ANATOMICAL STUDY
Transnasal Approach to the Anterior Skull Base: An Endoscopic Anatomic Study Yu Zong, MD,* Xiangcui Li, MD,* Yiming Jiang, MD,*Þ Ji Xu, MD,* and Jiping Li, MD, PhD*Þ
Objective: The purpose of this study was to locate the constant anatomic landmarks for anterior skull base surgery via endoscopic transnasal approach in Chinese subjects. Methods: Eight cases of adult skull specimens (all Chinese) were dissected by the endoscopic transnasal approach. The relationships of the anatomic landmarks under endoscopic view were characterized. The distance between the columella and the anterior ethmoid artery (AEA) or the posterior ethmoid artery (PEA) was measured. Results: The uncinate process attached to the lamina papyracea in 7 sides (43.8%), to the skull base in 4 sides (25%), and to the middle turbinate in 3 sides (18.8%). In addition, the uncinate process was found to have bifurcated attachment in 2 sides (12.5%).The mean T SD distance from the columella to the AEA was 62.71 T 2.18 mm on the right side and 63.38 T 1.69 mm on the left side. The mean T SD distance from the columella to the PEA was 70.91 T 1.99 mm on the right side and 71.79 T 1.95 mm on the left side. Conclusions: The frontal recess, the AEA, and the PEA can serve as the constant landmarks in the transnasal endoscopic approach to the anterior skull base.
The objectives of this study were to locate the constant anatomic landmarks for this surgical approach and to characterize their relationships under endoscopic view.
MATERIALS AND METHODS Skull Specimens Eight complete head specimens (all Chinese) were used, 6 of which were fixed with 10% formalin and 2 of which were fresh. The samples were rinsed under pressure with saline for approximately 20 minutes through bilateral internal carotid arteries, followed by continuous infusion with saline for 1 to 3 hours to remove the remaining endovascular clots. The samples were placed horizontally overnight. One side of the internal carotid artery was ligated, and the contralateral carotid artery was used as the infusion blood vessel. The prepared red latex was injected slowly with appropriate and even pressure. The ligated internal carotid artery was opened when obvious resistance was felt. The infusion was stopped when the latex overflowed, and then the infusion artery was clamped and ligated.
Dissection and Observation Methods
A
The observational instrument was the Stryker endoscopy system, which includes 0-degree and 30-degree rigid endoscopes (length, 18 cm; diameter, 4 mm). Other equipments used included the conventional nasal endoscopic surgery equipments and the electric drill. The anterior wall of the agger nasi cell was removed to expose the upper part of the uncinate process. The whole length of the uncinate process was then resected, and the frontal recess was identified. A probe was used to locate the frontal sinus ostium. The frontal beak was then drilled to enlarge the frontal sinus ostium. The anterior ethmoid sinus was opened, and the surrounding cells were eliminated. Thereafter, the bony canal of the anterior ethmoid artery (AEA) was identified. The posterior ethmoid sinus was removed until the skull base was reached. The bony canal of the posterior ethmoid artery (PEA) was recognized. The relationships of the anatomic landmarks under endoscope were characterized. The distance between the columella and the AEA or the PEA was measured.
From the Department of Otorhinolaryngology Head and Neck Surgery, Ren Ji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People’s Republic of China; and †Institution of Otorhinolaryngology of Shanghai Jiaotong University, Shanghai, People’s Republic of China. Received June 23, 2013. Accepted for publication November 13, 2013. Address correspondence and reprint requests to Dr. Jiping Li, Department of Otorhinolaryngology Head and Neck Surgery, Ren Ji Hospital, 1630 Dong Fang Rd, Shanghai 200127, People’s Republic of China; E-mail: [email protected] Supported by Shanghai Public Health Bureau (no. 01457). The authors report no conflicts of interest. Copyright * 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000562
The agger nasi was observed anterior to the middle turbinate, namely, the axillary of the middle turbinate. One or 2 cells were found to exist in the agger nasi. After eliminating the cells, the upper part of the uncinate process was observed to form part of the posterior wall of the agger nasi. The frontal recess was then exposed after removal of the upper part of the uncinate process. Four types of attachment of the uncinate process were observed in our study. The uncinate process attached to the lamina papyracea in 7 sides (43.8%), to the skull base in 4 sides (25%), and to the middle turbinate in 3 sides (18.8%). In addition, the uncinate process was found to have bifurcated attachment in 2 sides (12.5%). The frontal sinus drained into the middle meatus in 7 sides (43.8%) when the uncinate process attached to the lamina papyracea. It drained into the ethmoid
Key Words: Endoscope, anterior skull base, transnasal approach, anatomic landmark (J Craniofac Surg 2014;25: 1041Y1043)
wide range of diseases including tumors and chronic infection may occur in the region of the anterior skull base.1,2 Transnasal endoscopic approach can provide convenient access to almost all regions of the anterior skull base and avoid the need for an external incision. The traditional transcranial procedures are gradually substituted by the less invasive endoscopic surgery because of fewer complications and better outcomes.3Y6 The characteristic anatomy under endoscope is distinctively different from the gross anatomy. To avoid serious complications during the surgical procedure, it is necessary for a surgeon to be familiar with the endoscopic anatomy.
