Meningiomas of the velum interpositum: surgical considerations

Endoscopic trans-septal interforniceal approach for excision of colloid cysts of the third ventricle using the rotational technique

Colloid cysts of the third ventricle are benign intracranial lesions that account for 0.5 to 2% of all brain tumors and are even rarer in pediatric population. Dandy was the first to successfully excise a colloid cyst of the third ventricle via a transcortical transventricular approach in 1921. For several decades to follow, the transcortical transventricular and transcallosal microsurgical approaches remained the cornerstone of surgical management of these lesions. With time and refinements in endoscopic equipment and techniques, endoscopic resection of colloid cysts evolved into a currently well-established and appealing minimally invasive alternative to microsurgery. Endoscopic endochannel techniques for colloid cysts of the third ventricle may either be transforaminal or trans-septal interforniceal, depending on the pathoanatomical features of the colloid cyst and its relation to the juxtaposed anatomical structures. The endoscopic trans-septal interforniceal approach is required to access the rare subset of colloid cysts that extend superior to the roof of the third ventricle between the two fornices insinuating themselves between the leaflets of the septum pellucidum. In this article, the surgical technique of the endochannel endoscopic trans-septal interforniceal approach is elaborated upon. A representative case is presented along with an operative video.

Primary Stereotactic Radiosurgery Provides Favorable Tumor Control for Intraventricular Meningioma: A Retrospective Analysis

The surgical resection of intraventricular meningiomas (IVMs) remains challenging because of their anatomically deep locations and proximity to vital structures, resulting in non-negligible morbidity and mortality rates. Stereotactic radiosurgery (SRS) is a safe and effective treatment option, providing durable tumor control for benign brain tumors, but its outcomes for IVMs have rarely been reported. Therefore, the goal of the present study was to evaluate the SRS outcomes for IVMs at our institution. This retrospective observational study included 11 patients with 12 IVMs with a median follow-up period of 52 months (range, 3-353 months) treated with SRS using the Leksell Gamma Knife. Nine (75%) tumors were located in the trigone of the lateral ventricle, two (17%) in the body of the lateral ventricle, and one (8%) in the third ventricle. Tumor control was achieved in all cases, and seven (55%) decreased in size. Post-SRS perifocal edema was observed in four (37%; three asymptomatic and one symptomatic but transient) patients, all of which were resolved by the last follow-up. SRS appears to provide safe and excellent tumor control for IVMs. A longer follow-up with a larger number of cases is desired for a more solid conclusion.

Falcotentorial Meningiomas: Optimal Surgical Planning and Intraoperative Challenges - Case Report and a Review

Meningiomas arising from the falcotentorial junction are rare, and the selection of the optimal surgical approach is essential. We report a falcotentorial meningioma (FTM) case approached by occipitotranstentorial resection and subtotal tumor resection presenting a satisfactory clinical outcome. The present review sought to reveal the current knowledge regarding the clinical presentation, radiological imaging, and the microsurgical anatomy of FTMs as a form of improving the surgical approach. The selection of the optimal surgical approach is essential for the safe and effective removal of an FTM. Preoperative imaging analysis should identify the anatomical relations of the tumor and guide toward the least disruptive route that preserves the neurovascular structures.

Occipital Interhemispheric Transtentorial Approach for a Pineal Region Meningioma with Pseudobulbar Palsy

Meningiomas represent 8%-10% of all pineal region (PR) tumors. When they arise from the falx, tentorium, or tentorial incisura, they are not always considered a true PR tumor, as they do not originate from it but instead only grow toward the region. The true meningioma of PR must be originated from the arachnoid envelope of the pineal gland or from the 2 leaflets of the velum interpositum. In both conditions there are no dural attachments.^1,2 Occipital interhemispheric transtentorial and supracerebellar infratentorial are the 2 main approaches for tumors within this region. Aside from the surgeon's preference, the position of the venous system and the direction of the tumor growth guide the approach choice. Endoscope assistance can help reach areas unable to be visualized under the microscope.^3-5 We report the case of a 37-year-old female with a large PR meningioma (velum interpositum) presenting with intense dysphagia, dysphonia, and bilateral tongue palsy. Given the affected bilateral upper motor tracts associated with bulbar symptoms, a diagnosis of pseudobulbar palsy was considered.^6,7 Preoperative imaging also showed compression of the deep venous system. The patient underwent a total resection of the tumor via an occipital interhemispheric transtentorial approach and exhibited a dramatic recovery of neurologic symptoms after the surgery (Video 1). Postoperative venogram showed restoration of the usual deep venous system pattern, which may be associated with significant neurologic improvement. Careful management of the deep veins is mandatory during the resection of PR meningiomas. The venous system improvement after the surgery may be associated with the dramatic recovery seen in this unique case. The patient consented to publication of her images.

