Nonneoplastic disorders of the salivary glands involve inflammatory processes. These disorders have been managed conservatively with antibiotics, warm compresses, massage, sialogogues, and adequate hydration. Up to 40% of patients may have an inadequate response or persistent symptoms. When conservative techniques fail, the next step is operative intervention. Sialendoscopy offers a minimally invasive option for the diagnosis and management of chronic inflammatory disorders of the salivary glands and offers the option of gland and function preservation. In this article, we review some of the more common nonneoplastic disorders of the parotid gland, indications for diagnostic and interventional sialendoscopy, and operative techniques.
Chronic inflammatory disorders of the parotid gland can usually be related to salivary stasis, ductal obstruction, or reduced salivary flow rates from any etiology.
Traditional management of nonneoplastic disorders of the parotid gland include conservative measures, with surgical management (parotidectomy) reserved for treatment failure.
Sialendoscopy is a relatively new, gland-sparing, minimally invasive technique offering diagnostic capabilities and interventional modalities for management of nonneoplastic disorders of the salivary glands.
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The great majority of nonneoplastic disorders of the salivary glands involve inflammatory processes related to a multitude of underlying etiologies. Historically, these disorders have been managed with conservative measures, including antibiotics, warm compresses, massage, sialogogues, and adequate hydration. Although beneficial for some patients, it has been reported that up to 40% of patients may have an inadequate response or persistent symptoms despite appropriate first steps in management. Traditionally, when conservative techniques fail, the next step is operative intervention. In the case of nonneoplastic disorders of the parotid gland, this would involve superficial or total parotidectomy with all of its potential complications, including facial nerve paresis or paralysis. In 1988, salivary endoscopy techniques were introduced in Europe. Salivary endoscopy is now being practiced widely globally and in the United States. Sialendoscopy offers a minimally invasive option for the diagnosis and management of chronic inflammatory disorders of the salivary glands and offers the option of gland and function preservation. In this article, we review some of the more common nonneoplastic disorders of the parotid gland, indications for diagnostic and interventional sialendoscopy, and operative techniques.
Relevant anatomy and physiology
The parotid gland is the largest of the 3 major salivary glands. It is located anterior to the external auditory canal and lateral to the mandibular ramus and masseter muscle. It is encapsulated by a very dense connective tissue that is continuous with the investing layer of deep cervical fascia in the neck. Histologically, the parotid gland differs from the other salivary glands in that the acinar cells purely secrete a protein-rich serous fluid and there are no mucinous secreting acinar cells. Salivary flow is then mediated through the intercalated ducts, the striated ducts, and ultimately the excretory ducts. The main excretory duct of the parotid gland is known as the parotid duct, or Stenson’s duct. This projects from the anterior surface of the parotid gland where it courses over the masseter muscle and pierces the buccinator to enter the oral cavity at about the level of the second maxillary molar. The anatomy of Stenson’s duct is important when discussing operative techniques. In general, the duct can measure up to 6 cm in length with a diameter anywhere from 0.5 to 1.4 mm. The narrowest segment of the duct is located at the ostium. Specifically pertaining to sialendoscopy, it is important to remember that the parotid papilla is easier to enter but more difficult to navigate compared with the submandibular papilla. The masseter muscle around which the parotid duct curves to enter the mouth can provide a bend to the duct that is endoscopically recognized as the “masseteric bend.”
It is also important to understand the production and flow of saliva as stasis is thought to be a mediator of chronic sialadenitis. The autonomic nervous system plays a major role in regulation of salivary production and flow. The parotid gland receives its sympathetic innervation from postganglionic fibers as they travel with the vascular supply following their synapse in the superior cervical ganglion. The preganglionic parasympathetic fibers originate from the inferior salivatory nucleus associated with the glossopharyngeal nerve. The postganglionic fibers then leave the otic ganglion with the auriculotemporal nerve, where they ultimately find their way into the substance of the parotid gland. The neurotransmitter of the parasympathetic nervous system is acetylcholine, and when binding to muscarinic receptors, the end result is increased production of watery saliva with enhanced flow. This physiologic concept helps to explain why antimuscarinic and anticholinergic medications are implicated in the development of sialadenitis. It also explains why some clinicians prescribe muscarinic agonists, such as cevimeline, in an attempt to increase salivary production and flow in certain salivary gland disorders.
The average daily flow of saliva may range anywhere from 1 to 1.5 L. During rest, the submandibular gland is the main contributor to salivary flow but during stimulation, the parotid gland is thought to contribute to more than 50% of salivary production. Any process that may promote the disruption of anterograde salivary flow (sialolithiasis, stenosis, anatomic anomaly, or medications) can ultimately lead to problems with obstructive sialadenitis that lead to acute or chronic symptoms for patients.
Acute suppurative parotitis
As discussed, salivary stasis owing to any cause may be a precipitating factor for the development of acute bacterial sialadenitis. It is commonly encountered in the elderly population after an inciting event, although it can happen in any age group. Patients usually present with acute onset of pain, edema, and overlying skin changes at the level of the parotid gland. Physical examination may demonstrate induration, fluctuance, and trismus. On occasion, purulence can be expressed from Stenson’s duct and, if present proximally, stones may be palpable. Computed tomography (CT) scan or ultrasound may be used to identify sites of potential obstruction or development of an abscess ( Fig. 1 ). Ultrasound can not only be beneficial in the diagnosis of abscess formation, but can also be valuable intraoperatively to localize the abscess cavity.
