Single burr hole rigid endoscopic third ventriculostomy and endoscopic tumor biopsy: What is the safe displacement range for the foramen of Monro?

Good clinical outcomes and the necessity of CSF drainage in patients undergoing simultaneous biopsy and endoscopic third ventriculostomy in the region of pineal tumors: A systematic review and meta-analysis

INTRODUCTION

Due to their delicate and deep-seated location, tumors in the pineal region of the brain pose exceptional challenges in neurosurgical management. Highly precise procedures have become crucial to address these complexities, such as the simultaneous performance of biopsy and endoscopic third ventriculostomy (ETV). Our aim was to assess the feasibility, safety, and efficacy of simultaneous biopsy and ETV for treating patients with pineal region tumors.

METHODS

Medline, Embase, and Web of Science were searched for English studies from January 2000 to February 2024, following Cochrane and PRISMA guidelines. Eligible studies encompassed a minimum of four patients and examined at least one of the following outcomes: good clinical outcomes and the necessity of shunt placement. Single proportion analysis with 95% confidence intervals was conducted under a random-effects model, employing the I2 statistic to assess heterogeneity. Additionally, publication bias was evaluated using the ROBINS-I tool.

RESULTS

After a meticulous selection process, eighteen studies involving 390 patients were included in the analysis. Overall, good clinical outcomes were observed in 131 out of 147 patients, representing a rate of 92 % (95 % CI: 84 % to 100 %, I2 = 62 %) through random effects analysis. Subgroup analysis showed that children exhibited a notably high rate of good clinical outcomes, reaching 100 % (95 % CI: 96 % to 100 %, I2 = 0 %). Regarding the need for shunt placement, out of the 356 patients assessed, only 39 required shunt placement, yielding a rate of 8 % (95 % CI: 4 % to 12 %, I2 = 63 %). Further sub-analyses indicated shunt requirement rates of 12 % for children and 3 % for adults. Specifically focusing on adults, data from 46 patients who underwent biopsy revealed a success rate of 84 % (95 % CI: 62 % to 100 %, I2 = 81 %). Remarkably, no major complications were reported among adults, resulting in a rate of 0 % (95 % CI: 0 % to 6 %, I2 = 0 %). Additionally, low rates of mortality related to the procedure were observed in adults, with two deaths recorded among the 46 patients analyzed, resulting in a mortality rate of 1 % (95 % CI: 0 % to 7 %, I2 = 0 %).

CONCLUSION

In conclusion, our study aimed to assess the feasibility, safety, and efficacy of performing simultaneous biopsy and ETV for patients with pineal region tumors. We meticulously examined clinical aspects and patient outcomes, including good clinical outcomes, the requirement for shunt placement after ETV, biopsy success rates, mortality, and complications.

Neuroendoscopic transventricular transchoroidal approach for access to the posterior zone of the third ventricle or pineal region

The endoscopic transventricular transchoroidal approach facilitates entry into the posterior part of the third ventricle, allowing a visualization field from the foramen of Monro to the pineal region through this anatomical corridor. Combined surgery to treat the target lesion and possible endoscopic third ventriculostomy (ETV) can be performed through a single burr hole. A detailed description of this surgical technique is given, and a series of cases from our center is presented. This retrospective study included patients with lesions in the pineal region or posterior zone of the third ventricle who underwent surgery between 2004 and 2022 in our center for tumor biopsy or endoscopic cyst fenestration. In nine cases, the transchoroidal approach was performed. Demographic and clinical variables were collected: sex, age at diagnosis, clinical presentation, characteristics of the lesion, pathological diagnosis, characteristics of the procedure, complications, subsequent treatments, evolution, follow-up time, and degree of success of the endoscopic procedure. The mean and range of the quantitative variables and frequency of the qualitative variables were analyzed, together with the statistical significance (p < 0.05). Surgical planning was carried out by performing a preoperative MRI, calculating the ideal entry point and trajectory for each case. The preoperative planning of the surgical technique is described in detail. Of our sample, 55.6% were women, with a mean age of 35 years (7-78). The most common clinical presentation was intracranial hypertension (55.6%), with or without a focus. Eight patients presented hydrocephalus at diagnosis. The most frequent procedure was endoscopic biopsy with ETV (66.7%). The pathological diagnosis varied widely. Procedure-related complications included one case of self-limited bleeding of the choroidal fissure at its opening and one intraventricular hemorrhage due to tumor bleeding in the postoperative period. Non-procedure-related complications comprised two ETV failures and one case of systemic infection, while late complications included one case of disease progression and one case of radionecrosis. Four patients died, one due to poor neurological evolution after post-surgical tumor bleeding and three due to causes unrelated to the procedure. The rest of the patients had a favorable evolution and were asymptomatic or stable. The transchoroidal approach through a single burr hole is a feasible and safe option for access to the posterior part of the third ventricle. Proper planning of each case is necessary to avoid complications.

