Far-lateral approach without C1 laminectomy for microsurgical treatment of vertebral artery and proximal posterior inferior cerebellar artery aneurysms: Experience from 48 patients

Background

In the endovascular era, most of vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms were mainly treated with endovascular procedures. This study aimed to demonstrate the microsurgical treatment via the far-lateral approach without C1 laminectomy and its clinical outcomes.

Methods

Forty-eight patients with VA and proximal PICA aneurysms treated by microsurgery through the far-lateral approach without C1 laminectomy, between January 2016 and June 2021, were retrospectively evaluated.

Results

Most patients (87.5%) presented with subarachnoid hemorrhage. Grading at presentation was poor in 41.7%. The rates of VA dissecting aneurysms, saccular aneurysms of the VA-PICA junction, and true PICA saccular aneurysms were 54.2, 18.7, and 14.6%, respectively. All aneurysms were located above the lower margin of the foramen magnum. The far-lateral approach without C1 laminectomy was successfully used in all patients without residual aneurysms. Various surgical strategies were applied depending on the characteristics of the aneurysm. Good outcomes 3 months postoperatively were achieved in 77.1% and 89.3% for the overall and good-grade groups, respectively.

Conclusions

Microsurgery is a safe and effective treatment of VA and proximal PICA aneurysms. Moreover, the far-lateral approach without C1 laminectomy was adequate and effective for aneurysms located above the lower border of the foramen magnum.

Volumetric comparative analysis of anatomy through far-lateral approach: surgical space and exposed tissues

Background

The three-dimensional (3D) visualization model has ability to quantify the surgical anatomy of far-lateral approach. This study was designed to disclose the relationship between surgical space and exposed tissues in the far-lateral approach by the volumetric analysis of 3D model.

Methods

The 3D skull base models were constructed using MRI and CT data of 15 patients (30 sides) with trigeminal neuralgia. Surgical corridors of the far-lateral approach were simulated by triangular pyramids to represent two surgical spaces exposing bony and neurovascular tissues. Volumetric comparison of surgical anatomy was performed using pair t test.

Results

The morphometric results were almost the same in the two surgical spaces except the vagus nerve (CN X) exposed only in one corridor, whereas the volumetric comparison represented the statistical significant differences of surgical space and bony and neurovascular tissues involved in the two corridors (P<0.001). The differences of bony and neurovascular tissues failed to equal the difference of surgical space.

Conclusions

For far-lateral approach, the increase of exposure for the bony and neurovascular tissues is not necessarily matched with the increase of surgical space. The volumetric comparative analysis is helpful to provide more detailed anatomical information in the surgical design.

The Far-Lateral Suboccipital Approach to the Lesions of the Craniovertebral Junction

The far-lateral suboccipital approach and its variants, including the transcondylar, supracondylar, and paracondylar approaches, are essential skull base techniques for the neurosurgeon to expose and treat pathologies located at the ventral and ventrolateral craniovertebral junction. An understanding of the surgical anatomy and technical nuances of these approaches is vital for preventing catastrophic brainstem or spinal cord injury, neurovascular injury, and/or cranial nerve injury. This is achieved by carefully studying the location, the rostral-caudal and lateral extents of the lesion itself, and the anatomy of the surrounding structures on preoperative imaging. The amount of bony exposure should be tailored to each specific lesion to avoid unnecessary bone drilling and therefore decrease the risk of potential craniocervical instability. Minimizing retraction of the cerebellum, brainstem, and spinal cord is important for preventing neurologic injury; therefore, appropriate intraoperative head positioning and adequate bony exposure should be ensured, especially for more ventrally located lesions. A thorough knowledge of the anatomy of the extradural and intradural segments of the vertebral artery, and the lower cranial nerves, in relation to the lesion is also critical. For almost all lesions, the far-lateral suboccipital route with no or minimal condylar drilling is more than adequate for removing the most ventral lesions. Herein, we discuss the indications, general and preoperative considerations, and surgical anatomy and technical nuances of this approach.

