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Background and Objectives: The size and anatomic location of meningiomas have been shown to correlate with distinct clinical manifestations, histopathological subtypes, and surgical risk. However, meningioma anatomic origin sites can be obscured in large tumors and those crossing compartments. We therefore sought to apply unbiased lesion mapping to localize intracranial meningioma distributions and their association with biology and grade., Methods: MRI scans, World Health Organization (WHO) grade, and a molecularly Integrated Grade (IG) derived from cytogenetics were analyzed from adult patients with intracranial meningiomas. Semi-automated tumor segmentation was performed on T1-weighted contrast-enhanced MRI. We used the voxel-based lesion mapping technique to generate a meningioma atlas, mapping spatial frequency and correlating with tumor grades., Results: Of 881 patients with meningioma (median age: 57 years, 68.8% female), 589 were WHO grade 1 (66.8%), 265 WHO grade 2 (30.1%), and 27 WHO grade 3 (3.1%) with a median tumor volume of 14.6 cm3. After molecular reclassification, 585 were IG-1 (66.4%), 160 IG-2 (18.2%), and 136 IG-3 (15.4%). Benign tumors were concentrated in and around the midline anterior skull base while malignant meningiomas were enriched in the falcine/parasagittal region and the sphenoid wing, similar to the distribution when stratified by chromosome 1p loss. Meningiomas exhibited sharper spatial clustering when stratified by the molecular IG than by WHO grade. WHO grade 2 meningiomas divided equally across IG 1-3, with corresponding partition of spatial distribution in the midline anterior skull base (in WHO grade 2, IG-1) and falcine/parasagittal and sphenoid regions (WHO grade 2, IG-3). Meningioma volumes significantly varied across age, sex, and WHO/IG grades., Conclusion: We demonstrate the utility of voxel-based lesion mapping for intracranial tumors, characterizing distinct meningioma distribution patterns across histopathological and molecularly defined grades. Molecular grading associated with sharper tumor spatial clusters, supporting a phenotype-genotype association in meningiomas., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Background and Objectives: Although stereotactic radiation has frequently supplanted whole-brain radiation therapy (WBRT) in treating patients with multiple brain metastases, the role of surgery for these patients remains unresolved. No randomized trials have compared surgical resection with postoperative stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) to SRS/SRT alone. Previous studies addressing surgery for patients with multiple brain metastases are often limited by small sample sizes, a lack of appropriate comparison groups, or a focus on patients treated before recent advances in targeted therapy and immunotherapy. We compared outcomes in patients with multiple brain metastases treated with surgical resection and postoperative SRS/SRT to those treated with SRS/SRT alone., Methods: We studied 734 patients with multiple newly diagnosed brain metastases (surgery with SRS/SRT, n = 228; SRS/SRT alone, n = 506) from 2011 to 2022 in a retrospective, single-institution cohort. Patients who received upfront whole-brain radiotherapy were excluded. Cox proportional hazards models were constructed for overall survival and additional intracranial outcomes., Results: After adjustment for potential confounders, surgery with postoperative SRS/SRT was associated with decreased all-cause mortality compared with SRS/SRT alone (hazard ratio [HR]: 0.67, 95% CI [0.50-0.89], P = 5.56 × 10 -3 ). The association between surgical resection and overall survival was replicated in a subset of the cohort after cardinality matching (HR: 0.64, 95% CI [0.46-0.88], P = 6.68 × 10 -3 ). Patients with melanoma benefited significantly less from surgical resection compared with patients with other tumor types, most notably non-small-cell lung cancer. Compared with definitive SRS/SRT, cavity SRS/SRT was associated with a significantly reduced risk of both symptomatic radiation necrosis (HR: 0.22, 95% CI [0.08-0.59], P = 2.70 × 10 -3 ) and radiographic radiation necrosis (HR: 0.23, 95% CI [0.09-0.57], P = 1.43 × 10 -3 ) in multivariable models., Conclusion: In patients with multiple brain metastases, surgical resection before SRS/SRT is associated with reduced mortality and radiation necrosis. Prospective studies may further delineate patient populations that benefit from aggressive local, brain-directed treatment even with significant intracranial disease burden., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background and Objectives: Stereotactic radiotherapy (SRT) in multiple fractions (typically ≤5) can effectively treat