Endoscopic extended transforaminal approach (medial subchoroid) as an alternative to the classical transchoroidal approach: Technical note

The extended transforaminal endoscopic approaches allows visualization and manipulation of the middle and posterior third of the III ventricle. In selected cases where the venous anatomy is favorable, the medial subchoroidal approach can be performed as an alternative to the classic transchoroidal approach (via trans-taenia fornicis) with increased protection over the fornix and without the need to sacrifice the septal vein. We present a 14-year-old male with history of Neurofibromatosis type 1 referred for two weeks of clinical evolution with headache, dizziness, gait instability and appearance of a right VI nerve palsy. Magnetic resonance imaging showed obstructive tri-ventricular hydrocephalus due to stenosis of the aqueduct of Sylvius with suspicion of an underlying tumor. An endoscopic surgical procedure was performed through a single approach with III cisternostomy and resection of the tissue that produced the stenosis. The anatomopathological diagnosis showed reactive glial tissue with no signs of malignancy. In conclusion, the medial subchoroidal approach is a plausible alternative in the endoscopic approach to the III ventricle structures in a safe and comfortable manner.

Neuroendoscopy in the management of pineal region tumours in children

INTRODUCTION

Pineal region tumours (PRTs) are more common in children and represent a wide variety of lesions. The practise of a radiation test dose is obsolete and a biochemical/histological diagnosis is recommended before further therapy. Many patients present with hydrocephalus. Advances in neuroendoscopic techniques have allowed safe and effective management of this obstructive hydrocephalus with an opportunity to sample cerebrospinal fluid (CSF) and obtain tissue for histopathology. Definitive surgery is required in less than a third. Endoscopic visualisation and assistance is increasingly used for radical resection, where indicated.

METHODOLOGY

Our experience of endoscopic surgery for paediatric PRTs from 2002 to 2021 is presented. All patients underwent MRI with contrast. Serum tumour markers were checked. If negative, endoscopic biopsy and endoscopic third ventriculostomy (ETV) were performed; and CSF collected for tumour markers and abnormal cells. For radical surgery, endoscope-assisted microsurgery procedures were performed to minimise retraction, visualise the extent of resection and confirm haemostasis.

RESULTS

M:F ratio was 2:1. The median age of presentation was 11 years. Raised ICP (88.88%) was the commonest mode of presentation. Nineteen patients had pineal tumours, one had a suprasellar and pineal tumour, one had disseminated disease, while six had tectal tumours. The ETB diagnosis rate was 95.45%, accuracy rate was 83.3% and ETV success rate was 86.96%.

CONCLUSION

Neuroendoscopy has revolutionised the management of paediatric PRTs. It is a safe and effective procedure with good diagnostic yield and allows successful concurrent CSF diversion, thereby avoiding major surgeries and shunt implantation. It is also helpful in radical resection of lesions, where indicated.

Concomitant, Single Burr Hole Endoscopic Third Ventriculostomy and Tumor Biopsy for Pineal Lesions: Feasibility, Safety, and Benefits

Obtaining a prompt diagnosis, avoiding indwelling ventriculoperitoneal shunt, and enhancing the predictive value of pathologic examinations are only some of the advantages conferred by a simultaneous third ventriculostomy and tumor biopsy in patients with pineal region tumors. The objective of this study was to retrospectively search the literature on concomitant, single burr hole endoscopic third ventriculostomy (ETV) and tumor biopsy (TB) for pineal region tumors and to analyze the feasibility, surgical safety, and benefits of these 2 combined procedures. Consequently, a comprehensive, systematic literature search was performed in compliance with the updated PRISMA 2020 guidelines within electronic databases MEDLINE/PubMed, EMBASE, PLOS, and Cochrane Library. Statistical analysis was performed with IBM SPSS 28.0.1.1(14), using Kendall's and Spearman's tests, with a P < 0.05 considered significant. A total of 25 studies were selected and included in this review, for a total of 368 patients (mean age 20.6 years; range 1-86 years; SD 17.5). More than two-thirds of the procedures were operated with a rigid endoscope and 27.6% were performed with either a flexible endoscope, a combination of the 2, or not otherwise specified. Germinoma represented the most frequent diagnosis (20.1%) followed by astrocytoma (12.9%) and pineocytoma (9.9%). The single-entry approach allowed a correct histologic diagnosis in 88.7% of the examined cases. Summing up, concomitant ETV and TB represent a valuable option for the management of non-communicating hydrocephalus and the initial assessment of pineal region tumors. The histologic confirmation rate was 88.7% in the examined cohort, with only 10% of the biopsies yielding inconclusive results.

