Fascial Layers of the Neck

Original Author: Oliver Jones
Last Updated: May 10, 2018
Revisions: 29
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Fascia is a layer of fibrous tissue that surrounds muscles, vessels and nerves. In the neck, there are several layers of fascia, which act to support and compartmentalise the structures present.

In this article, we shall look at the anatomy of the fascial layers of the neck, and examine their clinical significance as pathways for infection spread.


Superficial Cervical Fascia

Fig 1.0 - The platysma muscle, located within the superficial cervical fascia.

Fig 1.0 – The platysma muscle, located within the superficial cervical fascia.

The superficial cervical fascia lies between the dermis and the deep cervical fascia. It contains various structures:

  • Neurovascular supply to the skin
  • Superficial veins (e.g the external jugular vein)
  • Superficial lymph nodes
  • Fat
  • Platysma muscle

The platysma muscle is situated on the anterior aspect of the neck. It has two heads, which originate from the fascia of the pectoralis major and deltoid. Fibres from the two heads cross the clavicle, and meet in the midline, fusing with the muscles of the face. Motor innervation to the platysma is via the cervical branch of the facial nerve.


Deep Cervical Fascia

The deep cervical fascia is located underneath the superficial fascia, and is organised into several layers. These layers act like a shirt collar, supporting the structures and vessels of the neck.

We shall now look at the layers of the deep cervical fascia in more detail (superficial to deep):

Investing Layer

Fig 1.1 - Transverse section of the neck. The investing layer of fascia in highlighted in blue. Note how the fascia completely envelopes the SCM and trapezius.

Fig 1.1 – Transverse section of the neck. The investing layer of fascia in highlighted in blue. Note how the fascia completely envelopes the SCM and trapezius.

The investing layer is the most superficial of the deep cervical fascia.

It surrounds all the structures in the neck. Where it meets the trapezius and sternocleidomastoid muscles, it splits into two, surrounding them.

The investing fascia can be thought of as a tube; with superior, inferior, anterior and posterior attachments:

  • Superior: attaches to the external occipital protuberance and the superior nuchal line.
  • Anterior: attaches to the hyoid bone.
  • Inferior: attaches to the spine and acromion of the scapula, the clavicle, and the manubrium of the sternum.
  • Posterior: attaches along the ligamentum nuchae.

Pretracheal Layer

The pretracheal layer of fascia is situated anteriorly in the neck. It spans between the hyoid bone and the thorax, where it fuses with the pericardium.

The trachea, oesophagus, thyroid gland and infrahyoid muscles are enclosed by the pretracheal fascia. It can be anatomically divided into two parts:

  • Muscular – encloses the infrahyoid muscles.
  • Visceral – encloses the thyroid gland, trachea and oesophagus.

The posterior aspect of the visceral fascia is formed by contributions from the buccopharyngeal fascia (a fascial covering of the pharynx).

Fig 1.2 - Transverse section of the neck, showing the pretracheal fascia in red.

Fig 1.2 – Transverse section of the neck, showing the pretracheal fascia in red.

Prevertebral Layer

The prevertebral fascia surrounds the vertebral column and its associated muscles (scalene, prevertebral, and deep muscles of the back). It has attachments along the antero/posterior and supero/inferior axes:

  • Superior: attaches to the base of the skull.
  • Anterior: attaches to the transverse processes and vertebral bodies of the vertebral column.
  • Posterior: attaches along the ligamentum nuchae.
  • Inferior: fuses with the endothoracic fascia of the ribcage.

The anterolateral portion of prevertebral fascia forms the floor of the posterior triangle of the neck. It also surrounds the brachial plexus and subclavian artery as they leave the neck, forming the axillary sheath.

 

Fig 1.3- Transverse section of the neck. The carotid sheaths and prevertebral sheaths are highlighted.

Fig 1.3- Transverse section of the neck. The carotid sheaths and prevertebral sheaths are highlighted.

Carotid Sheaths

The carotid sheaths are paired structures which enclose important vessels and nerves. They are formed by contributions from the pretracheal, prevertebral, and investing fascia layers.

The contents of the carotid sheath are:

  • Common carotid artery (which bifurcates within the sheath into the external and internal carotid arteries).
  • Internal jugular vein.
  • Vagus nerve.
  • Cervical lymph nodes.

The carotid fascia is organised into a column, which runs from the base of the skull to the thoracic mediastinum. This is of clinical importance as a pathway for the spread of infection.

Clinical Relevance: Spread of Infections

The neck fascia compartmentalises the structures within the neck. These layers of tough fascia define where infection can spread (e.g a superficial skin abscess is prevented from spreading further into the neck by the investing fascia).

Infections that occur deep to the investing fascia have a well-defined spread:

  • Posterior to the prevertebral fascia – This can erode through the prevertebral fascia, and drain into the retropharyngeal space (a space between the pretracheal and prevertebral fascial layers). The retropharyngeal space extends into the thorax, and infection can spread to the mediastinal contents.
  • Between the investing fascia and visceral part of the pretracheal fascia – This can spread inferiorly into the chest, causing infection of the anterior mediastinum.

 

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Which two muscles are entirely surrounded by the investing layer?
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The posterior aspect of the pre-tracheal fascia is known as what?
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The anterolateral portion of the prevertebral fascia forms the floor of which anatomical triangle?
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