Occipitocervical fusion following the extreme lateral transcondylar approach

Predicting the Need for Occipitocervical Fusion for Patients with Lower Clival Chordoma: A Single-Center Retrospective Study

OBJECTIVE

To assess the impact of tumor extension into the occipital condyle (OC) in lower clival chordoma management and the need for occipito-cervical fusion (OCF).

METHODS

A retrospective analysis was conducted on 35 patients with lower clival chordoma. The preoperative area of the intact OCs, Hounsfield units, and the integrity of the apical ligament and the tectorial membrane were assessed using preoperative imaging.

RESULTS

Seven (20%) patients were in the OCF group. The OCF group exhibited a higher prevalence of preoperative pain in the neck or head (P = 0.006), ligament absence (P = 0.022), and increased propensity for postoperative wound issues (P = 0.022) than the non-OCF group. The OCF group had less intact OCs (P < 0.001) and higher spinal instability neoplastic score (P = 0.002) than the non-OCF group. All patients with intact OCs < 60% underwent OCF, and those with OCs ≥ 70% were treated without OCF. Those with OCs between 60% and 69% underwent OCF if the ligaments were eroded, and did not undergo OCF if the ligaments were intact. Treatment strategies varied, with endoscopic endonasal approach alone being common. Radiation therapy was administered to 89% of patients. All 3 patients treated with OCF after tumor resection had wound issues; none treated with OCF before resection had wound issues. None developed atlanto-occipital instability. Survival rates did not significantly differ between groups.

CONCLUSIONS

In the absence of mobility-related neck pain, patients with lower clival chordoma and intact OC ≥ 60%, intact apical ligament, and intact tectorial membrane, may not require OCF.

Anatomy of the craniocervical junction - A review

An in-depth understanding of the anatomy of the craniocervical junction (CCJ) is indispensable in skull base neurosurgery. In this paper, we discuss the osteology of the occipital bone, the atlas (C1) and axis (C2), the ligaments and the muscle anatomy of the CCJ region and their relationships with the vertebral artery. We will also discuss the trajectory of the vertebral artery and review the anatomy of the jugular foramen and lower cranial nerves (IX to XII). The most important surgical approaches to the CCJ, including the far lateral approach, the anterolateral approach of Bernard George and the endoscopic endonasal approach, will be discussed to review the surgical anatomy.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Far Lateral Approach

Introduction  Skull base neuroanatomy is classically taught using surgical atlases. Although these texts are critical and rich resources for learning three-dimensional (3D) relationships between key structures, we believe they could be optimized and complemented with step-by-step anatomical dissections to fully meet the learning needs of trainees. Methods  Six sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A far lateral craniotomy was performed by each of three neurosurgery resident/fellow at varying stages of training. The study objective was the completion and photodocumentation of the craniotomy to accompany a stepwise description of the exposure to provide a comprehensive, intelligible, and anatomically oriented resource for trainees at any level. Illustrative case examples were prepared to supplement approach dissections. Results  The far lateral approach provides a wide and versatile corridor for posterior fossa operation, with access spanning the entire cerebellopontine angle (CPA), foramen magnum, and upper cervical region. Key Steps Include  The study includes the following steps: positioning and skin incision, myocutaneous flap, placement of burr holes and sigmoid trough, fashioning of the craniotomy bone flap, bilateral C1 laminectomy, occipital condyle/jugular tubercle drilling, and dural opening. Conclusion  Although more cumbersome than the retrosigmoid approach, a far lateral craniotomy offers unparalleled access to lesions centered lower or more medially in the CPA, as well as those with significant extension into the clival or foramen magnum regions. Dissection-based neuroanatomic guides to operative approaches provide a unique and rich resource for trainees to comprehend, prepare for, practice, and perform complex cranial operations, such as the far lateral craniotomy.

Morphological analysis and morphometry of the occipital condyle and its relationship to the foramen magnum, jugular foramen, and hypoglossal canal: implications for craniovertebral junction surgery

Anatomical knowledge of the occipital condyle (OC) and its relationships to surrounding structures is important for avoiding injury during craniovertebral junction (CVJ) surgeries. This study was conducted to evaluate the morphology and morphometry of OC and its relationship to foramen magnum, jugular foramen (JF), and hypoglossal canal (HC). Morphometric parameters including length, width, height, and distances from the OC to surrounding structures were measured. The oval-like condyle was the most common OC shape, representing for 33.0% of all samples. The mean length, width and height of OC were 21.3±2.4, 10.5±1.4, and 7.4±1.1 mm, respectively. Moreover, OC was classified into three types based on its length. The most common OC length in both sexes was moderate length or type II (62.5%). The mean distance between anterior tips and posterior tips of OC to basion, and opisthion were 11.5±1.4, 39.1±3.3, 25.2±2.2, and 27.4±2.7 mm, respectively. The location of intracranial orifice of HC was commonly found related to middle 1/3 of OC in 45.0%. JF was related to the anterior 2/3 of OC in 81.0%, the anterior 1/3 of OC in 12.5%, and the entire OC length in 6.5%. These morphological analysis and morphometric data should be taken into consideration before performing surgical operation to avoid CVJ instability and neurovascular structure injury.

Impact of Radiation Therapy on Outcomes After Spinal Instrumentation for Craniocervical Junction Malignancies

Objective

Spinal reconstruction after resection of invasive craniocervical junction malignancies is fraught with technical and management considerations as well as a paucity of data in the existing literature. In this study, we describe our experience with craniocervical junction malignancies, especially the influence of radiation on the need for revision spinal instrumentation.

Methods

We performed a retrospective chart review of all patients who underwent occipitocervical fixation between 2011 and 2019 at The University of Texas MD Anderson Cancer Center.

Results

Twenty-five patients had primary malignancies and 12 (30%) had metastatic tumors. Thirteen (33%) underwent a staged resection in multiple operations during their hospital stay. Tumor resection was performed in 19 patients (48%), while only stabilization was performed in 21 patients (52%). Nine patients (23%) underwent expanded endoscopic transclival approaches for tumor resection, 10 patients (25%) an extreme lateral approach, and 2 patients (5%) an anterior open approach. Eleven patients underwent early postoperative radiation therapy (within 3 months) and 8 underwent delayed radiation therapy (between 3 months and 1 year in 7 patients). The revision rate was 8%, with a median time to revision surgery of 42 months. The administration and timing of adjuvant radiation therapy relative to surgery had no significant effect on the need for instrumentation revision on log-rank and Cox regression analyses (p < 0.05).

Conclusion

Revision surgery was needed infrequently in our patients. Postoperative radiation therapy was not associated with hardware failure, indicating that the timing of radiation therapy should be dictated by the diagnosis and can be initiated postoperatively without delay.

Management of pediatric clival chordoma with extension to the craniocervical junction and occipito-cervical fusion: illustrative case

BACKGROUND

Chordomas are rare malignant neoplasms that develop from the primitive notochord with < 5% of the tumors occurring in pediatric patients younger than the age of 20. Of these pediatric chordomas, those affecting the craniocervical junction (C1–C2) are even more rare; therefore, parameters for surgical management of these pediatric tumors are not well characterized.