a wide range of brain metastases, including those less suitable for single-fraction stereotactic radiosurgery (SRS). Prior prospective studies on surgical resection with stereotactic radiation have focused exclusively on SRS, and retrospective studies have shown equivocal results regarding whether surgery is associated with improved outcomes compared with SRT alone. We compared resection with postoperative cavity SRT or SRS to SRT alone in patients with 1 brain metastasis, while including patients receiving SRS alone as an additional reference group., Methods: We studied 716 patients in a retrospective, single-institution cohort diagnosed with single or solitary brain metastases from 2007 to 2020. Patients receiving whole-brain radiotherapy were excluded. Cox proportional hazards models were constructed for overall survival and additional intracranial outcomes., Results: After adjustment for potential confounders, surgery with cavity SRT/SRS was associated with decreased all-cause mortality (hazard ratio [HR]: 0.39, 95% CI [0.27-0.57], P = 1.52 × 10 -6 ) compared with SRT alone, along with lower risk of neurological death attributable to intracranial tumor progression (HR: 0.46, 95% CI [0.22-0.94], P = 3.32 × 10 -2 ) and radiation necrosis (HR: 0.15, 95% CI [0.06-0.36], P = 3.28 × 10 -5 ). Surgery with cavity SRS was also associated with decreased all-cause mortality (HR: 0.52, 95% CI [0.35-0.78], P = 1.46 × 10 -3 ), neurological death (HR: 0.30, 95% CI [0.10-0.88], P = 2.88 × 10 -2 ), and radiation necrosis (HR: 0.14, 95% CI [0.03-0.74], P = 2.07 × 10 -2 ) compared with SRS alone. Surgery was associated with lower risk of all-cause mortality and neurological death in cardinality-matched subsets of the cohort. Among surgical patients, gross total resection was associated with extended overall survival (HR: 0.62, 95% CI [0.40-0.98], P = 4.02 × 10 -2 ) along with lower risk of neurological death (HR: 0.31, 95% CI [0.17-0.57], P = 1.84 × 10 -4 ) and local failure (HR: 0.34, 95% CI [0.16-0.75], P = 7.08 × 10 -3 )., Conclusion: In patients with 1 brain metastasis, minimizing intracranial disease specifically before stereotactic radiation is associated with improved oncologic outcomes., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background: Venous thromboembolism (VTE), encompassing deep venous thrombosis (DVT) and pulmonary embolism (PE), causes postoperative morbidity and mortality in neurosurgical patients. The use of pharmacological prophylaxis for DVT prevention in the immediate postoperative period carries increased risk of intracranial hemorrhage, especially after skull base surgeries., Objective: To investigate the impact of routine Doppler ultrasound monitoring in prevention and tiered management of VTE after skull base surgery., Methods: We retrospectively analyzed a large cohort of consecutive adult patients who were prospectively and uniformly managed with routine monitoring by Doppler ultrasound for DVT after resection of a skull base tumor., Results: A total of 389 patients who underwent 459 surgeries for intracranial tumor resection were analyzed. Skull base meningioma was the most common pathology. Forty-four (9.59%) postoperative VTEs were detected: 9 (1.96%) with PE with or without DVT and 35 (7.63%) with DVT alone. Four cases of subsegmental PE were diagnosed without evidence of lower extremity DVT, possibly in the setting of peripherally inserted central catheters maintenance. One patient had a preoperative proximal DVT and underwent a prophylactic inferior vena cava filter but expired from PE after discharge. Prior history of VTE (risk ratio [RR] 5.13; 95% CI 2.76-7.18; P < .01), anesthesia duration (RR 1.14; 95% CI 1.03-1.27; P = .02), and blood transfusion (RR 1.95; 95% CI 1.01-3.37; P = .04) were associated with VTE development on multivariate analysis., Conclusion: Routine postoperative venous ultrasound monitoring detects asymptomatic DVT guiding management. This is an alternative strategy to prescribing pharmacological VTE prophylaxis immediately after lengthy surgeries for intracranial tumors. Peripherally inserted central catheters were associated with subsegmental PE., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Tumors that arise in and around the skull base comprise a wide range of common and rare entities. Recent studies have advanced our understanding of their pathogenesis, which in some cases, have significantly influenced clinical practice. The genotype of meningiomas is strongly associated with their phenotype, including histologic subtype and tumor location, and clinical outcome. A single molecular alteration, NAB2-STAT6 fusion, has redefined the category of solitary fibrous tumors to include the previous entity hemangiopericytomas. Schwannomas, both sporadic and