Peer-Review Reports
Endoscopic Approaches to the Craniovertebral Junction and Odontoid Process Chandrashekhar E. Deopujari1, Vikram S. Karmarkar1, Nishit J. Shah2
Key words Dens - Endonasal - Extended skull base approach - Odontoid process - Skull base reconstruction - Ventral cervicomedullary compression -
Abbreviations and Acronyms CV: Craniovertebral HB: Hadad-Bassagasteguy From the Departments of 1Neurosurgery and 2 Otorhinolaryngology, Bombay Hospital Institute of Medical Sciences, Mumbai, India To whom correspondence should be addressed: Chandrashekhar E. Deopujari, M.Ch., M.Sc. [E-mail: [email protected]] Citation: World Neurosurg. (2014) 82, 6S:S49-S53. http://dx.doi.org/10.1016/j.wneu.2014.07.025 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.
- BACKGROUND:
The microsurgical transoral approach has traditionally been the preferred access for ventral decompression of the craniovertebral junction. This natural corridor, although direct, may be a challenging approach because of potential morbidities. The evolution of endoscopic methods in skull base surgeries has reduced morbidity and improved results. Endoscopic approaches are also being used for ventral decompression at the craniovertebral junction. Some technical modifications in this approach are described.
- METHODS:
An endoscope is inserted endonasally for a panoramic view of the entire area of interest, from the sphenoid to second cervical vertebra. Image guidance systems are used in all cases to guide the resection. The soft palate is retracted away with a rubber catheter sling when both nasal and oral corridors are being used. Various mucosal flaps are raised for access and reconstruction. Actual decompression can be done through the nasal or oral corridors based on the relationship of the pathology to the palate. Reconstruction is done using standard principles with the vascularized flaps, fat, and fibrin glue.
- RESULTS:
Reduced surgical morbidity by avoiding palatal split and good postoperative healing are some of the advantages of this modified endoscopic technique. Better surgical exposure and a wide perspective facilitate the decompression. However, as with all newer perspectives, a learning curve exists.
INTRODUCTION
- CONCLUSIONS:
The craniovertebral (CV) junction is a complex anatomic structure at the skull base enclosing the cervicomedullary structures. Various algorithms for surgical management of cervicomedullary compression are well established. The “gold standard” for surgical treatment of ventral compression at the CV junction has been the transoral approach. Over the years, some authors have advocated the use of endoscopy to reach pathologies at the CV junction (2, 6, 15); cadaveric anatomic studies have been done to establish the feasibility of this approach (1, 3, 10-12). Emerging acceptance of the endoscope for accessing cranial base pathology through an endonasal sphenoid sinus portal has led to contemplation of access to the CV junction through the same route. A better understanding of the pathologic anatomy of midline skull base lesions is essential to the success of these techniques. Closer collaboration between rhinologists and neurosurgeons has resulted in better appreciation of nasal and paranasal sinus and skull base anatomy
from the inferior perspective; this has helped in finding new corridors and extending older ones for better surgical results. Techniques such as the development of mucosal flaps have stimulated reconstruction of skull base defects adding safety to these procedures. In the last 15 years, our group has performed >500 endonasal endoscopic procedures for pituitary tumours and other midline skull base lesions. Extended approaches were used after >200 pituitary surgeries. Although endoscopic CV junction surgery is being done at a few centers around the globe for various pathologies (4-9, 13, 14), we discuss some of our technical modifications of this approach with emphasis on exposure, decompression methods, and reconstruction. The basic concept is to have a 2-nostril, 2-surgeon technique.
Used judiciously, this modified endoscopic approach to the craniovertebral junction and odontoid process is minimally invasive and adds to the surgeon’s armamentarium.
WORLD NEUROSURGERY 82 [6S]: S49-S53, DECEMBER 2014
MATERIALS AND METHODS While planning the endoscopic procedures for decompression, we have used the following “rule of thumb”: the patient’s lateral CV junction x-ray or sagittal computed tomography scan is studied. A line drawn in the plane of the hard palate and extending posteriorly gives an idea of how much pathology lies above the plane of the hard palate. This line differs from Chamberlain’s line in that the posterior end does not end at the posterior foramen magnum lip. When the junction of the dens and the body of the second cervical vertebra (C2) lies above this line, the endoscopic procedure can be done entirely through the nose. When part of the pathology lies above and below the plane, a combined endoscopic transnasal and transoral procedure can be done with visualization from the nose with
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PEER-REVIEW REPORTS CHANDRASHEKHAR E. DEOPUJARI ET AL.