OBSERVATIONS

In this case, a 3-year-old male was found to have a clival chordoma on imaging with extension to the craniocervical junction resulting in spinal cord compression. Endoscopic-assisted transoral transclival approach for clival tumor resection was performed first. As a second stage, the patient underwent a left-sided far lateral craniotomy and cervical laminectomy for resection of the skull base chordoma and instrumented fusion of the occiput to C3. He made excellent improvements in strength and dexterity during rehab and was discharged after 3 weeks.

LESSONS

In pediatric patients with chordoma with extension to the craniocervical junction and spinal cord compression, decompression with additional occipito-cervical fusion appears to offer a good clinical outcome. Fusion performed as a separate surgery before or at the same time as the initial tumor resection surgery may lead to better outcomes.

Transmastoid Trautman's Triangle Combined Low Retrosigmoid Approach for Foramen Magnum Meningiomas: Surgical Anatomy and Technical Note

Objective  This study was aimed to assess the potential of utilizing a transmastoid Trautman's triangle combined low retrosigmoid approach for ventral and ventrolateral foramen magnum meningiomas (FMMs) surgical treatment. Methods  We simulated this transmastoid Trautman's triangle combined low retrosigmoid approach using five adult cadaveric heads to explore the associated anatomy in a step-by-step fashion, taking pictures of key positions as appropriate. We then employed this approach in a single overweight patient with a short neck who was suffering from large ventral FMMs and cerebellar tonsillar herniation. Results  Through cadaver studies, we were able to confirm that this transmastoid Trautman's triangle combined with low retrosigmoid approach achieves satisfactory cranial nerve and vasculature visualization while also offering a wide view of the whole of the ventrolateral medulla oblongata. We, additionally, have successfully employed this approach to treat a single patient suffering from large ventral FMMs with cerebellar tonsillar herniation. Conclusion  This transmastoid Trautman's triangle combined low retrosigmoid approach may represent a complement to treatment strategies for ventral and ventrolateral FMMs, particularly in patients with the potential for limited surgical positioning due to their being overweight, having a short neck and suffering from cerebellar tonsillar herniation.

Endoscope-assisted far-lateral transcondylar approach for craniocervical junction chordomas: a retrospective case series and cadaveric dissection

OBJECTIVE

Craniocervical junction (CCJ) chordomas are a neurosurgical challenge because of their deep localization, lateral extension, bone destruction, and tight relationship with the vertebral artery and lower cranial nerves. In this study, the authors present their surgical experience with the endoscope-assisted far-lateral transcondylar approach (EA-FLTA) for the treatment of CCJ chordomas, highlighting the advantages of this corridor and the integration of the endoscope to reach the anterior aspect and contralateral side of the CCJ and the possibility of performing occipitocervical fusion (OCF) during the same stage of surgery.

METHODS

Nine consecutive cases of CCJ chordomas treated with the EA-FLTA between 2013 and 2020 were retrospectively reviewed. Preoperative characteristics, surgical technique, postoperative results, and clinical outcome were analyzed. A cadaveric dissection was also performed to clarify the anatomical landmarks.

RESULTS

The male/female ratio was 1.25, and the median age was 36 years (range 14-53 years). In 6 patients (66.7%), the lesion showed a bilateral extension, and 7 patients (77.8%) had an intradural extension. The vertebral artery was encased in 5 patients. Gross-total resection was achieved in 5 patients (55.6%), near-total resection in 3 (33.3%), and subtotal resection 1 (11.1%). In 5 cases, the OCF was performed in the same stage after tumor removal. Neither approach-related complications nor complications related to tumor resection occurred. During follow-up (median 18 months, range 5-48 months), 1 patient, who had already undergone treatment and radiotherapy at another institution and had an aggressive tumor (Ki-67 index of 20%), showed tumor recurrence at 12 months.

CONCLUSIONS

The EA-FLTA provides a safe and effective corridor to resect extensive and complex CCJ chordomas, allowing the surgeon to reach the anterior, lateral, and posterior portions of the tumor, and to treat CCJ instability in a single stage.

Long-term Radiographic Outcome of Occipitocervical Fixation: An Analysis of Fusion Rate and Spontaneous Subaxial Alignment Change at an Average 7-year Follow-up

STUDY DESIGN

Retrospective case series.

OBJECTIVE

The aim of this study was to investigate the long-term radiographic outcome of patients who underwent occipitocervical fixation (OCF) using a modern screw/rod system.

SUMMARY OF BACKGROUND DATA

Few studies have reported fusion rates and radiographic alignment changes in unfused subaxial segments after OCF at a long-term follow-up.

METHODS

We retrospectively reviewed 22 patients who underwent OCF with a modern screw-based construct. The patients satisfied the minimum 2-year radiographic follow-up. Baseline demographics and the following pre- and postoperative sagittal alignment parameters were investigated. McGregor slope, O-C2 angle (OC2A), and C2-7 Cobb angle (CL). We grouped patients into those whose OC2A increased postoperatively (OC2A-increase group) and those whose OC2A decreased postoperatively (OC2A-decrease group). The postoperative sagittal alignment change was compared between the 2 groups at the final follow-up. The perioperative complications as well as fusion status based on computed tomography (CT) were investigated.

RESULTS

The average follow-up period was 89.7 months. The lowest instrumented vertebra was at C2 (63.6%), C3 (18.1%), or C4 (18.1%). The fusion rate at the final follow-up was 77.2%. Postoperative dysphasia occurred in two patients (16.6%) in the OC2A-decrease group, whereas distal junctional kyphosis was observed in two patients (20.0%) in the OC2A-increase group. The OC2A-increase group demonstrated a mean 4.8° decrease in CL as a compensation for the 5.1° increase in OC2A. In contrast, the OC2A-decrease group showed a mean 9.2° increase in CL as a compensation for the 6.3° decrease in OC2A.

CONCLUSION

The CT-confirmed fusion rate of OCF was 77.2% over an average 89.7-month follow-up. Compensatory sagittal alignment change can occur in the unfused subaxial segments in conjunction with the alignment change in the instrumented OC segments, whereas the horizontal gaze was maintained. Strong consideration for the intraoperative measurement of the OC2A should be given during OCF to minimize both early and long-term complications.Level of Evidence: 4.

Comparative Cadaveric Analysis for Surgical Corridor and Maneuverability: Far-Lateral Approach and Its Transcondylar Extension

OBJECTIVE

The necessity of partial occipital condyle (OC) resection for lesions in the ventral craniocervical junction is debatable. This study's purpose was to compare the surgical exposure of the classic far-lateral approach (FLA) and transcondylar FLA.

METHODS

The classic FLA and transcondylar FLA were performed in 12 human cadaveric heads (24 sides). The surgical corridor of 3 levels (a: vagus nerve, b: from the midpoint of proximal ends of the vagus and hypoglossal nerves to the midpoint of the distal ends of each nerve, c: hypoglossal nerve) and the maneuverability (the area between neurovascular structures that limits instrumental maneuvers) were measured after each approach.

