Mucoceles of the sinuses: causes, symptoms, diagnosis, treatment

Mucocele of the paranasal sinuses is a unique retention saccular cyst of one paranasal sinus, formed as a result of obliteration of the nasal excretory duct and accumulation of mucous and hyaline secretions inside the sinus, as well as elements of epithelial desquamation.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ]

Epidemiology

Mucocele of the paranasal sinuses is a rare disease that occurs in both women and men, in the latter more often in the interval between 15 and 25 years. Very rarely, mucocele of the paranasal sinuses occurs in people under 10 and after 45 years of age. Most often, mucocele of the paranasal sinuses is localized in the frontal sinus, then in the ethmoid labyrinth or on the border between them, which often leads to penetration of the "cyst" into the eye socket, causing exophthalmos - a fact that explains its frequent detection by an ophthalmologist. Very rarely, mucocele is localized in the sphenoid and maxillary sinuses. But odontogenic cysts are often localized in the latter.

Causes sinus mucocele

Obvious causes of mucocele of the paranasal sinuses are obstruction of the excretory ducts, which occurs as a result of either an inflammatory process, or the influence of osteoma or the consequences of trauma. Contributing factors may be various anomalies in the development of the facial skeleton, including the paranasal sinuses. The absence of the drainage function of the sinus and the accumulation of mucus and its decay products in it, the absence of an oxygen environment, which is so necessary for the normal functioning of the mucous membrane of the sinus and its glandular elements, leads to the formation of catabolites with toxic properties, increasing the activity of osteoclasts and irritating the nerve endings of the VNS, which increases the activity of the mucous glands, causing increased secretion. The resulting vicious circle contributes to the development of chronic aseptic inflammation of the mucocele, and its infection - to acute empyema of the sinus. Thus, the progressive accumulation of waste products of the mucous membrane of the sinus and its glandular elements leads to an increase in pressure on its mucous membrane and bone walls, their atrophy, thinning and the formation of a erosion, through which the mucocele penetrates into adjacent cavities and anatomical formations.

Pathogenesis

Pathogenesis of mucocele of the paranasal sinuses. In the pathogenesis of mucocele of the paranasal sinuses, different authors considered different "theories" of its occurrence:

1. The "monoglandular theory" explains the occurrence of mucocele by the blockage of one mucous gland, which results in its expansion, proliferation of the epithelial layer and the formation of a mucous sac;
2. "morphogenetic theory" appeals to congenital disruption of the development of the cells of the ethmoid labyrinth, by analogy with odontogenic cysts;
3. The "compression theory" favors the banal blockage of the excretory ducts, the formation of aggressive mucocele contents and the activation of osteoclasts, which lead to bone destruction.

Pathological anatomy of mucocele of the paranasal sinuses. Histological studies have shown that as a result of the formation of a mucocele, the ciliated columnar epithelium is transformed into a multilayered flat epithelium, devoid of the ciliary apparatus. When the cystic formation exits the sinus into the surrounding soft tissues, its membrane is covered with a fibrous layer on the outside. The contents of the mucocele have a viscous gelatin-like consistency, are yellowish-white in color, aseptic, and have no odor. The bone walls atrophy and become thinner, acquiring the appearance of parchment paper, then are resorbed with the formation of a defect. Osteoclasts predominate in the bone tissue.

Symptoms sinus mucocele

The development of mucocele of the paranasal sinuses is very slow and goes through three periods:

1. latent period;
2. the period of exterritorialization, i.e. the exit of the cyst beyond the sinus;
3. period of complications.

The latent period is completely asymptomatic, without any subjective or objective signs. In rare cases, periodic unilateral rhinorrhea appears, which is caused by a temporary opening of the frontonasal canal or a breakthrough of the mucous contents of the cyst through the openings that communicate the cells of the ethmoid labyrinth with the nasal cavity. If the cyst becomes infected during this period, the clinical course takes on the course of ordinary acute purulent sinusitis.