the endoscope and the instruments going through the mouth. When the pathology lies completely below the level of the hard palate, one may use the standard transoral procedure or an endoscopic transoral procedure where the scope and the instruments go through the mouth. Preparation for the procedure involves standard instructions for nasal and mouth preparation. This preparation includes povidone-iodine mouth gargles before the induction of anesthesia. Tracheal intubation is always performed with the patient awake with fiberoptic scope assistance. The neurologic status is assessed after intubation, and anesthesia is induced. The patient’s head is fixed in a 3-pin skull clamp, and the image guidance system is registered and activated. We have used image guidance in all cases. Apart from giving orientation in a new perspective offered by the endoscope, it is vital to limit and tailor the extent of bone removal. A mouth gag was used to keep the mouth open to approach pathology through this corridor when required. A 0-degree endoscope is used for the procedure. A 45-degree endoscope is useful when exposure is limited. An angled drill handpiece is most useful to navigate the curve of the palate. A straight handpiece may also be used. If the angle makes it difficult to use through the nose, we use the drill through the mouth and visualize through the nose; this gives a wide field of vision and a superior ability to visualize the instrument ends. Nasal endoscopy is done, and the posterior nasal septum is removed. Removal
ENDOSCOPIC APPROACHES TO CV JUNCTION AND ODONTOID PROCESS
of the septum facilitates angulation and increases the space for maneuvering the scope and instruments during the procedure. Mini-Hadad-Bassagasteguy (HB) flaps on both sides extending only to the bone-cartilage junction are raised. The mini-HB flap has its vascular pedicle on the septal branch of the sphenopalatine artery similar to a standard HB flap, but it is not as wide as the standard HB flap, and only the inferior half of the septum is used. With flaps on both sides, only half the width is needed because it is doubled with the 2 flaps coming together. The sphenoid sinuses are opened wide after the flaps are raised to allow the flap to be “parked” in the sphenoid until it is needed for the reconstruction. To reconstruct the nasopharynx and defect over the first and second cervical vertebrae (C1eC2), one may use a HB flap with a reverse flap from the other side to cover the bare cartilage. If the sphenoid is involved or its floor needs to be drilled, the maxillary sinuses are opened posteriorly, and the flaps are tucked into the sinuses. After the flaps are raised and “parked,” the posterior septectomy can be done by removing the perpendicular plate of ethmoid and posterior vomer bone down to the floor of the nose to the choana. This inferior removal of bone improves visibility and allows better retraction of the uvula and soft palate anteriorly. A rubber catheter can be passed through the nostril and out the mouth to pull the palate anteriorly. When the nasal exposure is complete, the vertical extent of the pathology is
Figure 1. Image-guided navigation systems are used in all cases. They are employed to define the vertical limits of the nasopharyngeal flap based on the pathology. (A) Navigation system being used (through the nose) at the
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assessed; navigation is useful here (Figure 1). Based on the extent, a nasopharyngeal mucosal flap, based inferiorly, is raised. The nasopharyngeal flap starts just under the roof as an inverted “U” incision because the tissue over the adenoids may be friable, especially in pediatric patients. The incision extends to the muscle layer but not through it. The upper half of the incision is done by instrumentation through the nose, but as one gets lower, it is easier to raise this flap through the mouth. The lateral limits of the flap are medial to the eustachian tube openings. Lateral to these lie the parapharyngeal carotid artery. The attachments of the muscles are elevated off the clivus, anterior arch of C1, and dens. At this time, one also appreciates the additional “hands.” While the ear, nose, and throat surgeon holds the scope and provides vision and suction from above, the neurosurgeon can retract the flap with a forceps and incise with a cautery to raise and lower the flap to the required level. When the level is reached, the flap is allowed to stay in the oropharynx and can be weighed down so that it does not obstruct vision or instrumentation (Figure 2). Drilling the anterior arch of the atlas is done with various cutting and diamondtipped burrs. After the anterior arch is drilled out, the ligaments are cut; this is followed by drilling the odontoid process. As with the standard transoral procedure, the dens is hollowed out, and then the shell is excised after cutting its
beginning of the decompression to define the upper limit. (B) Lower limit for decompression being defined (through the mouth). (C) Navigation system being used to check the thickness of the dens after initially thinning it out.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.025
PEER-REVIEW REPORTS CHANDRASHEKHAR E. DEOPUJARI ET AL.