The relationship between semantic and episodic memory: evidence from a case of severe anterograde amnesia

It is increasingly being recognized that new declarative, consciously accessible information can be learned in anterograde amnesia, but it is not clear whether this learning is supported by episodic or semantic memory. We report a case of a 55-year-old man who experienced severe amnesia after limited damage to the medial temporal lobe following neurosurgical complications. His general cognitive performance and knowledge of new French words and public events that occurred before and after the onset of amnesia were assessed. Performance remained satisfactory on post-morbid vocabulary and public events, with a drop in performance observed for very recent public events only, while knowledge of very recent vocabulary was comparable to that of the control subjects. The implications of these findings for our understanding of the underlying learning mechanisms are discussed. This is the first report of acquisition of consciously accessible postmorbid knowledge of public events in a patient with severe amnesia.

Single Burr-Hole Extended Transforaminal Approach for Concurrent Endoscopic Surgery in the Third Ventricle Posterior to the Foramen of Monro and Ventriculostomy: Clinical Series and Planning Steps

OBJECTIVE

For endoscopic surgery of third ventricular lesions posterior to the foramen of Monro that frequently require a third ventriculostomy during the same procedure, the extended transforaminal approach (ETFA) through the choroid fissure has been proposed. This study reports clinical results and provides anatomic background and guidelines for individual planning of a single burr-hole approach and a safe transchoroid entry zone.

METHODS

A retrospective review was undertaken of 25 cases of concurrent third ventricle surgery and third ventriculostomy via ETFA. Assessment was made of a safe transchoroidal entry zone on cadavers (6 hemispheres) and of planning guidelines on magnetic resonance imaging showing occlusive hydrocephalus (30 sides).

RESULTS

ETFA was feasible in all 25 cases. The safe transchoroid entry zone was sufficient in 16 cases; in 9 cases, additional transchoroid opening with transection of the anterior septal vein was required without clinical consequences. The anatomic study showed a safe transchoroid entry zone of 5 mm (3-6 mm) for posterior enlargement of the foramen of Monro. Individual planning on magnetic resonance imaging of patients with enlarged third ventricles showed an optimal burr-hole position 22 mm (10-30 mm) lateral to the midline and 8 mm (27 to -23 mm) precoronal; a foramen of Monro diameter of 7 mm (3-11 mm) and a safe transchoroid entry zone of 6 mm (3-12 mm).

CONCLUSIONS

According to our data, concurrent endoscopic surgery of third ventricular lesions posterior to the foramen of Monro and ventriculostomy are feasible through a single burr hole and a transchoroid extension of the transforaminal approach. Precise preoperative planning is recommended for anticipating the individual anatomic nuances.

Resection of a recurrent medulloblastoma in the anterior middle part of the aqueduct with a flexible endoscope: a case report

Resection or biopsy of intraventricular brain tumors using an endoscope has become common, but the limitations of these procedures are not clear. Manipulation to access a tumor that arises from the blind angle of the rigid endoscope, such as the anterior part of the aqueduct, is limited. We report here that we successfully resected a recurrent medulloblastoma in the anterior part of the aqueduct using only a flexible endoscope. This method appears to be suitable for poorly vascularized and suctionable tumors that arise in the blind angle of a rigid endoscope.

Endoscopic Third Ventriculostomy and Simultaneous Tumor Biopsy in Pineal Region Tumors using the "Single Burr Hole" Technique: An Analysis of 34 Cases

Background

Pineal region tumors often present with hydrocephalus. Endoscopic third ventriculostomy (ETV) and simultaneous tumor biopsy remain a minimally invasive procedure offering both diagnostic and therapeutic advantages in the management of these tumors. However, different operative techniques have been described in the literature.

Aim

The aim is to study the ETV success rate, diagnostic rate of simultaneous tumor biopsy, complications, and follow-up of patients of pineal region tumors managed with ETV and simultaneous tumor biopsy using the single burr hole technique.

Methods

The study was performed by retrospectively reviewing the records of patients of pineal region tumors managed by simultaneous ETV and tumor biopsy using a "single burr hole" technique from January 2012 to December 2019.

Results

Thirty-four patients (22 males and 12 females) with a mean age of 28.7 years were analyzed. ETV was successful in relieving hydrocephalus in 29 (87.8%) patients. Three patients needed a ventriculoperitoneal shunt, and one required Ommaya reservoir placement for persistent hydrocephalus. Histological diagnosis was successfully established in 26 (78.8%) patients. There were two procedure-related mortalities. Two patients underwent craniotomy and tumor excision subsequently. Radiotherapy was given to 11 patients, and 9 patients were managed by observation alone. The mean follow-up of our study was 15.8 months.