familial, are characterized by near ubiquitous alterations in NF2 , with additional mutations in SMARCB1 or LZTR1 in schwannomatosis. In pituitary adenohypophyseal tumors, cell lineage transcription factors such as SF-1, T-PIT, and PIT-1 are now essential for classification, providing a more rigorous taxonomy for tumors that were previously considered null cell adenomas. The pituicyte lineage transcription factor TTF-1 defines neurohypophyseal tumors, which may represent a single nosological entity with a spectrum of morphologic manifestations (ie, granular cell tumor, pituicytoma, and spindle cell oncocytoma). Likewise, the notochord cell lineage transcription factor brachyury defines chordoma, discriminating them from chondrosarcomas. The identification of nonoverlapping genetic drivers of adamantinomatous craniopharyngiomas and papillary craniopharyngiomas indicates that these are distinct tumor entities and has led to successful targeted treatment of papillary craniopharyngiomas using BRAF and/or mitogen-activated protein kinase inhibitors. Similarly, dramatic therapeutic responses have been achieved in patients with Langerhans cell histiocytosis, both with BRAF -mutant and BRAF -wildtype tumors. Familiarity with the pathology of skull base tumors, their natural history, and molecular features is essential for optimizing patient care., (Copyright © Congress of Neurological Surgeons 2021. All rights reserved.)

Facial nerve schwannomas are rare and can arise from any segment along the course of the facial nerve.1 Their location and growth patterns present as distinct groups that warrant specific surgical management and approaches.2 The management challenge arises when the facial nerve maintains good function (House-Brackmann grade I-II).3 Hence, a prime goal of management is to maintain good facial animation. In large tumors, however, resection with facial nerve function preservation should be sought and is achievable.4,5  While tumors originating from the geniculate ganglion grow extradural on the floor of the middle fossa, they may extend via an isthmus through the internal auditory canal to the cerebellopontine angle forming a dumbbell-shaped tumor. Despite the large size, they may present with good facial nerve function. These tumors may be resected through an extended middle fossa approach with preservation of facial and vestibulocochlear nerve function.  The patient is a 62-yr-old man who presented with mixed sensorineural and conductive hearing loss and normal facial nerve function. Magnetic resonance imaging (MRI) revealed a large tumor involving the middle fossa, internal auditory meatus, and cerebellopontine angle.  The tumor was resected through an extended middle fossa approach with a zygomatic osteotomy and anterior petrosectomy.6 A small residual was left at the geniculate ganglion to preserve facial function. The patient did well with hearing preservation and intact facial nerve function. He consented to the procedure and publication of images.  Image at 1:30 © Ossama Al-Mefty, used with permission. Images at 2:03 reprinted from Kadri and Al-Mefty,6 with permission from JNSPG., (© Congress of Neurological Surgeons 2021.)

Insular gliomas are located amongst myriad critical neurovascular structures, including lenticulostriate vessels, long insular perforators, putamen, internal capsule, frontal and temporal opercula, and key fasciculi.1-6 Each of these critical structures engenders key function of the brain, which must be preserved. Although anatomic knowledge remains the cornerstone of insular glioma surgery, novel tools have been developed to aid the surgeon in identifying and preserving these essential structures. Modern surgery of the insular glioma calls for seamless integration of these techniques to maximize the safety and totality of insular glioma resection, which has been shown to improve length of survival and seizure control, while reducing risk of tumor transformation.7-10 Neuronavigation can be used to help plan the craniotomy to achieve adequate exposure and assist during tumor resection. Brain "shift" can be corrected by re-registration following intraoperative magnetic resonance imaging (MRI). Interval ultrasound imaging reflects real-time progressive tumor resection. Dynamic neurophysiologic monitoring using thresholding techniques guides the surgeon as he resects tumor at its depth and posterior pole-close to the internal capsule. Intraoperative magnetic resonance imaging depicts residual infiltrative tumor that may require additional resection. The patient is a 33-yr-old woman with progressive growth of a right insular tumor and has consented to surgery, photography, and video recording.  Figure at 1:57, © Ossama Al-Mefty, used with permission., (© Congress of Neurological Surgeons 2021.)

