Salivary gland function after sialolithiasis: Scintigraphic examination of submandibular glands with 99mTc-pertechnetate

710

DISCUSSION

gland and remaining there because of complete duct obstruction. Thus, the salivary gland actually functioned significantly. When salivary function was evaluated by Cmax and ratio of excretory grade by stimulation, the numerical values on the two parameters increased after sialolithectomy from the preoperative pattern of M, A, and P, with all showing recovery offunction of varying degrees. Therefore, these parameters should be useful indicators for salivary function in patients with sialolithiasis. Among the four cases showing a P pattern, two revealed Nand M patterns after sialolithectomy: ie, they recovered from severe hypofunction to a moderate or almost-normal grade. Only two cases out of nine remained in a hypofunctional condition. The functional recovery rate after sialolithectomy has been reported to be 75%,5 and 100%.3 These figures suggest justification for initial oral sialolithectomy in spite of the fact that there exist cases which remain in hypofunction after sialolithectomy, as shown in this study. If we take the point of view that the salivary gland should be excised when there is severe hypofunction or no function of the submandibular gland, some glands would have been inappropriately removed, as shown in Table 3. Therefore, we believe that the following operative criteria should be applied for sialolithiasis of the submandibular excretory duct: Precise examination and evaluation of the sialolithiasis should first be

performed with regard to such points as location of the calculus, preoperative salivary function by scintigraphy, and ductal condition by sialography. Sialolithectomy should then be performed initially, and periodic follow-up examination should be instituted. Consequently, the necessity for further operative intervention should be determined by evaluation of salivary gland function. References I. Ohrt HJ, Shafer RB: An atlas of salivary gland disorders. Clin Nucl Med 7:370, 1982 2. Isacsson G, Isberg A, Haverling M, et aI: Salivary calculi and chronic sialoadenitis of the submandibular gland: A radiographic and histologic study . Oral Surg 58:622, 1984 3. Nishi M, Takashima H, Marutani K, et al: Assessment of gland function with sialoscintigraphy following sialolithectorny for calculi in posterior mandibular duct. Jpn J Oral Maxillofac Surg 32:2311, 1986 4. Sato Y: Clinicopathological investigation of submandibular sialolithiasis-Comparison of sialogram and histopathology-Jpn J Oral Maxillofac Surg 30;274, 1984 5. Van den Akker HP, Busemann-Sokole E: Absolute indications for salivary gland scintigraphy with 99mTc-pertechnetate. Oral Surg 60:440, 1985 . 6. Sugihara T, Yoshimura Y: Scintigraphic evaluation of the · salivary glands in patients with Sjogren's syndrome. Int J Oral Maxillofac Surg (in press) 7. Mita S, Kohno M, Matsuoka Y, et al: Diagnostic availability of RI-sialography in Sjogren's syndrome. Ryumachi 21:305, 1981 8. Isacsson G, Ahlner B, Lundquist PG: Chronic sialoadenitis of the submandibular gland: A retrospective study of 108 cases . Arch Otorhinolaryngol232:91, 1981

J Oral Maxillofac Surg 47:710-711.1989

Discussion Salivary Gland Function After Sialolithiasis: Scintigraphic Examination of Submandibular Glands With 99mYc·Pertechnetate

Stephen E. Feinberg, DDS, MS, PhD Ohio State University, Columbus

The most important diagnostic tools in the evaluation of salivary gland function are a detailed history and a thorough physical examination. The diagnosis and eventual treatment can be assisted by the use of other modalities such as sialography, sialometry, sialochemistry, microbiology, computered tomography, magnetic resonance imaging, ultrasound, fine-needle aspiration, incisional or excisional biopsy, and as discussed in this article, scintigraphy. Sequential salivary gland scintigrapy is a relatively noninvasive procedure, is well tolerated by the patient, and is primarily suited to assess

glandular function. The saliva~ glands can be imaged following the administration of "Tc-pertechnetate (Tc) or radioactive iodine. Tc is the preferred agent owing to its low radiation dose, short half-life of six hours, and desirability of its photon emission, gamma, which easily penetrates tissue and can be measured by an external detector. Salivary scanning is made possible by the gland's ability to concentrate radionuclide before excreting it into the saliva. The Tc is administered intravenously in doses ranging from 0.5 to 10 MeL A vascular blush is seen immediately outlying the parotid glands even if the glandular epithelium does not concentrate the tracer. The concentration phase begins within the first ten minutes and represents the active accumulation of radionuclide by the ductile epithelium; this phase can be enhanced by cholinergic drugs such as pilocarpine or carbachol. The excretory phase begins ten to 40 minutes following administration of Tc and represents the tracer being transported into the saliva and excreted into the oral cavity;

711

STEPHEN E. FEINBERG

this phase may be enhanced by drugs such as tartaric acid, which was used in this study. Scintigraphy by itself is rarely diagnostic, and the results should always be interpreted in the context of data provided by the history, physical examination, and other diagnostic modalities. The absolute indications for salivary gland scintigraphy with Tc have been delineated by van den Akker and Busernann-Sokole. I They include technical failure (inability to probe and cannulate a main excretory duct), developmental anomalies (aplasia or agenesis of the excretory apparatus), obstructive disorders (sialolithiasis, mucous plugs), traumatic lesions and fistulae (secondary to sharp or blunt trauma, or surgery in the region of the main excretory duct), and for evaluation of glandular function after surgical treatment (subtotal or total excision, ligation of main excretory duct, sialoductoplasty). When a stone is present in the submandibular duct, the choice of treatment is primarily based on duration, severity of obstruction, degree of inflammation, age of the patient, and location of the stone in the duct. Yoshimura et al have given us in this article yet another means to aid in determining appropriate treatment by assessing glandular function through sequential Tc scans. As they have

pointed out , removal of sialoliths from the main excretory duct can result in eventual regeneration of glandular parenchyma.i-' and therefore, sialoadenectomy is not always necessary. There is also no evidence to support the idea that an atrophic gland will cause problems if it is not removed. The excision of a submandibular gland is not without risks such as a facial scar or damage to the lingual and hypoglossal nerve or the mandibular branch of the facial nerve. Thus, one should be prudent in excising an atrophic but asymptomatic gland . In this age of litigious suits, patients should be well informed and given appropriate treatment options.

References I. van den Akker HP, Busemann-Sokole E: Absolute indications for salivary gland scintigraphy with 99mTc_per_ technetate. Oral Surg 60:440, 1985 2. van den Akker HP, Busemann-Sokole E: Submandibular gland function following transoral sialolithectomy. Oral Surg 56:351, 1983 3. Bhaskar SN, Lilly GE, Bhus sry B: Regeneration of the salivary glands in the rabbit. J Dent Res 45:37, 1%6