- Email: [email protected]
Clinical significance of MRI-aided measurements in the transsphenoidal approach in Chinese adults
Journal of Clinical Neuroscience 17 (2010) 1523–1526
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Clinical Study
Clinical significance of MRI-aided measurements in the transsphenoidal approach in Chinese adults Chunlin Wang , Yuan Pan , Yicheng Lu ⇑, Xuehua Ding Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai 200003, China
a r t i c l e
i n f o
Article history: Received 28 October 2009 Accepted 15 April 2010
Keywords: Anatomical imaging MRI Transsphenoidal approach
a b s t r a c t To determine the optimal direction for approaching sellar tumors, we developed an anatomical model of the most common approach, the transsphenoidal approach, in Chinese adults by analyzing MRI-aided measurements. Craniocerebral MRI of 75 Chinese adults with pituitary tumors and 238 healthy Chinese adults were obtained to analyse the angle between the direction of the transsphenoidal approach and the reference line linking the glabella and the external occipital tubercle, the approach depth, and the distance between the internal carotid arteries (ICA) at the cavernous sinuses segment. The mean angle (± standard deviation [SD]) between the direction of the transsphenoidal approach and the reference line in patients with sellar tumors was 40.51 ± 2.98°, similar to the angle in the healthy control group (41.18 ± 3.35°) (p > 0.05). The mean depth (± SD) calculated via the transsphenoidal approach in the sellar tumor group was 86.01 ± 4.99 mm, which was similar to the control group (85.34 ± 4.96 mm) (p > 0.05). However, the mean distance (± SD) between the bilateral ICA at the cavernous sinuses in the patients with sellar tumors was 22.68 ± 5.03 mm, greater than in the control group (15.89 ± 3.11 mm) (p < 0.01). Thus, during sellar tumor resection via the transsphenoidal approach, the patient’s head should be first positioned to allow the line linking the glabella and the external occipital tubercle to be perpendicular to the horizontal plane, and then inclined backwards at an angle of about 40°. The floor of the sella, at a depth of about 85 mm, can then be reached vertically by introducing a speculum via a single nostril. The operative field should be limited to about 1 cm from the midline. By adopting this method, the optimal angle and depth of the transsphenoidal approach can be determined without complicated equipment. Moreover, this technique is simple and accurate enough to maintain the correct approach, locate the lesion, and reduce the incidence of serious postoperative complications, including bleeding caused by rupture of the ICA. Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction The transsphenoidal approach is the most commonly used for pituitary tumor resection.1 This approach is also used for the resection of craniopharyngiomas, tuberculum sellae meningiomas, and notochordomas.2–6 Although the safety of such surgical procedures has improved with advances in operative technique, such procedures are still associated with severe life-threatening complications, including massive hemorrhage. The risk of fatal injury to the internal carotid arteries (ICA) and surrounding structures (cavernous sinus, optic nerve, and brain stem)7 during transsphenoidal surgery is due to errors in determining the correct location and direction within the operative field.8 Navigation within the operational field during surgery in this region is difficult because of the variations in the structure of the sphenoid and a paucity of local anatomical landmarks.9 No standard method
has been established for positioning the patient’s head during surgery. The angle of operation is determined mainly on the basis of the surgeon’s clinical experience. In order to determine the optimal direction for approaching sellar tumors, we analyzed the cranial MRI anatomic data of the sellar region in 238 healthy Chinese adults and 75 Chinese adults with pituitary adenoma. The most commonly used anatomic markers on the cranial surface; the glabella, the external occipital tubercle, and the nasal columella, which can be easily located and accurately determined, and undergo little variation during surgery, were used to calculate the transsphenoidal angle and depth, to determine the appropriate head position and therefore, the optimal direction of the transsphenoidal approach. 2. Clinical data and methods 2.1. Clinical data
⇑ Corresponding author. Tel.: +86 2181885373.
E-mail address: [email protected] (Y. Lu). Chunlin Wang and Yuan Pan contributed equally to this work.
