| Danger space | |
|---|---|
 Section of the neck at about the level of the sixth cervical vertebra. Showing the arrangement of the fascia coli. | |
| Anatomical terminology |
The danger space or alar space, is a region of the neck. [1] The common name originates from the risk that an infection in this space can spread directly to the thorax, and, due to being a space continuous on the left and right, can furthermore allow infection to spread easily to either side.
It is bounded at the top by the skull base, at the front by the alar fascia and behind by the prevertebral fascia. It comes to an end at the level of the diaphragm.
The retropharyngeal space 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 retropharyngeal space drains into the superior mediastinum, whereas the danger space drains into the posterior mediastinum.
On CT or MRI 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. [2] Superior spread of infection can affect the contents of the carotid sheath, including the internal jugular vein and cranial nerves IX, X, XI, and XII, while inferior spread of infection through the danger space can cause mediastinitis.
The thoracic cavity is the chamber of the body of vertebrates that is protected by the thoracic wall. The central compartment of the thoracic cavity is the mediastinum. There are two openings of the thoracic cavity, a superior thoracic aperture known as the thoracic inlet and a lower inferior thoracic aperture known as the thoracic outlet.
The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong inelastic connective tissue, and an inner layer made of serous membrane. It encloses the pericardial cavity, which contains pericardial fluid, and defines the middle mediastinum. It separates the heart from interference of other structures, protects it against infection and blunt trauma, and lubricates the heart's movements.
In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. The thoracic duct usually begins from the upper aspect of the cisterna chyli, passing out of the abdomen through the aortic hiatus into first the posterior mediastinum and then the superior mediastinum, extending as high up as the root of the neck before descending to drain into the systemic (blood) circulation at the venous angle.
The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches. There are also two other types of salivary glands; they are submandibular and sublingual glands. Sometimes accessory parotid glands are found close to the main parotid glands.
The mediastinum is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is an undelineated region that contains a group of structures within the thorax, namely the heart and its vessels, the esophagus, the trachea, the phrenic and cardiac nerves, the thoracic duct, the thymus and the lymph nodes of the central chest.
The mylohyoid muscle or diaphragma oris is a paired muscle of the neck. It runs from the mandible to the hyoid bone, forming the floor of the oral cavity of the mouth. It is named after its two attachments near the molar teeth. It forms the floor of the submental triangle. It elevates the hyoid bone and the tongue, important during swallowing and speaking.
The pyramid-shaped maxillary sinus is the largest of the paranasal sinuses, located in the maxilla. It drains into the middle meatus of the nose through the semilunar hiatus. It is located to the side of the nasal cavity, and below the orbit.
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, and ansa cervicalis. The carotid sheath helps protects the structures contained therein.
Mediastinitis is inflammation of the tissues in the mid-chest, or mediastinum. It can be either acute or chronic. It is thought to be due to four different etiologies:
Ventriculitis is the inflammation of the ventricles in the brain. The ventricles are responsible for containing and circulating cerebrospinal fluid throughout the brain. Ventriculitis is caused by infection of the ventricles, leading to swelling and inflammation. This is especially prevalent in patients with external ventricular drains and intraventricular stents. Ventriculitis can cause a wide variety of short-term symptoms and long-term side effects ranging from headaches and dizziness to unconsciousness and death if not treated early. It is treated with some appropriate combination of antibiotics in order to rid the patient of the underlying infection. Much of the current research involving ventriculitis focuses specifically around defining the disease and what causes it. This will allow for much more advancement in the subject. There is also a lot of attention being paid to possible treatments and prevention methods to help make this disease even less prevalent and dangerous.
The retropharyngeal space 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 laterally by the carotid sheath. It extends between the base of the skull superiorly, and the mediastinum inferiorly. It contains the retropharyngeal lymph nodes. Its function is to facilitate movements in the superoinferior axis of the larynx, pharynx, and esophagus in relation to the cervical spine.
Atlanto-occipital dislocation, orthopedic decapitation, or internal decapitation describes ligamentous separation of the spinal column from the skull base. It is possible for a human to survive such an injury; however, 70% of cases result in immediate death. It should not be confused with atlanto-axial dislocation, which describes ligamentous separation between the first and second cervical vertebra.
The prevertebral fascia is the layer of deep cervical fascia that surrounds the vertebral column. It is the deepest layer of deep cervical fascia.
The buccopharyngeal fascia is a fascia of the pharynx. It represents the posterior portion of the pretracheal fascia. It covers the superior pharyngeal constrictor muscles, and buccinator muscle.
The retropharyngeal lymph nodes, from one to three in number, lie in the buccopharyngeal fascia, behind the upper part of the pharynx and in front of the arch of the atlas, being separated, however, from the latter by the Longus capitis.
The retrovisceral space is divided into the retropharyngeal space and the danger space by the alar fascia. It is of particular clinical importance because it is a main route by which oropharyngeal infections can spread into the mediastinum.
Retropharyngeal abscess (RPA) is an abscess located in the tissues in the back of the throat behind the posterior pharyngeal wall. Because RPAs typically occur in deep tissue, they are difficult to diagnose by physical examination alone. RPA is a relatively uncommon illness, and therefore may not receive early diagnosis in children presenting with stiff neck, malaise, difficulty swallowing, or other symptoms listed below. Early diagnosis is key, while a delay in diagnosis and treatment may lead to death. Parapharyngeal space communicates with retropharyngeal space and an infection of retropharyngeal space can pass down behind the esophagus into the mediastinum. RPAs can also occur in adults of any age.
The alar fascia a portion or prevertebral fascia that may or may not be considered a distinct anatomical structure. When acknowledged, it is described as anterior to the prevertebral fascia.
The prevertebral space is a space in the neck.
The parapharyngeal space, is a potential space in the head and the neck. It has clinical importance in otolaryngology due to parapharyngeal space tumours and parapharyngeal abscess developing in this area. It is also a key anatomic landmark for localizing disease processes in the surrounding spaces of the neck; the direction of its displacement indirectly reflects the site of origin for masses or infection in adjacent areas, and consequently their appropriate differential diagnosis.
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