RESULTS

The surgical corridors were significantly greater in transcondylar FLA than in classic FLA (a: 14.4 ± 3.4 mm vs. 17.1 ± 4.4 mm, P < 0.001; b: 8.6 ± 2.9 mm vs. 11.2 ± 4.1 mm, P < 0.001; c: 5.5 ± 2.2 mm vs. 7.7 ± 2.8 mm, P < 0.001). Transcondylar FLA also provided greater maneuverability than classic FLA (73.2 ± 23.9 mm² vs. 94.9 ± 32.2 mm², P < 0.001). The increased length of the surgical corridor was greatest in a (a: 2.7 ± 2.3 mm, b: 2.6 ± 2.0 mm, c: 2.2 ± 1.4 mm). However, the rate of increase was greatest in c (a: 18.9 ± 16.4%, b: 30.4 ± 26.2%, c: 44.8 ± 27.2%). The area of increased maneuverability was 21.7 ± 20.3 mm² (31.1 ± 27.8%) after partial OC resection.

CONCLUSIONS

Transcondylar FLA can significantly increase surgical exposure compared with the classic FLA, although also increasing surgical complications. Therefore, the surgical approach should be individualized according to each lesion and patient. The results of our study may assist in surgical decision-making regarding the need for OC resection.

Far lateral approach without occipital condylar resection for intradural ventral/ventrolateral foramen magnum tumors and aneurysms of V4 segment of vertebral artery: Review of surgical results

BACKGROUND

Controversies exist regarding the need and extent of condylar resection for safe surgical management of intradural ventral/ventrolateral foramen magnum (VFM) tumors and aneurysms of V4 segment of vertebral artery (VA) by far lateral approach. This retrospective study was conducted to evaluate the results of basic far lateral approach(retrocondylar approach) without upfront occipital condylar resection.

METHODS AND RESULTS

Twenty one patients underwent surgery via far lateral approach for intradural VFM tumors and aneurysms of V4 segment of VA at Sri Sathya Sai Institute of Higher Medical Sciences during 9 years(2008-2016) study period. Eight patients had VA aneurysms and 13 patients had intradural VFM tumors. After basic far lateral approach(retrocondylar approach), dura was opened and checked if the exposure was adequate for safe surgery. Retrocondylar approach provided adequate exposure for all these lesions and resection of occipital condyle/jugular tubercle was not required in any of these cases. Skeletonization or transposition of VA was not done in any of these cases. Gross total resection of the tumor could be done in 9 patients(9/13-69.2 %) and near total excision (>95 %) in 4 patients (4/13-30.8 %). Seven of the 8 VA aneurysms were successfully clipped. Outcome at a final follow up of 3 months or more was good(mRS<2) in 19 patients(19/21-90.5 %) and poor in 2 patients. Complications included lower cranial nerve deficits [transient-2/21(9.5 %), persisting-2/21(9.5 %)], motor deficits(2/21-9.5%), seventh nerve paresis(1/21-4.8%), sixth nerve paresis(2/21-9.5%) and pseudomeningocele(1/21-4.8%).

CONCLUSION

Basic far lateral (retrocondylar) approach provides excellent exposure for majority of VFM tumors and aneurysms of V4 segment of VA. Condylar resection(transcondylar approach), drilling of jugular tubercle (transtubercular approach), skeletonization/transposition of VA might not be required for safe surgical management of majority of these lesions.

Restabilization of the Occipitocervical Junction After a Complete Unilateral Condylectomy: A Biomechanical Comparison of Unilateral and Bilateral Fixation Techniques

BACKGROUND

Occipitocervical instability may result from transcondylar resection of the occipital condyle. Initially, patients may be able to maintain a neutral alignment but severe occipitoatlantal subluxation may subsequently occur, with cranial settling, spinal cord kinking, and neurological injury.

OBJECTIVE

To evaluate the ability of posterior fixation constructs to prevent progression to severe deformity after radical unilateral condylectomy.

METHODS

Eight human cadaveric specimens (Oc-C2) underwent biomechanical testing to compare stiffness under physiological loads (1.5 N m). A complete unilateral condylectomy was performed to destabilize one Oc-C1 joint, and the contralateral joint was left intact. Unilateral Oc-C1 or Oc-C2 constructs on the resected side and bilateral Oc-C1 or Oc-C2 constructs were tested.

RESULTS

The bilateral Oc-C2 construct provided the greatest stiffness, but the difference was only statistically significant in certain planes of motion. The unilateral constructs had similar stiffness in lateral bending, but the unilateral Oc-C1 construct was less stiff in axial rotation and flexion-extension than the unilateral Oc-C2 construct. The bilateral Oc-C2 construct was stiffer than the unilateral Oc-C2 construct in axial rotation and lateral bending, but there was no difference between these constructs in flexion-extension.

CONCLUSION

Patients who undergo a complete unilateral condylectomy require close surveillance for occipitocervical instability. A bilateral Oc-C2 construct provides suitable biomechanical strength, which is superior to other constructs. A unilateral construct decreases abnormal motion but lacks the stiffness of a bilateral construct. However, given that most patients undergo a partial condylectomy and only a small proportion of patients develop instability, there may be scenarios in which a unilateral construct may be appropriate, such as for temporary internal stabilization.

Hybrid antero-lateral transcondylar approach to the clivus: a laboratory investigation and case illustration

BACKGROUND

Surgical treatment of lesions involving the ventral craniovertebral junction (CVJ) and the lower clivus, traditionally involved complex lateral or transoral approaches to the skull base. However, mid or upper clivus involvement requires more extensive lateral approaches. Recently, the endoscopic endonasal approach (EEA) has become the standard for upper CVJ lesions and medial clival, and a valuable alternative for those tumors extending in its upper third as well as laterally. However, the EEA is associated with an increased risk of post-operative CSF leakage and infection when the tumor is characterized by an intradural extension. Furthermore, whenever the tumor has significant lateral and/or inferior extension below the odontoid process, the chances for a complete resection decrease.

METHOD

To analyze the extent of exposure of a hybrid microscopic-endoscopic transcondylar antero-lateral approach to the CVJ and clival region, and to verify its effectiveness in terms of mid and upper clival access. Five silicone-injected cadaver heads were used. Following a standard antero-lateral approach, condylectomy and jugular tubercle drilling were performed, after which angled endoscopes were utilized to extend the bone resection to the clivus. A volumetric assessment of the amount of clival removal was carried out. A case of CVJ chordoma operated through this approach is presented.

RESULTS

The hybrid antero-lateral transcondylar approach provides adequate exposure of the ventral CVJ, up to the dorsum sellae and the sphenoid sinus, the contralateral petrous apex, and the contralateral paraclival internal carotid artery (ICA). Approximately 60% of the total clival volume can be removed with this approach. The main limitation is the limited visualization of the ipsilateral paraclival ICA and petrous apex.

CONCLUSION

The hybrid antero-lateral transcondylar approach is a valuable surgical option for CVJ tumor extending from C2 to the mid and upper clivus.

From the Occipital Condyle to the Sphenoid Sinus: Extradural Extension of the Far Lateral Transcondylar Approach with Endoscopic Assistance

BACKGROUND

Surgical management of extensive skull base tumors, such as chordoma and chondrosarcoma, remains very challenging. The need for gross total removal to improve survival must be weighed against the risk of injury to neurovascular structures and the loss of stability at the craniovertebral junction. In cases of tumors that are already compromising craniovertebral junction stability, the occipital condyle can be exploited as a deep keyhole to reach the clivus, petrous apex, and sphenoid sinus.

