- Email: [email protected]
Computed tomographic and endoscopic analysis of supraorbital ethmoid cells
Otolaryngology–Head and Neck Surgery (2007) 137, 562-568
ORIGINAL RESEARCH—SINONASAL DISORDERS
Computed tomographic and endoscopic analysis of supraorbital ethmoid cells Luo Zhang, MD, Demin Han, MD, PhD, Wentong Ge, MD, Jianhua Tao, MD, Xianzhong Wang, MD, Yunchuan Li, MD, and Bing Zhou, MD, Beijing, P. R. China OBJECTIVES: The aim of this study is to look at the incidence of supraorbital ethmoid cells (SOEC) in normal Chinese subjects by using spiral computed tomography (CT) scanning. In addition, subjects with chronic rhinosinusitis with SOEC were reviewed for endoscopic analysis. METHODS: A total of 202 normal Chinese subjects underwent spiral CT. Meanwhile, a retrospective review of patients who had undergone endoscopic sinus surgery over a 1-year period was conducted. RESULTS: SOEC showed an incidence of 5.4% (22 sides), and all of them arose from the anterior ethmoid cells. On coronal CT, an SOEC might give the appearance of multiple frontal sinuses, type III frontal cells, suprabullar cells, frontal bullar cells, interfrontal septal cells, or that there was a septation present within the frontal sinus. Meanwhile, 11 chronic rhinosinusitis patients with 12 SOEC were identified. CONCLUSION: A thorough knowledge of endoscopic anatomy and CT of the frontal recess and various fronto-ethmoid cells were required for safe dissection of the SOEC and frontal ostium. © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.
T
he advent of less invasive techniques of endoscopic frontal sinus surgery provides an important role for computed tomography (CT) of the paranasal sinuses, especially in the frontal recess and frontal sinus regions. In terms of imaging the fine detailed anatomy and its variants, 3-dimensional high resolution CT acts as a diagnostic tool as well as a major part of preoperative planning.1,2 Historically, the importance of anatomic variations in the frontal recess and frontal sinus regions was stressed by Turner, Cryer and Shambaugh more than 100 years ago.3 Although these anatomic variations do not represent disease states by themselves, together with mucosa inflammatory processes, they compromise the already narrow frontal sinus drainage pathway and produce significant obstruction that may play a role in both frontal sinusitis4 and revision surgery.3,5,6 The frontal pneumatization patterns are determined by the variable fronto-ethmoid cells, which include supraor-
bital ethmoid cells (SOEC), frontal cells (FC), suprabullar cells (SBC), frontal bullar cells (FBC), interfrontal septal cells (IFSC), etc.1,7 The incidence of these variations has been described previously from dissection of cadaver specimens8 and more recently by CT scanning.4,7,9-12 Defined by Van Alyea in 1942, an SOEC is an (anterior mostly) ethmoid cell that invades the supraorbital plate of the frontal bone. A knowledge of the anatomy of the SOEC is important for endoscopic frontal sinus surgery. Failure to recognize SOEC as well as other fronto-ethmoid cells can mislead the surgeon into believing the targeted frontal sinus has been opened. On the other hand, obstruction of the SOEC may result in a supraorbital cell mucocele,5 and unopened SOEC are commonly seen in more than 10% of patients with revision endoscopic sinus surgery.13 It has been reported that ethnic factors may have an influence on anatomic variants. With the use of CT scanning, Badia et al14 reported a significantly higher incidence of sphenoethmoid cells in 100 Chinese subjects compared with that of 100 white subjects, which hints that there are ethnic differences in certain anatomic variants. In 2006, a significantly lower incidence of SOEC was reported in a Korean population (2.6%) compared with white subjects (64.6%).9 Because China is part of East Asia, as is Korea, we presumed a low incidence of SOEC in the normal Chinese population. The aim of this study was to look at the incidence of SOEC in normal Chinese subjects, assessed by spiral CT scanning. Moreover, we present the results of endoscopic dissection of 11 cases of chronic rhinosinusitis in 11 patients with 12 SOECs.
METHODS The protocol was approved by Institutional Committee of Beijing Institute of Otolaryngology.
Received April 23, 2007; revised May 29, 2007; accepted June 26, 2007.
0194-5998/$32.00 © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved. doi:10.1016/j.otohns.2007.06.737
Zhang el al
CT and endoscopic analysis of SOEC . . .
CT Analysis of SOEC The CT analysis was performed at the Department of Otolaryngology–Head and Neck Surgery and the Department of Radiology, Beijing TongRen Hospital (affiliated with the Capital Medical University). From November 2004 to December 2006, 202 subjects (404 sides of the frontal region) with no previous clinical history of frontal sinus disease were identified. These subjects were either patients with no frontal sinus disease or volunteers. The mean ⫾ SD age of subjects was 39.4 ⫾ 13.5 years (range, 17 to 81 years). Gender distribution was 121 men and 81 women. Spiral CT scans of the nasal cavities and paranasal sinuses were performed with a GE LightSpeed CT scanner (GE Medical Systems, Milwaukee, WI) with overlapping axial cuts of 0.625 mm thickness. The scanning parameters used were 120 kV and 400 mA, and intermediate window and level settings were 2500 HU and 300 HU, respectively. The images were then forwarded to an imaging laboratory and evaluated with a standard triplanar reconstruction protocol on a computer workstation (Volume Viewer, GE Medical Systems). We evaluated images for the presence of SOEC as well as other fronto-ethmoid cells with the criteria defined by Lee et al,7 which was a combination of traditional concepts and contemporary knowledge. Each CT scan was studied jointly by one of the consultant ENT surgeons (Zhang L and Han D) and one radiologist (Tao J). Because the radiologist read all the CTs, this allowed for minimized variability of interpretation between the 2 teams.
