stapedial tendon with Bellucci scissors. Then, disarticulate the incus from the stapes with the help of a hook and remove the stapes superstructure. 
	NOTE: Avoid using suction on the hole to prevent perilymphatic fluid removal and minimize post-operative vertigo or inner ear damage.</li>
	<li>Use the Fisch hook to regularize the footplate hole and check its adequate calibration, as well as to remove possible small bone fragments from the vestibule.</li>
	<li>Insert the stapes prosthesis (0.6 mm x 4.75 mm - total length 5.75 mm platinum/polytetrafluoroethylene prosthesis) into the EAC using the suction tube.</li>
	<li>Gently position it into the footplate hole with the hook. Crimp the prosthesis hook after anchoring it to the long process of the incus.</li>
	<li>Check the proper movement of the prosthesis, by gently pushing on the handle of the malleus.</li>
	<li>Replace the TMF and pack the EAC with resorbable hemostatic pledgets.</li>
</ol>
5. Ear dressing
<ol>
	<li>Cover the auricle with an adhesive plaster. No compression is needed.</li>
</ol>
6. Post operative care
<ol>
	<li>Allow the patient to drink, eat, and stand up at least 8 h post-operatively, if no nausea or vomiting occurred.</li>
	<li>The following day assess the facial nerve function, using the House-Brackman scale14 and the presence of spontaneous nystagmus with Frenzel googgles. Perform bone conduction pure tone audiometry to exclude sensorineural HL15. 
	NOTE: A two week-follow up visit is planned to remove residual pledgets of hemostatic material and check the healing process. Complete audiometric evaluation and otoendoscopy are usually performed between 1 to 2 months post-operatively.</li>
</ol>

