Endoscopic Endonasal Approach to the Ventral Cranio-Cervical Junction: Anatomical Study

Summary. Summary.   Objective: In order to develop an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process under the concept of a minimally invasive surgical strategy, a cadaver study was performed.   Methods: Sixteen artery-injected adult head specimens were used. Endonasal endoscopic approach was made through one- or two-nostril routes following the Jho's endonasal paraseptal technique. Rod-lens endoscopes, which were 2.7 or 4 mm in diameter, 18 cm in length with 0-, 30-, and 70-degree lenses, were used.   Results: Surgical landmarks leading to the craniocervical junction were the inferior margin of the middle turbinate, nasopharynx and Eustachian tube. The nasopharynx was readily identified following the inferior margin of the middle turbinate. The line drawn between the Eustachian tubes indicated the juncture between the clivus and atlas. With a midline mucosal incision, the ventral cranio-cervical junction was exposed. Odontoid resection was performed with removal of the anterior arch of the atlas. Clival resection can be performed as much rostral as required. Manoeuverability of the surgical instruments was better with a two-nostril technique than with a one-nostril. Although the entire midline clivus was accessible rostrally, C-2 was the caudal limit through this endonasal route. A suturing device needed to be developed for mucosal or dural closure for live operations.   Conclusion: This cadaver study demonstrates that an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process can be a valid alternative to the conventional transoral approach.     

The influence of cervical spine position on the three anterior endoscopic approaches to the craniovertebral junction: an imaging study

Background contextThree endoscopic anterior approaches, the transnasal, transoral, and transcervical approaches, are used for ventral lesions of the craniovertebral junction and have been compared regarding surgical working distances and approach angles. However, how the position of the cervical spine influences the depths of surgical corridors and approach angles for the three approaches has not been evaluated.PurposeTo evaluate the depths of surgical corridors and the approach angles for the three endoscopic approaches, taking the influence of cervical spine position into account.Study designA radiographic study comparing three anterior endoscopic approaches to the craniovertebral junction.Patient sampleCervical extension and flexion radiographs for 34 patients and cross-sectional computed tomography scans for 30 additional patients were assessed.Outcome measuresThe depths of the surgical corridors and the approach angles for the three endoscopic approaches in the midsagittal planes.MethodsWe determined the mean angles of the surgical trajectories for the endoscopic transoral and transcervical approaches on cervical extension and flexion radiographs. In addition, we measured the depths of the surgical corridors and the approach angles for the three approaches in the midsagittal plane.ResultsThe average depths of surgical corridors were as follows: endonasal, 93.65 mm; transoral, 85.27 mm; transcervical, 62.97 mm (in extension). The average approach angles were as follows: endonasal, 31.22°; transoral, 30.87°; transcervical, 36.58° (in extension).ConclusionsThe position of the cervical spine does not influence the surgical convenience of the endoscopic transnasal approach, but it can influence the endoscopic transoral and transcervical approaches, especially the latter. The endoscopic transcervical approach offers several advantages over the endoscopic transoral and endonasal approaches.     

Benign osteoblastoma of the odontoid process of the axis with secondary aneurysmal bone cyst component: a case report

The authors report their experience on one patient with osteoblatoma of the odontoid process of the axis with secondary aneurysmal bone cyst. According to their knowledge, this is the first case, reported in the literature, of this kind of lesion in that particular anatomical region. Because of the rarity of this lesion, it was difficult to have a certain preoperative diagnosis. Therefore, the patient underwent a biopsy via a transoral route. The biopsy was performed over the noncalcified component of the lesion. The intraoperative histological examination showed the benign nature of the lesion. Thereafter, the lesion was totally removed, succeeding in preserving the remaining part of the odontoid process and the anterior arch of C1. In the follow-up, there was no evidence of cranio-vertebral instability. The histological examination revealed an osteoblastoma of the odontoid process of the axis with a secondary aneurysmal bone cyst. To the best of our knowledge, this is the first case reported in the literature.     