Far-Lateral Approach for Medullary Cavernous Malformation: 2-Dimensional Operative Video

Medullary cavernous malformations are the rarest subtype of brainstem cavernous malformation and are associated with a high degree of morbidity. Selection of surgical candidates is critical, and cases are most favorable when the cavernous malformation abuts the surface of the brainstem. This limits the amount of native tissue transgressed during the resection. This patient had a large cavernous malformation within the caudal medulla eccentric. A right-sided paramedian far-lateral approach was used to access the brainstem. The cavernous malformation was readily apparent along the medullary surface and was dissected away in its entirety. Postoperative imaging confirmed complete resection. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Microneurosurgical Management of Posterior Inferior Cerebellar Artery Aneurysms: Results of a Consecutive Series

Aneurysms of the posterior inferior cerebellar artery (PICA) are uncommon. The complex anatomy of PICA and its intimate relationships with medulla, lower cranial nerves, and jugular tubercle makes the surgical treatment of these aneurysms fascinating. The reported is study aimed at a critical review of the overall results of a personal series of PICA aneurysms, treated by the senior author, R. Galzio. Demographics, charts, videos, outcome, and follow-up of a cohort of PICA aneurysms managed in the last 10 years were retrospectively analyzed, focusing only upon those treated with microneurosurgery. Twenty-five patients, harboring a single aneurysm, were operated on. Fifteen aneurysms were ruptured. Nineteen were proximal, all of these being been treated through a far-lateral approach. Trans-condylar or trans-tubercular variants were rarely necessary and however reserved to peculiar cases. Twenty-three aneurysms underwent direct treatment consisting of clip ligation. At 6-month follow-up, 60% of patients had a modified Rankin Score (mRS) of 0-2. Given the high anatomical variability of both PICA and patients' bony anatomy, a case-by-case meticulous preoperative imaging evaluation is mandatory for the choice of the most suitable and tailored surgical corridor which, in turn, is pivotal to achieve the best outcome.

Technique Nuances for Functional Preservation of Lower Cranial Nerves during Surgical Management of Ventral Foramen Magnum Meningiomas Via a Dorsal Lateral Approach

BACKGROUND

This study established novel technique nuances in surgery for ventral foramen magnum meningiomas (vFMMs) via a dorsal lateral approach.

METHODS

From July 2012 to July 2019, 37 patients with vFMMs underwent tumor resection surgery and were operated on with a dorsal lateral approach. Two safe zones were selected as the entrance of the surgical corridor. Safe zone I was located between the dural attachment of the first dental ligament (FDL) and the branches of C1; safe zone II lay between the dural attachment of the FDL and the jugular foramen. The tumor was debulked first through safe zone I and then through safe zone II. The tumor was removed through a trajectory from the caudal to cephalad to allow tumor debulking from below and downward delivery, away from the brainstem and lower cranial nerves.

RESULTS

Thirty-three patients underwent gross total resection, and 4 patients underwent subtotal resection. Four patients transiently required a nasogastric feeding tube. All patients recovered within 3 months postoperatively. Three patients (8.1%) developed permanent mild hoarseness and dysphagia as a result of postoperative damage of cranial nerves IX and X. One patient underwent tracheotomy. No patient experienced tumor recurrence during the follow-up period.

CONCLUSIONS

We established a minimal retraction principle, in which the selection of 2 safe zones as the entrance of the surgical corridor, tumor removal from the inferior to superior direction, and debulking followed by devascularization were the key elements to implement the minimal retraction principle in vFMM surgery.

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 for Ventral and Ventrolateral Upper Cervical Meningiomas: A Case Series and Literature Review

STUDY DESIGN

Retrospective cohort study.

PURPOSE

To evaluate the safety and efficacy of the far-lateral approach in the resection of ventral and ventrolateral upper cervical meningiomas.

OVERVIEW OF LITERATURE

Upper cervical meningiomas are a common disease entity. These lesions can be surgically treated via many accesses. The far-lateral approach is a very appealing technique for these lesions.

METHODS

We assessed 23 patients with a mean age of 57.3±15 years. According to the Japanese Orthopedic Association (JOA) scale; eight patients had grade 0, nine had grade I, and six had grade II. All patients underwent plain radiography and magnetic resonance imaging of the cervical spine. The foramen magnum was involved in 10 patients, C1-2 in seven, C2-3 in four, and C3-4 in two. All patients were operated via the far-lateral approach.

RESULTS

Gross total resection was achieved in 21 patients. Sixteen lesions were psammomatous, five were fibroblastic, and two were meningothelial meningiomas. The mean operative duration was 135±40 minutes, while the mean operative blood loss was 450±210 mL, and the mean hospital stay was 4.3±2.2 days. At the final follow-up that was conducted at 27.6±21 months and as per the JOA score; 16 patients were classified into grade 0 and 7 into grade II. The condition of none of our patients deteriorated postoperatively. There was no significant correlation of the clinical outcome with tumor level, pathological subtype of the tumor, symptom duration, age, and sex. There was no significant correlation of tumor resection completeness with tumor level, tumor pathological subtype, or tumor topography (ventral or ventrolateral).

