What Is a Sphenoid Sinus?

The sphenoidal sinus is located in the body of the sphenoid bone, deep below the base of the skull, and is divided into two cavities by the septum of sphenoidal sinus. Sphenoid sinus development is often different, and the sphenoid sinus septum is rarely centered, or even oblique, coronal, frontal, etc., so the size and shape of the sphenoid sinus cavity on both sides are mostly asymmetric.

Chinese name: Sphenoid sinus
Foreign name: sphenoidal sinus

Location: Sphenoid bone
Field: biological

Sphenoid sinus anatomy

The top wall and side wall of the sphenoid sinus are the middle skull base, and the anatomy of the important structures of the middle cranial fossa, such as the sphenoid saddle, internal carotid artery, cavernous sinus, optic nerve, and optic cross, and the III, IV, , and to the brain The relationship is extremely close. The variation of the development of the sphenoid sinus caused its adjacent relationship with the above structure and the final sieve room to change accordingly. Therefore, the sphenoid sinus and the base of the middle skull are the most dangerous areas for endoscopic sinus surgery.

The sphenoid sinus is located in the sphenoid bone, one behind the upper turbinate, one on the left and one on the left. After birth, there is only a small sphenoid sinus primordium. Development began at the age of 3 years, and the development on both sides was more symmetrical; most of them had developed at the age of 6, and the development on the sides was inconsistent at puberty; therefore, the shape and size of the sphenoid sinuses in adults were often different.

Adult sphenoid sinus: 20mm high, 18mm wide, 12mm long before and after. Volume: 7, 5 (5-30) ml.

Sphenoid sinus bone wall

Sphenoid sinus anterior wall

Tilt back and down slightly to form the posterior segment of the nasal cavity top and the posterior wall of the ethmoid sinus. The upper part of the anterior wall is thinner and connects with the bone at the base of the skull. The intersection is the site of cerebrospinal fluid nasal leakage. Most of them are accidentally inserted into the anterior cranial fossa when they enter the sphenoid sinus or they are forced to sprain when biting the anterior wall. Caused by. The medial boundary of the anterior wall is the sphenoid ridge, which connects the upper posterior edge of the nasal septum. The outer side of the anterior wall is the posterior wall of the final sieve room, which is the butterfly sieve plate.

Above the anterior wall of the sphenoid sinus, there is a natural opening of the sphenoid sinus near the nasal septum, which is open in the sphenoid crypt, which is an important sign of transsphenoidal sinus surgery and nasal endoscopic surgery. The bony sinus orifice is about 10 mm in diameter, but the mucosal sinus orifice is smaller, only 2 to 3 mm in diameter.

The sphenoid sinus opening is mostly located in the upper part of the anterior wall of the sphenoid sinus, which is basically symmetrical on both sides and has a figure-eight shape. The distance from the upper edge of the bony sphenoid sinus opening to the top of the sphenoid sinus is 3, 3 (0-11, 7) mm. The shortest distance from the margin to the sphenoid condyle is about 1, 4mm, and the shape of the opening varies. The oval shape is 34, 9% (Figure 4-95), and the round or kidney shape is 31, 9% (Figure 4-96). Crescent and bowstring shapes are 17, 3%, and those of triangles, spindles and fissures are 15, 9%. The wing tube is opened below the front wall.

Posterior wall of sphenoid sinus

The diaphragm is adjacent to the posterior cranial fossa, which is part of the skull base platform. The thickness of this bone wall is related to the development of the sphenoid sinus. If the sphenoid sinus is excessively vaporized, this wall can be very thin. The posterior superior is adjacent to the pontine and basilar artery.

Superior sphenoid sinus

The upper wall is part of the base of the middle cranial fossa. From front to back there is the sphenoid winglet root, the sphenoid plane and its two outer corners of the optic nerve hole. The most important adjacent structure of the top wall of the saddle is the saddle that supports the pituitary gland above it. There is a nodule in front of the saddle, and the protuberance behind the saddle is the anterior bed. The anterior bed process is directly in front of the optic cross, and both sides are close to the intracranial mouth of the optic nerve. Cavernous sinus is on both sides of the saddle. The top wall of the sphenoid sinus is the key structure of the intra-nasal sphenoid sinus approach to saddle surgery under endoscopy. Among the sphenoid sinuses with good gasification, such as semi-saddle type, full saddle type, or occipital saddle type, the saddle is semi-saddle type. Round, easy to identify, but in sphenoid sinuses with poor and poor gasification, such as pre-saddle type and parietal type, the above anatomical relationship will vary, and the sphenoid sinus cavity is completely in front of the saddle nodules and the saddle The bottom is not adjacent. For this sphenoid sinus, part of the sphenoid sinus posterior wall loosened bone should be excised to enlarge the sinus cavity and expose the sole of the saddle as much as possible. Otherwise, blindly opening the top wall may mistakenly enter the anterior cranial fossa, causing nasal leakage of cerebrospinal fluid or damage to the optic cross. In addition, since the cavernous sinus and internal carotid artery are also located on both sides of the saddle, surgery should not be extended to both sides. The upper wall is very thin, and the sphenoidal saddle and the optic canal often protrude into the sinus (Figure 4-97). Therefore, sphenoid sinusitis can be the cause of posterior optic neuritis, affecting vision, and even blindness on one or both sides.