METHODS

We performed an anatomic study on 7 cadaveric specimens to describe the main landmarks and boundaries of the corridor. We also provide a clinical case to demonstrate the feasibility of the approach.

RESULTS

In all specimens, using the space provided by the condyle, it was possible to drill the petrous bone up to the posterior wall of the sphenoid sinus following the direction of the inferior petrosal sinus. To successfully complete the approach, after the hypoglossal canal was exposed, endoscopic assistance was needed to overcome the narrowing of the visual field provided by the microscope.

CONCLUSIONS

In cases of invasive skull base tumor involving the craniovertebral junction and affecting its stability, the occipital condyle can be exploited as a deep keyhole to the homolateral and contralateral petrous apex, clivus, and sphenoid sinus.

Extreme lateral transodontoid approach to the ventral craniocervical junction: cadaveric dissection and case illustrations

OBJECTIVE

Surgical treatment of pathological processes involving the ventral craniocervical junction (CCJ) traditionally involves anterior and posterolateral skull base approaches. In cases of bilateral extension, when lesions extend beyond the midline to the contralateral side, a unilateral corridor may result in suboptimal resection. In these cases, the lateral extent of the tumor will prevent extirpation of the lesion via anterior surgical approaches. The authors describe a unilateral operative corridor developed along an extreme lateral trajectory to the anterior aspect of the clival and upper cervical dura, allowing exposure and resection of tumor on the contralateral side. This approach is used when the disease involves the bone structures inherent to stability at the anterior CCJ.

METHODS

To achieve exposure of the ventral CCJ, an extreme lateral transcondylar transodontoid (ELTO) approach was performed with transposition of the ipsilateral vertebral artery, followed by drilling of the C1 anterior arch. Resection of the odontoid process allowed access to the contralateral component of lesions across the midline to the region of the extracranial contralateral vertebral artery, maximizing resection.

RESULTS

Exposure and details of the surgical procedure were derived from anatomical cadavers. At the completion of cadaveric dissection, morphometric measurements of the relevant anatomical landmarks were obtained. Illustrative case examples for approaching ventral CCJ chordomas via the ELTO approach are presented.

CONCLUSIONS

The ELTO approach provides a safe and direct surgical corridor to treat complex lesions at the ventral CCJ with bilateral extension through a single operative corridor. This approach can be combined with other lateral approaches or posterior infratemporal approaches to remove more extensive lesions involving the rostral clivus, jugular foramen, and temporal bone.

A Microanatomical Study of the Far Lateral Approach

OBJECTIVE

The far-lateral approach (FLA) remains a challenge for neurosurgeons due to the complex anatomy of this region, especially in patients with anatomical variations. There is therefore an urgent need for better quantitative knowledge of the microsurgical anatomy of the FLA.

METHODS

The study was performed using the dried skulls and atlas vertebrae of 50 Chinese adults, in which significant clinical parameters were measured. We further used 12 cadaveric heads to simulate the FLA to explore the step-by-step anatomy entailed by this procedure, enabling us to obtain key images and related information.

RESULTS

Limited to hypoglossal canal, the occipital condyle posterior was abraded by roughly 10 mm, which provided good exposure to the ventral front of the foramen magnum. When occipital artery exits the occipital groove, the mean diameter was 2.20 mm. The average occipital artery suboccipital segment length was 65.26 mm. The posterior spinal artery (PSA) and posterior inferior cerebellar artery (PICA) generally originated from the fourth vertebral artery segment intradurally, and the mean distances from the PSA and PICA to the dural entry point of the vertebral artery were 2.62 mm and 8.71 mm, respectively. The incidence of PSA and PICA arising from the third vertebral artery segment was 16.67% and 4.17%, respectively.

CONCLUSIONS

Understanding the important anatomic structures of the CVJ region and developing improved knowledge of the microsurgical anatomy of the FLA offer an opportunity to ensure safe exposure and treatment of lesions in the ventral and ventrolateral regions of the CVJ.

Delayed Occipitocervical Instability With Cranial Settling After Far-Lateral Transcondylar Surgery for Invasive Skull Base Tumor

BACKGROUND

Occipitocervical instability is a rare but potentially severe complication of a far-lateral transcondylar surgical approach to the skull base.

OBJECTIVE

To investigate the incidence of clinically significant occipitocervical instability after transcondylar surgery via a far-lateral approach and to determine whether the extent of occipital condyle resection relative to the hypoglossal canal was associated with the development of occipitocervical instability.

METHODS

A retrospective review of patients undergoing far-lateral transcondylar surgery was performed at our institution to identify patients who developed postoperative occipitocervical instability.

RESULTS

Of the 61 far-lateral transcondylar operations performed, the authors identified 2 cases of delayed occipitocervical instability after surgery. In each case, the patient had tumor invading into the occipital condyle and supracondylar region and a resection extending anterior to the hypoglossal canal was performed. Both patients presented with pathological fractures and a severe occipitocervical deformity.

CONCLUSION

Patients who have tumor involvement of the occipital condyle and supracondylar region and undergo partial unilateral condylar resection are at risk for occipitocervical instability and should be considered for occipitocervical fusion.

The timing of fusion surgery for clival chordoma with occipito-cervical joint instability: before or after tumor resection?

Clival chordoma with occipito-cervical (OC) joint invasion can result in preoperative and postoperative instability. The authors investigate the appropriate timing of OC fusion to prevent instability-, fusion-, and surgery time-related morbidity. Twenty-two consecutive patients underwent surgery for clival chordoma from December 2008 to September 2014. OC fusion was performed for patients with OC joint invasion and instability due to preoperative destruction of the occipital condyle or extensive postoperative condylectomy. The data in relation to OC joint instability, fusion, and surgery time were analyzed retrospectively and compared between OC fusion before and after tumor resection. Of the 22 patients, 8 with tumor invasion of the OC joint underwent OC fusion. OC fusion was performed after tumor resection in one-stage for four patients and before tumor resection in two-stage for four patients. There was OC joint instability from tumor destruction of the occipital condyle in seven patients (87.5%). Patients with OC fusion after tumor resection encountered complications such as surgery site wound dehiscence, encephalitis, and cardiac arrest with consequent mortality in one patient. These complications were avoided in subsequent patients where OC fusion was performed before tumor resection. There were no differences in the extent of tumor resection between OC fusion before and after tumor resection. Two-stage OC fusion before tumor resection can reduce instability-, fusion-, and surgery time-related morbidity and achieve feasible tumor resection when OC joint instability is expected. The extent of tumor invasion and brain stem compression should be considered when fusion precedes tumor resection.

Occipitocervical Instability After Far-Lateral Transcondylar Surgery: A Biomechanical Analysis

BACKGROUND

After a far-lateral transcondylar approach, patients may maintain neutral alignment in the immediate postoperative period, but severe occipitoatlantal subluxation may occur gradually with cranial settling and possible neurological injury. Previous research is based on assumptions regarding the extent of condylar resection and the change in biomechanics that produces instability.

OBJECTIVE

To quantify the extent of bone removal during a far-lateral transcondylar approach, determine the changes in range of motion (ROM) and stiffness that occur after condylar resection, and identify the threshold of condylar resection that predicts alterations in occipitocervical biomechanics.

