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 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°, 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.
Congenital cholesteatoma (CC) accounts for 25% of cholesteatoma cases in children, and its proportion within cholesteatoma cases has increased in recent years due to improved public health measures and earlier detection worldwide1,2. The size and ossicular involvement of CC significantly impact the prognosis and surgical strategy. As a result, CC can be classified according to the Potsic classification3. When diagnosed early, these lesions are typically confined to the tympanic cavity or may extend to the epitympanum with an intact matrix, involving the ossicles (Potsic stage III) or not (Potsic stage I or II). In more advanced cases, distinguishing CC from acquired cholesteatomas can be challenging, with diffluent lesions in the epitympanum or mastoid regions and altered tympanic membranes (Potsic stage IV).
Patients with CC without mastoid involvement (Potsic stage I to III) make excellent candidates for total endoscopic ear surgery (TEES), which involves a minimal trans-canal incision and offers an excellent view of the entire tympanic cavity and epitympanic region. Numerous studies have demonstrated that TEES yields similar residual rates compared to the traditional microscopic approach4,5,6,7,8,9. TEES has been adopted by many pediatric otology centers worldwide, providing a safe and efficient technique that also enhances ergonomics for surgeons, allowing them to sit upright while facing the screen5,7,8,10. However, during TEES, safely dissecting the ossicles can be challenging in stage III lesions due to the lack of counter-stabilization when using an instrument in the second hand, increasing the risk of ossicular subluxation and inner ear trauma from excessive ossicle mobilization. Additionally, the lack of suction during dissection can lead to poor visibility due to bleeding or endoscope fogging. A robotic arm designed for middle ear surgery and cochlear implantation has been employed as a robotic dynamic endoscope holder, providing six degrees of freedom, including three translational and three rotational axes throughout the procedure. Its safety during robot-assisted TEES has already been reported in the adult population11.
This article reports the robotic setup and surgical procedure for a stage III congenital cholesteatoma in a 3-year-old child, using robotic-assisted TEES. This approach allows for the dissection of the cholesteatoma with two hands while benefiting from an endoscopic view and a trans-canal approach.
This study was conducted in compliance with the European GDPR and registered at AP-HP, Hôpital Necker – Enfants Malades (number 20200727144143). The study adhered to the CARE guidelines12, and both parents provided written consent to record the surgical video of the procedure and to publish a case report13,14. The surgical strategy mirrored the one typically used in our tertiary referral center with a microscope, involving the use of both hands. The primary difference was the surgical approach, which was trans-canal, eliminating the need for atticotomy or canalplasty.
1. Pre-operative procedures
2. Preparation for the surgery
3. Onset of the surgery
4. Congenital cholesteatoma (CC) procedure
The case study reports a robotic-assisted total endoscopic ear surgery (TEES) for a Potsic stage III left congenital cholesteatoma in a 3-year-old child. The robotic arm was equipped with a 0° and 30°, 25 cm long, and 2.9 mm wide scope, connected to a 1080p full-HD camera and screen.
The pre-operative work-up revealed a typical congenital cholesteatoma with a CT scan showing a round anterior mass medial to the malleus, extending posteriorly between the stapedial crus and anteriorly into the supratubal recess (Figure 3). The ossicular chain remained intact. Audiometric testing indicated a slight 10 dB conductive hearing loss on the side of the lesion (Figure 4). The 3-year-old patient had a narrow external auditory canal, allowing only a size 3 speculum to be inserted. Therefore, the microscope was prepared as a backup, and the family was informed that an endaural approach might be necessary.
The installation of the robotic arm took 16 min, and the overall installation time (from intubation to incision, including all draping and instrument preparation) was 27 min. The total surgery duration (from intubation to closure) was 2 h and 9 min. The entire TEES was conducted with a 0° endoscope, except for a 10 min interval when a 30° scope was used to examine between the stapedial crus and the epitympanum. The microscope was not utilized.
