1

Introduction

Considered the “gold standard” for anterior access to the craniocervical junction (CCJ), the transoral approach has been widely used to gain exposure of diverse pathologies involving the rostral cervical spine and atlantoaxial regions . However, this approach often entails significant disruption of the tongue or palate, and is associated with a significant risk of velopharyngeal incompetence and prolonged dysphagia necessitating postoperative gastrostomy use . In many cases, tracheotomy is performed routinely . Additional disadvantages of the technique include field contamination, infection, and wound dehiscence .

Extraoral anterolateral transcervical approaches have also been used to access the CCJ without entry into the hypopharynx or oral cavity . Access through a retropharyngeal prevascular or retrovascular approach entails a skin incision, which enables wide surgical exposure while avoiding oropharyngeal contamination. Nevertheless, transcervical dissection places multiple neurovascular structures contained in the carotid sheath at risk, as well as the recurrent laryngeal nerve, esophagus, and trachea .

With technological advances in endoscopic surgery, less invasive approaches to the anterior skull base and CCJ have evolved. Previously described endoscopic endonasal transclival and transodontoid approaches have allowed surgeons to overcome many of the morbidities and complications associated with transoral or transcervical approaches . Traditionally both endonasal approaches employ a posterior bony and mucosal septectomy. Resection of the mucosa over the posterior nasal septum may compromise the integrity of the vascularized pedicled nasoseptal flap (PNSF) as a reconstructive option. Here, we describe a new variation which preserves the mucosal integrity of the posterior nasal septum.

2

Illustrative case

A 61-year-old woman with a history of rheumatoid arthritis presented with progressive bilateral upper extremity and left lower extremity weakness. She had a prior posterior C1-2 fixation for instability and degenerative pannus at another institution four years earlier. However, in the last year, she developed progressive quadriparesis. At the time of presentation to our institution, computed tomography (CT) showed a non-union and hardware failure at the prior C1-2 fixation construct, and magnetic resonance imaging (MRI) revealed a recurrent C1-2 pannus with worsening basilar invagination causing brainstem and craniocervical spinal cord compression ( Fig. 1 ). The patient subsequently underwent an endoscopic endonasal transclival transodontoid approach to the anterior CCJ to resect the odontoid process and compressive pannus followed by an occipitocervical stabilization and fusion. A mucosal-septum sparing variant was selected in order to preserve nasoseptal tissue for reconstruction without compromising panoramic surgical exposure or instrumentation. The patient underwent successful resection of the rheumatoid pannus with excellent brainstem decompression ( Fig. 1 ).

(A) Preoperative sagittal CT scan showing the posterior displacement of the odontoid process. (B) Postoperative sagittal CT scan after endoscopic endonasal resection of the superior portion of the odontoid process and inferior clivus. (C) Preoperative T2-weighted MRI showing compression of the brainstem by the odontoid process and rheumatoid pannus. (D) Postoperative T2-weighted MRI showing CSF around the decompressed brainstem.

2.1

Mucosal-sparing septectomy technique ( Video 1 )

At our institution, endoscopic endonasal skull base surgery is carried out in a collaborative fashion by an otolaryngologist and neurosurgeon both specializing in endoscopic skull base surgery. This dual-surgeon approach permits the use of bimanual dissection techniques, and the use of up to 4 instruments simultaneously (after binostril access is established). Intraoperative stereotactic navigation with a CT angiogram and neurophysiological monitoring with somatosenosory and motor evoked potentials are employed.

The patient is positioned supine with the head in three-point fixation using a Mayfield head holder. The nasal cavity is prepped with an iodine-based solution. Topical oxymetazoline is applied to the nasal cavities bilaterally. A 30-degree rigid endoscope is used for the entire operation to provide an additional viewing angle towards the CCJ.

The bilateral inferior and middle turbinates are lateralized. Full visualization and instrumentation in this region typically require posterior septectomy. Usually, posterior septectomy entails the resection of varying quantities of bone and mucosa. In our mucosal-sparing septectomy, we begin by elevating a right-sided PNSF based on the posterior septal branch of the sphenopalatine artery ( Fig. 2 A , dashed outline). The anterior limit of the incision determines the length of the PNSF, which is in turn determined by the expected size and location of the surgical defect or the amount of space necessary for adequate triangulation of instruments. Blunt dissection in a submucoperichondrial and submucoperiosteal plane is carried posteriorly toward the vascular pedicle. The PNSF is then tucked into the ipsilateral middle meatus for protection; at the same time, the pedicle is maintained in a safe location superior to the level of the choana ( Fig. 2 B). The same procedure is repeated on the left side with care taken to harvest a different size PNSF to prevent making the incisions directly opposite the contralateral previously elevated PNSF (i.e. the septal incisions are off-set). With both PNSFs elevated, the posterior bony septum can then be resected as needed for adequate exposure and to facilitate instrumentation ( Fig. 2 C).

(A) Intraoperative 30-degree endoscopic photograph roughly depicting the incision line for the right PNSF. (B) After the right PNSF is elevated, it is stored superiorly between the middle and inferior turbinates. (C) Endoscopic view after elevation of bilateral PNSFs and posterior septectomy. (D) After endoscopic endonasal approach to the CCJ, the PNSFs are repositioned and sutured in place. PNSF = pedicled nasoseptal flap.

If one or both PNSFs are needed for reconstruction, they are laid down onto the defect and supported accordingly with nasal packing. In this illustrative case, no cerebrospinal fluid (CSF) leak was encountered, and the use of a PNSF was not necessary. The PNSFs were returned to their native positions and secured in place with absorbable suture in a quilting pattern ( Fig. 2 D).