Combined Microscopic and Endoscopic Surgery for Pineal Region Meningiomas Using the Occipital-Parietal Transtentorial Approach

Objective

Pineal region meningiomas are deeply located and adjacent to critical neurovascular structures, making them one of the most challenging areas to access. The authors presented a combined microscopic and endoscopic surgery and investigated its value in resecting pineal region meningiomas.

Methods

Twelve patients with pineal region meningiomas from February 2017 to December 2020 were retrospectively reviewed. All patients underwent combined microscopic and endoscopic surgery using the occipital-parietal transtentorial approach. Perioperative clinical, surgical, and radiographic data were collected.

Results

The endoscope provided a wider view and increased visualization of residual tumors. All tumors were completely resected, and none of the patients died. Total resection was believed to have been achieved in four patients, but the residual tumor was detected after endoscopic exploration and was completely resected with an endoscope. Only one patient had transient visual field deficits. No recurrence was observed during follow-up.

Conclusions

Combined microscopic-endoscopic surgery for pineal region meningiomas eliminates microscopic blind spots, thus compensating for the shortcomings of the traditional occipital transtentorial approach. It is a promising technique for minimally invasive maximal resection of pineal region meningiomas.

Pineal Region Meningioma in a Very Young Child

INTRODUCTION

Meningiomas in childhood are infrequently seen. Furthermore, they are extremely rare at a pineal location with few reported cases above 5-years of age. We present a very young child with a large pineal region meningioma which mimicked the usually occurring pathologies at this site.

CASE PRESENTATION

A 2.5-year-old child presented with symptoms of raised intracranial pressure. MRI demonstrated a homogenously enhancing pineal lesion with small cystic areas. After an initial cerebrospinal fluid evaluation for germ cell tumors, the child underwent excision of the lesion by the Krause approach. The tumor showed no definitive dural attachment, had well-defined arachnoid interface, and was completely excised. The final histopathology was meningioma.

CONCLUSION

Although unusual, we highlight the importance of considering meningiomas among the childhood pineal region lesions, given their good outcome with total resection. Also, pertinent brief literature of the pediatric pineal region meningiomas has been provided. An assessment of preoperative and intraoperative features (clear arachnoid plane) along with adjuncts such as frozen studies can help discern various entities of this region, and decide the extent of excision.

Surgical treatment of falcotentorial meningiomas: a retrospective review of a single-institution experience

OBJECTIVE

Meningiomas at the falcotentorial junction represent a rare subgroup of complex meningiomas. Debate remains regarding the appropriate treatment strategy for and optimal surgical approach to these tumors, and surgical outcomes have not been well described in the literature. The authors reviewed their single-institution experience in the management, approach selection, and outcomes for patients with falcotentorial meningiomas.

METHODS

From the medical records, the authors identified all patients with falcotentorial meningiomas treated with resection at the Barrow Neurological Institute between January 2007 and October 2017. Perioperative clinical, surgical, and radiographic data were retrospectively collected. For patients who underwent the supracerebellar infratentorial approach, the tentorial angle was defined as the angle between the line joining the nasion with the tuberculum sellae and the tentorium in the midsagittal plane.

RESULTS

Falcotentorial meningiomas occurred in 0.97% (14/1441) of the patients with meningiomas. Most of the patients (13/14) were female, and the mean patient age was 59.8 ± 11.3 years. Of 17 total surgeries (20 procedures), 11 were single-stage primary surgeries, 3 were two-stage primary surgeries (6 procedures), 2 were reoperations for recurrence, and 1 was a reoperation after surgery had been aborted because of brain edema. Hydrocephalus was present in 5 of 17 cases, 4 of which required additional treatment. Various approaches were used, including the supracerebellar infratentorial (4/17), occipital transtentorial/transfalcine (4/17), anterior interhemispheric transsplenial (3/17), parietal transventricular (1/17), torcular (2/17), and staged supracerebellar infratentorial and occipital transtentorial/transfalcine (3/17) approaches. Of the 17 surgeries, 9 resulted in Simpson grade IV resection, and 3, 1, and 4 surgeries resulted in Simpson grades III, II, and I resection, respectively. The tentorial angle in cases with Simpson grade I resection was significantly smaller than in those with an unfavorable resection grade (43.3° ± 4.67° vs 54.0° ± 3.67°, p = 0.04). Complications occurred in 10 of 22 approaches (17 surgeries) and included visual field defects (6 cases, 2 permanent and 4 transient), hemiparesis (2 cases), hemidysesthesia (1 case), and cerebellar hematoma (1 case).