Endoscopic Analysis of SOEC We conducted a retrospective review of patients who had undergone endoscopic sinus surgery over a 1-year period (Department of Otolaryngology–Head and Neck Surgery at Beijing TongRen Hospital). CT scans of the nasal cavities and paranasal sinuses were performed on either a GE SYTEC4000i CT scanner (GE Medical Systems) with coronal and axial cuts of 2 mm thickness or the GE LightSpeed CT scanner, and intermediate window and level settings were 2000 HU and 200 HU, respectively. SOEC were generally determined by their radiographic location on coronal and axial images. The surgical plan for the patients would be uncinectomy followed by opening of the agger nasi cell by removal of its anterior and medial walls. After removal of the anterior wall of the ethmoid bulla, its above-sitting SOEC was identified. Anteriorly, structures that obstructed the frontal ostium, such as the terminal recess and/or FC, were removed. The openings of the SOEC and frontal sinus were identified, mostly with the use of a 70-degree endoscopy. Postoperatively, each patient was assessed by 30- or 70-degree nasal endoscopy for SOEC and frontal sinus patency.
RESULTS CT Analysis of SOEC Of the 404 sides from 202 subjects, the presence of SOEC was found in 22 (5.4%) sides. All 22 SOECs arose from the
563 anterior ethmoid cells. On coronal CT images an SOEC (Fig 1A) might initially give the appearance of multiple frontal sinuses (Fig 2A), type III FC (Fig 2B), FBC (Fig 2B), IFSC, or that there was a septation present within the frontal sinus. In Figure 1, what might appear to be the most lateral compartment of a septated frontal sinus was actually a separate ethmoid cell present posterior and lateral to the frontal sinus. With the images moving posteriorly, the lateral cell located immediately above the orbital bone appeared to become wider. Meanwhile, the medial 2 cells joined to become one cell (Fig 1A and B). The axial images illustrated that the location of the lateral cell was behind and lateral to the medial 2 cells, and the most medial cell was the pneumatization of the frontal septal (note the location of the crista galli), named IFSC (Fig 1B). The sagittal image confirmed the location of the SOEC. Furthermore, it illustrated that the origin of the cell was the anterior ethmoid sinus (Fig 1C). The appearance of more than one cell in the frontal region on the coronal image should require considering the presence of fronto-ethmoid cells. For example, the IFSC was the pneumatization of the frontal septal, usually illustrated on coronal and axial CT images. FBC might have a similar appearance on sagittal and axial CT images to SOEC (Fig 2C and D). However, differences were identified on coronal CT images (Fig 2B). In Figure 2, the initial coronal CT image illustrated two separated cells in the left frontal sinus (Fig 2A). The coronal image cut further behind illustrated a type III FC on the left side, which was confirmed by the left sagittal image. The type III FC was a single large ethmoid cell above the agger nasi cell (Fig 2B), and its superior wall inserted on the inner aspect of the anterior frontal sinus table. The FBC was an ethmoid cell above the ethmoid bulla (Fig 2D). It was located medially in the frontal region on the coronal image (Fig 2B). Although its posterosuperior wall was the anterior skull base, its anterior border extended into the frontal sinus (Fig 2D). The FBC might have anteroinferiorly compressed the simultaneouslypresented type III FC (Fig 2B and D).
Endoscopic Analysis of SOEC Eleven chronic rhinosinusitis patients (10 males and 1 female) with 12 SOECs, ranging in age from 25 to 58 (mean, 39.9) years, were identified. Of these, only one had previously undergone endoscopic sinus surgery. The most frequently reported symptoms were nasal obstruction (82%), mucous rhinorrhea (73%), headache (64%), and hyposmia (55%). CT scan findings demonstrated one patient had two SOECs. The remaining 10 patients had one SOEC each. All 12 SOECs originated from the anterior ethmoid cell (Fig 3) and the cell extended superolaterally between the lamina papyracea and the roof of the ethmoid to pneumatize the orbital plate of the frontal bone. Intraoperatively, the SOEC was first identified after removal of the anterior wall of the ethmoid bulla, and its recess location gave the impression of a frontal ostium location. This configuration altered the frontal drainage
564
Otolaryngology–Head and Neck Surgery, Vol 137, No 4, October 2007
Figure 1 (A) Coronal plane CT images illustrates two cells in the left frontal region. The most lateral one is the SOEC (**) and the medial one is the frontal sinus merged with the IFSC (*). (B) Axial plane CT images illustrates three cells in the left frontal region. The most lateral one is the SOEC (**), the most medial one is the IFSC (*), and in the middle is the frontal sinus. The crista galli is indicated (arrow). (C) Left saggital plane CT image demonstrates the SOEC originated from the ethmoid sinus. (ANC, agger nasi cell; EB, ethmoid bullar)
pathway as the SOEC pushed the pathway anteriorly. The frontal ostium was anterior and medial to the SOEC recess, which was mostly blocked by the insertion of the uncinate process onto the lamina papyracea, the terminal
recess. The surgeon could fully expose the frontal recess by passing the curette behind the posterior wall of the agger nasi cell and fracturing the posterior wall and roof of the agger nasi cell. Because the frontal ostium was
Zhang el al
CT and endoscopic analysis of SOEC . . .
