Comparison of endoscopic transnasal and transoral approaches to the craniovertebral junction

Quantitative Anatomical Studies in Neurosurgery: A Systematic and Critical Review of Research Methods

BACKGROUND

The anatomy laboratory can provide the ideal setting for the preclinical phase of neurosurgical research. Our purpose is to comprehensively and critically review the preclinical anatomical quantification methods used in cranial neurosurgery.

METHODS

A systematic review was conducted following the PRISMA guidelines. The PubMed, Ovid MEDLINE, and Ovid EMBASE databases were searched, yielding 1667 papers. A statistical analysis was performed using R.

RESULTS

The included studies were published from 1996 to 2023. The risk of bias assessment indicated high-quality studies. Target exposure was the most studied feature (81.7%), mainly with area quantification (64.9%). The surgical corridor was quantified in 60.9% of studies, more commonly with the quantification of the angle of view (60%). Neuronavigation-based methods benefit from quantifying the surgical pyramid features that define a cranial neurosurgical approach and allowing post-dissection data analyses. Direct measurements might diminish the error that is inherent to navigation methods and are useful to collect a small amount of data.

CONCLUSION

Quantifying neurosurgical approaches in the anatomy laboratory provides an objective assessment of the surgical corridor and target exposure. There is currently limited comparability among quantitative neurosurgical anatomy studies; sharing common research methods will provide comparable data that might also be investigated with artificial intelligence methods.

Functional Anatomy and Biomechanics of the Craniovertebral Junction

The craniovertebral junction (CVJ) involves the atlas, axis, and occiput along with the atlanto-occipital and atlantoaxial joints. The anatomy and neural and vascular anatomy of the junction render the CVJ unique. Specialists treating disorders that affect the CVJ must appreciate its intricate anatomy and should be well versed in its biomechanics. This first article in a three-article series provides an overview of the functional anatomy and biomechanics of the CVJ.

A two-stage combined anterolateral and endoscopic endonasal approach to the petroclival region: an anatomical study and clinical application

OBJECT

The pretemporal transcavernous anterior petrosal (PTAP) approach and the combined petrosal (CP) approach have been used to resect petroclival meningiomas (PCMs). In this cadaveric anatomical study, a two-stage combined PTAP and endoscopic endonasal far medial (EEFM) approach (the PTAPE approach) was compared morphometrically to the CP approach. A case study provides a clinical example of using the PTAPE approach to treat a patient with a PCM. The key elements of the approach selection process are outlined.

METHODS

Five cadaveric specimens underwent a CP approach and 5 underwent a PTAPE approach. The area of drilled clivus, length of multiple cranial nerves (CNs), and the area of brain stem exposure were measured, reported as means (standard deviations) by group, and compared.

RESULTS

The total area of the clivus drilled in the PTAPE group (695.3 [121.7] mm²) was greater than in the CP group (88.7 [17.06] mm², P < 0.01). Longer segments of CN VI were exposed via the PTAPE than the CP approach (35.6 [9.07] vs. 16.3 [6.02] mm, P < 0.01). CN XII (8.8 [1.06] mm) was exposed only in the PTAPE group. Above the pontomedullary sulcus, the total area of brain stem exposed was greater with the PTAPE than the CP approach (1003.4 [219.5] mm² vs. 437.6 [83.7] mm², P < 0.01). Similarly, the total exposure of the medulla was greater after the PTAPE than the CP exposure (240.2 [57.06] mm² vs. 48.1 [19.9] mm², P < 0.01).

CONCLUSION

A combined open-endoscopic paradigm is proposed for managing large PCMs. This approach incorporates the EEFM approach to address the limitations of the PTAP and the CP approach in a systematic fashion. Understanding the anatomical findings of this study will aid in tailoring surgical approaches to patients with these complex lesions.

Posterior midline approach to odontoidectomy: A novel method to treat basilar invagination

Background:

Basilar invagination (BI) is a common malformation of the craniocervical region where the odontoid process protrudes into the foramen magnum. Surgery in this region is difficult because of the complex anatomy of the craniocervical junction. Serious life-threatening complications have been observed with previously described approaches. Therefore, we conceived a novel surgical approach that can be implemented by neurosurgeons with different skill levels to facilitate better outcomes.

Methods:

We describe a new surgical technique for the treatment of BI that we used in two patients in whom cervical myelopathy and direct ventral compression of the cervicomedullary junction were confirmed through clinical and radiological findings. We present the technique of posterior odontoidectomy in a step-by-step, didactic, and practical manner with surgical tips and tricks.

Results:

The resection was completed without intraoperative or postoperative complications in both cases. The patients experienced substantial neurological improvements, and full recovery was observed during the 9-month and 12-month follow-up visits after discharge. Compared with the transoral approach, our technique provides a larger decompression area.

Conclusions:

We describe a novel method for the treatment of BI that was applied in two patients and suggest that the posterior approach might be a safe and effective method for ventral decompression of the craniocervical junction. Posterior odontoidectomy followed by craniocervical fixation helped achieve complete cervicomedullary decompression.

Metastatic Lesions of the Clivus: A Systematic Review

BACKGROUND

Metastatic lesions of the clivus are extremely rare, having previously been estimated as representing 0.02% of all intracranial tumors. Owing to its close intracranial relationship with the clivus before entering the cavernous sinus, clinical palsies of the sixth cranial nerve have been classically associated with destructive lesions of this structure.

METHODS

A comprehensive search of PubMed was conducted for studies of patients with metastasis to the clivus from primary cancer at any site. Studies reported in English in the past 20 years from our last search on April 12, 2021 were included. The data collected included patient age, sex, symptoms at presentation, histopathology and treatment timeline of the primary tumor, treatment, follow-up, and mortality.

RESULTS

After the literature review, 46 studies reporting on 58 patients with clivus metastasis were included in the final analysis. The mean age of the patients was 57.5 years, and 39 were male (67.2%). The most common sites of the primary tumor were the prostate (22%), gastrointestinal tract (15%), lung (13%), and kidney (11%). In 43% of patients, symptoms of clivus metastasis had presented before the diagnosis of primary cancer was known, and 71% of the patients had presented with sixth nerve palsy. Of the 58 patients, 53% had undergone surgery, and 37% had received adjuvant radiotherapy. Of the 58 patients, 25% had received radiotherapy alone. The endoscopic transsphenoidal approach to the clivus was almost uniquely used for surgical management. Survival data were available for 31 patients. Death had occurred at a mean of 9.4 months after the presentation of clivus metastasis. A strong correlation was found between the interval from primary cancer to the presentation of clivus metastasis and mortality.

CONCLUSIONS

Although an extremely rare occurrence, clivus metastasis should be considered in patients with a history of malignancy, in particular, prostate malignancy, presenting with new-onset isolated sixth nerve palsy.

Comparative analysis of the combined petrosal and the pretemporal transcavernous anterior petrosal approach to the petroclival region

OBJECTIVE

The combined petrosal (CP) approach has been traditionally used to resect petroclival meningioma (PCM). The pretemporal transcavernous anterior petrosal (PTAP) approach has emerged as an alternative. A quantitative comparison of both approaches has not been made. This anatomical study compared the surgical corridors afforded by both approaches and identified key elements of the approach selection process.

METHODS

Twelve cadaveric specimens were dissected, and 10 were used for morphometric analysis. Groups A and B (n = 5 in each) underwent the CP and PTAP approaches, respectively. The area of drilled clivus, lengths of cranial nerves (CNs) II-X, length of posterior circulation vessels, surgical area of exposure of the brainstem, and angles of attack anterior and posterior to a common target were measured and compared.

