Diagnosis and Management of Salivary Gland Disorders PDF

21 Diagnosis and Management of Salivary Gland Disorders MICHAEL MILORO AND ANTONIA KOLOKYTHAS acute and chronic salivary gland infections, traumatic salivary gland CHAPTER OUTLINE...

21 Diagnosis and Management of Salivary Gland Disorders MICHAEL MILORO AND ANTONIA KOLOKYTHAS acute and chronic salivary gland infections, traumatic salivary gland CHAPTER OUTLINE disorders, Sjögren syndrome, necrotizing sialometaplasia, and benign Embryology, Anatomy, and Physiology, 423 and malignant salivary gland tumors. Diagnostic Modalities, 427 History and Clinical Examination, 427 Embryology, Anatomy, and Physiology Salivary Gland Radiology, 428 The salivary glands are divided into two groups: (1) the major Plain-Film Radiographs, 428 glands and (2) the minor glands. All salivary glands develop from Sialography, 428 the embryonic oral cavity as buds of epithelium that extend into Computed Tomography, Magnetic Resonance Imaging, the underlying mesenchymal tissues. These epithelial ingrowths, Ultrasonography, and Positron Emission Tomography, 430 or anlages, are apparent anatomically at 8 weeks’ gestation (Fig. Salivary Scintigraphy (Radioactive Isotope Scanning), 432 21.1) and then branch to form a primitive ductal system that Salivary Gland Endoscopy (Sialoendoscopy), 434 eventually becomes canalized to provide the basic salivary gland Sialochemistry, 434 unit for the production and drainage of salivary secretions (Fig. Fine-Needle Aspiration Biopsy, 434 21.2). This unit consists of an acinus (or secretory unit), which is Salivary Gland Biopsy, 435 a cluster of cells including myoepithelial cells and acinar (secretory) Obstructive Salivary Gland Disease: Sialolithiasis, 435 cells with secretory granules that coalesce into the collecting ducts Mucous Retention and Extravasation Phenomena, 439 that include the intercalated duct, followed by the striated duct, Mucocele, 439 and finally the excretory duct; each ductal unit consists of unique Ranula, 440 acinar cells with branching ducts. The minor salivary glands begin to develop around the fortieth day in utero, whereas the larger Salivary Gland Infections, 440 major glands begin to develop slightly earlier, at about the thirty-fifth Necrotizing Sialometaplasia, 443 day in utero. At around the seventh or eighth month in utero, Sjögren Syndrome, 443 secretory cells called acini begin to develop around the ductal Traumatic Salivary Gland Injuries, 444 system. The acinar cells of the salivary glands are classified either Salivary Gland Neoplasms, 445 as serous cells, which produce a thin, watery serous secretion, or Benign Salivary Gland Tumors, 445 mucous cells, which produce a thicker, more viscous mucous secre- Malignant Salivary Gland Tumors, 446 tion. The minor salivary glands are well developed and functional in the newborn infant. The acini of the minor salivary glands produce primarily mucous secretions, although some are composed of serous cells as well; this results in the classification of these minor glands as mixed. Between 800 and 1000 minor salivary A s experts in the oral and maxillofacial region, the practic- glands are present throughout the portions of the oral cavity that ing dentist and dental specialist may be required to are covered by mucous membranes, with a few exceptions, such perform the necessary assessment, diagnosis, and manage- as the anterior third of the hard palate, the attached gingiva, and ment of a variety of salivary gland disorders ranging from minor, the dorsal surface of the anterior third of the tongue. The well- self-limiting disease processes to more significant disorders of the established locations of the minor salivary glands are referred to major and minor salivary glands; thus a thorough practical knowl- as labial, buccal, palatine, tonsillar (Weber glands), retromolar edge of the incidence, demographics, embryology, anatomy, and (Carmalt glands), and lingual glands. The lingual glands are divided pathophysiology is necessary to manage these patients in the most into three groups of glands: (1) inferior apical glands (of Blandin appropriate manner. This chapter reviews the anatomy and physiol- and Nuhn), (2) taste buds (Ebner glands), and (3) posterior lubricating ogy of salivary glands, as well as the etiologies, diagnostic methods, glands (Table 21.1). contemporary radiographic evaluation, and medical and surgical The major salivary glands are paired structures and include the management of a variety of salivary gland disorders, including parotid, submandibular, and sublingual glands. The parotid glands sialolithiasis and obstructive phenomena (e.g., mucocele and ranula), contain primarily serous acini with few mucous cells. Serous cells 423 Downloaded for Anonymous User (n/a) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on July 24, 2020. For personal use only. No other uses without permission. Copyright ©2020. Elsevier Inc. All rights reserved. 424 Pa rt I V Infections are cuboidal cells with eosinophilic secretory granules and produce thin, watery secretions with a low viscosity (1.5 Pa s). Conversely, the sublingual glands are, for the most part, composed of mucous cells, which are clear low columnar cells with nuclei polarized away from the lumen of the acini, and produce a thick secretion with high viscosity (13.4 Pa s). The submandibular glands are mixed glands, made up of approximately equal numbers of serous and mucous acini and thus produce a secretion with an intermediate viscosity of 3.4 Pa s. The parotid glands, the largest salivary glands, lie superficial to the posterior aspect of the masseter muscles and the ascending vity Parotid ca rami of the mandible, in an “inverted triangular” shape below the al anlage Or zygomatic arch. Peripheral portions of the parotid glands may extend to the mastoid process, along the anterior aspect of the sternocleidomastoid muscle, and around the posterior border of Sublingual the mandible into the pterygomandibular space (Fig. 21.3). The anlage major branches of the seventh cranial (facial, VII) nerve roughly Submandibular divide the parotid gland into a superficial lobe and a deep lobe anlage and course anteriorly from the exit of the nerve from the stylo- mastoid foramen to innervate the muscles of facial expression. 