565
Figure 2 (A) Coronal CT image illustrates two separated cells in the left frontal sinus (*). (B) Coronal image cut further behind illustrates a type III FC (**) above the agger nasi cell (A) on the left side. On the right side, beside a type III FC (**) above agger nasi cell (A), a FBC is indicated by the arrow. (C) Right sagittal image illustrates the agger nasi cell (A), type III FC (**), and the FBC (arrow). (D) Axial image illustrates a type III FC (**) on both sides, together with a FBC (arrow) on the left.
anterior and medial to the SOEC recess, which pushed the anterior skull base posteriorly, and the SOEC recess was anterior to the anterior ethmoid artery, the risk of damage to the anterior ethmoid artery was theoretically
less (Fig 3C). All the patients remain free of disease after endoscopic sinus surgery (range, 2 to 17 months; median, 10 months). This was documented by nasal endoscopy with or without CT scanning.
566
Otolaryngology–Head and Neck Surgery, Vol 137, No 4, October 2007
Figure 3 Chronic sinusitis patient with SOEC. (A) Coronal CT image illustrates two cells in the right frontal region. The lateral one is the SOEC (**) and the medial one is the frontal sinus (*). (B) Axial image illustrates the frontal sinus (*) and SOEC (**) on the right side. (C), Endoscopic view (70 degree) of the frontal sinus ostium (*) and the SOEC recess (**) on the side, which were separated by a thick bone separation.
DISCUSSION With the development of endoscopic frontal sinus surgery, the importance of both the anatomy1,3,15-18 and the CT4,7,9,10,12,19,20 of the frontal recess have been emphasized. High-resolution CT has extensively shown the intrinsic complexity of the anatomy of the frontal recess.7 SOEC3 and other fronto-ethmoid cells compromise the narrow frontal sinus drainage pathways and produce significant obstruction. The existence of SOEC in cadaver specimens was investigated about 50 years ago by Kasper, Van Alyea, and Dixon, and the presence rate ranged from 5% to 15%.3,8 By using spiral CT, the incidence of SOEC in 2 normal white
populations (⬃50 cases) were shown to be more than 60% (62%7 and 64.6%9). Moreover, Cho et al11 compared the incidence of SOEC in 57 Korean subjects with that in 41 white subjects. SOEC were overwhelmingly more frequent in the white (64.6%) population, compared with the Korean (2.6%) population, which might be attributable to the more pronounced glabella and superior orbital rim found in whites. Thus, we presumed that China, which is also located in East Asia, also has a lower incidence of SOEC. In our normal population of 202 subjects, the SOEC frequency (5.4%) was generally consistent with that of Korean subjects, which also hints an ethnic influence on the development of SOEC.
Zhang el al
CT and endoscopic analysis of SOEC . . .
It has been realized that the differential identification of SOEC, as well as other fronto-ethmoid cells, by using 3-dimensional CT is crucial. There was a possibility of presenting fronto-ethmoid cells when multiple cells appeared in the frontal region on coronal CT.3 These multiple cells should be considered as SOEC, multiple frontal sinuses, type III FC, FBC, or IFSC. Meanwhile, a tiny septation presented within the frontal sinus might also give the appearance of multiple cells. Generally speaking, while the type III FC, FBC, or IFSC was medial to the frontal sinus, the SOEC was lateral to the frontal sinus. Although IFSC were located in the frontal sinus, type III FC or FBC were posterior to IFSC. Both type III FC and FBC were above the agger nasi cell. However, coronal CT scanning alone was not enough to discriminate FBC from type III FC, although FBC were posterior to type III FC. Both sagittal CT and axial CT were extremely helpful for this discrimination. On the sagittal CT images, FBC and SOEC had a similar appearance. The difference in the two types of cells was the degree of frontal pneumatization. On coronal CT images, the SOEC was lateral to the frontal sinus, while the FBC was medial to the frontal sinus. Although the high prevalence of SOEC was reported with the use of CT analysis, endoscopic management of SOEC was rarely mentioned in the literature. In 1997, Owen and Kuhn3 reported three cases of revision endoscopic surgery with endoscopic exposure of SOEC. Later, 10 cases of supraorbital cell mucocele, which were managed endoscopically, were reported by Chiu and Vaughan.5 With a much lower prevalence of SOEC in China (5.4%), we reported 11 cases of chronic rhinosinusitis with 12 SOEC. In this series of 11 patients, all SOECs arose from the anterior ethmoid cells. To effectively eliminate disease in the frontal area, the surgeon must positively identify an opening into each of the cells during endoscopic surgery. When operating in the frontal recess, the surgeon must carefully locate two anatomic landmarks, the terminal recess and the ethmoid bulla. Nearly 90% of the superior uncinate process inserts onto the lamina papyracea to form the terminal recess. The frontal drainage pathway was between the posterior wall of the terminal recess and the anterior wall of the SOEC. The identification of the ethmoid bulla led the surgeon to its above-sitting SOEC. Because the SOEC recess was high in the anterior ethmoid roof, it could often be confused with the frontal ostium, and the removal of the terminal recess led to the full exposure of the frontal ostium. The existence of SOEC pushed the frontal drainage pathway anteriorly and narrowed the frontal recess. In conclusion, a thorough knowledge of anatomy and CT of the frontal recess and various fronto-ethmoid cells are required for safe dissection of SOEC and the frontal ostium. The SOEC recess is located posteriorly and laterally to the frontal ostium, and the anterior ethmoid artery is located posteriorly to the SOEC. Although enlarging the SOEC in the posterior direction could risk
567 injury to the anterior ethmoid artery, enlarging the frontal ostium in the posterior direction had a lower potential to cause injury to the artery.