RESULTS

The area of drilled clivus was significantly greater in group A than group B (mean ± SD 88.7 ± 17.1 mm2 vs 48.4 ± 17.9 mm2, p < 0.01). Longer segments of ipsilateral CN IV (52.4 ± 2.33 mm vs 46.5 ± 3.71 mm, p < 0.02), CN IX, and CN X (9.91 ± 3.21 mm vs 0.00 ± 0.00 mm, p < 0.01) were exposed in group A than group B. Shorter portions of CN II (9.31 ± 1.28 mm vs 17.6 ± 6.89 mm, p < 0.02) and V1 (26.9 ± 4.62 mm vs 32.4 ± 1.93 mm, p < 0.03) were exposed in group A than group B. Longer segments of ipsilateral superior cerebellar artery (SCA) were exposed in group A than group B (36.0 ± 4.91 mm vs 25.8 ± 3.55 mm, p < 0.02), but there was less exposure of contralateral SCA (0.00 ± 0.00 mm vs 7.95 ± 3.33 mm, p < 0.01). There was no statistically significant difference between groups with regard to the combined area of the exposed cerebral peduncles and pons (p = 0.75). Although exposure of the medulla was limited, group A had significantly greater exposure of the medulla than group B (p < 0.01). Finally, group A had a smaller anterior angle of attack than group B (24.1° ± 5.62° vs 34.8° ± 7.51°, p < 0.03).

CONCLUSIONS

This is the first study to quantitatively identify the advantages and limitations of the CP and PTAP approaches from an anatomical perspective. Understanding these data will aid in designing maximally effective yet minimally invasive approaches to PCM.

Anterior cervical osteophytes causing dysphagia: Choice of the approach and surgical problems

Background

Anterior cervical osteophytes (ACOs) may rarely cause dysphagia, dysphonia, and dyspnea. Symptomatic ACOs are most commonly located between C3 and C7, whereas those at higher cervical (C1-C2) levels are rarer. We report a case series of 4 patients and discuss the best surgical approach according to the ostheophyte location and size, mainly for those located at C1-C2, and the related surgical problems.

Materials and Methods

Four patients (two males and two females) aged from 57 to 72 years were operated on for ACOs, causing variable dysphagia (and dyspnea with respiratory arrest in one). Three patients with osteophytes between C3 and C5 were approached through antero-lateral cervical approach, and one with a large osteophyte between C1 and C3-C4 level underwent a two-stage transcervical and transoral approach. All had significant postoperative improvement of dysphagia.

Results

The patient operated on though the transoral approach experienced postoperative flogosis of the prevertebral tissues and occipital muscles and thrombosis of the right jugular vein and transverse-sigmoid sinuses (Lemierre syndrome).

Conclusion

The transoral approach is the best surgical route to resect C1 and C2 ACOs, whereas the endoscopic endonasal approach is not indicated. The anterior transcervical approach is easier to resect osteophytes at C3, as well as those located below C3. A combined transoral and anterior cervical approach may be necessary for multilevel osteophytes.

Endoscopic Transnasal Odontoidectomy for Ventral Decompression of the Craniovertebral Junction: Surgical Technique and Clinical Outcome in a Case Series of 19 Patients

BACKGROUND

Abnormalities and pathologies of the craniovertebral junction as well as space-occupying lesions of the odontoid process can result in myelopathy symptoms. A staged procedure with posterior stabilization and anterior transnasal endoscopic decompression is recently considered a less invasive alternative to the transoral approach. We present a considerably large case series focused on the operative technique and the long-term neurological clinical outcome.

OBJECTIVE

To determine the safety and efficacy of odontoidectomy performed via an endoscopic transnasal approach.

METHODS

We retrospectively reviewed all patients treated in our neurosurgical department from January 2009 to January 2020. Demographics, pre- and postoperative clinical status, and operative technique and complications were extracted and analyzed.

RESULTS

In total, 22 transnasal operations were performed in 19 patients from January 2009 to January 2020. All but one patient underwent posterior C1-C2 instrumentation prior to the anterior transnasal computed tomography (CT)-navigated full-endoscopic decompression. The median duration of symptoms before surgery was 3 mo. Complications occurred in 1 patient who died from septic organ failure because of his initial diagnosis of osteomyelitis. Postoperative CT imaging showed sufficient decompression in 16 patients, and 3 patients underwent a transnasal endoscopic re-decompression (16%).

CONCLUSION

Transnasal endoscopic odontoidectomy presents a safe procedure with a satisfying clinical and radiological postoperative outcome.

The side door and front door to the upper retroclival region: a comparative analysis of the open pretemporal and the endoscopic endonasal transcavernous approaches

OBJECTIVE

The pretemporal transcavernous approach (PTA) and the endoscopic endonasal transcavernous approach (EETA) are both used to access the retroclival region. A direct quantitative comparison of both approaches has not been made. The authors compared the technical nuances of, and surgical exposure afforded by, each approach and identified the key elements of the approach selection process.

METHODS

Fourteen cadaveric specimens underwent either PTA (group A) or EETA with unilateral (group B) followed by bilateral (group C) interdural pituitary gland transposition. The percentage of drilled clivus; length of exposed oculomotor nerve (cranial nerve [CN] III), posterior cerebral artery (PCA), and superior cerebellar artery (SCA); and surgical area of exposure of both cerebral peduncles and the pons for the 3 groups were measured and compared.

RESULTS

Group A had a significantly lower percentage of drilled area than group B (mean [SD], 35.6% [11.2%] vs 91.3% [4.9%], p < 0.01). In group C, 100% of the upper third of the clivus was drilled in all specimens. Significantly longer segments of the ipsilateral PCA (p < 0.01) and SCA (p < 0.01) were exposed in group A than in group B. There was no significant difference in the length of the ipsilateral CN III exposed among the 3 groups. There was also no significant difference between group A and either group B or group C for the contralateral CN III or PCA exposure. However, longer segments of the contralateral SCA were exposed in group C than in group A (p = 0.02). Furthermore, longer segments of CN III (p < 0.01), PCA (p < 0.01), and SCA (p < 0.01) were exposed in group C than in group B. For brainstem exposure, there was greater exposure of the pons in group C than in group A (mean [SD], 211.4 [19.5] mm2 vs 157.7 [25.3] mm2, p < 0.01) and group B (211.4 [19.5] mm2 vs 153.9 [34.1] mm2, p < 0.01). However, significantly greater exposure of the ipsilateral peduncle was observed in group A (mean [SD], 125.6 [43.1] mm2) than in groups B and C (56.3 [6.0] mm2, p < 0.01). Group C had significantly greater exposure of the contralateral peduncle than group B (p = 0.02).

CONCLUSIONS

This study is the first to quantitatively identify the advantages and limitations of the PTA and EETA from an anatomical perspective. Understanding these data may help the skull base surgeon design a maximally effective yet minimally invasive approach to individual lesions.

Anterior release without odontoidectomy for irreducible atlantoaxial dislocation: transoral or endoscopic transnasal?

PURPOSE

To compare transoral and endoscopic transnasal anterior release without odontoidectomy and posterior reduction and fixation to treat irreducible atlantoaxial dislocation (IAAD).

METHODS

From June 2006 to January 2017, 35 consecutive patients with IAAD underwent transoral (Tr-Oral group) or endoscopic transnasal (Tr-Nasal group) release and posterior fixation and fusion in our department. Clinical neurological recovery (Japanese Orthopedic Association (JOA) score) and radiological reduction parameters including atlantodontoid interval (ADI), space available for the cord (SAC) and cervicomedullary angle (CMA) were analyzed and compared. The operation duration, blood loss, length of intensive care unit (ICU)/hospital stay and complications were recorded.

