Imaging of Salivary Glands

25/11/2015Dr. Y. Madhu Madhava Reddy

Salivary Glands

• The salivary glands are exocrine glands (with ducts), that produce saliva and pour their secretion in the oral cavity.

• Major (Paired)• Parotid• Submandibular• Sublingual

• Minor : those in tongue, palatine tonsil, palate, lips and cheeks.

Anatomy

Parotid Gland

• The parotid gland is located behind the angle of the mandible, with the anterior part of the gland lying on the masseter muscle.

• It has a large single duct (Stenson's) that runs forwards crossing the masseter muscle, turning inwards at its anterior border to pierce the buccinator muscle and then opening into the mouth on a papilla opposite the second upper molar tooth.

Parotid Gland

Parotid Gland

• The gland is divided into superficial and deep parts by the parotid plexus (branches of Facial nerve), but however they donot innervate the gland.

• At its anterior margin there is a small separate accessory part which lies between the duct and the zygomatic arch.

Submandibular Gland

• It is located below the mandible and has superficial part that lies on the mylohyoid muscle and deep part that extends deep to the posterior border of this muscle.

• A single duct ( Wharton’s) emerges from deep surface of the gland, tunrs around the posterior border of the mylohyoid muscle and runs deep to that muscle to open on a papilla at the side of the frenulum beneath the tongue.

Sublingual Gland

• The sublingual gland lies anteriorly in the floor of the mouth and opens into the mouth through a number of ducts. Ducts within all of these glands are evenly distributed and gently tapered.

CT and MRI Anatomy

• Parotid glands have variable amounts of fatty stroma, thus have lower CT attenuation (-25 to +15HU) than adjacent muscles, LN and vessels.

• Higher density is seen in Children. In some adults attenuation of parotid glands approaches that of muscle, and in these dense glands, MRI is superior in detection of masses.

• There are between 20 and 30 lymph nodes within the parotid gland, making it a site for metastatic disease from the scalp, external auditory canal and face.

• The submandibular glands have higher attenuation than the parotid glands but are still easily distinguished from the adjacent musculature.

• The sublingual salivary glands and minor (accessory) salivary glands which line the upper aerodigestive tract are not routinely visualised. The minor salivary glands may give rise to masses in the parapharyngeal space.

• The submandibular and sublingual glands lie within their respective spaces; they are separated by the mylohyoid muscle anteriorly but the spaces are continuous with each other posteriorly where the posterior part of the sublingual gland and the deep part of the submandibular gland lie in close proximity.

• The submandibular space is encircled by the superficial layer of the deep cervical fascia and contains the superficial part of the submandibular gland together with submandibular and submental lymph nodes.

• The sublingual space contains not only the sublingual gland and duct but also the deep portion of the submandibular gland and duct.

• Masses arising in the submandibular space tend to remain within that space but masses in the sublingual space may extend to the submandibular space.

• Parotid tail lesions occasionally present as masses at the angle of the mandible and may be mistaken for submandibular masses.

Salivary gland Imaging

• Plain X rays ( Stones, Calcifications, Bony erosions)

• Sialography ( Radiolucent Stones, Sialectasis, duct displacement)

• USG• CT• MRI

Plain Films

• Parotid Gland : AP, tangential, lateral, lateral oblique plain radiographs are useful for showing calculi, soft tissue swellings.

• Submandibular gland is assessed in lateral oblique view with patient finger in mouth, depressing the tongue and pushing the submandibular gland into the sight beneath mandible.

• Stone in anterior part of duct are best demonstrated by placing occlusal film in mouth and using submentovertical projection.

Mandibular occlusal view

Sialography

• Can be performed on parotid and submandibular glands.

• Initial series of plain films are taken to identify RO calculi.

• Sialogogue ( lemon juice or citric acid ) is given to dilate duct orifice.

• Duct intubated by means of blunt tipped, slightly angulated, metal cannula or fine thin walled polythene catheter with a tapered end.

Sialography

• Approximately 0.5 – 1.5 ml of contrast medium ( Lipiodol Ultra fluid or a water soluble medium) is slowly injected by hand until the duct system is filled.

• A series of radiographs are taken or substracted images can be obtained with digital x ray.

• To complete examination few drops of lemon juice is given to stimulate salivation. Further film is taken after an interval of 10min, which normally will show most of contrast medium cleared from ducts.

Sialography

• Indications : Sialoliths, Chronic inflammation and tumours in parotid, submandibular glands and duct diseases.

• Contra indicated in acute sialadenitis as it can exacerbate the condition.

Sialograms

Sialograms

Normal Submandibular and parotid sialogram study

Ultrasound

• Parotid and submandibular glands are examined using a 7.5MHz or higher frequency linear array transducer with patients chin turned away from side being examined.

• Both glands have homogenous echo pattern with scattered echogenic steaks produced by branch ducts converging into main duct.

• ECA and retromandibular vein can both be seen. Few LN’s can be seen within gland.