A tragal graft was harvested through a direct incision and sutured before the endoscopic stage. The tympano-meatal flap was elevated from the malleus after a trans-canal approach, following which the congenital cholesteatoma (CC) was debulked, dissected from the incus and stapedial crus, and pushed forward under the malleus (Figure 5). It was then removed with an intact anterior and superior matrix. Due to the large size of the CC, a tragal graft was placed in an underlay fashion to prevent any future tympanic retraction before repositioning the tympano-meatal flap.
The procedure proceeded without surgical difficulties, particularly concerning the use of the robot. Passive movement of the endoscope could occur if it was pushed aside by an instrument, but this was gradual and did not obstruct the vision. Conversely, the instruments remained secure and stable throughout the procedure.
At the 6-week follow-up, the tympanic membrane and external auditory canal were healed without any epidermal inclusion cyst or myringitis. The 6-week post-operative audiometry indicated a slight conductive hearing loss, likely due to the use of underlay cartilage to reinforce the tympanic membrane. Importantly, there was no sensorineural hearing loss, which was the primary concern after extensive ossicular manipulation and dissection. The patient will undergo non-EPI diffusion-weighted MRI scans at 18 and 36 months after surgery, along with clinical and audiological follow-up for 8 to 10 years1.
Figure 1: Operating theatre setup for left tympanoplasty. In this proposed setup, the robot is positioned opposite the surgeon, aligned with the patient's external auditory canal axis. For a left tympanoplasty, the video tower is placed slightly to the left, towards the patient's feet. In the case of a right tympanoplasty, where the external auditory canal axis differs, the robot would be positioned towards the patient's feet. Please note that the surgical microscope should be draped and located in a corner of the room, though it's not depicted in the figure. Please click here to view a larger version of this figure.
Figure 2: Peri-operative installation for left tympanoplasty. (A) The robot arm holder centralizes the endoscope to evenly distribute weight and minimize tube tension. (B) Observe the positioning of the video tower on the side opposite to the surgical field. The surgeon has a multi-directional control device, the space mouse, on the left for controlling the robotic endoscope holder. (C) The surgeon performs surgery on the left ear, facing the video tower, which is placed on the opposite side of the patient. (D) A close-up view from the surgeon's perspective shows the robotic arm holding the endoscope in line with the external auditory canal. Both surgical hands remain free for instrument manipulation and suction, akin to the conventional microscopic technique. The endoscope is capable of tilting, rotating, and translating at varying speeds using the space mouse. Please click here to view a larger version of this figure.
Figure 3: Pre-operative CT-scan. The lesion is marked with an asterisk (*). (A) The transverse plane reveals an extensive congenital cholesteatoma involving the malleus and extending anteriorly into the supratubal recess. (B) In the transverse plane, the supratubal recess (§) is clearly visible, along with the extension between the crus of the stapes, which appears intact (stage III congenital cholesteatoma). The retrotympanum (marked with ¤) is devoid of any lesions. (C) The coronal plane displays a typical round mass medial to the malleus. (D) In the coronal plane, the extension of the lesion into the supratubal recess (§) is shown anteriorly. Please click here to view a larger version of this figure.
Figure 4: Audiometry (pre and post-operative). Left: Pre-operative audiometry reveals a slight 10 dB conductive hearing loss in the left ear, causing a minor asymmetry with the normal hearing in the right ear. Right: Six weeks post-operation, a 10 dB conductive hearing loss is observed in the left ear (likely due to the underlay cartilage graft), but notably, there is no sensorineural hearing loss. The x-axis represents hearing loss in decibels (dB), while the y-axis indicates frequencies in Hertz (Hz). Please click here to view a larger version of this figure.
Figure 5: Endoscopic view (0° endoscope). (A) This is an immediate pre-surgical view, where the anterior congenital cholesteatoma presses against the intact tympanic membrane. (B) The tympano-meatal flap has been elevated from the malleus, fully exposing the congenital cholesteatoma from the stapedial crus at the rear to the supratubal recess at the front. (C) After cholesteatoma removal, the ossicular chain remains intact. Note the broad scope of the 0° endoscope view, spanning from the Eustachian tube at the front to the stapes at the rear. The black arrowhead in (A) and (B) points to the congenital cholesteatoma, which is removed in (C). Please click here to view a larger version of this figure.