When exudate can be expressed from the main excretory duct, it should be collected and sent for culture and sensitivity. While awaiting results, empiric intravenous antibiotic therapy should be initiated to address the most common etiologic organisms. Multiple microbes have been implicated in the development of acute bacterial sialadenitis, but Staphylococcus aureus accounts for the overwhelming majority of organisms cultured out. In addition to antibiotic therapy, warm compresses, sialogogues, and massage should also be encouraged. Most patients respond with appropriate medical management, but some fail and go on to develop complications, including intraparotid abscess. Surgical management with incision and drainage is indicated in these cases. The use of ultrasound guidance may also be used for needle aspiration and drainage where appropriate. Currently, interventional sialendoscopy is contraindicated in the management of acute sialadenitis for fear of ductal injury, complications, and spread of infection. We have found salivary endoscopy to be valuable in the management of acute parotitis. In the senior author’s experience, for patients not responding to medical management within 48 hours, we have performed dilation of the parotid duct and a conservative endoscopic washout of the parotid ductal system. Although the endoscopic intervention does not decrease induration of the infected gland, patients who have undergone this intervention reported significant pain relief and benefit. Our work needs to be substantiated by larger numbers and is currently unpublished. Consequently, for practical purposes, until these results can be validated, endoscopic intervention for acute parotitis must be considered with caution.
Some patients may present with similar symptoms of acute parotid swelling, extreme tenderness, and xerostomia, but they may lack purulence or other signs of suppurative infection. It is important to consider other infectious causes for salivary gland enlargement, and these will primarily be viral in nature. Mumps is the most common viral cause of parotitis, but will commonly be seen with bilateral parotid gland enlargement. The incidence of mumps has markedly been reduced after the advent of childhood immunization. Other viral etiologies to consider include Coxsackie virus, cytomegalovirus, influenza virus, and the human immunodeficiency virus. Diagnosis may be made with serology, although management is usually conservative and symptomatic in nature.
Chronic sialadenitis may develop as a consequence of repeated infections of the salivary glands, of which the parotid gland is the most likely to be affected. With the development of recurrent parotitis, the acini of the gland are destroyed and it becomes dysfunctional overtime resulting in xerostomia, among many other symptoms. As discussed, it is important to investigate why these patients are developing these recurrent inflammatory processes. History and physical examination may help to elicit underlying etiologies. Imaging will also play an important role in establishing a diagnosis. CT and ultrasonography are both good initial measures when considering salivary gland pathology. They can assist with identification of cysts, neoplasms, or calculi within the gland. Sialography is a valuable option when considering ductal pathology. More recently, MRI sialography, a unique technique using saliva as a contrast medium for the visualization of the salivary ductal system, has also been used to demonstrate ductal pathology at several institutions.
Ultimately, chronic parotitis can be related to salivary stasis, physical obstruction, or reduced salivary flow rates. Common conditions encountered include sialolithiasis, salivary duct strictures or stenosis, juvenile recurrent parotitis (JRP), autoimmune processes such as Sjögren syndrome, and radioiodine-induced sialadenitis. We take some time to review some of these topics, in particular, those that may be amenable to management with sialendoscopy.
Salivary stones are one of the most common nonneoplastic disorders of the salivary glands, and they represent a common cause of acute and chronic sialadenitis in the general population. It is estimated that annually, up to 60 people per million require treatment for acute sialadenitis related to sialolithiasis. Although most commonly encountered in the submandibular gland, they can also be seen with moderate frequency in the parotid gland (20% of the time). Salivary calculi can be made of inorganic substances including calcium carbonate and calcium phosphate. There does not seem to be a predilection for the development of salivary calculi with other systemic diseases, other than gout.
Physical examination may reveal signs associated with generalized parotitis and occasionally, the salivary calculi may be palpable intraorally or overlying the masseter muscle. CT and ultrasonography are good imaging modalities for the assessment of sialolithiasis. CT essentially detects almost all salivary calculi, although if the stones are less than 2 mm, they may be missed. Sialography, including MRI sialography is another imaging modality that can identify obstruction within the parotid duct. At our institution, CT scan of the neck with and without contrast using 1 mm cuts is the standard radiologic study to detect size, location, shape, and orientation of the stone, all of which are relevant to predict success with sialendoscopy. Ultrasonography is extremely valuable when performed by the surgeon because it helps with real-time examination of the stone and assists in localization both in the office and intraoperatively.
Treatment for those patients with sialolithiasis is largely dependent on the size and location of the apparent calculus. Historically, conservative management with sialogogues, warm compresses, and massage may facilitate the spontaneous passage of very small stones (<2 mm). Sialendoscopy has become important for the management of sialolithiasis. For stones that are less than 3 mm in maximal dimension, interventional salivary endoscopy alone can often facilitate complete removal, ( Fig. 2 ). For intermediate size stones, between 3 and 6 mm, endoscopy can be combined with techniques for fragmentation of the calculus. These include utilization of extracorporeal/intraductal lithotripsy ( Fig. 3 ) or the holmium laser ( [CR] ; available online at http://www.oto.theclinics.com/ ) through the working port of the salivary endoscope. Fragmentation of the calculus allows for piecemeal removal of the stone in select cases. Stones that are larger than 8 mm or those that extend far past the hilum may be best approached with combined techniques. These may include diagnostic sialendoscopy for stone localization and external or intraoral approaches for assisted removal. Combined techniques often obviate the need for parotidectomy and have resulted in a gland preservation rate of greater than 90%. There are still some patients who ultimately may require parotidectomy for symptomatic relief.