<ol>
	<li>Manna, S., Kaul, V. F., Gray, M. L., Wanna, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscopic+versus+microscopic+middle+ear+surgery:+A+meta-analysis+of+outcomes+following+tympanoplasty+and+stapes+surgery.">Endoscopic versus microscopic middle ear surgery: A meta-analysis of outcomes following tympanoplasty and stapes surgery.</a> Otology &amp; Neurotology. 40 (8), 983-993 (2019).</li><li>Das, A., Mitra, S., Ghosh, D., Sengupta, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscopic+stapedotomy:+Overcoming+limitations+of+operating+microscope.">Endoscopic stapedotomy: Overcoming limitations of operating microscope.</a> Ear, Nose &amp; Throat Journal. 100 (2), 103-109 (2021).</li><li>Marchioni, D., 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=Complications+in+endoscopic+ear+surgery.">Complications in endoscopic ear surgery.</a> Otology &amp; Neurotology. 39 (8), 1012-1017 (2018).</li><li>Lucidi, D., 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=Disease-specific+quality+of+life+and+psychological+distress+after+endoscopic+tympanoplasty.">Disease-specific quality of life and psychological distress after endoscopic tympanoplasty.</a> European Archives of Oto-Rhino-Laryngology. 279 (1), 191-198 (2021).</li><li>Lucidi, D., 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=Does+microscopic+experience+influence+learning+curve+in+endoscopic+ear+surgery?+A+multicentric+study.">Does microscopic experience influence learning curve in endoscopic ear surgery? A multicentric study.</a> Auris, Nasus, Larynx. 48 (1), 50-56 (2020).</li><li>Kozin, E. D., 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=Systematic+review+of+outcomes+following+observational+and+operative+endoscopic+middle+ear+surgery.">Systematic review of outcomes following observational and operative endoscopic middle ear surgery.</a> The Laryngoscope. 125 (5), 1205-1214 (2015).</li><li>Lucidi, D., Molinari, G., Reale, M., Alicandri-Ciufelli, M., Presutti, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+results+and+learning+curve+of+endoscopic+stapes+surgery:+A+10-year+experience.">Functional results and learning curve of endoscopic stapes surgery: A 10-year experience.</a> The Laryngoscope. 131 (4), 885-891 (2020).</li><li>Fang, L., Xu, J., Wang, W., Huang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Would+endoscopic+surgery+be+the+gold+standard+for+stapes+surgery+in+the+future?+A+systematic+review+and+meta-analysis.">Would endoscopic surgery be the gold standard for stapes surgery in the future? A systematic review and meta-analysis.</a> European Archives of Oto-Rhino-Laryngology. 278 (4), 925-932 (2021).</li><li>Fernandez, I. J., 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+role+of+endoscopic+stapes+surgery+in+difficult+oval+window+niche+anatomy.">The role of endoscopic stapes surgery in difficult oval window niche anatomy.</a> European Archives of Oto-Rhino-Laryngology. 276 (7), 1897-1905 (2019).</li><li>Fernandez, I. J., Villari, D., Botti, C., Presutti, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscopic+revision+stapes+surgery:+surgical+findings+and+outcomes.">Endoscopic revision stapes surgery: surgical findings and outcomes.</a> European Archives of Oto-Rhino-Laryngology. 276 (3), 703-710 (2019).</li><li>Molinari, G., 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=Taste+impairment+after+endoscopic+stapes+surgery:+do+anatomic+variability+of+chorda+tympani+and+surgical+technique+matter.">Taste impairment after endoscopic stapes surgery: do anatomic variability of chorda tympani and surgical technique matter.</a> European Archives of Oto-Rhino-Laryngology. , (2021).</li><li>Alicandri-Ciufelli, 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=Rating+surgical+field+quality+in+endoscopic+ear+surgery:+proposal+and+validation+of+the+Modena+Bleeding+Score.">Rating surgical field quality in endoscopic ear surgery: proposal and validation of the Modena Bleeding Score.</a> European Archives of Oto-Rhino-Laryngology. 276 (2), 383-388 (2019).</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=Management+of+bleeding+in+exclusive+endoscopic+ear+surgery:+Pilot+clinical+experience.">Management of bleeding in exclusive endoscopic ear surgery: Pilot clinical experience.</a> Otolaryngology - Head and Neck Surgery. 157 (4), 700-706 (2017).</li><li>House, J. W., Brackmann, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facial+nerve+grading+system.">Facial nerve grading system.</a> Otolaryngology - Head and Neck Surgery. 93 (2), 146-147 (1985).</li><li>Marchioni, D., 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=Complications+in+endoscopic+ear+surgery.">Complications in endoscopic ear surgery.</a> Otology &amp; Neurotology. 39 (8), 1012-1017 (2018).</li><li>Campbell, K. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+basic+audiologic+assessment.">The basic audiologic assessment.</a> Essential Audiology for Physicians. , (1998).</li><li>Alicandri-Ciufelli, 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=Epinephrine+use+in+endoscopic+ear+surgery:+Quantitative+safety+assessment.">Epinephrine use in endoscopic ear surgery: Quantitative safety assessment.</a> ORL. 82 (1), 1-7 (2020).</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=Discovering+middle+ear+anatomy+by+transcanal+endoscopic+ear+surgery:+A+dissection+manual.">Discovering middle ear anatomy by transcanal endoscopic ear surgery: A dissection manual.</a> Journal of Visualized Experiments: JoVE. (131), e56390 (2018).</li><li>Altamami, N. 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=Is+one+of+these+two+techniques:+CO2+laser+versus+microdrill+assisted+stapedotomy+results+in+better+post-operative+hearing+outcome.">Is one of these two techniques: CO2 laser versus microdrill assisted stapedotomy results in better post-operative hearing outcome.</a> European Archives of Oto-Rhino-Laryngology. 276 (7), 1907-1913 (2019).</li><li>Alicandri-Ciufelli, 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=Acquisition+of+surgical+skills+for+endoscopic+ear+and+lateral+skull+base+surgery:+A+staged+training+programme.">Acquisition of surgical skills for endoscopic ear and lateral skull base surgery: A staged training programme.</a> Acta Otorhinolaryngologica Italica. 38 (2), 151-159 (2018).</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 Otolaryngology - Head &amp; Neck Surgery. 143 (3), 247-252 (2017).</li></ol>

All the authors declare no conflicts of interest.

A protocol for totally EStS is herein proposed, to guide any otologic surgeon in performing stapes surgery endoscopically.
The first surgical step (elevation of the TMF) could be the bloodiest phase of the whole procedure, and it represents a challenge for the surgeon in relation to one-hand bleeding control13. Moreover, in otosclerosis cases, the tympanic membrane is intact; so maximal care should be paid not to damage it. As reported in our protocol, some technical hi...

