Endonasal access to the upper cervical spine, part one: radiographic morphometric analysis

Endoscopic endonasal approaches to the craniovertebral junction: The Otolaryngologist's perspective

Objective

To review indications and techniques for the endoscopic endonasal approach to the craniovertebral junction (CVJ), analyze postoperative outcomes, and discuss important technical considerations.

Methods

A retrospective analysis was performed on all patients undergoing endonasal endoscopic approaches to the CVJ from May 2007 to June 2017. Demographic information, presenting symptoms, imaging results, treatment course, postoperative functional status, and follow-up were recorded.

Results

There was a total of 30 patients in this series, with a mean follow-up of 11.7 months. The average age was 33.6 years (range, 5–75 years), with 18 females and 12 males. The majority of patients (n = 22, 73.3%) had Chiari malformation type 1 with basilar invagination and symptomatic cervicomedullary compression as the indication for surgery. Intraoperative cerebrospinal fluid leak (CSF) was noted in 3 cases of odontoid resection and a single case of skull base resection. There were no postoperative CSF leaks. Overall, 81% of patients resumed regular diet by post-operative day 2 (range, 0–8 days). Severe postoperative dysphagia occurred in two cases with one requiring gastrostomy tube placement and another utilizing total parenteral nutrition for support prior to eventual gastrostomy. On average, patients were extubated by postoperative day 0.93 (range 0–3 days), with 85% extubated by postoperative day 1. A tracheotomy was required in one patient.

Conclusion

The endonasal endoscopic approach is a valuable technique for access to the CVJ with minimal disruption of respiratory and alimentary function.

Endoscopic endonasal transclival approach to the ventral brainstem: Radiologic, anatomic feasibility and nuances, surgical limitations and future directions

The endoscopic endonasal transclival approach (EETA) is less invasive than traditional open approaches; however, there is currently limited data on the pre-operative features that may predict success of the EETA. Surgical landmarks and exposure of the EETA and expanded EETA are assessed. We retrospectively measured multiple anatomic features in 154 adult dry skulls, 22 C1 and C2 dry bone vertebrae, and 500 paranasal sinus computed tomography (CT) scans. We also dissected 13 formalin-fixed, silicone-injected adult cadaveric heads. Relevant qualitative and quantitative data were obtained with CT (n = 10) and cadaveric dissection (n = 13). They are expressed as mean (SD), as appropriate and compared with unpaired t tests. Categorical variables were compared with χ² tests. We determined the prevalence of clival and sphenoid sinus anatomic variations and assessed potential exposure of the craniovertebral region, based on the relative position of the nasal bone tip, posterior point of the hard palate, and their relation to the position of C1 and C2. Depending on anatomic features, EETA should allow visualization of the ventral brainstem. The mean (SD) dimensions of the surgical window for EETA were 43.2 (5.1) × 18.3 (1.1) mm, in the craniocaudad and horizontal dimensions, respectively. The craniocaudad dimension enlarged to 60.2 (4.7) mm with expanded EETA. The EETA allowed satisfactory exposure for odontoid and C1 anterior arch resection (expanded EETA) in all specimens, regardless of the orientation of the palate. The combination of preoperative radiographic assessment and intraoperative considerations allows safe and effective application and facilitate selection of the most appropriate approach.

The Endonasal Endoscopic Approach to Pathologies of the Anterior Craniocervical Junction: Analytical Review of Cases Treated at Four European Neurosurgical Centres

Supported by preliminary anatomical and clinical studies exploring the feasibility and usefulness of approaching many ventral pathologies of the craniocervical junction (CCJ) using the endoscopic endonasal approach, four European centres have joined forces to accumulate and share their growing surgical experience of this advanced technique. By describing the steps that led to the development and continuous refinement of this approach to the CCJ, this article delves deeply into an analysis of the cases operated on since 2010 at these four institutions, and discusses in detail the operative nuances that so far have allowed achievement of successful outcomes with excellent perioperative patient comfort and satisfactory long-term quality of life.