CONCLUSIONS

The far-lateral approach is a safe and effective access for ventral and ventrolateral cervical meningiomas. It allows direct access to tumor with no spinal cord or nerve roots traction, and thus may yield a fairly better outcome than the standard posterior approach.

Quantitative Analysis of the Far-Lateral, Supra-Articular Transcondylar Transtubercular Approach Using Cadaveric Computed Tomography and Magnetic Resonance Imaging

BACKGROUND

Removing the jugular tubercle (JT) is regarded as an important step in the far-lateral approach; however, few cadaveric studies have objectively evaluated it.

OBJECTIVE

To quantitatively analyze the effect of JT removal in the far-lateral approach, using cadaveric computed tomography (CT) and magnetic resonance (MR) imaging.

METHODS

The far-lateral, supra-articular transcondylar transtubercular approach was employed on 23 sides of 13 formalin-fixed cadaveric heads. CT bone images were obtained before and after JT removal, and MR images were obtained before dissection and were merged with the CT bone images. The angles of attack used to approach the ventral region of the medulla, the distances between the medulla and the bony structure, and the volume of the paramedullary space were measured at the level of the JT on axial CT-MR fusion images. The values obtained after JT removal were compared with those obtained before JT removal.

RESULTS

All evaluated values were significantly increased after JT removal, including the angle of attack at the level of the JT (29.8 ± 7.4° vs 58.2 ± 15.5°, P < .001), the distance between the olive and the JT (6.4 ± 2.0 mm vs 9.5 ± 5.0 mm, P = .01), and the volume of the space around the medulla (0.28 ± 0.04 cm3 vs 0.47 ± 0.09 cm3, P < .001).

CONCLUSION

The paramedullary surgical working space widened by JT removal was quantitatively demonstrated in the cadaveric CT and MR imaging study. The measurement methods in this study can be applied to clinical cases and other skull base cadaveric studies.

Unique Far-Lateral Closure Technique: Technical Note

BACKGROUND

The far-lateral approach is a mainstay in gaining access to the ventrolateral craniocervical junction for tumor removal and the treatment of vascular lesions. It has a reportedly high rate of cerebrospinal fluid leak (up to 20%), which can bring devastating consequences, including meningitis, and may require wound revision associated with a longer hospital stay.

OBJECTIVE

To describe a closure technique employed to close the access corridor provided by the far-lateral approach and present an illustrative case.

METHODS

The far-lateral closure technique employs dural closure, followed by fat buttress, to alleviate dead space and reduce the likelihood of fluid collection and leakage.

RESULTS

This technique has been successfully used by the senior author for more than 14 yr, with a rate of cerebrospinal fluid leak of 2.9%.

CONCLUSION

This unique approach and closure of the far-lateral craniotomy is a reasonable option for the approach to the ventrolateral craniocervical junction. Skull base surgeons can consider the use of this closure technique to ensure watertight closure.

Comparative analysis of surgical exposure and freedom between the subtonsillar, endoscope-assisted subtonsillar, and far-lateral approaches to the lower clivus: A cadaveric study

The far-lateral (FL)approach is a classic technique for skull base surgeries involving the lower clivus (LC).Recently, a modified suboccipital midline approach known as the subtonsillar (ST) approach, along with the endoscope-assisted subtonsillar (EST) approach, has been described as a minimally invasive technique to treat LC lesions. However, there is no quantitative study on comparing these approaches together for reaching LC. We aimed to compare surgical exposure and freedom provided by ST, EST, and FL approaches for various targets at LC. These approaches were performed on each side of five cadaveric specimens (total 10 sides), and relevant parameters were quantified and compared using a repeated measures ANOVA test. FL approach yielded the greatest surgical area (237.8 ± 56.0 mm²) and exposure, including lengths of glossopharyngeal nerve (16.2 ± 1.9 mm), hypoglossal nerve (11.4 ± 2.4 mm), vertebral artery (23.9 ± 3.3 mm), followed by EST and ST approaches. For surgical freedom, FL approach provided the greatest angle of attack (90.0 ± 14.0° at jugular foramen, 95.1 ± 15.8° at hypoglossal canal, 83.4 ± 31.4° at bifurcation point of posterior inferior cerebellar artery and vertebral artery). Our systematic comparison suggests that EST approach, compared to ST approach, can significantly increase surgical exposure to the medial side of LC, but FL approach still provides the greatest surgical exposure and freedom at LC. Despite the limitations of a cadaveric study, our quantitative data can update the literature on currently available surgical techniques for reaching LC and better inform preoperative planning in this area. Further studies should be performed to evaluate these approaches in clinical practice.