Background: Isolated trigeminal schwannomas occur in 0.07% to 0.3% of intracranial tumors and account for 0.8% to 8% of intracranial schwannomas and 1/3 of Meckel cave tumors. The presence of multisegmental schwannoma is rare, resulting in a limited understanding of its optimal management., Objective: To describe potential surgical options to manage this rare entity., Methods: A 2-institution retrospective review of all patients with pathologically confirmed trigeminal schwannoma managed with resection from January 2009 through January 2019 was conducted. A manual chart review was performed to verify patients' inclusion and collect data about age, sex, tumor size, tumor site, treatment modality, surgical approach, complications, and follow-up duration and status., Results: A total of 4 patients (age range 12-50 yr) who underwent a variety of cranial and orbitocranial approaches for tumor resection were identified. Patients achieved good outcomes with improvement of visual outcomes. One case of infection and 1 case of partial tumor recurrence requiring reresection were identified., Conclusion: Multisegmental trigeminal schwannoma is a rare and unique entity, often associated with trigeminal schwannomatosis. Interdisciplinary management has been shown to be the most effective method for improving patient outcomes with these complex and poorly understood diseases., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Falcine meningiomas have unique characteristics including their high rates of recurrence, association with high grade pathology, increased male prevalence, and potential for diffuse involvement of the falx., Objective: To address these issues in a substantial series of falcine meningiomas and report on the impact of extent of resection for this distinct meningioma entity., Methods: Retrospective analysis of characteristics and outcomes of 59 falcine meningioma patients who underwent surgery with the senior author. A "Grade Zero" category was used when an additional resection margin of 2 to 3 cm from the tumor insertion was achieved., Results: For de novo falcine meningiomas, gross total resection (GTR) was associated with significantly decreased recurrence incidence compared with subtotal resection (P ≤ .0001). For recurrent falcine meningiomas, median progression-free survival (PFS) was significantly improved for GTR cases (37 mo vs 12 mo; P = .017, hazard ratio (HR) .243 (.077-.774)). "Grade Zero" resection demonstrated excellent durability for both de novo and recurrent cases, and PFS was significantly improved with "Grade Zero" resection for recurrent cases (P = .003, HR 1.544 (1.156-2.062)). The PFS benefit of "Grade Zero" resection did not achieve statistical significance over Simpson grade 1 during the limited follow-up period (mean 2.8 yr) for these groups., Conclusion: The recurrence of falcine meningiomas is related to the diffuse presence of tumor between the leaflets of the falx. Increased extent of resection including, when possible, a clear margin of falx surrounding the tumor base was associated with the best long-term outcomes in our series, particularly for recurrent tumors., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Chronic subdural hematoma (cSDH) is a common neurosurgical condition, with symptoms ranging from headaches to coma. Operative evacuation is the treatment of choice. Subdural reaccumulation leading to reoperation is a vexing postoperative complication., Objective: To present a novel technique for intraoperative aspiration of pneumocephalus via a subdural drain following SDH evacuation as a method of reducing potential subdural space and promoting cerebral expansion, thereby decreasing SDH recurrence., Methods: In this retrospective study, 15 patients who underwent operative evacuation of cSDH between 2008 and 2015 were assessed. Six patients underwent a small craniotomy with intraoperative pneumocephalus aspiration. These patients were matched by age, gender, and anticoagulation status to 9 patients who underwent evacuation of SDH without pneumocephalus aspiration. Quantitative volumetric analysis was performed on the preoperative, postoperative, and 1-mo follow-up computed tomography scan to assess the subdural volume., Results: In the immediate postoperative period, there was no difference in the percentage of residual subdural fluid between the aspiration and control groups (0.291 vs 0.251; P = 1.00). There was a decrease in amount of pneumocephalus present when the aspiration technique was applied (0.182 vs 0.386; P = .041). At 1-mo follow-up, there was a decrease in the residual cSDH volume between the aspiration and the control groups (28.7 mL vs 60.8 mL; P = .011). The long-term evacuation rate was greater in the aspiration group (75.4% vs 51.6%; P = .015)., Conclusion: Intraoperative aspiration of cSDH cavity is a safe technique that may enhance cerebral expansion and reduce