RESULTS

All 35 patients (18 and 17 patients in the Tr-Oral and Tr-Nasal groups, respectively) were followed up for a mean of 36.4 months (range, 21-60 months). All patients achieved excellent anatomical reduction and clinical neurological recovery, with no significant differences between the two groups. The JOA score, ADI, SAC and CMA were not significantly different between the two groups at various postoperative points. Although the Tr-Oral group had shorter operation time and less blood loss than the Tr-Nasal group, the Tr-Nasal group tended to have a significantly shorter hospital/ICU stay, earlier extubation and earlier oral intake than the Tr-Oral group.

CONCLUSION

The transoral and endoscopic transnasal approaches can achieve equivalent release and reduction effects when treating IAAD. Compared to the transoral approach, the endoscopic transnasal route is less invasive with earlier extubation and oral intake, shorter hospital/ICU stays and lower medical costs, which is conducive to enhanced recovery after surgery.

Overview of Minimally Invasive Spine Surgery

Minimally invasive spine surgery (MISS) has continued to evolve over the past few decades, with significant advancements in technology and technical skills. From endonasal cervical approaches to extreme lateral lumbar interbody fusions, MISS has showcased its usefulness across all practice areas of the spine, with unique points of access to avoid pertinent neurovascular structures. Adult spine deformity has also recognized the importance of minimally invasive techniques in its ability to limit complications and to provide adequate sagittal alignment correction and improvements in patients' functional status. Although MISS has continued to make significant progress clinically, consideration must also be given to its economic impact and the learning curve surgeons experience in adding these procedures to their armamentarium. This review examines current innovations in MISS, as well as the economic impact and future directions of the field.

Clinical Outcomes of Endoscopic Endonasal Odontoidectomy: A Single-Center Experience

BACKGROUND

Odontoidectomy for basilar invagination and craniovertebral junction pathology traditionally has been performed using a transoral route. However, the endoscopic endonasal approach to the anterior craniovertebral junction may offer safer and more effective access when compared with transoral approaches. The objective of this study is to review the surgical outcomes and complications associated with endoscopic endonasal odontoidectomy.

METHODS

This study is a retrospective chart review of all adult patients who underwent an endoscopic endonasal odontoidectomy at a single tertiary care center between January 2011 and May 2019.

RESULTS

Seventeen patients who underwent endoscopic endonasal odontoidectomy were included. The median age at admission was 67 years (range: 33-84 years) and 65% of the patients were female. One patient (1/17, 6%) had vertebral artery injury, which had to be coiled with no neurologic deficits, and 4 patients (4/17, 24%) had intraoperative CSF leaks with no postoperative leak. Fourteen (14/17, 82%) patients were extubated by postoperative day 1. Three patients (3/17, 18%) developed postoperative sinus infections and required antibiotics. Eight patients (8/17, 47%) developed transient postoperative dysphagia. One patient (1/17, 6%) had postoperative epistaxis and 1 patient (1/17, 6%) had postoperative lower cranial nerve symptoms. The median length of hospital stay was 13 days (range: 2-44 days).

CONCLUSIONS

Although the transoral approach has been the traditional route for anterior decompression of the craniovertebral junction, endoscopic endonasal odontoidectomy is a feasible and well-tolerated procedure associated with satisfactory patient outcomes and low morbidity.

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 Fascial Layers Attached to the Skull Base: A Cadaveric Study

OBJECTIVE

A profound understanding of the relationship between the deep cervical fasciae and the skull base is essential for skull base surgery. To our knowledge, there has been little research on the relationship between the deep cervical fasciae and inferior surface of the skull base; thus, this study aims to examine the fascial network of the skull base.

METHODS

Two cadaveric heads are dissected to reveal the fascial network of the skull base and 19 sides of cadaveric heads were used to reveal an anatomical variant of the pterygospinous and pterygoalar ligaments/muscles.

RESULTS

The interpterygoid fascia is attached to the skull base along the sphenopetrosal fissure and tympanosquamous suture. The tensor vascular styloid fascia extends from the inferior border of the tensor veli palatini and covers the tympanic bone and styloid apparatus laterally. The pharyngobasilar fascia attaches to the pharyngeal tubercle on the inferior surface of the basilar part of the occipital bone and petro-occipital synchondrosis. In the middle of the clivus, we found thick fibrocartilaginous tissue and the prevertebral fascia fused to this area. Fascia of the longus capitis, the tensor-vascular styloid fascia, and stylopharyngeal fascia extend laterally and form the complex fascial network around the internal jugular vein and the internal carotid artery. The carotid sheath attaches anteriorly to the vaginal process and posteriorly to the fibrocartilaginous tissue around the jugular foramen and carotid canal.

CONCLUSIONS

This study comprehensively exposes the fascial network of the skull base. Our cadaveric dissection findings support those from previous imaging-anatomical studies. Precise knowledge of these fascial layers is essential for accurate diagnosis and understanding the spread of disease, as well as helping skull base surgeons safely perform challenging procedures.

Endonasal and Transoral Approaches to the Craniovertebral Junction: A Quantitative Anatomical Study

BACKGROUND

The endoscopic endonasal approach has recently been added to the surgical armamentarium to access the anterior craniovertebral junction (CVJ). Comparative analyses with the transoral approach are scarce. The aim of this study was to provide a quantitative anatomical analysis of both approaches.

METHODS

In four specimens the endoscopic endonasal approach (before and after sphenoidectomy) and the transoral approach (without and with a soft palate split) were performed. ApproachViewer-part of GTx-UHN (Guided Therapeutics software, developed at University Health Network, Toronto, ON, Canada)-was used to quantify and visualize the working volume, as well as the exposed area, of each surgical approach. Different modalities (crossing and non-crossing) were used to quantify the exposure of the deep surface, providing an indirect quantitative value of the 'surgical freedom'. The lowest point exposed by the endonasal approaches was compared with that predicted by preoperative radiological lines. Non-parametric Welch analysis of variance (ANOVA) was used for statistical analyses.

RESULTS

The working volume was significantly larger and the distance to the target was shorter with the transoral approaches than with the endonasal approaches. Clival exposure was better with the endonasal approaches than with the non-crossing transoral approach without a soft palate split; areas below C1 were better exposed with the transoral routes. The nasoaxial line best predicted surgical exposure with the endonasal approaches.

CONCLUSION

Endoscopic endonasal and transoral approaches to the anterior CVJ provide optimal exposure of different areas that overlap at the level of C1 when no anatomical anomalies are present. A split of the soft palate is not necessary during the transoral approach if it is combined with an endoscopic endonasal approach.

Endoscopic Endonasal Approaches for Treatment of Craniovertebral Junction Tumours

Tumours involving the craniovertebral junction (CVJ) are challenging because of their local invasiveness and high recurrence rates, as well as their proximity to critical neurovascular structures and the difficulty of reconstructing the resulting skull base defect at this site. Several surgical techniques are currently available to access these lesions, including the far lateral, extreme lateral, direct lateral, transcervical, transoral and transnasal approaches. In this paper, application of the endoscopic endonasal approach (EEA) in the treatment of CVJ tumours is analysed. The indications, contraindications, preoperative workup, step-by-step surgical technique, skull base reconstruction options and postoperative management are described. The advantages and limitations of the EEA are also discussed. Finally, a systematic review of the literature is provided to elucidate the levels of evidence supporting the use of the EEA in this field. Employment of this approach to the CVJ has contributed to high success rates in achieving gross total resection of tumours and improvement in neurological symptoms. Intraoperative and postoperative complication rates are acceptable, with cerebrospinal fluid leakage being the major concern (with a 17-25% incidence). Moreover, in comparison with traditional approaches to the CVJ, the EEA provides lower rates of postoperative dysphagia and respiratory complications. Use of the EEA for treatment of CVJ tumours appears to be a rational alternative to the conventional transoral, transcranial and transcervical approaches in selected cases. Multidisciplinary teamwork including different specialists-such as medical and radiation oncologists, radiologists, otorhinolaryngologists and neurosurgeons-is strongly recommended for the purpose of offering the best treatment strategy for the patient.

