Transcerebellar Approach Research Articles

How i do it: Robot-assisted transcerebellar stereotactic approach for brainstem lesion.

Stereotactic approaches to diffuse intrinsic pontine gliomas (DIPGs) remain essential due to advances in molecular biology and management, necessitating tissue sampling. Here we present an effective technique with a biopsy by robot-assisted transcerebellar approach. Our procedure was performed using the ROSA robotic system and the OARM CT scan, which provided stereotactic conditions for this transcerebellar approach to brainstem lesions. The robot-assisted transcerebellar stereotactic approach remains essential to provide complications for biopsy of brainstem lesions.

Frameless Stereotactic Biopsy of Brainstem Tumors Using the Stealth Autoguide: A Technical Note.

In the molecular era of neuro-oncology, it is increasingly necessary to obtain tissue for next-generation sequencing and methylome profile for prognosis and targeted oncological management. Brainstem tumors can be technically challenging to biopsy in the pediatric population. Frame-based and frameless techniques have previously been described and proven to be safe and efficacious in children. Recent cranial robotic guidance platforms have augmented the fluency of frameless stereotactic approaches, but the technical nuances of these procedures in children are not often discussed. We present a technical workflow for frameless stereotactic biopsy of brainstem tumors in children using the Medtronic Stealth Autoguide cranial robotic guidance platform and examine safety and efficacy of this surgical approach. A minimally invasive, frameless, transcerebellar approach is described, including operative steps and workflow. We assessed operative times, diagnostic accuracy and yield, and complication rates. Five patients underwent biopsy with the technique described. The youngest patient in our series was of 2 years. The intended target was achieved on postoperative imaging in all cases, and diagnostic tissue was obtained in all 5 patients. One patient had a clinically insignificant hemorrhage. Frameless stereotactic biopsy of the brainstem can be performed safely, efficiently, and accurately using the Medtronic Stealth Autoguide robotic platform in children as young as 2 years.

Leksell Frame-Based Stereotactic Biopsy for Infratentorial Tumor : Practical Tips and Considerations.

The Leksell frame-based transcerebellar approach was proposed with the arc support frame attached upside down to the Z coordinate. This study presented practical tips and considerations for obtaining adequate tissue samples for deep-seated cerebellar lesions or lower brainstem lesions specifically those accessible via the cerebellar peduncle. For practical insights, the Leksell coordinate frame G was fixed to prevent the anterior screw implantation within the temporalis muscle, to avoid interference with the magnetic resonance (MR)-adapter, and taking into account the magnetic field of MR in close proximity to the tentorium. After mounting of indicator box, the MR imaging evaluation should cover both the indicator box and the infratentorial region that deviated from it. The coordinates [X, Y, Za, Arc0, Ringa0] obtained from Leksell SurgiPlan® software (Elekta, Stockholm, Sweden) with arc 00 located on the patient's right side were converted to [X, Y, Zb=360-Za, Arc0, Ringb0=Ringa0-1800]. The operation was performed in the prone position under general anesthesia in four patients with deep cerebellar (n=3) and brainstem (n=1) tumors. The biopsy results showed two cases of diffuse large B-cell lymphoma, one metastatic braintumor and one glioblastoma. One patient required frame repositioning as a complication. Drawing upon the methodology outlined in existing literature, we anticipate that imparting supplementary expertise could render the stereotactic biopsy of infratentorial tumors more consistent and manageable for the practitioner, thereby facilitating adequate tissue samples and minimizing patient complications.

Robot-assisted transcerebellar stereotactic approach to the posterior fossa in pediatric patients: a technical note.