The Journal of Craniofacial Surgery
RESULTS
& Volume 25, Number 3, May 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1041
The Journal of Craniofacial Surgery
Zong et al
& Volume 25, Number 3, May 2014
infundibulum in 9 sides (56.2%), with the uncinate process attaching to the skull base or to the middle turbinate or the bifurcated attachment. The AEA was observed in the bony canal, which was located within the range of 2 to 3 mm behind the posterior border of the frontal recess, and coursed superiorly from the lateral to the medial side (Fig. 1). Among the 16 dissections in this study, the anterior ethmoid bony canal was observed to protrude from the skull base in 10 sides (62.5%) and embedded in the ethmoid plate without protuberance in 6 sides (37.5%). The PEA was observed to pass through the bony canal located in front of the anterior wall of the sphenoid sinus. The canals of the posterior arteries were all embedded in the skull base (Fig. 2). The mean T SD distance from the columella to the AEA was 62.71 T 2.18 mm (range from 60.2 to 66.8 mm) on the right side and 63.38 T 1.69 mm (range from 60.2 to 65.8 mm) on the left side. The mean T SD distance from the columella to the PEAwas 70.91 T 1.99 mm (range from 69.1 to 74.6 mm) on the right side and 71.79 T 1.95 mm (range from 69.3 to 73.9 mm) on the left side (Table 1).
DISCUSSION Endoscopic Anatomic Landmarks of the Anterior Skull Base and Relevant Anatomy The agger nasi cell is one of the most anterior cells of the ethmoid. Being anterior to the axillary of the middle turbinate, the agger nasi can be easily located and serves as an endoscopic landmark. The middle turbinate is another important anatomic landmark for endoscopic skull base surgery. The vertical lamella of the middle turbinate attaches to the skull base. The horizontal lamella (basal lamella) separates the anterior from the posterior ethmoid cells. The well pneumatic agger nasi cells can push the middle turbinate anteriorly and medially.7,8 The uncinate process lies laterally to the middle turbinate and extends from the maxillary ostium to the frontal recess.9 Identification of the uncinate process is very important during the endoscopic surgery because the uncinate process serves as a constant anatomic landmark. The superior attachment of the uncinate process has instructional significance for locating the frontal passage.10 Attachment to the lamina papyracea is the most common type, which occurred in 7 sides (48.2%) in this study. In this type, the frontal sinus drains into the middle meatus. The surgeon should probe the frontal
FIGURE 2. Relationship of the skull base and the lamina papyracea. The AEA attaches to the skull base. The posterior artery is embedded in the posterior part of the skull base. ASB indicates anterior skull base; FR, frontal recess; LP, lamina papyracea.
recess medially to the uncinate process. When the uncinate process attaches to the skull base or the middle turbinate, the sinus drains into the ethmoid infundibulum and the frontal passage lies laterally to the uncinate process. After resection of the uncinate process, the frontal recess serves as the further anatomic landmark.11 The frontal recess is neighbored by the lateral wall of the olfactory recess medially and the lamina papyracea of the orbit laterally. The base of the frontal sinus is recognized after exposure of the frontal recess. The safety range of the frontal sinus base is the anterior skull base posteriorly and the lamina papyracea laterally. The posterior wall of the frontal sinus forms the most anteroinferior boundary of the anterior cranial fossa and is in close contact with the frontal lobes, separated only by the dura mater.12 Considering the anatomic relationship, the posterior border of the frontal sinus should be located firstly during an operation in this region. Any manipulation should be confined to the region anterior to it and medial to the lamina papyracea.
