Advantages of endoscopic surgery

Several authors have described previously that the use of endoscopes in the surgical management of otosclerosis leads to better visualisation of the middle-ear structures, thereby allowing less traumatic and invasive surgery, and potentially better audiological outcomes (Table 3).^{Reference Daneshi and Jahandideh1,Reference Marchioni, Soloperto, Villari, Tatti, Colleselli and Genovese5–Reference Kojima, Komori, Chikazawa, Yaguchi, Yamamoto and Chujo11,Reference Naik and Nemade13–Reference Hunter, Zuniga, Leite, Killeen, Wick and Ramirez18}

Table 3. Summary of published literature regarding audiological outcomes after endoscopic stapes surgery

Pre-op = pre-operative; ABG = air–bone gap; N/A = not available

Bennett et al.^{Reference Bennett, Zhang, Labadie and Noble19} corroborated those assumptions by demonstrating that endoscopes allow better exploration of several middle-ear regions – except the antrum – as compared with the microscopic view. In addition, Daneshi and Jahandideh demonstrated several benefits of using the endoscopic approach for stapes surgery, including the decreased surgery time, the possibility of performing the whole surgery with less drilling and trauma, and audiological results that are similar to those achieved using the operating microscope.^{Reference Daneshi and Jahandideh1}

These advantages further support the association of endoscope use with less risk of intra-operative chorda tympani nerve injury and a decreased prevalence of post-operative transient vertigo. However, only a few studies compared the audiological outcomes of microscopic versus endoscopic techniques in stapes surgery (Table 2).

Disadvantages of endoscopic surgery

Although generally associated with less trauma, the use of endoscopes for stapes surgery can be challenging, especially for surgeons who are not experienced in otological surgery. The one-handed surgical technique is probably the most critical issue. Excessive bleeding may preclude the use of endoscopes; therefore, attention to haemostasis is essential to complete the procedure with one hand alone. Furthermore, the two-dimensional image provided by the endoscope may lead to loss of stereoscopic vision (loss of depth perception). Stereoscopic vision is fundamental for ear surgery, and some of the crucial steps of stapes surgery (e.g. cutting the stapedial limb or tightening the wire) require an adequate sense of depth.

Other disadvantages include the need for additional physician training and the cost of equipment. Experienced otolaryngologists who routinely perform nasal endoscopy or functional endoscopic sinus surgery are more likely to master these necessary skills in a shorter time. However, otological surgeons who lack extensive endoscopic training may find it difficult to perform these procedures using endoscopes. The availability of equipment is not an issue, as most hospitals do have the necessary equipment available in the operating theatres, and the required instruments are minor modifications of existing ones. It has been previously suggested that the extra costs associated with new equipment and instruments are justified in the long-term, when one considers the shorter surgery time and the reduced number of in-patient days associated with less traumatic procedures;^{Reference Tarabichi7} however, our findings do not robustly support such an argument. Further prospective studies that include a larger sample of patients operated on by surgeons who are experienced in fully endoscopic ear surgery may corroborate those assumptions.

Surgical considerations

All studies reviewed were in concordance that the endoscopic technique has advantages over conventional techniques. These advantages include an excellent view of the oval window niche and anterior crus, allowing less manipulation of the chorda tympani and less bone drilling.

Daneshi and Jahandideh,^{Reference Daneshi and Jahandideh1} Kojima et al.^{Reference Kojima, Komori, Chikazawa, Yaguchi, Yamamoto and Chujo11}, and Iannella and Magliulo,^{Reference Iannella and Magliulo6} demonstrated that using the endoscope may allow less external auditory canal bone removal as compared with surgery performed using the microscope, leading to lower rates of post-operative pain. However, our review of the literature revealed that, in 10 studies (71.4 per cent), the authors either routinely or occasionally removed the scutum. Thus, these results suggest that, despite the better view provided by the endoscope, manipulation of the external ear canal and of the annulus is still needed in a significant proportion of cases.

Regarding surgery duration, the selected studies described inconsistent results. Iannella and Magliulo^{Reference Iannella and Magliulo6} showed reduced operation time with the microscopic technique (36.5 vs 45.0 minutes, p = 0.01), while Daneshi et al.^{Reference Daneshi and Jahandideh1} demonstrated reduced surgery time with the endoscopic approach (31.78 vs 54.33 minutes, p = 0.05). Although most studies generally reported that the surgical procedures performed with an endoscope were faster than those performed with a microscope, the studies do not provide sufficient data for analysis to determine whether such a statement is true. In this regard, most of the studies only provided average surgery time, but no range, standard deviations or medians. Furthermore, the learning curve of endoscopic stapes surgery may have had an additional impact on surgery time. In this regard, Iannella and Magliulo^{Reference Iannella and Magliulo6} showed a decrease in operation time from 52.5 minutes in the first three months, to 35.9 minutes after four months. There was no statistical difference between surgery times for each approach in the last period of the study.

