Chapter 22 Salivation
Pathophysiology and Mechanisms
Excessive salivation is a common clinical finding in patients with disease of the oral cavity, and is usually as a consequence of pain, inflammation, and obstruction (see Chapter 54). Trauma patients, such as those with mandibular fracture, have concurrent disruption in the normal mechanisms of swallowing. Ingested toxins may have both direct noxious effects on saliva production and indirect effects through inflammation of mucosal surfaces. Primary salivary gland disorders (e.g., necrosis, inflammation, cancer) usually provoke an increase in secretion of saliva, although some salivary disorders may be associated with a decrease in saliva production. Neoplasia affecting structures of the oral cavity, oropharynx, and esophagus will interfere with normal swallowing mechanisms resulting in pseudoptyalism. True ptyalism is a common clinical sign with gastrointestinal, metabolic, and systemic disease, and involves activation of humoral and neural pathways for nausea and vomiting (see Chapter 23). Many of the infectious diseases, including viral, bacterial, rickettsial, and protozoal infections, can have direct or indirect effects on saliva production. Central nervous system disorders either increase salivation (e.g., meningitis) or interfere with normal swallowing function (e.g., trigeminal neuropathy).
Differential Diagnosis
The DAMNIT system of disease classification can be used to systematically consider the most important differential diagnoses for ptyalism1–11 and pseudoptyalism:
• D, Degenerative, Drug-Induced, and Developmental—Some drug-induced disorders of ptyalism result from ingestion of unpleasant tasting medications (e.g., metronidazole in cats), whereas others (e.g., erythromycin in dogs) activate the humoral pathway for nausea, salivation, and vomiting. Developmental anomalies such as lip folds and malocclusions will often be accompanied by pseudoptyalism.
• A, Anatomic, Allergic, Autoimmune—Generalized idiopathic megaesophagus and gastric dilation/volvulus syndrome have documented distal effects on normal swallowing function resulting in pseudoptyalism. Some of the autoimmune disorders, such as pemphigus vulgaris, involve the mucous membranes as well as the skin resulting in both true ptyalism and pseudoptyalism.
• M, Metabolic, Mechanical—Any of the metabolic disorders (e.g., renal, hepatic, endocrine) may be accompanied by humoral activation of nausea, salivation, and vomiting. True fever and hyperthermic reactions directly stimulate panting, salivary secretion, and evaporative cooling. Bony fragments and other foreign bodies lodged in the soft palate, oropharynx, and proximal esophagus directly stimulate salivary secretion.
• N, Nutritional, Neoplastic, Neurologic—Incubation of pancreatic enzyme supplements in the food of dogs with exocrine pancreatic insufficiency may induce a severe inflammatory response of the oral cavity and true ptyalism. Cancers of the oral cavity, particularly squamous cell carcinomas in cats, induce true and pseudoptyalism (Fig. 22-1). Central nervous system disorders such as facial paralysis, seizure disorders, vestibular disease, and cranial nerve lesions may interfere with normal swallowing function. An unusual form of phenobarbital-responsive ptyalism has been reported in the dog that has been analogized to limbic epilepsy. Although poorly understood, behavioral responses or reactions may interfere with normal swallowing function (Fig. 22-2).
• I, Inflammatory, Infectious, Immune-Mediated—Caudal stomatitis in cats (see Fig. 22-3) and chronic ulcerative paradental stomatitis in dogs (Figs. 22-4 and 22-5) are important causes of true ptyalism. Severe untreated oral, esophageal, and gastric inflammation may progress to erosion and ulceration inducing both true and pseudoptyalism. Viral infections (e.g., rabies, pseudorabies, calicivirus, and herpes viruses), bacterial infections (e.g., tetanus, botulism, Bordetella), and periodontal disease (Fig. 22-6) may be associated with voluminous aqueous or mixed aqueous-mucoid salivary secretions. Almost any disease of the salivary gland (e.g., sialocele, foreign body, abscessation, trauma, necrosis, neoplasia, hyperplasia, necrotizing sialometaplasia) is associated with moderate to severe true ptyalism.
• T, Traumatic, Toxic—Mandibular and maxillary fractures, temporomandibular joint luxation, and traumatic and electrical injuries stimulate salivary secretion from one or more of the salivary glands. Postmaxillectomy, mandibulectomy, and glossectomy patients (Fig. 22-7) all have predictable true and pseudoptyalism. Excessive salivation will regress with soft tissue and bony healing. Organophosphates, toxic mushrooms, caustic material, and insect bites are all associated with true ptyalism.
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