The use of the endoscope in ear surgery has gradually increased since its first application in the 1990s, to treat a variety of middle ear pathologies, including otosclerosis1. As compared to the microscope, the endoscope guarantees a wide field of exposure, high magnification and resolution images, reduced bone removal and a significantly improved quality of life after surgery2,3,4.
The use of one hand has been mentioned as a limitation of the endoscopic technique, especially in functional procedures such as the stapes surgery5,6. However, a growing number of papers have shown that endoscopic stapes surgery (EStS) is feasible, safe, and has favorable outcomes, similar to the traditional stapedotomy7,8. Moreover, the endoscope has unraveled its full potential especially in patients with unfavorable anatomy or in revision cases, representing a valuable tool to support the surgeon in these demanding settings9,10. Limited manipulation of the chorda tympani and low rate of post-operative dysgeusia are further benefits of this technique11.
EStS could be challenging for surgeons who do not have much experience in the use of the endoscope. The problem of sharing the surgical field between the endoscope and the operating instruments could be easily overcome if proper instruments handling is understood. One-handed bleeding control in the narrow space of the external auditory canal (EAC) and the tympanic cavity could be frustrating for a novice surgeon12,13. Moreover, it is important to properly position the patient and set up the operating room in order to guarantee a comfortable setting for the surgeon across the entire operation.
The aim of this article is to show the 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 procedure is reported, to allow any ear surgeon to understand and possibly reproduce such intervention.
We report the case of a 56-year-old female who underwent right transcanal EStS for bilateral otosclerosis. The patient reported slowly progressing and bilateral hearing loss (HL), without vertigo or tinnitus. While the right otoscopy was normal, the audiometric test demonstrated a right moderate mixed HL, with a mean preoperative bone conduction-pure tone average (BC-PTA) of 24&#160;dB, a mean preoperative air-conduction pure tone average (AC-PTA) of 71 dB, and a mean preoperative air-bone gap (ABG) of 47&#160;dB. The tympanogram was bilateral type A and stapedial reflexes were absent. No CT scan was deemed necessary as preoperative assessment.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antifog solution</td>
			<td>GOLFF</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Aspirator system (40L/min power)</td>
			<td>EXTRUDAN SURGERY APS</td>
			<td></td>
			<td>4m long, dimeter ch25</td>
		</tr>
		<tr>
			<td>Cold light source with cable</td>
			<td>STORZ</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Consumables: 
			- Iodopovidone solution 
			- Epinephrine 
			- Sterile water to rinse 
			- Spongostan (adsorbable hemostatic sponge)</td>
			<td>ETHICON INC.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cotton pads</td>
			<td>FARMAC ZABBAN</td>
			<td></td>
			<td>10x10cm</td>
		</tr>
		<tr>
			<td>Cottonoid pledgets</td>
			<td>CODMAN</td>
			<td></td>
			<td>10 surgical patties</td>
		</tr>
		<tr>
			<td>Endoscope</td>
			<td>STORZ</td>
			<td></td>
			<td>3mm diameter, 15cm length, 0&#176;</td>
		</tr>
		<tr>
			<td>Local anesthetic with vasoconstrictor in sterile and non-sterile syringe</td>
			<td>GALENICA SENESE</td>
			<td></td>
			<td>10 vials x 5ml</td>
		</tr>
		<tr>
			<td>Otologic set instruments</td>
			<td>STORZ</td>
			<td></td>
			<td>round knife, hook, curette, Bellucci scissors and Hartmann forceps, suction tubes</td>
		</tr>
		<tr>
			<td>Skeeter Drill</td>
			<td>MEDTRONIC</td>
			<td></td>
			<td>0.6 mm diamond burr</td>
		</tr>
		<tr>
			<td>Stapes prosthesis</td>
			<td>SPIGGLE &#38; THEIS</td>
			<td></td>
			<td>0.6x4.75mm</td>
		</tr>
		<tr>
			<td>Surgical scrub set for otologic patients</td>
			<td>EURONDA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical scrub set for operating surgeon</td>
			<td>EURONDA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical scrub set for nurse</td>
			<td>EURONDA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vesalius molecular resonance electrosurgical unit</td>
			<td>TELEA ELECTRONIC ENGINEERING</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Video equipment: 4K Camera 
			- HD screen 
			- Video processor (Image 1S system)</td>
			<td>STORZ</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

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 patient had a normal post-operative course, without facial palsy or vertigo. The 6-month post-operative hearing test16&#160;is shown in Figure 3. The otoendoscopy showed regular healing of the tympanic membrane. The patient denied any taste impairment.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63061/63061fig01.jpg" /> 
Figure 1: Standard otologi...

