Introduction
Sjögren syndrome (SS) is a chronic autoimmune disorder characterized by inflammatory destruction of the body’s exocrine glands and may be considered primary or secondary, in association with other autoimmune disorders, such as collagen vascular diseases. Although SS can present with a variety of symptoms, both glandular and extraglandular, initial presenting symptoms most commonly include decreased secretions of the major and minor salivary glands, leading to dry mouth and dry eyes, or sicca syndrome. In particular, involvement of the parotid glands can present as recurrent and tender swelling. Salivary gland dysfunction in SS reduces acinar cell production of serous saliva. This leads to mucous plugs within the salivary gland, resulting in obstructive sialoadenitis and possible superimposed inflammation. Furthermore, the insidious autoimmune process confers an increased risk for lymphoma. Both computed tomography (CT) and magnetic resonance imaging (MRI) are suitable options for evaluating the affected parotid glands, and sialography can be also performed to further evaluate the salivary ducts.
Temporal Evolution: Overview
SS leads to a fairly characteristic progression of changes in the parotid glands ( Fig. 41.1 ). Initially, the parotid glands in SS may appear normal on imaging. Eventually, a classic miliary pattern of tiny cysts forms within the glands bilaterally, which appears as punctate foci of hypoattenuation on CT and high signal on T2-weighted MRI. The glands tend to become swollen diffusely from inflammation, although they may be asymmetric. Punctate calcifications may also form within the parotid glands, which is a classic feature of intermediate to late stages of SS and are best depicted on CT ( Fig. 41.2 ). In addition, as parenchymal injury progresses, some of the cysts may enlarge and lymphoid aggregates may form solid nodules. Ultimately, the gland atrophies with fibrosis and fat deposition, which imparts a heterogeneous appearance on imaging ( Fig. 41.3 ). The strictures that form in the salivary ducts can be depicted via sialography and may have a string of beads appearance ( Fig. 41.4 ).
Given the autoimmune nature of SS, patients are at risk for certain lymphomas, particularly non-Hodgkin lymphoma (NHL) of the head and neck, with a 7- to 19-fold higher incidence than the general population. Consequently, patients with SS should be followed up with adequate imaging of the parotid gland to detect NHL early on, especially those who present with persistent parotid swelling. The development of a solid nodule accompanied by cervical lymphadenopathy and enlargement of the Waldeyer ring tissues on imaging raises concern for lymphoma ( Fig. 41.5 ).