Endoscope-assisted microsurgical transoral approach to the anterior craniovertebral junction compressive pathologies

At the present time, an update to the classical microsurgical transoral decompression is strongly provided by the most recent literature dealing with the introduction of the endoscopy in spine surgery. In this paper, we present our experience on the endoscope-assisted microsurgical transoral approach to anterior craniovertebral junction (CVJ) compressive pathology. We analysed seven patients (3 paediatrics and 4 adults ranging from 6 to 78 years) operated on for CVJ decompressive procedures using an open access, microsurgical technique, neuronavigation and endoscopy. All techniques mentioned were simultaneously employed. Among the endoscopic routes described in the literature, we have preferred the transoral using 30° endoscopes. In all the cases endoscopy allowed a radical decompression compared to the microsurgical technique alone, as confirmed intraoperatively with contrast medium fluoroscopy. In conclusion, endoscopy represents a useful complement to the standard microsurgical approach to the anterior CVJ; it provides information for a better decompression with no need for soft palate splitting, hard palate resection, or extended maxillotomy. Moreover, intraoperative fluoroscopy helps to recognize residual compression. Virtually, in normal anatomic conditions, no surgical limitations exist for endoscopically assisted transoral approach, compared with the pure endonasal and transcervical endoscopic approaches. In our opinion, the endoscope deserves a role as “support” to the standard transoral microsurgical approach since 30° angulated endoscopy significantly increases the surgical area exposed at the level of the anterior CVJ.     

颅底病变手术入路方法选择的探讨

1992～1996年间治疗10例颅底部肿瘤和齿状突骨折。其中斜坡肿瘤3例。齿状突骨折7例。10例均经CT或MRI、DSA检查确诊.经口咽入路或前颅凹底入路两种方式将肿瘤切除。术后患者临床症状都得到了良好改善,无一例死亡。作者认为,斜坡肿瘤和齿状突骨折经前颅凹底或口咽显微外科治疗是一种安全有效的方式。     

Anterior surgery of the upper cervical spine.

The authors report the results obtained in a series of more than 80 cases submitted to 76 operations of the upper cervical spine by transoral approach with a minimum follow-up of two years. The cases include: 15 unstable fractures or non-union of the odontoid processes; 28 cases of post-traumatic instability of C1-C2 level without fracture of the odontoid process; 13 cases of rheumatoid arthritis with instability at C1-C2; 14 cases of severe anomalies of the craniovertebral junction, often associated with basilar impression and spinal cord compression, of which 7 cases presented with tetraparesis; 6 malignant tumors. The method used involves an anterior transoral approach, more often without tracheotomy, and with exposure of the anterior aspect of the atlas and of the odontoid process by means of a midline incision of the posterior wall of the pharynx. When spinal cord lesion was present, decompression and reconstruction by bone grafts taken from the iliac crest were performed. In nearly all of the cases osteosynthesis with an anterior plate was used. Complications were mild. There were two cases of infection, observed at the onset of our experience, which were resolved after removal of the instrumentation. There was loosening of a screw in three cases; this was eliminated through the digestive tube with no consequences. There were no early intra- or postoperative deaths. Consolidation was obtained in most of the patients, and only in three cases did we observe a loss of postoperative reduction. Among patients affected with tetraparesis we observed many cases of neurological recovery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transoral approach to extradural non-neoplastic lesions of the craniovertebral junction

Background

The transoral approach allows for an unobstructed anterior view of the craniovertebral junction from the lower clivus to C1 and C2. It can be applied to a heterogeneous spectrum of pathological lesions involving this area including craniovertebral junction malformations, atlanto-axial synovial cysts, pseudoarthrosis following odontoid fractures, selected cases of retro-odontoid pannus, and vertical translocation in rheumatoid patients.

Methods

Microsurgical strategy is dictated by the nature and site of the target lesion. Atlas preservation during transoral approach (atlas-sparing technique) minimizes postoperative instability and is suitable for the majority of extradural non-neoplastic lesions of the craniovertebral junction. The transoral trans-atlas approach allows for a wider exposure of the anterior craniovertebral junction, but at the price of a higher incidence of postoperative instability; it is usually required in patients with severe basilar invagination or irreducible vertical translocation in rheumatoid arthritis.