0967-5868/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2010.04.039
A control cohort of 238 healthy adults (131 males and 107 females, with an average age of 50.6 years (range: 18–80 years)
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C. Wang et al. / Journal of Clinical Neuroscience 17 (2010) 1523–1526
Fig. 1. Sagittal T1-weighted MRI showing points of anatomic measurement relevant to the transsphenoidal approach: (a) approach depth (represented by line C–D), and angle AOC (between the direction of the transsphenoidal approach (C–D) and the glabella–external occipital tubercle reference line (line A–B) (A = glabella, B = external occipital tubercle, C = midpoint of the nasal columella, D = sellar floor, O = intersection point of line C–D and line A–B)); (b) and (c) coronal T2-weighted MRI passing through the midpoint between the anterior (b) and posterior (c) clinoid processes showing the distance between the internal carotid arteries (ICA) at the cavernous segment. E–F is the distance between medial walls of the ICA cavernous segment.
was selected from those who had undergone physical examination in our hospital between 2005 and 2009. The patient group with sellar tumors comprised 75 patients (36 males, 39 females) with an average age of 40.2 years (range: 18–74 years) selected from patients with pituitary tumors who had visited the hospital during the same period. The following selection criteria were used for the two groups: (i) Chinese adults aged between 18 and 80 years of age; (ii) volunteers in the control group who had neither a history of craniocerebral disease nor craniocerebral space-occupying lesion on the MRI; (iii) patients with pituitary adenoma who had undergone brain MRI with contrast enhancement and had the diagnosis confirmed by histopathology after tumor removal. Patients were excluded from the study if: (i) the pituitary tumor was recurrent; and (ii) the pituitary tumor was associated with other intracranial tumors. 2.2. Method Both the patients and volunteers underwent brain MRI (GE 1.5 T Signa HD; GE Healthcare, Waukesha, WI, USA) with contrast enhancement. The T1-weighted mid-sagittal plane and T2weighted coronal plane in the midpoint of the anterior clinoid process and the posterior clinoid process were selected (Fig. 1), and measured with the software Centricity DICOM Viewer (GE Medical Systems). Anatomic landmarks on the cranial surface, including the glabella, the external occipital tubercle,10 and the nasal columella,11 were marked on the MRI. The approach direction was defined as the line linking the midpoint of the nasal columella and the floor of the sella. Measurements included: (i) the angle between the direction of the transsphenoidal approach and the line linking the glabella–external occipital tubercle; (ii) approach depth; and (iii) distance between the medial walls of the ICA at the cavernous segment.12
Table 1 Measurements from MRI of patients with sellar pituitary adenoma and a healthy control group (mean ± standard deviation) Measurement
Tumor group
Control group
t-value p value
AOC (°) 40.51 ± 2.98 41.18 ± 3.35 1.553 86.01 ± 4.99 85.34 ± 4.95 1.011 Distance between the nasal columella and sellar floor (mm) Distance between the internal 22.68 ± 5.03 15.89 ± 3.11 14.013 carotid arteries (mm)
0.121 0.313
0.000
AOC = angle between the direction of the transsphenoidal approach and the reference line linking the glabella and the external occipital tubercle.
3. Results 3.1. Angle between the direction of the transsphenoidal approach and the line linking the glabella–external occipital tubercle The average angle between the direction of the transsphenoidal approach and the line linking the glabella–external occipital tubercle in the sellar tumor group was 40.51o ± 2.98o (range: 34.2–46.9o) and in the healthy control group was 41.18o ± 3.35o (range: 32.6–47.6o), which were not significantly different (Table 1). 3.2. Distance between the nasal columella and sellar floor There was no significant difference in average distance between the nasal columella and the sellar floor between the sellar tumor group (86.01 ± 4.99 mm, range: 75.12–96.67 mm) and the healthy control group (85.34 ± 4.95 mm, range: 70.37–95.12 mm) (Table 1).
2.3. Statistical analyses 3.3. The distance between the ICA at the cavernous segment All analyses were carried out using the Statistical Package for the Social Sciences version 10.0 (SPSS; Chicago, IL, USA). Data are expressed as the mean ± standard deviation (SD) for continuous variables. Comparisons of variables between the two groups were performed using the Student t-test. All tests are two-sided. A p value less than 0.05 was considered statistically significant (p < 0.05).
The average distance between the ICA at the cavernous segment in patients with sellar tumors was 22.68 ± 5.03 mm (range: 13.78–34.22 mm), greater than in the healthy control group (15.89 ± 3.11 mm; range: 8.46–24.81 mm) (p < 0.01) (Table 1).
