Chapter 21 Endoscopic Approaches to the Craniovertebral Junction
Introduction
The standard transoral approach for odontoidectomy has been a widely accepted surgical procedure to decompress the soft-tissue and osseous mass lesions at the anterior craniovertebral junction (CVJ). There have been several series published in the past two decades showing satisfactory clinical results of this transoral approach.1–4 Detailed surgical techniques and nuance of transoral surgery have been described in detail by multiple authors in the literature.1,3–7 In addition, other approaches to the anterior or lateral CVJ with wider exposures, which often involve more aggressive osteotomies along the surgical corridor, have been reported. For example, such extensive surgical approaches include palate splitting, mandibulotomy, or trespassing the maxillary sinus, and even a zygomatic process or other extensive craniotomies. Under microscopes or loupe with head lights, these extensive approaches allow magnification and illumination of the deeply seated anterior CVJ and surgical maneuver of the neural tissue. However, as these microscopic approaches require wide exposures, they inevitably carry problems of reconstruction, including both cosmetic and functional.
Endoscopic approaches have emerged and prevailed in the past decade for many skull base cases.8–11 Using the endoscope, magnification and illumination can be achieved easily. Moreover, the endoscope provides a remarkably more panoramic view of the deeply seated CVJ than microscopes. Around the CVJ, which usually requires a working corridor of length 8 to 10 cm, the viewing angle and working space are inherently limited through the microscopes. In contrast, the endoscope can move the surgeons’ eyes closer to the target of pathology and thus gain a greater panoramic view of surrounding structures. Moreover, by introducing the endoscope at an angled view (e.g., the 30-, 45-, and 70-degree-angled endoscopes), significantly greater and wider visualization can be achieved. Surgical manipulation of the structures seen under the endoscope often also requires specialized instruments, which have a bayonet-shaped long shaft, or mechanisms that could convert the direction of force. The endoscopic approaches to the anterior CVJ are less invasive than traditional microscopic surgery because they require less exposure and thus less compromise to the normal anatomic structures and physiologic functions. For example, an endoscopic transnasal transclival odontoidectomy can achieve similar decompression at the anterior CVJ while allowing less velopharyngeal insufficiency and earlier oral intake than the traditional transoral odontoidectomy performed under microscopes.8,10,11
21.1 Surgical Approaches
Endoscopic approaches provide a panoramic view through a deep working channel with sufficient magnification and illumination. Together with specialized instruments and image guidance, which can be fluoroscopy or a navigation system if required, surgery of the anterior CVJ can be performed with a few comorbidities. Over the past 15 years, approximately 100 patients with pathologies around the CVJ were treated in our institute using endoscopic approaches. Among them, the most common pathologies were (in frequency) chordoma, compression related to odontoid process, pituitary macroadenoma with skull base involvement, chondrosarcoma, meningioma, metastatic carcinoma, sarcoma of the skull-base, epidermoid tumor, and others ( Table 21.1 ).
Pathology | Case number (%) |
Chordoma | 34 (33.7%) |
Odontoid compression | 15 (14.9%) |
Pituitary adenoma | 11 (10.9%) |
Chondrosarcoma | 8 (7.9%) |
Meningioma | 8 (7.9%) |
Carcinoma (metastatic) | 5 (5%) |
Sarcoma | 4 (4%) |
Epidermoid tumor | 4 4%) |
Fibrous dysplasia | 3 (3%) |
Craniopharyngioma | 2 (2%) |
Giant cell tumor | 2 (2%) |
Abscess | 1 (1%) |
Anaplastic ependymoma | 1 (1%) |
Cerebrospinal leakage | 1 (1%) |
Inflammatory pseudotumor | 1 (1%) |
Multiple myeloma | 1 (1%) |
Endoscopic surgery to address pathologies of the anterior CVJ can be categorized into two types, namely, transnasal and transoral, according to high- or low-lying pathologies in relation to the palate.9 These two endoscopic approaches can be combined during the same operation, but the palatal line is an important anatomic consideration in the selection of the surgical approach.
21.1.1 Endoscopic Transnasal Approach
The transnasal endoscopic approach is best used when the target pathology of the CVJ lies higher than the palate.
There are various kinds of pathologies, including both extradural and intradural, at the ventral CVJ that can be dealt with using the endoscopic transnasal corridor. Accordingly, the transnasal endoscopic approach involves two modifications: transnasal transsphenoidal and transnasal transclival approaches, respectively.
A: Endoscopic Transnasal Transsphenoidal Approach
This approach targets lesions at the upper and middle clivus. Laterally, this endoscopic approach is limited by the eustachian tubes and medial pterygoid plates. Typically, the nasal turbinates are pushed and out-fractured but not resected during this approach. The surgery can be performed via one nostril, and frequently it is convenient to use a nasal speculum to maintain an appropriate working space and to keep the endoscopic lens uncontaminated. The endoscope can be held either with a pneumatic-controlled scope-holder or by an assistant surgeon.10–13
In this approach, a “rescue flap” mucosal incision is first made and the nasal septum is pushed toward the contralateral side after submucosal dissection. The sphenoid rostrum is removed widely, as low as possible, and the clivus bone is then drilled to expose the anterior CVJ. Extradural pathologies of this region can thus be addressed easily. For intradural targets, there is an inevitable problem of cerebrospinal fluid (CSF) leakage, which requires reconstruction. In our earlier experiences, multilayered repair of a skull base bony defect using facia, autologous fat, and bone grafts was performed to prevent postoperative CSF leakage for intradural pathologies. However, approximately 7 years ago we adapted the pedicled nasoseptal flap plus multilayered reconstruction. Since then we have experienced a very high success rate in repairing the dural defect for intradural and intra-arachnoid lesions such as meningioma, craniopharyngioma, and epidermoid tumor, using the following procedure.
