Alternative Names: Sialolithiasis; submandibular duct stones; parotid duct stones.
Definition: Stone formation in the duct of either the parotid, submandibular, or sublingual glands.
What Is Going on in My Body? There are three major pairs of salivary glands: the parotid glands, submandibular glands, and sublingual glands. The parotid glands are located directly under the skin in front of the ear covering the masseter, which is one of the chewing muscles. The sublingual and submandibular glands are both located just inside the horizontal aspect of the jaw bone. The sublingual glands are toward the front and drain into the mouth under the front of the tongue through numerous small openings. The submandibular glands are located slightly farther behind the sublingual glands, and have a fairly long duct that drains through a small opening under the front of the tongue just adjacent to the mid-line. These are termed the Warthin’s ducts. The parotid glands drain through a separate opening in the cheek just adjacent to the upper second molars. In addition to the three pairs of major salivary glands scattered throughout the mouth and throat are numerous minor salivary glands. These are approximately the size of a lentil bean and drain through individual small channels onto the lining of the mouth. There are literally hundreds of these scattered throughout the mouth and throat. The submandibular gland produce most of the saliva in the mouth, approximately 60%. Because of the anatomy, the submandibular glands actually drain slightly uphill.
Saliva is formed in response to smell and taste stimuli. Its most important function is to provide a healthy environment for the teeth but also to help break down complex starches using an enzyme called amylase. Most stones occur in the setting of either dehydration or sludging of saliva. When the water content of saliva is reduced during acute dehydration, use of diuretics, etc., then calcium and phosphate in the saliva can precipitate and form a stone. Stone formation is much more likely in the submandibular gland. The chemical composition of the stones also varies from one gland to another. Submandibular gland stones tend to have higher concentrations of calcium, which explains why 85% of submandibular stones are visible on x-ray, whereas only 15% of parotid duct stones are visible. Certain disease states associated with thickening of the saliva also predispose to stone formation. There are some disorders where the immune system attacks the salivary glands, thus causing a thicker form of saliva. This would include sicca syndrome, Sjogren’s syndrome, lupus, and other forms of mixed connective tissue disease. In its extreme presentation autoimmune salivary gland disease is associated with significant dental caries and cyst formation and hypertrophy of the salivary glands.
What Are the Signs and Symptoms? Individuals with salivary gland stones that are incompletely obstructive will often notice some discomfort and swelling of the affected saliva gland typically in association with meals. This will be exaggerated with the ingestion of acidic or sour foods, which are greater saliva stimulants than other food types. Often the swelling and discomfort resolve over several hours. The saliva may have a gritty or unusual taste. When the stone is completely obstructive, saliva cannot drain, which then can set the gland up for bacterial infection. If an infection occurs, the gland becomes tense, swollen, very painful, and sore to the touch. If the parotid gland is acutely affected, the swelling is usually in front of and just below the external ear. If it is in the submandibular gland, it is usually under the back part of the jaw. If it is in the sublingual gland, which is quite rare, it will present just behind the chin. Fever is often present during the acute gland infection.
Normally compression of the saliva gland causes a clear, watery, slightly thick saliva to drain from its opening. In the individual with partial obstruction, either no saliva will come out of the opening when pressure is applied to the gland, or what comes out is much thicker than usual and may have strings of yellow to white material in it. Sometimes the stone can be felt or visualized in the duct or duct opening respectively. The individual suffering from an acute infection at the time of diagnosis will have a severely tender, swollen area over the affected gland. When pressure is applied to the gland and its opening observed, infected material may come out.
What Are the Causes and Risks? Any disorder that thickens saliva can predispose to stone formation. These disorders include autoimmune attack of the saliva gland, such as seen with sicca syndrome, Sjogren’s syndrome, lupus, and other autoimmune connective tissue disorders. Drying medications are also frequent causes and include antidepressants, antihistamines, diuretics, etc. Dehydration also plays a prominent role, particularly in older individuals.
