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Mark M. Souweidane

Object

Primary endoscopic procedures for children with intraventricular brain tumors include endoscopic tumor biopsy and endoscopic tumor removal. The simultaneous treatment of hydrocephalus with endoscopic third ventricu-lostomy (ETV) or endoscopic septostomy increases the appeal of a minimally invasive endoscopic approach.

Methods

Eighty-five patients who underwent endoscopic management of an intraventricular brain tumor were identified from a prospective database. Of these patients, 26 were younger than 21 years of age at the time of diagnosis. The surgical technique, its success rate, and patient outcome were assessed. Illustrative cases are used in this study to detail the procedure of endoscopic tumor biopsy and resection.

Endoscopic tumor procedures were successful in 96% of cases (23 of 24 endoscopic tumor biopsy samples and both endoscopic tumor removals). Fourteen simultaneous procedures were performed to treat hydrocephalus successfully. There was no recognized morbidity from the surgical procedures.

Conclusions

Endoscopic surgery in children with intraventricular brain tumors is an effective and safe method for sampling of the lesion and, in select cases, its resection. This minimally invasive technique should be considered in situations in which the patient might thereby avoid a more conventional procedure, given the high rate of success and low morbidity associated with endoscopic management.

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Konstantinos Margetis and Mark M. Souweidane

Endoscopic resection of colloid cyst in patients with normal-sized ventricular system is challenging, because the limited intraventricular space increases the risk of injuring eloquent nervous structures and critical blood vessels. The utilization of frameless stereotaxy and tissue shaving device facilitates the procedure. An important operative step is the ventricular insufflation that allows for an endoscope introduction without causing inadvertent injury to the caudate nucleus. The attached clip shows the basic operative steps of the procedure. In this clip the solid colloid cyst contents necessitated an en-block colloid cyst resection, in lieu of initially aspirating the cyst contents and subsequently removing the cyst walls.

The video can be found here: http://youtu.be/zzYYZEsd-uk.

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Maria M. Santos and Mark M. Souweidane

The authors report an illustrative case of a purely endoscopic surgical approach to successfully remove a solid choroid plexus papilloma of the third ventricle in an infant. A 10-week-old male infant first presented with transient episodes of forced downward gaze, divergent macrocephaly, a tense anterior fontanel, diastasis of the cranial sutures, and papilledema. Brain MRI revealed a small, multilobulated contrast-enhancing mass situated within the posterior third ventricle, with resultant obstructive hydrocephalus. A purely endoscopic removal of the tumor was performed through a single right frontal bur hole. Intraoperatively, a unique vascular tributary was recognized coming from the tela choroidea and was controlled with coagulation and sharp dissection. Postoperative MRI confirmed complete tumor removal, and the tumor was classified as a choroid plexus papilloma. There has been no evidence of tumor recurrence over 42 months of follow-up. With this case report the authors intended to show that endoscopic surgery can be an additional tool to consider when planning a choroid plexus tumor approach. It seems to be of particular interest in selected cases in which there are concerns about the patient's total blood volume, as in infants with potential hemorrhagic tumors and when it is possible to preoperatively identify a single vascular pedicle that can be approached early in the surgery.

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David I. Sandberg, Mark A. Edgar and Mark M. Souweidane

Object. Convection-enhanced delivery (CED) can be used safely to achieve high local infusate concentrations within the brain and spinal cord. The use of CED in the brainstem has not been previously reported and may offer an alternative method for treating diffuse pontine gliomas. In the present study the authors tested CED within the rat brainstem to assess its safety and establish distribution parameters.

Methods. Eighteen rats underwent stereotactic cannula placement into the pontine nucleus oralis without subsequent infusions. Twenty rats underwent stereotactic cannula placement followed by infusion of fluorescein isothiocyanate (FITC)—dextran at a constant rate (0.1 µl/minute) until various total volumes of infusion (Vis) were reached: 0.5, 1, 2, and 4 µl. Additional rats underwent FITC—dextran infusion (Vi 4 µl) and were observed for 48 hours (five animals) or 14 days (five animals). Serial (20-µm thick) brain sections were imaged using confocal microscopy with ultraviolet illumination, and the volume of distribution (Vd) was calculated using computer image analysis. Histological analysis was performed on adjacent sections.

No animal exhibited a postoperative neurological deficit, and there was no histological evidence of tissue disruption. The Vd increased linearly (range 15.4–55.8 mm3) along with increasing Vi, with statistically significant correlations for all groups that were compared (p < 0.022). The Vd/Vi ratio ranged from 14 to 30.9. The maximum cross-sectional area of fluorescence (range 9.8–20.9 mm2) and the craniocaudal extent of fluorescence (range 2.8–5.1 mm) increased with increasing Vi.

Conclusions. Convection-enhanced delivery can be safely applied to the rat brainstem with substantial and predictable Vds. This study provides the basis for investigating delivery of various candidate agents for the treatment of diffuse pontine gliomas.

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Jeremy C. Wang, Linda Heier and Mark M. Souweidane

Object. Suprasellar arachnoid cysts present unique management problems. The authors retrospectively reviewed six cases, in which endoscopic ventriculocystocisternotomy was performed, to identify specific neuroimaging features that aid both the accurate diagnosis of this entity and the postoperative assessment of fenestration patency.

Methods. Six consecutive children underwent treatment for suprasellar arachnoid cysts. Consistent radiographic features in all cases were identified. Through a single entry site, endoscopic fenestration was performed at both the apical and basal cyst membranes. Outcome was assessed using clinical examination, quantitative changes in cyst size, and triplanar magnetic resonance (MR) imaging with flow-sensitive (long TR) sequences.

