The danger space or alar space, is a region of the neck.
The common name originates from the risk that an
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
in this space can spread directly to the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
, and, due to being a space continuous on the left and right, can furthermore allow infection to spread easily to either side.
Structure
It is bounded at the top by the
skull base
The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria.
Structure
Structures found at the base of the skull are for ...
, at the front by the
alar fascia
The alar fascia is a layer of fascia, sometimes described as part of the prevertebral fascia, and sometimes as in front of it.
Anatomy
Cranially, it reaches the skull, and caudally, it reaches the second thoracic vertebra.
In 2015, the anatomy ...
and behind by the
prevertebral fascia
The prevertebral fascia (or prevertebral layer of cervical fascia) is a fascia in the neck.
Variations
In some literature, the prevertebral fascia also includes the other fascial layers extending around the vertebral column and enclosing all musc ...
. It comes to an end at the level of the diaphragm.
The
retropharyngeal space
The retropharyngeal space (abbreviated as "RPS") is a potential space and deep compartment of the head and neck situated posterior to the pharynx. The RPS is bounded anteriorly by the buccopharyngeal fascia, posteriorly by the alar fascia, and la ...
is found anterior to the danger space, between the alar fascia and
buccopharyngeal fascia
The buccopharyngeal fascia is a fascia in the head and neck.
Structure
The buccopharyngeal runs parallel to the medial aspect of the carotid sheath. It is a thin lamina given off from the pretracheal fascia.
It is attached to the prevertebral f ...
. There exists a midline raphe in this space so some infections of this space appear unilateral.
Clinical significance
On
CT or
MRI
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
it is only visible when distended by fluid or pus, below the level of T1-T6, as the retropharyngeal space ends at this level, allowing distinction between the two entities. Superior spread of infection can affect the contents of the
carotid sheath
The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adip ...
, including the
internal jugular vein
The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve.
It begins in the posteri ...
and cranial nerves IX, X, XI, and XII, while inferior spread of infection through the danger space can cause
mediastinitis
Mediastinitis is inflammation of the tissues in the mid-chest, or mediastinum. It can be either Acute (medical), acute or Chronic (medical), chronic. It is thought to be due to four different etiologies:
* direct contamination
* hematogenous or Ly ...
.
History
It was first characterized in 1938.
[Grodinsky M, Holyoke EA. The fasciae and fascial spaces of the head, neck and adjacent regions. Am J Anat 1938;63:367-408.]
See also
*
Retrovisceral space
References
External links
* https://web.archive.org/web/20070319235431/http://www.bcm.edu/oto/grand/10694.html
{{Digestive tract
Human head and neck