Comparison of microscopic and endoscopic approaches to the cerebellopontine angle

Pain Outcomes Following Endoscopic Microvascular Decompression for Trigeminal Neuralgia Based on Vascular Compression Type

Background  Arterial compression of the trigeminal nerve at the root entry zone has been the long-attributed cause of compressive trigeminal neuralgia despite numerous studies reporting distal and/or venous compression. The impact of compression type on patient outcomes has not been fully elucidated. Objective  We categorized vascular compression (VC) based on vessel and location of compression to correlate pain outcomes based on compression type. Methods  A retrospective video review of 217 patients undergoing endoscopic microvascular decompression for trigeminal neuralgia categorizing VC into five distinct types, proximal arterial compression (VC1), proximal venous compression (VC2), distal arterial compression (VC3), distal venous compression (VC4), and no VC (VC5). VC type was correlated with postoperative pain outcomes at 1 month ( n  = 179) and last follow-up (mean = 42.9 mo, n  = 134). Results  At 1 month and longest follow-up, respectively, pain was rated as "much improved" or "very much improved" in 89 69% of patients with VC1, 86.6 and 62.5% of patients with VC2, 100 and 87.5% of patients with VC3, 83 and 62.5% of patients with VC4, and 100 and 100% of patients with VC5. Multivariate analysis demonstrated VC4 as a significant negative of predictor pain outcomes at 1 month, but not longest follow-up, and advanced age as a significant positive predictor. Conclusion  The degree of clinical improvement in all types of VC was excellent, but at longest follow-up VC type was not a significant predictor out outcome. However distal venous compression was significantly associated with worse outcomes at 1 month.

How I do it: endoscopic microvascular decompression for hemifacial spasm associated with anterior inferior cerebellar artery-posterior inferior cerebellar artery common trunk

BACKGROUND

Multiple vessels from the anterior inferior cerebellar artery-posterior inferior cerebellar artery common trunk (APC) variation of the posterior circulation can cause hemifacial spasm (HFS).

METHOD

Endoscopic microvascular decompression (eMVD) was performed using 0° and 30° endoscopes through a retrosigmoid keyhole. The root exit zone (REZ) was decompressed by transpositioning the offending anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) arising from the APC under excellent endoscopic view.

CONCLUSION

eMVD is an advanced, minimally invasive and reliable technique to resolve the neurovascular conflict (NVC) in HFS due to offenders from APC.

Fully Endoscopic Retrosigmoid Approach for Cerebellopontine Angle Tumors

BACKGROUND

Fully endoscopic or endoscope-controlled approaches are essentially keyhole approaches in which rigid endoscopes are the sole visualization tools used during the whole procedure. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Fully endoscopic retrosigmoid approach for cerebellopontine angle tumors is a minimally invasive approach that is not routinely practiced by neurosurgeons, with few series published so far. Unfamiliarity with the technique, steep learning curve, and concerns about inadequate exposure, neurovascular injury, and decreased visibility may explain this fact. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic retrosigmoid approach and present an overview of the published series.

METHODS

From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases undergoing fully endoscopic retrosigmoid approach for cerebellopontine angle tumors were retrieved and analyzed. The pertinent literature was also reviewed.

RESULTS

The surgical technique of the fully endoscopic retrosigmoid approach was formulated.

CONCLUSION

The endoscopic technique has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results.

Microsurgical anatomy and pathoanatomy of the outer arachnoid membranes in the cerebellopontine angle: cadaveric and intraoperative observations

PURPOSE

The cerebellopontine angle (CPA) is a frequent region of skull base pathologies and therefore a target for neurosurgical operations. The outer arachnoid is the key structure to approach the here located lesions. The goal of our study was to describe the microsurgical anatomy of the outer arachnoid of the CPA and its pathoanatomy in case of space-occupying lesions.

METHODS

Our examinations were performed on 35 fresh human cadaveric specimens. Macroscopic dissections and microsurgical and endoscopic examinations were performed. Retrospective analysis of the video documentations of 35 CPA operations was performed to describe the pathoanatomical behavior of the outer arachnoid.

RESULTS

The outer arachnoid cover is loosely attached to the inner surface of the dura of the CPA. At the petrosal surface of the cerebellum the pia mater is strongly adhered to the outer arachnoid. At the level of the dural penetration of the cranial nerves, the outer arachnoid forms sheath-like structures around the nerves. In the midline, the outer arachnoid became detached from the pial surface and forms the base of the posterior fossa cisterns. In pathological cases, the outer arachnoid became displaced. The way of displacement depends on the origin of the lesion. The most characteristic patterns of changes of the outer arachnoid were described in case of meningiomas, vestibular schwannomas, and epidermoid cysts of the CPA.