Conclusions

Simultaneous ETV and tumor biopsy using a single burr hole technique is a safe, minimally invasive procedure for the management of pineal region tumors.

One- vs Two-Burr-Hole Technique for Combined Endoscopic Third Ventriculostomy and Pineal Region Biopsy: Volumetric Analysis of Brain at Risk

BACKGROUND

Pineal region tumors are associated with the ventricular system. Endoscopic third ventriculostomy (ETV) is often performed at the same time as tumor biopsy.

OBJECTIVE

To investigate the volume of brain possibly undergoing injury and forniceal stretching during ETV and tumor biopsy.

METHODS

We performed a retrospective review of preoperative magnetic resonance imagings (MRIs) and computed tomography (CTs) of patients with pineal region masses and used volumetric image-guided navigation to simulate a 1-burr-hole vs a 2-burr-hole approach through the brain parenchyma. We compared the volumes of parenchyma and fornix at the risk of injury.

RESULTS

The ideal entry point for ETV using 2 burr holes was a mean ± standard deviation (SD) of 25.8 ± 6 mm from the midline and 11.4 ± 9 mm behind the coronal suture. The ideal entry point using 2 burr holes for tumor biopsy was 25.7 ± 8 mm from the midline and 53.7 ± 14 mm anterior to the coronal suture. With 1 burr hole, the mean ± SD volume of brain parenchyma at risk was 852 ± 440 mm3. The volume of brain parenchyma at risk with 2 burr holes was 2159 ± 474 mm3 (P < .001; paired t-test). The use of 1 burr hole predisposed the fornix to 14 ± 3 mm of possible stretch, which was minimized with the 2-burr-hole approach.

CONCLUSION

Using 1 burr hole for both the ETV and tumor biopsy is less likely to traumatize the brain parenchyma than using 2 burr holes. However, 1 burr hole predisposes the fornix to stretch injury. We recommend tailoring the entry to each patient according to their anatomy rather than using a 1-size-fits-all approach.

A Steerable Neuroendoscopic Instrument Using Compliant Contact-Aided Joints and Monolithic Articulation

This work presents the design of an articulate neuroendoscopic instrument (ANI), a handheld tool for use in minimally invasive neurosurgery. The instrument consists of a handle and a steerable tube-shaft with a distal end-effector. The design aims to increase the reach of surgeons operating through narrow channels within the center of the brain when approaching multiple targets from a single incision point. The steerable tube-shaft consists of a 1.6- mm notch-tube compliant joint mechanism augmented with contact-aids modeled after a gear geometry. The contact-aid geometry aims to address the performance tradeoff between stiffness, range-of-motion (RoM), and joint compactness for millimeter-scale notched-tube joints; it increases blocking force without sacrificing RoM. Finite element modeling (FEM) was used to refine design features, and the joint stiffness and RoM are assessed experimentally for three prototypes. The joint is incorporated into a tube-shaft instrument, and the assembled tool's stiffness properties are characterized. The prototype was then assessed in a validated neurosurgical simulator. An individual 1.24-mm outer-diameter notch-tube compliant joint with gear contact-aids is capable of 30 deg maximum bending and can sustain a 0.55 N blocking force with 0.5 mm displacement. A functional instrument shaft with a 15.5- mm-long articulating section was constructed from three joints in series with an external flexible stainless-steel sheath. It achieves a 6.7-mm bending radius at 75 deg maximum bending angle. In preclinical testing with an endoscopic third ventriculostomy and endoscopic tumor biopsy (ETV-ETB) simulator, the tool successfully completes the biopsy and fenestration maneuvers from a single burr-hole entry point. The ANI prototype uses contact-aid geometry incorporated into a compliant nitinol notched-tube joint to produce an articulate biopsy instrument for minimally invasive neurosurgical applications.

Continuum Robot With Follow-the-Leader Motion for Endoscopic Third Ventriculostomy and Tumor Biopsy

BACKGROUND

In a combined endoscopic third ventriculostomy (ETV) and endoscopic tumor biopsy (ETB) procedure, an optimal tool trajectory is mandatory to minimize trauma to surrounding cerebral tissue.

OBJECTIVE

This paper presents wire-driven multi-section robot with push-pull wire. The robot is tested to attain follow-the-leader (FTL) motion to place surgical instruments through narrow passages while minimizing the trauma to tissues.

