Intraoperative Measurement of Arterial Blood Flow in Aneurysm Surgery.

Intraoperative flowmetry (IF) has been recently introduced during cerebral aneurysm surgery in order to obtain a safer surgical exclusion of the aneurysm. This study evaluates the usefulness of IF during surgery for cerebral aneurysms and compares the results obtained in the joined surgical series of Verona and Padua to the more recent results obtained at the neurosurgical department of Verona.In the first surgical series, between 2001 and 2010, a total of 312 patients were submitted to IF during surgery for cerebral aneurysm at the neurosurgical departments of Verona and Padua: 162 patients presented with subarachnoid hemorrhage (SAH) whereas 150 patients harbored unruptured aneurysms. In the second series, between 2011 and 2016, 112 patients were submitted to IF during surgery for cerebral aneurysm at the neurosurgical department of Verona; 24 patients were admitted for SAH, whereas 88 patients were operated on for unruptured aneurysms.Comparison of the baseline values in the two surgical series and the baseline values between unruptured and ruptured aneurysms showed no statistical differences between the two clinical series. Analysis of flowmetry measurements showed three types of loco-regional flow derangements: hyperemia after temporary arterial occlusion, redistribution of flow in efferent vessels after clipping, and low flow in patients with SAH-related vasospasm.IF provides real-time data about flow derangements caused by surgical clipping of cerebral aneurysm, thus enabling the surgeon to obtain a safer exclusion; furthermore, it permits the evaluation of other effects of clipping on the loco-regional blood flow. It is suggested that-in contribution with intraoperative neurophysiological monitoring-IF may now constitute the most reliable tool for increasing safety in aneurysm surgery.

Outcome of patients affected by newly diagnosed glioblastoma undergoing surgery assisted by 5-aminolevulinic acid guided resection followed by BCNU wafers implantation: a 3-year follow-up.

The purpose of the study was to evaluate the clinical outcome of the association of BCNU wafers implantation and 5-aminolevulinic acid (5-ALA) fluorescence in the treatment of patients with newly diagnosed glioblastoma (ndGBM). Clinical and surgical data from patients who underwent 5-ALA surgery followed by BCNU wafers implantation were retrospectively evaluated (20 patients, Group I) and compared with data of patients undergoing surgery with BCNU wafers alone (42 patients, Group II) and 5-ALA alone (59 patients, Group III). Patients undergoing 5-ALA assisted resection followed by BCNU wafers implantation (Group I) resulted long survivors (>3 years) in 15 % of cases and showed a median PFS and MS of 11 and 22 months, respectively. Patients treated with BCNU wafers presented a significantly higher survival when tumor was removed with the assistance of 5-ALA (22 months with vs 18 months without 5-ALA, p < 0.0001); these data could be partially explained by the significantly higher CRET achieved in patients operated with 5-ALA assistance (80 % with vs 47 %% without 5-ALA). Moreover, patients of Group I showed a significant increased survival compared with Group III (5-ALA without BCNU) (22 months with vs 21 months without BCNU wafers, p = 0.0025) even with a comparable CRET (80 % vs 76 %, respectively). The occurrence of adverse events related to wafers did not significantly increase with 5-ALA (20 % with and 19 % without 5-ALA) and did not impact in survival outcome. In conclusion, our experience shows that on selected ndGBM patients 5-ALA technology and BCNU wafers implantation show a synergic action on patients' outcome without increasing adverse events occurrence.

Beyond breast specific-Graded Prognostic Assessment in patients with brain metastases from breast cancer: treatment impact on outcome.

Brain metastases are a serious relatively common complication of breast cancer. We evaluated prognostic factors for survival after diagnosis of brain metastases from breast cancer in a contemporary cohort of patients. Patients diagnosed with breast cancer brain metastases at our institution between 1999 and March 2016 were evaluated. Overall survival was defined as time from brain metastasis diagnosis to death or last follow-up. Patients were classified according to the Breast cancer-specific Graded Prognostic Assessment (BS-GPA), based on age, Karnofsky performance score and breast cancer phenotype. 181 patients were identified. Tumor phenotype distribution was as follows: triple negative (TN, 18.8%), hormone receptor (HR)-HER2+ (16.6%), HR+HER2+ (23.2%) and HR+HER2- (30.9%), not available (10.5%). Median overall survival from brain metastasis diagnosis was 7.7 mos (95% CI 5.4-10.0 mos). Although TN patients experienced the worse outcome, no significant difference was observed across tumor phenotypes (median 5.1, 7.7, 11.0 and 8.6 months in TN, HR-HER2+, HR+HER2+, HR+HER2-, p = 0.081). The BS-GPA index was significantly associated with overall survival (median 18.8, 8.8, 6.2 and 3.6 months, respectively, for BS-GPA categories 3.5-4, 2.5-3, 1.5-2 and 0-1, p = 0.014). Increased number of local treatments for brain metastasis (radiotherapy or neurosurgery) or the administration of systemic therapy after brain metastasis diagnosis were also significant predictors of better overall survival (p < 0.001) and, when evaluated in multivariate analysis with BS-GPA, both added independent prognostication beyond BS-GPA. Patient-related features, tumor phenotype and multimodal treatments all independently contribute to modulate prognosis of patients diagnosed with breast cancer brain metastases.