CONCLUSIONS

Falcotentorial meningiomas are challenging lesions. A steep tentorial angle is an unfavorable preoperative radiographic factor for achieving maximal resection with the supracerebellar infratentorial approach. Collectively, the study findings show that versatility is required to treat patients with falcotentorial meningiomas and that treatment goals and surgical approach must be individualized to obtain optimal surgical results.

Reinvestigation of the origins of pineal meningiomas based on its related veins and arachnoid membranes

BACKGROUND

A series of patients harboring pineal region meningiomas were respectively analyzed to explore the origin of these tumors and the true meaning of the term "velum interpositum (VI) meningiomas".

METHODS

21 patients with pineal meningiomas underwent operation in Nanfang Hospital of Southern Medical University from January 2005 to December 2016 were retrospectively included to analyze the clinical features, imaging findings and surgical video data of these patients. According to the method of literature, the data of this group were also divided into falcotentorial (FT) meningiomas and VI meningiomas, and the differences between the two types of tumors were compared.

RESULTS

Among the 21 cases of tumor, there were 12 cases of FT meningiomas, including 4 cases originating from cerebral falx, 4 cases from tentorium of cerebellum and 4 cases from straight sinus; there were 9 cases of VI meningiomas, 7 of which originated from the arachnoid sleeve of the Galen vein, 1 from the posterior part of the internal cerebral vein and 1 from the posterior surface of the pineal gland. Postoperative pathological examination showed meningiomas in all the 21 patients, including 16 cases of total resection and 5 cases of subtotal resection. Postoperatively limitation of binocular vertical motion was found in 3 cases, homotropic hemianopia in 7 cases, hemiplegia in 1 case and death in 1 case.

CONCLUSIONS

This study suggests that pineal meningiomas are more suitable to be described by FT meningioma and meningiomas of the arachnoid of the pineal region by analyzing the origin of tumors. The term "VI meningiomas" can only reflect a part of meningiomas of the arachnoid of the pineal region. Before the removal of pineal meningiomas, more attention should be paid to the effects of the two types of tumors on the Galen vein and the straight sinus, and the establishment of venous collateral circulation.

Calcifications of the Medial Choroid in the Velum Interpositum: An Unrecognized Site of Physiologic Calcifications Evident on Multidetector Computed Tomography

OBJECTIVE

In adult patients undergoing multidetector computed tomography (CT) of the brain, we observed linear calcification along the deep venous system on thin (<3 mm) sagittal reconstructions. We found no reports of this finding in the velum interpositum (VI) in the imaging literature. We performed a focused examination of the VI on 2 autopsy cases and retrospectively reviewed sagittal, thin-section reconstructions of CT scans of 273 consecutive adult patients.

METHODS

On 2 routine autopsies of the brain, sampling and histologic evaluation was performed of structures within the VI. A series of 273 unselected, sequentially acquired clinical head CT scans of patients ≥60 years old were retrospectively reviewed on a three-dimensional workstation to determine the incidence of this finding and its correlation with patient age.

RESULTS

In 1 of the autopsy cases, calcified choroid plexus was identified in the region of the VI; this was also visible on the patient's premorbid CT. In the series of CT scans, linear calcification of ≥9 mm along the deep venous system was evident in 24.5% of cases. The median age of the cases without calcifications was 72 years, while the median age of the cases with calcification was 82; this difference was statistically significant (χ², P < 0.0005).

CONCLUSIONS

Evidence supports that linear midline calcification along the internal cerebral veins represents age-related, physiologic calcification of extraventricular choroid plexus within the VI. Awareness of this previously unreported finding on CT will prevent mistaking these physiologic calcifications on CT for evidence of underlying venous pathology. This finding provides additional support that the midline choroid plexus lies within the VI rather than in the third ventricle and expands our understanding of the detailed anatomy of the VI.

