Anatomy of neck spaces
These spaces are present in the neck between the layers of cervical fascia. These spaces are important from the point of view of clinician because of the propensity of infections to involve this space and to spread along these spaces to involve other areas like the mediastinum. Many of these spaces could as well be inconsequential.
There are two types of fascial spaces in the neck.
I. Those associated with muscles
II.Those associated with viscera and vessels
Fascial spaces associated with muscles are limited by the insertion of muscles to bones. These muscular insertions serve as a limiting factor to spread of infections from these spaces. Spaces associated with viscera and blood vessels are not limited by insertion of muscles and hence infections cross and travel long distances if these spaces are involved.
Visceral spaces:
Lateral pharyngeal space: (Para pharyngeal space)
This space is situated lateral to the fascia covering the constrictor muscles of the pharynx (buccopharyngeal fascia). Lateral to this space lie the pterygoid muscle, mandible and carotid sheath.
Superiorly it extends up to the skull base while inferiorly it ends at the level of hyoid bone because of the attachment of the submandibular gland sheath to the sheaths of the stylohyoid muscle and the posterior belly of digastric muscle.
The carotid sheath lies close to the posterolateral wall of this space.
Postero medially this space communicates with the retropharyngeal space.
Anteriorly and inferiorly this space communicates with the spaces associated with the floor of the mouth.
This space is most commonly involved in neck space infections. Infections from this space can easily spread to the carotid and retropharyngeal spaces.
Common routes of infections of parapharyngeal space:
1. Lingual infections
2. Submandibular gland infections
3. Infections involving the parotid space
4. Spread from peritonsillar abscess
Submandibular space:
This is actually a combination of two spaces partially separated by the mylohyoid muscle. The space below the mylohyoid muscle is known as the submaxillary space while the space above the muscle is known as sublingual space.
Boundaries:
Superior – Oral mucosa and tongue
Medial – oral mucosa and tongue
Lateral – Superficial layer of deep cervical fascia with its tight attachment to the mandible and hyoid bone laterally
Inferior – Hyoid bone
The mylohyoid cleft separates the submaxillary from sublingual space. Structures passing through mylohyoid cleft include:
1. Wharton’s duct
2. Lingual nerve
3. Hypoglossal nerve
4. Branch of facial artery
5. Lymphatics
There is free communication across midline between these spaces. Ludwig’s angina is the characteristic example of infections of this space.
Masticator space:
This space is formed by the splitting of the superficial layer of deep cervical fascia as it encloses the mandible and the primary muscles of mastication.
Contents of this space include:
1. Masseter muscle
2. Medial & lateral pterygoid muscles
3. Ramus & posterior portion of the body of mandible
4. Insertion of the temporalis muscle
Supero medially this space communicates with the temporal space medial to the zygomatic arch. Infections involving this space involve the temporal space also. The most common cause of infection within this space is from abscessed third molar tooth.
Retropharyngeal space:
This space lies between the deep layer of the deep cervical fascia (prevertebral fascia) and the buccopharyngeal fascia superiorly and the fascia covering the oesophagus inferiorly. An ancillary portion of deep cervical fascia referred to as the alar layer extends from the base of skull to approximately the second thoracic vertebra at which point it fuses with that of the fascial covering of the oesophagus. The prevertebral fascia lies over the vertebra and the paraspinal muscles running from the base of the skull to the diaphragm. Thus there are two potential spaces in the retropharyngeal space. The first one lies between the fascia covering the pharynx and oesophagus and the alar layer of deep cervical fascia. This space is commonly referred to as the retropharyngeal / retrovisceral space. This space ends at the level of T2 vertebra. Lying posterior to the alar fascia but anterior to the prevertebral fascia is the danger space known as the prevertebral or Grodinsky space. This space allows wider spread of infections into the mediastinum. This space is commonly involved by rupture of retropharyngeal space abscesses.
Parotid space:
This space lies between the superficial and deep capsules of parotid gland. This is actually formed by splitting of the superficial layer of deep cervical fascia. The superficial capsule is very thick and strong and is closely adherent to the underlying parotid gland. Multiple septa could be seen running from the superficial capsule into the gland forming numerous intraglandular compartments. Infections of parotid gland cannot pierce the tough lateral capsule, instead they present medially with easy access to the lateral pharyngeal space. From the lateral pharyngeal space infections may progress to the retropharyngeal space. This is one of the most feared complication of parotid space infections.