In every case, the suprasellar cysts displayed three diagnostic MR imaging features: 1) vertical displacement of the optic chiasm/tracts; 2) upward deflection of the rostral mesencephalon and mammillary bodies; and 3) effacement of the ventral pons. Two patients initially underwent placement of a ventriculoperitoneal shunt before the cysts were recognized, but MR images obtained after shunt placement revealed the cysts. In a mean follow-up period of 26.2 months, all patients improved clinically. Postoperative imaging revealed a mean cyst volume decrease of 52.7% and a return to more normal suprasellar and prepontine anatomy. Flow-sensitive MR imaging confirmed pulsation artifact at all 12 fenestration sites. There was no surgery-related death and no additional cerebrospinal fluid diversion procedure was required.

Conclusions. To aid in the accurate diagnosis of prepontine arachnoid cysts, the authors identified several pathognomonic features on sagittal MR images: vertical deflection of the optic chiasm and mammillary bodies, as well as pontine effacement. Dual endoscopic fenestration into the intraventricular compartment and basal cistern is safe, and it effectively provides symptomatic relief by decreasing the cyst size. Triplanar flow-sensitive MR imaging sequences can confirm fenestration patency without the need for cine-mode MR imaging.

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Jothy Kandasamy and Mark Souweidane

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Mark M. Souweidane, Caitlin E. Hoffman and Theodore H. Schwartz

Object

Intraventricular anatomy has been detailed as it pertains to endoscopic surgery within the third ventricle, particularly for performing endoscopic third ventriculostomy (ETV) and endoscopic colloid cyst resection. The expanding role of endoscopic surgery warrants a careful appraisal of these techniques as they relate to frequent anatomical variants. Given the common occurrence of cavum septum pellucidum (CSP) and cavum vergae (CV), the endoscopic surgeon should be familiar with that particular anatomy especially as it pertains to surgery within the third ventricle.

Methods

From a prospective database of endoscopic surgical cases were selected those cases in which the defined pathology necessitated surgery within the third ventricle and there was coexistent CSP and CV. Pertinent radiographic studies, operative notes, and archived video files were reviewed to define the relevant anatomy. Features of the intracavitary anatomy were assessed regarding their importance in approaching the third ventricle.

Results

Four cases involving endoscopic surgery within the third ventricle (2 colloid cyst resections and 2 ETVs) were identified in which the surgical objective was accomplished through a septal cavum. In each case the width of the body of the lateral ventricle was reduced and the foramen of Monro was obscured. Because of the ventricular distortion, a stereotactic transcavum route was used for approaching the third ventricle. Entry into the third ventricle was accomplished through an interforniceal fenestration immediately behind the anterior commissure. The surgical goal was met in each case without any neurological change or postoperative morbidity. During the follow-up period, there has been no recurrence of a colloid cyst and no need of a secondary cerebrospinal fluid diversionary procedure.

Conclusions

In the presence of a CSP and CV, endoscopic navigation into the third ventricle can be problematic via a transforaminal approach. Alternatively, a transcavum interforniceal route for endoscopic surgery in the third ventricle is suggested, with the rostral lamina and the anterior commissure as important anatomical landmarks. Endoscopic third ventriculostomy and endoscopic colloid cyst resection performed via a transcavum interforniceal route in patients with a coexistent septal cavum is a feasible and safe option.

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Editorial

Anterior third ventriculostomy: an endoscopic variation on a theme

Mark M. Souweidane

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Neal Luther, Anders Cohen and Mark M. Souweidane

Object

Concern regarding the ability to accomplish adequate hemostasis during intracranial neuroendoscopy is often cited as a potential obstacle for primary endoscopic tumor management. In this study, the rate of clinically significant hemorrhage encountered as a result of endoscopic surgery for an intraventricular brain tumor is examined.

Methods

A total of 86 patients underwent an endoscopic biopsy procedure or resection of an intraventricular tumor. Recognized hemorrhagic sequelae occurred at a rate of 3.5% per patient. Visual obscuration due to the presence of intraventricular bleeding necessitated aborting the procedure before completion of the objective in two cases. There was a hemorrhagic event resulting in relevant morbidity in one patient, who suffered a bilateral diencephalic stroke after attempted tumor biopsy sampling.

Conclusions

The low hemorrhagic complication rate described in this series counters the misconception surrounding ineffective hemostasis during intracranial endoscopy for tumors and provides further evidence that this minimally invasive approach is a safe alternative to some conventional intracranial approaches.

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Jeffrey P. Greenfield and Mark M. Souweidane

Object

Endoscopic fenestration has been recognized as an accepted treatment choice for patients with symptomatic arachnoid cysts. The success of this procedure, however, is greatly influenced by individual cyst anatomy and location as well as the endoscopic technique used. This review was conducted to assess what variables influence the treatment success for different categories of arachnoid cysts.

Methods

Thirty-three consecutive patients who underwent endoscopic fenestration for treatment of an intracranial arachnoid cyst were identified from a prospective database. The surgical indications and techniques were reviewed, and surgical success rates and patient outcomes were assessed. Specific examples of each cyst category are included to illustrate the technical aspects of endoscopic cyst fenestration.

Endoscopic fenestration of arachnoid cysts was successful when judged by cyst decompression, and symptom resolution was noted in 32 (97%) of 33 cases. The one patient with short-term treatment failure underwent a successful repetition of the operation. There were no surgery-related morbidities or deaths.

Conclusions

Arachnoid cysts are a relatively benign pathological entity that can be managed by performing endoscopically guided cyst wall fenestrations into the ventricular system or cerebrospinal fluid–containing cisterns. Proper patient selection, preoperative planning of endoscope trajectory, use of frameless navigation, and advances in endoscope lens technology and light intensity combine to make this a safe procedure with excellent outcomes.