Location and Protection of the Anterior Skull Base Because of unfamiliarity with endoscopic anatomy, the skull base might be injured accidentally during operation associated with TABLE 1. Distance From the Columella to the AEA or to the PEA in 8 Cadaveric Heads Cadaver No.
FIGURE 1. Anatomic relationship of the frontal recess. The frontal recess is the drainage passage of the frontal sinus located lateral-posterior to the uncinate process. The canal of the AEA is behind the posterior border of the frontal recess. ASB indicates anterior skull base; FR, frontal recess; FS, frontal sinus; UP, uncinate process.
1042
1 2 3 4 5 6 7 8 Mean SD
Right Side, mm
Left Side, mm
C-AEA
C-PEA
C-AEA
C-PEA
63.3 66.8 62.8 60.4 64.2 62.8 61.2 60.2 62.71 2.18
71.7 74.6 69.1 70.8 72.8 69.9 69.1 69.3 70.91 1.99
64.6 63.8 62.8 63.4 64.2 65.8 60.2 62.2 63.38 1.69
73.7 70.6 70.1 72.8 73.8 73.9 70.1 69.3 71.79 1.95
C-AEA indicates distance from the columella to the AEA; C-PEA, distance from the columella to the PEA.
* 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery
& Volume 25, Number 3, May 2014
cerebrospinal leakage.13 Therefore, accurate identification of the skull base is the key point of a safe operation. Frontal recess could serve as one of the anatomic landmarks, to which the skull base is superior-posterior. As mentioned above, the exposure of the frontal recess is affected by the attachment of the uncinate process and the aerification of the arger nasi. It is important to resect both of them thoroughly to reach the frontal recess. Thereafter, the AEA behind the posterior border of the frontal recess could be located. Positioning the AEA has important significance, which is as follows: (1) The recognition of the AEA makes it possible to carry out cauterization in case of catastrophic bleeding. (2) The plane of AEA could serve as a safety surgical plane. Any manipulation exceeding this plane should be reminded of injuring the dura mater. (3) The position of the AEA is less variable, which makes it a constant landmark to ensure protection of the dura mater. In this study, the AEA canal forms a protuberance in 10 sides (62.5%) of the cadavers. Considering the weakness of the canal bone, the AEA is easy to be injured by violent manipulation. On the contrary, the PEA was found being embedded in the ethmoid plate, making it less vulnerable. Another possibility to locate the anterior skull base is by referring the relationship of the lamina papyracea and the ethmoid roof. Because the anterior skull base is mainly composed of the ethmoid roof, it could be observed by tracing the lamina papyracea upwardly until reaching the ethmoid roof. Because of the variable relationship between the lamina papyracea and the ethmoid roof, the orientation of the endoscope should be adjusted according to the angle between the lamina papyracea and the ethmoid roof. The following procedure is helpful to position the ethmoid roof: First, skeletonize the lamina papyracea by eliminating the ethmoidal cells to get a clear overall view. Second, trace the lamina papyracea upwardly by removing the remnant cell attaching to the ethmoid roof carefully until the flaxen thick bone of the ethmoid roof is viewed. Third, obtain an overall view of the ethmoid roof by eliminating the remaining bone pieces. The skull base is at the same anatomic plane as the ethmoid roof.14 This procedure can provide safe and effective protection for the skull base, especially in recurrent cases.
CONCLUSIONS The frontal recess, the AEA, and the PEA can serve as the constant landmarks in the transnasal endoscopic approach to the anterior skull base. Understanding the relationships among these constant landmarks is helpful to locate and protect the skull base.