C. Wang et al. / Journal of Clinical Neuroscience 17 (2010) 1523–1526
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Fig. 2. Preoperative placement of the patient’s head for pituitary tumor resection via the transsphenoidal approach using our measurements showing: (a) location of the glabella (A) and the external occipital tubercle (B) on the cranial surface, with the A–B reference line perpendicular to the horizontal plane; (b) tilting the head backward to make the transsphenoidal direction (C–D) vertical; and (c) if a semi-sitting posture is used, the patient’s head can be positioned at a more appropriate angle, depending on the surgeon’s experience. A = glabella, B = external occipital tubercle, C = midpoint of the nasal columella, D = sellar floor, line G–H is the horizontal, O = intersection point of line C–D and line A–B.
4. Discussion Only a small operative field, normally about 1.5 cm 1.0 cm, can be visualized during pituitary tumor resection via the transsphenoidal approach, with the sella turcica surrounded by important structures including the cavernous sinus, optic nerve, and ICA. Therefore, precise positioning of the head is necessary. The direction of the approach needs to be carefully maintained, avoiding deviation. The upper boundary of the window that is opened in the floor of the sella in the sphenoid sinus is at the same level as the crypt of the tuberculum sella, and the lateral boundary of this window is the ICA. A neuronavigation system is useful for precise localization;13 and is used in many complicated cases, especially in recurrent pituitary adenoma.14 In this study, however, we selected widely used anatomic landmarks on the cranial surface to help determine an optimal surgical approach – the glabella, the external occipital tubercle, and the nasal columella. These landmarks were easily and accurately identified and show little interindividual variation. Currently, the nasal transsphenoidal approach is most commonly used for resection of sellar lesions. The optimal surgical approach must provide excellent exposure of the lesion. However, horizontal deflection of the approach may damage the ICA, leading to uncontrolled bleeding, and anterior deviation could damage the sphenoid bone platform of the anterior cranial fossa, causing cerebrospinal fluid rhinorrhea. Backward deflection could injure the brain stem. Surgeons use a number of different operative postures while performing a sellar tumor resection via the nasal transsphenoidal approach. Some surgeons prefer Cushing’s classical method,15 in which the patient is in a supine posture and the surgeon stands behind the patient’s head. Others prefer Guiot or Hardy’s semi-sitting posture.15–17 In the latter operative posture, the head position can be widely adjusted between parallel to, and perpendicular to, the horizontal. Venous drainage should also be considered. The ideal head posture should make the angle of the head, with backward or forward declination, correspond to the angle of the surgical approach as much as possible. However, it is difficult to directly verify the optimal approach direction because of the deep location of sellar lesions. Thus, we used an indirect method of observation in this study. We used the easily identified and measured line linking the glabella and the external occipital tubercle as the reference line, and then measured the angle between it and the direction of the surgi-
cal approach (Fig. 1a). We found that the average angle in 238 healthy Chinese adults was 41.18o, which was not significantly different to that found in 78 patients with pituitary tumors, and variation in the angles was negligible. By first adjusting the preoperative position of the patient’s head, we made the reference line perpendicular to the horizontal plane (Fig. 2a) and then tilted the head backwards using the above-mentioned angle so that the floor of the sella can be reached directly after placing a speculum through a single nostril (Fig. 2b). If the surgeon is accustomed to placing the speculum in the horizontal plane, they can also adjust the angle according to the above-mentioned method (Fig. 2c). For less-experienced surgeons, the nasal transsphenoidal approach may be complicated by deviation from the ideal approach. Although this deviation can be corrected using intraoperative Xray localization, it may increase the risk of bleeding, nerve and vessel damage, and significantly prolong the operating time. Therefore, reaching the lesion site directly is critical. Then the floor of the sella, at an average approach depth of 85 mm, will be reached, allowing the tumor to be resected by extending the bone window, depending on the extent of tumor growth and invasion.18 Because of the anatomical variations in the sphenoid sinus and its adjacent structures,19 the angle and depth of the transsphenoidal approach must be based on the patient’s preoperative MRI. Then, combined with the surgical markers on the body surface we have described, the surgeon can accurately determine the approach direction without adjusting the speculum repeatedly during the operation. This helps reduce mucosal peeling and damage, nasal