Watch this Scientific Journal Video about Step-by-Step Stapedotomy through Transcanal Exclusive Endoscopic Approach at JoVE.com

Step-by-Step Stapedotomy through Transcanal Exclusive Endoscopic Approach

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. ...

step-step-stapedotomy-through-transcanal-exclusive-endoscopic

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JoVE Journal

Medicine

5.1K Views.  University Hospital of Modena. 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.

Video: Step-by-Step Stapedotomy through Transcanal Exclusive Endoscopic Approach

How to Measure Cortical Folding from MR Images: a Step-by-Step Tutorial to Compute Local Gyrification Index

Cortical folding (gyrification) is determined during the first months of life, so that adverse events occurring during this period leave traces that will be identifiable at any age. As recently reviewed by Mangin and colleagues2, several methods exist to quantify different characteristics of gyrification. For instance, sulcal morphometry can be used to measure shape descriptors such as the depth, length or indices of inter-hemispheric asymmetry3. These geometrical properties have the advantage of being easy to interpret. However, sulcal morphometry tightly relies on the accurate identification of a given set of sulci and hence provides a fragmented description of gyrification. A more fine-grained quantification of gyrification can be achieved with curvature-based measurements, where smoothed absolute mean curvature is typically computed at thousands of points over the cortical surface4. The curvature is however not straightforward to comprehend, as it remains unclear if there is any direct relationship between the curvedness and a biologically meaningful correlate such as cortical volume or surface. To address the diverse issues raised by the measurement of cortical folding, we previously developed an algorithm to quantify local gyrification with an exquisite spatial resolution and of simple interpretation. Our method is inspired of the Gyrification Index5, a method originally used in comparative neuroanatomy to evaluate the cortical folding differences across species. In our implementation, which we name local Gyrification Index (lGI1), we measure the amount of cortex buried within the sulcal folds as compared with the amount of visible cortex in circular regions of interest. Given that the cortex grows primarily through radial expansion6, our method was specifically designed to identify early defects of cortical development.
In this article, we detail the computation of local Gyrification Index, which is now freely distributed as a part of the FreeSurfer Software (<a href="http://surfer.nmr.mgh.harvard.edu/">http://surfer.nmr.mgh.harvard.edu/</a>, Martinos Center for Biomedical Imaging, Massachusetts General Hospital). FreeSurfer provides a set of automated reconstruction tools of the brain's cortical surface from structural MRI data. The cortical surface extracted in the native space of the images with sub-millimeter accuracy is then further used for the creation of an outer surface, which will serve as a basis for the lGI calculation. A circular region of interest is then delineated on the outer surface, and its corresponding region of interest on the cortical surface is identified using a matching algorithm as described in our validation study1. This process is repeatedly iterated with largely overlapping regions of interest, resulting in cortical maps of gyrification for subsequent statistical comparisons (Fig. 1). Of note, another measurement of local gyrification with a similar inspiration was proposed by Toro and colleagues7, where the folding index at each point is computed as the ratio of the cortical area contained in a sphere divided by the area of a disc with the same radius. The two implementations differ in that the one by Toro et al. is based on Euclidian distances and thus considers discontinuous patches of cortical area, whereas ours uses a strict geodesic algorithm and include only the continuous patch of cortical area opening at the brain surface in a circular region of interest.

Measuring gyrification (cortical folding) at any age represents a window into early brain development. Hence, we previously developed an algorithm to measure local gyrification at thousands of points over the hemisphere1. In this paper, we detail the computation of this local gyrification index.

Cortical folding (gyrification) is determined during the first months of life, so that adverse events occurring during this period leave traces that will ...