ENDOSCOPIC APPROACHES TO CV JUNCTION AND ODONTOID PROCESS
complete the C1eC2 closure and sutured with a 3-0 polyglactin suture. A nasogastric feeding tube is inserted under vision. The nasogastric tube is removed early in the postoperative period when the patient is able to swallow properly. Patients are electively ventilated for 24 hours and extubated after confirming neurologic function. RESULTS We have used the combined nasal and oral endoscopic approach described in this article for pathologies including fixed atlantoaxial dislocation and clivus chordomas. Of the patients with fixed atlantoaxial dislocation, 2 had a history of posterior decompression and fixation and continued to experience progressive symptoms secondary to ventral compression (Figures 3 and 4). Postoperative morbidity was reduced with endoscopic procedures. Because the palate is not split, the velopharyngeal reflex is not impaired significantly, which helps patients’ swallowing. Healing of the nasopharynx also takes place relatively unhindered. DISCUSSION
Figure 2. Operative procedure photos. (A) The limits of the inverted “U” nasopharyngeal mucosal flap are shown. The flap is limited laterally by the eustachian tube openings. The vertical extent can begin high in the nasopharynx. (B) After the flap is raised, the muscles are cut and elevated off the lower clivus, anterior arch of C1, and over C2. (C) The anterior arch of C1 is drilled out, and soft tissue and ligaments are excised to expose the odontoid process. (D) The odontoid is drilled out, first by thinning out the core and then excising the shell of bone. (E) After the decompression is complete, the dura mater is seen bulging through the decompression defect.
attachments. After the dens is drilled out, the tectorial membrane is incised. At the end of the decompression, the dura mater is seen bulging. Image guidance is used to ascertain the extent and completeness of the bony decompression. At this point, it is important to reconstruct the defect. In case of a large cerebrospinal fistula, such as may be discovered incidentally during odontoidectomy or after intradural pathology has been tackled (i.e., a clivus chordoma), the
repair needs to be more complete and secure and is in multiple layers. We usually use fascia lata as an internal closure layer with fat above. Fibrin glue is used to fix them in place. When there is no leak, the defect is filled only with fat and fixed with glue. The outer closure in either case is effected by the 2 mini-HB flaps and the nasopharyngeal flap. The 2 septal flaps are rotated to cover the clivus and roof of the nasopharynx area, whereas the inverted “U” nasopharynx flap is replaced to
WORLD NEUROSURGERY 82 [6S]: S49-S53, DECEMBER 2014
Retracting the soft palate anteriorly using a fine catheter passed through the nostril and taken out of the oral cavity to pull the palate forward aids in producing a panoramic view of the entire area from sphenoid to C2 using an endoscope. To clarify the issue of conflicting straight surgical instruments with the endoscope, we have found instrumentation through the oral cavity to be easier. Nasal endoscopy allows for vision and irrigation through the nose, whereas the neurosurgeon can perform the surgery through the open mouth. This approach gives the surgeon greater freedom of movement, avoiding conflict with the endoscope. Also, it is easier because the surgical instruments are in a straighter plane. A slight flexion of the neck makes it easier to access the nasopharynx from the nose, but too much flexion must be avoided because that would affect transoral instrumentation. To avoid anterior septal surgery and the associated morbidity with raising a formal full HB flap, we used a combination of flaps. The horizontal limb of the nasopharyngeal mucosal flap is
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ENDOSCOPIC APPROACHES TO CV JUNCTION AND ODONTOID PROCESS
Figure 3. A 10-year-old boy with congenital mobile atlantoaxial dislocation was operated on by posterior fusion at a younger age. The anterior compression continued to increase, and the child experienced progressive neurologic worsening. (A) Sagittal magnetic resonance imaging with anterior cervicomedullary compression with signal intensity changes. The patient underwent an endoscopic odontoidectomy successfully. (B) Sagittal computed tomography scan performed after the surgery shows adequate ventral decompression.