USG

CT

CT

• The parotid duct will be demonstrated on thin sections taken parallel to the hard palate. The gantry angulation should be adjusted to avoid dental fillings.

• The scan should extend from the skull base to the level of the hyoid bone, to demonstrate the facial nerve canal and to ensure that the parotid tail and the high deep cervical and jugulodigastric lymph nodes have been included

CT

• IV contrast enhancement increases the conspicuity of salivary masses and affords some prediction of their nature.

• CT sialography is alternative method of increasing consipicuity of salivary gland masses but the technique is invasive and is not widely practised as MRI is more beneficial.

• Presence of metallic dentures / metallic fillings can cause artefacts on CT.

MRI

• It allows multiplanar imaging and have intrinsic contrast advantage.

• Reduces artefacts from Dental amalgam.• Disadvantages are its inability to demonstrate

calcifications, whose presence is important in diagnosis of pleomorphic adenoma and sialolithiasis.

• Gadolinium contrast enhancement decrease the conspicuity of some masses.

MRI

• Masses of salivary glands have low T1 signal, particularly contrasted against the fatty stroma of parotid. Fat supressed T1 sequences are superior in determining extent of invasion.

• STIR images are also used.• MR sialography has been described using heavy

T2WI, which contrast ductal fluid against stroma. It helps in diagnosis of Sialectasis upto some extent.

• CT and MRI examinations of the salivary glands are usually requested to evaluate a mass in the region of a salivary gland.

• Value of CT and MRI is more in detection, anatomical placement and demarcation of masses than in their characterisation.

Salivary Gland Lesions

Sialolithiasis

• 80% develop in submandibular glands as these glands produce a more alkaline and viscous saliva and ducts take an uphill course.

• Calculi form as a result of stasis or infection, once formed predispose to further infection and stone formation.

• Majority are Radio opaque and seen on radiographs.

• Multiple calculi are seen in parotid glands.

Sialolithiasis

• Patients with duct calculi present with pain and swelling of gland that is related to meals.

• Sialolithiasis may lead to chronic sclerosing sialadenitis, it is most common in submandibular glands.

Sialolithiasis

• Sialography can identify both RO and RL calculi and associated strictures that develop in ductal system.

• USG can also demonstrate calculi but NCCT is most sensitive of all these techniques.

• CECT can be performed if abscess is suspected.

Sialolithiasis

Acute Parotitis

• Causes: Mumps, sialolithiasis, Staphylococcal and streptococcal infections may develop in debilitated, dehydrated patients with poor oral hygiene.

• Other causes: TB, candidiasis.• CT : Swollen gland, increased enhancement,

surrounding inflammatory stranding and lymphadenopathy.

Acute Parotitis

• Parotitis may be complicated by abscess formation, which is seen as an area of non enhancement on contrast enhanced scans with an irregular enhancing rim.

• Deep parotid infection may extend to parapharyngeal space.

Acute Parotitis

Acute Suppurative Parotitis

• Commonly seen in diabetic patients

Chronic Inflammation

• Recurrent infection, granulomatous and auto immune diseases -> recurrent swelling of the gland.

• Sialography -> narrowing of ducts with areas of strictures and dilatation.

• Calculi are seen in 2/3 of cases.

Sialectasis

• Dilatation or increased calibre of salivary ducts.• Most commonly seen in parotid gland and

associated with ascending infections and gland destruction.

• Etiology: Any condition that causes chronic inflammation.

• Sjogren syndrome, post infectious, recurrent sialadenitis, salivary duct strictures, congenital (rare).

Sialectasis

• Different pattern of dilatation:• Punctate• Globular• Cavitary• Cylindrical• Fusiform

Chronic Inflammation

Strictures

• Results from combination of obstruction and infection.

• Strictures are more sited at orifice of the ducts.• Small stones pass spontaneously but leaves duct

stricture.• Ducts proximal to stricture dilate and contrast

medium is retained on postsialogogue film.• Localized strictures can be dilated using a guide

wire and small balloon catheter.

Strictures

Balloon dilatation of stricture

Myoepithelial sialadenitis(Mikulicz disease)

• It is characterised by lymphocytic infiltration, parenchymal atrophy and myoepithelial islands.

• Involves parotid (85%) and submandibular(15%)

• Most patients will have Sjogrens syndrome, an autoimmune disease involving lacrimal as well as salivary glands causing kertoconjuntivitis and xerostomia.

Sjogrens disease

• Sjogrens may be primary or secondary when associated with other connective disease (RA).

• Patients with myoepithelial sialadenitis are 44 times more risk of developing lymphoma.

• More common in females between 40 – 60 yrs.

Sjogrens disease• CT and MRI: Bilateral parotid enlargement with cystic

lesions with heterogenously enhancing parenchyma.• CT: Honey comb of low density foci in generally

enhancing gland.• T1WI: multiple low signal lesions uniformly distributed

in gland• T2WI: multiple high signal cystic lesions reflecting

watery saliva (salt and pepper appearance) • Punctate changes will progress to globular, cavitary

destructive lesions.