Multistaged, multidirectional strategy for safe removal of large meningiomas in the pineal region

OBJECTIVE Pineal region meningiomas are rare and tend to be discovered only after they grow. Several simultaneous multidirectional approaches performed as a single operation have been proposed, but the best strategy to remove these deeply situated large meningiomas involving the deep vital venous system remains to be established. The authors advocate a multistaged, multidirectional approach to safely remove these challenging tumors. METHODS Four consecutive cases of meningioma in the pineal region were treated between April 2013 and June 2016. The 3 large (> 40 mm diameter) tumors were removed via multistaged, multidirectional approaches (2 surgeries in 2 patients and 3 surgeries in 1 patient) with gravity retraction of the occipital or parietal lobe. The large occipital skin incision extending bilaterally was used for the next operation from the contralateral side. Combinations of the occipital transtentorial approach with or without the transfalcine approach, occipital bitranstentorial/falcine approach, combined supra-/infratentorial transsinus approach, and contralateral parietal interhemispheric transcallosal approach were used. RESULTS Transient visual field deficits occurred after 2 of the 8 operations, but all tumors were removed grossly or subtotally without permanent surgery-related morbidity. The galenic venous system and straight sinus remained intact in all patients. During the follow-up period (mean 29.5 months [range 13-52 months]), there were no recurrences after the final operation. CONCLUSIONS A multistaged, multidirectional strategy with an intentional large occipital scalp incision and gravity retraction of the occipital lobe is a good choice for the safe removal of large meningiomas in the pineal region.

Third ventricle World Health Organization Grade II meningioma presenting with intraventricular hemorrhage and obstructive hydrocephalus: A case report and literature review

Background:

Third ventricular meningiomas are exceedingly rare intracranial tumors that may present with intraventricular hemorrhage.

Case Description:

The patient is 46-year-old who initially presented with obstructive hydrocephalus from a presumed vascular lesion and who was treated with endoscopic third ventriculostomy. He presented 3 years later with acute intraventricular hemorrhage and hydrocephalus. The hemorrhage was evacuated and the third ventricular tumor was resected, and the patient made an excellent recovery. Histopathological analysis identified the tumor as the World Health Organization Grade II meningioma.

Conclusion:

Third ventricular meningioma is a rare tumor that may present with hemorrhage and obstructive hydrocephalus. Surgical resection can be helpful for this rare presentation of intracranial meningioma.

Meningiomas Originated at the Falcotentorial Region: Analysis of Topographic and Diagnostic Features Guiding an Optimal Surgical Planning

BACKGROUND

Meningiomas arising at the pineal region are a rare entity and still represent a great neurosurgical challenge given their deep location and critical neuroanatomic relationships. The optimal surgical approach to treat these lesions is still under debate. Our objective is to review the topographic and diagnostic features of these lesions, which can help to guide an optimal surgical outcome.

METHODS

We present 2 clinical cases of falcotentorial meningiomas successfully treated at our institution (2016-2017) with different surgical approaches. A literature review is performed, and a description of the classification, anatomic relationships, clinical features, diagnosis, and different surgical options and outcomes of these lesions is presented.

RESULTS

The first patient was treated via a supracerebellar infratentorial approach, and the second patient was treated via a parieto-occipital interhemispheric approach. In both tumors, a gross total resection was achieved with no permanent neurologic deficits. In the literature review, gross total resection rates range from 33% to 100%, with no differences regarding the type of meningioma or the surgical approach performed. Permanent neurologic morbidity varies from 0% to 50%, and mortality rates range from 0% to 23%. The distortion and displacement of the vein of Galen and straight sinus represent the most important feature in the decision of optimal surgical approach.

CONCLUSIONS

Pineal region meningiomas represent very infrequent, challenging lesions, and their description in the literature is scarce. The systematic topographic classification of these tumors and evaluation of the neuroanatomic structures involved are crucial to guide a safe and optimal surgical approach and achieve satisfactory outcomes.

Surgical Management of Anterolateral and Posteromedial Incisural Tentorial Meningioma

BACKGROUND

Tentorial meningiomas are a broad and consistent category of tumors but their definition is still unclear and their classification uncertain.

OBJECTIVE

To report the clinical and surgical characteristics of tentorial hiatus meningiomas based on a revised classification of tentorial meningiomas.

METHODS

We reviewed the records of 14 patients who had undergone microsurgical removal of incisural tentorial meningioma. Two tumor subgroups, anterolateral (AL) and posteromedial (PM), were distinguished according to their site of attachment: the middle third and the posterior third of the tentorial free margin, respectively. Clinical presentation, radiological findings, surgical approaches, extent of resection, and outcome were compared.