The full-endoscopic uniportal technique for decompression of the anterior craniocervical junction using the retropharyngeal approach: an anatomical feasibility study in human cadavers and review of the literature

Objective

Acute or progressive myelopathy may necessitate direct anterior decompression of the craniocervical junction and odontoidectomy. Different techniques with individual advantages and disadvantages can be used. In addition to the gold standard-the transoral approach-there is also increasing experience with the endoscopic transnasal technique. Other alternative methods are also being developed to reduce technical and perioperative problems. The aim of this anatomical study was to investigate the feasibility of the full-endoscopic uniportal technique with a retropharyngeal approach for decompression of the craniocervical junction, taking into consideration the specific advantages and disadvantages compared with conventional methods and the currently available data in the literature.

Methods

Five fresh adult cadavers were operated on. The endoscope used has a shaft cross-section of 6.9 × 5.9 mm and a 25° viewing angle. It contains an eccentric intraendoscopic working channel with a diameter of 4.1 mm. An anterior retropharyngeal approach was used. The anatomical structures of the anterior craniocervical junction were dissected and the bulbomedullary junction was decompressed.

Results

The planned steps of the operation were performed in all cadavers. The retropharyngeal approach allowed the target region to be accessed easily. The anatomical structures of the anterior craniocervical junction could be identified and dissected. The bulbomedullary junction could be adequately decompressed. No resections of the anterior arch of the atlas were necessary in the odontoidectomy.

Conclusions

Using the full-endoscopic uniportal technique with an anterior retropharyngeal approach, the craniocervical region can be adequately reached, dissected, and decompressed. This is a minimally invasive technique with the known advantages of an endoscopic procedure under continuous irrigation. The retropharyngeal approach allows direct, sterile access. The instruments are available for clinical use and have been established for years in other operations of the entire spine.

Full-endoscopic uniportal retropharyngeal odontoidectomy for anterior craniocervical infection

BACKGROUND

Infections of the anterior craniocervical junction may require surgery. There are various techniques with individual advantages and disadvantages. This study evaluates the full-endoscopic uniportal technique via the anterior retropharyngeal approach for odontoidectomy, decompression, and debridement.

MATERIAL AND METHODS

Three patients with an infection of the anterior craniocervical junction with retrodental involvement were operated on between 2014 and 2016 using the full-endoscopic uniportal technique. Posterior stabilization was also performed with the same procedure for all patients.

RESULTS

The operation was technically satisfactory in all cases. No problems due to swelling of the pharyngeal soft tissue occurred. No other complications were observed. All patients had a satisfactory outcome with stable regression of the myelopathy symptoms and/or complete healing of the infection. The follow-up images showed sufficient decompression of bone and soft tissues in all cases.

CONCLUSIONS

The full-endoscopic uniportal technique with an anterior retropharyngeal approach can be an adequate and minimally invasive surgical technique for odontoidectomy, decompression, and debridement in infections of the craniocervical junction and can reduce access-related problems. The transoral, transnasal, and retropharyngeal approaches have different surgical fields due to the access trajectories, which must be taken into consideration depending on the anatomy and pathology when selecting a suitable technique.

Full-endoscopic Uniportal Odontoidectomy and Decompression of the Anterior Cervicomedullary Junction Using the Retropharyngeal Approach

STUDY DESIGN

A study of a series of consecutive full-endoscopic uniportal decompressions of the anterior craniocervical junction with retropharyngeal approach.

OBJECTIVE

The aim of this study was to evaluate the direct anterior decompression of the craniocervical junction in patients with bulbomedullary compression using a full-endoscopic uniportal technique via an anterolateral retropharyngeal approach.

SUMMARY OF BACKGROUND DATA

Acute or progressive myelopathy may necessitate direct anterior decompression of the craniocervical junction and odontoidectomy. Different techniques with individual advantages and disadvantages can be used. In addition to the gold standard - the transoral approach - there is increasing experience with the endoscopic transnasal technique. Other alternative procedures are also being developed.

METHODS

Between 2013 and 2016, eight patients with basilar impression, retrodental pannus, or retrodental infection were operated in the full-endoscopic uniportal technique with a retropharyngeal approach. Anterior decompression of the bulbomedullary junction with odontoidectomy was performed. All patients additionally underwent posterior stabilization. Imaging and clinical data were collected in follow-up examinations for 1 year.

RESULTS

The bulbomedullary junction was adequately decompressed. No problems due to swelling of pharyngeal soft tissue occurred. One patient required revision due to secondary bleeding. No other complications were observed. All patients had a good clinical outcome with stable regression of the myelopathy symptoms and/or healing of the infection. The imaging follow-up showed sufficient decompression of bone and soft tissue in all cases. No evidence was found of increasing instability or failure of posterior fusion.

CONCLUSION

In the operated patients, the full-endoscopic uniportal surgical technique with anterior retropharyngeal approach was found to be a sufficient and minimally invasive method with the known advantages of an endoscopic procedure under continuous irrigation. It should not be viewed only as competition for other surgical techniques - due to its individual technical parameters, it can also be considered to be an alternative or complementary procedure.

LEVEL OF EVIDENCE

4.

Quality of Life After Combined Endonasal Endoscopic Odontoidectomy and Posterior Suboccipital Decompression and Fusion

BACKGROUND

Basilar invagination can result from systemic diseases that can weaken structural integrity of the craniocervical junction. Definitive treatment often requires ventral decompression and posterior decompression and fusion. Endonasal odontoidectomy is a relatively new minimal access procedure; quality of life (QOL) after this procedure has not been reported.

METHODS

We reviewed a consecutive database of endonasal odontoidectomy cases and identified patients having posterior decompression and fusion. Two QOL questionnaires were administered postoperatively: Sino-Nasal Outcome Test and 36-Item Short Form Survey. Comparisons with other endonasal or Chiari procedures were performed.

RESULTS

The study comprised 14 patients; 79% had Chiari malformation in addition to basilar invagination. Mean follow-up was 17.2 months. Symptomatic improvement occurred in 78.6% after surgery. Average postoperative Sino-Nasal Outcome Test scores were 39.2 ± 17.93, with worst scores in areas related to fatigue and sleep patterns but not nasal function. 36-Item Short Form Survey scores were lower in areas of physical function and general health but better for emotional health and pain. Compared with patients undergoing Chiari malformation surgery without endonasal odontoid resection or fusion, patients undergoing odontoidectomy had higher QOL in areas of role emotional, emotional well-being, and pain but worse QOL in general health and role physical.

CONCLUSIONS

Patients undergoing posterior decompression and fusion with endonasal odontoidectomy do well after surgery with respect to nasal function and emotional health. Patients who also have severe basilar invagination associated with systemic diseases demonstrate reduced QOL after surgery in areas of physical function and sleep leading to fatigue, irritability, and concentration difficulty, likely related to their systemic disease.