CONCLUSION

The knowledge of the anatomy of the outer arachnoid of the cerebellopontine region is essential to safely perform microsurgical approaches as well as of dissections during resection of pathological lesions.

Case report: Fully endoscopic microvascular decompression for trigeminal neuralgia

Microvascular decompression is safe, effective, and micro-invasive. Due to these advantages, it has become the mainstream treatment for trigeminal neuralgia, glossopharyngeal neuralgia, and hemifacial spasm. Initially, microvascular decompression was performed under a microscope, which limited the light source and visualization capabilities. With the development of endoscopic technology, the endoscope has been used in microvascular decompression, which further improved the visualization range and light source properties. The purpose of the present study was to investigate the efficacy of fully endoscopic microvascular decompression for the treatment of trigeminal neuralgia. In total, three patients with trigeminal neuralgia who underwent fully endoscopic microvascular decompression were evaluated. After surgery, the facial pain of all patients was significantly relieved. In addition, there were no obvious postoperative complications and no recurrence after 6 months of follow-up. These excellent surgical outcomes indicate that fully endoscopic microvascular decompression is an effective and safe method for the treatment of trigeminal neuralgia. Furthermore, it also shows that the endoscope presents advantages for use in microvascular decompression.

ACR Appropriateness Criteria® Cranial Neuropathy: 2022 Update

Cranial neuropathy can result from pathology affecting the nerve fibers at any point and requires imaging of the entire course of the nerve from its nucleus to the end organ in order to identify a cause. MRI with and without intravenous contrast is often the modality of choice with CT playing a complementary role. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Combined endoscopic and exoscopic resection of intracranial epidermoid cysts

OBJECTIVE

This article aims at introducing an endoscopic-exoscopic technique for the resection of epidermoid cysts.

METHODS

We retrospectively analyzed the intracranial epidermoid cysts patients who received whole course combined endoscopic and exoscopic resection between 2017 and 2020 at our institution, to explore the benefit of combined endoscopic and exoscopic resection of intracranial epidermoid cysts and evaluated the clinical utility of endoscopic-exoscopic technique.

RESULTS

A total of 17 patients were enrolled in the study. Of all patients, 6 patients (6/17, 35.3%) underwent total resection, 10 patients (10/17, 58.8%) underwent subtotal resection (residual capsule and/or) and 1 patient (1/17, 5.9%) underwent partial resection. Postoperative surgical complications were seen in 3 patients (3/17, 17.6%), including intracranial infection in 2 patients （2/17, 11.8%） , and a delayed postoperative hematoma observed in the seventh day after operation for 1 patient (1/17, 5.9%), who was treated in a conservative manner and recovered smoothly from the hemorrhage. The median follow-up time was 33.3 months (range 14.5-54.5 months). During the follow-up period, there was no recurrence of the tumors that received total resection. 2 patients developed residual tumor regrowth but did not show any symptom therefore no further surgery was required.

CONCLUSIONS

Endoscopic-exoscopic technique is safe and efficient in the resection of intracranial epidermoid cysts with panoramic views and superior maneuverability. With further development and accumulation of practical experiences, the endoscopic-exoscopic technique can also be applied in the resection of other intracranial tumors.

Association study of the pneumatization degree of mastoid air cells and postoperative complications after microvascular decompression in hemifacial spasm

BACKGROUND

This study aimed to analyse the association between the degree of pneumatization of mastoid air cells (MACs) and postoperative complications after microvascular decompression in hemifacial spasm.

METHODS

We retrospectively reviewed 308 patients with hemifacial spasm who underwent surgery at our institute between January 2017 and March 2021. The degree of pneumatization of MACs was classified into four grades (grades 1, 2, 3, and 4) according to method of Han et al. The clinical data of the four grades were analysed and statistically examined.