Sjogrens disease

Malignant Lymphoma

• Accounts for 15% of malignant tumours of salivary glands.

• 6% of Sjogrens syndrome patients develop non Hodgkins lymphoma.

• Associated with HIV.• 80% occur in parotid gland.• Increased no. Of intraparotid LN’s with

infiltrative characteristics.

Malignant Lymphoma

Salivary cystic lesions• 5% of salivary masses• DD’s:• Warthins tumor• Lymphoepithelial cyst• 1st branchial cleft cysts• Sialocele• Ranula• Abscess• Necrotic nodes / tumors• HIV multiple b/l cysts

Salivary cystic lesions

Sialosis

• Chr. Non tender enlargement of parotid gland.• B/L and Symmetric• Non inflammatory and non neoplastic lesion• May be ass. With DM and certain medications• Sialography show splaying of duct system• CT b/l enlargement of glands with preserved

density

Sialosis

Salivary Neoplasms

• Eighty per cent of salivary gland tumours are found in the parotid glands. The most common tumour is the pleomorphic adenoma, the majority of which are benign.

• Carcinomas are rare but the probability of a salivary gland tumour being malignant is greatest for masses arising in the smaller salivary glands.

Benign tumors

Pleomorphic adenoma

• Typical CT appearance is smoothly marginated mass which is of higher attenuation that the surrounding gland and show no significant contrast enhancement.

• Larger masses are lobulated or show necrosis, haemorrhage and calcification.

• MRI: Inhomogenous signal, haemorrhage being manifested as high signal on T1.

Pleomorphic adenoma

Pleomorphic adenoma

Pleomorphic adenoma

Warthins tumour

• Second most common benign tumor.• Typically located in superficial part of parotid.• It is the heterotopic salivary gland tissue within

parotid lymph nodes.• B/L in 15% of cases. • They are well defined and cavitate commonly

leading to cystic appearance on CT. • M:F = 3:1• Age of incidence 40 – 70 yrs.

Warthins tumour

Warthins tumour

Warthins tumour

Cystic component with mural nodules1% Malignant transformation

Parotid lipoma

• 1% of parotid lesions• CT and MRI show typical findings• 90% are ordinary lipomas• 10% infiltrate adjacent structures

Parotid lipoma

Parotid lipoma

Lipoma of left parotid gland extending to the deep lobe and anterior parapharyngeal space,

showing high T1 and T2 signal intensity.

Malignant Tumors

Muco epidermoid Ca.

• 30% of salivary malignancies• 50% occur in parotid, 45% in minor salivary gl.• Low grade lesions may appear like benign

tumors.• High grade lesions show malignant characters.

Muco epidermoid Ca.

Malignant deep lobe parotid tumor

Malignant tumors

• Masses in deep lobe of parotid need to be differentiated from parapharyngeal pathologies like carcinoma, sarcoma and neural tumors.

• Metastases and lymphomatous involvement of parotid gland occur due to presence of intraparotid LN, a feature not seen in other salivary glands.

• Mets 2o to skin neoplasms like malignant melanoma, squamous cell carcinoma of face, EAM ,scalp and sq. Cell ca of nasopharynx.

Malignant tumors

• Following parotidectomy, the surgical void fills with fat and scar tissue. Recurrent tumour is best diagnosed with MRI, where distinction between scar and tumour can be made because tumour shows greater contrast enhancement

Non epithelial tumors

• Represents less than 5%.• In children they represent 50%• Lesions:• Hemangioma• Lymphangioma• Lymphoma• Lipoma• Sarcoma....

Hemangioma

• 1-5% of salivary gland tumors• The most common salivary neoplasm in children

(girls)• 90% are of capillary type• Cavernous type occur in older children• Rapid enlargement with bluish skin coloration.• Typically the lesion regress at adulthood.• Strong enhancement with phleboliths may be seen

on CT.

Hemangioma in 6 months old girl

B/L Parotid hemangioma MRI

Marked signal increase in T2WI, signal voids may be seen

Lymphangioma

• Lymphangioma simplex, cavernous lymphangioma, cystic hygroma.

• 5% of all benign tumors in infanct and childhood.• 90% are present by age of 2 years• Commonly arising in posterior neck triangle• Soft tissue painless lesions.• Multilocular lesion with fluid levels are seen on

T2WI.

Cystic hygroma

Intra parotid LNs

• Hyperplasia• Viral / bacterial infections• Granulomatous disease• Lymphoma• Metastatic deposits

• Rapid painful nodal enlargement – Inflammatory nature.

Lymphoma of salivary glands + Cervical nodes

FNAC

• It will correctly predict a benign or malignant process in approximately 90% of cases and make a specific diagnosis in 70%.

• Enthusiasm for FNAC of salivary gland masses varies. It tends to be used in situations where the clinical picture and imaging suggest a benign diagnosis and long-term follow-up is planned, when a metastasis or a mass secondary to a systemic disease such as lymphoma is suspected, or when a patient is considered unfit for surgery.

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