Primary solitary retro-clival amyloidoma

BACKGROUND

Amyloidosis encompasses a group of disorders sharing the common feature of intercellular deposition of amyloid protein by several different pathogenetic mechanisms. Primary solitary amyloidosis, or amyloidoma, is a rare subset of amyloidosis in which amyloid deposition is focal and not secondary to a systemic process or plasma cell dyscrasia.

CASE DESCRIPTION

This 84-year-old female presented with history of multiple syncopal episodes, dysphagia, and ataxia. Motor strength was 3+/5 in the right upper extremity. Rheumatoid factor, cyclic citrullinated peptide (CCP), and anti-nuclear antibody (ANA) were normal. Serum and urine immune-electrophoresis detected no abnormal bands. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a non-enhancing soft-tissue mass extending from the retro-clivus to C2 posteriorly, eccentric to the right with severe mass effect on the upper cervical medullary junction. Endoscopic trans-nasal debulking of the retro-clival mass was performed with occiput to C5 posterior instrumentation for spinal stabilization.

CONCLUSIONS

Primary solitary amyloidosis, unlike other forms of amyloidosis, has an excellent prognosis with local resection. Diagnosis requires special stains and a degree of suspicion for the disease. This is the first report to document an endoscopic trans-nasal approach for removal of a primary solitary amyloidosis of the retro-clivus. Management of vertebral amyloidoma involves aggressive local resection of the tumor when feasible and spine stabilization as the degree of tumor involvement mandates. Complete evaluation for the diagnosis of systemic amyloidosis is essential for the management and prognostication. Surgeons encountering such lesions must maintain high suspicion for this rare disease and advise pathologists accordingly to establish the correct diagnosis.

Walk the Line. The Surgical Highways to the Craniovertebral Junction in Endoscopic Approaches: A Historical Perspective

BACKGROUND

We compiled a comprehensive literature review on the anatomic and clinical results of endoscopic approaches to the craniocervical junction (CVJ) to better contribute to identify the best strategy.

METHODS

An updated literature review was performed in the PubMed, OVID, and Google Scholar medical databases, using the terms "Craniovertebral junction," "Transoral approach," "Transnasal approach," "Transcervical approach," "Endoscopic endonasal approach," "Endoscopic transoral approach," "Endoscopic transcervical approach." Clinical series, anatomic studies, and comparative studies were reviewed.

RESULTS

Pure endonasal and cervical endoscopic approaches still have some disadvantages, including the learning curve and the deeper surgical field. Endoscopically assisted transoral surgery with 30° endoscopes represents an emerging option to standard microsurgical techniques for transoral approaches to the anterior CVJ. This approach should be considered as complementary rather than an alternative to the traditional microsurgical transoral-transpharyngeal approach.

CONCLUSIONS

The transoral approach with sparing of the soft palate still remains the gold standard compared with the pure transnasal and transcervical approaches because of the wider working channel provided by the former technique. The transnasal endoscopic approach alone appears to be superior when the CVJ lesion exceeds the upper limit of the inferior third of the clivus.

How I do it: Endoscopic endonasal approach for odontoid resection

BACKGROUND

Since it was first described in 2005 by Kassam et al., the technique of endoscopic resection of the odontoid by the transnasal route has gained broad acceptance. Its advantages over the transoral approach are currently well-demonstrated.

METHOD

The authors present the surgical technique developed by the senior author in a series of 12 patients, specifying the planning, complications avoidance and showing a film of the operating technique.

CONCLUSION

Endoscopic endonasal odontoidectomy is an effective procedure with low morbidity. This technique has a place in the treatment of complex pathologies of the craniovertebral junction and has many advantages over the transoral route.

Cerebrospinal fluid leakage after turbinate submucosal diathermy: an unusual complication

Submucosal diathermy of the inferior turbinate (SMDIT) is a generally safe procedure to control inferior turbinate hypertrophy. We present a case of a cerebrospinal fluid (CSF) leak at the craniocervical junction after SMDIT done in another institution. A 27-year-old man presented 3 weeks after undergoing SMDIT with signs and symptoms of meningitis and postnasal rhinorrhea. Nasal endoscopy and imaging revealed a nasopharyngeal CSF fistula at the craniocervical junction. Transnasal endoscopic repair and reconstruction was performed with no recurrence on repeat imaging and clinical follow up. We describe the first reported case in the literature of an iatrogenic CSF fistula caused by SMDIT, an unusual and potentially fatal complication, and its surgical management.

SIMILAR CASES PUBLISHED

0

CONFLICT OF INTEREST

None.

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.

Microsurgical anatomy and approaches around the lateral recess with special reference to entry into the pons

OBJECTIVE The lateral recess is a unique structure communicating between the ventricle and cistern, which is exposed when treating lesions involving the fourth ventricle and the brainstem with surgical approaches such as the transcerebellomedullary fissure approach. In this study, the authors examined the microsurgical anatomy around the lateral recess, including the fiber tracts, and analyzed their findings with respect to surgical exposure of the lateral recess and entry into the lower pons. METHODS Ten cadaveric heads were examined with microsurgical techniques, and 2 heads were examined with fiber dissection to clarify the anatomy between the lateral recess and adjacent structures. The lateral and medial routes directed to the lateral recess in the transcerebellomedullary fissure approach were demonstrated. A morphometric study was conducted in the 10 cadaveric heads (20 sides). RESULTS The lateral recess was classified into medullary and cisternal segments. The medial and lateral routes in the transcerebellomedullary fissure approach provided access to approximately 140º-150º of the posteroinferior circumference of the lateral recess. The floccular peduncle ran rostral to the lateral recess, and this region was considered to be a potential safe entry zone to the lower pons. By appropriately selecting either route, medial-to-lateral or lateral-to-medial entry axis is possible, and combining both routes provided wide exposure of the lower pons around the lateral recess. CONCLUSIONS The medial and lateral routes of the transcerebellomedullary fissure approach provided wide exposure of the lateral recess, and incision around the floccular peduncle is a potential new safe entry zone to the lower pons.

Direct and Oblique Approaches to the Craniovertebral Junction: Nuances of Microsurgical and Endoscope-Assisted Techniques Along with a Review of the Literature

PURPOSE

The aim of this review is to provide an update of the technical nuances of microsurgical and endoscopic-assisted approaches to the craniovertebral junction (transnasal, transoral, and transcervical), and to report on the available clinical results in order to identify the best strategy.

METHODS

A nonsystematic update of the reviews and reporting on the anatomical and clinical results of endoscopic-assisted and microsurgical approaches to the craniovertebral junction (CVJ) was performed.

RESULTS

Pure endonasal and cervical endoscopic approaches still have some disadvantages, including their steep learning curves and their deeper surgical fields. Endoscopically assisted transoral surgery with 30° endoscopes represents an emerging option compared with standard microsurgical techniques for transoral approaches to the anterior CVJ. This approach should be considered as complementary to, rather than as an alternative to the traditional transoral-transpharyngeal approach.

CONCLUSIONS

The transoral (microsurgical or video-assisted) approach with sparing of the soft palate still remains the gold standard compared with the "pure" transnasal and transcervical approaches, due to the wider working channel provided by the former technique. The transnasal endoscopic approach alone appears to be superior when the CVJ lesion exceeds the upper limit of the inferior third of the clivus. Of particular interest is the evidence that advances in reduction techniques can avoid the ventral approach.

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.

Morphological and Morphometric Analysis of Foramen Magnum: An Anatomical Aspect

OBJECTIVE

To investigate the detailed morphological and morphometric analysis of foramen magnum (FM) in dry cranii.