RESULTS

There were no statistically significant differences between the four grades in terms of the operative time, intraoperative blood loss, and postoperative hospital stay (all, P > 0.05). The incidence of hearing loss was higher in grade 4 MACs (26.56%) than in grades 1 and 2 MACs (5.41% and 2.89%, respectively; P < 0.05). The incidence of facial paralysis was higher in grade 4 MACs (28.13%) than in grades 1 and 2 MACs (5.41% and 9.18%, respectively; P < 0.001). The incidence of intracranial infection was higher in grade 3 MACs (17.65%) than in grade 2 MACs (3.89%) (P < 0.05). All four patients with cerebrospinal fluid leakage belonged to grade 4 MACs. The incidence of cerebrospinal fluid leakage was higher in grade 4 MACs (5.13%) than in grade 2 MACs (P < 0.05).

CONCLUSIONS

This study found that the degree of pneumatization of MACs was closely related to the postoperative complications after MVD surgeries. Well-pneumatized MACs increase the risk of cerebrospinal fluid leakage and intracranial infection. However, insufficient exposure increases the risk of facial paralysis and hearing loss. For patients with well-pneumatized MACs, sufficient surgical exposure is the top priority when locating the bone hole. For those who may have a latent MAC opening, preventive occlusion should be considered.

Endoscope-assisted microsurgical retrosigmoid approach to the lateral posterior fossa: Cadaveric model and a review of literature

Background:

The advancement of endoscopic techniques in the past decade has improved the surgical management of cerebellopontine angle (CPA) tumors. Endoscope-assisted microsurgery improves the ability to evaluate the extent of resection, achieve safe tumor resection and reduce the risk of surgery-related morbidity.

Methods:

In this study, we used a cadaveric model to demonstrate a step by step endoscope-assisted microsurgery of the retrosigmoid approach to the lateral posterior fossa.

Results:

Retrosigmoid craniotomies were performed on four latex-injected cadaver heads (eight CPAs). Microsurgical exposures were performed to identify neurovascular structures in each segment. 0° and 30° rigid endoscope lenses were subsequently introduced into each corridor and views were compared in this manner. The endoscopic images were compared with the standard microscopic views to determine the degree of visualization with each technique. In each case, better visualization was provided by both the 0° and 30° endoscope lenses. Endoscopic views frequently clarified neurovascular relationships in obscured anatomic regions.

Conclusion:

Endoscope-assisted microsurgery could allow better visualization of various regions of the posterior fossa. Surgical planning for posterior fossa lesions should include consideration of this combined approach.

Fully endoscopic versus microscopic vascular decompression for hemifacial spasm: a retrospective cohort study

INTRODUCTION

Microvascular decompression (MVD) is the preferred surgical method for hemifacial spasm (HFS). The purpose of this study was to analyze the effectiveness and safety of fully endoscopic MVD for HFS relative to microscopic MVD.

MATERIAL AND METHODS

The retrospective study was conducted on HFS patients who underwent microscopic or fully endoscopic MVD from January 2018 to March 2019. All patients were treated at a single institution and by a single surgeon. Patients were divided into two groups based on the surgical method, and clinical data were then compared between groups.

RESULTS

A total of 116 patients, including 54 cases who received fully endoscopic MVD (E group) and 62 cases who received microscopic MVD (M group), were included in this study. Follow-up efficacy did not differ significantly between groups, with total effective rates of 88.9% in the E group and 90.3% in the M group. When postoperative complications were compared individually, there were no statistically significant differences between the two groups; however, the E group had a higher total incidence of complications than the M group (48.1% vs. 29.0%, P = 0.034).

CONCLUSION

Although both fully endoscopic and microscopic MVD for HFS achieved good efficacy, the former method had a higher total incidence of complications. Based on the results of this study, there is no evidence that a microscope can be replaced by a full endoscope in MVD for HFS.

Fully Endoscopic Resection of an Epidermoid Cyst of the Cerebellopontine Angle: Bilateral Resection via a Unilateral Approach

BACKGROUND AND IMPORTANCE

Epidermoid cysts are rare, benign intracranial neoplasms that typically arise at the cerebellopontine angle (CPA) and can be extensive lesions that intricately involve many critical neurovascular structures. We describe the case of a patient who presents with the classic picture of CPA epidermoid cyst and describe the value of the 4K endoscope for resection, which is illustrated in our accompanying surgical video.

CLINICAL PRESENTATION

The patient presents with headache, nausea, and vomiting accompanied by dizziness and balance issues. Radiographic imaging demonstrated a large lesion highly consistent with epidermoid cyst which involved the left CPA, encircled the basilar artery, and extended to the opposite side. Surgery was planned with a small left-sided retrosigmoid craniotomy with use of a 2-dimensional 4K endoscope to aid in resection, particularly of the contralateral side. This approach was successful with gross total resection apparent at 14-mo follow-up.