Endoscopic Transseptal Approach with Posterior Nasal Spine Removal: A Wide Surgical Corridor to the Craniovertebral Junction and Odontoid: Technical Note and Case Series

BACKGROUND

The transnasal approach to lesions involving the craniovertebral junction represents a technical challenge because of limited inferior exposure. The endoscopic transseptal approach (EtsA) with posterior nasal spine (PNS) removal is described. This technique can create a wide exposure of the craniovertebral junction, thereby increasing the caudal exposure.

METHODS

On patients undergoing anterior craniovertebral junction decompression, we calculated the degree of exposure on the sagittal plan through a paraseptal route, an EtsA without and with PNS removal. The horizontal exposure and working area with the latter approach were also evaluated.

RESULTS

Five patients underwent the transnasal procedure. The age of patients ranged from 34-71 years. All patients harbored basilar impression. The mean postoperative Nurick grade (1, 8) was improved versus the average preoperative grade (3). The average follow-up duration was 16 months. All patients underwent occipitocervical fixation. The mean vertical distances, from the clinoid recess to the inferior most limit with the paraseptal approach, EtsA without and with PNS removal were 38.52, 44.12, and 51.16 mm, respectively. The difference between our approach and a standard paraseptal route was statistically significant (P = 0.041; P< 0.05). The mean horizontal distances were 31.68 mm (mononostril entry) and 35.37 mm (binostril entry). The mean working area was 1795.53 mm².

CONCLUSIONS

Endoscopic endonasal approaches to the craniovertebral junction are increasing, but the downward extension on the anterior cervical spine represents a limit. Therefore, many surgeons prefer transoral or transcervical approaches. The EtsA with PNS removal allows for a more caudal exposure than the standard paraseptal approach, with reduced nasal trauma.

The endoscopic endonasal approach to cranio-cervical junction: the complete panel

We aim to establish a complete summary on the Endoscopic Endonasal Approach (EEA) to Cranio Cervical Junction (CCJ): evolution since first description, criteria to predict the feasibility and limitations, anatomical landmarks, indications and biomechanical evaluation after performing the approach. A comprehensive literature search to identify all available literature published between March 2002 and June 2015, the articles were divided into four categories according to their main purpose: 1- surgical technique, 2- anatomical landmarks and limitations, 3- literature reviews to identify main indications, 4- biomechanical studies. Thereafter, we demonstrate the approach step-by-step, using 1 fresh and 3 silicon injected embalmed cadaveric specimen heads. 61 articles and one poster were identified. The approach was first described on cadaveric study in 2002, and firstly used to perform odontoidectomy in 2005. The main indication is odontoid rheumatoid pannus and basilar invagination. The nasopalatine line (NPL), the superior nostril-hard palate Line (SN-HP), the naso-axial line (NAxL), the rhinopalatine Line (RPL) and other methods were described to predict the anatomical feasibility of the approach. The craniocervical fusion is potentially unnecessary after removal of < 75% of one occipital condyle. A recent cadaveric study stated the possibility of C1-C2 fusion via EEA. This paper reviews all available clinical and anatomical studies on the EEA to CCJ. The approach marked a significant evolution since its first description in 2002. Because of its lesser complications compared to the transoral approach, the EEA became when feasible, the approach of choice to the ventral CCJ.

