Salivary disease: imaging for obstructive disease and neoplasms

Question 1

Common salivary gland problems (3)

Answer 1

Dry mouth (xerostomia)
Painful and swollen gland 
Lump in salivary gland

Question 2

Dry mouth (xerostomia) causes (lots)

Answer 2

There are a range of causes of dry mouth, including: diabetes, due to raised blood sugar and polyuria; medication, anti-cholinergics, cytotoxics, sympathomimetics, diuretics, anti-depressants; radiotherapy; auto-immune conditions, including Sjögrens syndrome (see Xerostomia symposium).

Question 3

Painful and swollen salivary gland types and causes (3)

Answer 3

Sialadenitis (salivary gland infection) can be acute or chronic. The acute forms are either bacterial or viral in origin. The chronic forms are often secondary to reduced salivary flow (drug-induced, Sjögrens, post-radiotherapy), but also include obstructive sialadenitis.

Question 4

Lump in a salivary gland - what could it be (3)

Answer 4

Typically these are tumours, which can be benign or malignant. Remember that the parotid glands contain small lymph nodes within them (submandibular and sublingual do not) and scalp/ear/haematological cancers can spread to/involve intra-parotid lymph nodes. The history may point you in the right direction.

Question 5

Imaging for
-dry mouth (xerostomia)
-painful and swollen gland
-lump in the gland 
(3)

Answer 5

Dry mouth: ultrasound is first line imaging test if you suspect Sjogren’s syndrome, occasionally sialography can be useful
Painful and swollen gland: plain radiography usually followed by sialography
Lump in the gland: ultrasound with a core biopsy for a tissue diagnosis. For malignant tumours this is followed up with MRI.

Question 6

Dry mouth identified on imaging (3)

Answer 6

Sjögren’s syndrome is the only cause of dry mouth that can be identified on imaging. The disease process destroys the gland parenchyma, producing a typical pattern of changes on imaging.

Question 7

Obstructive sialiadenitis presentation and causes (5)

Answer 7

Common clinical problem, usually presenting as a swollen and painful gland that occurs at mealtimes, or sometimes when thinking about or smelling food.
Caused by salivary calculi (stones), strictures or debris/sludge in the ductal system.
Calculi are the most common in the submandibular gland, whereas strictures (focal narrowing) are more common in the parotid gland. Obstruction of the sublingual gland is very rare, because it lacks a single duct, rather there are multiple tiny openings into the floor of the mouth, like a teabag

Question 8

Investigation of salivary obstruction (3)

Answer 8

Plain film radiographs first then sialography. Ultrasound can identify some stones, but is not as sensitive as a sialogram.
For a submandibular obstruction, a lower true (90˚) occlusal and a posterior oblique occlusal film are needed, possibly with a sectional OPT.
For a parotid obstruction, an AP extra-oral film plus a small dental film inside the cheek are useful

Question 9

Submandibular sialography (3)

Answer 9

Involves injecting iodinated contrast along the submandibular or parotid ducts. The iodine in the contrast makes it densely radiopaque; stones are less dense than the contrast, and they appear as radiolucent filling defects on the image.

Question 10

Treatment of submandibular calculi (3)

Answer 10

If visible in the anterior third of the duct, then surgical excision, usually under local anaesthetic via an intra-oral approach.
If small, mobile and anterior to the mylohyoid bend then basket removal is indicated.
If beyond the mylohyoid bend or too big to remove with a basket, then excision of the submandibular gland via an extra-oral approach.

Question 11

Basket removal of submandibular calculi (3)

Answer 11

An intra-ductal technique done under local anaesthetic.
Helical wire basket inserted into the duct opening (closed). Advance past the calculus and open the basket. Calculus snared within basket and drawn to the duct opening.
Calculus released from the duct with a small papillotomy incision. No suturing is required (causes stenosis).