AUTHOR INFORMATION From the Beijing Institute of Otolaryngology (Drs Zhang and Han) and the Departments of Otolaryngology–Head and Neck Surgery (Drs Zhang, Han, Ge, Wang, Li, and Zhou) and Radiology (Dr Tao), Beijing TongRen Hospital, Capital Medical University, Beijing, P. R. China. Corresponding author: Demin Han, 1, DongJiaoMinXiang Avenue, DongCheng District, Beijing, 100730 P. R. China. E-mail address: [email protected].
AUTHOR CONTRIBUTIONS Demin Han, study design; Luo Zhang, study design; Surgeon; CT analysis; Wentong Ge, surgeon; CT analysis; Jianhua Tao, CT analysis; Xianzhong Wang and Yunchuan Li, surgeons, Bing Zhou, editing.
AUTHOR DISCLOSURE None.
REFERENCES 1. Wormald PJ. Three-dimensional building block approach to understanding the anatomy of the frontal recess and frontal sinus. Operative Techniques in Otolaryngology 2006;17:2–5. 2. Wormald PJ. The agger nasi cell: the key to understanding the anatomy of the frontal recess. Otolaryngol Head Neck Surg 2003;129(5): 497–507. 3. Owen RG Jr, Kuhn FA. Supraorbital ethmoid cell. Otolaryngol Head Neck Surg 1997;116(2):254 – 61. 4. DelGaudio JM, Hudgins PA, Venkatraman G, et al. Multiplanar computed tomographic analysis of frontal recess cells: effect on frontal isthmus size and frontal sinusitis. Arch Otolaryngol Head Neck Surg 2005;131(3):230 –5. 5. Chiu AG, Vaughan WC. Management of the lateral frontal sinus lesion and the supraorbital cell mucocele. Am J Rhinol 2004;18(2):83– 6. 6. Bradley DT, Kountakis SE. The role of agger nasi air cells in patients requiring revision endoscopic frontal sinus surgery. Otolaryngol Head Neck Surg 2004;131(4):525–7. 7. Lee WT, Kuhn FA, Citardi MJ. 3D computed tomographic analysis of frontal recess anatomy in patients without frontal sinusitis. Otolaryngol Head Neck Surg 2004;131(3):164 –73. 8. Dixon FW. The clinical significance of the anatomical arrangement of the paranasal sinuses. Ann Otol Rhinol Laryngol 1958;67(3): 736 – 41. 9. Cho JH, Citardi MJ, Lee WT, et al. Comparison of frontal pneumatization patterns between Koreans and Caucasians. Otolaryngol Head Neck Surg 2006;135(5):780 – 6. 10. Landsberg R, Friedman M. A computer-assisted anatomical study of the nasofrontal region. Laryngoscope 2001;111(12):2125–30. 11. Meyer TK, Kocak M, Smith MM, et al. Coronal computed tomography analysis of frontal cells. Am J Rhinol 2003;17(3):163– 8. 12. Turgut S, Ercan I, Sayin I, et al. The relationship between frontal sinusitis and localization of the frontal sinus outflow tract: a computer-
568
13. 14. 15.
16.
Otolaryngology–Head and Neck Surgery, Vol 137, No 4, October 2007
assisted anatomical and clinical study. Arch Otolaryngol Head Neck Surg 2005;131(6):518 –22. Chiu AG, Vaughan WC. Revision endoscopic frontal sinus surgery with surgical navigation. Otolaryngol Head Neck Surg 2004;130(3):312– 8. Badia L, Lund VJ, Wei W, et al. Ethnic variation in sinonasal anatomy on CT-scanning. Rhinology 2005;43(3):210 – 4. Daniels DL, Mafee MF, Smith MM, et al. The frontal sinus drainage pathway and related structures. AJNR Am J Neuroradiol 2003;24(8): 1618 –27. Friedman M, Bliznikas D, Vidyasagar R, et al. Frontal sinus surgery 2004: update of clinical anatomy and surgical techniques. Operative Techniques Otolaryngol Head Neck Surg 2004;15(1):23-31.
17. Kuhn FA, Bolger WE, Tisdal RG. The agger nasi cell in frontal recess obstruction: an anatomic, radiologic and clinical correlation. Operative Techniques Otolaryngol Head Neck Surg 1991;2: 226 –32. 18. Zhang L, Han D, Ge W, et al. Anatomical and computed tomographic analysis of the interaction between the uncinate process and the agger nasi cell. Acta Otolaryngol 2006;126(8):845–52. 19. Coates MH, Whyte AM, Earwaker JW. Frontal recess air cells: spectrum of CT appearances. Australas Radiol 2003;47(1):4 –10. 20. Kew J, Rees GL, Close D, et al. Multiplanar reconstructed computed tomography images improves depiction and understanding of the anatomy of the frontal sinus and recess. Am J Rhinol 2002;16(2):119 –23.