CONCLUSION

We describe the use of a fully endoscopic technique from a unilateral approach for resection of a lesion that extended in the CPA bilaterally. Additionally, we highlight the relevant neuroanatomical and neurovascular structures in this highly critical intracranial region which is well-visualized through endoscopy in the associated surgical video.

How I do it: endoscopic microvascular decompression for glossopharyngeal neuralgia

BACKGROUND

Microvascular decompression (MVD) for glossopharyngeal neuralgia (GPN) is associated with high complication and incomplete cure rates because of its poor ability to visualize neurovascular conflicts.

METHOD

Fully endoscopic MVD for GPN was carried out through a retrosigmoid keyhole approach. Neurovascular conflicts were clearly demonstrated with a loop of the posterior inferior cerebellar artery (PICA) under a 30° endoscopic view, and no significant cerebellar retraction was observed. The loop of the PICA was safely decompressed and the perforators were preserved while offering an excellent operative view.

CONCLUSION

Endoscopic MVD is a reliable and minimally invasive method for GPN.

Complication Rates During Endoscopic Microvascular Decompression Surgery Are Low With or Without Petrosal Vein Sacrifice

OBJECTIVE

Endoscopic-microvascular decompression (E-MVD) is a well-described treatment for trigeminal neuralgia (TGN), but there has been debate on the safety of intraoperative sacrifice of the petrosal vein (PV) due to concern for subsequent venous insufficiency. Our objective was to investigate the risk of PV sacrifice during E-MVD in TGN and subsequent postoperative complications and pain outcomes.

METHODS

5 five-year review yielded 201 patients who underwent MVD for TGN. PV sacrifice, vascular compressive anatomy, and postoperative complications attributable to venous insufficiency were analyzed. Preoperative and postoperative pain outcomes were analyzed.

RESULTS

PV was sacrificed in 118 of 201 (59%) of patients, with 43 of 201 (21%) patients undergoing partial sacrifice versus 75 of 201 (37%) with complete sacrifice. No cases of venous infarction, cerebellar swelling, or fatal complications were noted in either cohort. Non-neurologic complications occurred in 1.69% (2 of 118) of patients with PV sacrifice and 0% (0 of 83) of patients with PV preservation. Neurologic deficits (facial palsy, conductive hearing loss, gait instability, memory deficit) occurred in equal proportions in PV preservation and sacrifice groups (2.41% vs. 1.69%) Overall, 87.3% (145 of 166) patients reported their pain as "very much improved" or "much improved" at 1 month, and no difference between groups was identified.

CONCLUSIONS

This study did not find higher complication rates in patients undergoing petrosal vein sacrifice during E-MVD for trigeminal neuralgia. In this series where petrosal vein was sacrificed only 59% of the time, it appears to be a safe technique, but larger studies will be needed to determine true incidence of complications after PV sacrifice.

Flexible endoscopic assistance in the surgical management of vestibular schwannomas

Endoscopic-assisted techniques have extensively been applied to vestibular schwannoma (VS) surgery allowing to increase the extent of resection, minimize complications, and preserve facial nerve and auditory functions. In this paper, we retrospectively analyze the effectiveness of flexible endoscope in the endoscopic-assisted retrosigmoid approach for the surgical management of VS of various sizes. The authors conducted a retrospective analysis on 32 patients who underwent combined microscopic and flexible endoscopic resection of VS of various sizes over a period of 16 months. Flexible endoscopic-assisted retrosigmoid approach was performed in all cases, and in 6 cases, flexible and rigid endoscopic control were used in combination to evaluate the differences between the two surgical instruments. The surgical results were additionally compared with a previous case series of 141 patients operated for VS of various sizes without endoscopic assistance. Gross-total resection was achieved in 84% of the cases and near-total resection was accomplished in the rest of them. Excellent or good facial nerve function was observed in all except one case with a preoperative severe facial palsy. Hearing preservation surgery (HPS) was attempted in 11 cases and accomplished in 9 (81.8%). A tumor remnant was endoscopically identified in the fundus of the IAC in all cases (100%). Endoscopic assistance increased the rate of total removal and no intrameatal residual tumor was seen at radiological follow-up. Comparative analysis with a surgical cohort of patients operated with the sole microsurgical technique showed a significative association between endoscopic assistance and intracanalicular extent of resection. Combined microsurgical and flexible endoscopic assistance provides remarkable advantages in the pursuit of maximal safe resection of VS and preservation of facial nerve and auditory functions, minimizing the risk of post-operative complications.