METHODS

One hundred fifty skulls of unidentified sex were macroscopically examined and were photographed with Canon 400B (55 mm objective). According to tooth eruption of the skulls, they were accepted as adults. None of the examined skulls showed signs of prior cranial surgery, malformation, or trauma. The evaluated study parameters that were recorded with Vernier caliper in millimeter were as follows: antero-posterior diameter from Basion to Opisthion, transverse diameter (largest distance between the lateral margins of the FM), and the shape of the FM (Fig. 1). The shape of the FM was determined according to FM index that was calculated by dividing antero-posterior diameter by transverse diameter. When FM index was found greater than or equal to 1.2, the foramen was accepted to be oval in shape. Whereas the FM index was found less than 1.2, the foramen was accepted to be round in shape The area of the FM was calculated by using 2 different formulas as described previously by Radinsky (/4 × π × w × h) and Teixeira (π × {(h + w)/4}2), and "π" was accepted as 3.14 in both formulas.

RESULTS

The results of descriptive statistics and areas of the FMs were presented in Table 1. The mean antero-posterior diameter and transverse diameter of anteroposterior diameter by transverse diameters were found as 34.38 ± 2.38 and 28.95 ± 2.19, respectively. The mean area of the FMs estimated by Teixeria formula was determined significantly larger than the mean area of the FMs estimated by Radinsky formula (P <0.001). According to estimated FM index of the 150 adult dry skulls, 87 (58%) of skulls were described as being round in shape and 63 (42%) of skulls were described as being oval in shape (Fig. 1).

CONCLUSION

The surgeons must comprehend regarding the detailed morphological and morphometric features of FM to avoid vital complications during the surgical procedures.

Endoscopic approach to the upper cervical spine and clivus: an anatomical study of the upper limits of the transoral corridor

BACKGROUND

Recent advances in endoscopic techniques have allowed minimally invasive approaches to the cranio-vertebral junction (CVJ) through the oropharynx (ETA) in addition to the transnasal approach (EEA). These minimally invasive endoscopic techniques allow for increased surgical exposure using no visible incisions, with a potential less morbidity. The ability to know preoperatively the limit of the ETA is vital for the surgical planning in order to better address CVJ pathology. The aim of the present study is to determine the anatomical limits of endoscopic dissection of the skull base and upper cervical spine through the transoral corridor and the superior limit reached by adopting this approach.

METHODS

Six fresh-frozen adult cadaver heads were dissected adopting ETA preserving the hard and soft palate. The most superior extent of the exposure was dissected. Post-operative CT scans were performed to confirm the superior extent.

RESULTS

The superior most limit of dissection corresponded to the sphenoid-occipital junction, where the basilar portion of the occipital bone joins with the sphenoid bone's body. This ranged from 12.7 to 18.9 mm above the line of the hard palate. This was achieved without having to transgress any of the palatine structures.

CONCLUSIONS

The sphenoid-occipital junction represents the rostral limit of endoscopic transoral approach to the lower skull base and CVJ area. This approach is limited superiorly by the orientation of the hard palate and mouth aperture and lower dentition due to the linear nature of the endoscope. Using the endoscope for this approach can allow for a more superior exposure than the traditional open transoral approach.

Transnasal Endoscopic Biopsy Approach to Atlas Tumor with X-ray Assisted and Related Radiographic Measure

OBJECTIVE

To develop an endoscopic transnasal approach to atlas tumors and study its practicability.

METHODS

This article comprises two components: an illustrative case report and observational data on 50 volunteers. As to the case report, a 34 year old man presented with occipital pain for more than 3 months and underwent systematic investigation in Qilu Hospital of Shandong University. CT and MRI scans showed bony destruction in the craniovertebral junction (CVJ) suggestive of tumor. Via an endoscopic transnasal approach to the suspected atlas tumor through the inferior nasal meatus, a Gallini biopsy needle was used to obtain tissue for examination. The procedure was performed endoscopically with double orientation X-ray guidance and coaxial technology after establishing the shortest distance for the biopsy track and range of target tissue and was assisted by manual palpation. As to the observational data, 50 volunteers underwent atlas-related morphometric image measurement using gemstone CT equipment. Biopsy track angles, range for biopsy of the atlas and biopsy track distances were measured by a blinded operator on CT images.

RESULTS

CASE REPORT

pathological examination of the biopsy resulted in diagnosis of a chordoma. There were no complications such as bleeding, infection or spinal cord injury. One month later, the patient underwent tumor resection and reconstruction in other hospital and the diagnosis of chordoma was confirmed by pathological examination of the resected specimen. Observational data: measurements obtained from CT scans of the 50 volunteers were as follows. Biopsy track angles: mean leaning inside angle 3.53° ± 0.39° and mean posterior slope angle 13.05° ± 1.39°. Range for atlas biopsy: transverse diameter 11.84 ± 1.24 mm and longitudinal diameter 9.67 ± 0.90 mm. Biopsy track distances: from atlas to nostril, and to anterior and posterior edges of the inferior turbinate mucosa were 94.52 ± 5.03 mm, 78.21 ± 4.63 mm, and 33.51 ± 3.13 mm, respectively.

CONCLUSIONS

An endoscopic transnasal approach enables biopsy and diagnosis of tumors in the anterior arch of the atlas. Relevant measurements were obtained by assessing CT scans of 50 volunteers to assist operators to determine the effective and safe range for transnasal atlas biopsy.

Use of Frameless Stereotactic Neuronavigation and O-arm for Transoral Transpalatal Odontoidectomy to Treat a Very High Basilar Invagination

Frameless stereotactic neuronavigation system has been in wide use since many years for precise localization of cranial tumors and navigation for spinal instrumentation. We present its usage in the localization of odontoid process in a very high basilar invagination for a transoral transpalatal resection of the same. We discuss the technical aspects of assembly of neuronavigation system, O-arm and Mayfield head frame on Allen spine system to achieve precise and accurate localization of high riding odontoid process through an extremely narrow operative corridor.

Experimental Endoscopic Angular Domains of Transnasal and Transoral Routes to the Craniovertebral Junction: Light and Shade

STUDY DESIGN

We investigate on the surgical reliability of nasal palatine line for the transnasal approach and introduce a conceptually analogue radiological line as a reliable predictor of the maximal superior extension of the transoral approach. We have also compared radiological and surgical lines to find possible radiological references points to predict preoperatively the maximal extent of superior dissection for the transoral approach.

OBJECTIVE

After comparing the surgical exposition angle and the working channel volume of both the approaches in our previous article, now we compare the radiological (theoretical) with the "surgical" (effective) Nasopalatine line and the latter with the recently introduced Nasal Axial Line. We conceived a radiological line with a similar significance for the transoral approach and we called it Mandibulopalatine line; then we compared the radiological with the "surgical" one.

SUMMARY OF BACKGROUND DATA

Endoscopy represents both an alternative and a useful complement to the standard microsurgical approach to the anterior craniovertebral junction (CVJ). Both the surgical routes have a limitation caused by the hard palate.

METHODS

Ten fresh nonperfused cadavers were studied. Transnasal and transoral linear and angled exposure of the CVJ were evaluated by means of X-ray and CT scan in the sagittal plane.

RESULTS

The angular difference between the radiological and surgical transoral endoscopic lines was significantly smaller compared with the difference between the radiological and surgical transnasal lines. Finally we found how to calculate preoperatively the "surgical" (effective) Mandibulopalatine line by a simple lateral preoperative radiological study of the CVJ.

CONCLUSION

Naso-axial line is confirmed to be a reliable preoperative predictor of the maximal extent of inferior dissection for transnasal approach. Surgical Palatine Inferior dental Arch line will draw the maximal extent of superior dissection for the transoral approach with simple lateral head X-ray examination by open mouth.