RESULTS

The 2 subgroups differed by tumor size (larger in PM), incidence of the direction of growth (infratentorial in PM), and hydrocephalus (only in PM), as well as by some clinical aspects. Surgical approach depended on tumor location: lateral (pterional, subtemporal, and retromastoid) for AL lesions; medial (occipital or supracerebellar infratentorial) for PM lesions. Total removal (Simpson grade I-II) was performed in 64% of cases and complications occurred in 14%. Stereotactic radiosurgery was performed in cases of incomplete resection. At a mean follow-up of 104.5 mo, clinical improvement with low recurrence (9%) was achieved.

CONCLUSION

Reallocation of tentorial edge meningiomas is the premise to compare treatment and further improve the approach case-by-case. In spite of their deep site, good outcomes can be achieved in both AL and PM tentorial meningiomas. Also of note is the indolent behavior of residual tumor.

Primary intraventricular meningiomas in children-experience of two cases with review of literature

Meningiomas are rare in the pediatric age group, more so in the intraventricular location. They arise in the lateral ventricles from the arachnoid cells contained within the choroid plexus, in the third ventricle from the velum interpositum and in the fourth ventricle from the choroids. These tumors are usually large and have an aggressive behaviour. Surgical management of intra-ventricular meningiomas is challenging because of their deep location, large size at presentation and increased vascularity. The authors report two such cases who presented with symptoms of raised intra cranial pressure and on evaluation were found to have associated hydrocephalus. Both these patients underwent surgical excision of the tumour by frontal transcortical approach and histopathology report confirmed transitional meningioma in them. Only twenty seven cases of intraventricular meningiomas in children have been reported till date. Their definitive treatment is surgery alone and total excision of the tumor is curative. Possibility of neurofibromatosis as a differential should also be considered in their management.

Cystic meningioma: radiological, histological, and surgical particularities in 43 patients

BACKGROUND

The presence of cysts is a rare occurrence for intracranial meningiomas in adults. We report our experience in a large consecutive series of cystic meningiomas.

METHOD

We prospectively collected data for a dedicated database of cystic meningioma cases between January 2004 and December 2011 in two tertiary neurosurgical centers. Studied data included preoperative imaging, surgical records, and pathology reports.

RESULTS

Among 1214 surgeries for intracranial meningioma, we identified 43 cases of cystic meningioma, corresponding to an incidence of 3.5 %. The most common localization was the hemispheric convexity (17/43 cases). Twenty-eight patients had intratumoral cysts, nine peritumoral, and five mixed intra and extratumoral. In 29 patients with available diffusion imaging, ADC coefficients were significantly lower in grade II-III tumors compared to grade I (p = 0.01). Complete resection of the cystic components was possible in 27/43 patients (63 %); partial resection in 4/43 (9 %); in 6/43 (14 %) cyst resection was not possible but multiple biopsies were performed from the cystic walls; in another 6/43 (14 %) the cystic wall was not identified during surgery. Cells with neoplastic features were identified within the cyst walls at pathology in 26/43 cases (60 %). All patients were followed-up for 24 months; long-term follow-up was available only in 32 patients for an average period of 49 months (range, 36-96 months). No recurrence requiring surgery was observed.

CONCLUSIONS

Cystic meningiomas are rare. Cells with neoplastic features are often identified within the cyst walls. Complete cyst resection is recommendable when considered technically feasible and safe.

Two cases of pineal-region meningiomas derived from arachnoid membrane over the vein of Galen without dural attachment

BACKGROUND

We present two rare cases of pineal-region meningiomas. These tumors are the first reported cases of dura-unrelated meningiomas originating from the arachnoid membrane over the vein of Galen (AMG).

CASE DESCRIPTION

In Case 1, a 37-year-old woman presented with a progressing headache. Magnetic resonance imaging (MRI) showed a large tumor in the pineal region, displacing the vein of Galen upward. Angiography disclosed occlusion of the vein of Galen, with deep venous flow draining through the veins on the right medial surface of the occipital lobe to the superior sagittal sinus. In Case 2, a 67-year-old man presented with dizziness. MRI demonstrated a large mass in the pineal region, displacing the vein of Galen inferiorly. Angiography disclosed occlusion of the vein of Galen, with deep venous flow draining through the collateral venous channel into the transverse sinus. Both tumors were totally excised (Simpson Grade III for Case 1, Grade I for Case 2) via a left occipital transtentorial approach. No dural attachment was recognized in either case, but the tumor in Case 1 was firmly adherent to the inferior portion of the AMG, while that in Case 2 was attached to the superior portion of the AMG, but remained dissectible.