During the last decade, there has been renewed interest in stereotactic approaches to diffuse intrinsic pontine gliomas (DIPGs) in children, due to the development of new concepts in molecular biology and management, and subsequent need for tissue sampling. Stereotactic frame-based and robot-assisted techniques are associated with reduced target error and have been incorporated into standard practice at our institution. Four children (age 2-7years) underwent a robot-assisted frame-based transcerebellar approach using the Leksell G frame coupled with Renishaw's neuromate® stereotactic robot. The procedures included 3 biopsies (two brainstem tumors and one cerebellar hemispheric lesion) and 1 depth electrode implantation into a low-grade tumor remnant (ganglioglioma) of the middle cerebellar peduncle causing drug-resistant epilepsy in a young girl. Targeting was based on MRI, and in one case, 18F-FET-PET was coregistered to MRI to improve sampling accuracy. The frame was applied 180° rotated compared to standard orientation, and patients were positioned prone during surgery and stereotactic preoperative CT scan. Postoperative CT scan ruled out complications and was coregistered to preoperative MRI to check the target accuracy. No complications occurred, and targeting was accurate in all cases. All tissue samplings provided proper histology; depth electrode EEG exploration was diagnostic and led subsequent resective surgery. According to our experience, the transcerebellar frame-based robotic stereotactic approach to the cerebellum and the brainstem is feasible, safe, and effective even in young children.

Frameless robot-assisted stereotactic biopsies for lesions of the brainstem-a series of 103 consecutive biopsies.

Targeted treatment for brainstem lesions requires above all a precise histopathological and molecular diagnosis. In the current technological era, robot-assisted stereotactic biopsies represent an accurate and safe procedure for tissue diagnosis. We present our center's experience in frameless robot-assisted biopsies for brainstem lesions. We performed a retrospective analysis of all patients benefitting from a frameless robot-guided stereotactic biopsy at our University Hospital, from 2001 to 2017. Patients consented to the use of data and/or images. The NeuroMate® robot (Renishaw™, UK) was used. We report on lesion location, trajectory strategy, histopathological diagnosis and procedure safety. Our series encompasses 96 patients (103 biopsies) treated during a 17years period. Mean age at biopsy: 34.0years (range 1-78). Most common location: pons (62.1%). Transcerebellar approach: 61 procedures (59.2%). Most common diagnoses: diffuse glioma (67.0%), metastases (7.8%) and lymphoma (6.8%). Non conclusive diagnosis: 10 cases (9.7%). After second biopsy this decreased to 4 cases (4.1%). Overall biopsy diagnostic yield: 95.8%. Permanent disability was recorded in 3 patients (2.9%, all adults), while transient complications in 17 patients (17.7%). Four cases of intra-tumoral hematoma were recorded (one case with rapid decline and fatal issue). Adjuvant targeted treatment was performed in 72.9% of patients. Mean follow-up (in the Neurosurgery Department): 2.2years. Frameless robot-assisted stereotactic biopsies can provide the initial platform towards a safe and accurate management for brainstem lesions, offering a high diagnostic yield with low permanent morbidity.

Rediscovery of the transcerebellar approach: improving the risk-benefit ratio in robot-assisted brainstem biopsies.

Conventional frame-based stereotaxy through a transfrontal approach (TFA) is the gold standard in brainstem biopsies. Because of the high surgical morbidity and limited impact on therapy, brainstem biopsies are controversial. The introduction of robot-assisted stereotaxy potentially improves the risk-benefit ratio by simplifying a transcerebellar approach (TCA). The aim of this single-center cohort study was to evaluate the risk-benefit ratio of transcerebellar brainstem biopsies performed by 2 different robotic systems. In addition to standard quality indicators, a special focus was set on trajectory selection for reducing surgical morbidity. This study included 25 pediatric (n = 7) and adult (n = 18) patients who underwent 26 robot-assisted biopsies via a TCA. The diagnostic yield, complication rate, trajectory characteristics (i.e., length, anatomical entry, and target-point location), and skin-to-skin (STS) time were evaluated. Transcerebellar and hypothetical transfrontal trajectories were reconstructed and transferred into a common MR space for further comparison with anatomical atlases. Robot-assisted, transcerebellar biopsies demonstrated a high diagnostic yield (96.2%) while exerting no surgical mortality and no permanent morbidity in both pediatric and adult patients. Only 3.8% of cases involved a transient neurological deterioration. Transcerebellar trajectories had a length of 48.4 ± 7.3 mm using a wide stereotactic corridor via crus I or II of the cerebellum and the middle cerebellar peduncle. The mean STS time was 49.5 ± 23.7 minutes and differed significantly between the robotic systems (p = 0.017). The TFA was characterized by longer trajectories (107.4 ± 11.8 mm, p < 0.001) and affected multiple eloquent structures. Transfrontal target points were located significantly more medial (-3.4 ± 7.2 mm, p = 0.042) and anterior (-3.9 ± 8.4 mm, p = 0.048) in comparison with the transcerebellar trajectories. Robot-assisted, transcerebellar stereotaxy can improve the risk-benefit ratio of brainstem biopsies by avoiding the restrictions of a TFA and conventional frame-based stereotaxy. Profound registration and anatomical-functional trajectory selection were essential to reduce mortality and morbidity.

