Transcavum septum pellucidum interforniceal approach for the colloid cyst of the third ventricle

Transseptal interforniceal endoscopic removal of superiorly recessed colloid cysts

OBJECTIVE

Transforaminal endoscopic colloid cyst resection is well described. However, some anatomical colloid cyst variants may warrant a modified approach. Rarely, colloid cysts separate the forniceal columns and grow superiorly within the leaflets of the septum pellucidum. Thus, the authors' goal was to characterize the imaging features, clinical presentation, surgical strategy, and outcomes of patients with this superiorly recessed colloid cyst variant.

METHODS

A retrospective evaluation of patients who underwent endoscopic resection of colloid cysts from 1999 to 2020 was performed. The patients were dichotomized depending on whether the cyst was located predominately below the forniceal columns or was superiorly recessed (forniceal column separation with variable intraseptal extension). This comparative cohort study focused on clinical presentation, imaging features, operative technique, and patient outcome.

RESULTS

In total, 182 patients were identified. Seventeen patients had colloid cysts that were defined as superiorly recessed and underwent transseptal interforniceal removal, and 165 patients underwent a standard transforaminal approach. Patients had similar demographic characteristics. However, transseptal cysts were on average larger (17.8 mm vs 11.4 mm, p < 0.0001), and these patients had a greater frontal-occipital horn ratio (0.45 vs 0.41, p = 0.012). They were also more likely to have undergone a previous resection (p = 0.02). The two cohorts had similar surgical outcomes, with no differences in extent of resection, recurrence, or complications.

CONCLUSIONS

Superiorly recessed intraseptal colloid cysts are larger and tend to splay the bodies of the fornix, thus requiring a parasagittal transseptal interforniceal endoscopic approach. This achieves complete removal with comparatively negligible morbidity or rare recurrence (5.9%).

Excision of Colloid Cyst through Interhemispheric, Transcallosal, Transcavum, Interfornicial Approach

Colloid cysts (CC) occur predominantly in the midline with majority involving roof of the third ventricle. In cases of cavum septum pellucidum (CSP), the surgeon can lose orientation when normal intraventricular structures are not encountered during surgery. We report a patient with CSP, who underwent right frontal parasagittal craniotomy, interhemispheric, transcallosal approach to reach the lesion. Lesion may not be seen in its usual location of foramen of Monroe, and entering the cavum may be confusing because no intraventricular landmarks will be seen. Excision of the cyst through the cavum usually requires interfornicial approach, and this structure must be separated gently to avoid injury.

Perspectives on Endoscopic Transseptal Interforniceal Approach for Retroforaminal Colloid Cysts

BACKGROUND

Although the interforniceal approach with the preservation of the fornix is useful during the endoscopic approach for retroforaminal colloid cysts, it carries a significant risk of memory and cognitive difficulties. Because most reports have reported the endoscopic approach to colloid cysts through the foramen with little emphasis on retroforaminal cysts, the aim of this study was to investigate colloid cysts as a special entity with regard to their different characteristics and surgical approaches and outcomes.

METHODS

In this retrospective study, 12 patients with third ventricular colloid cysts with retroforaminal extensions were included. All patients underwent endoscopic transseptal interforniceal approach with tumor resection. The surgical technique was briefly described, and preoperative and postoperative data were evaluated.

RESULTS

Among the 12 patients included in this study, most of our patients were males. Average diameter of the colloid cyst was relatively large (average 22 mm). Gross total resection was achieved in 10 cases (83.3%). The stable images showed no local recurrence in the long-term follow-up period except in 1 case at the 28-month follow-up period.

CONCLUSIONS

Retroforaminal colloid cyst represents a unique entity that requires special attention to its mode of growth. The endoscopic approach for retroforaminal colloid cysts is nearly the same as that for foraminal cysts. It has a lower incidence rate of postoperative memory changes, lower chances of total resection, and lower incidence rate of hard contents. Moreover, sufficient knowledge on morbid anatomy is important to avoid fornix injury.

Feasibility and Challenges of Microsurgical Resection of Colloid Cysts in Patients with Preexisting Ventriculoperitoneal Shunts

BACKGROUND

Colloid cysts are the most common third ventricular tumor and may present with symptoms related to obstructive hydrocephalus. Although definitive endoscopic or microsurgical resection is the standard of care, patients may receive temporizing ventriculoperitoneal shunts when definitive management is deferred. Subsequent definitive treatment can be challenging because of the ventricular collapse and narrowing of the operative corridor. There is currently no literature evaluating the feasibility of definitive colloid cyst resection in patients with preexisting ventriculoperitoneal shunts.

METHODS

We retrospectively reviewed records for patients undergoing colloid cyst resection between 2009 and 2019 to identify patients with preexisting shunts prior to surgery.

RESULTS

Three patients had preexisting ventriculoperitoneal shunts. Two patients had been shunted at outside institutions where microsurgical or endoscopic resection was not available. One patient received a shunt from an outside surgeon when she was deemed a poor surgical candidate because of cardiac instability. All 3 patients underwent successful gross total colloid cyst resection via the transcallosal approach without recurrences during a mean follow-up of 4.2 years. All patients had intact cognitive and memory function and returned to work.

