Between the fascial layers in the neck are spaces that may provide a conduit for the spread of infections from the neck to the mediastinum.
(Fig. 8.163):
The first is the pretracheal space between the investing layer of cervical fascia covering the posterior surface of the infrahyoid muscles and the pretracheal fascia (covering the anterior surface of the trachea and the thyroid gland), which passes between the neck and the anterior part of the superior mediastinum.