CONCLUSIONS

We reported two cases of pineal-region meningiomas originating from the arachnoid membrane over the vein of Galen, resulting in meningioma without dural attachment. These tumors can be totally resected by careful dissection of the tumor from the arachnoid membrane surrounding the vein of Galen.

Meningioma of the superior leaflet of the velum interpositum: A case report

BACKGROUND

Meningiomas of the velum interpositum in the roof of the third ventricle are rare. Knowing from which leaflet the meningioma originates and thus its relationships with the internal cerebral and Galen veins, may help in choosing the surgical approach.

CASE DESCRIPTION

We report the case of a 40-year-old male with a meningioma arising from the superior leaflet of the velum interpositum. The tumor was resected successfully using the infratentorial-supracerebellar approach. Reviewing the literature, of the 22 reported cases of velum interpositum meningiomas, sufficient information regarding the precise location of the origin of the tumor was provided in 14 cases, all of which were from the inferior leaflet.

CONCLUSION

We report the first case of velum interpositum meningioma arising from the superior leaflet and give a potential explanation as to why meningiomas of the velum interpositum occur more commonly on the inferior leaflet. Distinguishing from which of the two leaflets the tumor originates may influence the surgical strategy.

Comparison of outcomes following complex posterior fossa surgery performed in the sitting versus lateral position

The sitting position during surgery is thought to provide important advantages, yet it remains controversial. We compared surgical and neurological outcomes for patients operated on in the sitting versus lateral position. Technically difficult procedures performed from the years 2001-2008 for complex lesions in the posterior fossa (vestibular schwannomas, other cerebellopontine angle tumors, foramen magnum meningiomas, brainstem cavernomas, pineal region tumors) were included. Outcomes in the two surgical positions were compared for all 243 patients (93 sitting, 38.3%; 150 lateral, 61.7%) and for 130/243 patients with vestibular schwannomas (50 sitting, 38.5%; 80 lateral, 61.5%). Sitting and lateral patient subgroups were clinically comparable. There were no surgical mortalities. The extent of removal and surgical and neurological outcomes were comparable. We found no advantage in surgical or neurological outcomes for use of the sitting or lateral surgical positions in technically difficult posterior fossa procedures. In vestibular schwannoma surgeries facial nerve preservation (House-Brackmann score 1-2) was related to extent of resection but not to surgical position. The choice of operative position should be based on lesion characteristics and the patient's preoperative medical status as well as the experience and preferences of the surgeons performing the procedure.

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.

Pineal region masses--imaging findings and surgical approaches

The anatomy of the pineal region is complex. Despite advances in surgical techniques since the first reported successful pineal region surgery in the early 20th century, pineal region surgery remains challenging owing to the proximity of deep cerebral veins and dorsal midbrain structures critical for vision. In this article, we review the relevant surgical anatomy of the pineal region and discuss historically important and current surgical approaches. We describe specific imaging features of pineal region masses that may affect surgical planning and review neoplastic and nonneoplastic masses that occur in the pineal region.

Giant velum interpositum meningioma in a child

Intraventricular meningiomas are rare, but are relatively more often seen in children. Large size at presentation often obscures anatomical details. A particular subset of such tumors arising from the velum interpositum pose a significant surgical challenge. Thorough preoperative imaging, especially with respect to the course of the deep venous structures, provides useful evidence as to the origin. Preservation of venous anatomy at surgery is vital. We describe a 3-year-old girl with a giant velum interpositum meningioma that was completely excised with excellent outcome. This is probably the youngest such case reported.

Arachnoid cyst of the velum interpositum originating from tela choroidea

BACKGROUND

Arachnoid cysts originating from the velum interpositum are very rare, and their existence as a clinicopathologic entity remains controversial. We report a case of a patient with an arachnoid cyst of the velum interpositum presenting with memory disturbance, focusing on the anatomical origin of the lesion and the physiological mechanisms causing memory disturbance.

CASE DESCRIPTION

A 65-year-old man with a large cystic lesion in the velum interpositum experienced progressive memory disturbance and enlargement of the lesion 6 months before referral to our institution. Neuropsychological evaluation on admission demonstrated severe memory disturbance. Radiological examination did not reveal hydrocephalus, but the bilateral fornices and thalami were compressed by the cyst. The patient underwent endoscopic cystoventriculostomy via the frontal horn of the right lateral ventricle through a frontal burr hole. Histopathology of the sample was consistent with that of an arachnoid cyst, and the endoscopic findings suggested that the cyst originated from the tela choroidea, which covers the velum interpositum. The symptoms resolved after surgery with significant improvement in neuropsychological test scores.

