11.1 Introduction

Inflammatory salivary gland disease represents more than one-third of the salivary gland pathology in childhood. ^{1 , 2} Since salivary gland disorders are infrequently encountered in children, there are relatively few papers in the literature dealing with these problems. In this chapter, we discuss salivary gland inflammatory conditions and salivary gland stones in childhood, their diagnostic methods, and treatment.

11.2 General Anatomical Considerations

By the end of intrauterine life, the salivary glands are well developed and ready to produce saliva at the time of the first breastfeeding. ³ While the anatomy of the salivary glands themselves is similar in children and adults, their topography and shape have some pediatric peculiarities (▶ Fig. 11.1a).

In an embryo, the parotid glands appear first and are the largest salivary glands weighing from 2 to 3 g in neonates to almost 30 g in adolescents. ³ Each parotid gland is located behind the mandibular ramus and in front of the mastoid process of the temporal bone. The parotid duct and Stensen’s duct, is formed from several large interlobular ducts inside the gland. Its orifice can be observed at the parotid papilla, which lies in the vestibule of the mouth between the cheek and the gums. The second superior molar tooth serves as the landmark in older children and adolescents. Moving from the orifice to the gland, the duct passes through the buccinator muscle, takes a steep turn at the border of the masseter muscle, and runs backward along the lateral side of the masseter muscle. In this course, the Stensen’s duct is surrounded by the buccal fat pad. ⁴

This buccal fat is to be taken into account in pediatric cases. This deep anatomic compartment is situated posterior and lateral to the zygomaticus major muscle that exists as multiple lobes or lobules. ⁵ It is responsible for the fullness of the cheeks in infants and young children and aids in cushioning and sucking function. The pad is prominent in neonates and infants and is often referred to as the “sucking pad.” It represents a special type of tissue that is distinct from subcutaneous fat and serves to line the masticatory space, separating the muscles of mastication from each other, from the zygomatic arch, and from the ramus of the mandible. ⁶ The mean diameter of the Stensen’s duct at four different segments along its length ranges between 0.4 and 0.8 mm in young children and between 0.5 and 1.2 mm in adolescents. There is a narrowing at the middle segment of the duct and the minimum width of the secretory duct is at the ostium. Therefore, the diameter of 1 to 1.2 mm should be considered the upper limit for duct endoscopes in case of the Stensen’s duct. A discrete lobe of fat within the buccal space, the inferior lobe of the buccal fat, predicts the location of the parotid duct in infants and young children when the second molar cannot be used for this purpose. ⁷

The Stensen’s duct is located above the inferior lobe of the buccal fat. The facial nerve lies immediately on top of most of these deep fat pads, with the exception of buccal fat. The nerve may actually penetrate buccal fat, as does the duct. However, with proper knowledge of the anatomy of the buccal fat, it can be manipulated with safety. The inferior lobe of the fat is a safe region to manipulate, because the parotid duct travels above this lobe, between the inferior and the middle lobe. Distinguishing the position of this fat pad tells the observer that the Stensen’s duct must be located superior to this location. This is another way to identify the position of the parotid duct in addition to using its course toward the second molar. In children, the drainage of saliva from the parotid glands is lateral from the paired ducts.

The submandibular gland is located in the anterior cervical region in the submandibular triangle, and its duct, the Wharton’s duct, leaves the body of the gland between the mylohyoid, hyoglossus, and genioglossus muscles. The duct opens by a narrow orifice on the summit of a small papilla at the side of the frenulum of the tongue. The tongue of a child is large relatively to the body proportions. When the tongue is elevated, these orifices are quite visible from both sides of the midline of the underside of it. From the orifice, the Wharton’s duct runs into the gland via a gap between the muscles. The main part of the Wharton’s duct is surrounded by gland tissue from the submandibular and partly from the sublingual gland. From the orifice, the duct may run deep into the gland either almost horizontally backward, or in a slightly curved semicircle, or obliquely downward and backward. As a rule, it curves around the mylohyoid muscle. That is why as it proceeds from its entrance in the oral cavity deeper, it curves, and in children the size of the angle of this curve varies between 20 and 170 degrees.