The stability of multifocal ventriculoperitoneal shunts with Y-connections

Multifocal ventriculoperitoneal shunts with Y-connections (MVPS with Ys) are widely used in many centers when neuroendoscopic procedures on entrapped ventricles are not feasible; however, their use is not frequent. This study aimed to confirm the stability of an MVPS with Y and, for the first time, identify the factors that influence stability. We studied 33 consecutive patients who underwent initial conversion to MVPS with Ys. The one-year overall shunt survival rate was calculated and compared with the historical outcome of single ventriculoperitoneal shunts (VPSs). The factors influencing the one-year overall shunt survival rate were also investigated. The one-year survival rate for proximal catheters in each location was further investigated, and the rates were compared among locations. The factors affecting proximal catheter survival were determined. The one-year overall shunt survival rate of MVPS with Y was 70%, which was not much different from that of previously reported single VPSs, including our institution. We found no significant factor influencing overall shunt survival, but when an additional catheter was inserted into the fourth ventricle, the survival rate was exceptionally low at 40% (p = 0.21). When we investigated the one-year survival rate of each proximal catheter, we found that the location of the proximal catheter showed a certain trend toward significance (p = 0.07), especially in the case of the fourth ventricle, which had the lowest survival rate at 57% and an odds ratio of 15.64 (p = 0.013) in multivariate analysis. However, when the catheter was sufficiently inserted parallel to the brain stem using navigation, the survival was relatively well maintained (1,995 to 2,547days). The stability of MVPS with Y was similar to that of single VPSs. However, the malfunction rate of the proximal catheter inserted at the fourth ventricle in the Y-connection was higher than that at other locations. The transcerebellar vertical approach or transtentorial approach parallel to the brain stem may decrease the malfunction rate.

Endoscope-Assisted Neuroportal Transcerebellar Approach to the Fourth Ventricle: An Anatomical Study.

Minimally invasive approaches to deep-seated lesions still represent a fundamental issue in modern neurosurgery. Tubular retractors allow to enhance the operability of intraventricular lesions, minimizing the risk of damages to brain parenchyma. Increasing interest for portal devices has been mainly focused on supratentorial pathologies, while transportal approaches in the posterior cranial fossa have been rarely described. In the present study, the authors aimed to investigate the surgical exposure and operability obtained with a microsurgical neuroportal transcerebellar approach targeting the fourth ventricle, assisted by endoscopic exploration. Six cadaveric specimens were provided for anatomical microsurgical dissection and Vycor ViewSite Brain Access System was used as tubular retractor. Surgical feasibility of the neuroportal transcerebellar approach was demonstrated through a definable and measurable parameter, the operability score. The neuroport provided a surgical corridor away from eloquent structures to target the whole fourth ventricle cavity, preventing injury to cerebellar nuclei and white matter pathways and, potentially, minimizing the risk of surgical morbidity. Maximal operability was reached in the pontomedullary junction and medullary area of the ventricular floor. Transportal endoscopic assistance contributed to a further extension of surgical exposure in blind spots, corresponding to the ipsilateral lateral recess, the uppermost part of the fourth ventricle, and the obex. The neuroportal transcerebellar approach represents a viable alternative route to the fourth ventricle, avoiding vermian splitting or subarachnoid dissection of the cerebellomedullary cistern. Endoscopic assistance enhances the exposure of the surgical field and accomplishes a valid instrument for intraventricular orientation to ease microsurgical procedures.

A Paravermal Trans-Cerebellar Approach to the Posterior Fossa Tumor Causes Hypertrophic Olivary Degeneration by Dentate Nucleus Injury.