Transnasal Approach to Skull Base
REFERENCES 1. Liu JK, O’Neill B, Orlandi RR, et al. Endoscopic-assisted craniofacial resection of esthesioneuroblastoma: minimizing facial incisionsVtechnical note and report of 3 cases. Minim Invasive Neurosurg 2003;46:310Y315 2. Yuen APW, Fan YW, Fung CF, et al. Endoscopic-assisted cranionasal resection of olfactory neuroblastoma. Head Neck 2005;27:488Y493 3. Eloy JA, Vivero RJ, Hoang K, et al. Comparison of transnasal endoscopic and open craniofacial resection for malignant tumors of the anterior skull base. Laryngoscope 2009;18:518Y526 4. Carrau RL, Kassam AB, Snyderman CH, et al. Endoscopic transnasal anterior skull base resection for the treatment of sinonasal malignancies. Oper Tech Otolaryngol 2006;17:102Y110 5. Gardner PA, Kassam AB, Thomas A, et al. Endoscopic endonasal resection of anterior cranial base meningiomas. Neurosurgery 2008;63: 36Y52 6. Russell PT, Weaver KD. Anterior endoscopic skull-base surgery getting started: an otolaryngologist’s perspective. Curr Opin Otolaryngol Head Neck Surg 2007;15:1Y5 7. Wormald PJ. The axillary flap approach to the frontal recess. Laryngoscope 2002;112:494Y499 8. Yanagisawa E, Mirante JP, Christmas DA. Vertical insertion of the middle turbinate: a sign of the presence of a well-developed agger nasi cell. Ear Nose Throat J 2002;81:818Y819 9. Kim KS, Kim HU, Chung TH, et al. Surgical anatomy of the nasofrontal duct anatomical and computed tomographic analysis. Laryngoscope 2001;111:603Y608 10. Liu SC, Wang CH, Wang HW. Prevalence of the uncinate process, agger nasi cell and their relationship in a Taiwanese population. Rhinology 2010;48:239Y244 11. Lessa MM, Voegels RL, Cunha Filho B, et al. Frontal recess anatomy study by endoscopic dissection in cadavers. Braz J Otorhinolaryngol 2007;73:204Y209 12. Friedman M, Bliznikas D, Vidyasagar R, et al. Frontal sinus surgery: update of clinical anatomy and surgical techniques. Oper Tech Otolaryngol Head Neck Surg 2004;15:23Y318 13. Platt MP, Parnes SM. Management of unexpected cerebrospinal fluid leak during endoscopic sinus surgery. Curr Opin Otolaryngol Head Neck Surg 2009;17:28Y32 ¨ , Polat K, et al. Analysis of ethmoid roof and skull base 14. Gu¨ler C, Uysal IO with coronal section paranasal sinus computed tomography. J Craniofac Surg 2012;23:1460Y1464
* 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1043
Transnasal Approach to the Anterior Skull Base: An Endoscopic Anatomic Study Yu Zong, MD,* Xiangcui Li, MD,* Yiming Jiang, MD,*Þ Ji Xu, MD,* and Jiping Li, MD, PhD*Þ
Objective: The purpose of this study was to locate the constant anatomic landmarks for anterior skull base surgery via endoscopic transnasal approach in Chinese subjects. Methods: Eight cases of adult skull specimens (all Chinese) were dissected by the endoscopic transnasal approach. The relationships of the anatomic landmarks under endoscopic view were characterized. The distance between the columella and the anterior ethmoid artery (AEA) or the posterior ethmoid artery (PEA) was measured. Results: The uncinate process attached to the lamina papyracea in 7 sides (43.8%), to the skull base in 4 sides (25%), and to the middle turbinate in 3 sides (18.8%). In addition, the uncinate process was found to have bifurcated attachment in 2 sides (12.5%).The mean T SD distance from the columella to the AEA was 62.71 T 2.18 mm on the right side and 63.38 T 1.69 mm on the left side. The mean T SD distance from the columella to the PEA was 70.91 T 1.99 mm on the right side and 71.79 T 1.95 mm on the left side. Conclusions: The frontal recess, the AEA, and the PEA can serve as the constant landmarks in the transnasal endoscopic approach to the anterior skull base.
The objectives of this study were to locate the constant anatomic landmarks for this surgical approach and to characterize their relationships under endoscopic view.
MATERIALS AND METHODS Skull Specimens Eight complete head specimens (all Chinese) were used, 6 of which were fixed with 10% formalin and 2 of which were fresh. The samples were rinsed under pressure with saline for approximately 20 minutes through bilateral internal carotid arteries, followed by continuous infusion with saline for 1 to 3 hours to remove the remaining endovascular clots. The samples were placed horizontally overnight. One side of the internal carotid artery was ligated, and the contralateral carotid artery was used as the infusion blood vessel. The prepared red latex was injected slowly with appropriate and even pressure. The ligated internal carotid artery was opened when obvious resistance was felt. The infusion was stopped when the latex overflowed, and then the infusion artery was clamped and ligated.