In children, the Wharton’s duct is 1 to 4 cm long, according to the age. Its diameter ranges between 0.4 and 1.2 mm in various segments. ⁸ The narrowest duct diameter is identified at the ostium. The practicality of these facts for the endoscopic intervention is obvious. For diagnostic and therapeutic purposes, sialoendoscopes with stone-extraction baskets or forceps and balloon catheters should conform as much as possible to physiological duct widths. While modern sialoendoscopes may be less than 1 mm in diameter, the diameter of 1.2 mm should be considered the upper limit for duct instruments in pediatric cases. The best results for children 10-year-old and older can be achieved when the maximum size of a stone or a stone fragment does not exceed 1.2 mm.

The pathology of the sublingual glands is extremely rare in children. Usually the sublingual duct, the Bartholin’s duct, joins the submandibular duct to drain through the sublingual caruncle that is a small papilla near the midline of the floor of the mouth on each side of the lingual frenum. But a variation exists when the Bartholin’s duct opens independently near to the orifice of the Wharton’s duct. Congenital anatomic variations of the ductal system of the sublingual glands might be a possible cause of ranulas in patients with simple or plunging ranulas, especially in pediatric patients. ⁹

11.3 Preoperative Evaluation and Anesthesia

11.4 Salivary Imaging

There are a variety of available imaging methods to detect calculi and inflammatory diseases of the salivary glands. In this section we focus on those techniques that are most suitable for children. In general, ultrasonography may be the initial imaging study used for the examination of pediatric salivary gland lesions. Most of them are benign and are well detected with this modality. Ultrasonography may differentiate intraglandular and extraglandular lesions, but additional studies such as color Doppler, computed tomography (CT) scans, cone-beam computed tomography (CBCT), CBCT sialography (if possible), or MRI may be needed as well. ^{10 – 13} The best way to assess a lesion is the sialoendoscopic observation.

11.4.1 Submandibular Gland

In the case of infants, parents are often able to assist the child to allow completion of the image taking (▶ Fig. 11.2a–d).

Sialography

Sialography in children is often impossible and is reserved, if necessary, for selected cooperative patients. In the past, when there were no alternatives, this technique was accomplished in the operating room. The discomfort during sialography may be reduced by applying topical anesthesia to Wharton’s duct papilla and/or by lavaging the gland through the orifice with 2% lidocaine prior to the injection of the water-soluble dye. Sialography provides images of the morphology of the ductal system, and allows the diagnosis of strictures, dilatations, and filling defects. This technique also provides information on glandular function. ^{14 , 15}

Ultrasound

High-resolution ultrasound (above 10 MHz) is a good imaging method to assess the submandibular glands in children. It is noninvasive and there is no associated discomfort. It is useful to distinguish the submandibular gland from surrounding lymph nodes and to locate calculi. The portion of the Wharton’s duct that leads from the hilum of the gland toward the floor of the mouth, precisely after the penetration of the mylohyoid muscle, is difficult to identify. ^{16 , 17}

Computed Tomography

CT scan is especially useful for evaluating inflammatory conditions of the submandibular gland. Sialoliths are readily identified on CT imaging (▶ Fig. 11.2c). The standard images should be 1-mm cuts with three-dimensional (3D) reconstruction. In this way the glands and ducts can be visualized in all planes and stones are less likely to be missed. ¹⁸

11.4.2 Parotid Gland

Most inflammatory conditions of the parotid glands are not a consequence of sialolithiasis. Therefore, the imaging techniques are directed toward documenting changes in the Stensen’s duct morphology and size and changes in the substance of the gland. The most effective imaging methods for the inflammatory parotid conditions in childhood are sialography, ultrasound, and sialoendoscopy.

