Curriculum · Surgery
Anatomical localisation of a neck swelling
What it is
When there is a neck swelling, the first thing to identify is whether it is an anterior or a posterior neck swelling. An anterior neck swelling is anterior to the anterior border of the SCM muscle, and a posterior swelling is posterior to the posterior border of the SCM muscle. The parts named around the two triangles are the inferior border of the mandible, the sternocleidomastoid muscle, the clavicle and the trapezius muscle. A third group of masses sits in the midline, in the central neck, and not in either triangle.
How it presents
The place decides a large part of the list before the swelling is even felt.
- Central neck masses: thyroglossal cyst, thyroid mass, submental lymphadenopathy, cervical cleft.
- Anterior triangle masses: branchial cyst, submandibular abscess, thyroid nodule, laryngocele.
- Posterior triangle masses: cystic hygroma, clavicular tumor, cold abscess, which is an abscess lacking the usual inflammation, for example a TB abscess.
The level within the triangle cuts the list further. An anterior neck swelling in the upper 1/3 of the anterior neck triangle is a branchial cyst, from failure of obliteration of the 2nd branchial cleft; the branchial cleft cyst is a smooth, painless, slowly enlarging lateral neck mass that often follows a URTI, at the anterior border of the sternocleidomastoid it is intermittent, soft and fluctuant, and it may become infected. A posterior neck swelling in the lower 2/3 of the posterior neck triangle is a cystic hygroma, from maldevelopment of lymphatic tissue; it is a thin walled cyst that transilluminates, painless, soft and compressible, present by the age of 2 years, and infection causes a sudden increase in size. Two midline swellings are separated by how the mass moves and by age. A thyroglossal cyst sits at the midline below the hyoid bone, moves with swallowing and with tongue protrusion, is linked to the foramen caecum, and enlarges with URTI; a goitre is a midline swelling that moves upwards on swallowing in a patient who is systemically well, and patients with a goitre are often euthyroid or have minor symptoms. Age parts them too: a thyroglossal cyst is usually in children, with up to 40% after 20 years old, and it would be unusual in an older patient, since these cysts typically present in patients under 20 years. Two more are known by what they do rather than by where they sit: a small fluctuant swelling on the side of the neck that gurgles when palpated, with dysphagia and halitosis, is a pharyngeal pouch, and TB lymphadenitis is usually in adults, bilateral, and in the posterior triangle.