Simple SummaryPosterior fossa tumor surgery is challenging due to the proximity and exposure of cerebellar structures. A favorable operative approach is unknown. Following lesions to the dentato–rubro–olivary-pathway, a neurodegenerative disease called hypertrophic olivary degeneration (HOD) can occur. This study for the first time demonstrates that paravermal trans-cerebellar approaches are associated with a significantly higher likelihood of HOD on MRI when compared to other approaches. This finding can well be attributed to dentate nucleus (DN) injury. Furthermore, cerebellar mutism syndrome (CMS) was discussed in the literature to be correlated with HOD due to a functional overlap of pathways involved. We found no such correlation in this study, but HOD was shown to be a reliable indicator for surgical disruption of efferent cerebellar pathways involving the DN. Henceforth, neurosurgeons should consider more midline or lateral approaches in posterior fossa surgery to spare the DN whenever feasible, and focus on cerebellar functional anatomy in their preoperative planning.Background: In brain tumor surgery, injury to cerebellar connectivity pathways can induce a neurodegenerative disease called hypertrophic olivary degeneration (HOD), along with a disabling clinical syndrome. In children, cerebellar mutism syndrome (CMS) is another consequence of damage to cerebello–thalamo–cortical networks. The goal of this study was to compare paravermal trans-cerebellar to other more midline or lateral operative approaches in their risk of causing HOD on MR-imaging and CMS. Methods: We scanned our neurosurgical database for patients with surgical removal of pilocytic astrocytoma, ependymoma and medulloblastoma in the posterior fossa. Fifty patients with a mean age of 22.7 (±16.9) years were identified and analyzed. Results: HOD occurred in n = 10/50 (20%) patients within four months (median), always associated with contralateral dentate nucleus (DN)-lesions (p < 0.001). Patients with paravermal trans-cerebellar approach significantly more often developed HOD (7/11; 63.6%) when compared to other approaches (3/39; 7.7%; p < 0.001). Injury to the DN occurred more frequently after a paravermal approach (8/11 vs. 13/39 patients; p < 0.05). CMS was described for n = 12/50 patients (24%). Data indicated no correlation of radiological HOD and CMS development. Conclusions: A paravermal trans-cerebellar approach more likely causes HOD due to DN-injury when compared to more midline or lateral approaches. HOD is a radiological indicator for surgical disruption of cerebellar pathways involving the DN. Neurosurgeons should consider trajectories and approaches in the planning of posterior fossa surgery that spare the DN, whenever feasible.

Stereotactic Brainstem Biopsy: Technical Aspects with Emphasis on Role of Awake Craniotomy

Abstract Introduction The role of frame-based stereotactic biopsy in brainstem lesions has been well established in literature. Transfrontal, transtentorial, and transcerebellar routes are used to access various targets within the brainstem. While the transfrontal approach is preferable in midbrain lesions, a transcerebellar approach via the middle cerebellar peduncle forms the shortest possible trajectory for pontine and medullary lesions. Objective Authors to describe the technical nuances of frame-based stereotactic biopsy of lower brainstem lesions to increase the procedural safety and efficacy. Materials and Methods Technical modifications in frame fixation were done to acheive the desired trajectory to the target. In adult cases biopsy was performed with patient awake during the procedure. Results Total of five patients underwent biopsy with the technical modifications. Three patients were adults and two were in pediatric age group. Their age ranged from 12 to 50 years. No complications were encountered. Two of the biopsies showed demyelination and the other three turned out to be low-grade glioma, pilocytic astrocytoma, and lymphoma, respectively. Conclusion Despite obvious inherent risks, the transcerebellar biopsy in semi-sitting position is a well-tolerated and effective method of obtaining a diagnostic tissue sample in brainstem lesions. We have noted that adoption of the technical modifications described in this article has aided in improving the safety and ease of the procedure.