taken just below the roof, and vertical limbs are dropped on either side staying medial to the eustachian tubes. This modification prevents damage to the eustachian tubes and ensures against accidental injury to the internal carotid artery—except in the case of an aberrant internal carotid artery. We believe that the above-described simple modification in reconstruction can reduce some of the morbidity associated with a formal HB flap. The flaps are simpler to raise, there is no exposure of bone cartilage, the combined width of the 2 flaps may be wider,
suturing of the reverse flap is not required, and crusting and postoperative care for the nose are reduced. The flaps could be sutured to each other, but we prefer not to do that and instead allow it to fall flat on the fat, to avoid potential dead space between the flaps and fat. A Merocel (Medtronic Xomed Inc., Jacksonville, FL, USA) pack is kept for 3e4 days to maintain pressure and keep the flaps in position. Postoperative healing is good because there are almost no raw or exposed areas in the nose or nasopharynx. Traditional ventral surgical approaches to the craniocervical junction include the
transoral odontoidectomy using a microscope. Other approaches such as the high cervical retropharyngeal approaches are also described. Visualization of the surgical field largely depends on the depth at which the operative site is from the microscope or eye. With a microscope, one has a cylindrical/conical perspective. Although modern microscopes with their maneuverability can look at the edges of the field, vision may be compromised if there are barriers. Endoscopic vision differs because the depth from the operative site is very small, and corners can be looked at by angulating the scope or using angled scopes. The main disadvantage of the endoscope is the lack of depth perception. This lack of depth perception is usually overcome by moving the scope in and out; this is advantageous in ventral odontoidectomy where the barrier of the palate does not hinder vision. Based on the vertical extent of decompression necessary, traditional transoral procedures may require splitting the soft palate and may even necessitate splitting the hard palate. Both of these maneuvers are known to cause postoperative swallowing difficulties secondary to the disruption of the velopharyngeal mechanism. This additional step is not needed when using the endoscope. When the mouth is being used as a corridor, the soft palate is moved out of the way via a rubber catheter sling, through the nostril and out through the mouth. CONCLUSIONS Any surgical intervention at this complex anatomic site has to be a carefully considered decision based on one of the currently accepted algorithms. Endoscopic procedures have added an option to this decision-making algorithm. REFERENCES 1. Abuzayed B, Tanriover N, Ozlen F, Gazioglu N, Ulu MO, Kafadar AM, Eraslan B, Akar Z: Endoscopic endonasal transsphenoidal approach to the sellar region: results of endoscopic dissection on 30 cadavers. Turk Neurosurg 19:237-244, 2009.
Figure 4. A 56-year-old man presented with progressive spastic quadriparesis. Imaging revealed a fixed atlantoaxial dislocation with cervicomedullary compression seen more posteriorly. He was operated on elsewhere with a posterior fusion and fixation with a loop. His symptoms worsened a few years later. (A) Sagittal computed tomography cisternogram with predominant ventral cervicomedullary compression. The patient was operated on using the endoscopic techniques described in the present article. (B) Sagittal computed tomography image obtained after surgery. The patient experienced satisfactory neurologic improvement.
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2. Alfieri A, Jho H-D, Tschabitscher M: Endoscopic endonasal approach to the ventral craniocervical junction: anatomical study. Acta Neurochir (Wien) 144:219-225, 2002. 3. Baird CJ, Prevedello
Conway JE, Sciubba DM, DM, Quiñones-Hinojosa A,
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.025
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Kassam AB: Radiographic and anatomic basis of endoscopic anterior craniocervical decompression: a comparison of endonasal, transoral, and transcervical approaches. Neurosurgery 65:158-164, 2009. 4. Cornelius JF, Kania R, Bostelmann R, Herman P, George B: Transnasal endoscopic odontoidectomy after occipito-cervical fusion during the same operative setting—technical note. Neurosurg Rev 34:115-121, 2011. 5. Husain M, Rastogi M, Ojha BK, Chandra A, Jha DK: Endoscopic transoral surgery for craniovertebral junction anomalies. Technical note. J Neurosurg Spine 5:367-373, 2006. 6. Kassam AB, Snyderman C, Gardner P, Carrau R, Spiro R: The expanded endonasal approach: a fully endoscopic transnasal approach and resection of the odontoid process: technical case report. Neurosurgery 57 (1 Suppl):E213 [discussion E213], 2005.
ENDOSCOPIC APPROACHES TO CV JUNCTION AND ODONTOID PROCESS
Welch WC: Da Vinci Robot-assisted transoral odontoidectomy for basilar invagination. ORL J Otorhinolaryngol Relat Spec 72:91-95, 2010.
Endoscopic endonasal approach for clival chordomas. Neurosurgery 64:268-278, 2009.
9. Magrini S, Pasquini E, Mazzatenta D, Mascari C, Galassi E, Frank G: Endoscopic endonasal odontoidectomy in a patient affected by Down syndrome: technical case report. Neurosurgery 63: 373-374, 2008.
