This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
Abscesses of the neck usually arise in connection with the lymphatic nodes. They may also start from infected wounds, carious teeth, suppuration of the thyroid gland, and other causes. They may have their course influenced by the various layers of the deep fascia.
As the submaxillary space has the mylohyoid muscle as its floor, abscesses here show below the body of the mandible between it and the hyoid bone. Usually they point towards the skin. Infection of this space may occur from the teeth. Tillmans ("Surgery," vol. 1, p. 434) saw a case in which in four days the pus caused death from infection of the mediastinum and pleura. This proceeded downward from a badly extracted tooth and thence under the deep fascia of the neck to the chest.
The pus, filling the submaxillary space, as can also occur in Ludwig's angina, which is an infective inflammation of the submaxillary and sublingual regions, may follow the lingual and facial arteries to the sheath of the great vessels and down into the superior mediastinum. The infection in Ludwig's angina may pass around the posterior edge of the mylohyoid muscle and involve the structures around the base of the tongue and pharynx, and produce oedema of the larynx and death (see page 200).
Fig. 179, - Section through the upper portion of the third cervical vertebra, showing the buccopharyngeal and prevertebral fascias and retropharyngeal space.
Pus in the suprasternal notch or space of Burns bulges anteriorly but may perforate posteriorly. The sternothyroid and sternohyoid muscles are attached to the posterior surface of the sternum; but the layer of fascia on their anterior surface is very thin, so that pus may either pass between the muscles or perforate them and so pass down in front of the pretracheal fascia close to the under surface of the sternum. It would then tend to show itself in the upper intercostal spaces, close to the sternum.
Pus between the pretracheal and stiperficial layers, as may occur from abscesses of the thyroid gland, tends to work its way downward rather than laterally. The pretracheal fascia at the sides blends with the sheath of the vessels and the fascia covering the posterior surface of the sternomastoid muscles. In this space lie the sternohyoid, sternothyroid, and omohyoid muscles. The pretracheal fascia is beneath them and the superficial layer of the deep fascia above. Pus can follow the posterior surface of these muscles down behind the sternum in front of the innominate veins and arch of the aorta.
Pus between the pretracheal and prevertebral layers cannot go further to one side than the sheath of the vessels. Therefore it follows the trachea and oesophagus down into the posterior mediastinum. This space, between these layers, is sometimes called the visceral space because it contains the oesophagus, trachea, and thyroid gland. Pus in this space can also perforate into the trachea, pharynx, oesophagus, or even extend laterally and involve the great vessels.
If the anterior portion of the thyroid gland suppurates, the pus may perforate the
Fig. 180. - The superficial layer, pretracheal layer, and prevertebral layer of the deep cervical fascia thin pretracheal fascia covering it and pass down behind the sternohyoid and sternothyroid muscles into the anterior part of the superior mediastinum.
Pus posterior to the prevertebral fascia, as from caries of the vertebrae, if high up may bulge into the pharynx, forming a retropharyngeal abscess. It may follow the scaleni muscles and brachial plexus down around the axillary artery into the axilla. In the neck it shows itself posterior to the carotid arteries and to the outer edge of the sternomastoid muscles.
Pus in the sheath of the great vessels, when originating from lymphatic nodes, may first raise the sternomastoid muscle and show itself along its anterior border; it may perforate the lumen of the vessels; it may pass down with the vessels into the superior mediastinum; or it may bulge into the visceral space between the prevertebral and pretracheal layers and follow the trachea and oesophagus down into the chest. Should it tend outwardly it may break into the posterior cervical triangle between the prevertebral and superficial layers and show itself above the clavicle.