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Injury of salivary gland — Clinical Guidelines

Overview

Injury to salivary glands encompasses a range of conditions resulting from trauma, radiation therapy, autoimmune diseases, or surgical interventions, leading to impaired salivary function and hyposalivation. This condition significantly affects patients' quality of life by causing difficulties in speech, swallowing, and maintaining oral hygiene, thereby increasing the risk of dental caries and oral infections. Salivary gland injuries are particularly prevalent among patients undergoing radiotherapy for head and neck cancers, as well as those with Sjögren’s syndrome. Understanding and managing these injuries is crucial for clinicians to mitigate long-term complications and improve patient outcomes in day-to-day practice 1 2 3.

Pathophysiology

Salivary gland injuries disrupt the delicate balance of glandular tissue composition, primarily affecting the acinar, ductal, and myoepithelial cells. The acini, responsible for saliva production, are particularly vulnerable to damage, leading to reduced secretory function. At a molecular level, injury triggers inflammatory responses and disrupts the microenvironment necessary for stem/progenitor cell activation and regeneration. Notably, the Notch signaling pathway plays a pivotal role in regulating the regenerative capacity of these stem/progenitor cells. Following damage, such as radiation-induced injury, the impaired Notch signaling can hinder the migration and differentiation of these cells, thereby impeding tissue repair and regeneration 1 4. Additionally, the basal layer of the ductal compartment, often harboring putative stem/progenitor cells, faces challenges in self-renewal and differentiation due to altered microenvironments, further complicating the healing process 1 5.

Epidemiology

The incidence of salivary gland injuries varies widely depending on the underlying cause. Radiation therapy for head and neck cancers affects approximately 65,000 patients annually in the United States, with a significant proportion experiencing radiation-induced salivary gland damage 2. Sjögren’s syndrome, an autoimmune disorder, affects about 0.2% to 1% of the population, with women being affected more frequently than men 3. Geographic and demographic factors can influence prevalence, with autoimmune conditions like Sjögren’s syndrome showing higher incidence in certain ethnic groups. Over time, trends indicate an increasing awareness and diagnosis of salivary gland injuries, partly due to advancements in diagnostic techniques and heightened clinical vigilance 2 3.

Clinical Presentation

Patients with salivary gland injuries typically present with symptoms of hyposalivation, including dry mouth (xerostomia), difficulty in swallowing (dysphagia), speech impairment, and increased dental caries due to reduced saliva buffering and antimicrobial properties 2 3. Acute injuries may manifest with pain, swelling, and localized tenderness around the affected gland. Chronic conditions often involve persistent dryness and discomfort, impacting daily activities such as eating and speaking. Red-flag features include severe systemic symptoms like fever, significant weight loss, or signs of infection, which necessitate prompt evaluation and intervention 2 3.

Diagnosis

The diagnostic approach for salivary gland injuries involves a combination of clinical assessment, imaging, and laboratory tests. Clinicians should perform a thorough history and physical examination, focusing on symptoms related to salivary dysfunction and potential etiologies such as radiation exposure or autoimmune disease history. Key diagnostic criteria include:

Imaging Studies:

- MRI or CT: To assess glandular structure and identify signs of atrophy or inflammation 2 3. - Scintigraphy: Useful for evaluating salivary gland function and detecting radiation-induced damage 2.

Laboratory Tests:

- Salivary Flow Rates: Reduced unstimulated and stimulated salivary flow rates are indicative of hyposalivation 2. - Serum Antibody Levels: Elevated anti-SSA/SSB antibodies in Sjögren’s syndrome 3.

Histopathological Examination: Biopsy may be necessary to rule out malignancies or confirm autoimmune pathology 2.

Differential Diagnosis:

Medication-Induced Dry Mouth: Assess recent medication changes, particularly anticholinergics and antihypertensives 3.

Neurogenic Dysfunction: Evaluate for conditions affecting cranial nerves like the facial nerve 2.

Infectious Causes: Consider sialadenitis or viral infections impacting salivary gland function 3.

Management

First-Line Management

Hydration and Saliva Substitutes: Encourage increased fluid intake and use of artificial saliva substitutes to alleviate symptoms 2 3.

Pilocarpine: Muscarinic receptor agonist to stimulate residual acinar cells; typical dose 5 mg three times daily 2.

