Address for correspondence : Jin Kook Kim, MD, PhD, Department of Otorhinolaryngology-Head & Neck Surgery, Konkuk University School of Medicine, 120-1 Neungdong-ro, Gwangjin-gu, Seoul 143-729, Korea
Tel : +82-2-2030-7662, Fax : +82-2-2030-5299, E-mail : entalk@kuh.ac.kr

Introduction

The nasal fontanelle (NF), the portion without bony structures in the medial aspect of the maxillary sinus, was divided into the anterior and posterior fontanelles by the uncinate.¹⁾ However, few anatomical studies have been conducted to depict and measure the NF because it could not be observed with-out removing the mucosal covering and because routine laboratory techniques for its removal often damaged the fine bony structures surrounding the NF. During middle meatal antrostomy, for instance, the uncinate process was first cut down, then the natural ostium was widened, and the nasal fontanelle was opened. In the variation such as laterally curved or flattened uncinate process, opening up of the maxillary sinus ostium became difficult, sometimes increased risk of orbital penetrations and therefore affected the outcome of the surgery and could easily lead to complications.²⁾
We hypothesized that in middle meatus, there was so limited space to medial side which composed of bony structure that the nasal polyp would lateralize the fontanelle composed of mucosal structure and chronic maxillary sinusitis may influence on the medialization of fontanelle due to pressure induced by accumulation of discharge.
This study aimed to evaluate the relationship between the location of the nasal fontanelle and either the chronic rhiosinusitis with nasal polyp in middle meatus (NP) or chronic maxillary sinusitis (CMS)(Fig. 1).

Subjects and Method

Patients
We classified 127 subjects who had not had any nasal septal deviation (deviation <5°) into three groups: normal control group, chronic maxillary sinusitis group without nasal polyp (CMS group), and chronic rhinosinusitis group with nasal polyp in middle meatus (NP group). By means of CT image, the angles of both nasal septum and fontanelle were measured; and both sides of a nasal cavity were counted individually. We had compared 96 CT scans of normal controls with 79 CT scans of CMS groups and 54 CT scans of NP groups. The cases of septal deviation ≥5°, fungal sinusitis, facial trauma and previous operation history were excluded.

CT image protocol
Rapidia 3D^® ver. 2.8 (INFINITT, Seoul, Korea) was employed for three dimensional (3D) reconstruction system. In case of discrepancy in the locations of both fontanelles on their CT scans, we reconstructed all the CT scans to identify the fontanelle location for further measurement of its angle. Lateral side on which the fontanelle actually was located was assigned to positive angle, while medial side was to negative angle to determine the presence of fontanelle deviation. In case of both sides of fontanelles was shown on different CT cuts, we rearranged the image by 3D reconstruction to be presented on the same view. If the borderline between a nasal polyp and fontanelle was not clear, endoscopic view of 3D reconstruction system was used to make it obvious (Fig. 2). Normal range of the fontanelle deviation was defined from the median of the range between the most medial and mean angle to the median of the range between mean and the most lateral angle (Fig. 3).

Position of fontanelle
The reference line was defined as line between midline of anterior dorsum and posterior nasal spine. The nasal fontanelle line was defined as line between anterior maxillary sinus medial bony margin and posterior medial bony margin. So the angle of nasal fontanelle composed of the reference line and the nasal fontanelle line (Fig. 4). There were no studies about clinical variation of nasal fontanelle, we defined that normal range of nasal fontanelle angle was between 25% quartiles and 75% quartiles. And over the normal range, we defined as lateralization, below that, as medialization (Fig. 3).

Statistical analysis
Statistical analysis was performed using SPSS 17.0 (SPSS, Inc., Chicago, IL, USA). The chi-square tests with Bonferroni Post Hoc test were performed to analyze the different rate of fontanelle position among three groups. A value of p≤0.05 was considered statistically significant.

Results

Clinical presentations
Gender ratio of a normal control group was 22 : 74 (M : F) and mean age was 41.4 (18-75) years. The ratio was 38 : 41 and the mean age was 48.5 (18-73) years for CMS group, while the ratio was 36 : 18 and the age was 45.3 (18-77) years for NP group respectively (Table 1).

Angle of fontanelle
The mean angle was 1.34° (-9.31-13.69°) in normal control group, 3.47° (-27.05-41.33°) in CMS, and 6.99° (-12.98-27.79°) in NP group respectively (Table 2).

Set-up normal range of fontanelle position
Normal range of angle between nasal fontanelle and nasal septum has not been reported yet, thus we have set it from the data obtained in normal control group. It has been set up from -2.43° to 5.90°, which was assumed by 50% of both medial and lateral side laying stress on the point of 2.06°, a mean angle of normal control group (-9.31° to 13.69°). We also classified the data into lateralization, normal and medialization group by means of the standard angle we had obtained (Table 3).

Position of fontanelle
In control group, lateralization, normal and medialization group showed 23, 48 and 25 sides respectively. Also 28, 35 and 16 sides respectively in CMS group and 30, 14 and 10 sides in NP group were obtained from the data. The lateralization of NP group was 55.6%, which indicated statistically significant gap with 24.0% in normal control group, and medialization of CMS group was 20.3% which did not have statistical significance comparing with normal control group, 26.0%. Other data did not have any statistical significance (Fig. 5).

Discussion

The first advantage of this study was the first trial that evaluated the location change of fontanelle in nasal polyp and CMS. We have figured out that nasal polyp would significantly lateralize the position of fontanelle by mass effect in comparison with normal group (p=0.001). We hypothesized that chronic maxillary sinusitis may influence on the medialization of fontanelle due to pressure induced by accumulation of discharge. Making a comparative study of CMS and normal control group, there were no difference of fontanelle position between CMS and normal control group (p=0.237), so was between CMS and NP group (p=0.051). In the result, it is considered that maxillary sinusitis does not have much influence on the medialization of fontanelle.
The second advantage of this study was the information of surgical anatomy. There were so many methods introduced about uncinectomy and middle meatal antrostomy.^2,3,4) It is explained for the purpose making less complication such as orbital complication,⁵⁾ it is indirect expression of variety of anatomic locations proceeding uncinectomy and middle meatal antrostomy.^6,7) The present study suggested that the change of fontanelle location is a certain cause making surgery difficulty such as anatomic variants. For example, when the nasal fontanelle was lateralized after removing middle meatal polyp, the uncinectomy was more trouble due to nearby lamina papyracea and the short range of backtbiter. Thus more attention is required when middle meatal antrostomy would be performed to the patients with NP, since there is quite a possibility that fontanelle may be located laterally.
There are some limitations to this study. First, to analyze the influence of nasal polyp on the position of fontanelle, it is appropriate to analyze patients with nasal polyp who do not have sinusitis. However, because there were few who fit them, we chose chronic rhinosinusitis group with nasal polyp to analyze the tendency of effect of nasal polyp on the position of fontanelle. Second, in NP group, rhinosinusitis included a maxillary sinus or other sinuses. Because it was reported that osteomeatal complex obstruction is not associated with adjacent sinus disease in chronic rhinosinusitis with polyps,⁸⁾ it is considered that other sinusitis except maxillary sinusitis may not have influence on the position of fontanelle. Further study is necessary to this subject.

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