Nasoseptal flap necrosis: a rare complication of endoscopic endonasal surgery

OBJECTIVE The vascularized nasoseptal flap (NSF) has become the workhorse for skull base reconstruction during endoscopic endonasal surgery (EES) of the ventral skull base. Although infrequently reported, as with any vascularized flap the NSF may undergo ischemic necrosis and become a nidus for infection. The University of Pittsburgh Medical Center's experience with NSF was reviewed to determine the incidence of necrotic NSF in patients following EES and describe the clinical presentation, imaging characteristics, and risk factors associated with this complication. METHODS The electronic medical records of 1285 consecutive patients who underwent EES at the University of Pittsburgh Medical Center between January 2010 and December 2014 were retrospectively reviewed. From this first group, a list of all patients in whom NSF was used for reconstruction was generated and further refined to determine if the patient returned to the operating room and the cause of this reexploration. Patients were included in the final analysis if they underwent endoscopic reexploration for suspected CSF leak or meningitis. Those patients who returned to the operating room for staged surgery or hematoma were excluded. Two neurosurgeons and a neuroradiologist, who were blinded to each other's results, assessed the MRI characteristics of the included patients. RESULTS In total, 601 patients underwent NSF reconstruction during the study period, and 49 patients met the criteria for inclusion in the final analysis. On endoscopic exploration, 8 patients had a necrotic, nonviable NSF, while 41 patients had a viable NSF with a CSF leak. The group of patients with a necrotic, nonviable NSF was then compared with the group with viable NSF. All 8 patients with a necrotic NSF had clinical and laboratory evidence indicative of meningitis compared with 9 of 41 patients with a viable NSF (p < 0.001). Four patients with necrotic flaps developed epidural empyema compared with 2 of 41 patients in the viable NSF group (p = 0.02). The lack of NSF enhancement on MR (p < 0.001), prior surgery (p = 0.043), and the use of a fat graft (p = 0.004) were associated with necrotic NSF. CONCLUSIONS The signs of meningitis after EES in the absence of a clear CSF leak with the lack of NSF enhancement on MRI should raise the suspicion of necrotic NSF. These patients should undergo prompt exploration and debridement of nonviable tissue with revision of skull base reconstruction.

Endonasal Endoscopic Odontoidectomy in Ventral Diseases of the Craniocervical Junction: Results of a Multicenter Experience

BACKGROUND

Over the past decades, supported by preliminary anatomic and clinical studies exploring its feasibility and safety, experience has increased of the use of the endoscopic endonasal approach (EEA) to ventral diseases at the craniocervical junction (CCJ).

METHODS

A multicenter study was carried out over a 4-year period of 14 patients managed by EEA odontoidectomy for CCJ diseases causing irreducible atlantoaxial dislocation. The surgical setup included an IGS system based on computed tomography and magnetic resonance images fusion, and 0° and 30° angled endoscopes with dedicated endoscopic tools.

RESULTS

Nine men and 5 women, with a mean age of 60.7 years, were included. The mean follow-up was 28.5 months; 9 patients had basilar impression, whereas 5 had a degenerative pannus. The quality of anterior decompression was excellent in all cases; nonetheless, a posterior stabilization was deemed necessary in 13 patients, and no external orthosis was used during the postoperative course. No tracheostomy or gastrostomy was required after surgery; no deaths, no new neurologic deficits/complications, and no postoperative cerebrospinal fluid leak were recorded. At follow-up, the neurologic status assessed with Frankel grade did not deteriorate in any of the patients but improved in 13 of them; and no new listhesis was shown on neuroradiologic follow-up.

CONCLUSIONS

The results show that EEA provides a direct surgical corridor to the CCJ, allowing an adequate decompression as with the more invasive transoral route. Morbidity is less than with a transoral approach, resulting in higher patient comfort and faster recovery.

Endoscopic endonasal odontoid resection with real-time intraoperative image-guided computed tomography: report of 4 cases

The authors present 4 cases in which they used intraoperative CT (iCT) scanning to provide real-time image guidance during endonasal odontoid resection. While intraoperative CT has previously been used as a confirmatory test after resection, to the authors' knowledge this is the first time it has been used to provide real-time image guidance during endonasal odontoid resection. The operating room setup, as well as the advantages and pitfalls of this approach, are discussed. A mobile intraoperative CT scanner was used in conjunction with real-time craniospinal neuronavigation in 4 patients who underwent endoscopic endonasal odontoidectomy for basilar invagination. All patients underwent a successful decompression. In 3 of the 4 patients, real-time intraoperative CT image guidance was instrumental in achieving a comprehensive decompression. In 3 (75%) cases in which the right nostril was the predominant working channel, there was a tendency for asymmetrical decompression toward the right side, meaning that residual bone was seen on the left, which was subsequently removed prior to completion of the surgery. Endoscopic endonasal odontoid resection with real-time intraoperative image-guided CT scanning is feasible and provides accurate intraoperative localization of pathology, thereby increasing the chance of a complete odontoidectomy. For right-handed surgeons operating predominantly through the right nostril, special attention should be paid to the contralateral side of the resection, where there is often a tendency for residual pathology.