Surgical Steps
The patient was put in a supine position under general anesthesia. The neuronavigation and/or fluoroscopy was set. The nasal cavity and the right low abdomen were disinfected and draped (to harvest fascia or fat graft whenever necessary).
The rigid-rod straight 0-degree endoscope was used to identify the inferior, middle and superior turbinates, and the choana. The one-side middle turbinate was out-fractured or removed for better exposure. The superior arm of the pedicled nasoseptal flap was incised (“rescue flap” incision) and submucosal dissection was done. The nasal septum could then be pushed contralaterally to expose the sphenoidal rostrum.
The sphenoidal rostrum was widely opened as low as possible using Kerrison′s rongeurs or drills.
The clivus bone, sella turcica, bilateral clival protuberances of internal carotid artery (ICA), and lower clivus were subsequently identified.
These bony structures were drilled and punched superiorly to the pituitary fossa (including dorsum sellae and the posterior clinoid process if needed), bilaterally to both ICA margins, and inferiorly to the lower clivus bone as needed. The ICA flow could be detected with the micro-Doppler and its location verified with neuronavigation. Venous oozing from the clival dura or venous plexus was managed with packing of Gelfoam or other hemostatic agents.
Epidural lesions could be removed at this stage. The wound was repaired with Gelfoam or fat graft, and then sealed by tissue glue.
For intradural lesions, the dura matter had to be opened. The intradural maneuver of the pathology required more caution and was repaired in multilayers by Gelfoam, fascia, fat, and bone grafts. The pedicled nasoseptal flap was then raised to cover the operative wound to ensure closure.
Case Examples
Case A: A 14-year-old girl had rapidly progressive double vision 1 week prior to admission. Her diplopia was associated with severe headache, dizziness, nausea, and vomiting. The CSF examination from lumbar puncture was negative for evidence of meningitis. The magnetic resonance imaging (MRI) demonstrated a 2.7-cm chordoma involving upper, middle, and lower clivus, retrosellar area, dorsum sellae and medial posterior clinoid process, left Dorello′s canal, and left posterior cavernous sinus. An endoscopic transnasal transsphenoidal surgery without resection of the nasal turbinates was performed to remove this tumor, which involved bone (clivus, sella, and dorsum sellae, part of the posterior clinoid process). The wound was impacted with a small piece of fat tissue without a nasoseptal flap. This girl experienced a full recovery of preoperative abducent palsy within 2 weeks after surgery. The postoperative MRI confirmed complete removal of the chordoma. Her hormonal functions were all normal. She has remained disease-free since then. There was no tumor recurrence as demonstrated by MRI taken 4 years post-peration ( Figs. 21.1 and 21.2 ).
Case B: A 61-year-old woman had suffered from dizziness and unsteady gait for 2 years. She also had difficulty in swallowing and had hoarseness of voice for half a year. The MRI demonstrated a 4-cm meningioma at the middle and lower clivus, causing compression to the pons and medulla as well. The endoscopic transnasal transsphenoidal transclival approach was used to resect this tumor. Postoperative CSF leakage with resultant meningitis was noticed 2 weeks after surgery, and she received a second endoscopic transnasal surgery with continuous lumbar drainage to repair the CSF rhinorrhea. A ventriculoperitoneal shunt was placed later for meningitis-related hydrocephalus. The patient maintained her neurologic functions as per preoperation. Serial MRI follow-ups (the last at 7 years after surgery) showed a 1.5-cm residual tumor without progression ( Figs. 21.3 and 21.4 ).
B: Endoscopic Transnasal Transpharyngeal Approach
The endoscopic transnasal transpharyngeal approach targets the lower clivus, odontoid process, and upper C2 regions. The lateral limit of this approach is the eustachian tube. Pathologies of this area include bony deformity of CVJ with compression to the medulla, the spinal cord at the medullo-cervical junction, and neoplasms. It is worthwhile mentioning that it is extremely difficult to tightly close the operative wound in this approach, owing to the narrow surgical corridor and long distance of reach. Therefore, we avoided as far as possible operating on intradural lesions using this approach because of the high risks of postoperative CSF leakage.
Related posts:
Chapter 20 Transclival Approach
Chapter 22 The “Far Medial” (Transcondylar/Transtubercular) Approach to the Inferior Third of the Clivus
Chapter 23 Jugular Foramen Approach
Chapter 19 Pituitary Gland Transposition and Retrosellar Approach
Chapter 6 Medial Maxillectomy
Chapter 28 Retrosigmoid–Transclival Approach
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