METHODS

A wire-driven continuum robot with six sub-sections was developed and its kinematic model was proposed to achieve FTL motion. An accuracy test to assess the robot's ability to attain FTL motion along a set of elementary curved trajectory was performed. We also used hydrocephalus ventricular model created from human subject data to generate five ETV/ETB trajectories and conducted a study assessing the accuracy of the FTL motion along these clinically desirable trajectories.

RESULTS

In the test with elementary curved paths, the maximal deviation of the robot was increased from 0.47 mm at 30 ° turn to 1.78 mm at 180 ° in a simple C-shaped curve. S-shaped FTL motion had lesser deviation ranging from 0.16 to 0.18 mm. In the phantom study, the greatest tip deviation was 1.45 mm, and the greatest path deviation was 1.23 mm.

CONCLUSION

We present the application of a continuum robot with FTL motion to perform a combined ETV/ETB procedure. The validation study using human subject data indicated that the accuracy of FTL motion is relatively high. The study indicated that FTL motion may be useful tool for combined ETV and ETB.

An anatomical study of the foramen of Monro: implications in management of pineal tumors presenting with hydrocephalus

BACKGROUND

For pineal tumors presenting with hydrocephalus, simultaneous endoscopic third ventriculostomy (ETV) and tumor biopsy is commonly used as the initial step in management. To analyze the restriction which the foramen of Monro poses to this procedure, one must start with a detailed description of the microsurgical anatomy of the foramen in living subjects. However, the orientation and shape of the foramen of Monro make this description difficult with conventional imaging techniques.

METHOD

Virtual reality technology was applied on MRIs on living subject without hydrocephalus, as well as patients with hydrocephalus, to generate precise anatomical models with sub-millimeter accuracy. The morphometry of the foramen of Monro was studied in each group. In addition, displacement of the margins of the foramen was studied in detail for simultaneous ETV and pineal tumor biopsy through a single burr hole.

RESULTS

In 30 normal subjects, the foramen of Monro had oval-shaped openings averaging 5.23 mm². The foramen was larger in people above age 55 (p = 0.007) and on the left side compared to the right (p = 0.002). For patients with clinical presentation of hydrocephalus, the average opening was 32.6 mm². Simulated single burr hole simultaneous ETV and pineal tumor biopsy was performed in 10 specimens. Average displacement of the posterior and anterior margins of the foramen was 5.71 mm and 5.76 mm, respectively. However, maximum displacement reached 9.3 mm posteriorly and 10 mm anteriorly.

CONCLUSIONS

The foramen of Monro is an oval-shaped cylinder that changes in size and orientation in the hydrocephalic patient. If universally applied to all patients regardless of foramen and tumor size, ETV/biopsy can displace structures around the Foramen of Monro up to 1 cm, which can potentially lead to neurological damage. Careful pre-operative assessment is critical to determine if a single burr hole approach is safe.

Clinical Management of Prostate Cancer Metastasis to Pineal Gland: Case Report and Review of Literature

BACKGROUND

Prostate cancer is the most common cancer among American men, with an incidence of approximately 233,000 cases per year. Intracranial metastases are rare and, specifically, metastasis to the pineal gland has only been reported in 2 postmortem cases in the literature.

CASE DESCRIPTION

We present the first documented case of confirmed prostate cancer metastasis to the pineal gland in a living patient. The patient underwent an endoscopic third ventriculostomy and pineal lesion biopsy with complete resolution of his hydrocephalus and presenting symptoms. His biopsy results confirmed the prostate origin of the metastasis, and he subsequently underwent stereotactic radiosurgery for treatment of this lesion.

CONCLUSIONS

This is the first report of the clinical management of metastatic prostate cancer to the pineal region and description of the clinical outcome. Although prostate cancer is the most common cancer in American men, metastasis to the pineal has only been reported twice from autopsy examinations. Overall, pineal tumors in the geriatric population are exceedingly rare and the age and comorbidities in this patient made management quite unique.

Endoscopic Third Ventriculostomy: Outcome Analysis of an Anterior Entry Point

BACKGROUND

Endoscopic third ventriculostomy (ETV) is a safe and effective treatment for hydrocephalus. An entry point located 4 cm anterior to the coronal suture, 3 cm anterior to Kocher point, and approximately 9 cm from the pupil at the midpupillary line has been used successfully for the last 20 years in our center. We aimed to evaluate this alternative anterior entry point routinely used for ETV, with or without concurrent endoscopic biopsy.

METHODS

Patients undergoing this proposed entry point were examined to evaluate its safety and efficacy. Factors such as patients' age, sex, hydrocephalus etiology, tumor location and pathology, and complication rate were examined through regression analyses to evaluate their impact on tumor biopsy and ETV success rates, and the need for subsequent ventricular shunting.

