In recent years, more congenital middle ear cholesteatoma cases have been reported in children due to the widespread application of outpatient otoendoscopy and the improvement of clinicians' awareness of the disease. However, due to the characteristics of "short, flat and straight" eustachian tube in children, some children were diagnosed with CMEC only when tympanic membrane perforation and ear discharge occurred. Other children might be diagnosed when they visited hospital for secretory otitis media which were excluded by Levenson's criteria[4–6].Since the lack of timely and accurate expression of unilateral hearing loss in children at a younger age, they are often sent to specialists when failed the hearing screening. In this study, 3 children did not pass the hearing screening and then were diagnosed with CMEC. Gilberto[7] suggest that routine hearing screening should be carried out for children entering kindergarten and school. For children who fail the hearing screening, otoendoscopic temporal bone CT should be performed. In this paper, 11 children underwent outpatient otoendoscope examination and all of them were found to have white localized mass shadows on the inner side of intact tympanic membrane. Therefore, the early detection rate of CMEC can be improved by using otoendoscope as a routine examination method for children with hearing loss or hearing screening failure in outpatient department. In addition, for children with secretory otitis media if Symptoms do not improve for a long time after treatment, temporal bone CT should be considered to perform to exclude CMEC.
The pathogenesis of CMEC is still unclear. Currently, there are epidermoid theory, drum ring development disorder theory, metagenesis theory, ectoderm implantation theory, etc. Among them, the epidermoid theory has been widely accepted. Although the accumulation of keratoid epithelium is benign, it can grow progressively and destroy normal surrounding tissue[7]. Congenital cholesteatoma in the posterior attic quadrant of the eardrum is often detected late in routine ear examinations because the eardrum is more opaque. Due to the adjacent ossicular chain, facial nerve and other organizational structures, congenital cholesteatoma occurring in the posterior quadrant is more invasive and can cause serious intracranial and external complications. In this study, 4 children with stage III CMEC all occurred in the posterior quadrant. Therefore, early detection and early treatment of CMEC is particularly important to avoid the occurrence of serious complications.
Currently, surgical treatment is the only treatment for CMEC[8]. The main objectives of surgery are to completely remove lesions, prevent recurrence, preserve or rebuild hearing. For patients with CMEC, the classical surgical methods are complete wall mastoid radical resection and tympanoplasty according to the lesion scope. For localized lesions of stage I and stage II, some scholars also used enlarged tympanum exploration [9]. CMEC children’s mastoid gasification is good and lesions are limited. Radical mastoidectomy is more traumatic and children needs to be cleaned regularly in the clinic which cause children poor cooperation. Moreover, microscopic exposure of the attic tympanum, facial recess and tympanum sinus is limited which may cause incomplete removal of the lesion and recurrence. We chose the surgical treatment of CMEC under otoendoscope based on the literature report that CMEC within stage III can be treated through the ear canal approach under the microscope. This approach can avoid damage to mastoid bone and air chamber with mild lesions [10]. For stage III CMEC, it could also be completed by ear canal approach when lesion is localized and mastoid process is not invaded before surgery. The stage III cases in this paper were all underwent surgeries by otoendoscope. The application of angle scope also helped to preserve the bone wall of the external auditory canal and the lateral wall of the upper drum. External auditory canal exudation and dressing time decreased significantly.
It is reported that the recurrence rate of CMEC in children is 10.5%-45%[11, 12]. At present most reports on CMEC are small-sample reports[7, 11, 13–16], so there is no data to prove that otoendoscope can reduce the recurrence rate of CMEC. With the development of ear endoscopy, ear endoscopy with a diameter of 2.7 mm and 1.9 mm can pass through the narrow ear canal, increase the surgical field of vision, improve the clarity of the surgical field and observe tissue from multiple angles at close range[17]. Otoendoscope can provide a clear vision for the superior tympanum, facial crypt, tympanum sinus, eustachian tube and other concealed anatomical sites. The incision of otoendoscopic surgery is small and it is easier for families to accept even the children who plan to have a second surgery. Another difficulty of CMEC children is the stenosis of the ear canal. When preoperative CT indicates that the anteroposterior diameter of middle part of external auditory canal (midpoint of ear canal opening and umbilical point of eardrum) ear bone wall exceeds 4.5 mm, an otoendoscope with a diameter of more than 2.7 mm can be used for operation [18]. The anteroposterior diameter of the isthmus of the external auditory canal in Chinese children is 3.27±0.75 mm for 0-5 years old and 4.01±0.75 mm for 6-15 years old. If the external auditory canal bulge affects the surgical field, curettors or electric drills can be used to expand the external auditory canal to increase the surgical field of vision. Due to the thin skin of children's ear canal, protection of ear canal flap is important which can avoid postoperative scar stenosis.
In this study, all 11 children were treated with transcanal endoscopic surgery. In 1 case, cartilage connection was implanted because of low position of facial nerve and the hearing was not recovered after surgery. The second surgery to reconstruct hearing was considered. In another case, tympanic membrane fissure occurred during surgery separation. The eardrum is repaired with perichondrium at the same time. The healing was good 3 weeks after surgery. Up to now, hearing of all cases has been significantly improved. The 7 cases of stage I and stage II were young and prompt diagnosis. Their external auditory canal and shield plate were not expanded during the surgery. The ABG was reduced to within 10 dB HL after surgery and recovered dry ear in about 2 months. The 4 cases of stage III were all over 7 years old which may be related to the lack of early birth examination and hearing screening. 1 case planned to undergo the second surgery for hearing reconstruction, the hearing was significantly improved in other 3 cases. In order to clarify the lesion, there were different degrees of external auditory canal enlargement. All the children recovered dry ears within 3 months after surgery and no auditory ossicle discharge, displacement and recurrence were observed.