ORIGINAL RESEARCH—SINONASAL DISORDERS
Computed tomographic and endoscopic analysis of supraorbital ethmoid cells Luo Zhang, MD, Demin Han, MD, PhD, Wentong Ge, MD, Jianhua Tao, MD, Xianzhong Wang, MD, Yunchuan Li, MD, and Bing Zhou, MD, Beijing, P. R. China OBJECTIVES: The aim of this study is to look at the incidence of supraorbital ethmoid cells (SOEC) in normal Chinese subjects by using spiral computed tomography (CT) scanning. In addition, subjects with chronic rhinosinusitis with SOEC were reviewed for endoscopic analysis. METHODS: A total of 202 normal Chinese subjects underwent spiral CT. Meanwhile, a retrospective review of patients who had undergone endoscopic sinus surgery over a 1-year period was conducted. RESULTS: SOEC showed an incidence of 5.4% (22 sides), and all of them arose from the anterior ethmoid cells. On coronal CT, an SOEC might give the appearance of multiple frontal sinuses, type III frontal cells, suprabullar cells, frontal bullar cells, interfrontal septal cells, or that there was a septation present within the frontal sinus. Meanwhile, 11 chronic rhinosinusitis patients with 12 SOEC were identified. CONCLUSION: A thorough knowledge of endoscopic anatomy and CT of the frontal recess and various fronto-ethmoid cells were required for safe dissection of the SOEC and frontal ostium. © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.
T
he advent of less invasive techniques of endoscopic frontal sinus surgery provides an important role for computed tomography (CT) of the paranasal sinuses, especially in the frontal recess and frontal sinus regions. In terms of imaging the fine detailed anatomy and its variants, 3-dimensional high resolution CT acts as a diagnostic tool as well as a major part of preoperative planning.1,2 Historically, the importance of anatomic variations in the frontal recess and frontal sinus regions was stressed by Turner, Cryer and Shambaugh more than 100 years ago.3 Although these anatomic variations do not represent disease states by themselves, together with mucosa inflammatory processes, they compromise the already narrow frontal sinus drainage pathway and produce significant obstruction that may play a role in both frontal sinusitis4 and revision surgery.3,5,6 The frontal pneumatization patterns are determined by the variable fronto-ethmoid cells, which include supraor-
bital ethmoid cells (SOEC), frontal cells (FC), suprabullar cells (SBC), frontal bullar cells (FBC), interfrontal septal cells (IFSC), etc.1,7 The incidence of these variations has been described previously from dissection of cadaver specimens8 and more recently by CT scanning.4,7,9-12 Defined by Van Alyea in 1942, an SOEC is an (anterior mostly) ethmoid cell that invades the supraorbital plate of the frontal bone. A knowledge of the anatomy of the SOEC is important for endoscopic frontal sinus surgery. Failure to recognize SOEC as well as other fronto-ethmoid cells can mislead the surgeon into believing the targeted frontal sinus has been opened. On the other hand, obstruction of the SOEC may result in a supraorbital cell mucocele,5 and unopened SOEC are commonly seen in more than 10% of patients with revision endoscopic sinus surgery.13 It has been reported that ethnic factors may have an influence on anatomic variants. With the use of CT scanning, Badia et al14 reported a significantly higher incidence of sphenoethmoid cells in 100 Chinese subjects compared with that of 100 white subjects, which hints that there are ethnic differences in certain anatomic variants. In 2006, a significantly lower incidence of SOEC was reported in a Korean population (2.6%) compared with white subjects (64.6%).9 Because China is part of East Asia, as is Korea, we presumed a low incidence of SOEC in the normal Chinese population. The aim of this study was to look at the incidence of SOEC in normal Chinese subjects, assessed by spiral CT scanning. Moreover, we present the results of endoscopic dissection of 11 cases of chronic rhinosinusitis in 11 patients with 12 SOECs.
METHODS The protocol was approved by Institutional Committee of Beijing Institute of Otolaryngology.
Received April 23, 2007; revised May 29, 2007; accepted June 26, 2007.
0194-5998/$32.00 © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved. doi:10.1016/j.otohns.2007.06.737
Zhang el al
CT and endoscopic analysis of SOEC . . .
CT Analysis of SOEC The CT analysis was performed at the Department of Otolaryngology–Head and Neck Surgery and the Department of Radiology, Beijing TongRen Hospital (affiliated with the Capital Medical University). From November 2004 to December 2006, 202 subjects (404 sides of the frontal region) with no previous clinical history of frontal sinus disease were identified. These subjects were either patients with no frontal sinus disease or volunteers. The mean ⫾ SD age of subjects was 39.4 ⫾ 13.5 years (range, 17 to 81 years). Gender distribution was 121 men and 81 women. Spiral CT scans of the nasal cavities and paranasal sinuses were performed with a GE LightSpeed CT scanner (GE Medical Systems, Milwaukee, WI) with overlapping axial cuts of 0.625 mm thickness. The scanning parameters used were 120 kV and 400 mA, and intermediate window and level settings were 2500 HU and 300 HU, respectively. The images were then forwarded to an imaging laboratory and evaluated with a standard triplanar reconstruction protocol on a computer workstation (Volume Viewer, GE Medical Systems). We evaluated images for the presence of SOEC as well as other fronto-ethmoid cells with the criteria defined by Lee et al,7 which was a combination of traditional concepts and contemporary knowledge. Each CT scan was studied jointly by one of the consultant ENT surgeons (Zhang L and Han D) and one radiologist (Tao J). Because the radiologist read all the CTs, this allowed for minimized variability of interpretation between the 2 teams.