Frameless Stereotactic Targeting of the Cerebellar Dentate Nucleus in Nonhuman Primates: Translatable Model for the Surgical Delivery of Gene Therapy

Background: Stereotactic targeting techniques in nonhuman primate (NHP) models are often utilized in the preclinical investigation of new drug therapies with the goal of demonstrating accurate and reliable delivery of a therapy to the target tissue. However, targeting certain neuroanatomical structures can be challenging. The deep cerebellar nuclei, specifically the dentate nucleus, are potential stereotactic targets for the treatment of certain ataxias. Currently, there are no detailed techniques describing frameless targeting of these structures in a NHP model. A well-defined, accurate, and reliable stereotactic surgical approach to the dentate in these animal models is critical to prove the feasibility and safety of drug delivery in order to develop clinical protocols. Methods: Frameless stereotactic neuronavigation was employed to target the bilateral dentate nuclei of the cerebellum in four healthy juvenile Cynomolgus monkeys via a suboccipital, transcerebellar approach. The precision and accuracy of the targeting were evaluated radiologically and histologically. Results: Using the described surgical methodology, we were successful in hitting the target deep cerebellar nuclei seven out of eight times. Conclusion: Frameless stereotactic targeting of the cerebellar dentate nuclei in NHPs for future investigational drug delivery is feasible, safe, and accurate as described by this report. Potential areas for improving the technique are discussed.

Microscopic trans-cerebellar approach for infratentorial cavernous malformation near the lateral recess associated with developmental venous anomaly

Background: Reports showed the intimate association of the developmental venous anomaly with infra-tentorial cavernous malformation. This association has several clinical and surgical implications, sometimes this association will be a surgical challenge and affect the selection of the safest approach to the lesion. Surgery for infratentorial cavernoma is indicated for accessible symptomatic lesion only.&#x0D; Case scenario: we present a case of deep cerebello-pontine CM adjacent to the lateral recess, presented with acute clinical deterioration to the emergency department of the Neurosurgery Teaching Hospital in Baghdad, Iraq, with the only possible approach was Trans-cerebellar approach because of the medial location of the associated DVA.&#x0D; Conclusion: The association of developmental venous anomaly with infratentorial cavernous malformation has a pivotal role in selection the most appropriate and safe surgical approach which should be based upon the individualized patient anatomy and the location of the target lesion.

Novel Use of the Leksell Gamma Frame for Stereotactic Biopsy of Posterior Fossa Lesions.

Stereotactic transcerebellar biopsies of brainstem tumors have often been reported. The Leksell frame or Cosman-Roberts-Wells frame is often used in transcerebellar approaches. However, to access lesions via the cerebellum, these frames should be secured as inferiorly on the cranium as possible, which can require exaggerated neck flexion and limit the flexible trajectory to the target. To overcome these disadvantages, we have devised a new way to use the Leksell frame for transcerebellar approaches. The frame was fixed to the upper part of the head and arc support by attaching the frame upside down, which gives surgeons a wide operative field and permits flexible trajectory planning. Under local anesthesia, the surgery was performed in a sitting position. Air was observed in the target site on postoperative computed tomography and magnetic resonance imaging, which confirmed that a specimen had been successfully sampled from the site as planned. Our devised transcerebellar approach provided a generous operative field and a flexible trajectory, which enabled minimally invasive biopsy of aposterior fossa lesions to be performed in a shortamountof time with the patient under local anesthesia.

Telovelar Approach to IVth Ventricle Tumor: Experience and Review of Literature

Posterior fossa tumor surgery is challenging especially those located in the deeper regions of the middle and upper part of fourth ventricle. The traditional approach has been the vermis splitting or transcerebellar approach to gain access to these lesions. This is a retrospective study of all the cases operated via the telovelar approach between March 2008 and June 2017 in this centre. A total of eight cases were operated in this study period. With regards to medulloblastoma near total excision was achieved in 50% of the cases and one with total removal. Of these two cases needed postoperative ventriculo-peritoneal shunt , there were two cases of recurrence and in spite of cranio-spinal irradiation there were two deaths. Haemangioblastoma and choroid plexus papilloma were removed in total with no recurrence. One case of ependymoma had excessive bleeding with introperative hypotension leading to abandonment of the procedure. The telovelar approach has been described in detail by various authors elaborating the salient features along with the techniques to access the region around the fourth ventricle without the transvermian approach. The advantages of this approach are the avoidance of splitting the vermis and the theoretical reduced possibility of cerebellar mutism. Excision via bilateral telovelar approach have also been described for large tumors. Nepal Journal of Neuroscience, Vol. 14, No. 2, 2017 Page: 16-20

