What Is A Frontoethmoidal Sinus Mucocele?
According to medical and dental literature, frontoethmoidal mucocele can be mainly defined as a paranasal sinus lesion that appears cyst-like (also called mucocele) but is instead lined with respiratory mucosa. According to case reports, the frontal and frontoethmoidal regions are the most common locations for the occurrence of this paranasal sinus mucocele. They mainly develop due to primary obstruction in the normal sinus drainage, causing interference, and eventually grow into an expansile cyst-like fluid lesion in the paranasal sinuses, mainly in the frontal and the frontoethmoidal regions.
When the contents of this lesion form and expand, it causes thinning out the sinus walls, which is a characteristic feature, mainly presenting as a swelling above the medial canthus of the eye. This swelling on the medial side of the orbit can be painless and persist for several months to years, remaining unnoticed even by the patient. However, in the later phases of lesion development, patients suffering from this mucocele may complain of frequent headaches that mainly is attributed to sinusitis (sinus inflammation) of the frontal or ethmoidal air sinuses. Additionally, in the later stages, the continuous expansion of cystic contents can erode the bony walls of the sinus and may cause further erosion into the boundaries of the orbit, above the medial canthus of the eye, intracranially below the frontal lobe, or into the forehead (by erosion of the anterior frontal sinus wall but is comparatively uncommon due to the thickness of the anterior sinus wall).
What Are the Clinical Features of Frontoethmoidal Sinus Mucocele?
On eliciting patients' previous medical history, there might be traumatic or surgical history to the frontal sinus area that would predispose them to develop this mucocele as a secondary entity in some cases. Larger mucocele can cause a downward or inferior displacement of the eyeball. In the ethmoidal mucocele there is an additional displacement in the outward direction. Diplopia or double vision might be a common finding associated with large mucoceles. Similarly, a certain degree of clinical proptosis or bulging of eye sockets is also observed in these patients' correlative to eyeball displacement. Although mucoceles of the frontal and ethmoidal sinuses are a rare cause of unilateral proptosis, they have distinctive characteristics that make a diagnosis easy to make. Long-lasting proptosis that varies in size and gets worse with the common cold can be caused by mucoceles. As long as adequate images of the paranasal sinuses are captured, the distinctive radiological findings of a mucocele are very helpful in making a diagnosis. The eyelids remain largely unaffected and do not usually show inflammatory changes in a simple frontal or ethmoidal sinus mucocele. Neither the eyeball movements nor vision is affected in these mucoceles. If eyelids, eyeball movements, or vision impairment is observed in the patient, then the physician should establish a differential diagnosis. Diagnostically, upon intranasal endoscopic examination, a bulge may be observed in the middle meatus region due to the expansion in the ethmoidal air cells.
How to Diagnose Frontoethmoidal Sinus Mucocele?
The common diagnostic modalities adopted by the otolaryngologist or physician to check for a frontoethmoidal mucocele are:
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Caldwell Views X-ray: This X-ray view of the frontal sinus is extremely beneficial in diagnosis as a characteristic scalloping loss is observed on the sinus walls. The sinus walls exhibit a scalloped appearance in a normal sinus view, which is considered healthy.
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CT (Computed Tomography) Scan: CT scans are preferred over conventional X-rays or Caldwell view X-rays as this helps delineate the mucocele and assists in easy identification. CT scans also aid in obtaining a differential diagnosis and excluding other similar lesions like osteomas and ethmoidal malignancies by the physician. On the CT scan, the frontoethmoidal mucocele appears as a well-circumscribed expansile mass of the ethmoidal sinus. There is a homogenous hypoattenuation of the contents of the frontal sinus. The sinus contents may further appear hyperdense alongside any bony erosion or bony remodeling. These features are non-enhancing even with contrast CT.
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MRI(Magnetic Resonance Imaging): MRI is, in fact, the most widely preferred choice as it can distinguish a mucocele from a sinus tumor. Any symptoms like an intracranial or intraorbital extension can also be easily observed, which helps exclude diagnosis from other lesions.
- FNAC or Fine Needle Aspiration Cytology: By aspiration of the mucocele cells followed by histopathologic study, the investigation usually reveals a frontoethmoidal mucocele which typically presents with scanty inflammatory cell infiltration within the contents of the lesion that is of a mucoid or gelatinous consistency.
What Is the Differential Diagnosis of Frontoethmoidal Sinus Mucocele?
These three lesions being similar in manifestation, always need to be distinguished by the physician or healthcare provider from a frontoethmoidal mucocele:
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Lacrimal Sac Mucocele: This mucocele occurs usually below the level of the medial canthus of the eye and never above it. The frontoethmoidal mucocele always typically occurs above the medial canthus of the eye.
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Osteomas: These are hard and firm lesions that can be better observed or differentiated from paranasal sinus mucoceles either on CT scan or by Caldwell view X-ray imaging.
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Ethmoidal Malignancies: Cancers occurring within the paranasal sinuses can always be differentiated from mucocele lesions through an MRI. This is because the extent of the tumor is ideally analyzed and studied better through this technique. Also, a mucocele has fluid contents, while ethmoidal cancers appear clinically as solid masses with potential skin infiltration.
How to Manage Frontoethmoidal Sinus Mucocele?
1. Endoscopic Marsupialisation
The mainline surgical strategy for treating frontoethmoidal mucocele is through endoscopic marsupialization of the cyst. A wide segment of the medial wall from the mucocele can be excised by the surgeon endoscopically, and adequate drainage is established in order to maintain the osteal patency and prevent the recurrence of the cystic lesion. Attempts are never made to remove the cystic wall completely in this procedure to avoid postoperative complications.
2. Frontoethmoidectomy
Frontoethmoidectomy is another leading open surgical approach that may be performed by the surgeon instead of endoscopic marsupialization when the mucocele is larger in size. Postoperatively the surgeon prescribes antibiotics for 5 to 7 days, and the sutures can be removed after a week. Post-operative complications of surgical open approach techniques are webbing of scars or interference with cosmetics and an obstruction to the frontal sinus drainage that can facilitate the recurrence of infections.
Conclusion
To conclude, though frontoethmoidal is a chronic condition, it can be easily diagnosed with minimal clinical observations and non-invasive diagnostic procedures. These lesions are capable of slow expansive erosion into the face triggering severe inflammation and obstruction of the frontal or ethmoidal sinus. Hence, timely surgical management by cystic drainage would benefit the patient and improve post-surgical cosmetic outcomes.