LEVEL OF EVIDENCE

3.

The endoscopic transoral approach to the craniovertebral junction: an anatomical study with a clinical example

OBJECTIVE

The microscopic transoral, endoscopic transnasal, and endoscopic transoral approaches are used alone and in combination for a variety of craniovertebral junction (CVJ) pathologies. The endoscopic transoral approach provides a more direct exposure that is not restricted by the nasal cavity, pterygoid plates, and palate while sparing the potential morbidities associated with extensive soft-tissue dissection, palatal splitting, or mandibulotomy. Concerns regarding the extent of visualization afforded by the endoscopic transoral approach may be limiting its widespread adoption.

METHODS

A dissection of 10 cadaver heads was undertaken. CT-based imaging guidance was used to measure the working corridor of the endoscopic transoral approach. Measurements were made relative to the palatal line. The built-in linear measurement tool was used to measure the superior and inferior extents of view. The superolateral extent was measured relative to the midline, as defined by the nasal process of the maxilla. The height of the clivus, odontoid tip, and superior aspect of the C-1 arch were also measured relative to the palatal line. A correlated clinical case is presented with video.

RESULTS

The CVJ was accessible in all cases. The superior extent of the approach was a mean 19.08 mm above the palatal line (range 11.1–27.7 mm). The superolateral extent relative to the midline was 15.45 mm on the right side (range 9.6–23.7 mm) and 16.70 mm on the left side (range 8.1–26.7 mm). The inferior extent was a mean 34.58 mm below the palatal line (range 22.2–41.6 mm). The mean distances were as follows: palatal line relative to the odontoid tip, 0.97 mm (range −4.9 to 3.7 mm); palatal line relative to the height of the clivus, 4.88 mm (range −1.5 to 7.3 mm); and palatal line relative to the C-1 arch, −2.75 mm (range −5.8 to 0 mm).

CONCLUSIONS

The endoscopic transoral approach can reliably access the CVJ. This approach avoids the dissections and morbidities associated with a palate-splitting technique (velopharyngeal insufficiency) and the expanded endonasal approach (mucus crusting, sinusitis, and potential lacerum or cavernous-paraclival internal carotid artery injury). For appropriately selected lesions near the palatal line, the endoscopic transoral approach appears to be the preferred approach.

Quantification and comparison of neurosurgical approaches in the preclinical setting: literature review

There is a growing awareness of the need for evidence-based surgery and of the issues that are specific to research in surgery. Well-conducted anatomical studies can represent the first, preclinical step for evidence-based surgical innovation and evaluation. In the last two decades, various reports have quantified and compared neurosurgical approaches in the anatomy laboratory using different methods and technology. The aim of this study was to critically review these papers. A PubMed and Scopus search was performed to select articles that quantified and compared different neurosurgical approaches in the preclinical setting. The basic characteristics that anatomically define a surgical approach were defined. Each study was analyzed for measured features and quantification method and technique. Ninety-nine papers, published from 1990 to 2013, were included in this review. A heterogeneous use of terms to define the features of a surgical approach was evident. Different methods to study these features have been reported; they are generally based on quantification of distances, angles, and areas. Measuring tools have evolved from the simple ruler to frameless stereotactic devices. The reported methods have each specific advantages and limits; a common limitation is the lack of 3D visualization and surgical volume quantification. There is a need for a uniform nomenclature in anatomical studies. Frameless stereotactic devices provide a powerful tool for anatomical studies. Volume quantification and 3D visualization of the surgical approach is not provided with most available methods.

Craniovertebral junction 360°: A combined microscopic and endoscopic anatomical study

Objectives:

Craniovertebral junction (CVJ) can be approached from various corridors depending on the location and extent of disease. A three-dimensional understanding of anatomy of CVJ is paramount for safe surgery in this region. Aim of this cadaveric study is to elucidate combined microscopic and endoscopic anatomy of critical neurovascular structures in this area in relation to bony and muscular landmarks.

Materials and Methods:

Eight fresh-frozen cadaveric heads injected with color silicon were used for this study. A stepwise dissection was done from anterior, posterior, and lateral sides with reference to bony and muscular landmarks. Anterior approach was done endonasal endoscopically. Posterior and lateral approaches were done with a microscope. In two specimens, both anterior and posterior approaches were done to delineate the course of vertebral artery and lower cranial nerves from ventral and dorsal aspects.

Results:

CVJ can be accessed through three corridors, namely, anterior, posterior, and lateral. Access to clivus, foreman magnum, occipital cervical joint, odontoid, and atlantoaxial joint was studied anteriorly with an endoscope. Superior and inferior clival lines, supracondylar groove, hypoglossal canal, arch of atlas and body of axis, and occipitocervical joint act as useful bony landmarks whereas longus capitis and rectus capitis anterior are related muscles to this approach. In posterior approach, spinous process of axis, arch of atlas, C2 ganglion, and transverse process of atlas and axis are bony landmarks. Rectus capitis posterior major, superior oblique, inferior oblique, and rectus capitis lateralis (RCLa) are muscles related to this approach. Occipital condyles, transverse process of atlas, and jugular tubercle are main bony landmarks in lateral corridor whereas RCLa and posterior belly of digastric muscle are the main muscular landmarks.

Conclusion:

With advances in endoscopic and microscopic techniques, access to lesions and bony anomalies around CVJ is becoming easier and straightforward. A combination of microscopic and endoscopic techniques is more useful to understand this anatomy and may aid in the development of future combined approaches.

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.

Videoassisted anterior surgical approaches to the craniocervical junction: rationale and clinical results

PURPOSE

In this narrative review, we aim to give an update on the anatomic fundamentals of endoscopic assisted surgery to the craniocervical junction (transnasal, transoral and transcervical), and to report on the available clinical results.

METHODS

A non-systematic review and reporting on the anatomical and clinical results of endoscopic assisted approaches to the craniocervical junction (CVJ) is performed.

RESULTS

Pure endonasal and cervical endoscopic approaches still have some disadvantages, including the learning curve and the lack of 3-dimensional perception of the surgical field. Endoscopically assisted transoral surgery with 30° endoscopes represents an emerging alternative to standard microsurgical techniques for transoral approaches to the anterior CVJ. Used in conjunction with traditional microsurgery and intraoperative fluoroscopy, it provides a safe and improved method for anterior decompression with or without a reduced need for extensive soft palate splitting, hard palate resection, or extended maxillotomy.

CONCLUSIONS

Transoral (microsurgical or video-assisted) approach with sparing of the soft palate still remains the gold standard compared to the "pure" transnasal and transcervical approaches due to the wider working channel provided by the former technique. Transnasal endoscopic approach alone appears to be superior when the CVJ lesion exceeds the upper limit of the inferior third of the clivus. Combined transnasal and transoral procedures can be tailored according to the specific pathological and radiological findings.

Combined endoscopic transnasal and transoral approach for extensive upper cervical osteoradionecrosis

PURPOSE

Osteoradionecrosis (ORN) is a rare yet well-recognized complication following radiotherapy to the head and neck. We illustrate the only case of a spontaneous extrusion of the sequestered C1 arch through the oral cavity and discuss our experience with a combined endoscopic transnasal and transoral approach for cervical ORN.

METHODS

A 56-year-old female presented with a 3-month history of blood-stained nasal discharge. She had been treated with radiotherapy for nasopharyngeal carcinoma 25 years earlier. Flexible nasal endoscopy demonstrated an exposed bone with an edematous posterior nasopharyngeal mass. Computed tomography showed a pre-vertebral mass with destruction of C1 and C2. She underwent occipito-cervical fusion followed by a combined transnasal and transoral endoscopic debridement of non-viable bone in the same perioperative setting. Healing of the raw mucosa was by secondary intention and reconstruction was not performed.