Minimally Invasive Endoscopic Retrosigmoid Approach to the Cerebellopontine Angle Using a Novel Surgical Instrument: A Cadaveric Study

OBJECTIVES

In this study, we aimed to describe how endoscopes show the neural and vascular structures at the cerebellopontine angle (CPA) through a minimal craniotomy in a well-described anatomic point in the retrosigmoid region and at the same time, evaluate the endoscopic anatomic exposure and maneuverability. We planned to use the new surgical instrument (endoscope cannula), which we designed on fresh frozen cadavers to simulate a real surgical procedure.

MATERIALS AND METHODS

The surgical procedure was planned to be performed on 20 sides of 10 fresh cadaver heads. The distance between the asterion and mastoid process was determined, and the midpoint was then marked. From this midpoint, a craniotomy 2 cm in size was posteriorly made. The endoscope cannula together with 0° or 30° endoscopes was inserted to capture the panoramic views of the neurovascular structures in CPA. Endoscopic anatomic exposure and maneuverability were evaluated using 0° and 30° endoscopes with/without the endoscope cannula.

RESULTS

The surgeon could easily use both hands during the surgical simulation, and maneuverability was seen to increase in CPA with the use of the endoscope cannula.

CONCLUSION

The surgeon can work actively with both hands when the endoscopes and the endoscope cannula are used together. We believe that owing to this, the surgeon's maneuverability would increase and a more effective minimally invasive endoscopic retrosigmoid surgery would ensue.

The microneurosurgical anatomy legacy of Albert L. Rhoton Jr., MD: an analysis of transition and evolution over 50 years

The authors chronologically categorized the 160 original articles written by Dr. Rhoton and his fellows to show why they selected their themes and how they carried out their projects. The authors note that as neurosurgery progresses and new techniques and approaches are developed, accurate and safe treatment will depend upon continued clarification of microsurgical anatomy.

Flexible Endoscopic-Assisted Microsurgical Radical Resection of Intracanalicular Vestibular Schwannomas by a Retrosigmoid Approach: Operative Technique

The efficacy of endoscopic techniques in the surgical management of intracanalicular vestibular schwannomas (ICVSs) has been underlined in recent studies. An endoscopic- assisted retrosigmoid approach (EARSA) appears to be particularly suitable for achieving complete resection of an ICVS. In this study, we describe the surgical treatment of 3 cases of ICVS with an EARSA, highlighting the advantages and limitations of flexible endoscopy in accomplishing a safe radical resection with hearing preservation. Three patients with an ICVS underwent surgery via a flexible endoscopic-assisted microneurosurgical retrosigmoid approach. Flexible endoscopic assistance allowed the identification of residual tumor located in the most lateral portion of the fundus of the internal auditory canal in all cases. Endoscopic controls and further microsurgical resection were attempted, and complete surgical resection was achieved in all cases without the occurrence of postoperative facial or auditory nerve dysfunction. Flexible endoscopy appears to be particularly useful and safe in the surgical management of ICVS by microneurosurgery via an EARSA.

How I do it: endoscopic microvascular decompression for hemifacial spasm associated with the vertebral artery

BACKGROUND

Microvascular decompression (MVD) of hemifacial spasm (HFS) associated with the vertebral artery (VA) shows higher rates of incomplete cure and complications compared to non-VA-related HFS.

METHOD

Purely endoscopic MVD for VA-associated HFS via a retrosigmoid keyhole was performed. Neurovascular conflicts by a directly offending artery and VA around the root exit zone of the facial nerve were clearly demonstrated under 30° endoscopic view without significant cerebellar retraction. The VA and directly offending artery were safely transposed with preservation of perforators under excellent view.

CONCLUSION

Endoscopic MVD offers reliable decompression for VA-associated HFS with minimal invasiveness.

Microsurgical and endoscopic approaches to the pulvinar

OBJECTIVE

Approaches to the pulvinar remain challenging because of the depth of the target, surrounding critical neural structures, and complicated arterial and venous relationships. The purpose of this study was to compare the surgical approaches to different parts of the pulvinar and to examine the efficacy of the endoscope as an adjunct to the operating microscope in this area.

METHODS

The pulvinar was examined in 6 formalin-fixed human cadaveric heads through 5 approaches: 4 above and 1 below the tentorium. Each approach was performed using both the surgical microscope and 0° or 45° rigid endoscopes.

