A Salivation Abnormality with Trigeminal Nerve Dysfunction in Dogs

Abstract

Trigeminal nerve pathology can lead to sensory and motor dysfunction to structures of the head that are easily recognized. The trigeminal nerve is a conduit for the distribution of postganglionic parasympathetic innervation to structures of the head. Parasympathetic innervation to the salivary glands is provided by preganglionic parasympathetic neurons of the facial and glossopharyngeal nerves. Postganglionic axons course with branches of the mandibular branch of the trigeminal nerve to reach the salivary glands. Denervation of the salivary glands impacts glandular function, leading to a reduction in the volume and composition of the saliva produced. Saliva plays an important role in oral health. Poor oral health has widespread systemic implications. This article describes a group of dogs with unilateral or bilateral dysfunction of the trigeminal nerve and/or its branches. In all dogs, an accumulation of thick, foamy saliva was observed accumulating in the dorsal aspect of the caudal oral cavity on the ipsilateral side to the affected nerve. In dogs with magnetic resonance imaging (MRI), there was a reduction in size based on the largest crosssectional area measurement and an increase in mean signal intensity of the salivary glands ipsilateral to the affected nerves compared to the glands on the normal side. The authors hypothesize that the abnormal saliva and MRI changes observed were consequent to parasympathetic denervation of the salivary glands. The recognition of this clinical observation is the first step in understanding the impact that denervation has on salivation and ultimately on overall oral and systemic health in dogs.

The Anatomy of the Stomatognathic System in Different Skull Types in Dogs

“…Other cranial nerves of the stomatognathic system were the facial (CN VII), glossopharyngeal (CN IX), vagus (CN X), and hypoglossal (CN XII) nerves. 14,29 Alterations of the peripheral innervation of the head can also be due to neural dysfunctions and tumors originating from the neuronal fibers themselves, 30,31 and this knowledge is essential for local anesthesia in the head. [20][21][22][32][33][34][35] Healing of the oral mucosa is faster than that of the skin due to several factors, including a more abundant blood supply.…”

“…It has been previously stated, 14 that “understanding the anatomy of the nervous system of the head is relatively simple since the trigeminal nerve, the fifth cranial nerve, (CN V) is mainly responsible for the sensory function of the face (except for the tongue) and is the primary motor nerve of the masticatory muscles.” Other cranial nerves of the stomatognathic system were the facial (CN VII), glossopharyngeal (CN IX), vagus (CN X), and hypoglossal (CN XII) nerves. 14,29 Alterations of the peripheral innervation of the head can also be due to neural dysfunctions and tumors originating from the neuronal fibers themselves, 30,31 and this knowledge is essential for local anesthesia in the head. 20‐22,32‐35…”

Progress in salivary glands: Endocrine glands with immune functions

“…Chronic denervation of the trigeminal nerve is linked to atrophy, and increased fatty tissue in the dog PG has been reported, trigeminal dysfunction results in accumulation of abnormal saliva and decreased weight and size of the ipsilateral SG. Denervation and loss of the masticatory-salivary reflex is one of the reasons for the atrophy of SGs (109).…”