RESULTS

Histopathological examination reported ulcerated inflamed granulation tissue with no evidence of malignancy. During follow-up, she remained neurologically intact with no recurrence.

CONCLUSION

Using both nasal and oral spaces allows placement of the endoscope in the nasal cavity and surgical instruments in the oral cavity without splitting the palate. Hence, the endoscopic transnasal and transoral approach has vast potential to be effective in carefully selected cases of cervical ORN.

Evolution from microscopic transoral to endoscopic endonasal odontoidectomy

OBJECT

The goal of this study was to compare the indications, benefits, and complications between the endoscopic endonasal approach (EEA) and the microscopic transoral approach to perform an odontoidectomy. Transoral approaches have been standard for odontoidectomy procedures; however, the potential benefits of the EEA might be demonstrated to be a more innocuous technique. The authors present their experience with 12 consecutive cases that required odontoidectomy and posterior instrumentation.

METHODS

Twelve consecutive cases of craniovertebral junction instability with or without basilar invagination were diagnosed at the National Institute of Neurology and Neurosurgery in Mexico City, Mexico, between January 2009 and January 2013. The EEA was used for 5 cases in which the odontoid process was above the nasopalatine line, and was compared with 7 cases in which the odontoid process was beneath the nasopalatine line; these were treated using the transoral microscopic approach (TMA). Odontoidectomy was performed after occipital-cervical or cervical posterior augmentation with lateral mass and translaminar screws. One case was previously fused (Oc-C4 fusion). The senior author performed all surgeries. American Spinal Injury Association scores were documented before surgical treatment and after at least 6 months of follow-up.

RESULTS

Neurological improvement after odontoidectomy was similar for both groups. From the transoral group, 2 patients had postoperative dysphonia, 1 patient presented with dysphagia, and 1 patient had intraoperative CSF leakage. The endoscopic procedure required longer surgical time, less time to extubation and oral feeding, a shorter hospital stay, and no complications in this series.

CONCLUSIONS

Endoscopic endonasal odontoidectomy is a feasible, safe, and well-tolerated procedure. In this small series there was no difference in the outcome between the EEA and the TMA; however, fewer complications were documented with the endonasal technique.

Endoscopic Endonasal Odontoidectomy

Odontoidectomy is the treatment of choice for irreducible ventral cervical-medullary compression. The endonasal endoscopic approach is an innovative approach for odontoidectomy. The aim of this article is to identify in which conditions this approach is indicated, discussing variants of the technique for selected cases of craniovertebral malformation with platybasia. We believe that the technical difficulties of this approach are balanced by the advantages for patients. Some conditions related to the patient and to the anatomy of the craniovertebral junction may favor adoption of the endoscopic endonasal approach, which should be considered complementary and not alternative to standard approaches.

Purely endoscopic endonasal surgery of the craniovertebral junction: A systematic review

BACKGROUND

Endoscopic endonasal surgery (EES) is a relatively novel approach to the craniovertebral junction (CVJ). The purpose of this analysis is to determine the surgical outcomes of patients who undergo purely EES of the CVJ.

METHODS

A search for articles related to EES of the CVJ was performed using the MEDLINE/PubMed database. A bibliographic search was done for additional articles. Demographics, presenting symptoms, imaging findings, complications, follow-up, and patient outcomes were analyzed.

RESULTS

Eighty-five patients from 30 articles were included. The mean patient age was 47.9 ± 24.8 years (range, 3 to 96 years), with 44.7% being male. The most common presenting symptom was myelopathy (n = 64, 75.3%). The most common indications for surgery were brainstem compression secondary to basilar invagination (n = 41, 48.2%) and odontoid pannus (n = 20, 23.5%). Odontoidectomy was performed in 97.6% of cases. Intraoperative complications occurred in 16 patients (18.8%) and postoperative complications occurred in 18 patients (21.2%). Six patients developed postoperative respiratory failure necessitating a tracheostomy. Neurologic improvement was seen in 89.4% of patients at a mean follow-up of 22.2 months.

CONCLUSION

Our analysis found that EES of the CVJ results in a high rate of neurologic improvement with acceptable complication rates. Given its minimally invasive nature and high success rate, this approach appears to be a reasonable alternative to the traditional transoral approach in select cases. This study represents the largest pooled sample size of EES of the CVJ to date. Increasing use of the endoscopic endonasal approach will allow for further studies with greater statistical power.

Endoscopic endonasal atlantoaxial transarticular screw fixation technique: an anatomical feasibility and biomechanical study

OBJECT The primary disadvantage of the posterior cervical approach for atlantoaxial stabilization after odontoidectomy is that it is conducted as a second-stage procedure. The goal of the current study is to assess the surgical feasibility and biomechanical performance of an endoscopic endonasal surgical technique for C1-2 fixation that may eliminate the need for posterior fixation after odontoidectomy. METHODS The first step of the study was to perform endoscopic endonasal anatomical dissections of the craniovertebral junction in 10 silicone-injected fixed cadaveric heads to identify relevant anatomical landmarks. The second step was to perform a quantitative analysis using customized software in 10 reconstructed adult cervical spine CT scans to identify the optimal screw entry point and trajectory. The third step was biomechanical flexibility testing of the construct and comparison with the posterior C1-2 transarticular fixation in 14 human cadaveric specimens. RESULTS Adequate surgical exposure and identification of the key anatomical landmarks, such as C1-2 lateral masses, the C-1 anterior arch, and the odontoid process, were provided by the endonasal endoscopic approach in all specimens. Radiological analysis of anatomical detail suggested that the optimal screw entry point was on the anterior aspect of the C-1 lateral mass near the midpoint, and the screw trajectory was inferiorly and slightly laterally directed. The custommade angled instrumentation was crucial for screw placement. Biomechanical analysis suggested that anterior C1-2 fixation compared favorably to posterior fixation by limiting flexion-extension, axial rotation, and lateral bending (p > 0.3). CONCLUSIONS This is the first study that demonstrates the feasibility of an endoscopic endonasal technique for C1-2 fusion. This novel technique may have clinical utility by eliminating the need for a second-stage posterior fixation operation in certain patients undergoing odontoidectomy.

Endoscopic Transnasal Approach for Urgent Decompression of the Craniocervical Junction in Acute Skull Base Osteomyelitis

Ventral epidural abscess with osteomyelitis at the craniocervical junction is a rare occurrence that typically mandates spinal cord decompression via a transoral approach. However, given the potential for morbidity with transoral surgery, especially in the setting of immunosuppression, together with the advent of extended endonasal techniques, the transnasal approach could be attractive for selected patients. We present two cases of ventral epidural abscess and osteomyelitis at the craniocervical junction involving C1/C2 that were successfully treated via the endoscopic transnasal approach. Both were treated in staged procedures involving posterior cervical fusion followed by endoscopic transnasal resection of the ventral C1 arch and odontoid process for decompression of the ventral spinal cord and medulla. Dural repairs were successfully performed using multilayered, onlay techniques where required. Both patients tolerated surgery exceedingly well, had brief postoperative hospital stays, and recovered uneventfully to their neurologic baselines. Postoperative magnetic resonance imaging confirmed complete decompression of the foramen magnum and upper C-spine. These cases illustrate the advantages and low morbidity of the endonasal endoscopic approach to the craniocervical junction in the setting of frank skull base infection and immunosuppression, representing to our knowledge a unique application of this technique to osteomyelitis and epidural abscess at the craniocervical junction.