Surgical Anatomy: Salivary Glands

Salivary Glands

• There are two types of salivary glands: major and minor.
• Major salivary glands include:
• Parotid salivary glands (pair)
• Submandibular salivary glands (pair)
• Sublingual salivary glands (pair)
• Minor salivary glands include:
• Multiple scattered salivary glands (around 600-1000) found in the submucosa of the oral cavity, hard and soft palate, nasal cavity, nasal and paranasal sinuses, pharynx, and larynx.

Embryology

• The parotid gland develops between the 6th and 8th weeks of gestation.
• The parotid gland grows in a posterior direction, surrounding the facial nerve.
• The parotid gland is the last to become encapsulated, after the lymphatics develop, resulting in entrapment of lymphatics in the parenchyma of the gland.
• This entrapment is thought to play a role in the development of Warthin's tumors and lymphoepithelial cysts within the parotid gland.

Anatomy of Parotid Gland

• The parotid gland lies in front of and below the lower half of the ear.
• It is wrapped around the vertical ramus of the mandible, with its superficial portion projecting forwards on the surface of the masseter.
• The gland reaches up to just below the zygomatic arch and down into the neck.
• The parotid gland can be felt only in pathological conditions.

Parotid Duct (Stensen's Duct)

• The duct arises from the anterior border of the parotid and parallels the zygomatic arch.
• The duct measures 5 cm in length and 5 mm in diameter.

Acute Suppurative Sialadenitis

• Pathology:
• The parotid is the most common gland involved.
• The gland and duct are congested, edematous, and may suppurate.
• Complications:
• Abscess formation
• Chronicity and stone formation
• Spread to surrounding tissues (e.g., Ludwig's angina)

Clinical Picture

• General symptoms:
• Toxemic symptoms (e.g., fever, headache, anorexia, malaise)
• Local symptoms:
• Pain: early, dull aching, later severe throbbing
• Swelling: elevating the lobule of the ear, red, warm, edematous, tender, and fluctuate
• Opening of the duct: red, raised, and edematous, with possible discharge
• Trismus: restricted movement of the TMJ

Investigations

• Leukocytosis
• X-ray film may show calcifications or stones
• Ultrasound

Treatment

• Conservative treatment:
• General: rest, antibiotic (clindamycin), analgesics, and tonics
• Local: hot fomentation, H2O2 mouth wash, and KI as sialogogue
• Surgical treatment:
• Indications: failure of conservative treatment, signs of suppuration (abscess formation)
• Procedure: Hilton's method

Sialectasis

• The dilated ducts and branches are visualized as a snowstorm appearance on a contrast study.
• Initial treatment is conservative, involving citric drinks to stimulate salivary flow and massage of the affected gland to squeeze out accumulating epithelial debris.

Radiation Sialadenitis

• Caused by radiation to the nasopharynx or skull base
• Salivary secretion is temporarily suppressed, and the patient can be helped by the administration of sialagogues as citrus fruits.

Autoimmune Salivary Diseases

• Sjogren's disease:
• More common in women
• Manifestations include dryness of the mouth, dryness of the eye, and rheumatoid arthritis
• Aetiology is not exactly known, but thought to be caused by a cytomegalovirus which affects the ducts of the salivary glands, rendering them antigenic.
• Patients with Sjogren's disease are 44 times more prone to the development of lymphoma than the general population.

Benign Lymphoepithelial Lesions

• An uncommon disease characterized by progressive lymphocytic infiltration and diffuse enlargement of the salivary glands, particularly the submandibular and parotid.

Malignant Parotid Tumors

• Pleomorphic adenoma of the parotid:
• Typically raises the lobule of the ear and does not affect the facial nerve
• Differential diagnosis:
• Extra parotid swellings (e.g., lymph nodes, sebaceous cysts, lipomas)
• True parotid enlargement (e.g., non-neoplastic salivary gland disease)
• Hypertrophy of the masseter

Investigations

• Not routine as in most cases, clinical diagnosis is reliable enough to proceed to treatment
• Biopsy:
• FNAC is allowed (reliable investigation that needs an expert cytologist)
• Open surgical biopsy of the major salivary glands is contraindicated
• Neck US
• CT scan and MRI to show the extent of the tumor
• Isotope scanning with technetium to show a cold spot in salivary neoplasms

Treatment

• Surgery is the only reliable form of treatment of salivary neoplasms

Superficial Parotidectomy

• The CT scan shows the left facial nerve and its branches preserved