Dissection and Observation Methods
A
The observational instrument was the Stryker endoscopy system, which includes 0-degree and 30-degree rigid endoscopes (length, 18 cm; diameter, 4 mm). Other equipments used included the conventional nasal endoscopic surgery equipments and the electric drill. The anterior wall of the agger nasi cell was removed to expose the upper part of the uncinate process. The whole length of the uncinate process was then resected, and the frontal recess was identified. A probe was used to locate the frontal sinus ostium. The frontal beak was then drilled to enlarge the frontal sinus ostium. The anterior ethmoid sinus was opened, and the surrounding cells were eliminated. Thereafter, the bony canal of the anterior ethmoid artery (AEA) was identified. The posterior ethmoid sinus was removed until the skull base was reached. The bony canal of the posterior ethmoid artery (PEA) was recognized. The relationships of the anatomic landmarks under endoscope were characterized. The distance between the columella and the AEA or the PEA was measured.
From the Department of Otorhinolaryngology Head and Neck Surgery, Ren Ji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People’s Republic of China; and †Institution of Otorhinolaryngology of Shanghai Jiaotong University, Shanghai, People’s Republic of China. Received June 23, 2013. Accepted for publication November 13, 2013. Address correspondence and reprint requests to Dr. Jiping Li, Department of Otorhinolaryngology Head and Neck Surgery, Ren Ji Hospital, 1630 Dong Fang Rd, Shanghai 200127, People’s Republic of China; E-mail: [email protected] Supported by Shanghai Public Health Bureau (no. 01457). The authors report no conflicts of interest. Copyright * 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000562
The agger nasi was observed anterior to the middle turbinate, namely, the axillary of the middle turbinate. One or 2 cells were found to exist in the agger nasi. After eliminating the cells, the upper part of the uncinate process was observed to form part of the posterior wall of the agger nasi. The frontal recess was then exposed after removal of the upper part of the uncinate process. Four types of attachment of the uncinate process were observed in our study. The uncinate process attached to the lamina papyracea in 7 sides (43.8%), to the skull base in 4 sides (25%), and to the middle turbinate in 3 sides (18.8%). In addition, the uncinate process was found to have bifurcated attachment in 2 sides (12.5%). The frontal sinus drained into the middle meatus in 7 sides (43.8%) when the uncinate process attached to the lamina papyracea. It drained into the ethmoid
Key Words: Endoscope, anterior skull base, transnasal approach, anatomic landmark (J Craniofac Surg 2014;25: 1041Y1043)
wide range of diseases including tumors and chronic infection may occur in the region of the anterior skull base.1,2 Transnasal endoscopic approach can provide convenient access to almost all regions of the anterior skull base and avoid the need for an external incision. The traditional transcranial procedures are gradually substituted by the less invasive endoscopic surgery because of fewer complications and better outcomes.3Y6 The characteristic anatomy under endoscope is distinctively different from the gross anatomy. To avoid serious complications during the surgical procedure, it is necessary for a surgeon to be familiar with the endoscopic anatomy.
The Journal of Craniofacial Surgery
RESULTS
& Volume 25, Number 3, May 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1041
The Journal of Craniofacial Surgery
Zong et al
& Volume 25, Number 3, May 2014
infundibulum in 9 sides (56.2%), with the uncinate process attaching to the skull base or to the middle turbinate or the bifurcated attachment. The AEA was observed in the bony canal, which was located within the range of 2 to 3 mm behind the posterior border of the frontal recess, and coursed superiorly from the lateral to the medial side (Fig. 1). Among the 16 dissections in this study, the anterior ethmoid bony canal was observed to protrude from the skull base in 10 sides (62.5%) and embedded in the ethmoid plate without protuberance in 6 sides (37.5%). The PEA was observed to pass through the bony canal located in front of the anterior wall of the sphenoid sinus. The canals of the posterior arteries were all embedded in the skull base (Fig. 2). The mean T SD distance from the columella to the AEA was 62.71 T 2.18 mm (range from 60.2 to 66.8 mm) on the right side and 63.38 T 1.69 mm (range from 60.2 to 65.8 mm) on the left side. The mean T SD distance from the columella to the PEAwas 70.91 T 1.99 mm (range from 69.1 to 74.6 mm) on the right side and 71.79 T 1.95 mm (range from 69.3 to 73.9 mm) on the left side (Table 1).