RESULTS

A total of 131 patients were included in the study. ETV was successful in 125 (95.4%) patients. Of these, 26 (19.8%) patients required a biopsy, which was successful in 21 (80.8%) cases. A complication was observed in 10 (7.6%) patients, with a trend toward complications occurring after ETV failure. There was no association between ETV success rate and patients' age (P = 0.5) or sex (P = 0.99).

CONCLUSIONS

The anterior entry point is a safe and effective method for ETV, especially when considering concurrent ventricular tumor biopsy. This entry point may be considered as a more minimally invasive procedure when using rigid endoscopy and may also eliminate the need for a flexible scope.

A multiport MR-compatible neuroendoscope: spanning the gap between rigid and flexible scopes

OBJECTIVE Rigid endoscopes enable minimally invasive access to the ventricular system; however, the operative field is limited to the instrument tip, necessitating rotation of the entire instrument and causing consequent tissue compression while reaching around corners. Although flexible endoscopes offer tip steerability to address this limitation, they are more difficult to control and provide fewer and smaller working channels. A middle ground between these instruments-a rigid endoscope that possesses multiple instrument ports (for example, one at the tip and one on the side)-is proposed in this article, and a prototype device is evaluated in the context of a third ventricular colloid cyst resection combined with septostomy. METHODS A prototype neuroendoscope was designed and fabricated to include 2 optical ports, one located at the instrument tip and one located laterally. Each optical port includes its own complementary metal-oxide semiconductor (CMOS) chip camera, light-emitting diode (LED) illumination, and working channels. The tip port incorporates a clear silicone optical window that provides 2 additional features. First, for enhanced safety during tool insertion, instruments can be initially seen inside the window before they extend from the scope tip. Second, the compliant tip can be pressed against tissue to enable visualization even in a blood-filled field. These capabilities were tested in fresh porcine brains. The image quality of the multiport endoscope was evaluated using test targets positioned at clinically relevant distances from each imaging port, comparing it with those of clinical rigid and flexible neuroendoscopes. Human cadaver testing was used to demonstrate third ventricular colloid cyst phantom resection through the tip port and a septostomy performed through the lateral port. To extend its utility in the treatment of periventricular tumors using MR-guided laser therapy, the device was designed to be MR compatible. Its functionality and compatibility inside a 3-T clinical scanner were also tested in a brain from a freshly euthanized female pig. RESULTS Testing in porcine brains confirmed the multiport endoscope's ability to visualize tissue in a blood-filled field and to operate inside a 3-T MRI scanner. Cadaver testing confirmed the device's utility in operating through both of its ports and performing combined third ventricular colloid cyst resection and septostomy with an endoscope rotation of less than 5°. CONCLUSIONS The proposed design provides freedom in selecting both the number and orientation of imaging and instrument ports, which can be customized for each ventricular pathological entity. The lightweight, easily manipulated device can provide added steerability while reducing the potential for the serious brain distortion that happens with rigid endoscope navigation. This capability would be particularly valuable in treating hydrocephalus, both primary and secondary (due to tumors, cysts, and so forth). Magnetic resonance compatibility can aid in endoscope-assisted ventricular aqueductal plasty and stenting, the management of multiloculated complex hydrocephalus, and postinflammatory hydrocephalus in which scarring obscures the ventricular anatomy.

Operative planning aid for optimal endoscopic third ventriculostomy entry points in pediatric cases

OBJECT

Endoscopic third ventriculostomy (ETV) uses anatomical spaces of the ventricular system to reach the third ventricle floor and create an alternative pathway for cerebrospinal fluid flow. Optimal ETV trajectories have been previously proposed in the literature, designed to grant access to the third ventricle floor without a displacement of eloquent periventricular structures. However, in hydrocephalus, there is a significant variability to the configuration of the ventricular system, implying that the optimal ETV trajectory and cranial entry point needs to be planned on a case-by-case basis. In the current study, we created a mathematical model, which tailors the optimal ETV entry point to the individual case by incorporating the ventricle dimensions.

METHODS

We retrospectively reviewed the imaging of 30 consecutive pediatric patients with varying degrees of ventriculomegaly. Three dimensional radioanatomical models were created using preoperative MRI scans to simulate the optimal ETV trajectory and entry point for each case. The surface location of cranial entry points for individual ETV trajectories was recorded as Cartesian coordinates centered at Bregma. The distance from the Bregma in the coronal plane represented as "x", and the distance from the coronal suture in the sagittal plane represented as "y". The correlation between the ventricle dimensions and the x, y coordinates were tested using linear regression models.