14. Wu JC, Huang WC, Cheng H, Liang ML, Ho CY, Wong TT, Shih YH, Yen YS: Endoscopic transnasal transclival odontoidectomy: a new approach to decompression: technical case report. Neurosurgery 63 (1 Suppl 1):ONSE92-ONSE94 [discussion ONSE94], 2008.
10. Messina A, Bruno MC, Decq P, Coste A, Cavallo LM, Divittis ED, Cappabianca P, Tschabitscher M: Pure endoscopic endonasal odontoidectomy: anatomical study. Neurosurg Rev 30:189-194, 2007.
15. Wolinsky JP, Sciubba DM, Suk I, Gokaslan ZL: Endoscopic image-guided odontoidectomy for decompression of basilar invagination via a standard anterior cervical approach. J Neurosurg Spine 6:84-191, 2007.
11. Pillai P, Baig MN, Karas CS, Ammirati M: Endoscopic image-guided transoral approach to the craniovertebral junction: an anatomic study comparing surgical exposure and surgical freedom obtained with the endoscope and the operating microscope. Neurosurgery 64:437-444, 2009.
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 18 September 2013; accepted 25 July 2014
7. Lee A, Sommer D, Reddy K, Murty N, Gunnarsson T: Endoscopic transnasal approach to the craniocervical junction. Skull Base 20:199-205, 2010.
12. Seker A, Inoue K, Osawa S, Akakin A, Kilic T, Rhoton AL Jr: Comparison of endoscopic transnasal and transoral approaches to the craniovertebral junction. World Neurosurg 74:583-602, 2010.
8. Lee JY, Lega B, Bhowmick D, Newman JG, O’Malley BW Jr, Weinstein GS, Grady MS,
13. Stippler M, Carrau RL,
Gardner PA, Snyderman Prevedello DM, Kassam
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CH, AB:
Citation: World Neurosurg. (2014) 82, 6S:S49-S53. http://dx.doi.org/10.1016/j.wneu.2014.07.025 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
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Endoscopic Approaches to the Craniovertebral Junction and Odontoid Process Chandrashekhar E. Deopujari1, Vikram S. Karmarkar1, Nishit J. Shah2
Key words Dens - Endonasal - Extended skull base approach - Odontoid process - Skull base reconstruction - Ventral cervicomedullary compression -
Abbreviations and Acronyms CV: Craniovertebral HB: Hadad-Bassagasteguy From the Departments of 1Neurosurgery and 2 Otorhinolaryngology, Bombay Hospital Institute of Medical Sciences, Mumbai, India To whom correspondence should be addressed: Chandrashekhar E. Deopujari, M.Ch., M.Sc. [E-mail: [email protected]] Citation: World Neurosurg. (2014) 82, 6S:S49-S53. http://dx.doi.org/10.1016/j.wneu.2014.07.025 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.
- BACKGROUND:
The microsurgical transoral approach has traditionally been the preferred access for ventral decompression of the craniovertebral junction. This natural corridor, although direct, may be a challenging approach because of potential morbidities. The evolution of endoscopic methods in skull base surgeries has reduced morbidity and improved results. Endoscopic approaches are also being used for ventral decompression at the craniovertebral junction. Some technical modifications in this approach are described.
- METHODS:
An endoscope is inserted endonasally for a panoramic view of the entire area of interest, from the sphenoid to second cervical vertebra. Image guidance systems are used in all cases to guide the resection. The soft palate is retracted away with a rubber catheter sling when both nasal and oral corridors are being used. Various mucosal flaps are raised for access and reconstruction. Actual decompression can be done through the nasal or oral corridors based on the relationship of the pathology to the palate. Reconstruction is done using standard principles with the vascularized flaps, fat, and fibrin glue.
- RESULTS:
Reduced surgical morbidity by avoiding palatal split and good postoperative healing are some of the advantages of this modified endoscopic technique. Better surgical exposure and a wide perspective facilitate the decompression. However, as with all newer perspectives, a learning curve exists.