Auditory outcomes

The auditory outcome was generally reported among studies as the air–bone gap size. In those studies, 116 of 160 ears (73 per cent) had a residual air–bone gap of less than 10 dB. Also, 199 of 208 ears (96 per cent) had a residual air–bone gap of less than 20 dB after surgical treatment of stapes fixation. There were no significant differences in the mean residual air–bone gap in patients who underwent endoscopic surgery as compared with microscopic approaches among the studies.

Although those results are promising, the study of Vincent et al.,^{Reference Vincent, Sperling, Oates and Jindal20} which used a computerised database to review the auditory results of 3050 stapedotomies performed over 14 years, demonstrated contradictory findings. Those authors reported that 94.2 per cent of their patients had post-operative air–bone gaps of less than 10 dB. However, it must be considered that the endoscopic-assisted techniques may require extra training and have different learning curves. Thus, to better assess the real differences between endoscopic and microscopic approaches for stapes surgery, further well-designed, randomised, prospective studies, which include a large number of patients undergoing procedures performed by experienced surgeons who are extensively trained in endoscopic ear surgery, are warranted.

Complications

Four studies showed a smaller incidence of chorda tympani nerve injury in the endoscopic surgery group as compared with the microscopic technique group. Such a difference may be explained by the better view of the middle-ear structures. Iannella and Magliulo showed reduced post-operative pain in patients who underwent endoscopic approaches as compared with traditional microscopic surgery (90 per cent and 75 per cent of pain absence, respectively).^{Reference Iannella and Magliulo6} The same study demonstrated similar rates of dizziness on the first day after surgery in both groups, which affected up to 80 per cent of patients. Dursun et al.^{Reference Dursun, Özgür, Terzi, Oğurlu, Coşkun and Demirci14} reported tympanic membrane perforation in three patients who underwent endoscopic stapes surgery.

Endoscopy versus operating microscope

The first study to report the comparison between endoscopic stapes surgery and conventional stapes surgery using an operating microscope was performed by Kojima et al., in 2014.^{Reference Kojima, Komori, Chikazawa, Yaguchi, Yamamoto and Chujo11} In their study, 15 patients underwent endoscopic surgery (15 ears) and 35 patients underwent microscopic surgery (41 ears). The authors found no differences in operating time and post-operative air–bone gap between the two techniques (air–bone gap of less than 20 dB in 93.3 per cent of the endoscopic group and in 97.5 per cent of the microscopic group). Only one patient in the endoscopic group complained of facial palsy, which fully recovered one month after the procedure. No patient complained of dysgeusia in the endoscopic group, while four patients reported this complaint in the microscopic group.

Daneshi and Jahandideh compared the results of 19 patients who underwent endoscopic stapes surgery versus 15 patients who underwent microscopic surgery.^{Reference Daneshi and Jahandideh1} They found similar audiological results for both techniques (94.71 per cent in the endoscopic group vs 93.33 per cent in the microscopic group). The authors reported a shorter surgery duration in the endoscopic group than the microscopic group (p < 0.05), and higher patient satisfaction rates in the endoscopic group as compared with the microscope group (p < 0.05). No cases of dead ear, facial nerve palsy or dysgeusia were observed.^{Reference Daneshi and Jahandideh1}

In 2016, Iannella and Magliulo found no statistical differences in the audiological outcomes following endoscopic or microscopic approaches (20 patients in each group).^{Reference Iannella and Magliulo6} No cases of facial palsy were reported. Four patients in the endoscopic group and five patients in the microscopic group reported transient dysgeusia. The authors also found that total operative time was higher in the endoscopic group compared to the microscopic group (p = 0.01), which might be explained by the lack of surgeon experience for the first cases. Additionally, they observed that total operative duration decreased over time in the endoscopic group (potentially related to the learning curve), but remained similar in the microscopic group over the study period.^{Reference Iannella and Magliulo6}

Iannella and Magliulo,^{Reference Iannella and Magliulo6} and Surmelioglu et al.^{Reference Surmelioglu, Ozdemir, Tarkan, Tuncer, Dagkiran and Cetik16} reported statistically significant differences in total operative times between the two techniques (p = 0.033). However, Surmelioglu et al. found that total operative time was shorter in the endoscopic group. Nevertheless, they observed a more significant air–bone gap difference from the pre- to the post-operative period in the endoscopic stapedotomy group (p = 0.023).

Finally, Sproat et al.^{Reference Sproat, Yiannakis and Iyer17} found that 79 per cent of both endoscopic and microscopic groups had an air–bone gap of less than 10 dB HL. However, the air–bone gap closure did not vary significantly between the two groups. Furthermore, no cases of vertigo, facial nerve palsy or sensorineural hearing loss were reported.