Acta Oto-Laryngologica. 2015; Early Online, 1–6

ORIGINAL ARTICLE

Characteristics of paranasal sinus osteoma and treatment outcomes

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DONG HOON LEE1, SE HEE JUNG2, TAE MI YOON1, JOON KYOO LEE1, YOUNG EUN JOO3 & SANG CHUL LIM1 1

Department of Otolaryngology-Head and Neck Surgery, 2Radiology and 3Research Institute of Medical Sciences, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Jeonnam, Korea

Abstract Conclusion: The incidence of paranasal sinus (PNS) osteoma was 6.4%. The most common site of PNS osteoma was the ethmoid sinus. All surgically treated patients underwent endoscopic surgery, and there was no recurrence in any patient. Technical improvements, including an image guidance system, extended the indications for endoscopic surgery for PNS osteomas, especially in the frontal sinus region. Objective: The purpose of this study was to investigate the incidence and location of PNS osteomas detected by computed tomography (CT) scan at our hospital, and to describe our experience in the surgical treatment of PNS osteomas. Methods: This study was performed on 1724 patients undergoing CT scans because of suspected sinus disease between 2004 and 2013. Endoscopic surgery was performed in 34 symptomatic patients. Medical records of the patients were reviewed, and clinical findings and treatment outcomes were investigated. Results: PNS osteomas were detected in 110 patients (6.4%). Triple osteomas were detected in two patients. Double osteomas were detected in seven patients. In total, 121 lesions were identified as PNS osteomas. The ethmoid sinus was the most commonly affected site (57.0%), followed by the frontal sinus (25.6%), frontal recess (9.1%), maxillary sinus (5.0%), olfactory fissure (1.7%), and sphenoid sinus (1.7%) in descending order of frequency. Thirty-three patients were surgically treated for PNS osteomas through a purely endoscopic approach, and one patient with a frontal sinus osteoma underwent combined endoscopic surgery and frontal trephination. Image-guided surgery was performed in nine patients with involvement of the orbit and skull base, including the frontal sinus/recess. There were no major surgical complications and there was no tumor recurrence.

Keywords: Computed tomography, endoscopic surgery, image guidance

Introduction Osteoma is the most common benign tumor of the paranasal sinus (PNS) [1]. PNS osteomas are mostly asymptomatic and may be incidentally detected by radiological examination [2,3]. Approximately 3% of all computed tomography (CT) scans of the PNS reveal osteomas [4]. PNS osteomas may be discovered at any age, but are usually found during the fourth through sixth decades, and there is a male preponderance [3–5]. The frontal sinus is most frequently involved, followed by the ethmoid, maxillary, and sphenoid sinuses in descending order of frequency [5,6]. The etiology of osteomas is still a matter

of discussion with various causes having been proposed, including embryologic, traumatic, and infective theories [2,7,8]. The imaging modality of choice is thin-slice CT [6,9]. CT allows precise estimation of the size and location of the osteoma, as well as concurrent sinus pathology [6]. In symptomatic patients, surgical removal of osteomas is the treatment of choice, whereas conservative treatment is usually recommended for asymptomatic or small osteomas [2,5,6]. The purpose of this study was to investigate the incidence and location of PNS osteomas detected by CT scans at our hospital, and to describe our experience in the surgical treatment of PNS osteomas.

Correspondence: Sang Chul Lim, MD, Department of Otolaryngology-Head and Neck Surgery, Chonnam National University Medical School and Hwasun Hospital, 160 Ilsimri, Hwasun, Jeonnam 519-809, South Korea. Tel: +82 61 379 8190. Fax: +82 61 379 7761. E-mail: [email protected]

(Received 16 October 2014; accepted 16 December 2014) ISSN 0001-6489 print/ISSN 1651-2251 online  2015 Informa Healthcare DOI: 10.3109/00016489.2014.1003093

