Tuberculosis of the Salivary Gland

Definition

This is a chronic mycobacterial infection involving the salivary glands, and usually of dental or tonsillar origin (primary infection), or sometimes via the bloodstream, spread from the lungs (secondary infection).

Incidence/Age

It is rare and can occur in both adults and children. Atypical mycobacterial infection of both the parotid and submandibular glands is increasingly being described in young children.

Anatomy & Physiology

The parotid gland consists of a superficial (outer) and a deep (inner) part, which are separated by the tree-like terminal branches of the facial nerve, responsible for facial movement. Lymph nodes are present within the gland.

Saliva leaves the gland through Stensen's duct, which pierces the facial muscles and enters the mouth through the cheek opposite the second upper molar tooth. Saliva flow is stimulated by chewing and the presence of food in the mouth, particularly sour substances. The stimulus is mediated via parasympathetic nerve fibres carried on the auriculotemporal nerve to the parotid gland.

The submandibular gland consists of superficial and deep parts separated by the myelohyoid muscle. The duct leaves the deep part of the gland and enters the floor of the mouth, meeting its opposite partner. The deep part of the gland is intimately related to the hypoglossal nerve, which moves the tongue, and the lingual nerve, which provides sensation to the front half of the tongue.

Saliva flow is stimulated by the parasympathetic (chorda tympani) nerve fibres, carried along the lingual nerve.

Causes

The main organisms causing tuberculosis of the salivary glands are mycobacterium tuberculosis hominis, and increasingly atypical mycobacteria.

Symptoms/Signs

This condition can present in numerous ways:

1. Acute inflammation of the parotid/submandibular gland, as for acute suppurative sialoadenitis.
2. Chronic inflammation presenting as a slowly growing painless swelling of parotid/submandibular gland. This may need to be differentiated from a non-specific chronic inflammatory conditions, salivary stones and salivary tumours.

Complications of Disorder

• Widespread tuberculous infection (military TB) or progression from primary to secondary tuberculous infection in the absence of appropriate antituberculous chemotherapy.
• Tuberculous skin sinuses (tracks from an abscess cavity to the skin surface) into surgical scars or along tracks where pus has drained spontaneously.
• Facial nerve weakness in parotid tuberculosis.

Tests

• Microscopy and acid fast bacilli culture from pus obtained from either salivary duct openings in the mouth or from needle aspiration of the salivary mass, or during surgical drainage of a salivary abscess.
• Appropriate imaging investigations of the head, neck and chest which might include ultrasound of the neck, chest x-ray or computed tomographic (CT) imaging of the head, neck and chest to assess the size and extent of the problem.
• Sometimes biopsy of the involved gland may be required in the absence of pus being present, or if differentiation from salivary tumour is not otherwise possible.
• Tuberculin testing or sensitin testing for atypical mycobacteria can be helpful in making a dagnosis in patients who have not previously had BCG vaccination or who has not previously been exposed to tuberculous infection.

Treatment

Medical

Medical treatment of tuberculosis, irrespective of site should normally be under the auspices of a physician with a special interest in this field. Chemotherapy agents are the same as used for lung tuberculosis and usually involve 4 drugs for 6 months, Rifampicin, Ethambutal, Isoniazid and Streptomycin. Thereafter ethambutal and or streptom