Exposure of the External Carotid Artery Through the Posterior Neck Triangle, Cadaveric Surgical Simulation: 2-Dimensional Operative Video

The external carotid artery (ECA) is a robust extracranial donor used for high-flow cerebrovascular bypass procedures. It is usually exposed through the anterior triangle of the neck and may be used to revascularize recipients in the anterior or upper posterior cerebral circulations. However, when a high-flow bypass to the posterior circulation is indicated, oftentimes the patient needs to be put in the prone position (or variants thereof). In such situations, accessing the ECA through the anterior triangle of the neck can be challenging. Therefore, using a technique that enables the surgeon to expose the ECA through a posterior approach could be helpful.1 Although we have not yet encountered a case requiring this type of exposure and bypass, this cadaveric surgical simulation video demonstrates the surgical technique of exposing the ECA through the posterior triangle of the neck (as a cadaveric video, no patient consent was necessary). Briefly, this technique involves an inferolateral extension of the muscular stage of the far-lateral approach and exposing the ECA through a plane developed between the parotid gland and the posterior belly of the digastric muscle. The technical details of this technique are described. Also, relevant anatomic information regarding the safety measures taken to protect adjacent neurovascular structures are discussed.

Clipping of a PICA aneurysm located on the contralateral side of its parent vertebral artery in front of the brainstem: how I do it

BACKGROUND

Vertebro-PICA aneurysms may be challenging because of their relationship with the brainstem and the lower cranial nerves, especially when the vertebral artery is tortuous and the aneurysm is located in front of the brainstem, contralaterally to the parent vertebral artery. We describe the surgical technique for safe approach.

METHOD

Cadaveric dissection performed by the authors, provided comprehensive understanding of relevant anatomy. Intraoperative photos and videos show clipping of the aneurysm using a combined midline and far-lateral suboccipital craniotomy with a para-condylar extension. The literature reviews potential complications.

CONCLUSION

This combined approach allows safe clipping of such PICA aneurysms.

Sequential Extradural Release of the V3 Vertebral Artery to Facilitate Intradural V4 Vertebral Artery Reanastomosis: Feasibility of a Novel Revascularization Technique

BACKGROUND

Revascularization of the intradural vertebral artery (VA) usually involves V3-V4 bypass using an interposition graft. The interposition of a graft increases surgical time, adds risks, and requires 2 suture lines.

OBJECTIVE

To assess the feasibility of an excision-reanastomosis of V4 by sequentially releasing V3.

METHODS

Twenty specimens were prepared for surgical simulation of a far-lateral approach. The third and fourth segments of the VA were exposed through the far-lateral approach bilaterally. The V3 segment was divided into three subsegments: (1) V3 f : from entry to C1 transverse foramen to the point of exit from C1 transverse foramen; (2) V3 s : from V3 f to the distal point of V3 within the sulcus arteriosus; and (3) V3 d : from point V3 leaves the sulcus arteriosus to its dural entrance. After transecting the VA 2 mm proximal to the posterior inferior cerebellar artery origin, each subsegment was released sequentially. We measured the lengths obtained before and after releasing each segment by pulling the VA along its main axis to recreate a V3-V4 excision-reanastomosis.

RESULTS

The V3 could not be effectively mobilized without release. When totally released, an average length of 13.15 mm was available for completing V3-V4 reanastomosis.

CONCLUSION

Complete release of V3 from all its adhesions in its extracranial course can provide an average length of 13.15 mm for excision-reanastomosis. The present study shows the anatomic feasibility of the use of V3 segment in primary anastomosis after excision of a diseased segment of the intradural VA, laying the basis for future clinical application.