Question 12

Basket complications (4)

Answer 12

Pain and swelling is to be expected post-procedure.
Failing to remove the stone
Getting the basket stuck in the duct (stone adherent to duct wall, needs to be mobile on sialogram).
Persistent symptoms despite removing the calculus (ductal stenosis post-incision ?).

Question 13

Treatment of parotid obstruction (4)

Answer 13

Strictures
-balloon-dilatation if in the extra-glandular duct (most common), otherwise superficial parotidectomy.
Stones
-if visible at the duct opening then simple surgical excision.
If in the extra-glandular duct, anterior to the posterior border of the ramus, small and mobile, then basket retrieval as per submandibular stones.
If in the gland parenchyma or too large to pass down the duct, lithotripsy (shattered with sound waves) or superficial parotidectomy.

Question 14

Balloon dilatation of ductal strictures (3)

Answer 14

Intra-ductal technique under local anaesthesia: typically Articaine down the duct mixed with iodinated contrast, this produces topical anaesthesia and enables identification of the stricture site. Also submucosal buccal lidocaine injected along the course of the duct.
Dilatation of the parotid papilla with a lacrimal probe followed by insertion of a 2 or 3mm angioplasty balloon along the duct.
The uninflated balloon is positioned across the stricture under X-ray guidance and then inflated to 15 psi for 90 s. Two or three inflations can be needed.

Question 15

Balloons - complications (4)

Answer 15

In some cases the stricture is too tight to pass the balloon, even when a fine guide wire is used for navigation.
Despite the local anaesthetic, dilatation of parotid duct strictures is uncomfortable when the balloon is inflated.
Some strictures will not dilate, even after several balloon inflations
About a third of dilated parotid strictures will re-stenose within 2 years of treatment, and will require a repeat procedure.

Question 16

Salivary gland tumours epidemiology (4)

Answer 16

Most salivary gland tumours have a similar clinical presentation, regardless of histology: they are slow-growing solid masses. Some features are more predictive of a malignant tumour, such as rapid growth, fixation to skin or underlying tissues, pain and in the case of parotid gland tumours, facial nerve weakness.
As a rule of thumb, the smaller the gland the greater the likelihood that a salivary tumour is malignant.
Parotid: 80% benign, 20% malignant
Submandibular: 50% benign, 50% malignant
Sublingual: 15% benign, 50% malignants
Sublingual: 15% benign, 85% malignant
Minor salivary glands: 50% benign, 50% malignant

Question 17

How do you distinguish between salivary gland tumours? (1)

Answer 17

Only a biopsy can distinguish between individual histological diagnoses

Question 18

Pleomorphic adenoma epidemiology (5)

Answer 18

Commonest benign tumour, esp. parotid gland
30 – 60 yrs, mean = 40yrs
M:F = 1:1
Can recur
Small malignant transformation rate

Question 19

Warthin’s tumour epidemiology (5)

Answer 19

Only occurs in parotid, usually at the tail, approx. 10% of benign tumours
Tend to occur later, ≈ 60 yrs
M:F = 2:1
Smokers
May be multifocal,10-15% are bilateral

Question 20

Imaging features of benign salivary neoplasms (3)

Answer 20

Benign salivary neoplasms typically are well-defined solid masses with smooth/lobulated margins. Warthin’s tumours are characterized by their location (parotid tail), their cystic component and when they are bilateral.

Question 21

Imaging features of malignant salivary gland tumours (2)

Answer 21

High-grade malignant salivary neoplasms have an infiltrative, spiculated margin that is ill-defined, which helps distinguish them from benign tumours on imaging.

Question 22

Abnormal intra-parotid lymph nodes (3)

Answer 22

During embryological development, the parotid gland is encapsulated after the development of the lymphatic system, whereas the submandibular and sublingual glands encapsulate before lymphatic development. Hence lymph nodes are found normally within the parotid glands, but not in submandibular or sublingual glands.
Accordingly there is always a differential diagnosis for parotid gland masses that includes pathological intra-parotid lymph nodes. The history can be useful for this, but not always.