RESULTS

The distance of the optimal ETV entry point from the Bregma in the coronal plane ("x") and from the coronal suture in the sagittal plane ("y") correlated well with the frontal horn ratio (FHR). The coordinates for x and y were fitted along the following linear equations: x = 85.8 FHR-13.3 (r ² = 0.84, p < 0.001) and y = -69.6 FHR + 16.7 (r ² = 0.83, p < 0.001).

CONCLUSION

The surface location of the optimal cranial ETV entry point correlates well with the ventricle size. We provide the first model that can be used as a surgical planning aid for a case specific ETV entry site with the incorporation of the ventricle size.

Three-Dimensional Simulation of Collision-Free Paths for Combined Endoscopic Third Ventriculostomy and Pineal Region Tumor Biopsy: Implications for the Design Specifications of Future Flexible Endoscopic Instruments

BACKGROUND

Recent innovations to expand the scope of intraventricular neuroendoscopy have focused on transitioning multiple-incision procedures into single-corridor approaches. However, the successful adoption of these combined procedures requires minimizing the unwanted torques applied to surrounding healthy structures.

OBJECTIVE

To define the geometry of relevant anatomical structures in endoscopic third ventriculostomy (ETV) and pineal region tumor biopsy (ETB). Second, to determine the optimal instrument shaft path required for collision-free single burr hole combined ETV/ETB.

METHODS

Magnetic resonance and computed tomography data from 15 pediatric patients who underwent both ETV and ETB procedures between 2006 and 2014 was segmented by using the 3DSlicer software package to create virtual 3-D patient models. Anatomical regions of interest were measured including the foramen of Monro, the massa intermedia, the floor of the third ventricle, and the tumor margin. Utilizing the MATLAB software package, virtual dexterous instruments were inserted into the models and optimal dimensions were calculated.

RESULTS

The diameters of the foramen of Monro, massa intermedia (anterior-posterior, superior-inferior), anterior third ventricle, and tumor margin are 6.85, 4.01, 5.05, 14.2, and 28.5 mm, respectively. The average optimal burr placement was determined to be 22.5 mm anterior to the coronal and 30 mm lateral to the sagittal sutures. Optimal flexible instrument geometries for novel instruments were calculated.

CONCLUSION

We have established a platform for estimating the shape of novel curved dexterous instruments for collision-free targeting of multiple intraventricular points, which is both patient and tool specific and can be integrated with image guidance. These data will aid in developing novel dexterous instruments.

Endoscopic Histologic Mapping of a Mixed Germ Pineal Tumor

BACKGROUND

The accurate histologic diagnosis of germ cell tumors in the pineal region is a keystone for determining the best treatment strategy and prognosis. This situation poses a challenge for the neuropathologist, considering the lack of a standarized procedure to obtain biopsy samples, which results in few and small specimens, which are not suitable for diagnosis.

CASE DESCRIPTION

We report a case in which a pineal region mixed germ cell tumor was accurately diagnosed by performing histologic mapping through a dual burr-hole endoscopic approach. The technical pitfalls and other considerations necessary for obtaining an accurate diagnosis in this tumor subgroup are specified. In addition, the histologic analysis regarding the sampling technique used is described.

CONCLUSIONS

The supraorbital frontal endoscopic approach enables the surgeon to perform histologic mapping of pineal region tumors, allowing standarization of the procedure used to obtain the specimens. This approach could result in a more accurate diagnosis, especially in mixed germ cell neoplasms.

Endoscopic Versus Stereotactic Procedure for Pineal Tumor Biopsies: Focus on Overall Efficacy Rate

OBJECTIVE

The management of pineal region tumors depends on the histologic subtypes. Two minimally invasive techniques are available: endoscopic intraventricular biopsies and stereotactic biopsies. The recent Southampton and Lille series are the largest endoscopic and stereotactic series of pineal region tumors reporting both diagnosis rate and accuracy rate, respectively; we elaborated on these results in the light of other recent studies.

METHODS

We compared the Southampton endoscopic series with the Lille series, reflecting our 25-year experience of stereotactic biopsies, and the metadata of the literature for both approaches, as reported in the 2013 Report of the French-Speaking Society of Neurosurgery on tumors of the pineal region.

RESULTS

The results of the Southampton series match the endoscopic literature, in particular regarding the diagnosis rate (81.2%) and the perioperative morbidity (25.0%), and provide a rarely reported accuracy rate (78.6%), giving access to the overall efficacy rate (63.8%). The results of the Lille series match the stereotactic literature and show better results than endoscopic biopsies concerning the diagnosis rate (98.9%), accuracy rate (100%), resulting overall efficacy rate (98.9%), and perioperative morbidity (6.4%).