RESULTS

The pulvinar has a lateral ventricular and a medial cisternal surface that are separated by the fornix and the choroidal fissure, which wrap around the posterior surface of the pulvinar. The medial cisternal part of the pulvinar can be further divided into upper and lower parts. The superior parietal lobule approach is suitable for lesions in the upper ventricular and cisternal parts. Interhemispheric precuneus and posterior transcallosal approaches are suitable for lesions in the part of the pulvinar forming the anterior wall of the atrium and adjacent cisternal part. The posterior interhemispheric transtentorial approach is suitable for lesions in the lower cisternal part and the supracerebellar infratentorial approach is suitable for lesions in the inferior and medial cisternal parts.

The microscope provided satisfactory views of the ventricular and cisternal surfaces of the pulvinar and adjacent neural and vascular structures. The endoscope provided multi-angled and wider views of the pulvinar and adjacent structures.

CONCLUSIONS

A combination of endoscopic and microsurgical techniques allows optimal exposure of the pulvinar.

The endoscopic anatomy of the middle ear approach to the fundus of the internal acoustic canal

OBJECTIVE The application of the endoscope in the lateral skull base increases the importance of the middle ear cavity as the corridor to the skull base. The aim of this study was to define the middle ear as a route to the fundus (lateral end) of the internal acoustic canal and to propose feasible landmarks to the fundus. METHODS This was a cadaveric study; 34 adult cadaveric temporal bones and 2 dry bones were dissected with the aid of the endoscope and microscope to show the anatomy of the transcanal approach to the middle ear and fundus of the internal acoustic canal. RESULTS In the middle ear cavity, the cochleariform process is one of the key landmarks for accessing the fundus of the internal acoustic canal. The triangle formed by the anterior and posterior edges of the overhang of the round window and the cochleariform process provides a landmark to start drilling the bone to access the fundus of the internal acoustic canal. CONCLUSIONS The external acoustic canal and middle ear cavity combined, using endoscopic guidance, can provide a route to the fundus of the internal acoustic canal. A triangular landmark crossing the promontory has been described for reaching the meatal fundus. This transcanal approach requires an understanding of the relationship between the middle ear cavity and the fundus of the internal acoustic canal and provides a potential new area of cooperation between otology and neurosurgery for accessing pathology in this and the bordering skull base.

Comparison of endoscope- versus microscope-assisted resection of deep-seated intracranial lesions using a minimally invasive port retractor system

OBJECT

Tubular brain retractors may improve access to deep-seated brain lesions while potentially reducing the risks of collateral neurological injury associated with standard microsurgical approaches. Here, microscope-assisted resection of lesions using tubular retractors is assessed to determine if it is superior to endoscope-assisted surgery due to the technological advancements associated with modern tubular ports and surgical microscopes.

METHODS

Following institutional approval of the tubular port, data obtained from the initial 20 patients to undergo transportal resection of deep-seated brain lesions were analyzed in this study. The pathological entities of the resected tissues included metastatic tumors (8 patients), glioma (7), meningioma (1), neurocytoma (1), radiation necrosis (1), primitive neuroectodermal tumor (1), and hemangioblastoma (1). Surgery incorporated endoscopic (5 patients) or microscopic (15) assistance. The locations included the basal ganglia (11 patients), cerebellum (4), frontal lobe (2), temporal lobe (2), and parietal lobe (1). Cases were reviewed for neurological outcomes, extent of resection (EOR), and complications. Technical data for the port, surgical microscope, and endoscope were analyzed.

RESULTS

EOR was considered total in 14 (70%), near total (> 95%) in 4 (20%), and subtotal (< 90%) in 2 (10%) of 20 patients. Incomplete resection was associated with the basal ganglia location (p < 0.05) and use of the endoscope (p < 0.002). Four of 5 (80%) endoscope-assisted cases were near-total (2) or subtotal (2) resection. Histopathological diagnosis, presenting neurological symptoms, and demographics were not associated with EOR. Complication rates were low and similar between groups.

CONCLUSIONS

Initial experience with tubular retractors favors use of the microscope rather than the endoscope due to a wider and 3D field of view. Improved microscope optics and tubular retractor design allows for binocular vision with improved lighting for the resection of deep-seated brain lesions.

Fully Endoscopic Retrosigmoid Vestibular Nerve Section for Refractory Meniere Disease

OBJECTIVE

This study aims to report our results and technical details of fully endoscopic retrosigmoid vestibular nerve section.