Inferior sphenoid sinus

The bone is thicker and is the top of the nasopharynx. There is a longitudinal wing tube outside the wall, and the inner lining of the tube tube nerve. If the sphenoid sinus is over-developed downward, the canal can also protrude into the lower wall of the sphenoid sinus. When there is a bone defect, the inner canal nerve is exposed to the sinus, and inflammation can spread to the pterygopalatine fossa through the canal or the front of the vaporized wing The sphenopalatine ganglia causes sphenopalatine ganglia syndrome. The sphenoid sinus gasification spreads to the base of the posterior inferior occipital bone, which can be close to the pons, medulla oblongata, basal artery, lateral sinus, and inferior petrosal sinus.

Sphenoid sinus medial wall

The inner wall is the bony sphenoid sinus septum. The shape, size, thickness, location, and integrity of the sphenoid sinus septum are highly variable. 22% to 41% of the sphenoid sinus septum is located at the midline. According to the shape of the sphenoid sinus septum and the presence or absence of deflection, the sphenoid sinus septum was divided into sagittal median, S-shaped, C-shaped, slightly posterior, and deviated to the outer wall.

Most of the sphenoid sinus septum deviates from the midline when it passes through the sole of the saddle. The anterior part of the sphenoid sinus septum is sometimes located on the midline, while the posterior part is attached to the protrusion of the internal carotid artery, which is the front of the internal carotid artery sulcus. Therefore, the sphenoid sinus septum should never be used as a midline marker when performing intra-saddle surgery through the nasal sphenoid sinus. The sphenoid sinus septum can be similar to the presence of epiphyses in individual sphenoid sinus cavities, so that multiple crypts are formed in the sinus cavity, the so-called multisinus sphenoid sinus. It is worth mentioning that the septum of the individual sphenoid sinus or the bone in the sinus cavity The ridge is horizontal, and it is easy to mistake it as the sole of the saddle during the intrasphenoidal sinus surgery. Only after removing it can the sole of the saddle be exposed.

Lateral sphenoid sinus

The lateral wall of the sphenoid sinus is part of the middle cranial fossa, which is adjacent to the cavernous sinus, internal carotid artery, ophthalmic artery, and brain nerves II, III, IV, V, and VI. A small vein passes through this wall and communicates with the cavernous sinus. Therefore, sphenoid sinus infection can invade the cavernous sinus and nearby cerebral nerves, embolism, meningitis, eye muscle paralysis, and trigeminal neuralgia.

The anatomy of the lateral wall of the sphenoid sinus is important and complex. The outer wall of the sphenoid sinus is thin. If the gasification is excessive, the outer wall is often thin and even congenital. The above important structure can be exposed inside the sinus cavity, and it is the most dangerous anatomical variation in major complications such as blindness and major bleeding.

Sphenoid sinus related diseases and treatment

1. Classification of sphenoid sinus diseases According to the origin and location of sphenoid sinus diseases and the invasion of the structures around the sphenoid sinuses, we divide the sphenoid sinus diseases into the following three categories: 1. Solitary sphenoid sinus disease: refers to the primary origin of the sphenoid sinus disease. And the disease confined to the sphenoid sinus did not invade surrounding adjacent structures. We have noticed that there are no reports on "Isolated" sphenoid sinus reports in the literature. Some sphenoid sinus diseases are not confined to the sphenoid sinus, but have different degrees of contradiction. Invasion of surrounding structures, for example, sphenoid sinus foreign body and sphenoid sinus cerebrospinal fluid nasal leakage due to trauma or surgery, although there is damage to the sphenoid sinus bone wall, but because there is no violation of the surrounding structure, it is still classified as a sphenoid sinus disease. More reasonable. 2. Invasive sphenoid sinus disease: The lesion originates in or near the sphenoid sinus. In addition to involving the sphenoid sinus, there are still violations of adjacent structures. For example, a giant sphenoid sinus mucus cyst can invade the eye socket and compress the optic nerve to cause blindness. . Imaging examination can reveal different degrees of damage to the sphenoid sinus bone wall. 3. Metastatic sphenoid sinus disease: refers to the malignant tumors of other parts of the body that have metastasized to the sphenoid sinus and show corresponding symptoms.

2. The significance of sphenoid sinus disease classification in diagnosis

Solitary sphenoid sinus disease and invasive sphenoid sinus disease can be manifested as headache, eye and cranial nerve symptoms, and nasal symptoms. Once the symptoms of the eye and cranial nerves appear, it often indicates that the lesion has invaded the surrounding structure, so the diagnosis of sphenoid sinus disease should not only clarify the nature of the lesion, but also understand the scope of the lesion and its surrounding structures in detail. CT can be used as the method of choice for the diagnosis of sphenoid sinus disease. Peripheral structures that can be affected by sphenoid sinus disease include: ethmoid sinus, nasal cavity, dorsal and sphenoid sinus top wall, slope, side of sphenoid sinus and parasaddle, anterior skull base, optic nerve, nasopharynx, forehead, intracranial, intraorbital , Internal carotid artery, saddle nodule, middle cranial fossa, pterygium. Before the advent of nasal endoscopy, the surgical methods adopted for the treatment of sphenoid sinus lesions were: nasal incision, extranasal ethmoid sinus approach, intranasal approach, transnasal septum approach, combined nose-to-nose approach, and cranial-nasal approach. Disadvantages of these surgical approaches include perforation of the nasal septum, reduced incisor sensation after surgery, scar formation on the face, and prolonged hospital stay. We think that for sphenoid sinus inflammation, cysts, polyps, cerebrospinal fluid rhinorrhea and other isolated diseases, nasal endoscopic surgery should be preferred. For invasive sphenoid sinus disease, in designing a treatment plan, in addition to considering the nature of the disease, it is necessary to read the image data to understand the extent of lesion invasion in detail and choose the appropriate treatment.