Utility of indocyanine green videoangiography in subcortical arteriovenous malformation resection.

Subcortical arteriovenous malformations (AVMs) are surgically challenging. Localization is crucial for eloquent areas, and complete resection evaluation is uncertain. Indocyanine green videoangiography (ICG-VA) can assist this surgery. An illustrative video of a subcortical frontoparietal bleeding AVM resection assisted by ICG-VA is presented. A bleeding arterial feeder aneurysm was embolized in the acute phase to protect against rebleeding. ICG-VA helped to detect the AVM's superficial arterialized draining vein, distinguishing it from normal cortical veins. This enabled a customized sulcus approach. ICG-VA showed normalized flow through the previously arterialized vein, confirming the AVM's complete resection. This applies when there is a single drainage remaining. The video can be found here: https://youtu.be/L7yJEE66kV0 .

Multimodal Flow-Assisted Resection of Brain AVMs.

OBJECT: The authors report their personal experience with brain arterio-venous malformations (bAVMs) surgery with a multimodal flow-assisted approach. METHODS: Data from patients who consecutively underwent bAVM resection with the assistance of indocyanine green video-angiography (ICG-VA), micro-flow probe flowmetry, and temporary arterial clipping test under intra-operative monitoring, were retrospectively analyzed. RESULTS: Twenty seven patients were enrolled in the study. Re-operation for residual nidus was needed in one case (3 %). Average mRS change 1 month after surgery was +0.02. In our experience, the multimodal flow-assisted approach enabled surgeons to shift from one technique to another, according to the stage of resection, AVM location, or specific issues to be addressed. Before resection, the value of ICG-VA and flowmetry in showing AVM angio-architecture and guiding surgical strategy was related to AVM features. The temporary arterial clipping-test presented a 100 % sensitivity to differentiate between an AVM feeder and a transit artery to the sensi-motor area. At the final stage of resection, flowmetry was more effective than ICG-VA in detecting residual nidus missed at dissection. CONCLUSIONS: Multimodal flow-assisted approach in AVM surgery proved a feasible, safe, and reliable methodology to achieve AVM resection with high radicality and low morbidity rate.

ICG-VA application in subtemporal transtentorial treatment of a Cognard V dural arteriovenous fistula.

Intracranial dural arteriovenous fistulas (dAVF) with cervical perimedullary drainage, Cognard V, are a surgically challenging rare entity. In this video we show the disconnection of a right tentorial Cognard V dAVF, done through a subtemporal transtentorial approach with the application of indocyanine green video angiography. A 47-year-old man presented with severe tetraparesis. Only partial embolization was possible. An osteoplastic frontotemporal craniotomy was performed to obtain a wide view along with CSF release to safely mobilize the temporal lobe. Neuronavigation was used to detect the fistula and indocyanine to detect the tentorial afferent arteries and to confirm final disconnection. The video can be found here: https://youtu.be/Yr8tAiiHNXU .

Facial asymmetry quantitative evaluation in oculoauriculovertebral spectrum.