Conclusions

The transoral corridor is an effective route to approach a variety of anterior extradural lesions of the craniovertebral junction. Tailoring the approach to each specific lesion provides the needed exposure whilst limiting postoperative instability.     

Odontoid process and clival regeneration with Chiari malformation worsening after transoral decompression: an unexpected and previously unreported cause of “accordion phenomenon”

Purpose

Transoral odontoidectomy followed by occipito-cervical fixation is a widely used approach to relieve ventral compressions at the craniovertebral junction (CVJ). Despite the large amount of literature on this approach and its complications, no previous reports of odontoid process and clival regeneration following transoral odontoidectomy are present in the English literature.

Methods

We report the case of odontoid process and clival regeneration following transoral odontoidectomy.

Results

A 7-year-old boy presented with symptoms of brainstem and upper cervical spinal cord compression due to a complex malformation at the CVJ including a basilar invagination with Chiari malformation. A successful transoral microsurgical endoscopic-assisted odontoidectomy extended to the clivus was performed along with occipito cervical instrumentation and fusion. Clinical and radiological resolution of the CVJ compression was evident up to 2 years post-op, when the child had a relapse of some of the presenting symptoms and the follow-up CT and MRI scans showed a quite complete regrowth of the odontoid process, clival partial regeneration and recurrence of preoperative Chiari malformation.

Conclusions

Besides the need of an accurate complete resection of the periosteum, which apparently was incompletely performed in our case, our experience suggests the need of resection of the odontoid down to the dentocentral synchondrosis and an accurate lateral removal of the bone surrounding the anterior tubercle of the Clivus is advised when an anterior CVJ decompression is required in children presenting a still evident synchondrosis at neuroradiological investigation.

     

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.

Endoscopic transnasal resection of the odontoid: case series and clinical course

The transoral route is the gold standard for odontoid resection. Results are satisfying though surgery can be challenging for patients and surgeons due to its invasiveness. A less invasive transnasal approach could provide a sufficient extent of resection with less collateral damage. The technique of transnasal endoscopic odontoid resection is demonstrated by a case series of three patients. A fully endoscopic transnasal odontoid resection was conducted by use of CT-based neuronavigation. A complete odontoid resection succeeded in all patients. Symptoms such as dysarthria, swallowing disturbance, salivary retention, myelopathic gait disturbances, neck pain, and tetraparesis improved in all patients markedly. Transnasal endoscopic odontoid resection is a feasible alternative to the transoral technique. It leaves the oropharynx intact, which could result in lower approach related complications especially in patients with bulbar symptoms.     

A neurosurgical view of anatomical evaluation of anterior C1–C2 for safer transoral odontoidectomy

An anatomical study for evaluation of anterior C1–C2. To provide essential anatomic data for safer transoral odontoidectomy. The surface dimensions of the atlas vertebra and the transoral approach for odontoidectomy have been described in detail. Anterior arcus of C1 must be drilled out to reach odontoid process for transoral odontoidectomy. The thickness of anterior ring of C1 has not been studied before. Sixty, dried adult atlas and 60 axis vertebrae and ten cadaveric craniocervical specimens were measured for the following: (1) bony drilling depth (BDD), the distance from the anterior wall of anterior ring of C1 to anterior wall of odontoid; (2) minimum drilling diameter (MDD), distance of minimum C1 anterior ring removal for odontoid resection on horizontal plane; (3) maximum bony drilling diameter (MBDD), distance of maximum C1 anterior ring removal for odontoid resection on horizontal plane. Lateral border of this diameter is limited by medial borders of the lateral mass; (4) the widest odontoid diameters (WOD) on coronal sections were measured. On 60 atlas and axis vertebrae, the BDD was 7.0 ± 1.2 mm on dry bones, the distance between the medial borders of the lateral mass (MBDD) was 16.1 ± 1.5 mm, and the WOD on coronal sections (WOD) was 9.8 ± 0.8 mm. On cadavers, the distance between the two edges of C1 anterior ring removal for odontoid resection (MDD) was 10.8 ± 1.1 mm and the WOD on coronal sections (WOD) was 10.1 ± 1.4 mm. An odontoid surgery through transoral approach is safe and feasible. A quantitative understanding of the anterior anatomy of C-1 and C-2 is necessary when considering transoral odontoid resection. In this study the authors define safe zones for anterior atlas and axis.     