likelihood of cSDH recurrence., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Skull base chordomas in children are extremely rare. Their course, management, and outcome have not been defined., Objective: To describe the preeminent clinical and radiological features in a series of pediatric patients with skull base chordomas and analyze the outcome of a cohort who underwent uniform treatment. We emphasize predictors of overall survival and progression-free survival, which aligns with Collins' law for embryonal tumors., Methods: Thirty-one patients with a mean age of 10.7 yr (range 0.8-22) harboring skull base chordomas were evaluated. We retrospectively analyzed the outcomes and prognostic factors for 18 patients treated by the senior author, with uniform management of surgery with the aim of gross total resection and adjuvant proton-beam radiotherapy. Mean follow-up was 119.2 mo (range 8-263)., Results: Abducens nerve palsy was the most common presenting symptom. Imaging disclosed large tumors that often involve multiple anatomical compartments. Patients undergoing gross total resection had significantly increased progression-free survival (P = .02) and overall survival (P = .05) compared with those having subtotal resection. Those who lived through the period of risk for recurrence without disease progression had a higher probability of living entirely free of progression (P = .03; odds ratio = 16.0). Age, sex, and histopathological variant did not yield statistical significance in survival., Conclusion: Long-term overall and progression-free survival in children harboring skull base chordomas can be achieved with gross surgical resection and proton-beam radiotherapy, despite an advanced stage at presentation. Collins' law does apply to pediatric skull base chordomas, and children with this disease have a high hope for cure.

Question 1: What sequences should be obtained on magnetic resonance imaging (MRI) to evaluate vestibular schwannomas before and after surgery?, Target Population: Adults with vestibular schwannomas., Recommendations: Initial Preoperative Evaluation Level 3: Imaging used to detect vestibular schwannomas should use high-resolution T2-weighted and contrast-enhanced T1-weighted MRI. Level 3: Standard T1, T2, fluid attenuated inversion recovery, and diffusion weighted imaging MR sequences obtained in axial, coronal, and sagittal plane may be used for detection of vestibular schwannomas. Preoperative Surveillance Level 3: Preoperative surveillance for growth of a vestibular schwannoma should be followed with either contrast-enhanced 3-dimensional (3-D) T1 magnetization prepared rapid acquisition gradient echo (MPRAGE) or high-resolution T2 (including constructive interference in steady state [CISS] or fast imaging employing steady-state acquisition [FIESTA] sequences) MRI. Postoperative Evaluation Level 2: Postoperative evaluation should be performed with postcontrast 3-D T1 MPRAGE, with nodular enhancement considered suspicious for recurrence., Question 2: Is there a role for advanced imaging for facial nerve detection preoperatively (eg, CISS/FIESTA or diffusion tensor imaging)?, Target Population: Adults with proven or suspected vestibular schwannomas by imaging., Recommendation: Level 3: T2-weighted MRI may be used to augment visualization of the facial nerve course as part of preoperative evaluation., Question 3: What is the expected growth rate of vestibular schwannomas on MRI, and how often should they be imaged if a "watch and wait" philosophy is pursued?, Target Population: Adults with suspected vestibular schwannomas by imaging., Recommendation: Level 3: MRIs should be obtained annually for 5 yr, with interval lengthening thereafter with tumor stability., Question 4: Do cystic vestibular schwannomas behave differently than their solid counterparts?, Target Population: Adults with vestibular schwannomas with cystic components., Recommendation: Level 3: Adults with cystic vestibular schwannomas should be counseled that their tumors may more often be associated with rapid growth, lower rates of complete resection, and facial nerve outcomes that may be inferior in the immediate postoperative period but similar to noncystic schwannomas over time., Question 5: Should the extent of lateral internal auditory canal involvement be considered by treating physicians?, Target Population: Adult patients with vestibular schwannomas., Recommendation: Level 3: The degree of lateral internal auditory canal involvement by tumor adversely affects facial nerve and hearing outcomes and should be emphasized when interpreting imaging for preoperative planning., Question 6: How should patients with neurofibromatosis type 2 (NF2) and vestibular schwannoma be imaged and over what follow-up period?, Target Population: Adult patients with NF2 and vestibular schwannomas., Recommendation: Level 3: In general, vestibular schwannomas associated with NF2 should be imaged (similar to sporadic schwannomas) with the following caveats: 1. More frequent imaging may be adopted in NF2 patients because of a more variable growth rate for vestibular schwannomas, and annual imaging may ensue once the growth rate is established. 