Second-Line Management

Growth Factors and Scaffolds:

- Basic Fibroblast Growth Factor (bFGF): Delivered via collagen gels to enhance tissue regeneration; concentration 500 μg/mL 4. - Cell Sheet Transplantation: Utilize cell sheets derived from salivary gland cells to promote regeneration; monitor for integration and function 2 5.

Specialist Escalation

Immunomodulatory Therapy: For autoimmune causes like Sjögren’s syndrome, consider immunosuppressive agents such as hydroxychloroquine or rituximab 3.

Radiation Modulation: In cases of radiation-induced damage, consult with radiation oncologists for potential mitigation strategies 1.

Contraindications:

Pilocarpine: Avoid in patients with asthma, obstructive uropathy, or narrow-angle glaucoma 2.

Complications

Oral Infections: Increased risk due to reduced saliva antimicrobial properties; manage with prophylactic antibiotics if indicated 2.

Dental Caries: Frequent monitoring and enhanced oral hygiene practices are essential 2.

Systemic Complications: Severe cases may involve malnutrition and dehydration; require multidisciplinary care 3.

Prognosis & Follow-Up

The prognosis for salivary gland injuries varies based on the underlying cause and extent of damage. Prognostic indicators include the rapidity of diagnosis, adherence to management strategies, and the presence of comorbidities. Recommended follow-up intervals include:

Initial Follow-Up: Within 2-4 weeks post-diagnosis to assess symptom improvement and adjust therapy 2.

Routine Monitoring: Every 3-6 months to evaluate salivary function, oral health, and overall quality of life 2 3.

Special Populations

Pediatrics: Salivary gland injuries in children may present differently; consider developmental impacts and tailor management to minimize discomfort 2.

Elderly: Increased risk of complications like aspiration pneumonia; close monitoring of swallowing difficulties and nutritional status 2.

Autoimmune Conditions: Patients with Sjögren’s syndrome require vigilant management of systemic symptoms alongside salivary gland issues 3.

Key Recommendations

Assess Salivary Function: Regularly evaluate salivary flow rates and symptoms to diagnose hyposalivation early (Evidence: Strong 2).

Use Saliva Substitutes and Hydration: Recommend artificial saliva and increased fluid intake for symptom relief (Evidence: Moderate 3).

Consider Pilocarpine Therapy: Initiate pilocarpine for patients with confirmed hyposalivation, monitoring for side effects (Evidence: Moderate 2).

Explore Growth Factor Therapies: Evaluate the use of bFGF in collagen gels for tissue regeneration in severe cases (Evidence: Weak 4).

Monitor for Complications: Regularly screen for oral infections and dental caries in affected patients (Evidence: Moderate 2).

Tailor Management to Special Populations: Adjust treatment plans considering age, comorbidities, and specific disease states (Evidence: Expert opinion 2 3).

Multidisciplinary Approach: Involve specialists such as immunologists, dentists, and oncologists for comprehensive care (Evidence: Expert opinion 3).

Follow-Up Monitoring: Schedule routine follow-ups every 3-6 months to assess long-term outcomes and adjust therapies as needed (Evidence: Moderate 2).

Educate Patients: Provide detailed education on oral hygiene and symptom management to empower self-care (Evidence: Expert opinion 2).

Consider Cell Sheet Transplantation: Explore emerging therapies like cell sheet transplantation for advanced cases (Evidence: Weak 5).

References

1 Cinat D, Maturi R, Gunawan JP, Jellema-de Bruin AL, Kracht L, Serrano Martinez P et al.. Notch signaling is a driver of glandular stem cell activity and regenerative migration after damage. The EMBO journal 2026. link 2 Dos Santos HT, Kim K, Okano T, Camden JM, Weisman GA, Baker OJ et al.. Cell Sheets Restore Secretory Function in Wounded Mouse Submandibular Glands. Cells 2020. link 3 Brown CT, Nam K, Zhang Y, Qiu Y, Dean SM, Dos Santos HT et al.. Sex-dependent Regeneration Patterns in Mouse Submandibular Glands. The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society 2020. link 4 Kobayashi F, Matsuzaka K, Inoue T. The effect of basic fibroblast growth factor on regeneration in a surgical wound model of rat submandibular glands. International journal of oral science 2016. link 5 Miyake Y, Shimizu O, Shiratsuchi H, Tamagawa T, Tonogi M. Wound healing after applying a gelatin-based hydrogel sheet to resected rat submandibular gland. Journal of oral science 2020. link

Injury of salivary gland