Endoscopic transnasal odontoidectomy to treat basilar invagination with congenital osseous malformations

Purpose

Transoral resection of the odontoid has been accepted as a standard procedure to decompress the cervicomedullary junction during the past several decades. The endoscopic transnasal odontoidectomy is emerging as a feasible surgical alternative to conventional microscopic transoral approach. In this article, we describe several operative nuances and pearls from our experience about this approach, which provided successful decompression.

Methods

From September 2009 to April 2010, three consecutive patients with basilar invagination, of which the etiology was congenital osseous malformations, underwent endoscopic transnasal odontoidectomy. All patients presented with myelopathy. The last two cases also received occipitocervical fixation and bone fusion during the same surgical episode to ensure stability.

Results

All the patients were extubated after recovery from anesthesia and allowed oral food intake the next day. Cerebrospinal fluid rhinorrhea was found in the second case and cured by continuous lumber drainage of cerebrospinal fluid. No infection was noted. The average follow-up time was more than 24 months. Remarkable neurological recovery was observed postoperative in all patients.

Conclusion

The endoscopic transnasal odontoidectomy is a feasible approach for anterior decompression of pathology at the cervicomedullary junction. The advantages over the standard transoral odontoidectomy include elimination of risk of tongue swelling and teeth damaging, improvement of visualization, alleviation of prolonged intubation, reduction of need for enteral tube feeding and less risk of affecting phonation. The minimally invasive access and faster recovery associated with this technique make it a valid alternative for decompression of the ventral side of the cervicomedullary junction.     

Odontoid-sparing transnasal approach for drainage of craniocervical epidural abscess; a novel technique and review of the literature

Background Context

Surgical approaches to the craniovertebral junction (CVJ) are challenging. Available approaches include posterior, transoral, endonasal, and anterior extended retropharyngeal approach. Resection of the odontoid process is necessary to gain access to the pathology posterior to it. The resultant cranio-atlanto-axial instability usually necessitates subsequent posterior stabilization.

Extended endoscopic endonasal transclival approach to the ventrolateral brainstem and related cisternal spaces: anatomical study

Advances in endoscopic endonasal skull base surgery have led to the development of new routes to areas beyond the midline skull base. Recently, feasible surgical corridors to the lateral skull base have been described. The aim of this study was to describe the anatomical exposure of the ventrolateral brainstem and posterior fossa through an extended endoscopic endonasal transclival transpetrosal and transcondylar approach. Six human heads were used for the dissection process. The arterial and venous systems were injected with red- and blue-colored latex, respectively. A pre- and postoperative computed tomography (CT) scan was carried out on every head. The endoscopic endonasal transclival approach was extended through an anterior petrosectomy and a medial condylectomy. A three-dimensional model of the approach was reconstructed, using a dedicated software, from the overlapping of the pre- and post-dissection CT imaging of the specimen. An extended endoscopic transclival approach allows to gain access through an extradural anterior petrosectomy and medial condylectomy to the anterolateral surface of the brainstem and the posterior fossa. Two main intradural anatomical corridors can be described: first, between the V cranial nerve in the prepontine cistern and the VII–VIII cranial nerves in the cerebellopontine and cerebellomedullary cistern; second, between the VII–VIII cranial nerves and the IX cranial nerve, in the premedullary cistern. Extending the transclival endoscopic approach by performing an extradural anterior petrosectomy and a medial condylectomy provides a safe and wide exposure of the anterolateral brainstem with feasible surgical corridors around the main neurovascular structures.     