DISCUSSION Endoscopic Anatomic Landmarks of the Anterior Skull Base and Relevant Anatomy The agger nasi cell is one of the most anterior cells of the ethmoid. Being anterior to the axillary of the middle turbinate, the agger nasi can be easily located and serves as an endoscopic landmark. The middle turbinate is another important anatomic landmark for endoscopic skull base surgery. The vertical lamella of the middle turbinate attaches to the skull base. The horizontal lamella (basal lamella) separates the anterior from the posterior ethmoid cells. The well pneumatic agger nasi cells can push the middle turbinate anteriorly and medially.7,8 The uncinate process lies laterally to the middle turbinate and extends from the maxillary ostium to the frontal recess.9 Identification of the uncinate process is very important during the endoscopic surgery because the uncinate process serves as a constant anatomic landmark. The superior attachment of the uncinate process has instructional significance for locating the frontal passage.10 Attachment to the lamina papyracea is the most common type, which occurred in 7 sides (48.2%) in this study. In this type, the frontal sinus drains into the middle meatus. The surgeon should probe the frontal
FIGURE 2. Relationship of the skull base and the lamina papyracea. The AEA attaches to the skull base. The posterior artery is embedded in the posterior part of the skull base. ASB indicates anterior skull base; FR, frontal recess; LP, lamina papyracea.
recess medially to the uncinate process. When the uncinate process attaches to the skull base or the middle turbinate, the sinus drains into the ethmoid infundibulum and the frontal passage lies laterally to the uncinate process. After resection of the uncinate process, the frontal recess serves as the further anatomic landmark.11 The frontal recess is neighbored by the lateral wall of the olfactory recess medially and the lamina papyracea of the orbit laterally. The base of the frontal sinus is recognized after exposure of the frontal recess. The safety range of the frontal sinus base is the anterior skull base posteriorly and the lamina papyracea laterally. The posterior wall of the frontal sinus forms the most anteroinferior boundary of the anterior cranial fossa and is in close contact with the frontal lobes, separated only by the dura mater.12 Considering the anatomic relationship, the posterior border of the frontal sinus should be located firstly during an operation in this region. Any manipulation should be confined to the region anterior to it and medial to the lamina papyracea.
Location and Protection of the Anterior Skull Base Because of unfamiliarity with endoscopic anatomy, the skull base might be injured accidentally during operation associated with TABLE 1. Distance From the Columella to the AEA or to the PEA in 8 Cadaveric Heads Cadaver No.
FIGURE 1. Anatomic relationship of the frontal recess. The frontal recess is the drainage passage of the frontal sinus located lateral-posterior to the uncinate process. The canal of the AEA is behind the posterior border of the frontal recess. ASB indicates anterior skull base; FR, frontal recess; FS, frontal sinus; UP, uncinate process.
1042
1 2 3 4 5 6 7 8 Mean SD
Right Side, mm
Left Side, mm
C-AEA
C-PEA
C-AEA
C-PEA
63.3 66.8 62.8 60.4 64.2 62.8 61.2 60.2 62.71 2.18
71.7 74.6 69.1 70.8 72.8 69.9 69.1 69.3 70.91 1.99
64.6 63.8 62.8 63.4 64.2 65.8 60.2 62.2 63.38 1.69
73.7 70.6 70.1 72.8 73.8 73.9 70.1 69.3 71.79 1.95
C-AEA indicates distance from the columella to the AEA; C-PEA, distance from the columella to the PEA.
