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J Am Dent Assoc, Vol 131, No 4, 479-482. © 2000 American Dental Association

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by MANDEL, L. Articles by HATZIS, G. Search for Related Content PubMed PubMed Citation Articles by MANDEL, L. Articles by HATZIS, G. Related Collections Restoratives

AND THERAPY OF PAROTID STONES: A CASE REPORT

	ABSTRACT

TOP ABSTRACT SYMPTOMATOLOGY IMAGING CASE REPORT DISCUSSION CONCLUSION REFERENCES

 
Background. Small, semicalcified parotid stones are difficult to diagnose as imaging can be extremely difficult. Understanding how to diagnose parotid stones is important to dentists, however, because people with this condition develop parotid swellings and may seek routine dental care.

Case Description. The authors describe a classic case of parotid sialadenitis secondary to a small lucent stone in Stensen’s duct. They discovered the stone only because of the keen sensitivity of computerized tomography, or CT, to minimal amounts of calcific salts. The CT scan’s ability to accurately locate the stone and its position within 1 centimeter of the orifice facilitated a successful intraoral surgical approach.

Clinical Implications. CT can be a significant aid in early diagnosis and therapy of patients with parotid stones, who eventually develop sialadenitis. With early intervention, further gland degeneration and parotidectomy will be prevented.

Sialolithiasis—calculi or concretions in a salivary duct—represents a relatively common glandular entity seen in the dental office, occurring in 12 of every 1,000 patients.¹ Although submandibular salivary gland involvement is more frequent (80–90 percent) than the parotid gland involvement (10–20 percent),^2–4 parotid sialolithiasis presents more perplexing and unusual challenges in relation to diagnosis and therapy.

A failure to diagnose and treat these parotid stones early in the course of sialolithiasis leads to an inevitable progression of the pathology. Gland degeneration and gland removal, with serious consequences, can be anticipated if treatment is delayed.

Dental practitioners have the opportunity to play a key role in the interdiction of the disease’s downward spiral. To do so, however, the general practitioner must become familiar with the etiology, symptomatology, diagnostic techniques and treatment of parotid stones.

Stensen’s (parotid) duct is approximately 5 centimeters in length⁵ and follows a slightly uphill course as it exits from the gland on its path toward its intraoral orifice. The duct traverses the lateral surface of the masseter. At the muscle’s anterior border, it makes a right angle bend, perforates the buccinator muscle and exits on the buccal mucosa adjacent to the maxillary second molar.

Salivary flow functions as the duct’s cleansing mechanism. Decreased salivary production or a failure to deliver the saliva—an obstruction—sets the stage for the development of a sialolith.^4,6 Inadequate lavage can facilitate an ascending bacterial invasion from the oral cavity. Bacteria, desquamated epithelium, a foreign body or increased quantities of high-molecular-weight serum proteins escaping from an infected and permeable duct wall and forming a mucous plug can all serve as a nidus that obstructs salivary flow. Stasis with chemical precipitation of calcium salts into the nidus results.⁷

	SYMPTOMATOLOGY

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Parotid duct stones can form at any age, but their peak incidence occurs when people are in their 30s and 40s. Most are located within the extraglandular portion of Stensen’s duct. Few are in the intraglandular duct system.⁸

Parotid duct stones usually are small in size compared with submandibular gland stones and are singular. Regardless of size, obstructive symptomatology can be expected. Parotid swellings with discomfort, for example, occur during meals because the increased salivary volume produced during meals meets the obstruction caused by the sialolith. Saliva backs up as a result and parotid swelling and pain occur. Since the stone rarely totally blocks the duct’s lumen, the retained saliva seeps past the stone, and gland swelling and discomfort subside once the patient has stopped eating. At this stage, the prerequisites for infectious incursions—obstruction and stagnation—have been laid, and recurrent parotid swellings can be expected.

Unilateral parotitis eventually develops, and a more permanent diffuse firm swelling eventually replaces the episodic gland enlargements. Pain, fever and a moderate trismus develop. Suppuration ensues indicating infection. When the parotid is massaged manually and milked by extraoral pressure, pus will be observed intraorally exiting from the duct’s orifice.

	IMAGING

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A definitive diagnosis of a parotid stone necessitates imaging. Difficulties with substantiation of a stone’s presence are encountered for a variety of reasons. Parotid stones often are not detected because they tend to be small and not well-calcified.^6,9,10 Furthermore, surrounding anatomical structures obscure less-calcified stones when they are superimposed on well-calcified bone. Visualization via standard radiologic techniques may fail.

Successful radiologic visualization of a stone in the anterior segment of the duct often can be attained by placing a periapical film intraorally against the buccal soft tissues adjacent and posterior to the duct’s orifice. Puffing the cheek out for a posteroanterior radiograph also may prove successful because it displaces the duct away from the ramus. A small, semicalcified stone, however, can evade detection using these techniques.

Parotid stones lucent to standard radiography contain a minimum of calcific deposits that can be successfully imaged with the highly sensitive computerized tomographic scan.

Ultrasonography has been used to locate a stone,^7,11–15 but its failure to detect small semi-calcified stones is not uncommon.^16–18

Sialography is another method for detecting parotid stones. Many opaque or lucent parotid stones can be diagnosed by a filling defect that marks their location. In addition, a stone’s position can be determined by its pathological effect on the immediately adjacent portion of the proximal duct. However, small stones—calcified or not—will usually be obliterated by the opaque dye used in sialography. Furthermore, sialography is contraindicated during acutely infectious manifestations of parotid swelling.

