10% of symptomatic parotid stones cannot be removed by minimally invasive radiological or endoscopic techniques alone. In these cases endoscopically assisted surgical parotid sialolithectomy can be performed via an extraoral approach, reconstituting the duct and preserving functioning glandular tissue. Between 2003 and 2010, 55 consecutive patients underwent endoscopically assisted surgical removal of parotid stones from 57 glands, two having bilateral procedures. Outcome was assessed using a structured questionnaire. 39/55 patients (71%) patients were successfully contacted (40 procedures; one bilateral case). At median follow-up of 3.1 years 28 glands (70%) were symptomless, whilst 11 (28%) were much improved but causing mild or occasional residual symptoms. One patient required postoperative lithotripsy and basket retrieval of a retained stone, but was subsequently symptom free. A further patient was initially symptom free then relapsed, did not respond to lithotripsy and is awaiting further assessment. In 10% of cases a short-lived sialocoele developed postoperatively. No individual reported facial weakness and one had a scar of concern. 37/39 (95%) patients were pleased to have had the operation and would have the procedure contralaterally in similar circumstances. Endoscopically assisted surgical removal of parotid stones is a successful technique with low morbidity that is well received by patients.
60–70% of obstructive salivary gland disease is caused by stones and the annual incidence of symptomatic salivary calculi is estimated at 5.9/100,000 . The overall prevalence of symptomatic calculi in all glands is judged to be 0.45% The impact of stones on the British National Health Service is significant, their surgical removal accounts for £5 million of expenditure per year . Parotid stones account for 20–25% of all symptomatic salivary calculi . In common with submandibular stone disease, parotid stones can cause meal-time related swelling and occasional acute infective episodes as well as trismus . These symptoms are disabling and inconvenient.
Traditionally, superficial parotidectomy has been the surgical solution for parotid stones, but it carries a risk of facial nerve injury (6–7%), facial hollowing and Frey’s syndrome . Minimally invasive techniques, often used in tandem, have been developed in an attempt to reduce morbidity and enable treatment earlier in the disease course when superficial parotidectomy would have been considered too radical. Mobile stones, less than 5 mm in diameter, are suitable for sialoendoscopic or radiologically guided basket or micro-forcep retrieval, techniques that have proved successful in more than 75% of cases . Fixed or larger stones (>5 mm) can be treated with extracorporeal shockwave lithotripsy (ECSWL) with a complete success rate of 60–70% . 20–30% of patients will have retained stones that are asymptomatic . Overall, minimally invasive non-surgical treatment fails to relieve symptoms in approximately 10% of cases, necessitating surgical management.
B aurmarsh et al. first described a surgical approach to parotid duct sialolithectomy which avoided the need for sialadenectomy . It involved identification of the stone with plain radiography and ultrasound before a direct incision in the cheek to remove it. N ahieli et al. and M c G urk et al. have since described modifications of this approach that use sialoendoscopy to more accurately locate the stone. In the latter technique, a preauricular incision then follows (avoiding a direct one) and a skin flap is raised until anterior to the stone. Whilst the success of this procedure has been reasonably well documented, there are limited data on patients’ perceived outcomes.
Materials and methods
55 (29 male and 26 female) patients underwent surgical removal of symptomatic parotid stones at the authors’ hospital between January 2003 and June 2010. Glands were investigated by both ultrasonography and sialography and occasionally by endoscopy, magnetic resonance imaging and plain radiography to determine the position, size and number of stones. The patients undergoing surgical removal of stones represent a group that were either not suitable for ECSWL or basket retrieval or failed to be cured by these less invasive forms of treatment. The unit policy was that small stones (<6 mm diameter) that appeared mobile on sialography were suitable for basket retrieval. Larger or fixed stones <1 cm in diameter and clearly visible on ultrasound scanning were deemed appropriate for lithotripsy, although this involves a series of visits that does not always suit the patient.
All procedures were performed under general anaesthesia. Initially an endoscope is introduced into the parotid duct and the stone, or most distal stone if there are more than one, is localized. By placing the tip of the endoscope close to the stone, increasing the endoscope light to maximum and dimming the theatre lights it is possible to locate its position ( Fig. 1 ). Distal stones are approached via an incision in the cheek, whilst for stones in the proximal or mid part of the duct, which make up the majority of cases undergoing surgical retrieval, a limited modified Blair incision is employed. The extent of the incision depends on the position of the stone, with more distal stones requiring a longer incision. A sub-superficial musculoaponeurotic system (SMAS), supra-parotid fascia skin flap is then raised, ensuring that a radius of 1–2 cm around the stone is cleared, still using the light on the tip of the endoscope as a guide. The parotid faspcia is then divided over the stone and reflected and parotid tissue bluntly dissected with the aim of skeletalizing a length of duct that includes the stone, whilst being wary of the buccal branch of the facial nerve that is invariably associated with the duct. A limited longitudinal ductotomy is performed, the stone or stones removed and the duct irrigated with saline ( Fig. 2 ). The endoscope is then advanced past the surgical site to check for additional stones. Occasionally this is done through the ductotomy rather than the duct orifice if the latter proves difficult. The duct is closed with 6/0 polyglactin (Vicryl™) sutures and the parotid fascia with 4/0 polyglactin.