CONCLUSION

Arachnoid cysts of the velum interpositum are rare but distinct clinicopathologic entities that originate from the tela choroidea. The lesions can cause memory disturbance without hydrocephalus due to compression of the fornices and thalami, but this can be reversed by surgery.

Endoscopic anatomy of the velum interpositum: A sequential descriptive anatomical study

Background:

The velum interpositum and structures lying within and over it undergo morbid anatomical changes with hydrocephalus that have not been mentioned in the literature.

Objectives:

The aim of this article is to describe the diverse endoscopic anatomical findings for this surgically important region.

Materials and Methods:

One thousand five hundred and twenty cranial endoscopic procedures performed from September 1993 till March 2011 have been retrospectively reviewed. Anatomical `situm and covering layers have been reported in 40 cases.

Results:

The changes of the velum interpositum have four patterns. These are 1-Distraction mounting to disruption of layers, 2-Reverse in the normal curvature, 3-Reverse of the triangular shape with change in size, and 4-Cystic dilatation causing hydrocephalus.

Conclusion:

The velum interpositum and roof of the third ventricle are sites of changes associated with hydrocephalus that show specific patterns described in a sequential anatomical study.

The distribution of arachnoid membrane within the velum interpositum

BACKGROUND

There is as yet little knowledge as to the arachnoid architecture within the velum interpositum. The aim of this study was to clarify the distribution of the arachnoid membrane within the velum interpositum and its relationship with the arachnoid envelope over the pineal region.

METHODS

In seven adult cadaver heads, histological sections of the third ventricle roof, stained with Masson's trichrome stains, were studied under light microscopy.

RESULTS

Within the velum interpositum, there are two arachnoid layers. The dorsal layer of arachnoid membrane envelops the internal cerebral veins and fixes them to the surrounding tela choroidea as well as the ventral arachnoid layer. The ventral layer of arachnoid membrane is a direct anterior extension of the arachnoid envelope over the pineal region and covers the midline inferior layer of tela choroidea. Both arachnoid layers end near the foramen of Monro.

CONCLUSIONS

The membranous roof of the third ventricle comprises two layers of the tela choroidea and two arachnoid layers. These two arachnoid layers are derived from the arachnoid envelope over the pineal region.

Use of 3D-computed tomography angiography for planning the surgical removal of pineal region meningiomas using Poppen's approach: a report of ten cases and a literature review

BACKGROUND

There are several treatment approaches for pineal region meningiomas, such as Poppen's approach, Krause's approach and combinations of the two approaches. We present our experience with the use of 3D-computed tomography angiography for planning the surgical removal of pineal region meningiomas using a suboccipital transtentorial approach (Poppen's approach) and evaluate the role of Poppen's approach.

METHODS

During the period from January 2005 to June 2010, ten patients presented to us with pineal region meningioma. MRI was routinely used to define the tumor size, position, and its relevant complications while 3D-CTA was applied to define the blood supply of the tumor and the venous complex (VC) shift before operations. Most of the meningiomas had developed at both sides of the tentorial plane and extended laterally with typical characteristics of a pineal region tumor.

RESULTS

All tumors were completely removed surgically without any injury to the VC. Postoperative intracranial infection occurred in one case who recovered after antibiotics were given. Postoperative intraventricular hemorrhage and pneumocephalus were found in one case, but fully recovered after conservative treatment. In the nine cases of concurrent hydrocephalus, this was gradually relieved in eight patients and the single case that became aggravated was successfully treated with ventriculoperitoneal shunt. Moreover, the follow-up MRI examinations did not indicate any recurrence of the meningiomas.

CONCLUSION

We found that the use of Poppen's approach is strongly supported for the successful removal of pineal region meningiomas without serious complications.

Epidermoid cysts of the velum interpositum

The cistern of the velum interpositum is a space located between the corpus callosum dorsally and the roof of the third ventricle ventrally. Lesions located within the velum interpositum are rare and include meningiomas, pilocytic astrocytomas, atypical teratoid/rhabdoid tumors and arachnoid cysts. Epidermoid cysts in this location have not been reported previously. We report the clinical and radiological features of two patients with epidermoid cysts located in the velum interpositum. The patients presented with gait difficulty and features of raised intracranial pressure and magnetic resonance imaging demonstrated large tumors in the velum interpositum with intensities suggestive of epidermoid cysts. There was ventral displacement of the internal cerebral veins and dorsal displacement of the corpus callosum in keeping with a mass in the velum interpositum. Tumors of the third ventricle displace the internal cerebral veins dorsally. A transcallosal approach was used in both patients to effectively excise the tumors.