Endoscopic endonasal approach to the ventral brainstem: anatomical feasibility and surgical limitations

OBJECTIVE Sporadic cases of endonasal intraaxial brainstem surgery have been reported in the recent literature. The authors endeavored to assess the feasibility and limitations of endonasal endoscopic surgery for approaching lesions in the ventral portion of the brainstem. METHODS Five human cadaveric heads were used to assess the anatomy and to record various measurements. Extended transsphenoidal and transclival approaches were performed. After exposing the brainstem, white matter dissection was attempted through this endoscopic window, and additional key measurements were taken. RESULTS The rostral exposure of the brainstem was limited by the sella. The lateral limits of the exposure were the intracavernous carotid arteries at the level of the sellar floor, the intrapetrous carotid arteries at the level of the petrous apex, and the inferior petrosal sinuses toward the basion. Caudal extension necessitated partial resection of the anterior C-1 arch and the odontoid process. The midline pons and medulla were exposed in all specimens. Trigeminal nerves were barely visible without the use of angled endoscopes. Access to the peritrigeminal safe zone for gaining entry into the brainstem is medially limited by the pyramidal tract, with a mean lateral pyramidal distance (LPD) of 4.8 ± 0.8 mm. The mean interpyramidal distance was 3.6 ± 0.5 mm, and it progressively decreased toward the pontomedullary junction. The corticospinal tracts (CSTs) coursed from deep to superficial in a craniocaudal direction. The small caliber of the medulla with very superficial CSTs left no room for a safe ventral dissection. The mean pontobasilar midline index averaged at 0.44 ± 0.1. CONCLUSIONS Endoscopic endonasal approaches are best suited for pontine intraaxial tumors when they are close to the midline and strictly anterior to the CST, or for exophytic lesions. Approaching the medulla is anatomically feasible, but the superficiality of the eloquent tracts and interposed nerves limit the safe entry zones. Pituitary transposition after sellar opening is necessary to access the mesencephalon.

The rhinopalatine line as a reliable predictor of the inferior extent of endonasal odontoidectomies

OBJECT

The endoscopic endonasal approach (EEA) provides a minimally invasive corridor through which the cervicomedullary junction can be decompressed with reduced morbidity rates compared to those with the classic transoral approaches. The limit of the EEA is its inferior extent, and preoperative estimation of its reach is vital for determining its suitability. The aim of this study was to evaluate the actual inferior limit of the EEA in a surgical series of patients and develop an accurate and reliable predictor that can be used in planning endonasal odontoidectomies.

METHODS

The actual inferior extent of surgery was determined in a series of 6 patients with adequate preoperative and postoperative imaging who underwent endoscopie endonasal odontoidectomy. The medians of the differences between several previously described predictive lines, namely the nasopalatine line (NPL) and nasoaxial line (NAxL), were compared with the actual surgical limit and the hard-palate line by using nonparametric statistics. A novel line, called the rhinopalatine line (RPL), was established and corresponded best with the actual limit of the surgery.

RESULTS

There were 4 adult and 2 pediatric patients included in this study. The NPL overestimated the inferior extent of the surgery by an average (± SD) of 21.9 ± 8.1 mm (range 14.7-32.5 mm). The NAxL and RPL overestimated the inferior limit of surgery by averages of 6.9 ± 3.8 mm (range 3.7-13.3 mm) and 1.7 ± 3.7 mm (range -2.8 to 8.3 mm), respectively. The medians of the differences between the NPL and NAxL and the actual surgery were statistically different (both p = 0.0313). In contrast, there was no statistically significant difference between the RPL and the inferior limit of surgery (p = 0.4375).

CONCLUSIONS

The RPL predicted the inferior limit of the EEA to the craniovertebral junction more accurately than previously described lines. The use of the RPL may help surgeons in choosing suitable candidates for the EEA and in selecting those for whom surgery through the oropharynx or the facial bones is the better approach.

