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 tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

in this space can spread directly to the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of 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 di ...

, 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 Anatomical terms of location#Superior and inferior, inferior area of the human skull, skull. It is composed of the endocranium and the lower parts of the Calvaria ...

, at the front by the alar fascia and behind by the

prevertebral fascia The prevertebral fascia (also known as prevertebral layer of cervical fascia or vertebral fascia) is the layer of deep cervical fascia that surrounds the vertebral column. It is the deepest layer of deep cervical fascia. It encloses the sympathet ...

. 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 l ...

is found anterior to the danger space, between the alar fascia and buccopharyngeal fascia. There exists a midline raphe in this space so some infections of this space appear unilateral. The

drains into the superior mediastinum, whereas the danger space drains into the posterior mediastinum.

Clinical significance

On CT or

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and rad ...

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 a condensation of the deep cervical fascia enveloping multiple vital neurovascular structures of the neck, including the common and internal carotid arteries, the internal jugular vein, the vagus nerve (CN X), and ansa c ...

, 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.

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.

References

External links

* https://web.archive.org/web/20070319235431/http://www.bcm.edu/oto/grand/10694.html {{Digestive tract Human head and neck

Structure

Clinical significance

History

See also

References

External links