The suprahyoid neck
The suprahyoid neck extends from the skull base to the hyoid bone. It is divided into a number of spaces by the three layers of deep cervical fascia, which act as barriers to the spread of disease (Fig. 4.1).
This method also simplifies the differential diagnosis and has largely replaced the divisions based on various muscular triangles.
The three layers of deep cervical fascia are the superficial (investing) layer, the middle (visceral) layer and the deep (prevertebral) layer.
The superficial layer invests all the deep structures apart from the platysma and superficial nodes and sends slips that envelop the sternocleidomastoid and trapezius muscles and the parotid and masticator spaces.
The middle layer is more complex. It lies deep to the anterior strap muscles, surrounds the constrictor muscles, oesophagus and thyroid and contributes to the carotid sheath and the anterior aspect of the retropharyngeal space.
The deep layer encircles the vertebrae, paraspinal and prevertebral muscles.