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X-ray anatomy of the nasal cavity and paranasal sinuses
Last reviewed: 19.10.2021
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The nasal cavity occupies a central position in the facial skull. It is divided in half by a septum made up by a vertical plate of the trellis and a vomer. The rear opening of the nasal cavity divides the opener into two parts - the choana. The anterior opening of the nasal cavity - the so-called pear-shaped opening - is formed by the bones of the upper jaw and is closed by the nasal bones on top. Around the nasal cavity there are paired paranasal, or accessory, sinuses. They communicate with the nasal cavity by means of passages or channels, lined with mucous membrane and under normal conditions are filled with air, as a result of which they are clearly visible on radiographs as light and clearly limited formations.
By the time of birth, the cells of the latticed labyrinth are formed in the fetus and there are small maxillary sinuses. Development of paranasal sinuses occurs mainly in the womb, mainly in the first 10-14 years, and is completed by 20-25 years.
Image of the nasal cavity and paranasal sinuses are obtained on radiographs and tomograms. Especially indicative are the tomograms produced at a small angle of swing of the X-ray tube (the so-called monograms). Radiographs and tomograms produce in the forward anterior and lateral projections. Usually, the study begins with a survey in the front of the chin projection. It has a pear-shaped opening, and the nasal cavity itself has the appearance of a triangular enlightenment, separated by a narrow vertical shadow of the bone septum. On either side of her, shadows of nasal conchae are prominent, and between them are light intervals of nasal passages.
Around the nasal cavity in the anterior and lateral shots and tomograms, the paranasal sinuses are determined. The frontal sinuses are located above the nasal cavity and eye sockets, projected onto the lower anterior sections of the scales of the frontal bone and are separated by the bone interstitial septum. In addition, each sinus can be divided into several cells by additional partitions. The dimensions of the frontal sinuses are very variable. In some cases, they are generally absent or very small, in others, on the contrary, they extend far to the sides, forming the supraorbital coves. Latticed cells are located on the sides of the nasal septum, somewhat protrude into the cavity of the orbit and enter the upper and middle nasal shells. On the front shots, the trellis cells are superimposed on the image of the main sinuses, but on the lateral shots are visible anterior to them, under the shadow of the perforated plate.
On the roentgenograms and tomograms, the maxillary (maxillary) sinuses most prominently located on the sides of the nasal cavity. Each of these sinuses in the foreground images causes clarification of approximately triangular shape with sharp outlines, and on the lateral shots - the enlightenment of an irregular quadrangular shape. In the anterior picture, in the upper part of the sinus, there is a slight enlightenment - a circular opening of the base of the skull. The sinus may not be completely separated by thin bony septa.
Methods of artificial contrasting of the paranasal sinuses have been developed. In particular, in the maxillary sinus, a contrast agent is injected by puncturing the outer wall of the nasal cavity in the lower nasal passage after preliminary anesthesia. This technique is called gaymorography, it is used for special indications in institutions where there is no computer tomograph, with differential diagnostics of polyposis sprouts, cysts and tumors. Computed tomography in recent years begins to play a big role in the study of paranasal sinuses, including with tumor lesions. Tomograms make it possible to determine the volume and prevalence of tumor formation and the state of surrounding tissues and cavities.