Maxillary sinus

Maxillary sinus . Known as Highmore’s Antrum, it is one of the cavities that make up the paranasal sinuses on the face , of which it is the largest cavity and is pyramidal in shape.

Summary

[ disguise ]

• 1 Anatomy
• 2 Location
• 3 Physiology
• 4 Development
• 5 Irrigation
• 6 Related diseases
  • 1 Maxillary sinus lift
  • 2 Cysts in the maxillary sinus
• 7 Sources

Anatomy

The floor of the maxillary sinus remains in close relationship with the apices of the upper molars and premolars, which are separated from the sinus cavity by a thin layer of 5 to 8 mm, although they may be in direct contact in cases of severe resorption.

The upper wall is made up of the orbital floor; The anterior wall is made up of the facial surface of the upper jaw bone behind the canine eminence; the posterior wall corresponds to the anterior wall of the pterygo-maxillary fossa; The lower wall is made up of the alveolar and palatine processes of the maxillary bone, located below the floor level of the nasal passages for a variable distance that can be up to 10 mm.

The drainage system is located on the antero-superior aspect of the medial wall and is made up of an ostium and an infundibulum 7-10 mm long and several millimeters in diameter. This set of structures is called the osteomeatal unit, and it connects the maxillary sinus with the nasal cavity at the level of the middle meatus.

Location

It is located in the maxillary bone on each side of the nasal passages and below the eye socket .

Physiology

It is covered on the inside by a mucosa , called Schneider’s membrane. It is a pneumatic cavity, that is, a hollow cavity. It is usually located above the dental roots of the molars and premolars of the upper jaw , supporting the floor of the sinus as if it were the central rod of a tent.

Development

It originates in the third month of embryonic development from a lateral outpouching of the epithelium of the middle nasal meatus. Before birth, a second pneumatization process occurs. In the newborn, it persists as a small lateronasal cavity, located above the bud of the first decidual molar.

During childhood, it undergoes a gradual expansion that is related to the pressure exerted by the eyeball , the tension of the superficial facial muscles, the soft palate and the masticatory muscles , the intra-estrasinusal differential pressure and dental eruption.

The greatest development of the antrum coincides with the eruption of the permanent dentition, reaching its maximum pneumatization with the eruption of the third molars or wisdom teeth, at 16-21 years of age.

In the adult individual, the maxillary sinus has the shape of a quadrangular pyramid that occupies the central part of the pyramidal process of the upper jaw bone, whose base is constituted by the lateral nasal wall and whose apex is oriented to the zygomatic process.

Irrigation

It comes from branches of the facial, internal maxillary, infraorbital, sphenopalatine and greater palatine arteries. Venous drainage is directed primarily towards the pterygoid plexus and the facial vein.

Lymphatic drainage is carried out through the face, towards the submandibular lymph node collectors. The innervation comes from the branches of the second division of the trigeminal nerve through the posterior, middle and anterior dental nerves, greater palatine nerve and infraorbital nerve.

Related diseases

Maxillary sinus lift

Air circulates through the maxillary sinus when breathing, subject to positive and negative pressure (inspiration, expiration); The tooth roots being the ones that maintain balance. When teeth are lost, this balance is broken; the positive pressure being greater than the negative; and that is when the sinus begins to descend; This process is called pneumatization. This process results in a decrease or disappearance of the maxillary bone available for the placement of implants.

To solve this problem, a surgical technique called maxillary sinus floor elevation, or better known as simply sinus lift, is used . This consists of the creation of a small window in the lateral wall, allowing access to the sinus, subsequent elevation of the membrane and filling the space with the patient’s own bone or biomaterial.

Sinus lift is a very predictable technique that allows us to solve most cases, even those with severe resorption. It is a clean and simple technique that is easy to perform when you have the necessary surgical knowledge and skill.

Cysts in the maxillary sinus

A cyst is a small bump or bag that forms in the cavities of the cheekbones based on fluids and other substances when a duct in this area is blocked. It can be right, left or bilateral.

The vast majority of maxillary sinus cysts are found accidentally in radiological, tomographic or magnetic resonance studies that the patient had at the request of an otorhinolaryngologist, neurologist, neurosurgeon or dentist. The vast majority of these cysts do not represent a problem in themselves and are just “findings.” Other times they must be studied and treated, depending on the case.

There are several types of cysts and they are the following:

• Mucous retention cyst: This type of cysts in the maxillary sinuses are secretory type. They occur when the duct of a gland containing viscous fluid is partially blocked. When the layer covering secretory cysts breaks, the mucosa infects neighboring tissues.
• Non-secretory cysts: They are simply an inflammation in the tissue derived from an infection or allergy .
• Maxillary mucoceles: They are benign cysts of the maxillary sinuses with retention of mucous secretion. Its wall is made up of mucosa and its content is a thick liquid. In the sinuses, an increase in pressure occurs and therefore the dilation of its wall.

These cysts are usually found casually in radiological studies, MRIs, etc. at the request of an ENT, laryngologist , neurologist or dentist . In any case, they do not usually pose a serious problem.

Mucous cysts of the maxillary sinus are benign and there is no possibility of them transforming into any type of malignant tumor (or cancer). Mostly with imaging studies it is possible to clearly elucidate what type of cyst it is. If there are diagnostic doubts about whether it is really a simple maxillary sinus cyst, a clarifying biopsy can be used. This situation is very rare in current medicine.