injury and bleeding, postoperative nasal mucosal necrosis and the incidence of nasal septum perforation. When the speculum is positioned correctly, the anterior wall of the sphenoid sinus and the bone window at the sella base are large enough to maximize direct viewing with the operating microscope, which assists tumor resection,20,21 ensures smooth surgery, and reduces surgical complications. The ICA at the cavernous segment must be given special consideration when using the nasal transsphenoidal approach.22–24 Inaccurate positioning during surgery can injure the ICA and cavernous sinuses and cause bleeding, a lethal complication. According to Bergland et al.,25 the average distance between the ICAs is 14 mm, with a maximum distance of 23 mm. We found that the average distance between the ICAs at the midpoint of the anterior and posterior clinoid processes in the sellar tumor group was 22.68 mm, significantly greater than that in the healthy control
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group (15.89 mm). The tumor may extrude, wrap, or even invade the ICAs, thereby changing the direction and distance between the arteries, which can affect the identification of structures surrounding the tumor, and increase the risk of damage to the ICA. Therefore, the surgical field should not be more than 1 cm from the midline in the nasal transsphenoidal approach. The measurements in this study represent the cranial characteristics of East Asian populations. There are no equivalent data for European, North American, or African populations, which might vary from the population in this study. However, this technique of locating the lesion using surface markers to accurately determine the head position should be able to be applied to different human populations after appropriate measurements are made. References 1. Kerr C. Endonasal surgery for pituitary tumours replaces 40-year standard. Lancet Oncol 2003;4:135. 2. Maira G, Anile C, Albanese A, et al. The role of transsphenoidal surgery in the treatment of craniopharyngiomas. J Neurosurg 2004;100:445–51. 3. Wang Q, Lu XJ, Li B, et al. Extended endoscopic endonasal transsphenoidal removal of tuberculum sellae meningiomas: a preliminary report. J Clin Neurosci 2009;16:889–93. 4. Cook SW, Smith Z, Kelly DF. Endonasal transsphenoidal removal of tuberculum sellae meningiomas: technical note. Neurosurgery 2004;55:239–44 [comments 244–6]. 5. Jho HD, Alfieri A. Endoscopic endonasal pituitary surgery: evolution of surgical technique and equipment in 150 operations. Minim Invasive Neurosurg 2001;44:1–12. 6. Jho HD, Carrau RL, McLaughlin MR, et al. Endoscopic transsphenoidal resection of a large chordoma in the posterior fossa. Acta Neurochir (Wien) 1997;139: 343–7 [discussion 347–8]. 7. Mazumdar A. Imaging of the pituitary and sella turcica. Expert Rev Anticancer Ther 2006;6(Suppl. 9):S15–22. 8. Kocer N, Kizilkilic O, Albayram S, et al. Treatment of iatrogenic internal carotid artery laceration and carotid cavernous fistula with endovascular stent-graft placement. AJNR Am J Neuroradiol 2002;23:442–6. 9. Rodziewicz GS, Kelley RT, Kellman RM, et al. Transnasal endoscopic surgery of the pituitary gland: technical note. Neurosurgery 1996;39:189–92 [discussion 192–3].
10. Cotton F, Rozzi FR, Vallee B, et al. Cranial sutures and craniometric points detected on MRI. Surg Radiol Anat 2005;27:64–70. 11. Jacob S, Zelano B, Gungor A, et al. Location and gross morphology of the nasopalatine duct in human adults. Arch Otolaryngol Head Neck Surg 2000;126:741–8. 12. Hamid O, El Fiky L, Hassan O, et al. Anatomic variations of the sphenoid sinus and their impact on trans-sphenoid pituitary surgery. Skull Base 2008;18:9–15. 13. Hardy J. Neuronavigation in pituitary surgery. Surg Neurol 1999;52:648–9. 14. Zhao Y, Yu S, Wang R, et al. Clinical application of a neuronavigation system in transsphenoidal surgery of pituitary macroadenoma. Neurosurg Rev 2006;29: 306–12. 15. Fahlbusch R, Buchfelder M. The transsphenoidal approach to invasive sellar and clival lesions. In: Sekhar LN, Janecka IP, editors. Surgery of cranial base tumors. New York: Raven Press; 1993. p. 337–49. 16. Tindall GT, Woodard EJ, Barrow DL. Transsphenoidal excision of macroadenomas of the pituitary gland. In: Rengachary SS, Wilkins RH, editors. Neurosurgical operative atlas, Vol. 1. IL, USA: American Association of Neurological Surgeons; 1991. p. 287–98. 17. Jho HD, Carrau RL, Ko Y. Endoscopic pituitary surgery. In: Rengachary SS, Wilkins RH, editors. Neurosurgical operative atlas, Vol. 5. IL, USA: American Association of Neurological Surgeons; 1996. p. 1–12. 18. Kitano M, Taneda M. Extended transsphenoidal approach with submucosal posterior ethmoidectomy for parasellar tumors. Technical note. J Neurosurg 2001;94:999–1004. 19. Unal B, Bademci G, Bilgili YK, et al. Risky anatomic variations of sphenoid sinus for surgery. Surg Radiol Anat 2006;28:195–201. 20. Charalampaki P, Ayyad A, Kockro RA, et al. Surgical complications after endoscopic transsphenoidal pituitary surgery. J Clin Neurosci 2009;16:786–9. 21. Zhang X, Fei Z, Zhang W, et al. Endoscopic endonasal transsphenoidal surgery for invasive pituitary adenoma. J Clin Neurosci 2008;15:241–5. 