OBJECTIVES: Facial asymmetries in oculoauriculovertebral spectrum (OAVS) patients might require surgical corrections that are mostly based on qualitative approach and surgeon's experience. The present study aimed to develop a quantitative 3D CT imaging-based procedure suitable for maxillo-facial surgery planning in OAVS patients. MATERIALS AND METHODS: Thirteen OAVS patients (mean age 3.5 ± 4.0 years; range 0.2-14.2, 6 females) and 13 controls (mean age 7.1 ± 5.3 years; range 0.6-15.7, 5 females) who underwent head CT examination were retrospectively enrolled. Eight bilateral anatomical facial landmarks were defined on 3D CT images (porion, orbitale, most anterior point of frontozygomatic suture, most superior point of temporozygomatic suture, most posterior-lateral point of the maxilla, gonion, condylion, mental foramen) and distance from orthogonal planes (in millimeters) was used to evaluate the asymmetry on each axis and to calculate a global asymmetry index of each anatomical landmark. Mean asymmetry values and relative confidence intervals were obtained from the control group. RESULTS: OAVS patients showed 2.5 ± 1.8 landmarks above the confidence interval while considering the global asymmetry values; 12 patients (92%) showed at least one pathologically asymmetric landmark. Considering each axis, the mean number of pathologically asymmetric landmarks increased to 5.5 ± 2.6 (p = 0.002) and all patients presented at least one significant landmark asymmetry. CONCLUSIONS: Modern CT-based 3D reconstructions allow accurate assessment of facial bone asymmetries in patients affected by OAVS. The evaluation as a global score and in different orthogonal axes provides precise quantitative data suitable for maxillo-facial surgical planning. CLINICAL RELEVANCE: CT-based 3D reconstruction might allow a quantitative approach for planning and following-up maxillo-facial surgery in OAVS patients.

Tissue Engineering Strategies as Tools for Personalized Meningioma Treatment.

Pharmacogenomics, the science of how genetic makeup influences an individual's reaction to drugs, is an innovative tool for providing critical insights into how a patient will respond to a particular treatment. In the present work, we constructed cancer-like tissues to be used as tools for determining the most effective drug for an individual patient. Using tissue engineering strategies, we generated two different solid tumor-like tissues in vitro, a neuronal tumor (meningioma) and a nonmelanoma skin cancer. Samples were tested by both histological and genetic approaches (using a comparative genomic hybridization array, and the relative World Health Organization classification of the samples was compared with the results obtained by the molecular analyses. Our data confirmed the ability of the cells to maintain their phenotype in three-dimensional scaffolds as well as the strong relationship between chromosomal alterations and histological malignancy grades. We then validated the in vitro construction of tumor-like tissues as a potential tool for developing personalized drug treatments.

The suboccipital midline approach to foramen magnum meningiomas.

BACKGROUND: Anterior and anterolateral meningiomas of the foramen magnum (FM) can be resected either through extensive skull base approaches or through the classical suboccipital midline approach with limited bone removal. METHOD: This paper describes the suboccipital midline approach focusing on some peculiar technical features that serve to achieve the necessary space for safe resection of these challenging tumors. CONCLUSIONS: In our experience, by adopting appropriate strategies to gain space (some of them natural, others acquired) the suboccipital midline approach can achieve the safe resection of anterior and anterolateral FM meningiomas in the majority of cases.

Intraoperative functional mapping of calculation in parietal surgery. New insights and clinical implications.

BACKGROUND: Parietal areas play a crucial role in calculation processing. The purpose of this study is to report our experience in the assessment of calculation processing during awake surgery in parietal areas, focusing on clinical implications and new insights provided by this approach. METHODS: We retrospectively reviewed clinical and surgical data of 13 patients who underwent parietal surgery with calculation mapping. Cortical and sub-cortical areas (in 13 and five patients, respectively) involved in single-digit multiplications and additions were identified using bipolar electro-stimulation. RESULTS: Cortical stimulation data showed that the inferior parietal lobule and the intraparietal sulcus were specifically related to calculation in all cases, regardless of the side (100% of cases, in both sides). Conversely, the superior parietal lobule was inconstantly involved in calculation processing (40% of cases in the left and 75% in the right side), whereas the somatosensory area was never involved. Sub-cortical stimulation was able to detect functional areas for calculation in all patients: in 90% of cases the sub-cortical sites positive for calculation were in close anatomical connection with the cortical sites mapping for the same function. The intraoperative preservation (-or damaging-) of functional sites correlated with the absence (- or occurrence-) of post-operative calculation processing impairment. CONCLUSIONS: Our findings support the specificity of the reported technique in the intraoperative identification of sites functional for calculation. Our data show the bilateral involvement of parietal cortex, especially of the inferior lobule, in calculation processing. Furthermore, our study suggests the existence of a sub-cortical pathway specific for calculation, whose better understanding might be crucial for the clinical outcome of patients.

Phenotypic and functional characterization of Glioblastoma cancer stem cells identified through 5-aminolevulinic acid-assisted surgery [corrected].