Endoscopic Analysis of SOEC We conducted a retrospective review of patients who had undergone endoscopic sinus surgery over a 1-year period (Department of Otolaryngology–Head and Neck Surgery at Beijing TongRen Hospital). CT scans of the nasal cavities and paranasal sinuses were performed on either a GE SYTEC4000i CT scanner (GE Medical Systems) with coronal and axial cuts of 2 mm thickness or the GE LightSpeed CT scanner, and intermediate window and level settings were 2000 HU and 200 HU, respectively. SOEC were generally determined by their radiographic location on coronal and axial images. The surgical plan for the patients would be uncinectomy followed by opening of the agger nasi cell by removal of its anterior and medial walls. After removal of the anterior wall of the ethmoid bulla, its above-sitting SOEC was identified. Anteriorly, structures that obstructed the frontal ostium, such as the terminal recess and/or FC, were removed. The openings of the SOEC and frontal sinus were identified, mostly with the use of a 70-degree endoscopy. Postoperatively, each patient was assessed by 30- or 70-degree nasal endoscopy for SOEC and frontal sinus patency.
RESULTS CT Analysis of SOEC Of the 404 sides from 202 subjects, the presence of SOEC was found in 22 (5.4%) sides. All 22 SOECs arose from the
563 anterior ethmoid cells. On coronal CT images an SOEC (Fig 1A) might initially give the appearance of multiple frontal sinuses (Fig 2A), type III FC (Fig 2B), FBC (Fig 2B), IFSC, or that there was a septation present within the frontal sinus. In Figure 1, what might appear to be the most lateral compartment of a septated frontal sinus was actually a separate ethmoid cell present posterior and lateral to the frontal sinus. With the images moving posteriorly, the lateral cell located immediately above the orbital bone appeared to become wider. Meanwhile, the medial 2 cells joined to become one cell (Fig 1A and B). The axial images illustrated that the location of the lateral cell was behind and lateral to the medial 2 cells, and the most medial cell was the pneumatization of the frontal septal (note the location of the crista galli), named IFSC (Fig 1B). The sagittal image confirmed the location of the SOEC. Furthermore, it illustrated that the origin of the cell was the anterior ethmoid sinus (Fig 1C). The appearance of more than one cell in the frontal region on the coronal image should require considering the presence of fronto-ethmoid cells. For example, the IFSC was the pneumatization of the frontal septal, usually illustrated on coronal and axial CT images. FBC might have a similar appearance on sagittal and axial CT images to SOEC (Fig 2C and D). However, differences were identified on coronal CT images (Fig 2B). In Figure 2, the initial coronal CT image illustrated two separated cells in the left frontal sinus (Fig 2A). The coronal image cut further behind illustrated a type III FC on the left side, which was confirmed by the left sagittal image. The type III FC was a single large ethmoid cell above the agger nasi cell (Fig 2B), and its superior wall inserted on the inner aspect of the anterior frontal sinus table. The FBC was an ethmoid cell above the ethmoid bulla (Fig 2D). It was located medially in the frontal region on the coronal image (Fig 2B). Although its posterosuperior wall was the anterior skull base, its anterior border extended into the frontal sinus (Fig 2D). The FBC might have anteroinferiorly compressed the simultaneouslypresented type III FC (Fig 2B and D).
Endoscopic Analysis of SOEC Eleven chronic rhinosinusitis patients (10 males and 1 female) with 12 SOECs, ranging in age from 25 to 58 (mean, 39.9) years, were identified. Of these, only one had previously undergone endoscopic sinus surgery. The most frequently reported symptoms were nasal obstruction (82%), mucous rhinorrhea (73%), headache (64%), and hyposmia (55%). CT scan findings demonstrated one patient had two SOECs. The remaining 10 patients had one SOEC each. All 12 SOECs originated from the anterior ethmoid cell (Fig 3) and the cell extended superolaterally between the lamina papyracea and the roof of the ethmoid to pneumatize the orbital plate of the frontal bone. Intraoperatively, the SOEC was first identified after removal of the anterior wall of the ethmoid bulla, and its recess location gave the impression of a frontal ostium location. This configuration altered the frontal drainage
564
Otolaryngology–Head and Neck Surgery, Vol 137, No 4, October 2007
Figure 1 (A) Coronal plane CT images illustrates two cells in the left frontal region. The most lateral one is the SOEC (**) and the medial one is the frontal sinus merged with the IFSC (*). (B) Axial plane CT images illustrates three cells in the left frontal region. The most lateral one is the SOEC (**), the most medial one is the IFSC (*), and in the middle is the frontal sinus. The crista galli is indicated (arrow). (C) Left saggital plane CT image demonstrates the SOEC originated from the ethmoid sinus. (ANC, agger nasi cell; EB, ethmoid bullar)
pathway as the SOEC pushed the pathway anteriorly. The frontal ostium was anterior and medial to the SOEC recess, which was mostly blocked by the insertion of the uncinate process onto the lamina papyracea, the terminal
recess. The surgeon could fully expose the frontal recess by passing the curette behind the posterior wall of the agger nasi cell and fracturing the posterior wall and roof of the agger nasi cell. Because the frontal ostium was
Zhang el al
CT and endoscopic analysis of SOEC . . .