Computerized tomography, or CT, scanning avoids the pitfalls of the standard imaging techniques for parotid stones.^7,12,17 A significant advantage of the CT scan is its sensitivity to calcific deposits. Even stones lucent to standard radiography contain a minimum of calcific deposits that can be successfully imaged with the highly sensitive CT scan. On the CT scan, the extent of the parotid sialadenitis, secondary to the stone, will be noted as areas of increased density, while areas of decreased density reflect the existence of an abscess.

	CASE REPORT

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A 36-year-old man in good health came to the Salivary Gland Center, Columbia University School of Dental and Oral Surgery in New York City. His complaint concerned two episodes of painful left parotid swelling associated with eating. Eight months previous, the first episode of painful swelling occurred and then subsided after a few days. Ten days before the visit, however, it had returned during meals. This time the swelling had not subsided and had gotten larger and more painful at meals.

A mild left parotid swelling was evident extraorally. Palpation of the gland indicated that it was firm and tender. We noted a moderate trismus but no cervical lymphadenopathy.

Intraorally, the mucosa was moist. Aggressive and painful milking of the left parotid caused the delivery of a small amount of thick mucopuslike saliva from the duct’s orifice. We made a presumptive diagnosis of obstructive sialadenitis. However, radiographs—a periapical film of the buccal soft tissue, a panoramic film and an anteroposterior film with the cheek puffed out—did not reveal a stone. Through ultrasonography, we diagnosed an inflamed parotid gland but were not able to identify a calcific body.

Because we suspected a sialolith, we ordered a CT scan. We took axial slices with contrast dye at 5-millimeter intervals. In the region of the parotid duct, we took 2-mm-thick slices, 2 mm apart to negate the possibility of missing a small stone that might be situated between the cuts taken at 5-mm intervals. Soft tissue and bone windows corroborated our clinical impression. We readily observed the opacity of a small sialolith in the anterior segment of Stensen’s duct, just as the duct made its bend around the anterior border of the masseter muscle (Figure). Furthermore, a parotitis secondary to the stone was evident, and we could observe a diffuse, increased glandular density, resulting from the inflammatory process’ cellular and fluid infiltrate.

View larger version (133K): [in this window] [in a new window]   Figure. Computerized tomographic scan, axial view. Stone (thin arrow) in parotid duct is shown as it bends around anterior border of masseter muscle (M). Note increased left parotid density (thick arrow) reflecting the presence of a sialadenitis. Compare left parotid (L) density to right parotid (P) density.

 
The CT scan made it possible for us to estimate the distance of the stone from the orifice. Since it was approximately 1 cm from the duct’s oral opening, we chose an intraoral surgical approach. We made a vertical semilunar incision anterior to the orifice and mobilized a mucosal flap. The duct was dissected free on the undersurface of the flap. Via further blunt dissection, we followed the duct posteriorly and delivered the sialolith after we located it 1 cm from its orifice.

Healing was uneventful. Salivary flow returned to normal one week postoperatively, and, although the left parotid gland was less swollen, it still was somewhat firm.

When we examined the patient six months later, palpation of the left parotid indicated that it was normal in tone and painless. The left parotid salivary flow was normal, and there were no symptoms of parotid swelling or pain associated with meals.

	DISCUSSION

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Various techniques, including lithotripsy,^14,15,19,20 endoscopic techniques,^18,21 an intraductal retrieval basket^12,22 and ductal dilatation with massage,¹⁵ have been advocated for the nonsurgical removal of a parotid stone. However, intraoral surgical removal of a stone is simple and will be successful, provided the limitations of the procedure are understood.

The CT scan accurately shows the location of the stone, in an anterior posterior direction, and its relation to the masseter muscle. Such knowledge is indispensable for any successful intraoral surgical plan for parotid stone removal. It is the ability of the CT scan to identify the exact location of a parotid stone that dictates the surgical approach.

Because of its simplicity, intraoral surgical intervention is always the treatment of choice provided the sialolith is within 1.5 cm of the duct orifice.¹¹ Surgical accessibility and visibility are severely compromised by adjacent anatomical structures when the stone is positioned more than 1.5 cm away from the orifice. Stones placed posteriorly or within the gland require a more extensive extraoral procedure that often incorporates the removal of the parotid’s superficial lobe. Recognition of a stone’s anterior setting and the consequent intraoral approach avoids the surgical morbidity associated with extraoral surgery.

Standard radiography, ultrasonography and sialography often fail to reveal small parotid stones. The CT scan can play a singular role in identifying such stones, provided thin cuts are requested. Usually, the scan is taken at 5-mm intervals between each scanned plane. With such spacing, it is possible for a small stone to fall between successive cuts and not be seen. Therefore, dentists should request thinner planes taken at 1- to 2-mm intervals.

The CT scan is well-suited for the imaging of the semicalcified parotid stone as even minute deposits of calcium will be recognized. It is a procedure that circumvents the technical difficulties and the possibility of stone-obliteration by the dye associated with a sialogram, and it can be used even during episodes of acute parotitis.

Another significant advantage of imaging a parotid stone with a CT scan is the scan’s ability to assess the status of the gland secondary to the stone; sialadenitis and abscess formation can be diagnosed. Occasionally, however, the CT scan will indicate that the damage to the parotid gland is advanced. Surgical gland removal may be required to avoid future flare-ups. The information from the CT scan is incorporated into the therapeutic decision regarding the need for the gland’s removal.

	CONCLUSION

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The CT scan has proved to be a significant radiologic method for imaging small, semicalcified parotid stones and the extent of their effect on the parotid gland. The precise localization of such parotid stones by the CT scan expedites their intraoral surgical removal.

	FOOTNOTES

Mr. Hatzis is a fourth-year dental student, Columbia University School of Dental and Oral Surgery, New York.

	REFERENCES

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