Obstruction and trauma (Table 42.4)

Papillary obstruction

Occasionally a rough upper molar tooth or an overextended denture flange will irritate the parotid papilla. If this is suffi­cient to cause ulceration with consequent inflammation and oedema this may obstruct salivary flow, particularly at meal times when the flow rate is increased. In this situation the patient has classical rapid onset pain and swelling at meal times.

If the trauma to the parotid papilla continues there will be progressive scarring and fibrosis in the soft tissues and permanent stenosis of the papilla can occur. A papillotomy will be required. This is a simple procedure performed under local anaesthesia. A probe is inserted into the orifice of the papilla and with a scalpel blade the papilla is split open by incising down on to the probe. This lays open the papilla and divides the stenosis allowing free drainage of saliva.

Stone formation (sialolithiasis)

Eighty per cent of all salivary stones occur in the sub­mandibular gland, 10 per cent occur in the parotid, 7 per cent in the sublingual gland and the remainder occurs in the minor salivary glands. It is believed that the majority of stones occurs in the submandibular glands because their secretions contain mucus and the viscosity is higher. Eighty per cent of submandibular stones are radio-opaque and can be identified using plane radiographs. By contrast the majority of parotid stones are radiolucent and cannot be detected on plane radiography (Fig. 42.6).

The classical presentation is of acute pain and swelling at meal times. Onset is rapid — within a minute of starting the meal — and the swelling resolves over a period of about 1 hour after the meal is completed.

However, this classical picture only occurs when the stone causes almost complete obstruction often when it is impacted at the opening of Wharton’s duct. More often the stone causes only partial obstruction and is lying either within the hilum of the gland or within the duct in the floor of the mouth. In this situation the patient may complain of occasion­al swelling often with minimal discomfort or of a chronically enlarged mass in the submandibular triangle with episodes of dull aching pain. This results from chronic bacterial infection arising in an obstructed gland with salivary stasis and poor emptying. Often a salivary stone is totally asymptomatic and is discovered coincidentally during radiography for other reasons. If a stone is identified on plane radiographs, no other investigation is necessary. Parotid stones often impact at the parotid papilla or alternatively take on a ‘stag-horn’ shape and form at the junction of the two main collecting ducts and the Stenson’s duct (Fig. 42.7). If the stone is trapped at the duct papilla it can often be released by gently probing and carrying out dilatation of the papilla. It may he necessary to slit the duct in order to release the stone.

If the stone is lying in the submandibular duct in the floor of the mouth anterior to the point at which the duct crosses the lingual nerve (second molar region) the stone can be released by opening the duct longitudinally (Fig. 42.8). It is important to pass a large suture around the duct proximal to the stone so that during the operative procedure the stone cannot be displaced backwards in the duct. Once the stone has been released the wall of the duct should be sutured to the mucosa of the floor of the mouth to maintain an opening for the free drainage of saliva. No attempt should be made to repair the duct wall as this will lead to stricture formation. A parotid stone located at the confluence of the collecting ducts can be released surgically by raising a preauricular flap, exposing the parotid duct and again incising it longitudinally to release the stone.

Obstruction in and around the duct wall

Scarring and fibrosis in the duct wall stricture formation will also result in obstruction to salivary flow. It often results as a complication of long-standing sialolithiasis hut it may occur as a result of trauma particularly to the floor of the mouth. Subsequent healing and scarring can result in a stenosis of the duct. In patients with masseteric hypertrophy the parotid duct may be stretched around the anterior border of the muscle and this may cause obstruction of salivary flow at meal times.

Mucoceles

Mucus retention cysts and mucus extravasation cysts arise in the minor salivary glands as a result of mechanical damage to the gland or its duct. The common sites are on the mucosal aspect of the lower lip particularly in patients with a deep overbite and in the buccal mucosa posteriorly where an upper wisdom tooth is erupting buccally. Typically the patient presents with a history of recurrent swellings that develop over days or weeks, rupture and then recur after a few weeks. The cysts rarely exceed 1 cm in diameter and are tense bluish sessile swellings. The treatment is not to the cyst itself but to the underlying minor gland which should be excised under local anaesthesia.

A ranula is no more than a large mucocele arising from the sublingual gland. Classically the ranula presents as a large tense bluish swelling in the floor of the mouth anteriorly often displacing the tongue (Fig. 42.9). However, the ranula may push its way though the midline mylohyoid dehiscence in the floor of the mouth and enter the submental space presenting as a midline swelling in the upper neck. This is the ‘plunging ranula’. The treatment of a ranula is excision of the sublingual gland.