22. Couldwell WT, Weiss MH, Rabb C, et al. Variations on the standard transsphenoidal approach to the sellar region, with emphasis on the extended approaches and parasellar approaches: surgical experience in 105 cases. Neurosurgery 2004;55:539–47 [discussion 547–50]. 23. Dusick JR, Esposito F, Malkasian D, et al. Avoidance of carotid artery injuries in transsphenoidal surgery with the Doppler probe and micro-hook blades. Neurosurgery 2007;60:322–8 [discussion 328–9]. 24. Kassam A, Snyderman CH, Mintz A, et al. Expanded endonasal approach: the rostrocaudal axis. Part I. Crista galli to the sella turcica. Neurosurg Focus 2005;19:E3. 25. Bergland RM, Ray BS, Torack RM. Anatomical variations in the pituitary gland and adjacent structures in 225 human autopsy cases. J Neurosurg 1968;28: 93–9.
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Clinical Study
Clinical significance of MRI-aided measurements in the transsphenoidal approach in Chinese adults Chunlin Wang , Yuan Pan , Yicheng Lu ⇑, Xuehua Ding Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai 200003, China
a r t i c l e
i n f o
Article history: Received 28 October 2009 Accepted 15 April 2010
Keywords: Anatomical imaging MRI Transsphenoidal approach
a b s t r a c t To determine the optimal direction for approaching sellar tumors, we developed an anatomical model of the most common approach, the transsphenoidal approach, in Chinese adults by analyzing MRI-aided measurements. Craniocerebral MRI of 75 Chinese adults with pituitary tumors and 238 healthy Chinese adults were obtained to analyse the angle between the direction of the transsphenoidal approach and the reference line linking the glabella and the external occipital tubercle, the approach depth, and the distance between the internal carotid arteries (ICA) at the cavernous sinuses segment. The mean angle (± standard deviation [SD]) between the direction of the transsphenoidal approach and the reference line in patients with sellar tumors was 40.51 ± 2.98°, similar to the angle in the healthy control group (41.18 ± 3.35°) (p > 0.05). The mean depth (± SD) calculated via the transsphenoidal approach in the sellar tumor group was 86.01 ± 4.99 mm, which was similar to the control group (85.34 ± 4.96 mm) (p > 0.05). However, the mean distance (± SD) between the bilateral ICA at the cavernous sinuses in the patients with sellar tumors was 22.68 ± 5.03 mm, greater than in the control group (15.89 ± 3.11 mm) (p < 0.01). Thus, during sellar tumor resection via the transsphenoidal approach, the patient’s head should be first positioned to allow the line linking the glabella and the external occipital tubercle to be perpendicular to the horizontal plane, and then inclined backwards at an angle of about 40°. The floor of the sella, at a depth of about 85 mm, can then be reached vertically by introducing a speculum via a single nostril. The operative field should be limited to about 1 cm from the midline. By adopting this method, the optimal angle and depth of the transsphenoidal approach can be determined without complicated equipment. Moreover, this technique is simple and accurate enough to maintain the correct approach, locate the lesion, and reduce the incidence of serious postoperative complications, including bleeding caused by rupture of the ICA. Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction The transsphenoidal approach is the most commonly used for pituitary tumor resection.1 This approach is also used for the resection of craniopharyngiomas, tuberculum sellae meningiomas, and notochordomas.2–6 Although the safety of such surgical procedures has improved with advances in operative technique, such procedures are still associated with severe life-threatening complications, including massive hemorrhage. The risk of fatal injury to the internal carotid arteries (ICA) and surrounding structures (cavernous sinus, optic nerve, and brain stem)7 during transsphenoidal surgery is due to errors in determining the correct location and direction within the operative field.8 Navigation within the operational field during surgery in this region is difficult because of the variations in the structure of the sphenoid and a paucity of local anatomical landmarks.9 No standard method
has been established for positioning the patient’s head during surgery. The angle of operation is determined mainly on the basis of the surgeon’s clinical experience. In order to determine the optimal direction for approaching sellar tumors, we analyzed the cranial MRI anatomic data of the sellar region in 238 healthy Chinese adults and 75 Chinese adults with pituitary adenoma. The most commonly used anatomic markers on the cranial surface; the glabella, the external occipital tubercle, and the nasal columella, which can be easily located and accurately determined, and undergo little variation during surgery, were used to calculate the transsphenoidal angle and depth, to determine the appropriate head position and therefore, the optimal direction of the transsphenoidal approach. 2. Clinical data and methods 2.1. Clinical data
⇑ Corresponding author. Tel.: +86 2181885373.