The period of exterritorialization is characterized by subjective and objective symptoms. With frontal localization of mucocele, various eye symptoms most often occur, since with this localization in the overwhelming majority of cases the cyst prolapses into the orbit. In this case, the patient and others around him notice swelling in the upper inner region of the orbit, after which, after some time, diplopia appears, indicating the compressive effect of the mucocele on the eyeball. When the cyst spreads to the posterior pole of the eyeball, pressure occurs on the optic nerves, which causes a decrease in visual acuity and the occurrence of peripheral scotoma of this eye. When the cyst spreads forward and downward, epiphora occurs as a result of dysfunction of the lacrimal ducts. With further development of the process, neuralgic pain occurs as a result of compression of the sensory nerves of the first vegvi of the trigeminal nerve by the cyst, which can radiate to the orbit, upper jaw and teeth of the corresponding side.

The swelling that has developed is smooth and dense to the touch, creating the impression of being one whole with the bone surrounding it. With significant thinning of the bone above it, the phenomenon of crepitus is possible, and if a defect is formed in the bone, its edges are uneven, scalloped and bent outward. In most cases, anterior rhinoscopy does not reveal any changes. Sometimes, with significant downward prolapse of the cyst, a swelling can be seen in the middle nasal passage, covered with normal mucous membrane, pushing the middle nasal concha toward the nasal septum.

The period of complications is characterized by various secondary pathological manifestations.

Diagnostics sinus mucocele

The diagnosis in the latent period can be made only by chance during an X-ray examination of the skull, conducted for some other reason. The changes in the paranasal sinuses detected in this period do not, for the most part, provide direct indications of the presence of mucocele; only an experienced radiologist can suspect the presence of a volumetric process in the sinus (most often in the frontal sinus) by such signs as its total shading or the presence of a rounded shadow, an unusually large sinus, thinning and rarefaction of its walls, and displacement of the intersinus septum beyond the median plane. Sometimes, in this period, the contours of the affected sinus are erased and unclear. Sometimes, a downward displacement of the frontal sinus is determined, into the area of the ethmoid labyrinth. However, all these signs may not be taken into account if the purpose of the X-ray examination is, for example, the contents of the skull, and may be interpreted as an “individual variant of the norm”, especially when any neurological symptoms are observed indicating a brain disease, distracting the doctor from assessing the condition of the nasal cavity.

During the period of mucocele exterritorialization, based only on the signs described above, the diagnosis of "mucocele" may appear only as one of the versions of the existing disease. Among other versions, the presence of a primary congenital orbital cyst, such as a dermoid cyst, meningocele, encephalocele or some neoplasm, is not excluded. In this case, the final diagnosis (not always!) can be established only as a result of an X-ray (CT, MRI) examination.

In the vast majority of cases of frontal sinus mucocele, destructive bone changes occur in the superomedial angle of the orbit and its upper wall, which are radiographically manifested by the presence of a homogeneous, oval shadow with smooth contours extending beyond the sinus, interruption of the orbit contours and bone destruction (bone tissue resorption) in the area of the lacrimal bone. At the same time, the cyst can penetrate into the anterior cells of the ethmoid labyrinth and, destroying the medial part of the upper wall of the maxillary sinus, penetrate into this sinus.

However, most often, the mucocele of the ethmoid labyrinth extends towards the orbit, squeezing the paper plate into it and destroying this bone. Localization of mucocele in the sphenoid sinus most often, in its clinical manifestations concerning visual disorders, simulates a tumor of the skull base or ethmoid labyrinth, or cystic arachnoiditis in the area of the optic chiasm. In this case, a thorough X-ray (including CT) examination or MRI allows establishing a definitive diagnosis of mucocele. Radiologically, mucocele of the sphenoid sinus is manifested by an increase in the volume of the sinus, the presence of a homogeneous shadow, foci of resorption and thinning of the sinus walls, including the intersinus septum.

Differential diagnosis

Differential diagnostics are performed with osteoma in the initial stage of mucocele exterritorialization, when the latter is still covered by a thin layer of softened bone, squeezed into the orbit, ethmoid labyrinth or maxillary sinus. At this stage, mucocele should also be differentiated from osteosarcoma, syphilitic osteoperiostitis or gumma, primarily localized in this area. During the period of mucocele exterritorialization, it is differentiated from a congenital orbital cyst, for example, from a dermoid cyst or mucocele and encephalocele, localized in the same places where mucocele usually manifests itself.