Sialography

This is an excellent imaging technique to demonstrate changes in the parenchyma (sialectasis), small strictures, and dilatations in the main and secondary ducts. As noted for the submandibular gland, discomfort during the dye injection is a limiting factor. Topical anesthesia and Lidocaine 2% lavage may be used but in young children, the procedure requires general anesthesia (▶ Fig. 11.3).

Ultrasound

Ultrasound is useful to demonstrate parenchymal changes such as sialectasis and morphologic alterations of the parotid duct. The same advantages for ultrasound noted in the submandibular gland apply for the parotid (▶ Fig. 11.4). ^{19 , 20}

The parotid gland and duct can also be imaged by CT.

11.5 The Thallium Scan for All Salivary Glands

While not widely used, this investigation may be helpful in pediatric cases. Intravenously injected thallium, which is concentrated in the functioning salivary gland tissues, is excreted into the mouth with saliva. This can be used to quantify oral secretions aspirated over time. Images of labeled secretions are obtained with a gamma camera. In normal studies, the label is found in the salivary glands and stomach, with low levels in the oral cavity, pharynx, and esophagus. In children who aspirate oral secretions, label is also seen throughout the lung fields. ^{24 – 26}

11.6 Laboratory Data

Laboratory studies are helpful in the diagnosis of viral and bacterial infections as well as noninfectious inflammatory disorders. Complete blood count with differential white blood cell count is helpful in distinguishing viral from bacterial infection. In the former lymphocytosis is often found whereas in the latter leukocytosis. Serum amylase and serum antibody titers are helpful in cases with the acute phase of parotitis. Secretions or drainage from the salivary ducts should be Gram stained and sent for anaerobic and aerobic culture and sensitivity test.

This is especially helpful during the acute stages of sialadenitis. The common aerobic organisms are Streptococci and Staphylococci in immunocompromised systemically ill children. Common anaerobes include: anaerobic gram-negative bacilli (e.g., pigmented Prevotella and Porphyromonas); Fusobacterium spp.; and Peptostreptococcus spp. In addition, Streptococcus spp. (including Streptococcus pneumoniae) and aerobic and facultative Gram-negative bacilli (including Escherichia coli) have been reported. Aerobic and facultative Gram-negative bacilli are often seen in hospitalized patients. Organisms less frequently found are Haemophilus influenzae, Treponema pallidum, Bartonella henselae, and Eikenella corrodens. ^{27 – 29} The parotid gland is the salivary gland most commonly affected by inflammation.

11.7 Sialoendoscopy

The rapid developments in technology in the twenty-first century directed maxillofacial surgeons to develop new methods of treatment by means of noninvasive, minimally invasive, and less invasive interventions. The salivary gland endoscopic and endoscopic assistance techniques, the ductal stretching, and some other intraoral procedures can be applied in pediatric cases as well.

Endoscopes designed for the salivary gland ducts, sialoendoscopes, are produced by various manufacturers (PloyDiagnost GmbH, Germany; Karl Storz, Germany). ^{30 – 32} These sialoendoscopes are divided into diagnostic and therapeutic devices. Not all of them are suitable for pediatric practice, but endoscopes with the exterior diameter of 0.65 to 0.9 mm are suitable for observation and irrigation. Semi-rigid optic specifications vary from 3000 to 30,000 pixels.

We believe that good sialoendoscope should contain a telescope with at least 6000-pixel illumination fibers and focal length of 2 to 15 mm and 70 degree field of view. However the best results can be obtained with the 10,000 pixel optic with 120° field of view. Such microendoscopes can change the view field from 0 to 70 degree and further to 120 degree. The diameter of the telescope is usually 0.5 to 0.9 mm. The endoscopes can be either designed with the fixed exterior diameter or have disposable sleeves of various diameters (PloyDiagnost GmbH, Germany) (▶ Fig. 11.5a, b).