5-aminolevulinic acid (5-ALA) introduction in the surgical management of Glioblastoma (GBM) enables the intra-operatively identification of cancer cells in the mass by means of fluorescence. Here, we analyzed the phenotype of GBM cells isolated from distinct tumour areas determined by 5-ALA (tumour core, 5-ALA intense and vague layers) and the potency of 5-ALA labelling in identifying GBM cells and cancer stem cells (CSCs) in the mass. 5-ALA identified distinct layers in the mass, with less differentiated cells residing in the core of the tumour. 5-ALA was able to stain up to 68.5% of CD133(+) cells in the 5-ALA intense layer and, although 5-ALA(+) cells retrieved from different tumour areas contained a similar proportion of CD133(+) cells (range 27.5-35.6%), those from the vague layer displayed the lowest ability to self-renew. In conclusion, our data demonstrate that a substantial amount of GBM cells and CSCs in the mass are able to avoid 5-ALA labelling and support the presence of heterogenic CSC populations in the GBM mass.

Intra-operative 5-aminolevulinic acid (ALA)-induced fluorescence of medulloblastoma: phenotypic variability and CD133(+) expression according to different fluorescence patterns.

5-Aminolevulinic acid (5-ALA) fluorescence has been proved advantageous in glioma surgery. Conflicting results have been reported by few studies published in literature about intra-operative 5-ALA-induced fluorescence of medulloblastoma (MDB). The aim of this study is to verify if these conflicting results could be explained by intra-tumoral histological and phenotypic differences. In the present case of a 45-year-old patient affected by a cerebellar MDB, histological analysis of cell phenotype and 5-ALA and CD133 correlation were performed in multiple samples according to different fluorescence patterns. Intra-operatively, the tumor appeared unevenly fluorescent under blue-violet light. Histologically, 5-ALA-intense biopsies from inner areas were characterized by a significant amount of cancer cells, whereas 5-ALA faint regions from peripheral areas displayed normal cerebellar features, with MDB cells infiltrating healthy tissues. Presenting our findings, we show the correlation between different 5-ALA fluorescence patterns of medulloblastoma with specific histological and phenotypical features. Thus, we hypothesize that a distinct relationship between CD133 expression and fluorescence accumulation presented in our study could partially explain the divergent results published in literature.

Application of indocyanine green video angiography in parasagittal meningioma surgery.

OBJECT: There are no doubts about the role that indocyanine green video angiography (ICGVA) can play in current vascular neurosurgery. Conversely, in brain tumor surgery, and particularly in meningioma surgery, this role is still unclear. Vein management is pivotal for approaching parasagittal meningiomas, because venous preservation is strictly connected to both extent of resection and clinical outcome. The authors present the technical traits and the postoperative outcome of the application of ICGVA in patients undergoing parasagittal meningioma surgery. METHODS: The authors retrospectively collected demographic, radiological, intraoperative, and follow-up data in 43 patients with parasagittal meningiomas who underwent surgery with the assistance of ICGVA at Padua Neurosurgical Department between October 2010 and July 2013. Intraoperative ICGVA findings at different stages (before dural opening, after dural opening, during resection, after resection) were reviewed. Additional data on functional monitoring, temporary venous clipping, and flow measurements were also recorded. The overall postoperative outcome was evaluated by assessing both the extent of resection and the clinical outcome data. RESULTS: The ICGVA studies were performed 125 times in 43 patients, providing helpful data for vein management and tumor resection in all stages of surgery. In 16% of meningiomas completely occluding the superior sagittal sinus, the ICGVA data differed from radiological findings and changed the surgical approach. In 20% of cases the intraoperative ICGVA findings directly guided the surgical strategy: venous sacrifice was necessary in 7 cases, without postoperative consequences; temporary clipping with neurophysiological monitoring proved to be predictive of safe venous sacrifice. In 7% of cases the ICGVA data needed to be supplemented with flow measurements. Simpson Grade I-II and Grade III resections were achieved in 86% and 14% of cases, respectively, with a 4.6% rate of overall morbidity. CONCLUSIONS: This study shows that ICGVA can assist the different stages of parasagittal meningiomas surgery, guiding the vein management and tumor resection strategies with a favorable final clinical outcome. However, in the authors' experience the use of other complementary tools was mandatory in selected cases to preserve functional areas. Further studies are needed to confirm that the application of ICGVA in parasagittal meningioma surgery may improve the morbidity rate, as reported in this study.