Meningocele is characterized by protrusion of the meninges beyond the cranium, forming a herniated sac filled with cerebrospinal fluid. This sac then gradually fills with brain matter, forming an encephalocele. Meningocele is usually located in the midline, occupying the frontal-interorbital space, which distinguishes it from mucocele of the frontal sinus. Radiographically, meningocele is visualized as a low-intensity shadow located at the root of the nose. Occurring immediately after birth, mucocele deforms the bone tissues in the frontal-ethmoid-nasal region as it grows, so on radiographs taken in the supraorbito-frontal projection, the space between the orbits is visualized as significantly expanded. Due to its localization, the mucocele covers the superomedial contours of the orbit, deforms its walls and pushes the eyeball forward, downward and to the side, thereby causing exophthalmos and diplopia. In the frontal-nasal projection, the hernial opening appears on the radiograph as a significantly widened dehiscence with smoothed contours.

Complications of mucocele are divided into inflammatory and mechanical. When a mucocele becomes infected, a pyocele is formed, which results in a modification of the radiographic picture: more significant bone destruction occurs, which increases those that occurred with the previous uninfected mucocele. In addition, the inflammatory process can spread to adjacent sinuses and tissues, causing empyema.

In some cases, suppuration of the mucocele leads to the formation of an external fistula, most often in the area of the upper internal angle of the orbit. If the bone erosion occurs in the area of the posterior wall of the frontal sinus, the inflammatory process spreads to the anterior cranial fossa, causing one or several intracranial complications at once: extra- or subdural abscess, purulent meningitis or meningoencephalitis, brain abscess or thrombosis of the superior sagittal or cavernous sinus.

Mechanical complications are caused by the pressure of the mucocele, which it exerts on the anatomical structures that are in direct contact with it. Compression of these structures leads to their atrophy and degeneration (formation of erosions in bone tissue, degenerative-dystrophic changes in the paranasal sinuses, desolation of blood vessels with disruption of the nutrition of the corresponding structures, trigeminal neuralgia, etc.), and the constant pressure of the growing mucocele on the eyeball or lacrimal organs leads to their displacement, deformation and dysfunction (lacrimation, secondary dacryocystitis, diplopia, epiphora, etc.). As V. Racovenu (1964) notes, these mechanical complications often lead to or are accompanied by an abscess or phlegmon of the orbit, panophthalmitis, etc.

Treatment sinus mucocele

Treatment of mucocele is only surgical. It is usually recommended to perform RO on the frontal sinus with complete curettage of the mucous membrane and removal of the mucous sac, motivating this approach with the fear that the remaining parts of the mucous membrane and their glandular apparatus can lead to a relapse of mucocele. It is also recommended to create a wide drainage of the sinus with the nasal cavity at the site of the obliterated frontonasal canal. However, as the experience of a number of domestic and foreign authors has shown, excessive radicalism in surgical intervention for mucocele of the frontal sinus does not justify itself. It is sufficient only to remove the saccular cyst formation and form a wide junction of the sinus with the nasal cavity by the endonasal method, while, on the one hand, there is no need for total curettage of the mucous membrane of the sinus, on the other hand, endonasal opening of the ethmoid labyrinth with drainage and aeration of the postoperative cavity is mandatory.

If the mucocele develops only in the ethmoid labyrinth and prolapses into the nasal cavity without penetrating into the frontal sinus and especially into the orbit, then they limit themselves to opening the cells of the ethmoid labyrinth through the bulla ethmoidalis with the widest possible extirpation of the cells of the ethmoid labyrinth.

In case of mucocele of the sphenoid sinus or maxillary sinus, they are opened in the usual way, the mucous sac is removed with limited scraping of the mucous membrane in those places from which the mucocele originates, and a stable drainage opening of the sinus is formed.

In the postoperative period, the sinus is washed for 2-3 weeks with antiseptic solutions endonasal through the newly formed anastomosis. If purulent complications occur, depending on their location, prevalence and nature of the clinical course, extensive surgical intervention is performed in compliance with the principles of purulent surgery.