METHODS

Nine human cadaveric specimens were biomechanically tested before and after far-lateral transcondylar resection extending into the hypoglossal canal (HC). The extent of condylar resection was quantified using volumetric comparison between pre- and postresection computed tomography scans. ROM and stiffness testing were performed in intact and resected states. The extent of resection that produced alterations in occipitocervical biomechanics was assessed with sensitivity analysis.

RESULTS

Bone removal during condylar resection into the HC was 15.4%-63.7% (mean 35.7%). Sensitivity analysis demonstrated that changes in biomechanics may occur when just 29% of the occipital condyle was resected (area under the curve 0.80-1.00).

CONCLUSION

Changes in occipitocervical biomechanics may be observed if one-third of the occipital condyle is resected. During surgery, the HC may not be a reliable landmark to guide the extent of resection. Patients who undergo condylar resections extending into or beyond the HC require close surveillance for occipitocervical instability.

Simple Lateral Suboccipital Approach and Modification for Vertebral Artery Aneurysms: A Study of 52 Cases Over 10 Years

INTRODUCTION

Complex skull base approaches are frequently used to treat intracranial vertebral artery (VA) and proximal posterior inferior cerebellar artery (PICA) aneurysms. These complex procedures are associated with higher risk of neurovascular injury. Hence, a less-invasive surgical approach is needed to improve the efficacy and safety of treatment.

METHODS

A retrospective analysis was conducted on clinical and radiologic data from surgeries in which simple lateral suboccipital and "lateral-enough" approaches were used to clip VA aneurysms in the Department of Neurosurgery at Helsinki University Central Hospital from 2000 to 2009.

RESULTS

Fifty-two VA or PICA aneurysms were treated using the simple lateral suboccipital approach. Sixteen patients (31%) presented with an unruptured aneurysm, 21 patients (40%) with World Federation of Neurosurgical Societies (WFNS) grade 1-3, and 15 patients (29%) with World Federation of Neurosurgical Societies grade 4-5. The aneurysms were saccular in 48 cases (92%), dissecting in 3 cases (6%), and fusiform in 1 case (2%). The most common aneurysm location was the VA-PICA junction (81%). The mean final modified Rankin Scale score was 2, and in unruptured cases, all patients had favorable clinical outcomes. The main causes of unfavorable outcome were poor preoperative clinical grade (P = 0.002), preoperative intraventricular hemorrhage (P = 0.008), postoperative hydrocephalus (P = 0.003), brain infarction (P = 0.005), and postoperative pneumonia (P < 0.001).

CONCLUSIONS

We describe a 10-year experience using a simple lateral suboccipital approach and its modification by the senior author (J.H.) to treat VA and proximal PICA aneurysms. Unfavorable outcome was related to the poor preoperative clinical grade, preoperative intraventricular hemorrhage, and postoperative pneumonia.

Bilateral C-1 lateral mass reconstruction following radical resection of a giant osteoblastoma of the atlas: case report

Osteoblastoma is a rare, benign, osteoid-producing, and slow-growing primary bone tumor, typically arising in long bones or in the spine, with a slight male predominance. This report describes the surgical treatment of a giant C-1 (atlantal) osteoblastoma diagnosed in a young male patient with neurofibromatosis Type 1. The authors describe the clinical presentation, the surgical procedure for complete excision and stabilization, and results as of the 1-year follow-up. They detail a bilateral occipitoaxial spinal interarticular stabilization technique that they used after complete tumor excision. To the best of their knowledge, this is the first case of bilateral C-1 lateral mass reconstruction by this technique to be reported in the literature.

The far-lateral approach: destruction of the condyle does not necessarily result in clinically evident craniovertebral junction instability

OBJECT

Far-lateral or extreme-lateral approaches to the skull base allow access to the lateral and anterior portion of the lower posterior fossa and foramen magnum. These approaches include a certain extent of resection of the condyle, which potentially results in craniocervical junction instability. However, it is debated what extent of condyle resection is safe and at what extent of condyle resection an occipitocervical fusion should be recommended. The authors reviewed cases of condyle resection/destruction with regard to necessity of occipitocervical fusion.

METHODS

The authors conducted a retrospective analysis of all patients in whom a far- or extreme-lateral approach including condyle resection of various extents was performed between January 2007 and December 2014.

RESULTS

Twenty-one consecutive patients who had undergone a unilateral far- or extreme-lateral approach including condyle resection were identified. There were 10 male and 11 female patients with a median age of 61 years (range 22–83 years). The extent of condyle resection was 25% or less in 15 cases, 50% in 1 case, and greater than 75% in 5 cases. None of the patients who underwent condyle resection of 50% or less was placed in a collar postoperatively or developed neck pain. Two of the patients with condyle resection of greater than 75% were placed in a semirigid collar for a period of 3 months postoperatively and remained free of pain after this period. At last follow-up none of the cases showed any clear sign of radiological or clinical instability.

CONCLUSIONS

The unilateral resection or destruction of the condyle does not necessarily result in craniocervical instability. No evident instability was encountered even in the 5 patients who underwent removal of more than 75% of the condyle. The far- or extreme-lateral approach may be safer than generally accepted with regard to craniocervical instability as generally considered and may not compel fusion in all cases with condylar resection of more than 75%.

Atlanto-occipital Instability Following Endoscopic Endonasal Approach for Lower Clival Lesions: Experience With 212 Cases

BACKGROUND

The endoscopic endonasal approach (EEA) for craniocervical lesions involving the lower clivus and occipital condyles carries an unclear risk of atlanto-occipital (AO) instability requiring arthrodesis.

OBJECTIVE

Elucidate risk factors for AO instability following EEA for clival lesions.

METHODS

We reviewed patients with clival tumors who underwent EEA at our institution between 2002 and 2012. Resection of the lower clivus, foramen magnum, AO joint, and occipital condyles were evaluated on fine-cut postoperative computed tomography.

RESULTS

Two hundred twelve patients (mean age 47.9 years, 57.1% male) underwent transclival EEA for lower clival lesions. In addition to the lower clivus, resection involved the condyle in 14.2% of patients, the foramen magnum in 16.5%, and the AO joint in 1.4%. Quantification of condyle resection revealed complete resection in 3 cases, 75% resection in 8 cases, 50% resection in 6 cases, and 25% resection in 13 cases. Seven of these patients had EEA combined with an open, far-lateral approach. In total, 7 patients required arthrodesis following EEA (3.3%), 4 of them after a combined approach. All patients who underwent arthrodesis had primary bone tumors such as chordoma, chondrosarcoma, or osteosarcoma (P = .022). Degree of condyle resection was a significant factor predisposing to occipitocervical instability (P = .001 and P < .001 for 75% and 100% condyle resection, respectively). Use of a combined approach was significantly associated with arthrodesis (P < .001).

CONCLUSION

EEA resection of the occipital condyles that results in greater than 75% condyle resection or EEA in combination with an open approach significantly increases the risk of AO instability and likely necessitates AO fixation.

ABBREVIATIONS

AO, atlanto-occipitalEEA, endoscopic endonasal approachOC, occipitocervical.