INTRODUCTION
- CONCLUSIONS:
The craniovertebral (CV) junction is a complex anatomic structure at the skull base enclosing the cervicomedullary structures. Various algorithms for surgical management of cervicomedullary compression are well established. The “gold standard” for surgical treatment of ventral compression at the CV junction has been the transoral approach. Over the years, some authors have advocated the use of endoscopy to reach pathologies at the CV junction (2, 6, 15); cadaveric anatomic studies have been done to establish the feasibility of this approach (1, 3, 10-12). Emerging acceptance of the endoscope for accessing cranial base pathology through an endonasal sphenoid sinus portal has led to contemplation of access to the CV junction through the same route. A better understanding of the pathologic anatomy of midline skull base lesions is essential to the success of these techniques. Closer collaboration between rhinologists and neurosurgeons has resulted in better appreciation of nasal and paranasal sinus and skull base anatomy
from the inferior perspective; this has helped in finding new corridors and extending older ones for better surgical results. Techniques such as the development of mucosal flaps have stimulated reconstruction of skull base defects adding safety to these procedures. In the last 15 years, our group has performed >500 endonasal endoscopic procedures for pituitary tumours and other midline skull base lesions. Extended approaches were used after >200 pituitary surgeries. Although endoscopic CV junction surgery is being done at a few centers around the globe for various pathologies (4-9, 13, 14), we discuss some of our technical modifications of this approach with emphasis on exposure, decompression methods, and reconstruction. The basic concept is to have a 2-nostril, 2-surgeon technique.
Used judiciously, this modified endoscopic approach to the craniovertebral junction and odontoid process is minimally invasive and adds to the surgeon’s armamentarium.
WORLD NEUROSURGERY 82 [6S]: S49-S53, DECEMBER 2014
MATERIALS AND METHODS While planning the endoscopic procedures for decompression, we have used the following “rule of thumb”: the patient’s lateral CV junction x-ray or sagittal computed tomography scan is studied. A line drawn in the plane of the hard palate and extending posteriorly gives an idea of how much pathology lies above the plane of the hard palate. This line differs from Chamberlain’s line in that the posterior end does not end at the posterior foramen magnum lip. When the junction of the dens and the body of the second cervical vertebra (C2) lies above this line, the endoscopic procedure can be done entirely through the nose. When part of the pathology lies above and below the plane, a combined endoscopic transnasal and transoral procedure can be done with visualization from the nose with
www.WORLDNEUROSURGERY.org
S49
PEER-REVIEW REPORTS CHANDRASHEKHAR E. DEOPUJARI ET AL.
the endoscope and the instruments going through the mouth. When the pathology lies completely below the level of the hard palate, one may use the standard transoral procedure or an endoscopic transoral procedure where the scope and the instruments go through the mouth. Preparation for the procedure involves standard instructions for nasal and mouth preparation. This preparation includes povidone-iodine mouth gargles before the induction of anesthesia. Tracheal intubation is always performed with the patient awake with fiberoptic scope assistance. The neurologic status is assessed after intubation, and anesthesia is induced. The patient’s head is fixed in a 3-pin skull clamp, and the image guidance system is registered and activated. We have used image guidance in all cases. Apart from giving orientation in a new perspective offered by the endoscope, it is vital to limit and tailor the extent of bone removal. A mouth gag was used to keep the mouth open to approach pathology through this corridor when required. A 0-degree endoscope is used for the procedure. A 45-degree endoscope is useful when exposure is limited. An angled drill handpiece is most useful to navigate the curve of the palate. A straight handpiece may also be used. If the angle makes it difficult to use through the nose, we use the drill through the mouth and visualize through the nose; this gives a wide field of vision and a superior ability to visualize the instrument ends. Nasal endoscopy is done, and the posterior nasal septum is removed. Removal
ENDOSCOPIC APPROACHES TO CV JUNCTION AND ODONTOID PROCESS