Transoral vs. Endoscopic Endonasal Approach for Clival/Upper Cervical Chordoma

The surgical results of 18 cases of clival/upper cervical chordoma treated in the last decade via the endoscopic endonasal approach (EEA, 9 cases) and the transoral-transpalatal approach (TO-TPA, 9 cases) were compared. Each group showed the same incidence of subdural invasion, with 5 cases each. The superior (frontal base) and lateral surgical fields were wider by EEA, but the inferior view lower than the cranio-vertebral junction (CVJ) was wider by TO-TPA. Gross total removal was achieved in 3 cases in the EEA group, but in only 1 case in the TO-TPA group. Differences in radicality might be due to the extent of the lateral and subdural overview. However for large tumors extending below the CVJ, TO-TPA was the only viable approach for surgical removal. Surgical complications were higher in the EEA (4 cases) than the TO-TPA group (1 case), and were mainly caused by aggressive management of subdural invasion in the EEA group. Post-operative oral intake was earlier and the operative time was shorter in the EEA group. The surgical results were more radical and less invasive in the EEA group than the TO-TPA group. However in tumors extending below the CVJ, the surgical field in EEA was limited, indicating the need to use the transoral route or a combination of routes. A higher complication rate following subdural management was a negative factor that requires improvement in the EEA group and two-staged EEA followed by a transcranial approach may be considered for the cases with subdural invasion.     

Screwing the odontoid process. A functional operation

The authors describe a case of direct screw fixation of the odontoid process via an anterolateral retropharyngeal subhyoid pre-sternomastoid approach and discuss the indications for this operation. In this particular case, immobilization by a cervical collar or a halo vest was not chosen because of its constraining character and the risk of secondary displacement and pseudarthrosis. C1-C2 or occipitospinal arthrodesis, whether performed via a posterior, lateral or anterior approach, is difficult to perform and always leads to a functional handicap. The transoral approach does not allow direct screw fixation of the dens. Dens screwing via an anterior pre-sternomastoid subhyoid approach is the most logical and least disabling technique. The subhyoid approach is much simpler than the suprahyoid approach. This technique is used in fractures of the odontoid process with an ablique downward and backward fracture line, with or without arch fracture of C1, and allows screwing perpendicular to the fracture line. Considering the present results and the literature, the double screw fixation does not seem to be justified.     

经口咽入路显微直视减压术治疗颅颈区畸形

目的 探讨颅颈区畸形前路显微直视减压手术的方法和疗效。方法 颅颈区畸形45例,MRI表现为齿状突肥大,向后上方突出,斜坡了争入颅底,致颅底成角畸形,延髓及上颈段脊髓腹侧受压变形。其中16例还伴有颅后窝容积减小、小脑扁桃体下疝及脊髓空洞症。采用经口咽入路显微直视下切除齿状突、伴坡下部及增生的结缔组织,解除其对延髓、颈髓的压迫。结果 痊愈38例（84.4%),好转4例（8.9%),无效3例（6.7%)。手术并发症有脑脊液漏2例,环枕脱位1例,软腭裂开1例。结论 经口咽入路显微直视减压术是治疗以延髓、颈髓腹侧受压为主的颅颈区畸形的首选方法。     

Transoral operations for craniospinal malformations

The transoral approach to the lower third of the clivus and to the ventral aspect of the upper cervical spine is used in craniospinal malformations with or without dislocation as well as in basilar aneurysms, ventrally situated cranio-spinal tumours, fractures of the odontoid process, and in rheumatoid arthritis compressing the spinal cord. In consideration of the literature and ten personal cases the indications and techniques of the transoral approach in craniospinal malformations are discussed. According to our own experiences and those of other authors it is possible to expose the lower clivus and the cervical spine down to C2 by a midline incision of the pharyngeal wall using a mouth retractor and oral intubation. Splitting of the soft palate or resection of the hard palate are not necessary, a tracheotomy should be performed only in exceptional cases. In congenital craniospinal malformations without dislocation or instability causing a ventral compression of the spinal cord, for instance by the odontoid process, the transoral decompression is preferable to dorsal decompressing operations. In cases of pure instability without any space-occupying lesion the transoral and posterior approach are possible in order to perform a fusion. The last one seems more advantageous in these cases. In craniospinal malformations with dislocation causing a ventral and dorsal narrowing of the spinal canal, apart from the decompression a stabilization has to be achieved. In these usually complex malformations individual treatment is necessary. According to the rare cases in the literature and to our own experience a primary anterior decompression, followed by a most careful posterior stabilization seems to produce the most favourable results.