TRTH-23. FEASIBILITY AND SAFETY OF SURGICAL BIOPSY FOR PATIENTS WITH DIPG: PRELIMINARY RESULTS FROM DIPG-BATS

INTRODUCTION: The DIPG Biology and Treatment Study (DIPG-BATS) incorporated a surgical biopsy at presentation and stratified patients to receive FDA-approved agents chosen on the basis of specific biologic targets. METHODS: Subjects were enrolled in the DIPG-BATS trial if the imaging appearance of the tumors had typical features of a DIPG. Surgical biopsies were performed after enrollment and prior to definitive treatment. Subjects were all treated with conventional fractionated external radiotherapy, and bevacizumab. Subjects were stratified to receive erlotinib or temozolomide, both agents, or neither agent. Whole-genome sequencing (WGS) and RNA-sequencing were performed on tumor samples but not used for treatment planning. RESULTS: Fifty-three patients were enrolled at 23 participating institutions, of which 50 underwent biopsy. The median age was 6.4 years, with a male to female ratio of 24::29. Surgical biopsies were performed using standard stereotactic techniques with a transcerebellar approach. There were no deaths attributed to the surgical procedure. Two patients experienced grade 3 toxicities during the procedure (one patient with apnea and one with hypertension). One patient experienced a neurologic deficit (left hemiparesis) that did not recover. Of the 50 patients biopsied, 46 provided sufficient tissue to perform the assays (92%, two-stage exact binomial 90% confidence interval 83–97%). CONCLUSIONS: Surgical biopsy of DIPGs is technically feasible, associated with acceptable risks, and can provide biologic data that informs treatment decision making.

Diffuse intrinsic pontine gliomas in children: Interest of robotic frameless assisted biopsy. A technical note

IntroductionDiffuse intrinsic pontine gliomas (DIPG) constitute 10–15% of all brain tumors in the pediatric population; currently prognosis remains poor, with an overall survival of 7–14 months. Recently the indication of DIPG biopsy has been enlarged due to the development of molecular biology and various ongoing clinical and therapeutic trials. Classically a biopsy is performed using a stereotactic frame assisted procedure but the workflow may sometimes be heavy and more complex especially in children. In this study the authors present their experience with frameless robotic-guided biopsy of DIPG in a pediatric population. Patients and methodsRetrospective study on a series of five consecutive pediatric patients harboring DIPG treated over a 4-year period. All patients underwent frameless robotic-guided biopsy via a transcerebellar approach. ResultsAmong the 5 patients studied 3 were male and 2 female with a median age of 8.6 years [range 5 to 13 years]. Clinical presentation included ataxia, hemiparesis and cranial nerve palsy in all patients. MRI imaging of the lesion showed typical DIPG features (3 of them located in the pons) with hypo-intensity on T1 and hyper-intensity signal on T2 sequences and diffuse gadolinium enhancement. The mean procedure time was 56minutes (range 45 to 67minutes). No new postoperative neurological deficits were recorded. Histological diagnosis was achieved in all cases as follows: two anaplastic astrocytomas (grade III), two glioblastomas, and one diffuse astrocytoma (grade III). ConclusionFrameless robotic assisted biopsy of DIPG in pediatric population is an easier, effective, safe and highly accurate method to achieve diagnosis.

Stereotactic biopsy of brainstem lesions: 21years experiences of a single center.

Stereotactic biopsies are procedures performed to obtain tumor tissue for diagnostic examinations. Cerebral lesions of unknown entities can safely be accessed and tissue can be examined, resulting in correct diagnosis and according treatment. Stereotactic procedures of lesions in highly eloquent regions such as the brainstem have been performed for more than two decades in our department. In this retrospective study we focus on results, approaches, modalities of anesthesia, and complications. We performed a retrospective analysis of our prospective database, including 26 patients who underwent stereotactic biopsy of the brainstem between April 1994 and June 2015. All of the patients underwent preoperative MRI. Riechert-Mundinger-frame was used before 2000, thereafter the Leksell stereotactic frame was used. After 2000 entry and target points were calculated by using BrainLab stereotactic system. We evaluated histopathological results as well as further treatment; additionally we compared complications of local versus general anesthesia and complications of a frontal versus a trans-cerebellar approach. Median age of all patients was 33years, and median number of tissue samples taken was 12. In all patients a final histopathological diagnosis could be established. 5 patients underwent the procedure under local anesthesia, 21 patients in general anesthesia. In 19 patients a frontal approach was performed, while in 7 patients a trans-cerebellar approach was used. Complications occurred in five patients. Thereby no significant difference was found with regard to approach (frontal versus trans-cerebellar) or anesthesia (local versus general). Stereotactic biopsies even of lesions in the brainstem are a save way to obtain tumor tissue for final diagnosis, resulting in adequate treatment. Approach can be trans-cerebellar or frontal and procedure can be performed either under local or general anesthesia without significant differences concerning complication rate.