* 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery
& Volume 25, Number 3, May 2014
cerebrospinal leakage.13 Therefore, accurate identification of the skull base is the key point of a safe operation. Frontal recess could serve as one of the anatomic landmarks, to which the skull base is superior-posterior. As mentioned above, the exposure of the frontal recess is affected by the attachment of the uncinate process and the aerification of the arger nasi. It is important to resect both of them thoroughly to reach the frontal recess. Thereafter, the AEA behind the posterior border of the frontal recess could be located. Positioning the AEA has important significance, which is as follows: (1) The recognition of the AEA makes it possible to carry out cauterization in case of catastrophic bleeding. (2) The plane of AEA could serve as a safety surgical plane. Any manipulation exceeding this plane should be reminded of injuring the dura mater. (3) The position of the AEA is less variable, which makes it a constant landmark to ensure protection of the dura mater. In this study, the AEA canal forms a protuberance in 10 sides (62.5%) of the cadavers. Considering the weakness of the canal bone, the AEA is easy to be injured by violent manipulation. On the contrary, the PEA was found being embedded in the ethmoid plate, making it less vulnerable. Another possibility to locate the anterior skull base is by referring the relationship of the lamina papyracea and the ethmoid roof. Because the anterior skull base is mainly composed of the ethmoid roof, it could be observed by tracing the lamina papyracea upwardly until reaching the ethmoid roof. Because of the variable relationship between the lamina papyracea and the ethmoid roof, the orientation of the endoscope should be adjusted according to the angle between the lamina papyracea and the ethmoid roof. The following procedure is helpful to position the ethmoid roof: First, skeletonize the lamina papyracea by eliminating the ethmoidal cells to get a clear overall view. Second, trace the lamina papyracea upwardly by removing the remnant cell attaching to the ethmoid roof carefully until the flaxen thick bone of the ethmoid roof is viewed. Third, obtain an overall view of the ethmoid roof by eliminating the remaining bone pieces. The skull base is at the same anatomic plane as the ethmoid roof.14 This procedure can provide safe and effective protection for the skull base, especially in recurrent cases.
CONCLUSIONS The frontal recess, the AEA, and the PEA can serve as the constant landmarks in the transnasal endoscopic approach to the anterior skull base. Understanding the relationships among these constant landmarks is helpful to locate and protect the skull base.
Transnasal Approach to Skull Base
REFERENCES 1. Liu JK, O’Neill B, Orlandi RR, et al. Endoscopic-assisted craniofacial resection of esthesioneuroblastoma: minimizing facial incisionsVtechnical note and report of 3 cases. Minim Invasive Neurosurg 2003;46:310Y315 2. Yuen APW, Fan YW, Fung CF, et al. Endoscopic-assisted cranionasal resection of olfactory neuroblastoma. Head Neck 2005;27:488Y493 3. Eloy JA, Vivero RJ, Hoang K, et al. Comparison of transnasal endoscopic and open craniofacial resection for malignant tumors of the anterior skull base. Laryngoscope 2009;18:518Y526 4. Carrau RL, Kassam AB, Snyderman CH, et al. Endoscopic transnasal anterior skull base resection for the treatment of sinonasal malignancies. Oper Tech Otolaryngol 2006;17:102Y110 5. Gardner PA, Kassam AB, Thomas A, et al. Endoscopic endonasal resection of anterior cranial base meningiomas. Neurosurgery 2008;63: 36Y52 6. Russell PT, Weaver KD. Anterior endoscopic skull-base surgery getting started: an otolaryngologist’s perspective. Curr Opin Otolaryngol Head Neck Surg 2007;15:1Y5 7. Wormald PJ. The axillary flap approach to the frontal recess. Laryngoscope 2002;112:494Y499 8. Yanagisawa E, Mirante JP, Christmas DA. Vertical insertion of the middle turbinate: a sign of the presence of a well-developed agger nasi cell. Ear Nose Throat J 2002;81:818Y819 9. Kim KS, Kim HU, Chung TH, et al. Surgical anatomy of the nasofrontal duct anatomical and computed tomographic analysis. Laryngoscope 2001;111:603Y608 10. Liu SC, Wang CH, Wang HW. Prevalence of the uncinate process, agger nasi cell and their relationship in a Taiwanese population. Rhinology 2010;48:239Y244 11. Lessa MM, Voegels RL, Cunha Filho B, et al. Frontal recess anatomy study by endoscopic dissection in cadavers. Braz J Otorhinolaryngol 2007;73:204Y209 12. Friedman M, Bliznikas D, Vidyasagar R, et al. Frontal sinus surgery: update of clinical anatomy and surgical techniques. Oper Tech Otolaryngol Head Neck Surg 2004;15:23Y318 13. Platt MP, Parnes SM. Management of unexpected cerebrospinal fluid leak during endoscopic sinus surgery. Curr Opin Otolaryngol Head Neck Surg 2009;17:28Y32 ¨ , Polat K, et al. Analysis of ethmoid roof and skull base 14. Gu¨ler C, Uysal IO with coronal section paranasal sinus computed tomography. J Craniofac Surg 2012;23:1460Y1464
* 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1043
