Introduction
Osteomas are noncancerous bone tumors that grow slowly and are commonly found in the skull or lower jaw bones [6]. Various theories, including developmental, traumatic, and infectious factors, have been proposed to explain the origin of osteomas [2], but the exact cause remains unclear [4]. Osteomas typically do not cause symptoms. In this regard, conservative treatment is usually recommended [7]. However, when osteomas in the paranasal sinuses extend into the skull or eye socket and cause symptoms, surgical intervention is the preferred treatment [2, 7]. Surgery can be performed using either an endoscopic approach through the nasal cavity, with a microscopic approach through the skull, or a combination of both methods [4, 8]. In this study, we present a rare and aggressive case of frontoethmoidal sinus osteoma with intracranial extension and uncommon associated symptoms.

Case Presentation
A 27-year-old man visited our hospital complaining of headaches and frequent episodes of sleep apnea. He also reported chronic worsening of forehead headaches, reduced sense of smell, and a history of chronic sinusitis with left nasal congestion. Rhinoscopic examination revealed congested mucus and multiple polyps in the nasal cavity, but no abnormal discharge was observed. Computed tomography scans of the paranasal sinuses and skull showed a large fibro-osseous mass in the frontal sinus, extending into the skull. Magnetic resonance imaging of the brain confirmed the presence of a sizable lesion within the frontal skull, approximately 8 cm in diameter. 
The mass exhibited a heterogeneous signal and exerted pressure on the surrounding brain tissue. Due to the size of the mass and the patient’s symptoms, surgical removal of the tumor was deemed necessary. A combined surgical approach utilizing both microscopic and endoscopic methods through the skull and nasal cavity, respectively, was chosen to ensure complete tumor removal. During the surgery, a large pericranial flap was created to access the tumor through the skull. A bilateral frontal craniotomy was performed, revealing a large lesion involving the frontal sinus and extending into the dura mater. Under microscopic guidance and using microsurgery tools, the mass was completely excised. 
Following tumor removal, reconstruction of the left anterior cranial cavity, posterior wall of the frontal sinus, and base of the skull was performed. The operation was completed with bilateral endoscopy of the skull base through the nasal cavity, which involved anterior and posterior ethmoidotomy and internal enterostomy. 
After confirming the successful removal of the tumor, reconstruction of the skull base was finalized. The patient was subsequently transferred to the neurosurgery department in good overall condition. The excised bone mass was sent to the pathology department for examination, which confirmed the diagnosis of osteoma. The patient remained hospitalized and monitored in the neurosurgery department for three days following the surgery. Fortunately, his symptoms significantly improved, and he was discharged in good general condition without any neurological deficits. During the 6-week follow-up visit, the patient reported complete resolution of headaches and sleep apnea attacks, expressing satisfaction with the outcome of the procedure.

Conclusion
Paranasal sinus osteomas are slow-growing benign tumors [5]. Although most osteomas are small and asymptomatic, they can lead to various complications depending on their size and location [5]. These tumors can cause symptoms by exerting pressure or obstructing nearby structures [11]. Common clinical manifestations include frontal sinusitis, headaches, and the presence of nasal polyps and mucoceles alongside the osteoma [12]. When frontal sinus osteomas grow posteriorly, intracranial involvement and extension into the dura mater can occur, potentially resulting in complications such as cerebrospinal fluid fistula, meningitis, pneumocephalus, or brain abscess [12].
In our case, the patient presented with headaches and frequent sleep apnea attacks. While headaches are not uncommon in large osteomas, frequent sleep apnea attacks are rare. Sleep apnea is a serious sleep disorder characterized by repeated interruptions in breathing. Typical symptoms of sleep apnea include loud snoring, gasping during sleep, waking up with a dry mouth, and morning headaches [9]. Sleep apnea can affect individuals of any age, but certain factors increase the risk, such as being overweight, having a short neck, being male, smoking, and experiencing nasal congestion [9].
Osteomas are typically round or oval, firm, yellowish-white tumors with well-defined borders [8]. However, in our case, a very large tumor with unclear boundaries and extensive extension into the skull, eye socket, and nasal cavity was observed, suggesting a delayed diagnosis in this patient. Although several theories, including trauma, infection, genetics, and developmental factors, have been proposed to explain their formation, the exact cause of osteoma development remains unclear [2]. According to the infectious theory, chronic inflammation triggers bone irritation, leading to the formation of osteomas [2]. In our case, the patient had a history of chronic sinusitis and left nasal congestion, which may have contributed to the development of the osteoma.
Surgical intervention is the primary treatment for symptomatic osteomas [7, 8]. The choice of surgical technique depends on the size and location of the tumor. In our case, a combined approach utilizing both microscopic and an endoscopic methods was selected to ensure complete tumor removal. The use of an endoscope through the nasal cavity allows for better visualization and access to the tumor, while the microscope provides magnification and precision during the procedure [4]. Reconstruction of the skull base is crucial to prevent complications such as cerebrospinal fluid leakage or infection [5]. In our case, reconstruction of the skull base was performed after tumor removal to restore the integrity of the frontal sinus and prevent potential complications.
In this study, we presented a rare and aggressive case of frontoethmoidal sinus osteoma with intracranial extension. This highlights the importance of considering osteomas in the differential diagnosis of patients presenting with chronic headaches and sleep apnea. Prompt diagnosis and surgical intervention are crucial for the management of symptomatic osteomas. A combined surgical approach utilizing both microscopic and endoscopic methods can ensure complete tumor removal. Long-term follow-up is necessary to monitor for any recurrence or complications.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Kermanshah University of Medical Sciences (Code: IR.KUMS.REC.1402.188)

Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors 

Authors' contributions
Methodology: Ehsan Alimohammadi and Seyed Reza Bagheri Bavandpouri; Data collection: Kousar Mohammadi; Initial draft preparation: Ehsan Alimohammadi and Kousar Mohammadi; Supervision: Ehsan Alimohammadi; Conceptualization, investigation, editing & review: All authors.

Conflicts of interest
The authors declared no conflict of interest.


References