CONCLUSIONS

The Southampton and Lille series provide a unique opportunity to compare the overall efficacy rates of endoscopic and stereotactic biopsies, respectively. The stereotactic approach is safer and more effective for biopsies of pineal region tumors. To improve the safety and reliability of endoscopic biopsies, various methods have to be evaluated: alternative burr-hole strategies, use of neuronavigation, and a combination of flexible and rigid endoscopes.

Design optimization of neuroendoscopic continuum instruments for third ventriculostomy and tumor biopsy

A simulation-based approach to the design of procedure-specific dexterous neuroendoscopic continuum instruments for endoscopic third ventriculostomy and tumor biopsy is proposed. Given pre-operative CT and MRI images, the algorithm returns instrument design specifications including lengths, curvatures and alternative positions for the surgical incision while respecting anatomical boundaries. This methodology proposes a novel clinically-guided geometric representation of surgical targets specific to this indication. The additional constraints imposed by the presence of surgical trocars and endoscopes are also considered. Finally, we conclude with a clinical example to demonstrate the proposed approach.

Comparative analysis of endoscopic third ventriculostomy trajectories in pediatric cases

OBJECT

Endoscopic third ventriculostomy (ETV) has become a widely used method for CSF diversion when treating obstructive hydrocephalus. There are multiple recommendations on the transcortical ETV entry points, and some are specifically designed to provide a trajectory that avoids displacement to the eloquent periventricular structures. However, the morphology of the ventricular system is highly variable in hydrocephalus, and therefore a single best ETV trajectory may not be applicable to all cases. In the current study, 3 frequently quoted ETV entry points are compared in a cohort of pediatric cases with different degrees of ventriculomegaly.

METHODS

The images of 30 consecutive pediatric patients with varying degrees of ventriculomegaly were reviewed. Three-dimensional models were created using radiological analysis of anatomical detail and preoperative MRI scans in order to simulate 3 frequently quoted ETV trajectories for rigid neuroendoscopes. These trajectories were characterized based on the frequency and depth of tissue displacement to structures such as the fornix, caudate nucleus, genu of the internal capsule, and thalamus. The results are stratified based on ventricle size using the frontal horn ratio (FHR).

RESULTS

Eloquent areas were displaced in nearly all analyzed entry points (97%-100%). Stratifying the data based on ventricle size revealed that (1) lateral structures were more likely to be displaced in cases of intermediate ventriculomegaly (FHR < 0.4) using all 3 trajectories, whereas (2) the fornix was less likely to be displaced using more posteriorly placed trajectories for severe ventriculomegaly (FHR > 0.4). Allowing for minimal (2.4 mm) tissue displacement, a more posterior entry point was less traumatic for severe ventriculomegaly.

CONCLUSIONS

There is no single best ETV trajectory that fully avoids displacement of the eloquent periventricular structures. Larger ventricles require a more posteriorly placed entry point in order to reduce injury to the eloquent structures, and intermediate ventricles would dictate a medial entry point. These results suggest that the optimal entry point should be selected on a case-by-case basis after incorporating ventricle size.

A Novel Protocol of Continuous Navigation Guidance for Endoscopic Third Ventriculostomy

BACKGROUND:

Although considered a standard neurosurgical procedure, endoscopic third ventriculostomy (ETV) is associated with a relatively high complication rate that is predominantly related to malpositioning of the trajectory.

OBJECTIVE:

To develop an advanced navigation protocol for ETV, assess its possible benefits over commonly used ETV trajectories, and apply this protocol during surgery.

METHODS:

After development of our advanced protocol, the imaging data of 59 patients who underwent ETV without navigation guidance was transferred to our navigation software. An individualized endoscope trajectory was created according to our protocol in all cases. This trajectory was compared with 2 standard trajectories, especially with regard to the distance to relevant neuronal structures: a trajectory manually measured on preoperative radiological images, as performed in all 59 cases, and a trajectory resulting from a commonly used fixed coronal burr hole. Subsequently, we applied the protocol in 15 ETVs to assess the feasibility and procedural complications.

RESULTS:

Our individualized trajectory resulted in a significantly greater distance to the margins of the foramen of Monro, and the burr hole was located more posteriorly from the coronal suture in comparison with the standard trajectories. The advanced ETV technique was feasible in all 15 procedures, and no major complications occurred in any procedure. In 1 patient, a fornix contusion without clinical correlation was observed.

CONCLUSION:

Our data indicate that the proposed navigation protocol for ETV optimizes the distance of the endoscope to important neuronal structures. Continuous endoscope and puncture device guidance may further add to the safety of this procedure.