Endoscopes with the exterior diameter of 0.9 to 1.2 mm can be used for older children and adolescents. The useful tools are grasping forceps, basket, grasper, and balloon-like Fogarty or Sialoballoon catheter (AD-TECH-MED Ltd Lublin, Poland), biopsy forceps intracorporeal electrohydraulic lithotripter probes, and Er-YAG and Holmium-YAG laser probes. It is best to work under direct vision, but occasionally in children, it is necessary to work in a semiblind manner because of size constraints of the duct. In this case, the obstruction is identified with the endoscope and then the telescope is removed to make room for the working instrument. ^{8 , 33 , 34}

11.8 Pediatric Anesthesia

In children, the endoscopic salivary gland procedure is done under general anesthesia. It should be remembered that infants have poor respiratory reserves, and respiratory failure is a common sequel to pathology in any other system. Elective surgery should not take place when the patient has an acute intercurrent illness. The sialoendoscopy should be deferred about a month after the last symptoms of respiratory tract infection, croup, or the acute exanthems have subsided, as related adverse events can occur for up to several weeks. Specialized apparatus with low resistance to breathing (less than 30 cmH₂O/L per second during quiet breathing) and minimal dead space is necessary for infants. Older children and adolescents are significantly less fragile in this matter.

11.9 Differential Diagnostics with Rare Nonsurgical Conditions

Although rare, the following specific conditions may cause salivary gland infection and swelling or mimic infection in children: pneomoparotid, atypical mycobacteria, tuberculosis, actinomycosis, and acquired immunodeficiency syndrome (AIDS). Such disorders do not require surgical intervention but endoscopic observation and the above-mentioned sialoendoscopy may be used for differential diagnostic purposes in complicated cases.

Pneumoparotid is a rare condition of the parotid gland in which it is inflated with air as a result of positive air pressure inside the mouth (up to 150 mm Hg). Physical examination reveals parotid enlargement, usually unilateral but also bilateral. Palpation of the affected gland produces crepitus. ^{35 , 36} The best imaging technique is CT scan, which will show air in the parotid gland, Stensen’s duct, and occasionally in the surrounding tissue. ³⁷ In childhood most of the cases are self-induced but a few are accidental, e.g., blowing up a balloon, aggressive blowing of the nose, inflating a bicycle tire inner tube without a pump, or inveterate gum chewing.

Atypical mycobacteria infections have been identified as an important cause of infection in the head and neck in children. ³⁸ The parotid and submandibular gland can be affected as can the neighboring lymph nodes. The clinical appearance is swelling of the affected gland and sometimes-spontaneous drainage. Diagnosis relies upon culture, histology, chest radiography, and purified protein derivative (PPD).

Tuberculosis of the salivary gland in children can develop primarily or secondary to pulmonary tuberculosis. ^{39 , 40} The parotid gland is affected more than the submandibular gland and the clinical picture is a firm swelling sometimes with draining fistula. Diagnostic tests of suspected cases include chest X-ray, (PPD) skin test, and acid fast staining from drainage material and from tissue. It should be remembered that calcification of lymph nodes and sometimes salivary tissue can be identified in tuberculosis and can mimic sialoliths.

Actinomycotic infections can affect the salivary glands, with 10% of actinomycosis orofacial cases being in the salivary glands. ³⁹ The infection can be acute or chronic and in most of the cases the only method to distinguish this specific infection from other forms of sialadenitis is culture.

Speaking of AIDS, children infected with human immunodeficiency virus (HIV) develop salivary gland enlargement in 18% of cases. ^{41 , 42} Parotid gland enlargement is typically an early manifestation in the HIV-positive patient and should alert healthcare professionals to the likelihood of HIV infection. ⁴¹ Fine needle aspiration cytology investigation (FNAC) of the parotid gland is required to confirm the diagnosis. The surgical operation may be required in cases when the parotid enlargement results from benign lymphoepithelial cysts. ⁴³ The prognosis of children with salivary gland enlargement is poor only 5.4 years.