Step By Step: Microsurgical training method combining two nonliving animal models

The learning of microsurgical techniques and the maintenance of microsurgical skills have been traditionally based on the use of living animals, mainly laboratory rats. This method although extremely valuable can be economically demanding both for the surgeon and the sponsoring institution; it also requires special training facilities that may not always be available or accessible. Furthermore ethical concerns can limit the use of living animals for training purposes. Alternative training methods, such as inert tubes and gloves have not gained popularity among surgeons since they do not offer an experience similar to that of a clinical situation. Non-living animal models include the use of chicken thighs and wings; they offer a practice experience that resembles a clinical situation to a considerable extent. This type of training is relatively cheap and easily available. The microscope and instruments required can be acquired over the internet, and the chicken pieces can be bought at the local supermarket.
This approach allows a motivated trainee to rehearse different types of surgical techniques several times at a reasonable expense, helping to develop or maintain his surgical expertise if more complex facilities are not available. On the current manuscript we describe how to setup a small practice station, how to dissect the specimens, and how to practice both with the chicken thighs and with the chicken wings in a progressive fashion. This approach takes advantage on the versatility of the chicken thigh model and the small size of the chicken wing Brachial artery.

Here we describe how to set up a small microsurgical practice station and a simple and inexpensive method for the training of microsurgery with non-living animal models.

The learning of microsurgical techniques and the maintenance of microsurgical skills have been traditionally based on the use of living animals, mainly ...

Heterotopic Renal Autotransplantation in a Porcine Model: A Step-by-Step Protocol

Kidney transplantation is the treatment of choice for patients suffering from end-stage renal disease. It offers better life expectancy and higher quality of life when compared to dialysis. Although the last few decades have seen major improvements in patient outcomes following kidney transplantation, the increasing shortage of available organs represents a severe problem worldwide. To expand the donor pool, marginal kidney grafts recovered from extended criteria donors (ECD) or donated after circulatory death (DCD) are now accepted for transplantation. To further improve the postoperative outcome of these marginal grafts, research must focus on new therapeutic approaches such as alternative preservation techniques, immunomodulation, gene transfer, and stem cell administration.
Experimental studies in animal models are the final step before newly developed techniques can be translated into clinical practice. Porcine kidney transplantation is an excellent model of human transplantation and allows investigation of novel approaches. The major advantage of the porcine model is its anatomical and physiological similarity to the human body, which facilitates the rapid translation of new findings to clinical trials. This article offers a surgical step-by-step protocol for an autotransplantation model and highlights key factors to ensure experimental success. Adequate pre- and postoperative housing, attentive anesthesia, and consistent surgical techniques result in favorable postoperative outcomes. Resection of the contralateral native kidney provides the opportunity to assess post-transplant graft function. The placement of venous and urinary catheters and the use of metabolic cages allow further detailed evaluation. For long-term follow-up studies and investigation of alternative graft preservation techniques, autotransplantation models are superior to allotransplantation models, as they avoid the confounding bias posed by rejection and immunosuppressive medication.

Porcine models of organ transplantation provide an important platform to study mechanisms of organ preservation. This article describes a heterotopic porcine renal autotransplantation model, which allows investigating new approaches to improve the outcome of transplantation using marginal kidney grafts.

Kidney transplantation is the treatment of choice for patients suffering from end-stage renal disease. It offers better life expectancy and higher quality ...

A Step by Step Protocol for Subretinal Surgery in Rabbits

Age related macular degeneration (AMD), retinitis pigmentosa, and other RPE related diseases are the most common causes for irreversible loss of vision in adults in industrially developed countries. RPE transplantation appears to be a promising therapy, as it may replace dysfunctional RPE, restore its function, and thereby vision.
Here we describe a method for transplanting a cultured RPE monolayer on a scaffold into the subretinal space (SRS) of rabbits. After vitrectomy xenotransplants were delivered into the SRS using a custom made shooter consisting of a 20-gauge metallic nozzle with a polytetrafluoroethylene (PTFE) coated plunger. The current technique evolved in over 150 rabbit surgeries over 6 years. Post-operative follow-up can be obtained using non-invasive and repetitive in vivo imaging such as spectral domain optical coherence tomography (SD-OCT) followed by perfusion-fixed histology.
The method has well-defined steps for easy learning and high success rate. Rabbits are considered a large eye animal model useful in preclinical studies for clinical translation. In this context rabbits are a cost-efficient and perhaps convenient alternative to other large eye animal models.

Retinal pigment epithelium (RPE) replacement strategies and gene-based therapy are considered for several retinal degenerative conditions. For clinical translation, large eye animal models are required to study surgical techniques applicable in patients. Here we present a rabbit model for subretinal surgery geared towards RPE transplantation, which is versatile and cost-efficient.

