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Endoscopic and Transnasal Approaches to the Craniocervical Junction
Summary of Key Points
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The endoscopic transnasal approaches provide a direct surgical trajectory to anteriorly located lesions at the craniocervical junction.
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Clinical series demonstrate low rates of postoperative infection after endoscopic transnasal approaches to intradural pathology despite nasal contamination.
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Endoscopic transnasal odontoidectomy allows preservation of the soft palate, and patients can restart an oral diet on the first postoperative day.
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On sagittal imaging, a line drawn from the anterior inferior nasal bone through the posterior aspect of the hard palate—the nasopalatine line—can predict the caudal limit of exposure of the upper cervical spine with a transnasal approach.
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Lesions extending lateral to the lower cranial nerves cannot fully be treated via an endonasal approach.
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A vascularized nasoseptal flap has dramatically reduced the incidence of postoperative cerebrospinal fluid leak.
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We recommend a two-surgeon, four-handed approach with collaborative expertise in rhinology and neurosurgery.
Neoplasms, infections, trauma, and inflammatory and degenerative conditions can all affect the craniocervical junction. Lesions located anterior or anterolateral to the medulla and upper cervical spinal cord present a formidable challenge, given the proximity of critical neurovascular structures. Early attempts to address these lesions via a posterior approach resulted in considerable morbidity and mortality, owing to retraction-related morbidity and poor visualization. , Various surgical approaches have been developed to treat these lesions more effectively, while minimizing morbidity. These include the far-lateral transcondylar, the extreme lateral, the lateral transatlantal or direct lateral, the transoral, and various endoscopic and transnasal approaches. At the craniocervical junction, endoscopic and transnasal approaches have been used primarily to treat lesions located anterior to the brain stem and upper cervical spinal cord.
Endoscopic and transnasal approaches were developed because they provide a direct surgical trajectory to anterior craniocervical junction pathologies with excellent operative visualization. The direct route reduces the need to manipulate surrounding neurovascular structures and can therefore reduce the risk of retraction-related morbidity. The benefit of the endoscope is that it increases illumination of the operative field, provides higher magnification with a wider angle of view, and increases depth of field. This chapter reviews common endoscopic transnasal approaches to the craniocervical junction and highlights important intraoperative and perioperative details.
Preoperative Evaluation
Routine preoperative imaging includes thin-slice (1-mm) computed tomography (CT) and magnetic resonance imaging (MRI). This is necessary to fully evaluate both the bony anatomy and the neurovascular relationships to the pathology. In addition, fusion of both the thin-slice CT and the MRI is performed for intraoperative computer-assisted navigation. Finally, the addition of a high-resolution constructive interference in steady state sequence can provide unparalleled detail regarding the relationship of cranial nerves to the pathology. In addition to radiographic evaluation, a critical component of preoperative evaluation is dedicated bilateral sinonasal endoscopy in the office. This evaluation is performed by the participating otolaryngologist to identify any anatomic variations, such as septal deviation, spur formation, or perforation, which would affect the operative approach or reconstruction. In addition, screening for concurrent paranasal sinus disease is needed to determine if preoperative antibiotic treatment is necessary. For pathology affecting the lower cranial nerves, a preoperative swallow evaluation and direct laryngoscopy can be performed to provide baseline function and counsel patients on expected postoperative risks if preoperative dysfunction exists.
Endoscopic Transnasal Surgical Technique
Operating Room Setup, Patient Positioning, and Equipment
The patient is positioned supine and is placed near the edge of the right side of the operative table. If posterior fixation has not been performed first, the head is placed in a neutral position using a rigid three-point fixation device. This is particularly important when cervical instability is present or expected after surgery. If posterior fixation has previously been performed then the patient may be simply placed on a foam donut without rigid fixation. For access to the odontoid process, the head is elevated slightly to align the surgical trajectory with the surgeon. Frameless stereotactic image guidance is used with all endoscopic transnasal cases. Most navigational systems have suctions that can be registered and navigated. Malleable suctions are also useful during the resection stage, as they can be manipulated to reach the surgical target and avoid conflict with the endoscope.
After nasal access is obtained, a two-surgeon approach is used for the remainder of the case. The endoscope is positioned at the apex of the right nostril and navigated by one surgeon. For a right-handed surgeon, a suction is placed underneath the endoscope in the right nostril, and a dissecting instrument is placed in the left nostril. Endoscopes are 4 mm in diameter, and the 0- and 30-degree lens angles are most commonly used for these approaches. An irrigation sheath on the endoscope can improve efficiency by reducing the time needed to clean the lens.
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