Discussion

Traditionally, treatment of parotid duct stenoses has been challenging,^{Reference Koch and Iro3} with minimally invasive approaches such as interventional sialendoscopy with repeated blind dilation offering only temporary benefit. In such cases, an unavoidable risk is represented by the need for definitive management with parotidectomy. Currently, sialendoscopy allows better visualisation of these stenoses and employs minimally invasive approaches to their management,^{Reference Koch and Iro4} but parotidectomy continues to be offered in recurrent cases.

Difficult cases, such as parotid duct stenosis with megaduct secondary to previous surgery or to severe infections or abscesses of the parotid gland, can be treated with the help of an imaging assessment viable in the operating room. This surgical setting has been proven to be effective for the treatment of impacted unpalpable parotid stones, thanks to the development of a CT-guided and sialendoscopy-assisted transfacial approach.^{Reference Capaccio, Bresciani, Di Pasquale, Gaffuri, Torretta and Pignataro5,Reference Anicin and Urbancic6}

While it is well known that stenosis can be easily and effectively seen with magnetic resonance sialography, we have developed a novel combined approach based on the digital fusion of CT and magnetic resonance imaging (MRI) for the intra-opera navigation of the parotid gland and duct, in this case through a transoral approach for a distal stenosis. A pull-through sialodochoplasty was performed,^{Reference Kandl, Ong and Gillespie1} and the intra-operative navigation helped surgeons during the dissection to reach the exact site of the stenosis in scar tissue secondary to previous surgery, helping to avoid complications such as facial nerve injury thanks to the precise localisation of the dilated parotid duct. The transoral image-guided approach allows the surgeon to reach stenosis of the distal and mid-third part of the parotid duct; it could also be helpful for the treatment of proximal or intraparenchymal parotid duct stenosis by a transfacial approach.^{Reference Capaccio, Michele and Lorenzo7} Finally, sialendoscopy allows visualisation and confirmation of the lumen of the duct, and this can be helpful to guide the placement of a salivary stent in the exact position.

This technique could be considered highly effective and beneficial in guiding the surgeon to reach the stenosis in an extremely difficult surgical field. This approach is minimally invasive and compared to a traditional parotidectomy it carries fewer risks and morbidities, while when compared to simple dilation under interventional sialendoscopy, it potentially allows better outcomes in terms of recurrences. However, the surgical time could be longer because of the set up of the navigation system, with the need for adequate training, in particular at the beginning of this novel surgical experience.

In addition, in patients with dental implants, MRI may not provide precise results because of the artifacts caused by the implants, leading to a less accurate localisation of the stenosis, which could be considered the major contraindication for this approach. Although the cost of this technological setting is generally higher compared to that of a traditional sialodochoplasty, nowadays neuronavigation is widely diffused in head and neck surgical departments, thus leading to a reduction in and optimisation of healthcare costs.