of the septum facilitates angulation and increases the space for maneuvering the scope and instruments during the procedure. Mini-Hadad-Bassagasteguy (HB) flaps on both sides extending only to the bone-cartilage junction are raised. The mini-HB flap has its vascular pedicle on the septal branch of the sphenopalatine artery similar to a standard HB flap, but it is not as wide as the standard HB flap, and only the inferior half of the septum is used. With flaps on both sides, only half the width is needed because it is doubled with the 2 flaps coming together. The sphenoid sinuses are opened wide after the flaps are raised to allow the flap to be “parked” in the sphenoid until it is needed for the reconstruction. To reconstruct the nasopharynx and defect over the first and second cervical vertebrae (C1eC2), one may use a HB flap with a reverse flap from the other side to cover the bare cartilage. If the sphenoid is involved or its floor needs to be drilled, the maxillary sinuses are opened posteriorly, and the flaps are tucked into the sinuses. After the flaps are raised and “parked,” the posterior septectomy can be done by removing the perpendicular plate of ethmoid and posterior vomer bone down to the floor of the nose to the choana. This inferior removal of bone improves visibility and allows better retraction of the uvula and soft palate anteriorly. A rubber catheter can be passed through the nostril and out the mouth to pull the palate anteriorly. When the nasal exposure is complete, the vertical extent of the pathology is
Figure 1. Image-guided navigation systems are used in all cases. They are employed to define the vertical limits of the nasopharyngeal flap based on the pathology. (A) Navigation system being used (through the nose) at the
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assessed; navigation is useful here (Figure 1). Based on the extent, a nasopharyngeal mucosal flap, based inferiorly, is raised. The nasopharyngeal flap starts just under the roof as an inverted “U” incision because the tissue over the adenoids may be friable, especially in pediatric patients. The incision extends to the muscle layer but not through it. The upper half of the incision is done by instrumentation through the nose, but as one gets lower, it is easier to raise this flap through the mouth. The lateral limits of the flap are medial to the eustachian tube openings. Lateral to these lie the parapharyngeal carotid artery. The attachments of the muscles are elevated off the clivus, anterior arch of C1, and dens. At this time, one also appreciates the additional “hands.” While the ear, nose, and throat surgeon holds the scope and provides vision and suction from above, the neurosurgeon can retract the flap with a forceps and incise with a cautery to raise and lower the flap to the required level. When the level is reached, the flap is allowed to stay in the oropharynx and can be weighed down so that it does not obstruct vision or instrumentation (Figure 2). Drilling the anterior arch of the atlas is done with various cutting and diamondtipped burrs. After the anterior arch is drilled out, the ligaments are cut; this is followed by drilling the odontoid process. As with the standard transoral procedure, the dens is hollowed out, and then the shell is excised after cutting its
beginning of the decompression to define the upper limit. (B) Lower limit for decompression being defined (through the mouth). (C) Navigation system being used to check the thickness of the dens after initially thinning it out.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.025
PEER-REVIEW REPORTS CHANDRASHEKHAR E. DEOPUJARI ET AL.
ENDOSCOPIC APPROACHES TO CV JUNCTION AND ODONTOID PROCESS
complete the C1eC2 closure and sutured with a 3-0 polyglactin suture. A nasogastric feeding tube is inserted under vision. The nasogastric tube is removed early in the postoperative period when the patient is able to swallow properly. Patients are electively ventilated for 24 hours and extubated after confirming neurologic function. RESULTS We have used the combined nasal and oral endoscopic approach described in this article for pathologies including fixed atlantoaxial dislocation and clivus chordomas. Of the patients with fixed atlantoaxial dislocation, 2 had a history of posterior decompression and fixation and continued to experience progressive symptoms secondary to ventral compression (Figures 3 and 4). Postoperative morbidity was reduced with endoscopic procedures. Because the palate is not split, the velopharyngeal reflex is not impaired significantly, which helps patients’ swallowing. Healing of the nasopharynx also takes place relatively unhindered. DISCUSSION
Figure 2. Operative procedure photos. (A) The limits of the inverted “U” nasopharyngeal mucosal flap are shown. The flap is limited laterally by the eustachian tube openings. The vertical extent can begin high in the nasopharynx. (B) After the flap is raised, the muscles are cut and elevated off the lower clivus, anterior arch of C1, and over C2. (C) The anterior arch of C1 is drilled out, and soft tissue and ligaments are excised to expose the odontoid process. (D) The odontoid is drilled out, first by thinning out the core and then excising the shell of bone. (E) After the decompression is complete, the dura mater is seen bulging through the decompression defect.