E-mail address: [email protected] (Y. Lu). Chunlin Wang and Yuan Pan contributed equally to this work.
0967-5868/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2010.04.039
A control cohort of 238 healthy adults (131 males and 107 females, with an average age of 50.6 years (range: 18–80 years)
1524
C. Wang et al. / Journal of Clinical Neuroscience 17 (2010) 1523–1526
Fig. 1. Sagittal T1-weighted MRI showing points of anatomic measurement relevant to the transsphenoidal approach: (a) approach depth (represented by line C–D), and angle AOC (between the direction of the transsphenoidal approach (C–D) and the glabella–external occipital tubercle reference line (line A–B) (A = glabella, B = external occipital tubercle, C = midpoint of the nasal columella, D = sellar floor, O = intersection point of line C–D and line A–B)); (b) and (c) coronal T2-weighted MRI passing through the midpoint between the anterior (b) and posterior (c) clinoid processes showing the distance between the internal carotid arteries (ICA) at the cavernous segment. E–F is the distance between medial walls of the ICA cavernous segment.
was selected from those who had undergone physical examination in our hospital between 2005 and 2009. The patient group with sellar tumors comprised 75 patients (36 males, 39 females) with an average age of 40.2 years (range: 18–74 years) selected from patients with pituitary tumors who had visited the hospital during the same period. The following selection criteria were used for the two groups: (i) Chinese adults aged between 18 and 80 years of age; (ii) volunteers in the control group who had neither a history of craniocerebral disease nor craniocerebral space-occupying lesion on the MRI; (iii) patients with pituitary adenoma who had undergone brain MRI with contrast enhancement and had the diagnosis confirmed by histopathology after tumor removal. Patients were excluded from the study if: (i) the pituitary tumor was recurrent; and (ii) the pituitary tumor was associated with other intracranial tumors. 2.2. Method Both the patients and volunteers underwent brain MRI (GE 1.5 T Signa HD; GE Healthcare, Waukesha, WI, USA) with contrast enhancement. The T1-weighted mid-sagittal plane and T2weighted coronal plane in the midpoint of the anterior clinoid process and the posterior clinoid process were selected (Fig. 1), and measured with the software Centricity DICOM Viewer (GE Medical Systems). Anatomic landmarks on the cranial surface, including the glabella, the external occipital tubercle,10 and the nasal columella,11 were marked on the MRI. The approach direction was defined as the line linking the midpoint of the nasal columella and the floor of the sella. Measurements included: (i) the angle between the direction of the transsphenoidal approach and the line linking the glabella–external occipital tubercle; (ii) approach depth; and (iii) distance between the medial walls of the ICA at the cavernous segment.12
Table 1 Measurements from MRI of patients with sellar pituitary adenoma and a healthy control group (mean ± standard deviation) Measurement
Tumor group
Control group
t-value p value
AOC (°) 40.51 ± 2.98 41.18 ± 3.35 1.553 86.01 ± 4.99 85.34 ± 4.95 1.011 Distance between the nasal columella and sellar floor (mm) Distance between the internal 22.68 ± 5.03 15.89 ± 3.11 14.013 carotid arteries (mm)
0.121 0.313
0.000
AOC = angle between the direction of the transsphenoidal approach and the reference line linking the glabella and the external occipital tubercle.