CONCLUSIONS

Surgical resection of colloid cysts is possible despite a preexisting ventriculoperitoneal shunt. Because the ventricular space may be collapsed postoperatively because of cerebrospinal fluid diversion, a transcortical route (either endoscopic or microscopic) can be complicated by a small operative corridor with reduced visibility. The transcallosal approach was safe and feasible in these cases for providing midline access with adequate visualization for complete resection despite ventricular collapse.

Microsurgical resection of tumors of the lateral and third ventricles: operative corridors for difficult-to-reach lesions

Tumors of the lateral and third ventricles are cradled on all sides by vital vascular and eloquent neural structures. Microsurgical resection, which always requires attentive planning, plays a critical role in the contemporary management of these lesions. This article provides an overview of the open microsurgical approaches to the region highlighting key clinical perspectives.

Susceptibility-Weighted Imaging of the Anatomic Variation of Thalamostriate Vein and Its Tributaries

Background and Purpose

Thalamostriate vein (TSV) is an important tributary of the internal cerebral vein, which mainly drains the basal ganglia and deep medulla. The purpose of this study was to explore the anatomic variation and quality of TSV and its smaller tributaries using susceptibility-weighted imaging (SWI).

Methods

We acquired SWI images in 40 volunteers on a 3.0T MR system using an 8-channel high-resolution phased array coil. The frequencies of the TSV and its tributaries were evaluated. We classified TSV into types I (forming a venous angle) and II (forming a false venous angle). We classified anterior caudate vein (ACV)into types 1 (1 trunk) and 2 (2 trunks) as well as into types A (joiningTSV), B (joining anterior septal vein), and C (joining the angle of both veins).

Results

The TSV drains the areas of caudate nucleus, internal capsule,lentiform nucleus, external capsule, claustrum, extreme capsule and the white matter of the frontoparietal lobes,except thalamus. The frequencies of the TSV, ACV and transverse caudate vein (ACV) were 92.5%, 87.5% and 63.8%, respectively. We found TSV types I and II in 79.7%, and 20.3% with significantly different constitution ratios (P< 0.05). The most common types of ACV were type 1 (90.0%) and type A (64.3%).

Conclusion

The complex three-dimensional (3D) venous architecture of TSV and its small tributaries manifests great variation, with significant and practical implications for neurosurgery.

Colloid cysts posterior and anterior to the foramen of Monro: Anatomical features and implications for endoscopic excision

Background:

Colloid cysts are usually located at the rostral part of the third ventricle in proximity to the foramina of Monro. Some third ventricular colloid cysts, however, attain large sizes, reach a very high distance above the roof of the third ventricle, and pose some challenges during endoscopic excision. These features led to the speculation that for such a pattern of growth to take place, the points of origin of these cysts should be at areas away from the foramina of Monro at which some anatomical “windows” exist that are devoid of compact, closely apposed forniceal structures.

Methods:

A review of the literature on anatomical variations of the structures in the vicinity of the roof of the third ventricle and on reported cases with similar features was conducted.

Results:

Colloid cysts may grow vertically up past the roof of the third ventricle through anatomical windows devoid of the mechanical restraint of the forniceal structures.

Conclusion:

Some anatomical variations of the forniceal structures may allow unusually large sizes and superior vector of growth of a retro- or post-foraminal colloid cyst. Careful preoperative planning and knowledge of the pertinent pathoanatomy of these cysts before endoscopic excision is very important to avoid complications.

Optimized surgical approach to third ventricular choroid plexus papillomas of young children based on anatomical variations

BACKGROUND

Choroid plexus papilloma (CPP) in the third ventricle is a rare benign intracranial tumor.

METHODS

We report 3 pediatric cases of CPP in the third ventricle. The lesions were totally removed by a different surgical approach in each case.

RESULTS

When remarkable hydrocephalus is present, the transcortical approach is easier to perform, but may expose the patient to epilepsy and subdural effusion postoperatively. The transcallosal approach offers direct exposure of the ventricle system with minimal risk of cortical damage. The transcallosal-transforaminal approach with posterior enlargement of the foramen of Monro along the choroidal fissure provides a direct trajectory into the third ventricle through the natural cleft. The transcallosal-interforniceal approach does not depend on the size of the foramen of Monro, but it carries a risk for damage to the both fornices. The midline plane of the septum pellucidum and the forniceal columns in children are sometimes easily identifiable and separable, and in such cases the transcallosal-interforniceal approach appears to be a safe route for tumors extending to the posterior third ventricle. The interforniceal approach should be reserved for lesions that cannot be removed safely via the transforaminal approach.

CONCLUSIONS

Young children have a small total blood volume and fragile cardiovascular status. Therefore, it is critical to preserve the venous system and to ligate the feeding artery before extirpation of the tumor. The surgical approach to the third ventricular CPPs should be tailored to individual children based on tumor size, location, and vascularity.

Transcavum interforniceal endoscopic surgery of the third ventricle

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.