DESIGN

A prospective observational study was conducted.

SETTING

A single academic, tertiary institution involving neurosurgery and neurotology.

PARTICIPANTS

Previously diagnosed patients with Meniere disease, refractory to medical therapy, who underwent fully endoscopic vestibular nerve section.

MAIN OUTCOME MEASURES

Postoperative improvement in vertiginous symptoms as well as hearing preservation, based on the American Association of Otolaryngology-Head and Neck Surgeons score and the Gardener and Robertson-Modified Hearing Classification. Facial nerve preservation based on the House-Brackman (HB) score.

RESULTS

Symptoms improved or resolved in 38 of 41 (92.2%) patients with only 1 of 41 (2.4%) reporting worsening symptoms. All 41 patients (100%) had a postoperative HB score of 1/6, demonstrating full facial nerve preservation. Hearing was stable or improved in 34 of 41 (82.9%) patients. Three complications took place for a rate of 7.3%, one cerebrospinal fluid leak, and two wound infections.

CONCLUSION

The fully endoscopic approach to vestibular nerve sections is a safe and effective technique for the treatment of medically refractory Meniere disease. This technique also utilizes smaller incisions, minimal cranial openings, and no cerebellar retraction with improved visualization of the cerebellopontine angle neurovascular structures.

The combined microscopic-endoscopic technique for radical resection of cerebellopontine angle tumors

OBJECT

The combined microscopic and endoscopic technique has shown significant advantages in the management of various lesions through different approaches. Endoscopic-assisted techniques have frequently been applied to cerebellopontine angle (CPA) surgery in the context of minimally invasive craniotomies. In this paper the authors report on the use of the endoscope in the CPA as a tool to increase the extent of resection, minimize complications, and preserve the function of the delicate CPA structures. They also describe a technique of the simultaneous use of the microscope and endoscope in the CPA and dissection of CPA tumors under tandem endoscopic and microscopic vision to overcome the shortcomings of introducing the endoscope alone in the CPA. The reliability of using the microscope alone in dissecting CPA tumors is evaluated, as is the effectiveness of the combined technique in increasing the resectability of various types of CPA tumors.

METHODS

The authors conducted a retrospective analysis of 50 patients who underwent combined microscopic-endoscopic resection of CPA tumors by the senior author over a period of 3 years (February 2011 to February 2014) at Brigham and Women's Hospital, Harvard Medical School. The reliability of the extent of microscopic removal was evaluated with endoscopic exploration. Additional resection was performed with both microscopic and the combined microscopic-endoscopic technique. Endoscopically verified total resection was validated by intraoperative or postoperative MRI. The function of the cranial nerves was evaluated to assess the impact of the combined technique on their function.

RESULTS

A tumor remnant was endoscopically identified in 69% of the 26 patients who were believed to have microscopic total resection. The utilization of the endoscopic visualization and dissection increased endoscopically verified total removal to 38 patients, and 82% of these patients had no sign of residual tumor on postoperative imaging. The technique was most effective with epidermoid tumors. There were a total of 17 new cranial nerve deficits in 10 patients. Preoperative fifth cranial nerve deficits improved in 52% and hearing improved in 29% of patients after surgery.

CONCLUSIONS

This method provides simultaneous microscopic and endoscopic visualization and dissection techniques through skull-base approaches to CPA tumors. It overcomes some of the shortcomings of endoscopic-assisted surgery, further extends the surgical field, and increases the radicality of tumor resection with good functional outcomes.

Auditory brainstem implantation: anatomy and approaches

BACKGROUND

Auditory brainstem implantation at the cochlear nuclei used mainly for neurofibromatosis type 2 patients with bilateral loss of the cochlear nerves has more recently been extended to the inferior colliculus.

OBJECTIVE

To examine the microsurgical and endoscopic anatomy of the cochlear nuclei and inferior colliculus as seen through the translabyrinthine and retrosigmoid approaches used for cochlear nuclei and inferior collicular implantation.

METHODS

Ten cerebellopontine angles of formalin-fixed adult cadaveric heads were examined with the aid of the surgical microscope and endoscope. The ascending auditory pathways between the cochlear nuclei and inferior colliculi and above were examined by the fiber dissection technique.