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Material and methods After obtaining approval from the Institutional Review Board of Chonnam National University Hwasun Hospital, this study was performed on 1724 patients undergoing CT scans because of suspected sinus disease between 2004 and 2013. Radiologic examinations were performed using multi-detector CT scanners with a slice thickness of 0.6–2 mm. The 1724 examinations were reviewed jointly by one rhinologic surgeon (S.C.L.) and one radiologist (S.H.J.). Demographic characteristics, localization and size of osteomas, and clinical and imaging findings were reviewed. We classified PNS osteomas into five patterns according to the CT findings [4]: uniformly sclerotic, target-like lesion, partially corticated shell with heterogeneous matrix, heterogeneous matrix without a well-defined shell, and laminated pattern. In patients who underwent surgery, the type of surgical approach, treatment outcome, and intraoperative or postoperative complications were also analyzed. The type of surgical approach was determined by the size and location of the osteoma. Small osteomas were removed by en bloc resection. Large osteomas were removed by cavitation of the lesion with burrs, followed by fracturing and piecemeal removal of eggshell remnants (cavitation technique). Histopathological examination of the resected specimens was performed. Image-guided surgery (IGS) using a navigation system was performed in osteomas with involvement of the skull base and/or orbit. Results PNS osteomas were detected in 110 patients (6.4%). The ages of the patients ranged between 16 and 84 years, with a mean ± standard deviation (SD) of 56.3 ± 13.8 years. This group of patients included 62 males (56.4%) and 48 females (43.6%). More men than women were affected, with a male-to-female ratio of 1.29:1. Most of the osteomas detected were single lesions, found in 101 cases. Triple and double osteomas were detected in two cases (1.8%) and seven cases (6.4%), respectively. In total, 121 PNS osteomas were detected by CT scan. The ethmoid sinus was the most common location for osteomas (n = 69, 57.0%), followed by the frontal sinus (n = 31, 25.6%), frontal recess (n = 11, 9.1%), maxillary sinus (n = 6, 5.0%), olfactory fissure (n = 2, 1.7%), and sphenoid sinus (n = 2, 1.7%) in descending order of frequency. Among ethmoid sinus osteomas, 20 lesions involved the skull base and 14 lesions involved the lamina papyracea. Two lesions involved both the skull base and lamina papyracea.

Of the 121 lesions, 60 osteomas (49.6%) were located in the right paranasal sinus and 61 (50.44%) were located in the left paranasal sinus. The size of the osteomas varied from 1 to 39 mm at the widest point, with a mean diameter of 6.8 ± 4.9 mm. On CT classification of the osteomas [5], the majority were composed of uniformly sclerotic bone (n = 55, 45.5%), followed by heterogeneous matrix with partially corticated shell (n = 45, 37.2%). The remaining osteomas showed the target-like lesion (n = 16, 13.2%) and heterogeneous matrix without a well-defined shell (n = 5, 4.1%). The laminated pattern was not noted in the present study. Among 110 patients, we performed surgical treatment in 34 patients who had large or symptomatic osteomas, osteomas associated with complications, and osteomas accompanied by chronic sinusitis and headache without identified cause. There were 19 men and 15 women with a mean age of 51.3 ± 14.3 years (range 21–75 years). The site of the osteoma was the ethmoid sinus in 29 patients and the frontal sinus/recess in 5 patients. The mean tumor size was 7.9 ± 6.3 mm (range 3–31 mm). Most patients (n = 33, 97.1%) with osteomas had coexisting sinusitis. Presenting symptoms were usually nonspecific and included nasal obstruction or discharge due to concomitant sinusitis (n = 33), supraorbital pain and tenderness (n = 1), orbital discomfort (n = 1), and frontal headache (n = 1). Some of the patients reported more than one symptom. Small osteomas (n = 31, 91.2%) were removed by en bloc resection using curettes. Large osteomas (n = 3, 8.8%) were removed by cavitation technique using drills. Total removal of PNS osteomas could be done in all operated cases (n = 34). A purely endoscopic approach was performed in all patients except one patient with frontal osteoma (Chiu grade III) who underwent combined frontal trephination. IGS was performed in nine patients with involvement of the orbit or skull base. Five patients had ethmoid osteomas (Figure 1A), and four patients had frontal osteomas (Figure 1B). In all patients, histopathological findings of the resected specimens were consistent with osteoma. Exposure of the dura was noted in two patients with ethmoid osteoma with skull base involvement. The size of exposed dura was 6 and 12 mm in 12- and 31 mm-sized ethmoid osteomas, respectively. However, there were no cerebrospinal fluid (CSF) leaks resulting from surgical intervention. The periorbita was exposed in three patients and orbital fat herniation was noted in one patient. The periorbita or orbital fat was exposed in two patients with ethmoid osteoma, which was directly related to tumor removal, but periorbita exposure in two patients with frontal

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A

B

Figure 1. Image-guided surgery. (A) An orbital portion of ethmoid sinus osteoma (asterisk) which was partially drilled away. S, septum; M, maxillary sinus. (B) A partially resected frontal sinus osteoma (asterisk). F, anterior wall of the frontal sinus.