This study reports the successful use of a robot-assisted totally endoscopic procedure to remove a stage III congenital cholesteatoma in a 3-year-old child. Total endoscopic ear surgery (TEES) is particularly interesting in the pediatric population, as performing tympanoplasties with a keyhole trans-canal approach reduces healing time and the amount of immediate post-operative care. Regarding cholesteatoma surgery, many studies have now demonstrated that TEES yields similar, if not smaller, residual rates in selected patients compared to microscopic postauricular or endaural approaches4,5,10.
Stage I or II congenital cholesteatoma (CC) are, of course, ideal cases for TEES, with excellent results. In these cases, there is no ossicular involvement, visibility is often excellent, and the CC does not extend into high-risk areas of residual disease, such as the retrotympanum or anterior epitympanum4,5,6,7,8. Difficulties may arise in stage III or IV CC, where dissecting ossicles or removing extensive lesions is required with only one hand. In traditional microscopic two-handed surgery, the second hand typically holds a suction device, which can enhance vision by removing blood but also plays a key role in tissue manipulation and ossicular control during dissection.
The robotic endoscope holder represents an innovative and secure solution to combine the advantages of TEES with a two-handed procedure11. This case report demonstrates the feasibility of using this technology in a young 3-year-old child, where a 2.9 mm endoscope, two instruments, and sufficient working space could be accommodated within the child's narrow external auditory canal, enabling work on the stapes and exploration of the epitympanum.
Other systems have been used to combine endoscopic vision with a two-handed approach, facilitating bi-manual manipulation of grafts and prostheses or blood suction16,17,18,19,20. Although some steps during TEES that require a second operative hand can be done with the assistance of another individual (holding the camera or suction), endoscope holders make the entire TEES procedure feasible with two hands, which can be advantageous for surgeons accustomed to this configuration with the microscope. Rigid mechanical endoscope holders may be suitable for short and simple type 1 myringoplasties18, but they restrict movement, preventing the surgeon from quickly approaching the surgical field or adjusting the view. Therefore, dynamic holders, such as robotic endoscope holders, offer dynamic movement as well as the best precision and security compared to other manually-set dynamic holders16,20, particularly in a middle ear with an intact ossicular chain. Dangerous head movements may occur during otologic procedures, posing a risk of significant trauma during TEES21. As in most otology procedures near the oval window, we recommend securing the head with an adhesive elastic band (as detailed in step 2.4) since the robotic arm cannot automatically move with the patient's head.
The main limitation of the robotic method is the very narrow ear canal in children with craniofacial anomalies (such as Down syndrome), which may render it impossible to simultaneously insert the endoscope and two hand-held instruments. Additionally, diseases that extend posteriorly beyond the lateral semicircular canal may necessitate a larger incision. As previously mentioned (see steps 1.3 and 1.4), careful pre-operative planning and the insertion of a size 3 speculum enable the selection of appropriate candidates for the technique.
Robotic-assisted TEES presents a promising option to expand the use of TEES to complex middle ear lesions while benefiting from the advantages of two-handed surgery and dynamic intra-operative movement. The procedure was successful without adding extra surgical time. A large-scale study on a cohort of patients is required to more precisely determine the limits of robot-assisted TEES and discuss its indications compared to traditional microscopic surgery and one-handed TEES.
The authors have nothing to disclose.
The authors would like to thank Collin Medical, Bagneux, France, for their support and la Fondation des Gueules Cassées who helped finance the acquisition of the RobOtol at Hôpital Necker – Enfants Malades, APHP.
0° 2.9 mm 25 cm Endoscope | Collin | RBT-END-0 | Endoscope for otoendoscopy |
Colorado MicroDissection Needle | Stryker | Pointed electrocautery | |
Facial nerve monitoring | |||
RobOtol | Collin | Robot dedicated to ear surgery | |
Space mouse | 3DConnexion | RobOtol control arm | |
Standard otology surgical material | Including amongst standard instruments: speculum, Fisch dissectors |