Transdural indocyanine green video-angiography of vascular malformations.

BACKGROUND: The role of indocyanine green video-angiography (ICG-VA) in the surgical resection of vascular malformations has been largely described; conversely, the utility of ICG-VA before dural opening (transdural ICG-VA) in this situation remains unclear. The aim of this study is to present the application of transdural ICG-VA in a consecutive series of patients in order to explore the potential provided by a transdural visualisation of vascular malformations. METHOD: We retrospectively analysed the application of intra-operative ICG-VA before dural opening in 15 consecutive patients who underwent surgical resection of vascular malformations. The cases included 12 cerebral arterio-venous malformations (AVMs), 2 cerebral dural arterio-venous fistulas (dAVFs) and 1 spinal arterio-venous fistula (AVF). RESULTS: ICG-VA before dural opening allowed the visualisation of the site and extension of the malformation in 13 out of 15 cases, whilst arterial feeders and venous drainages were identified in 9 out of 15 cases. In two patients with dAVF, the point of fistula could be transdurally identified through ICG-VA. In 14% of cases, the size of bone flap designed on neuronavigation data was then modified according to transdural ICG-VA findings. CONCLUSIONS: Transdural ICG-VA proved an efficient tool that allows optimising the exposure of the malformation, performing a safe dural opening and identifying dural vascular connections of the lesion.

The neurosurgical telecounseling network in the Veneto Region: 4 years of experience of HEALTH OPTIMUM.

BACKGROUND: Neurosurgery is a highly specialized service that, because of high costs, is often centralized. Since 2005, a neurosurgical telecounseling service was defined and then deployed in the Veneto Region. It was aimed at creating the same range of services for head trauma by using standardized protocols at regional levels and at rationalizing the use of human and technological resources by providing a network of services that manages patients at the local level. The main objective of the study was to evaluate the use of this service. MATERIALS AND METHODS: Interoperability and flexibility were granted by creating a technological framework based on international standards. Physicians of local hospitals electronically transmit patients' clinical data and images to neurosurgeons located at a central hospital. These physicians respond to the requesting physicians by providing all the necessary recommendations. RESULTS: The outcomes were collected over a period of 41 months. The service is now available in 34 hospitals. Every year 3,181 telecounselings are conducted for patients with an average age of 65.5 years (55% male, 45% female) whose health status is mainly not serious. Within 30 min from the request of telecounseling, 49% of responses are sent. In 84% of cases the patient was not moved. The overall appreciation of clinicians is positive (4.3/5). Intervention time was reduced, and resources were optimized. CONCLUSIONS: The service brought remarkable benefits at the organizational level. The reorganization of the processes and patient management leads to rationalization of both human and technological resources.

Indocyanine green videoangiography (ICGV)-guided surgery of parasagittal meningiomas occluding the superior sagittal sinus (SSS).

BACKGROUND: Maximal safe resection is the goal of correct surgical treatment of parasagittal meningiomas, and it is intimately related to the venous anatomy both near and directly involved by the tumor. Indocyanine green videoangiography (ICGV) has already been advocated as an intra-operative resourceful technique in brain tumor surgery for the identification of vessels. The aim of this study was to investigate the role of ICGV in surgery of parasagittal meningiomas occluding the superior sagittal sinus (SSS). METHOD: In this study, we prospectively analyzed clinical, radiological and intra-operative findings of patients affected by parasagittal meningioma occluding the SSS, who underwent ICGV assisted-surgery. Radiological diagnosis of complete SSS occlusion was pre-operatively established in all cases. ICGV was performed before dural opening, before and during tumor resection, at the end of the procedure. RESULTS: Five patients were included in our study. In all cases, ICGV guided dural opening, tumor resection, and venous management. The venous collateral pathway was easily identified and preserved in all cases. Radical resection was achieved in four cases. Surgery was uneventful in all cases. CONCLUSIONS: Despite the small number of patients, our study shows that ICG videoangiography could play a crucial role in guiding surgery of parasagittal meningioma occluding the SSS. Further studies are needed to define the role of this technique on functional and oncological outcome of these patients.

5-aminolevulinic acid (5-ALA) fluorescence guided surgery of high-grade gliomas in eloquent areas assisted by functional mapping. Our experience and review of the literature.