3. Results 3.1. Angle between the direction of the transsphenoidal approach and the line linking the glabella–external occipital tubercle The average angle between the direction of the transsphenoidal approach and the line linking the glabella–external occipital tubercle in the sellar tumor group was 40.51o ± 2.98o (range: 34.2–46.9o) and in the healthy control group was 41.18o ± 3.35o (range: 32.6–47.6o), which were not significantly different (Table 1). 3.2. Distance between the nasal columella and sellar floor There was no significant difference in average distance between the nasal columella and the sellar floor between the sellar tumor group (86.01 ± 4.99 mm, range: 75.12–96.67 mm) and the healthy control group (85.34 ± 4.95 mm, range: 70.37–95.12 mm) (Table 1).
2.3. Statistical analyses 3.3. The distance between the ICA at the cavernous segment All analyses were carried out using the Statistical Package for the Social Sciences version 10.0 (SPSS; Chicago, IL, USA). Data are expressed as the mean ± standard deviation (SD) for continuous variables. Comparisons of variables between the two groups were performed using the Student t-test. All tests are two-sided. A p value less than 0.05 was considered statistically significant (p < 0.05).
The average distance between the ICA at the cavernous segment in patients with sellar tumors was 22.68 ± 5.03 mm (range: 13.78–34.22 mm), greater than in the healthy control group (15.89 ± 3.11 mm; range: 8.46–24.81 mm) (p < 0.01) (Table 1).
C. Wang et al. / Journal of Clinical Neuroscience 17 (2010) 1523–1526
1525
Fig. 2. Preoperative placement of the patient’s head for pituitary tumor resection via the transsphenoidal approach using our measurements showing: (a) location of the glabella (A) and the external occipital tubercle (B) on the cranial surface, with the A–B reference line perpendicular to the horizontal plane; (b) tilting the head backward to make the transsphenoidal direction (C–D) vertical; and (c) if a semi-sitting posture is used, the patient’s head can be positioned at a more appropriate angle, depending on the surgeon’s experience. A = glabella, B = external occipital tubercle, C = midpoint of the nasal columella, D = sellar floor, line G–H is the horizontal, O = intersection point of line C–D and line A–B.
4. Discussion Only a small operative field, normally about 1.5 cm 1.0 cm, can be visualized during pituitary tumor resection via the transsphenoidal approach, with the sella turcica surrounded by important structures including the cavernous sinus, optic nerve, and ICA. Therefore, precise positioning of the head is necessary. The direction of the approach needs to be carefully maintained, avoiding deviation. The upper boundary of the window that is opened in the floor of the sella in the sphenoid sinus is at the same level as the crypt of the tuberculum sella, and the lateral boundary of this window is the ICA. A neuronavigation system is useful for precise localization;13 and is used in many complicated cases, especially in recurrent pituitary adenoma.14 In this study, however, we selected widely used anatomic landmarks on the cranial surface to help determine an optimal surgical approach – the glabella, the external occipital tubercle, and the nasal columella. These landmarks were easily and accurately identified and show little interindividual variation. Currently, the nasal transsphenoidal approach is most commonly used for resection of sellar lesions. The optimal surgical approach must provide excellent exposure of the lesion. However, horizontal deflection of the approach may damage the ICA, leading to uncontrolled bleeding, and anterior deviation could damage the sphenoid bone platform of the anterior cranial fossa, causing cerebrospinal fluid rhinorrhea. Backward deflection could injure the brain stem. Surgeons use a number of different operative postures while performing a sellar tumor resection via the nasal transsphenoidal approach. Some surgeons prefer Cushing’s classical method,15 in which the patient is in a supine posture and the surgeon stands behind the patient’s head. Others prefer Guiot or Hardy’s semi-sitting posture.15–17 In the latter operative posture, the head position can be widely adjusted between parallel to, and perpendicular to, the horizontal. Venous drainage should also be considered. The ideal head posture should make the angle of the head, with backward or forward declination, correspond to the angle of the surgical approach as much as possible. However, it is difficult to directly verify the optimal approach direction because of the deep location of sellar lesions. Thus, we used an indirect method of observation in this study. We used the easily identified and measured line linking the glabella and the external occipital tubercle as the reference line, and then measured the angle between it and the direction of the surgi-