Validation of a magnetic resonance imaging guided stereotactic access to the ovine brainstem.

BackgroundAnatomical differences between humans and domestic mammals preclude the use of reported stereotactic approaches to the brainstem in animals. In animals, brainstem biopsies are required both for histopathological diagnosis of neurological disorders and for research purposes. Sheep are used as a translational model for various types of brain disease and therefore a species-specific approach needs to be developed. The aim of the present study was to establish a minimally invasive, accurate and reproducible stereotactic approach to the brainstem of sheep, using the magnetic resonance imaging guided BrainsightTM frameless stereotactic system.ResultsA transoccipital transcerebellar approach with an entry point in the occipital bone above the vermis between the transverse sinus and the external occipital protuberance was chosen. This approach provided access to the target site in all heads. The overall mean needle placement error was 1.85 ± 1.22 mm.ConclusionsThe developed transoccipital transcerebellar route is short, provides accurate access to the ovine caudal cranial fossa and is a promising approach to be further assessed in live animals.

Stereotactic Biopsy for Brainstem Tumors: Comparison of Transcerebellar with Transfrontal Approach

Background: An important aspect of evaluating patients submitted to stereotactic biopsy of the brainstem is the trajectory used. The literature describes two principal approaches: the suboccipital transcerebellar and the transfrontal; however, no studies exist comparing these two techniques. Objective: The purpose of this study was to compare diagnosis success rates and complications between the suboccipital transcerebellar and transfrontal trajectories. Methods: The study evaluated 142 patients submitted to stereotactic biopsy. The patients presented brainstem tumors in the following areas: pons (n = 31), midbrain (n = 36), medulla (n = 2), pons-medulla (n = 30), pons-midbrain (n = 33), and midbrain-pons-medulla (n = 10). On 123 patients, the transfrontal approach was used, and on 19 the suboccipital transcerebellar approach. Results: Comparing success rates between the two approaches, it was observed that in the group of patients submitted to the transfrontal approach, 95.1% (117 cases) were successful, while in those submitted to the suboccipital transcerebellar approach, 84.2% (16 cases) were successful. Despite a higher success rate among patients in the first group, the difference was not statistically significant. Regarding complications, in patients who were biopsied via the transfrontal trajectory, the morbidity rate was 9.8% (12 cases), while in patients submitted to the suboccipital transcerebellar approach, the morbidity rate was 5.3% (1 case) and the mortality rate 5.3% (1 case). Conclusions: This study verified a higher diagnosis rate in patients submitted to the transfrontal approach than in those submitted to the suboccipital transcerebellar approach (95.1 vs. 84.2%); however, the difference was not statistically significant. Regarding complications, the rate was similar in both groups of patients.

Treatment of Hydrocephalus Associated with Neurosarcoidosis by Multiple Shunt Placement

A 31-year-old man was admitted to our hospital due to hydrocephalus with neurosarcoidosis. Ventriculo-peritoneal shunting was performed in the right lateral ventricle with intravenous methylprednisolone. Subsequently, after 4 months, additional ventriculo-peritoneal shunting in the left lateral ventricle was performed due to the enlarged left lateral ventricle and slit-like right lateral ventricle. After 6 months, he was re-admitted due to upward gaze palsy, and magnetic resonance image showed an isolated fourth ventricle with both the inlet and outlet of fourth ventricle obstructed by recurrent neurosarcoidosis. Owing to the difficulty of using an endoscope, we performed neuronavigator-guided ventriculo-peritoneal shunting via the left lateral transcerebellar approach for the treatment of the isolated fourth ventricle with intravenous methyl prednisolone. The patient was discharged with improved neurological status.