Occipital condyle to cervical spine fixation in the pediatric population

Fixation at the craniovertebral junction (CVJ) is necessary in a variety of pediatric clinical scenarios. Traditionally an occipital bone to cervical fusion is preformed, which requires a large amount of hardware to be placed on the occiput of a child. If a patient has previously undergone a posterior fossa decompression or requires a decompression at the time of the fusion procedure, it can be difficult to anchor a plate to the occipital bone. The authors propose a technique that can be used when faced with this difficult challenge by using the occipital condyle as a point of fixation for the construct. Adult cadaveric and a limited number of case studies have been published using occipital condyle (C-0) fixation. This work was adapted for the pediatric population. Between 2009 and 2012, 4 children underwent occipital condyle to axial or subaxial spine fixation. One patient had previously undergone posterior fossa surgery for tumor resection, and 1 required decompression at the time of operation. Two patients underwent preoperative deformity reduction using traction. One child had a Chiari malformation Type I. Each procedure was performed using polyaxial screw-rod constructs with intraoperative neuronavigation supplemented by a custom navigational drill guide. Smooth-shanked 3.5-mm polyaxial screws, ranging in length from 26 to 32 mm, were placed into the occipital condyles. All patients successfully underwent occipital condyle to cervical spine fixation. In 3 patients the construct extended from C-0 to C-2, and in 1 from C-0 to T-2. Patients with preoperative halo stabilization were placed in a cervical collar postoperatively. There were no new postoperative neurological deficits or vascular injuries. Each patient underwent postoperative CT, demonstrating excellent screw placement and evidence of solid fusion. Occipital condyle fixation is an effective option in pediatric patients requiring occipitocervical fusion for treatment of deformity and/or instability at the CVJ. The use of intraoperative neuronavigation allows for safe placement of screws into C-0, especially when faced with a challenging patient in whom fixation to the occipital bone is not possible or is less than ideal.

Biomechanical Evaluation of the Craniovertebral Junction After Anterior Unilateral Condylectomy: Implications for Endoscopic Endonasal Approaches to the Cranial Base

BACKGROUND:

Endoscopic endonasal approaches to the craniovertebral junction and clivus, which are increasingly performed for ventral skull base pathology, may require disruption of the occipitocondylar joint.

OBJECTIVE:

To study the biomechanical implications at the craniovertebral junction of progressive unilateral condylectomy as would be performed through an endonasal exposure.

METHODS:

Seven upper cervical human cadaveric specimens (C0-C2) underwent nondestructive biomechanical flexibility testing during flexion-extension, axial rotation, and lateral bending at C0-C1 and C1-C2. Each specimen was tested intact, after an inferior one-third clivectomy, and after stepwise unilateral condylectomy with an anterior approach. Angular range of motion (ROM), lax zone, and stiff zone were determined and compared with the intact state.

RESULTS:

At C0-C1, mobility during flexion-extension and axial rotation increased significantly with progressive condylectomy. ROM increased from 14.3 ± 2.7° to 20.4 ± 5.2° during flexion and from 6.7 ± 3.5° to 10.8 ± 3.0° during right axial rotation after 75% condyle resection (P &lt; .01). At C1-C2, condylectomy had less effect, with ROM increasing from 10.7 ± 2.0° to 11.7 ± 2.0° during flexion, 36.9 ± 4.8° to 37.1 ± 5.1° during right axial rotation, and 4.3 ± 1.9° to 4.8 ± 3.3° during right lateral bending (P = NS). Because of marked instability, the 100% condylectomy condition was untestable. Changes in ROM were a result of changes more in the lax zone than in the stiff zone.

CONCLUSION:

Lower-third clivectomy and unilateral anterior condylectomy as would be performed in an endonasal approach cause progressive hypermobility at the craniovertebral junction. On the basis of biomechanical criteria, craniocervical fusion is indicated for patients who undergo &gt; 75% anterior condylectomy.

Biomechanical evaluation of the craniovertebral junction after inferior-third clivectomy and intradural exposure of the foramen magnum: implications for endoscopic endonasal approaches to the cranial base

OBJECT

Endoscopic endonasal approaches to the craniovertebral junction (CVJ) and clivus are increasingly performed for ventral skull-base pathology, but the biomechanical implications of these approaches have not been studied. The aim of this study was to investigate the spinal biomechanics of the CVJ after an inferior-third clivectomy and anterior intradural exposure of the foramen magnum as would be performed in an endonasal endoscopic surgical strategy.

METHODS

Seven upper-cervical human cadaveric specimens (occiput [Oc]-C2) underwent nondestructive biomechanical flexibility testing during flexion-extension, axial rotation, and lateral bending at Oc-C1 and C1-2. Each specimen was tested intact, after an inferior-third clivectomy, and after ligamentous complex dissection simulating a wide intradural exposure using an anterior approach. Angular range of motion (ROM), lax zone, and stiff zone were determined and compared with the intact state.

RESULTS

Modest, but statistically significant, hypermobility was observed after inferior-third clivectomy and intradural exposure during flexion-extension and axial rotation at Oc-C1. Angular ROM increased incrementally between 6% and 12% in flexion-extension and axial rotation. These increases were primarily the result of changes in the lax zone. No significant changes were noted at C1-2.

CONCLUSIONS

Inferior-third clivectomy and an intradural exposure to the ventral CVJ and foramen magnum resulted in hypermobility at Oc-C1 during flexion-extension and axial rotation. Although the results were statistically significant, the modest degree of hypermobility observed compared with other well-characterized CVJ injuries suggests that occipitocervical stabilization may be unnecessary for most patients.

A systematic review of occipital cervical fusion: techniques and outcomes

Object

Numerous techniques have been historically used for occipitocervical fusion with varied results. The purpose of this study was to examine outcomes of various surgical techniques used in patients with various disease states to elucidate the most efficacious method of stabilization of the occipitocervical junction.

Methods

A literature search of peer-reviewed articles was performed using PubMed and CINAHL/Ovid. The key words “occipitocervical fusion,” “occipitocervical fixation,” “cervical instrumentation,” and “occipitocervical instrumentation” were used to search for relevant articles. Thirty-four studies were identified that met the search criteria. Within these studies, 799 adult patients who underwent posterior occipitocervical fusion were analyzed for radiographic and clinical outcomes including fusion rate, time to fusion, neurological outcomes, and the rate of adverse events.

Results

No articles stronger than Class IV were identified in the literature. Among the patients identified within the cited articles, the use of posterior screw/rod instrumentation constructs were associated with a lower rate of postoperative adverse events (33.33%) (p < 0.0001), lower rates of instrumentation failure (7.89%) (p < 0.0001), and improved neurological outcomes (81.58%) (p < 0.0001) when compared with posterior wiring/rod, screw/plate, and onlay in situ bone grafting techniques. The surgical technique associated with the highest fusion rate was posterior wiring and rods (95.9%) (p = 0.0484), which also demonstrated the shortest fusion time (p < 0.0064). Screw/rod techniques also had a high fusion rate, fusing in 93.02% of cases.

When comparing outcomes of surgical techniques depending on the disease status, inflammatory diseases had the lowest rate of instrumentation failure (0%) and the highest rate of neurological improvement (90.91%) following the use of screw/rod techniques. Occipitocervical fusion performed for the treatment of tumors by using screw/rod techniques had the lowest fusion rate (57.14%) (p = 0.0089). Traumatic causes of occipitocervical instability had the highest percentage of pain improvement with the use of screw/plates (100% improvement) (p < 0.0001).