565
Figure 2 (A) Coronal CT image illustrates two separated cells in the left frontal sinus (*). (B) Coronal image cut further behind illustrates a type III FC (**) above the agger nasi cell (A) on the left side. On the right side, beside a type III FC (**) above agger nasi cell (A), a FBC is indicated by the arrow. (C) Right sagittal image illustrates the agger nasi cell (A), type III FC (**), and the FBC (arrow). (D) Axial image illustrates a type III FC (**) on both sides, together with a FBC (arrow) on the left.
anterior and medial to the SOEC recess, which pushed the anterior skull base posteriorly, and the SOEC recess was anterior to the anterior ethmoid artery, the risk of damage to the anterior ethmoid artery was theoretically
less (Fig 3C). All the patients remain free of disease after endoscopic sinus surgery (range, 2 to 17 months; median, 10 months). This was documented by nasal endoscopy with or without CT scanning.
566
Otolaryngology–Head and Neck Surgery, Vol 137, No 4, October 2007
Figure 3 Chronic sinusitis patient with SOEC. (A) Coronal CT image illustrates two cells in the right frontal region. The lateral one is the SOEC (**) and the medial one is the frontal sinus (*). (B) Axial image illustrates the frontal sinus (*) and SOEC (**) on the right side. (C), Endoscopic view (70 degree) of the frontal sinus ostium (*) and the SOEC recess (**) on the side, which were separated by a thick bone separation.
DISCUSSION With the development of endoscopic frontal sinus surgery, the importance of both the anatomy1,3,15-18 and the CT4,7,9,10,12,19,20 of the frontal recess have been emphasized. High-resolution CT has extensively shown the intrinsic complexity of the anatomy of the frontal recess.7 SOEC3 and other fronto-ethmoid cells compromise the narrow frontal sinus drainage pathways and produce significant obstruction. The existence of SOEC in cadaver specimens was investigated about 50 years ago by Kasper, Van Alyea, and Dixon, and the presence rate ranged from 5% to 15%.3,8 By using spiral CT, the incidence of SOEC in 2 normal white
populations (⬃50 cases) were shown to be more than 60% (62%7 and 64.6%9). Moreover, Cho et al11 compared the incidence of SOEC in 57 Korean subjects with that in 41 white subjects. SOEC were overwhelmingly more frequent in the white (64.6%) population, compared with the Korean (2.6%) population, which might be attributable to the more pronounced glabella and superior orbital rim found in whites. Thus, we presumed that China, which is also located in East Asia, also has a lower incidence of SOEC. In our normal population of 202 subjects, the SOEC frequency (5.4%) was generally consistent with that of Korean subjects, which also hints an ethnic influence on the development of SOEC.
Zhang el al
CT and endoscopic analysis of SOEC . . .
It has been realized that the differential identification of SOEC, as well as other fronto-ethmoid cells, by using 3-dimensional CT is crucial. There was a possibility of presenting fronto-ethmoid cells when multiple cells appeared in the frontal region on coronal CT.3 These multiple cells should be considered as SOEC, multiple frontal sinuses, type III FC, FBC, or IFSC. Meanwhile, a tiny septation presented within the frontal sinus might also give the appearance of multiple cells. Generally speaking, while the type III FC, FBC, or IFSC was medial to the frontal sinus, the SOEC was lateral to the frontal sinus. Although IFSC were located in the frontal sinus, type III FC or FBC were posterior to IFSC. Both type III FC and FBC were above the agger nasi cell. However, coronal CT scanning alone was not enough to discriminate FBC from type III FC, although FBC were posterior to type III FC. Both sagittal CT and axial CT were extremely helpful for this discrimination. On the sagittal CT images, FBC and SOEC had a similar appearance. The difference in the two types of cells was the degree of frontal pneumatization. On coronal CT images, the SOEC was lateral to the frontal sinus, while the FBC was medial to the frontal sinus. Although the high prevalence of SOEC was reported with the use of CT analysis, endoscopic management of SOEC was rarely mentioned in the literature. In 1997, Owen and Kuhn3 reported three cases of revision endoscopic surgery with endoscopic exposure of SOEC. Later, 10 cases of supraorbital cell mucocele, which were managed endoscopically, were reported by Chiu and Vaughan.5 With a much lower prevalence of SOEC in China (5.4%), we reported 11 cases of chronic rhinosinusitis with 12 SOEC. In this series of 11 patients, all SOECs arose from the anterior ethmoid cells. To effectively eliminate disease in the frontal area, the surgeon must positively identify an opening into each of the cells during endoscopic surgery. When operating in the frontal recess, the surgeon must carefully locate two anatomic landmarks, the terminal recess and the ethmoid bulla. Nearly 90% of the superior uncinate process inserts onto the lamina papyracea to form the terminal recess. The frontal drainage pathway was between the posterior wall of the terminal recess and the anterior wall of the SOEC. The identification of the ethmoid bulla led the surgeon to its above-sitting SOEC. Because the SOEC recess was high in the anterior ethmoid roof, it could often be confused with the frontal ostium, and the removal of the terminal recess led to the full exposure of the frontal ostium. The existence of SOEC pushed the frontal drainage pathway anteriorly and narrowed the frontal recess. In conclusion, a thorough knowledge of anatomy and CT of the frontal recess and various fronto-ethmoid cells are required for safe dissection of SOEC and the frontal ostium. The SOEC recess is located posteriorly and laterally to the frontal ostium, and the anterior ethmoid artery is located posteriorly to the SOEC. Although enlarging the SOEC in the posterior direction could risk
567 injury to the anterior ethmoid artery, enlarging the frontal ostium in the posterior direction had a lower potential to cause injury to the artery.
