The fascial planes of the neck are of considerable importance to the surgeon; they form convenient lines of cleavage through which he may separate the tissues in operative dissections and they delimit the spread of pus in neck infections.
The superficial fascia is a thin fatty membrane enclosing the platysma.
Pretracheal fascia (containing thyroid, trachea, oesophagus and recurrent nerve)
Anterior jugular vein
External jugular vein
Fig. 188 (a) Transverse section of the neck through C6—showing the fascial planes and also the contents of the pretracheal fascia (or 'visceral compartment of the neck'). (b) CT scan through the C6 level; compare this with the diagram.
Left lobe—I of thyroid
The deep fascia can be divided into three layers. 1 The enveloping fascia invests the muscles of the neck. It is attached to all the bony landmarks at the upper and lower margin of the neck: above, to the mandible, zygomatic arch, mastoid process and superior nuchal line; below, to the manubrium, clavicle, acromion and scapular spine. Posteriorly, the ligamentum nuchae provides a longitudinal line of attachment for it.
This enveloping fascia splits to enclose the trapezius, the sterno-cleidomastoid, the strap muscles and the parotid and submandibular glands.
The external jugular vein pierces the deep fascia above the clavicle. If the vein is divided here, it is held open by the deep fascia which is attached to its margins, air is sucked into the vein lumen during inspiration and a fatal air embolism may ensue.
2 The prevertebral fascia passes across the vertebrae and prevertebral muscles behind the oesophagus, the pharynx and the great vessels. Above it is attached to the base of the skull. Laterally, the fascia covers the scalene muscles together with the phrenic nerve, as this lies on scalenus anterior, and the emerging brachial plexus and subclavian artery. These structures carry with them a sheath formed from the prevertebral fascia, which becomes the axillary sheath.
Inferiorly, the fascia blends with the anterior longitudinal ligament of the upper thoracic vertebrae in the posterior mediastinum.
Pus from a tuberculous cervical vertebra bulges behind this dense fascial layer and may form a midline swelling in the posterior wall of the pharynx. The abscess may then track laterally, deep to the prevertebral fascia, to a point behind the sternocleidomastoid. Rarely, pus has tracked down along the axillary sheath into the arm.
3 The pretracheal fascia encloses the 'visceral compartment of the neck'. Extending from the hyoid above to the fibrous pericardium below, it encloses larynx and trachea, pharynx and oesophagus and the thyroid gland. A separate tube of fascia forms the carotid sheath, containing carotid, internal jugular and vagus nerve and bearing the cervical sympathetic chain in its posterior wall. (Some points of clinical significance concerning this fascia are to be found under 'The thyroid', page 267.)
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