Conclusions

Based on the existing literature, techniques that use screw/rod constructs in occipitocervical fusion are associated with very favorable outcomes in all categories assessed for all disease processes. For patients requiring occipitocervical arthrodesis for the treatment of inflammatory diseases, screw/rod constructs are associated with the most favorable outcomes, while posterior wiring and onlay in situ bone grafting is associated with the least favorable outcomes. Occipitocervical arthrodesis performed for the diagnosis of tumor is associated with the lowest rate of successful arthrodesis using screw/rod techniques, while posterior wiring and rods have the highest rate of arthrodesis. The nonspecified disease group had the lowest rate of surgical adverse events and the highest rate of neurological improvement.

Posterior occipitocervical (C0–3) fusion using polyaxial occipital condyle to cervical spine screw and rod fixation: a radiographic and cadaveric analysis

Numerous conditions affect the occipitocervical junction requiring treatment with occipitocervical fixation. In this paper the authors present their technique of craniocervical fixation achieved with the cephalad extension of posterior C1–3 polyaxial screw and rods to polyaxial screws placed in the occipital condyles. They retrospectively analyzed occipital condyle morphology obtained from CT analyses of 40 patients with normal cervical spines, evaluated occipital condyle screw placement feasibility in 4 cadavers, and provided a case report of a 70-year-old woman with rheumatoid arthritis, basilar invagination, and atlantoaxial instability who was treated with this novel technique. Based on radiographic analysis of occipital condyle anatomy, they concluded that on average a 3.5-mm-diameter × 20- to 30-mm-long screw can be safely placed at an angle of 20–33° from the sagittal plane. Overall, measuring the condylar heights (mean [± SD] 10.8 ± 1.5 mm, range 8.1–15.0 mm), widths (mean 11.1 ± 1.4 mm, range 8.5–14.2 mm), lengths (20.3 ± 2.1 mm, range 15.4–24.6 mm), and angles (mean 32.8 ± 5.2°, range 20.2–45.8°) by using CT studies is an accurate and precise method. This finding correlates with the results of prior anatomical studies of occipital condyles and is important in the planning of craniovertebral junction surgery.

Surgical approach for hypoglossal schwannomas to prevent deformity of the atlanto-occipital joint

BACKGROUND

Hypoglossal schwannomas are very rare tumors that often enlarge the hypoglossal canal and jugular foramen, and erode the bone bridge of the occipital condyle. We compared pre- and postoperative 3D bone CT images and discussed the ideal craniotomy to prevent fracture formation.

METHOD

Seven patients with hypoglossal schwannomas underwent surgery in our department. Six cases were type B and 1 case was type C. All patients complained of hypoglossal nerve paresis and nuchal pain.

FINDINGS

We used the condylar fossa approach for four cases of type B, the lateral suboccipital approach with C1 laminectomy for two cases of type B and extradural transjugular approach for one case of type C. In all cases, the lateral rim of the foramen magnum or the posterior rim of the jugular foramen was not resected at the same time. The intracranial part of the tumor was removed in all type B cases. Radiotherapy was added for the residual tumor. No patient had deformity or fracture of the joint.

CONCLUSIONS

Opening the hypoglossal canal and dural incision toward the hypoglossal canal are important for high radicality. However, preservation of the lateral rim of the foramen magnum must be noted to prevent consecutive deformity or fracture of the atlanto-occipital joint.

Tumor-biology and current treatment of skull-base chordomas

Chordomas are rare, slow growing tumors of the axial skeleton, which derive from the remnants of the fetal notochord. They can be encountered anywhere along the axial skeleton, most commonly in the sacral area, skull base and less commonly in the spine. Chordomas have a benign histopathology but exhibit malignant clinical behavior with invasive, destructive and metastatic potential. Genetic and molecular pathology studies on oncogenesis of chordomas are very limited and there is little known on mechanisms governing the disease. Chordomas most commonly present with headaches and diplopia and can be readily diagnosed by current neuroradiological methods. There are 3 pathological subtypes of chordomas: classic, chondroid and dedifferentiated chordomas. Differential diagnosis from chondrosarcomas by radiology or pathology may at times be difficult. Skull base chordomas are very challenging to treat. Clinically there are at least two subsets of chordoma patients with distinct behaviors: some with a benign course and another group with an aggressive and rapidly progressive disease. There is no standard treatment for chordomas. Surgical resection and high dose radiation treatment are the mainstays of current treatment. Nevertheless, a significant percentage of skull base chordomas recur despite treatment. The outcome is dictated primarily by the intrinsic biology of the tumor and treatment seems only to have a secondary impact. To date we only have a limited understanding this biology; however better understanding is likely to improve treatment outcome. Hereby we present a review of the current knowledge and experience on the tumor biology, diagnosis and treatment of chordomas.

Foramen magnum meningiomas: clinical outcome after microsurgical resection via a posterolateral suboccipital retrocondylar approach

OBJECTIVE

We analyzed a consecutive series of patients operated for a foramen magnum (FM) meningioma located on the ventral aspect of the medulla oblongata via a posterolateral suboccipital retrocondylar approach with regard to long-term surgical outcome.

METHODS

Clinical data in a consecutive series of 25 patients experiencing a meningioma attached to dura of the anterior or anterolateral FM rim were retrospectively reviewed.

RESULTS

The most common symptoms of the 19 women and six men (mean age, 59.2 yr) was cervico-occipital pain (72%) and gait disturbance (32%). Clinical examination revealed gait ataxia in 48% of the patients. As depicted from preoperative magnetic resonance imaging (MRI), dural attachment of the meningioma at the FM rim was anterior in 36% and anterolateral in 64% of cases. Tumor removal was accomplished via a posterolateral suboccipital retrocondylar approach in all patients. A Simpson Grade 2 resection was achieved in 96% of the patients. Permanent surgical morbidity and mortality rates were 8 and 4%, respectively. No tumor recurrence was observed after a mean follow-up period of 6.1 years (range, 1-14 yr) with clinical and MRI examination, and 80% of the patients have regained full daily activity.

CONCLUSION

Anterior and anterolateral FM meningiomas that displace the medulla/spinal cord can be safely and completely resected via a posterolateral suboccipital retrocondylar approach. A tumor remnant should be left on critical neurovascular structures in cases with poor arachnoid dissection planes.

Cervicomedullary compression and occipitocervical instability

A wide variety of pathologic processes can involve the cervicomedullary junction leading to spinal cord compression and mechanical instability. Effective surgical management involves accurate patient selection, appropriate operative planning, and meticulous surgical technique. Many different options for decompression exist, each associated with a unique set of risks and benefits. Spinal stabilization has been enhanced greatly through the evolution of posterior occipitocervical instrumentation constructs. Careful attention to detail may decrease the incidence of potential complications and provide the surgeon with an effective management strategy to maximize clinical outcome.