8 weeks Later stage Since the parotid gland contains the terminal branches of the facial Fig. 21.1 Embryologic development of the major salivary glands. nerve, this may explain why a mandibular block local anesthetic injection may result in transient facial paralysis if the anesthetic solution is deposited into the parotid gland as it extends around the posterior border of the mandible into the pterygomandibular Acinus space. Small ducts from various regions of the parotid gland coalesce Striated Excretory Intercalated duct duct at the anterosuperior aspect of the parotid gland to form the Stensen duct duct, which is the major duct of the parotid gland. The Stensen duct is about 1 to 3 mm in diameter and 6 cm in length. Occasion- ally a normal anatomic variation occurs in which an accessory parotid duct may aid the Stensen duct in the drainage of salivary secretions. In addition, an accessory portion of the parotid gland may be present anywhere along the course of the Stensen duct. The duct traverses anteriorly from the parotid gland hilum and courses in a position superficial to the masseter muscle. At the location of the anterior edge of the masseter muscle, the Stensen Myoepithelial cell duct turns sharply in a medial direction and pierces through the Fig. 21.2 Basic salivary gland unit. fibers of the buccinator muscle. The Stensen duct opens into the oral cavity through the buccal mucosa as a punctum in the maxillary posterior buccal vestibule, usually adjacent to the maxillary first or second molar. The parotid gland receives neural innervation TABLE 21.1 Salivary Gland Embryology and Anatomy from the ninth cranial (glossopharyngeal) nerve via the auriculo- temporal nerve from the otic ganglion (see Fig. 21.7). Major Salivary The submandibular glands are located in the “submandibular Minor Salivary Glands Glands triangle” of the neck, which is a triangle formed by (1) the anterior In utero Day 40 Day 35 belly of the digastric muscle, (2) the posterior belly of the digastric development muscle, and (3) the inferior border of the mandible (Fig. 21.4). The posterosuperior portion of the gland curves upward around Number of 800–1000 minor glands 6 (3 paired glands) glands and above the posterior border of the mylohyoid muscle and gives rise at the hilum to the major duct of the submandibular gland Types of glands Labial Parotid known as the Wharton duct. This duct passes forward along the Buccal Submandibular superior surface of the mylohyoid muscle in the sublingual space, Palatine Sublingual adjacent to the lingual nerve. The anatomic relationship in this Tonsillar (Weber glands) area is such that the lingual nerve loops under the Wharton duct, Retromolar (Carmalt glands) Lingual from lateral to medial, in the posterior floor of the mouth; the 1. Inferior apical glands (of lingual nerve then branches to provide sensory input to the anterior Blandin and Nuhn) two-thirds of the tongue on each side of the tongue. Of course 2. Taste buds (Ebner the glossopharyngeal nerve provides sensation to the posterior glands) one-third of each side of the tongue, and the chorda tympani 3. Posterior lubricating branch of the facial nerve provides taste sensation to the anterior glands two-thirds of the tongue. The Wharton duct continues forward in a straight line, and the lingual nerve traverses under the duct Downloaded for Anonymous User (n/a) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on July 24, 2020. For personal use only. No other uses without permission. Copyright ©2020. Elsevier Inc. All rights reserved.  CHAPTER 21 Diagnosis and Management of Salivary Gland Disorders 425 Parotid salivary gland Stensen duct Buccinator muscle Masseter muscle Facial nerve Fig. 21.3Parotid gland anatomy. The facial nerve branches divide the gland into superficial and deep lobes. The Stensen duct courses superficial to the masseter muscle then curves sharply to pierce the buccinator muscle and enter the oral cavity. Submandibular duct Submandibular salivary gland (deep lobe) Mylohyoid muscle Anterior belly of digastric muscle Submandibular salivary gland (superficial lobe) Posterior belly of digastric muscle Fig. 21.4 Submandibular gland anatomy. The submandibular triangle is formed by the anterior and posterior bellies of the digastric muscles and inferior border of the mandible. A portion of the gland may extend above the mylohyoid muscle. The Wharton duct courses superiorly and anteriorly to exit in the anterior floor of the mouth. from a lateral position (beginning in the pterygomandibular space 5 cm in length, and the duct lumen is 2 to 4 mm in diameter. after separating from the inferior alveolar nerve) to a medial position. The Wharton duct opens into the floor of the mouth via a muscular In a medial position, the Wharton duct is vulnerable to injury in punctum located close to the mandibular incisors at the most the third molar region during third molar extraction surgery because anterior aspect of the junction of the lingual frenum and the floor it lies in a position close to the medial surface of the internal of the mouth. The punctum is a constricted portion of the duct, oblique ridge of the posterior mandible. Subsequently, as mentioned, and it functions to limit retrograde flow of bacteria-laden oral the nerve turns in a medial direction to branch extensively into fluids into the ductal system. This is particularly important since the tongue musculature bilaterally. The Wharton duct is about this punctum limits retrograde entry of those bacteria that tend Downloaded for Anonymous User (n/a) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on July 24, 2020. For personal use only. No other uses without permission. Copyright ©2020. Elsevier Inc. All rights reserved. 426 Pa rt I V Infections Ducts of Rivinus Lingual nerve Branches to tongue Mylohyoid nerve Wharton Submandibular ganglion duct Submandibular salivary gland Sublingual salivary gland Mylohoid muscle Fig. 21.5 Sublingual gland anatomy. Note the relationship of the Wharton duct and the lingual nerve. TABLE 21.2 Composition of Normal Adult Saliva TABLE 21.3 Daily Saliva Production by Salivary Gland Parotid Gland Submandibular Gland Gland Production Amino acids 1.5 mg/dL