AUTHOR INFORMATION From the Beijing Institute of Otolaryngology (Drs Zhang and Han) and the Departments of Otolaryngology–Head and Neck Surgery (Drs Zhang, Han, Ge, Wang, Li, and Zhou) and Radiology (Dr Tao), Beijing TongRen Hospital, Capital Medical University, Beijing, P. R. China. Corresponding author: Demin Han, 1, DongJiaoMinXiang Avenue, DongCheng District, Beijing, 100730 P. R. China. E-mail address: [email protected].
AUTHOR CONTRIBUTIONS Demin Han, study design; Luo Zhang, study design; Surgeon; CT analysis; Wentong Ge, surgeon; CT analysis; Jianhua Tao, CT analysis; Xianzhong Wang and Yunchuan Li, surgeons, Bing Zhou, editing.
AUTHOR DISCLOSURE None.
REFERENCES 1. Wormald PJ. Three-dimensional building block approach to understanding the anatomy of the frontal recess and frontal sinus. Operative Techniques in Otolaryngology 2006;17:2–5. 2. Wormald PJ. The agger nasi cell: the key to understanding the anatomy of the frontal recess. Otolaryngol Head Neck Surg 2003;129(5): 497–507. 3. Owen RG Jr, Kuhn FA. Supraorbital ethmoid cell. Otolaryngol Head Neck Surg 1997;116(2):254 – 61. 4. DelGaudio JM, Hudgins PA, Venkatraman G, et al. Multiplanar computed tomographic analysis of frontal recess cells: effect on frontal isthmus size and frontal sinusitis. Arch Otolaryngol Head Neck Surg 2005;131(3):230 –5. 5. Chiu AG, Vaughan WC. Management of the lateral frontal sinus lesion and the supraorbital cell mucocele. Am J Rhinol 2004;18(2):83– 6. 6. Bradley DT, Kountakis SE. The role of agger nasi air cells in patients requiring revision endoscopic frontal sinus surgery. Otolaryngol Head Neck Surg 2004;131(4):525–7. 7. Lee WT, Kuhn FA, Citardi MJ. 3D computed tomographic analysis of frontal recess anatomy in patients without frontal sinusitis. Otolaryngol Head Neck Surg 2004;131(3):164 –73. 8. Dixon FW. The clinical significance of the anatomical arrangement of the paranasal sinuses. Ann Otol Rhinol Laryngol 1958;67(3): 736 – 41. 9. Cho JH, Citardi MJ, Lee WT, et al. Comparison of frontal pneumatization patterns between Koreans and Caucasians. Otolaryngol Head Neck Surg 2006;135(5):780 – 6. 10. Landsberg R, Friedman M. A computer-assisted anatomical study of the nasofrontal region. Laryngoscope 2001;111(12):2125–30. 11. Meyer TK, Kocak M, Smith MM, et al. Coronal computed tomography analysis of frontal cells. Am J Rhinol 2003;17(3):163– 8. 12. Turgut S, Ercan I, Sayin I, et al. The relationship between frontal sinusitis and localization of the frontal sinus outflow tract: a computer-
568
13. 14. 15.
16.
Otolaryngology–Head and Neck Surgery, Vol 137, No 4, October 2007
assisted anatomical and clinical study. Arch Otolaryngol Head Neck Surg 2005;131(6):518 –22. Chiu AG, Vaughan WC. Revision endoscopic frontal sinus surgery with surgical navigation. Otolaryngol Head Neck Surg 2004;130(3):312– 8. Badia L, Lund VJ, Wei W, et al. Ethnic variation in sinonasal anatomy on CT-scanning. Rhinology 2005;43(3):210 – 4. Daniels DL, Mafee MF, Smith MM, et al. The frontal sinus drainage pathway and related structures. AJNR Am J Neuroradiol 2003;24(8): 1618 –27. Friedman M, Bliznikas D, Vidyasagar R, et al. Frontal sinus surgery 2004: update of clinical anatomy and surgical techniques. Operative Techniques Otolaryngol Head Neck Surg 2004;15(1):23-31.
17. Kuhn FA, Bolger WE, Tisdal RG. The agger nasi cell in frontal recess obstruction: an anatomic, radiologic and clinical correlation. Operative Techniques Otolaryngol Head Neck Surg 1991;2: 226 –32. 18. Zhang L, Han D, Ge W, et al. Anatomical and computed tomographic analysis of the interaction between the uncinate process and the agger nasi cell. Acta Otolaryngol 2006;126(8):845–52. 19. Coates MH, Whyte AM, Earwaker JW. Frontal recess air cells: spectrum of CT appearances. Australas Radiol 2003;47(1):4 –10. 20. Kew J, Rees GL, Close D, et al. Multiplanar reconstructed computed tomography images improves depiction and understanding of the anatomy of the frontal sinus and recess. Am J Rhinol 2002;16(2):119 –23.