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sinus osteoma occurred during surgical manipulation to secure the operative view. The size of ethmoid osteomas was 17 mm and 31 mm and that of frontal osteomas was 17 mm and 25 mm. Exposed periorbita and orbital fat herniation healed uneventfully without reconstruction of the orbital wall. The dura or periorbita exposure usually developed in large osteomas with skull base and orbital involvement (>10 mm in the largest diameter), which suggests care should be taken to remove large osteomas endoscopically. Presenting symptoms usually improved after surgery, but in patients with concomitant chronic sinusitis, improvement was difficult to evaluate because of various postoperative symptoms. The mean follow-up period after surgery was 55.3 ± 26.2 months, with a range of 9–111 months. Patients were followed up with endoscopic examination and/or CT and recurrence was not observed in any patient. Discussion PNS osteomas were diagnosed radiologically in 6.4% of the patients in this study. This is a higher percentage than found in previous reports of osteomas detected in approximately 3% of CT scans [4,10]. The higher detection rate in the present study may be due to the use of a thin-slice CT protocol, in contrast to the 3 mm slice thickness used in previous reports [4,10]. We performed CT scans in 66 patients with slice thicknesses £1 mm (54.5%), and slice thickness values ranged from 0.6 to 2 mm. This study has the limitation that most of the PNS osteomas (71.9%, 87/ 121) were diagnosed radiologically, as in other incidence studies of PNS osteomas. Despite the possibility that other bone tumors might be included in our study, we think that its effect on incidence of PNS osteomas was minimal. Subsequent studies using CT examination with thinner sections and high resolution may show a higher incidence of PNS osteoma, similar to the results of our study. Most osteomas are asymptomatic, slow-growing lesions diagnosed incidentally in imaging studies [6]. Only 4–10% of all osteomas produce clinical symptoms [4,6]. Symptoms of PNS osteoma are usually related to the size, location, and growth rate of the tumor [5]. Facial pain and headache are the most common presenting symptoms [3,9]. The incidence of headache in various osteoma series varies between 52% and 100% [11]. However, headache in patients with PNS osteoma is nonspecific, and surgery should be carefully chosen in patients complaining of headache. According to most studies, the frontal sinus is the most commonly involved region for PNS osteoma, followed by the ethmoid, maxillary, and sphenoid sinuses in descending order of frequency [5,6].

However, some studies demonstrated that PNS osteomas were more common in the ethmoid sinus, followed by the frontal sinus [3,5]. In the present study, osteomas were more commonly located in the ethmoid sinus than in the frontal sinus. CT is an excellent tool for diagnosing osteomas [6,9]. CT imaging studies provide a precise estimation of the size and location of the osteoma, as well as concurrent sinus pathology [6]. Earwaker reported that osteomas are classified into five patterns according to CT findings [4]: uniformly sclerotic, target-like lesion, partially corticated shell with heterogeneous matrix, heterogeneous matrix without a well-defined shell, and laminated pattern. According to this classification scheme, uniformly sclerotic lesions were the most common finding [4,10]. The most common CT finding for PNS osteomas in this study was a uniformly sclerotic lesion (45.5%). Magnetic resonance imaging (MRI) might be helpful in differential diagnosis, in confirming an associated mucocele, and in case of intracranial or intraorbital involvement [6,11]. The management of PNS osteoma is usually decided by symptoms, location, and size [2,5,6]. Surgical removal is the generally accepted treatment of choice in symptomatic or rapidly growing osteomas, whereas conservative treatment is usually recommended for asymptomatic or small osteomas. In the conservative treatment group, we recommended serial CT scan every 1 or 2 years, because the average growth rate of osteomas is 1.61 mm/year, with a range of 0.44– 6.0 mm/year [12]. Although osteomas are usually slow growing, unpredictable sudden growth of PNS osteomas should be kept in mind. The surgical removal of frontoethmoidal osteomas is advised for tumors extending beyond the boundaries of the frontal sinus, those that continue to enlarge, those localized in the region adjacent to the frontonasal recess, those of the ethmoid sinus irrespective of size, and those associated with headache for which other causes have been excluded [13]. Some authors proposed removal of sphenoid osteomas as soon as possible because of the possibility of compression to the optic nerve [14]. In the present study, a patient with a sphenoid osteoma was followed up under a wait-and-see policy because of the small size of the lesion. In osteomas of the maxillary sinus, surgery can be indicated for large osteomas obstructing the maxillary fontanelle or risk of intraorbital complications [15]. In the present study, none of the patients with maxillary osteomas were treated surgically because the lesions were small and located in the lateral wall or floor of the maxillary sinus, sites that are difficult to approach endoscopically. Similar to previous reports [6,13], surgical indications for PNS osteoma in our hospital are as follows: large or symptomatic osteomas, osteomas associated

