Parotid Gland Injury

Anatomy: why the parotid matters

The parotid gland lies over the jaw angle, in front of and below each ear. It produces saliva that drains through Stensen's duct, which runs forward across the cheek muscle and opens inside the mouth opposite the upper second molar.

The facial nerve passes through the parotid gland, dividing into branches that control the muscles of facial expression: forehead, eyelids, cheek, mouth and neck. Injury anywhere along the gland can damage these branches.

A rough surface guide: the duct runs along a line drawn from the bottom of the ear (tragus) to the middle of the upper lip. Wounds crossing the middle third of this line are at high risk of duct injury.

Causes

• lacerations from glass, knives or sharp objects
• dog and other animal bites, common in children
• gunshot and penetrating wounds
• blunt trauma from falls, assaults or car crashes, sometimes with facial fractures
• surgery on the parotid gland, face or jaw

Signs and symptoms

• a cut or wound over the cheek
• facial weakness: drooping mouth, inability to close the eye, flat forehead on one side. See facial nerve palsy
• clear, watery fluid (saliva) coming from the wound, often increasing when eating
• sialocele: a soft, sometimes tender swelling under the skin from saliva pooling, usually appearing days after injury
• salivary fistula: a persistent channel leaking saliva through the skin
• swelling, bruising and pain
• signs of infection: redness, warmth, pus, fever

Diagnosis

• careful examination of facial nerve function before any numbing injection, testing each branch: raise eyebrows, close eyes tightly, smile, puff cheeks
• duct assessment: a thin probe or cannula is passed into the duct opening inside the mouth; fluid or dye emerging in the wound confirms a duct injury
• checking the duct opening: milking the gland and looking for saliva or blood at the opening in the mouth
• imaging: ultrasound for sialoceles; CT for deep wounds, foreign bodies or facial fractures; sialography occasionally
• analysis of wound fluid for amylase confirms saliva

Treatment

Wound care

Wounds are cleaned and explored, usually in an operating room for deep injuries. Antibiotics are given for bites and contaminated wounds, and tetanus protection is updated.

Facial nerve repair

If a major nerve branch is cut, it is repaired with fine stitches under a microscope, ideally within 72 hours, while the cut ends can still be stimulated and identified. Very small branches near the front of the face often recover without repair. Nerve grafts are used if there is a gap. Recovery after nerve repair is slow, over many months, and may be partial. Eye protection with lubricants and taping is essential if the eye cannot close.

Duct repair

A cut duct is repaired over a thin tube (stent) left in place for about 2 weeks, or tied off or redirected into the mouth in some cases.

Gland injury, sialoceles and fistulas

• pressure dressings and repeated needle drainage of sialoceles
• anti-saliva medicines (anticholinergics) to reduce saliva flow
• botulinum toxin injection into the gland, which temporarily reduces saliva production and helps leaks heal
• avoiding sour and stimulating foods during healing
• surgery for persistent fistulas, rarely

Complications

• permanent facial weakness
• persistent sialocele or salivary fistula
• infection (salivary gland infection)
• duct narrowing causing recurrent swelling with meals
• Frey syndrome: sweating and flushing of the cheek when eating, after parotid injury or surgery
• scarring

Outlook

When duct and nerve injuries are recognized and repaired early, most people recover well. Many sialoceles and fistulas resolve within weeks with conservative treatment. Facial nerve recovery depends on the injury's location and severity; partial recovery is common, and facial reanimation procedures are available for lasting weakness.

Frequently asked questions

What are the signs of a parotid duct injury?

Signs include a cheek wound along a line from the ear to the upper lip, clear fluid leaking from the wound especially when eating, and later a soft swelling under the skin (sialocele). A doctor can confirm it by passing a probe into the duct opening inside the mouth.

Can a parotid gland injury cause facial paralysis?

Yes. The facial nerve runs through the parotid gland, so injuries here can cause weakness of facial muscles on that side. Major nerve branches should be repaired early, ideally within 72 hours, for the best chance of recovery.

What is a sialocele?

A sialocele is a collection of saliva under the skin that forms after injury to the parotid gland or duct. It appears as a soft swelling that may grow with meals. It is often treated with drainage, pressure dressings and sometimes botulinum toxin.

How long does a parotid injury take to heal?

Simple gland injuries and sialoceles often settle within 2 to 6 weeks. Duct repairs heal over a few weeks with a stent in place. Facial nerve recovery after repair takes many months and may be incomplete.