Partial Transcondylar Approach for Ventral Foramen Magnum Neurenteric Cyst: 2-Dimensional Operative Video

The anterior foramen magnum area, ventral to the brainstem is one of the most difficult regions to access surgically, and the extent of osseous drilling through the far-lateral or transcondylar approach should be planned in each case based on the tumor extension.1,2 This video, reproduced after informed consent of the patient, demonstrates a case of a ventral foramen magnum neurenteric cyst surgically treated using the partial transcondylar approach. A 27-yr-old woman presented with gait disturbance, oscillopsia, and transient arm numbness. Neuroimaging revealed a ventral foramen magnum cystic tumor involving the basilar and bilateral vertebral arteries. The tumor extended inferiorly from the middle clivus to the C1 level, and occupied the whole premedullary cistern compressing the bilateral lower cranial nerves. The left partial transcondylar approach was performed with drilling the condylar fossa, superior part of the occipital condyle, C1 posterior arch, and posterior part of the jugular process to achieve the sufficient surgical view from the inferolateral side. The drilling of the occipital condyle was minimized so that the articular facet of the occipital condyle was preserved. The tumor on the bilateral side was completely removed as enabled by the sufficient surgical field without new neurological deficits. Three-dimensional reconstructed images based on the postoperative computed tomography scans demonstrated the appropriate extent of the osseous drilling.

Isolated Tuberculoma Mimicking Foramen Magnum Meningioma in the Absence of Primary Tuberculosis: A Case Report

Central nervous system tuberculosis is a devastating complication of systemic tuberculosis. Intradural extramedullary (IDEM) tuberculoma at the foramen magnum is rare, and mimics en plaque meningioma. We report the case of a 53-year-old woman who presented with dysesthesia of the tongue and lower cranial nerve (CN) palsy, with onset 4 months prior to admission. The neurologic examination revealed left upper-limb weakness and hypoesthesia on the sole and dorsum of the left foot. Other physical examinations revealed no features of tubercular infection. Laboratory investigations likewise showed no signs of infection or inflammation. Magnetic resonance imaging of the brain showed an IDEM mass originating from the left intradural surface at the foramen magnum extending to the C2 segment and compressing the brainstem and upper cervical cord. The mass was isointense/hypointense on T1- and T2-weighted images and homogeneously-enhanced on postcontrast images. The lesion also exhibited the dural-tail sign and was preoperatively diagnosed as en plaque meningioma. The patient underwent surgery via the left transcondylar fossa approach with partial laminectomy of the atlas. Intraoperatively, the mass exhibited a dural origin and encased the vertebral artery and lower CNs, with strong adhesions. While the histopathological study of the mass was strongly suggestive of tuberculoma with multifocal granulomas, caseous necrosis, and Langerhans giant cells, extensive diagnostic studies failed to detect Mycobacterium tuberculosis itself. Although the patient had recurrence with multisystem involvement, she responded well to antitubercular treatment. IDEM tuberculoma of the foramen magnum may present as en plaque meningioma. Histopathology is required for a definitive diagnosis. Prompt surgical resection and decompression with adequate antitubercular treatment yield better neurological outcomes.

A case report of surgical management of hemangiopericytoma at the foramen magnum

Background:

Hemangiopericytoma (HPC) is a highly vascularized mesenchymal tumor known for its high rates of recurrence and metastasis. The extent of tumor removal is known to be the most trustful prognostic factor. Skull base HPCs are challenging to treat because of the difficulty of the surgical approach and proximity to vital vascular and neuronal structures. We successfully treated a case of HPC at the ventral foramen magnum through surgical gross tumor removal via a far-lateral transcondylar approach.

Case Description:

A 38-year-old male complained of neck pain and bilateral paresthesia of his shoulders for 2 months, for which he was referred to our hospital. A magnetic resonance image (MRI) showed a 20 mm diameter mass at the ventral foramen magnum, which compressed his medulla oblongata. The tumor was gross totally removed via a far-lateral transcondylar approach. During the surgery, marked bleeding disturbed the surgical field until the main feeding artery from the direction of the dura mater was coagulated and cut. A relatively wide surgical field and a transcondylar approach were helpful to control the bleeding. The pathological examination revealed the tumor to be a HPC. After an uneventful recovery period of 9 days, the patient was discharged without neurological sequelae.

Conclusion:

We successfully and completely removed an HPC near the foramen magnum, employing a wide surgical field and a transcondylar approach to help control bleeding. When the tumor is suspected preoperatively to be a hemangiocytoma or vascular-rich tumor, a surgical approach that can secure a wide surgical field should be selected.