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Neuroradiology Case of the Week

   Case 68

Karin Westesson and PL Westesson, MD, PhD, DDS

Clinical Presentation:  A 31-year-old female presented with a several year history of intermittent swelling of the right more than the left parotid gland. Swellings were mostly associated with meals. A sialogram of the right parotid gland and a MR of the head and neck were performed for evaluation.

Radiological Findings:  MR imaging showed multiple small cystic cavities in the right parotid gland with no abnormal enhancement. The cystic cavities ranged in size from less than one mm to about 4-5 mm. Stenson’s duct was abnormally dilated and fluid filled. The left parotid gland showed similar changes. The submandibular glands were normal.
    The sialogram of the right parotid gland showed a markedly abnormal Stenson’s duct. It was dilated to twice the normal caliber and had multiple areas of stenosis. The duct was irregularly dilated with multiple areas of stenosis. After canalization and probing the Stenson’s duct with a 0.035 wire, a stream of mucous and saliva was released indicating that a mucous plug had been broken up.

Diagnosis: Sialoadenitis

Discussion:  Sialoadenitis is a glandular inflammation often caused by stone formation in the duct or other blockage of the outflow tract. Sialoadenitis often has associated results in the formation of sialectasis, which implies dilation of the intraglandular ductal spaces. The condition is typically exacerbated by chewing food since this precipitates salivation [2]. This causes swelling of the gland which usually takes one to several hours to resolve. Patients with chronic sialoadenitis present with a persistent diffuse or localized painful swelling of the salivary gland which is associated with an increase in the obstruction of the ductal system. There are other causes of sialoadenitis such as autoimmune conditions. Thus, Sjogrens’s syndrome is an autoimmune inflammatory process that affects the salivary and lacrimal glands.
   This patient had bilateral involvement which makes it more likely that she had an underlying condition that precipitated the bilateral parotid inflammations. Work up for an underlying condition did not reveal any underlying cause for her bilateral parotitis.
    A sialogram will often show a stone or other blockage of the main outflow duct or the focal stricture of the main duct and central ductal dilation. The stone may be radiopaque and can than be seen on plain radiographs or be radiolucent and only seen as a filling defect after injection of contrast. If the obstruction can be relieved by removing the stone or breaking up a mucous plug, the gland may return to normal function. This can only occur if the salivary acini were not entirely destroyed [3]. If the inflammation has been long standing and the outflow blockage can not be relieved, permanent damage to the gland may result. This can eventually lead to the need for removal of the damage gland [2,3].
    Imaging, other than a sialogram of sialoadenitis, is relatively nonspecific. On a CT scan, the salivary gland shows to have numerous small radiolucencies - micro-abscesses within the parotid tissue that has low density. Some of them may have peripheral rim enhancement and other may have few scattered areas of calcification [2]. On T1-weighted MR scans, the gland will also appear enlarged, heterogeneously low-signal. On the T2-weighted scans, the gland is brighter than normal and there are often many small fluid collections, presumed micro-abscesses with very bright signal. The signal intensity reflects a degree of chronic inflammatory cellular infiltrate versus the presence of associated edema fluid [3].

References:

1. Bowen BC, Whiteman ML. Salivary glands and lymph nodes. In: Neuroimaging. Ed. William W. Orrison Jr. Philadelphia: W. B. Saunders, 2000.
2. Grossman RI, Yousem DM. Neuroradiology: The Requisites. St. Louis: Mosby, 1994.
3. Som PM, Brandwein MS. Salivary glands: anatomy and physiology. In: Head and Neck Imaging, 4th ed. Eds. Peter M. Som and Hugh D. Curtain. St. Louis: Mosby, 2003.