RESULTS

Both the translabyrinthine and retrosigmoid routes provide sufficient exposure for concurrent tumor removal and implantation at either the cochlear nuclei or inferior colliculus. The position of the inferior colliculus in the auditory pathways and its accessibility in the infratentorial supracerebellar exposure directed through either the translabyrinthine or retrosigmoid approach makes it an alternative site for electrode placement if the cochlear nuclei are not functionally or structurally suitable for implantation. Endoscopic assistance may aid the exposure and electrode placement at either site.

CONCLUSION

The translabyrinthine or retrosigmoid approaches provide access to the cochlear nuclei for implantation and also to the inferior colliculus through the translabyrinthine or retrosigmoid infratentorial supracerebellar route. The endoscope may aid in exposing either site.

Pre-operative image-based segmentation of the cranial nerves and blood vessels in microvascular decompression: Can we prevent unnecessary explorations?

OBJECTIVES

This study was conducted to validate the accuracy of image-based pre-operative segmentation using the gold standard endoscopic and microscopic findings for localization and pre-operative diagnosis of the offensive vessel.

PATIENTS AND METHODS

Fourteen TN and 6 HS cases were randomly selected. All patients had 3T MRI, which included thin-sectioned 3D space T2, 3D Time of Flight and MPRAGE Sequences. Imaging sequences were loaded in BrainLab iPlanNet and fused. Individual segmentation of the affected cranial nerves and the compressing vascular structure was performed by a neurosurgeon, and the results were compared with the microscopic and endoscopic findings by two blinded neurosurgeons. For each case, at least three neurovascular landmarks were targeted. Each segmented neurovascular element was validated by manual placement of the navigation probe over each target, and errors of localization were measured in mm.

RESULTS

All patients underwent retro-sigmoid craniotomy and MVD using both microscope and endoscope. Based on image segmentation, the compressing vessel was identified in all cases except one, which was also negative intraoperatively. Perfect correspondence was found between image-based segmentation and endoscopic and microscopic images and videos (Dice coefficient of 1). Measurement accuracy was 0.45 ± 0.21 mm (mean ± SD).

CONCLUSION

Image-based segmentation is a promising method for pre-operative identification and localization of offending blood vessels causing HFS and TN. Using this method may prevent some unnecessary explorations on especially atypical cases with no vascular contacts. However, negative pre-operative image segmentation may not preclude one from exploration in classic cases of TN or HFS. A multicenter study with larger number of cases is recommended.

Japanese neurosurgeons and microsurgical anatomy: a historical review

Research in microneurosurgical anatomy has contributed to great advances in neurosurgery in the last 40 years. Many Japanese neurosurgeons have traveled abroad to study microsurgical anatomy and played major roles in advancing and spreading the knowledge of anatomy, overcoming their disadvantage that the cadaver study has been strictly limited inside Japan. In Japan, they initiated an educational system for surgical anatomy that has contributed to the development and standardization of Japanese neurosurgery. For example, the Japanese Society for Microsurgical Anatomy started an annual educational meeting in the middle of 1980s and published its proceedings in Japanese every year for approximately 20 years. These are some of the achievements that bring worldwide credit to Japanese neurosurgeons. Not only should Japanese neurosurgeons improve their educational system but they should also contribute to the international education in this field, particularly in Asia.

Endoscopic Resection of Vestibular Schwannomas

Objective To report our results and the technical details of fully endoscopic resection of vestibular schwannomas. Design Prospective observational study. Setting A single academic institution involving neurosurgery and neurotology. Participants Twelve consecutive patients who underwent fully endoscopic resection of a vestibular schwannoma. Main Outcome Measures Hearing preservation, based on the American Association of Otolaryngology-Head and Neck Surgeons (AAO-HNS) score as well as the Gardener and Robertson Modified Hearing Classification (GR). Facial nerve preservation based on the House-Brackmann (HB) score. Results All patients successfully underwent gross total resection. Facial nerve preservation rate was 92% with 11 of 12 patients retaining an HB score of 1/6 postoperatively. Hearing preservation rate was 67% with 8 of 12 patients maintaining a stable AAO-HNS grade and GR score at follow-up. Mean tumor size was 1.5 cm (range: 1-2 cm). No patients experienced postoperative cerebrospinal fluid leak, infection, or cranial nerve palsy for a complication rate of 0%. Mean operative time was 261.6 minutes with an estimated blood loss of 56.3 mL and average length of hospital stay of 3.6 days. Conclusion A purely endoscopic approach is a safe and effective option for hearing preservation surgery for vestibular schwannomas in appropriately selected patients.