Maxillary sinus

Maxillary sinus

Outline of bones of face, showing position of air sinuses. Maxillary sinus is shown in blue.

Left maxilla, medial view. Maxillary sinus shown in red.
Details
Artery infraorbital artery, posterior superior alveolar artery
Nerve posterior superior alveolar nerve, middle superior alveolar nerve, anterior superior alveolar nerve, and infraorbital nerve
Identifiers
Latin sinus maxilliaris
MeSH A04.531.621.578
TA A06.1.03.002
A02.1.12.023
FMA 57715

Anatomical terminology

The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose.[1]

Structure

It is the largest air sinus in the body. Found in the body of the maxilla, this sinus has three recesses: an alveolar recess pointed inferiorly, bounded by the alveolar process of the maxilla; a zygomatic recess pointed laterally, bounded by the zygomatic bone; and an infraorbital recess pointed superiorly, bounded by the inferior orbital surface of the maxilla. The medial wall is composed primarily of cartilage. The ostia for drainage are located high on the medial wall and open into the semilunar hiatus of the lateral nasal cavity; because of the position of the ostia, gravity cannot drain the maxillary sinus contents when the head is erect (see pathology). The ostium of the maxillary sinus is high up on the medial wall and on average is 2.4 mm in diameter; with a mean volume of about 10 ml.[1][2] Stand near the person during an extraoral examination to visually inspect and bilaterally palpate the maxillary sinuses.[3]

The sinus is lined with mucoperiosteum, with cilia that beat toward the ostia. This membrane is also referred to as the "Schneiderian Membrane", which is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the osseous side. The size of the sinuses varies in different skulls, and even on the two sides of the same skull.[2]

The infraorbital canal usually projects into the cavity as a well-marked ridge extending from the roof to the anterior wall; additional ridges are sometimes seen in the posterior wall of the cavity and are caused by the alveolar canals.

The mucous membranes receive their postganglionic parasympathetic nerve innervation for mucous secretion originating from the greater petrosal nerve (a branch of the facial nerve). The superior alveolar (anterior, middle, and posterior) nerves, branches of the maxillary nerve provide sensory innervation.

Nasal wall/base

Its nasal wall, or base, presents, in the disarticulated bone, a large, irregular aperture, communicating with the nasal cavity.

In the articulated skull this aperture is much reduced in size by the following bones:

The sinus communicates through an opening into the semilunar hiatus on the lateral nasal wall.

Posterior wall

On the posterior wall are the alveolar canals, transmitting the posterior superior alveolar vessels and nerves to the molar teeth.

Floor

The maxillary sinus can normally be seen above the level of the premolar and molar teeth in the upper jaw. This dental x-ray film shows how, in the absence of the second premolar and first molar, the sinus became pneumatized and expanded towards the crest of the alveolar process (location at which the bone meets the gum tissue).

The floor is formed by the alveolar process of the maxilla, and, if the sinus is of an average size, is on a level with the floor of the nose; if the sinus is large it reaches below this level.

Projecting into the floor of the antrum are several conical processes, corresponding to the roots of the first and second maxillary molar teeth; in some cases the floor can be perforated by the apices of the teeth.

Roof

The roof is formed by floor of the orbit. It is traversed by infraorbital nerves and vessels.

Development

It is present at birth as rudimentary air cells, and develops throughout childhood.

Clinical significance

Maxillary sinusitis

Maxillary sinusitis is inflammation of the maxillary sinuses. The symptoms of sinusitis are headache, usually near the involved sinus, and foul-smelling nasal or pharyngeal discharge, possibly with some systemic signs of infection such as fever and weakness. The skin over the involved sinus can be tender, hot, and even reddened due to the inflammatory process in the area. On radiographs, there is opacification (or cloudiness) of the usually translucent sinus due to retained mucus.[3]

Maxillary sinusitis is common due to the close anatomic relation of the frontal sinus, anteriorethmoidal sinus and the maxillary teeth, allowing for easy spread of infection. Differential diagnosis of dental problems needs to be done due to the close proximity to the teeth since the pain from sinusitis can seem to be dentally related.[1] Furthermore, the drainage orifice lies near the roof of the sinus, and so the maxillary sinus does not drain well, and infection develops more easily. The maxillary sinus may drain into the mouth via an abnormal opening, an oroantral fistula, a particular risk after tooth extraction.

Sinusitis treatment

Traditionally the treatment of acute maxillary sinusitis is usually prescription of a broad-spectrum cephalosporin antibiotic resistant to beta-lactamase, administered for 10 days. Recent studies have found that the cause of chronic sinus infections lies in the nasal mucus, not in the nasal and sinus tissue targeted by standard treatment. This suggests a beneficial effect in treatments that target primarily the underlying and presumably damage-inflicting nasal and sinus membrane inflammation, instead of the secondary bacterial infection that has been the primary target of past treatments for the disease. Also, surgical procedures with chronic sinus infections are now changing with the direct removal of the mucus, which is loaded with toxins from the inflammatory cells, rather than the inflamed tissue during surgery. Leaving the mucus behind might predispose early recurrence of the chronic sinus infection. If any surgery is performed, it is to enlarge the ostia in the lateral walls of the nasal cavity, creating adequate drainage.[3]

Cancer

Carcinoma of the maxillary sinus may invade the palate and cause dental pain. It may also block the nasolacrimal duct. Spread of the tumor into the orbit causes proptosis.[1]

Age

With age, the enlarging maxillary sinus may even begin to surround the roots of the maxillary posterior teeth and extend its margins into the body of the zygomatic bone. If the maxillary posterior teeth are lost, the maxillary sinus may expand even more, thinning the bony floor of the alveolar process so that only a thin shell of bone is present.[3]

History

The maxillary sinus was first discovered and illustrated by Leonardo da Vinci, but the earliest attribution of significance was given to Nathaniel Highmore, the British surgeon and anatomist who described it in detail in his 1651 treatise.[4]

Additional Images

See also

This article uses anatomical terminology; for an overview, see Anatomical terminology.

References

  1. 1 2 3 4 Human Anatomy, Jacobs, Elsevier, 2008, page 209-210
  2. 1 2 Bell, G.W., et al. Maxillary sinus disease: diagnosis and treatment, British Dental Journal 210, 113 - 118 (2011) at http://www.nature.com/bdj/journal/v210/n3/full/sj.bdj.2011.47.html
  3. 1 2 3 4 Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 67
  4. ↑ Merriam-Webster's Medical Desk Dictionary Revised Ed. 2002, pg 49.

External links

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