Endoscopic endonasal transclival transodontoid approach for ventral decompression of the craniovertebral junction: operative technique and nuances

The transoral approach is considered the gold-standard surgical route for performing anterior odontoidectomy and ventral decompression of the craniovertebral junction for pathological conditions that result in symptomatic cervicomedullary compression, including basilar invagination, rheumatoid pannus, platybasia with retroflexed odontoid processes, and neoplasms. Extended modifications to increase the operative corridor and exposure include the transmaxillary, extended "open-door" maxillotomy, transpalatal, and transmandibular approaches. With the advent of extended endoscopic endonasal skull base techniques, there has been increased interest in the last decade in the endoscopic endonasal transclival transodontoid approach to the craniovertebral junction. The endonasal route represents an attractive minimally invasive surgical alternative, especially in cases of irreducible basilar invagination in which the pathology is situated well above the palatine line. Angled endoscopes and instrumentation can also be used for lower-lying pathology. By avoiding the oral cavity and subsequently using a transoral retractor, the endonasal route has the advantages of avoiding complications related to tongue swelling, tracheal swelling, prolonged intubation, velopharyngeal insufficiency, dysphagia, and dysphonia. Postoperative recovery is quicker, and hospital stays are shorter. In this report, the authors describe and illustrate their method of purely endoscopic endonasal transclival odonotoidectomy for anterior decompression of the craniovertebral junction and describe various operative pearls and nuances of the technique for avoiding complications.

Endonasal Access to the Upper Cervical Spine: Part 2-Cadaveric Analysis

Objectives The study aims to determine factors that augment endonasal exposure of the cervical spine. Setting We used fluoroscopy and endoscopy to study endonasal visualization of the upper cervical spine. Participants Ten cadavers with normal anatomy were studied. Main Outcome Measures Endoscopic visualization was simulated with projected lines from an endoscope to the cervical spine in multiple positions. Results Neck position alone did not affect the extent of endonasal exposure of the upper cervical spine, although there was a trend correlating the extended neck position with more caudal exposure. The greatest impact was with concurrent use of a 30-degree endoscope and neck extension, and more caudal access was achieved by tilting the endoscope against the piriform aperture, using the posterior tip of the hard palate as the fulcrum. Conclusions Concurrent use of a 30-degree endoscope and neck extension increased the degree of exposure down the cervical spine. Maximum endonasal exposure of the upper cervical spine was obtained by maneuvering instruments at the fulcrum of the posterior hard palate and the nares, rather than changing the position of the neck alone. These results complement radiographic morphometric data in Part 1 of this study for preoperative assessment and surgical planning.

Basilar Invagination: Case Report and Literature Review

BACKGROUND

Basilar invagination is a rare clinical condition characterized by upward protrusion of the odontoid process into the intracranial space, leading to bulbomedullary compression. It is often encountered in adults with rheumatoid arthritis. Transoral microscopic or endonasal endoscopic decompression may be pursued, with or without posterior fixation. We present a case of basilar invagination with C1-C2 autofusion and discuss an algorithm for choice of anterior versus posterior approaches.

CASE DESCRIPTION

A 47-year-old woman with rheumatoid arthritis presented with severe occipital and cervical pain, dysphagia, hoarseness, and arm paresthesias. Findings on magnetic resonance imaging revealed moderate cranial settling with the odontoid indenting the ventral medulla but no posterior compression. Computed tomography demonstrated bony fusion at C1-C2 without lateral sag. Given autofusion of C1-C2 in proper occipitocervical alignment and the absence of posterior compression, the patient underwent endoscopic endonasal odontoidectomy without further posterior fusion, with satisfactory resolution of symptoms.

CONCLUSION

Endoscopic endonasal odontoidectomy offers a safe and effective method for anterior decompression of basilar invagination. Preoperative assessment for existing posterior fusion, absence of posterior compression, and preservation of the anterior C1 ring during operative decompression help stratify the need for lone anterior approach versus a combined anterior and posterior treatment.