attachments. After the dens is drilled out, the tectorial membrane is incised. At the end of the decompression, the dura mater is seen bulging. Image guidance is used to ascertain the extent and completeness of the bony decompression. At this point, it is important to reconstruct the defect. In case of a large cerebrospinal fistula, such as may be discovered incidentally during odontoidectomy or after intradural pathology has been tackled (i.e., a clivus chordoma), the
repair needs to be more complete and secure and is in multiple layers. We usually use fascia lata as an internal closure layer with fat above. Fibrin glue is used to fix them in place. When there is no leak, the defect is filled only with fat and fixed with glue. The outer closure in either case is effected by the 2 mini-HB flaps and the nasopharyngeal flap. The 2 septal flaps are rotated to cover the clivus and roof of the nasopharynx area, whereas the inverted “U” nasopharynx flap is replaced to
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Retracting the soft palate anteriorly using a fine catheter passed through the nostril and taken out of the oral cavity to pull the palate forward aids in producing a panoramic view of the entire area from sphenoid to C2 using an endoscope. To clarify the issue of conflicting straight surgical instruments with the endoscope, we have found instrumentation through the oral cavity to be easier. Nasal endoscopy allows for vision and irrigation through the nose, whereas the neurosurgeon can perform the surgery through the open mouth. This approach gives the surgeon greater freedom of movement, avoiding conflict with the endoscope. Also, it is easier because the surgical instruments are in a straighter plane. A slight flexion of the neck makes it easier to access the nasopharynx from the nose, but too much flexion must be avoided because that would affect transoral instrumentation. To avoid anterior septal surgery and the associated morbidity with raising a formal full HB flap, we used a combination of flaps. The horizontal limb of the nasopharyngeal mucosal flap is
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Figure 3. A 10-year-old boy with congenital mobile atlantoaxial dislocation was operated on by posterior fusion at a younger age. The anterior compression continued to increase, and the child experienced progressive neurologic worsening. (A) Sagittal magnetic resonance imaging with anterior cervicomedullary compression with signal intensity changes. The patient underwent an endoscopic odontoidectomy successfully. (B) Sagittal computed tomography scan performed after the surgery shows adequate ventral decompression.
taken just below the roof, and vertical limbs are dropped on either side staying medial to the eustachian tubes. This modification prevents damage to the eustachian tubes and ensures against accidental injury to the internal carotid artery—except in the case of an aberrant internal carotid artery. We believe that the above-described simple modification in reconstruction can reduce some of the morbidity associated with a formal HB flap. The flaps are simpler to raise, there is no exposure of bone cartilage, the combined width of the 2 flaps may be wider,
suturing of the reverse flap is not required, and crusting and postoperative care for the nose are reduced. The flaps could be sutured to each other, but we prefer not to do that and instead allow it to fall flat on the fat, to avoid potential dead space between the flaps and fat. A Merocel (Medtronic Xomed Inc., Jacksonville, FL, USA) pack is kept for 3e4 days to maintain pressure and keep the flaps in position. Postoperative healing is good because there are almost no raw or exposed areas in the nose or nasopharynx. Traditional ventral surgical approaches to the craniocervical junction include the
transoral odontoidectomy using a microscope. Other approaches such as the high cervical retropharyngeal approaches are also described. Visualization of the surgical field largely depends on the depth at which the operative site is from the microscope or eye. With a microscope, one has a cylindrical/conical perspective. Although modern microscopes with their maneuverability can look at the edges of the field, vision may be compromised if there are barriers. Endoscopic vision differs because the depth from the operative site is very small, and corners can be looked at by angulating the scope or using angled scopes. The main disadvantage of the endoscope is the lack of depth perception. This lack of depth perception is usually overcome by moving the scope in and out; this is advantageous in ventral odontoidectomy where the barrier of the palate does not hinder vision. Based on the vertical extent of decompression necessary, traditional transoral procedures may require splitting the soft palate and may even necessitate splitting the hard palate. Both of these maneuvers are known to cause postoperative swallowing difficulties secondary to the disruption of the velopharyngeal mechanism. This additional step is not needed when using the endoscope. When the mouth is being used as a corridor, the soft palate is moved out of the way via a rubber catheter sling, through the nostril and out through the mouth. CONCLUSIONS Any surgical intervention at this complex anatomic site has to be a carefully considered decision based on one of the currently accepted algorithms. Endoscopic procedures have added an option to this decision-making algorithm. REFERENCES 1. Abuzayed B, Tanriover N, Ozlen F, Gazioglu N, Ulu MO, Kafadar AM, Eraslan B, Akar Z: Endoscopic endonasal transsphenoidal approach to the sellar region: results of endoscopic dissection on 30 cadavers. Turk Neurosurg 19:237-244, 2009.
Figure 4. A 56-year-old man presented with progressive spastic quadriparesis. Imaging revealed a fixed atlantoaxial dislocation with cervicomedullary compression seen more posteriorly. He was operated on elsewhere with a posterior fusion and fixation with a loop. His symptoms worsened a few years later. (A) Sagittal computed tomography cisternogram with predominant ventral cervicomedullary compression. The patient was operated on using the endoscopic techniques described in the present article. (B) Sagittal computed tomography image obtained after surgery. The patient experienced satisfactory neurologic improvement.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 18 September 2013; accepted 25 July 2014
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CH, AB:
Citation: World Neurosurg. (2014) 82, 6S:S49-S53. http://dx.doi.org/10.1016/j.wneu.2014.07.025 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved.
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