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Paranasal sinus osteoma with complications, growing osteomas detected by serial CT scans, osteomas accompanied by refractory chronic sinusitis, and osteomas with significant orbital extension. Irrespective of the size of the tumor, patients with ethmoid osteomas accompanied by chronic sinusitis were endoscopically treated, which increased the incidence of endoscopically removed ethmoid osteomas in this study compared with other reports. Although a wait-and-see policy is generally accepted in the management of small ethmoid sinus osteomas, some surgeons prefer to remove them because ethmoid sinus osteomas are likely to become symptomatic early, and small osteomas can be removed easily without surgical complications such as CSF leak or orbital injury [16]. Surgical options for PNS osteomas include endoscopic removal, external approach, or a combined approach using both methods. The size and location of the osteoma determines the type of approach [5]. Traditionally, endoscopic removal is suitable if the osteoma is located anywhere other than the frontal sinus [8]. In ethmoid osteomas, endoscopic approaches are relatively straightforward [7]. We also were able to remove all ethmoid osteomas with anterior skull base or lamina papyracea involvement by the endoscopic approach. Maxillary osteomas located in the upper part of the maxillary sinus can be treated endoscopically [6]. In addition, sphenoid sinus osteomas can be resected via the endoscopic approach. The external approach has been considered standard for removing frontal sinus osteomas [9]. However, accumulation of experience with endoscopic sinus surgery, technological advances (including the development of dedicated instruments), improved endoscopes, and IGS systems have expanded the limits of endoscopic approaches [8,17]. Chiu et al. recommended endoscopic resection of small frontal osteomas medial to the sagittal line passing through the lamina papyracea (grade I and II), while using the external approach if the location was lateral to the sagittal line passing through the lamina papyracea or filling the frontal sinus (grade III and IV) [18]. Additionally, small anteroposterior diameter of the frontal sinus (less than 1 cm), extensive superior location with more than 2 cm of osteoma in the frontal sinus, and far laterally located frontal osteoma (beyond the midline of the orbital roof) have been reported to be contraindications to exclusively endoscopic surgery. However, Turri-Zanoni et al. recently suggested that the size of the lesion, far lateral extension of the tumor in the frontal sinus beyond the lamina papyracea, and intraorbital involvement no longer represent absolute contraindications for purely endoscopic resection [17]. Sies´kiewicz et al. also reported successful removal of frontal osteomas in

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six cases designated Chiu grade III [19]. However, despite successful outcomes for adversely located frontal osteomas reported in a few case series treated with a purely endoscopic approach, favorable anatomic conditions are mandatory for the removal of frontal osteomas. The endoscopic technique enables shorter hospitalization time, preserves the natural endonasal drainage pathways, and reduces postoperative morbidity [6,17]. On the other hand, the endoscopic approach requires lengthier surgical training and greater experience [17]. IGS with a navigation system, clearly helpful in endoscopic osteoma surgery, offers satisfactory accuracy, predicts the complete removal of the osteoma, and preserves the surrounding vital structures such as the orbit or brain [8,14]. In addition, it should be noted that when an osteoma is not removed via an endoscopic approach, an external approach such as frontal trephination can be used as an adjuvant to endoscopic surgery, especially in the case of frontal sinus osteoma. In the present study, a purely endoscopic approach was performed in 33 patients with frontoethmoidal osteomas, while 1 patient with a Chiu grade III frontal sinus osteoma needed endoscopic surgery combined with frontal trephination for the complete removal of the osteoma. There were no major surgical complications such as CSF leak and orbital injury, especially notable in cases with involvement of the skull base and lamina papyracea. In fact, osteomas arising from the intranasal bony structure grow laterally toward the orbit and brain, compressing but preserving the periorbital layer and dura [20]. We could remove large osteomas with extensions to the adjacent skull base or orbit without significant dural or orbital injury via IGS and the endoscopic cavitation technique wherein the center of the tumor is drilled away and the thin peripheral bony shell of the osteoma is removed. Tumor recurrence was not observed in any patient. Conclusion The incidence of PNS osteoma was 6.4% in this study. PNS osteomas were most common in the ethmoid sinus, followed by the frontal sinus. PNS osteomas were successfully removed by the endoscopic approach and no recurrences were observed in any patients. Improved endoscopic surgical skills and technical developments, including IGS, have extended the indications for endoscopic surgery for PNS osteomas and enabled endoscopic resection of osteomas with difficult-to-reach locations such as the frontal sinus. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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Characteristics of paranasal sinus osteoma and treatment outcomes.

The incidence of paranasal sinus (PNS) osteoma was 6.4%. The most common site of PNS osteoma was the ethmoid sinus. All surgically treated patients un...
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