Age related macular degeneration (AMD), retinitis pigmentosa, and other RPE related diseases are the most common causes for irreversible loss of vision in ...

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.

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 ...

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 ...

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 ...

Endoscopic Ultrasound-Guided Biliary Drainage: Endoscopic Ultrasound-Guided Hepaticogastrostomy in Malignant Biliary Obstruction

Patients with unresectable malignant biliary obstruction often require biliary drainage to decompress the biliary system. Endoscopic Retrograde Cholangiopancreatography (ERCP) is the primary biliary drainage method whenever possible. Percutaneous Transhepatic Biliary Drainage (PTBD) is used as a salvage method if ERCP fails. Endoscopic Ultrasound-Guided Biliary Drainage (EUS-BD) provides a feasible alternative biliary drainage method where one of the methods is EUS guided Hepaticogastrostomy (EUS-HGS). Here we describe the EUS-HGS technique in a case of unresectable malignant hilar biliary obstruction to achieve biliary drainage.
Presented here is the case of a 71-year-old female with painless jaundice and weight loss for 2 weeks. Computed Tomography (CT) imaging showed a 4 x 5 cm hilar tumor with lymphadenopathy and liver metastasis. EUS fine needle biopsy (FNB) of the lesion was consistent with cholangiocarcinoma. Her bilirubin levels were 212 &#181;mol/L (&lt;15) during presentation.
A linear echoendoscope was used to locate the left dilated intrahepatic ducts (IHD) of the liver. The segment 3 dilated IHD was identified and punctured using a 19 G needle. Contrast was used to opacify the IHDs under fluoroscopic guidance. The IHD was cannulated using a 0.025-inch guidewire. This was followed by the dilation of the fistula tract using a 6 Fr electrocautery dilator along with a 4 mm biliary balloon dilator. A partially covered metallic stent of 10 cm in length was deployed under fluoroscopic guidance. The distal part opens in the IHD and the proximal part was deployed within the working channel of the echoendoscope that subsequently released into the stomach. The patient was discharged three days after the procedure. Follow up performed in the second and fourth weeks showed that the bilirubin levels were 30 &#181;mol/L and 14 &#181;mol/L, respectively. This indicates that EUS-HGS is a safe method for biliary drainage in unresectable malignant biliary obstruction.

Endoscopic Ultrasound-Guided Biliary Drainage (EUS-BD) is an alternative method of biliary decompression in malignant biliary obstruction. Here we describe the technique of EUS guided-Hepaticogastrostomy (EUS-HGS) in a case of unresectable malignant hilar biliary obstruction.

Patients with unresectable malignant biliary obstruction often require biliary drainage to decompress the biliary system. Endoscopic Retrograde ...

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. ...

Transoral Endoscopic Thyroidectomy Vestibular Approach for Thyroid Lobectomy

The manuscript describes the transoral endoscopic thyroidectomy vestibular approach (TOETVA) for thyroid lobectomy. The patient is placed in the supine position with extension and fixation of the neck. One 20 mm transverse incision and two 5 mm incisions are made through the mucosa of the oral vestibule for camera and instrument placement after disinfection of the skin and oral cavity. The workspace is established and maintained by the skin suspension device, which is made of unabsorbable string (3-0) and rubber bands, and the CO2 insufflation pressure. Lobectomy using a medial-to-lateral technique and prophylactic ipsilateral central neck dissection is performed simultaneously on patients with papillary thyroid cancer (PTC). The specimen is extracted through the 20 mm incision. The parathyroid gland is immediately searched for in the specimen and auto-transplanted to the left brachioradialis. A drainage tube is inserted through the retractor hole into the bed of the thyroid gland, and absorbable sutures are used to close the mucosal incisions in the oral vestibule and the linea alba cervicalis. Prophylactics administered intravenously are recommended for the first 24 h after surgery, and oral antibiotics are used for 7 days postoperatively.

Here, we present a protocol to describe the methodology for the transoral endoscopic thyroidectomy vestibular approach in detail.

The manuscript describes the transoral endoscopic thyroidectomy vestibular approach (TOETVA) for thyroid lobectomy. The patient is placed in the supine ...