Introduction
Patients with stones of the parotid gland and its duct were usually treated by partial parotidectomy in previous years. Extracorporeal shock wave lithotripsy reduced the number of surgeries but is not generally available and is successful in only about two-thirds of cases. Today, sialendoscopy has led to a new, transoral approach. Smaller stones can be extracted with sialendoscopy and a basket.
Larger stones can potentially be treated with extracorporeal shock wave lithotripsy or intraductal laser lithotripsy prior to sialendoscopic extraction. Intraductal laser lithotripsy is possible with working channels of only 0.4 mm. Therefore, it is often possible to reach the stone with the endoscope. However, intraductal laser lithotripsy is time consuming. Mechanical methods such as intraductal pneumatic lithotripsy are dependent on larger working channels and intraductal pneumatic lithotripsy is precluded if the ducts are narrow.
An additional approach uses sialendoscopy and/or ultrasonography as navigation methods to guide a minimally-invasive transcutaneous intervention. The first description of this type of approach was probably the use of a probe inserted into the duct for mechanical localization of the stone. Currently, this type of surgical approach is usually addressed by the term “combined approach”.
Combined Transoral and External Approach
Combined approaches can be further categorized depending on the stone localization technique (sialendoscopic, ultrasonographic) and the type of incision (direct, posterior/parotidectomy).
The method used for localization depends on various factors: availability of instruments; acquaintance of the surgeon with the methods; duct diameter and tortuosity; and localization of the stone. In rare cases, stones can be palpated either from the outside or with a blunt probe through the papilla of Stensen’s duct. In these cases, neither ultrasound nor endoscopy are necessary for localization. However, sialendoscopy and ultrasound, in these cases, can add information by ensuring that no further stones remain. Some stones cannot be reached by sialendoscopy. In these cases, ultrasonography is a remaining alternative.
The selection of the incision also depends on various factors, including location of the stone, age, and gender of the patient. If the risk of a visible scar is paramount, a posterior approach, as used for parotidectomy, is preferred. This is usually possible as the skin is very flexible. However, for anterior located stones, the amount of skin preparation necessary, risk of nerve trauma (both sensory and motor), and duration of surgery might increase.
Combined Transfacial Incision Approach
The direct incision technique is illustrated in the following example: A 48-year-old male patient had several stones identified sonographically in Stensen’s duct about 2.5 cm anterior of the gland. Different therapeutic options including extracorporeal shock wave lithotripsy and intraductal lithotripsy were discussed with the patient. He chose a combined approach including a direct incision above the stone. The position of the stone was marked by transillumination using sialendoscopy ( Figs. 20.1 , 20.2 ). Using facial nerve monitoring, an incision was performed directly above the stones along the relaxed skin tension lines. Judiciously, the tissue was divided. It was possible to identify the buccal branch of the facial nerve with the operating microscope. The facial nerve branch was confirmed by neural stimulation with a nerve integrity monitoring probe ( Fig. 20.3 ). The light of the microscope was dimmed intermittently to confirm the exact position of the stone ( Fig. 20.4 ). The stone was located deep to the facial nerve branch. The facial nerve branch is meticulously separated from surrounding tissue and carefully mobilized cranial to the duct ( Fig. 20.5 ). With the duct visible, it was incised with a 15 blade and the sialodochotomy was enlarged using fine plastic scissors. Stones were extracted with a blunt hook ( Fig. 20.6 ). Fig. 20.6 also shows the tip of the sialendoscope inside the duct. Multiple stones were retrieved. The sialendoscope confirmed that no further stones remained inside the duct system. A drain was attached to the tip of the endoscope ( Fig. 20.7 ) and the endoscope was withdrawn intraorally. The duct was closed using 5-0 resorbable sutures. Subsequently, the overlying soft tissue and the skin were closed. The sialodrain was sutured to the buccal mucosa ( Fig. 20.8 ). This technique has since progressed, and currently the authors seldom insert drains because sialodrains are usually not necessary and may even block the flow of saliva.
Combined Parotidectomy-Like Posterior Approach
The second case is an example of a posterior parotidectomy-like skin incision. It has different indications.
In a 58-year-old male, a stone was posterior to the masseter muscle inside the intraparenchymal part of Stensen’s duct ( Fig. 20.9 ). Endoscopically, it was difficult to reach the stone. The stone was within a secondary duct behind a stenosis ( ). It was barely possible to reach it with a thin diagnostic sialendoscope. The authors discussed with the patient extracorporeal shock wave lithotripsy versus a combined approach. He chose the latter.