Callosal branches of the anterior cerebral artery: an anatomical report

Although the morphology of the corpus callosum is well defined, the arterial supply of this structure has not been comprehensively studied. To elucidate this further, 40 cerebral hemispheres from 30 adult cadaveric brains were obtained. The anterior cerebral arteries were cannulated and injected with red latex. The following were observed and documented: (1) the number, diameter, and course of the arteries supplying the corpus callosum; (2) the territories vascularized by these arteries; (3) any variations of the callosal arteries. Short callosal arteries were present in 58 hemispheres (96.6%) and supplied the superficial surface of the corpus callosum along its midline and were a primary arterial source to this structure. Long callosal arteries were found in 28 hemispheres (46.6%) and contributed to the pial plexus. The cingulocallosal arteries were present in all hemispheres and supplied the corpus callosum, cingulate gyrus, and also contributed to the pericallosal pial plexus. The recurrent cingulocallosal arteries were present in 17 hemispheres (28.3%) and also contributed to the pericallosal pial plexus. The median callosal artery, an anatomical variation, was present in 10 brains (33.3%). This vessel supplied the corpus callosum and the cingulate gyrus. The aim of the present study was to provide a detailed description of the arteries supplying the corpus callosum for those who encounter these vessels radiologically or surgically.

The velum interpositum revisited and redefined

INTRODUCTION

Descriptions of the velum interpositum (VI) are typically brief and lacking detail in most neuroanatomical and neurosurgical texts. As this structure may be involved clinically or encountered surgically, the present study seemed warranted.

MATERIALS AND METHODS

Twenty-adult (10 male and 10 female) formalin fixed and fresh cadaveric brains underwent a detailed dissection of the VI via an interhemispheric transcollosal approach. Observations were made of the attachment sites and continuation of the VI. Measurements were made of its length and width at its anterior, midportion, and posterior parts.

RESULTS

The VI extended laterally over the thalami to become continuous with the choroid plexus of the lateral ventricles. At a point along the thalami where the choroid plexus was found, the VI became "tacked" down and thus continuous with the choroid plexus subependymally. No specimen exhibited a separate choroid plexus of the third ventricle. In each, the choroid plexus of the lateral and third ventricles were the same tissue layer, all arising from the VI. This structure was adherent to but not fused to the deep surface of the fornix. The VI was also not fused to the pineal gland or habenula commissure but simply covered these structures. This membrane was confluent with the pia/arachnoid over the cerebellum and from the inferior surface of the parietal/occipital lobes and extended laterally into the choroid fissure.

CONCLUSIONS

To our knowledge, the extent of the VI as described herein has not been reported earlier. The supratentorial choroid plexus is simply a vascular extension of the VI. There is no separate choroid plexus of the third ventricle as often described. Clear planes exist between the VI and surrounding structures such as the pineal gland. Such data may be useful to neurosurgeons who operate in this region and to clinicians who interpret imaging in the area of the VI.

Meningiomas of pineal region in children

Meningiomas are uncommon tumors in children and either more rarely encountered in the pineal region. We report two cases of meningioma of the pineal region in children. One of these cases was a five years-old girl and the other a one year-old boy. No specific clinical presentation or tomographic examinations findings was identified before treatment, suggestive of a diagnosis of menigioma. The clinical and laboratory features were very similar to the most common tumors of the pineal region. Prior to the surgery, the histology of these tumors was not suspected. Both patients underwent direct surgery and complete removal was achieved by a suboccipital transtentorial approach. The tumors originated from velum interpositum in both cases. At the follow up, one case presented with recurrence six years later, and she underwent a reoperation with total resection without morbidity. Long-term follow up presented no other recurrences.

Intraventricular meningiomas

Intraventricular meningiomas are most often seen in the lateral ventricles of adults, more often on the left than on the right. A variety of surgical approaches can be selected depending on patient and tumor factors as well as on surgeon preference. Some of these approaches are complex and demand a thorough understanding of the ventricular and periventricular anatomy. When successful, surgery can be curative in most cases of total removal.