2. In NF2 patients with bilateral vestibular schwannomas, growth rate of a vestibular schwannoma may increase after resection of the contralateral tumor, and therefore, more frequent imaging may be indicated, based on the nonoperated tumor's historical rate of growth. 3. Careful consideration should be given to whether contrast is necessary in follow-up studies or if high-resolution T2 (including CISS or FIESTA-type sequences) MRI may adequately characterize changes in lesion size instead., Question 7: How long should vestibular schwannomas be imaged after surgery, including after gross-total, near-total, and subtotal resection?, Target Population: Adult patients with vestibular schwannomas followed after surgery., Recommendation: Level 3: For patients receiving gross total resection, a postoperative MRI may be considered to document the surgical impression and may occur as late as 1 yr after surgery. For patients not receiving gross total resection, more frequent surveillance scans are suggested; annual MRI scans may be reasonable for 5 yr. Imaging follow-up should be adjusted accordingly for continued surveillance if any change in nodular enhancement is demonstrated.  The full guideline can be found at https://www.cns.org/guidelines/guidelines-management-patients-vestibular-schwannoma/chapter&#95;5., (Copyright © 2017 by the Congress of Neurological Surgeons)

Background: Functional gonadotroph adenomas (FGAs) are rare tumors of the pituitary gland that secrete biologically active gonadotropins., Objective: To advance clinical understanding of FGAs., Methods: We performed a retrospective review of adult patients who underwent resection of a pituitary lesion between August 1997 and October 2014 and remain under care at our center. We identified patients who had pathologic and biochemical confirmation of FGAs, as defined by a lack of serum follicle-stimulating hormone/luteinizing hormone suppression in the setting of elevated gonadal steroids, associated clinical symptoms, or both., Results: FGAs were documented in 7 patients (5 men, 2 women) over a 17-year period. Clinical findings at presentation included visual field deficits in 5 patients, headache in 3, sexual dysfunction in 3, and ovarian cysts in both women. Each patient underwent lesion resection (6 via the endonasal transsphenoidal approach and 1 via a craniotomy with transsphenoidal reoperation). Analysis of tumor samples revealed immunopositivity for follicle-stimulating hormone/luteinizing hormone in 5 patients and FSH only in 2 patients. Postoperative follow-up (median, 10 months; range, 4-213 months) indicated remission in 6 of 7 patients., Conclusion: An FGA can pose both a diagnostic and a therapeutic challenge. The tumor is often diagnosed as a nonfunctioning macroadenoma after presenting with nonspecific symptoms and is the cause of significant morbidity. An FGA should be considered in the differential diagnosis of patients harboring pituitary adenomas with reproductive dysfunction. Transsphenoidal resection is the initial treatment of choice and can reduce endocrine dysfunction, resolve headaches, improve visual impairment, and provide tissue for detailed analysis., Abbreviations: FGA, functional gonadotroph adenomaFSH, follicle-stimulating hormoneLH, luteinizing hormoneTSH, thyroid-stimulating hormone.

Objective and Importance: We report a rare complication after resection of a recurrent intracranial nongerminomatous germ cell tumor in an adult. The growing teratoma syndrome, as originally described with pediatric germ cell neoplasms, represents tumor recurrence, often cystic, that sometimes is observed after partial response to multimodality therapy and despite decreasing tumor serum markers. The enlarging tumor consists of elements of a mature teratoma that presumably are refractory to chemotherapy or radiation. To our knowledge, this is only the third case of the growing teratoma syndrome in an adult patient with nongerminomatous germ cell tumor., Clinical Presentation: A 26-year-old man had signs of recurrent obstructive hydrocephalus 6 months after multimodality treatment of a diencephalic yolk sac tumor and endoscopic third ventriculostomy. Imaging studies revealed large multilocular cystic masses originating from the tumor bed and partially obstructing the ventriculostomy., Intervention: Near total tumor resection and fenestration was performed. Histopathological analysis demonstrated a mature teratoma., Conclusion: Surgical resection, if feasible, is the treatment of choice for the growing teratoma syndrome to establish the correct diagnosis and prevent complications.