How to Prevent the Disease: In the individual suffering from thickened saliva, regardless of its mechanism, adequate hydration using six to eight glasses of water per day and sucking on sour drops will help maintain a good flow of saliva. Salivary stimulants, such as Salagen, can further facilitate saliva flow. Avoiding older-style over-the-counter antihistamines in favor of newer, non-sedating antihistamines may be useful. Choosing antidepressants that have less drying effects may also be preventive. For those who have successfully recovered from a previous stone or who suffer from autoimmune attack on the saliva gland, massaging the gland forward after meals helps clear any thickened, saliva from the gland itself.
How Is It Diagnosed? It is mostly diagnosed on physical examination. Stones can often be felt, particularly in the submandibular glands. Because most submandibular gland stones are identifiable on x-ray, plain x-ray may confirm the presence of a stone. It is much less useful for parotid duct stones. If there is a strong suspicion that a stone exists, yet it cannot be felt, then a sialogram can be obtained. A sialogram is an x-ray study whereby dye is introduced into the salivary gland duct and then an x-ray taken. Stones can be easily visualized with this method.
What Are the Long-Term Effects? The long-term effects are very much determined by whether or not chronic bacterial infection sets into the gland because of the obstruction. Stones that pass spontaneously will create little, if any, difficulty. Should they, however, injure the lining of the duct, then a narrowing of the duct can occur which prevents good salivary flow from the gland, with either induction of additional stone formation or gland infection. Stones can occur in the duct and cause a complete obstruction. If the gland does not become infected, then it may involute and stop making saliva. Sometimes the stone may wear a hole in the duct and extrude into the tissue. In that location it may get walled off or spread the infection into the soft tissue. Should the gland not drain well and not respond to conservative treatment, such as hydration, gland massage, and saliva stimulants, it may become chronically symptomatic. For those individuals who develop a bacterial infection and the gland is incapable of effectively draining, chronic and recurrent bacterial salivary gland infection can result. The longer the infection continues, the more scarring there is in and about the gland and the greater difficulty exists in removing it should it be necessary.
Am I Putting Others at Risk? No.
What Are the Treatments? For small stones, the stone may be squeezed directly out of the duct. For larger stones that cannot completely pass out of the duct opening, a small incision into the duct can help to expel the stone. There have been some reports using shock wave lithotripsy for breakage of saliva gland stones similar to that which is used for kidney stones, but this is a treatment that has not gained wide acceptance. For those individuals who cannot pass their stone and continue to be symptomatic, the only alternative is to remove the gland and the duct which contains the stone.
What Are the Side Effects to the Treatments? Surgical removal of the stone sitting at the duct opening may lead to complete scarring of the duct opening, with subsequent failure of the gland to further drain. This could lead to additional stone formation, infection, and/or gland involution. Should the entire submandibular gland, duct, and the offending stone need to be removed, the complications are related to the adjacent structures. For example, just on the outside surface of the submandibular gland is a small branch of the facial nerve that stimulates lower lip movement. If this nerve is injured, then lower lip paralysis can result. Two other nerves sit underneath the saliva gland. One is the hypoglossal nerve, which controls that side of the tongue. Above the hypoglossal nerve is the lingual nerve, which supplies sensation to the front part of the tongue. If these nerves are injured, there is paralysis and loss of sensation respectively. The main difficulty arising from removal of the parotid gland is injury to the facial nerve. The facial nerve controls the muscles in the face and thus injury to the main trunk of the nerve results in complete facial paralysis. Interruption of specific branches will cause paralysis in that part of the face innervated by that particular nerve branch. Since the damaged glands are usually not very functional, no significant mouth dryness usually results.
What Happens After Treatment? After successful stone removal, if the duct and/or gland has not been injured, then it usually returns to normal. For recurrent acute or chronic infection, gland excision cures the process.
How Do I Monitor the Disease? For those individuals who have intermittent gland swelling or an asymptomatically extruded stone, they can be intermittently followed. However, increase in frequency of eating-related gland swelling and pain or unrelenting progressive gland swelling, pain, or redness necessitate immediate medical consultation.