cal approach (Fig. 1a). We found that the average angle in 238 healthy Chinese adults was 41.18o, which was not significantly different to that found in 78 patients with pituitary tumors, and variation in the angles was negligible. By first adjusting the preoperative position of the patient’s head, we made the reference line perpendicular to the horizontal plane (Fig. 2a) and then tilted the head backwards using the above-mentioned angle so that the floor of the sella can be reached directly after placing a speculum through a single nostril (Fig. 2b). If the surgeon is accustomed to placing the speculum in the horizontal plane, they can also adjust the angle according to the above-mentioned method (Fig. 2c). For less-experienced surgeons, the nasal transsphenoidal approach may be complicated by deviation from the ideal approach. Although this deviation can be corrected using intraoperative Xray localization, it may increase the risk of bleeding, nerve and vessel damage, and significantly prolong the operating time. Therefore, reaching the lesion site directly is critical. Then the floor of the sella, at an average approach depth of 85 mm, will be reached, allowing the tumor to be resected by extending the bone window, depending on the extent of tumor growth and invasion.18 Because of the anatomical variations in the sphenoid sinus and its adjacent structures,19 the angle and depth of the transsphenoidal approach must be based on the patient’s preoperative MRI. Then, combined with the surgical markers on the body surface we have described, the surgeon can accurately determine the approach direction without adjusting the speculum repeatedly during the operation. This helps reduce mucosal peeling and damage, nasal injury and bleeding, postoperative nasal mucosal necrosis and the incidence of nasal septum perforation. When the speculum is positioned correctly, the anterior wall of the sphenoid sinus and the bone window at the sella base are large enough to maximize direct viewing with the operating microscope, which assists tumor resection,20,21 ensures smooth surgery, and reduces surgical complications. The ICA at the cavernous segment must be given special consideration when using the nasal transsphenoidal approach.22–24 Inaccurate positioning during surgery can injure the ICA and cavernous sinuses and cause bleeding, a lethal complication. According to Bergland et al.,25 the average distance between the ICAs is 14 mm, with a maximum distance of 23 mm. We found that the average distance between the ICAs at the midpoint of the anterior and posterior clinoid processes in the sellar tumor group was 22.68 mm, significantly greater than that in the healthy control
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group (15.89 mm). The tumor may extrude, wrap, or even invade the ICAs, thereby changing the direction and distance between the arteries, which can affect the identification of structures surrounding the tumor, and increase the risk of damage to the ICA. Therefore, the surgical field should not be more than 1 cm from the midline in the nasal transsphenoidal approach. The measurements in this study represent the cranial characteristics of East Asian populations. There are no equivalent data for European, North American, or African populations, which might vary from the population in this study. However, this technique of locating the lesion using surface markers to accurately determine the head position should be able to be applied to different human populations after appropriate measurements are made. References 1. Kerr C. Endonasal surgery for pituitary tumours replaces 40-year standard. Lancet Oncol 2003;4:135. 2. Maira G, Anile C, Albanese A, et al. The role of transsphenoidal surgery in the treatment of craniopharyngiomas. J Neurosurg 2004;100:445–51. 3. Wang Q, Lu XJ, Li B, et al. Extended endoscopic endonasal transsphenoidal removal of tuberculum sellae meningiomas: a preliminary report. J Clin Neurosci 2009;16:889–93. 4. Cook SW, Smith Z, Kelly DF. Endonasal transsphenoidal removal of tuberculum sellae meningiomas: technical note. Neurosurgery 2004;55:239–44 [comments 244–6]. 5. Jho HD, Alfieri A. Endoscopic endonasal pituitary surgery: evolution of surgical technique and equipment in 150 operations. Minim Invasive Neurosurg 2001;44:1–12. 6. Jho HD, Carrau RL, McLaughlin MR, et al. Endoscopic transsphenoidal resection of a large chordoma in the posterior fossa. Acta Neurochir (Wien) 1997;139: 343–7 [discussion 347–8]. 7. Mazumdar A. Imaging of the pituitary and sella turcica. Expert Rev Anticancer Ther 2006;6(Suppl. 9):S15–22. 8. Kocer N, Kizilkilic O, Albayram S, et al. Treatment of iatrogenic internal carotid artery laceration and carotid cavernous fistula with endovascular stent-graft placement. AJNR Am J Neuroradiol 2002;23:442–6. 9. Rodziewicz GS, Kelley RT, Kellman RM, et al. Transnasal endoscopic surgery of the pituitary gland: technical note. Neurosurgery 1996;39:189–92 [discussion 192–3].
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