Analysis of radiological features relative to histopathology in 42 skull-base chordomas and chondrosarcomas

Chordomas and chondrosarcomas are malignant tumors that are reported to have similar clinical presentations and radiological features but different behaviors and outcomes. The aim of this retrospective study was to determine whether specific radiological features of skull-base chordomas or chondrosarcomas are correlated with histopathology, and thus allow preoperative diagnosis. The study involved 32 classic chordomas, 6 chondroid chordomas and 4 chondrosarcomas (42 tumors total). For each case, tumor size and extent, the detailed anatomy involved, and magnetic resonance imaging and computed tomography findings were analyzed. Tumor extent was assessed using a novel method that assessed presence/absence in 18 defined skull-base zones. The chondrosarcomas presented significantly earlier in life than the chordomas (means, 20.5 years versus 36 years, respectively). At time of diagnosis, the median tumor volume was 23 cm(3) (range, 1.2-78.8 cm(3)) and the mean tumor extent was 6.7+/-2.9 zones. There were no differences between chordomas and chondrosarcomas, or between the two chordoma subgroups, with respect to lesion volume or extent. Comparison of other imaging findings revealed no features that were diagnostic for either chordoma or chondrosarcoma. The data support previous claims that chondrosarcomas present earlier in life than chordomas, but this finding is not diagnostic. There is wide variation in the extent of skull-base chordomas and chondrosarcomas, and in the specific anatomical structures these tumors involve. None of the MRI or CT features of these tumors appear to be useful for differentiating chordomas from chondrosarcomas preoperatively. For surgical planning, specific, area-oriented definition of tumor extent might provide more useful information than tumor-type classification schemes.

Lateral approach to anterolateral tumors at the foramen magnum: factors determining surgical procedure

OBJECTIVE

We discuss and evaluate surgical strategies and results in 42 patients with a variety of tumors involving the anterior and anterolateral foramen magnum and present factors affecting the degree of resection and patient outcomes. We describe our surgical techniques for resection of these tumors via the lateral approach, including consideration for occipital condylar resection and vertebral artery management.

METHODS

A retrospective analysis was performed of 42 surgically treated patients with tumors involving the anterior and anterolateral foramen magnum. Patients received treatment between 1991 and 2002; patients' files, operative notes, and pre- and postoperative imaging studies were used for the analysis.

RESULTS

The female-to-male ratio was 28:14. Mean patient age was 47 years. Pathological entities comprised 18 meningiomas, 12 chordomas, 3 glomus tumors, 3 schwannomas, and 6 miscellaneous tumors. We mobilized the vertebral artery at the dural entry point in all patients with meningiomas. The vertebral artery was mobilized at the C1 transverse foramen for the majority of extradural tumors. Partial condyle resection was performed in eight meningiomas and five extradural tumors. Complete condyle resection was required in 12 cases, including 9 chordomas, 2 carcinomas, and 1 bone-invading pituitary adenoma. Thirteen patients required occipitocervical fusion after tumor resection.

CONCLUSION

In anterior or anterolaterally located foramen magnum tumors, we think the extreme lateral or far lateral approach affords significant advantages. Vertebral artery mobilization and occipital condyle resection may be needed depending on the extent and location of the foramen magnum tumor and its specific pathological characteristics. Tumor invading the occipital condyle or significant condylar resection may cause occipitocervical instability and require fusion.

Occipitocervical fusion after resection of craniovertebral junction tumors

Object

Surgical access to tumors at the craniovertebral junction (CVJ) requires extensive bone removal. Guidelines for the use of occipitocervical fusion (OCF) after resection of CVJ tumors have been based on anecdotal evidence. The authors performed a retrospective study of factors associated with the use of OCF in 46 patients with CVJ tumors. The findings were used to develop recommendations for use of OCF in such patients.

Methods

The authors retrospectively reviewed the cases of 51 patients with CVJ tumors treated by their group between March 1991 and February 2004. Forty-six patients were available for follow up. Charts were reviewed to obtain data on demographic characteristics, presenting symptoms, and perioperative complications. Preoperative computerized tomography scans and magnetic resonance imaging studies were obtained in all patients. Occipitocervical fusion was performed in patients who had undergone a unilateral condyle resection in which 70% or more of the condyle was removed, a bilateral condyle resection with 50% removal, or C1–2 vertebral body destruction. Of the 46 patients, 16 had foramen magnum meningiomas, 17 had chordomas, one had a chondrosarcoma, two had Schwann cell tumors, two had glomus tumors, and eight had other types of tumors. Twenty-three (50%) of the 46 patients underwent OCF, including 15 of the 17 patients with chordomas (88%). None of the patients with meningiomas required fusion. Seventeen (71%) of the 24 patients presenting with neck pain preoperatively underwent OCF.

Conclusions

Patients presenting with neck pain had a 71% chance of undergoing OCF. Patients with chordomas and metastatic tumors were most likely to require OCF. One patient with a 50% unilateral condylar resection returned with OC instability for which OCF was required. Based on their clinical experience and published biomechanical studies, the authors recommend that OCF be performed when 50% or more of one condyle is resected.

Anterolateral approach to the craniocervical junction

OBJECT

The authors present the surgical results obtained using the anterolateral approach to the craniocervical junction (CCJ) to resect a lesion with an extradural component located anterolateral to the foramen magnum and upper cervical spine.

METHODS

The anterolateral approach, which is a presternomastoid retrojugular route to the CCJ, was performed in 14 patients. The skin incision follows the anterior edge of the sternomastoid muscle. The vertebral artery (VA) was exposed at C-1. This approach was extended either down to the cervical spine or anteriorly to the jugular foramen, according to specific requirements. Two patients had previously undergone other surgical procedures. The follow-up period ranged from 4 months to 6.2 years. The tumor resection was complete in 11 cases and subtotal in two. In a case of vertebral coiling, a vein graft was interposed between the V1 and the V3 segments of the VA, and the bypass was still patent at the 2-year follow-up examination. In two cases involving a glomus tumor, there was a transitory postoperative seventh cranial nerve deficit.

CONCLUSIONS

The aforementioned technique allows for sufficient access to lesions located anterolateral to the CCJ. It is indicated in cases in which lesions exhibit a significant extradural component, and it provides good control of the VA, the cervical portion of the internal carotid artery, sigmoid-jugular complex, and lower cranial nerves. This approach can easily be combined with a posterolateral approach and can be extended anteriorly toward the jugular foramen and inferiorly toward the lower cervical spine.

Tumors of the skull base in children: review of tumor types and management strategies

Although many treatment strategies for skull base tumors in adults have been reported, relatively little has been reported regarding such therapies in the pediatric population. Skull base tumors in children present a therapeutic challenge because of their unique pathological composition, the constraints of the maturing skull and brain, and the small size of the patients. In this review, the authors examine the pediatric skull base lesions that occur in the anterior, middle, and posterior cranial base, focusing on unique pediatric tumors such as encepahalocele, fibrous dysplasia, esthesioneuroblastoma, craniopharyngioma, juvenile nasopharyngeal angiofibroma, cholesteatoma, chordoma, chondrosarcoma, and Ewing sarcoma. They review management strategies that include radio- and chemotherapy, as well as surgical approaches with emphasis on the modifications and complications associated with the procedures as they apply in children. Evidence for the advantages and limitations of radiotherapy, chemotherapy, and surgery as it pertains to the pediatric population will be examined. With a working knowledge of skull base anatomy and special considerations of the developing craniofacial skeleton, neurosurgeons can treat skull base lesions in children with acceptable morbidity and mortality rates. Outcomes in this population may be better than those in adults, in part because of the benign histopathology that frequently affects the pediatric skull base, as well as the plasticity of the maturing nervous system.