BACKGROUND: Only few data are available on the specific topic of 5-aminolevulinic acid (5-ALA) guided surgery of high-grade gliomas (HGG) located in eloquent areas. Studies focusing specifically on the post-operative clinical outcome of such patients are yet not available, and it has not been so far explored whether such approach could be more suitable for some particular subgroups of patients. METHODS: Patients affected by HGG in eloquent areas who underwent surgery assisted by 5-ALA fluorescence and intra-operative monitoring were prospectively recruited in our Department between June 2011 and August 2012. Resection rate was reported as complete resection of enhancing tumor (CRET), gross total resection (GTR) >98 % and GTR > 90 %. Clinical outcome was evaluated at 7, 30, and 90 days after surgery. RESULTS: Thirty-one patients were enrolled. Resection was complete (CRET) in 74 % of patients. Tumor removal was stopped to avoid neurological impairment in 26 % of cases. GTR > 98 % and GTR > 90 % was achieved in 93 % and 100 % of cases, respectively. First surgery and awake surgery had a CRET rate of 80 % and 83 %, respectively. Even though at the first-week assessment 64 % of patients presented neurological impairment, there was a 3 % rate of severe morbidity at the 90th day assessment. Newly diagnosed patients had a significantly lower morbidity (0 %) and post-operative higher median KPS. Both pre-operative neurological condition and improvement after corticosteroids resulted significantly predictive of post-operative functional outcome. CONCLUSIONS: 5-ALA surgery assisted by functional mapping makes high HGG resection in eloquent areas feasible , through a reasonable rate of late morbidity. This emerges even more remarkably for selected patients.

Serum YKL-40 following resection for cerebral glioblastoma.

The lack of serum biomarkers for assessing the prognosis of patients with cerebral glioblastoma multiforme (GBM) prompted the present study in order to evaluate the significance of serum YKL-40 values in patients operated on for glioblastoma. An homogeneous population of 60 patients who underwent surgical removal of GBM underwent a standard treatment (surgery, radiotherapy, chemotherapy in the same schedule) and standard radiological monitoring (same MRI sequences at pre-defined stages). Serum YKL-40 levels (Quidel Corporation, San Diego, CA) were evaluated after dividing patients into two groups on the basis of the extent of resection (total or sub-total) according to the MRI results obtained within 48 h following surgery. YKL-40 serum values, significantly higher in GBM patients than in healthy subjects, were also higher among patients who had undergone subtotal resection than in patients who underwent extensive resection. The effect of YKL-40 on overall survival was analyzed by comparing the change in marker concentration occurring in the first postoperative week with the baseline value. A significant (P = 0.04) hazards ratio of 1.97 was found at multivariate analysis. A significant association with shorter outcome (median survival time, 76 days) was found in patients whose postoperative YKL-40 concentration increases higher than, or equal to, 100%; a 50% increase can still be considered a negative prognostic index. The evaluation of the biochemical marker YKL-40 might provide earlier and additional information to that obtained using traditional factors and be a further aid in establishing the prognosis of GBM patients who have undergone surgery.

Multifocal presentation of medulloblastoma in adulthood.

Medulloblastoma in adulthood is uncommon but not rare; annual incidence is 2-20/1,000,000. Some peculiarities characterize medulloblastoma in adult patients compared with the child type: lateral cerebellar location, heterogeneous signal intensity on magnetic resonance imaging, desmoplastic histological variant, and more favourable prognosis. Preoperative diagnosis is crucial for correct management of these patients. However, because of the low incidence of medulloblastoma in the adult population, preoperative diagnosis remains challenging and prognostic factors and best treatment options are still controversial. In this setting, some unusual findings, for example multifocal presentation and extra-axial location, can confound diagnosis and make treatment difficult. We present a short case-illustrated review on these remarkable issues.

MGMT expression and promoter methylation status may depend on the site of surgical sample collection within glioblastoma: a possible pitfall in stratification of patients?

We recently described a three-layer concentric model of a glioblastoma (GBM) related to a specific distribution of molecular and phenotypic characteristics driven by the intratumoral hypoxic gradient in which the cancer stem cells niche is located in the hypoxic necrotic core of the tumour. The purpose of this study was to investigate the relationship between O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status and MGMT expression in GBM samples collected according to the three-layer concentric model. Multiple tissue samples were obtained, by means of image-guided surgery, from the three concentric layers of newly diagnosed GBM. Two samples from each layer were collected from 12 patients (total 72 samples). Immunohistochemical analysis was performed on formalin-fixed paraffin-embedded tissue samples. The methylation status of the MGMT promoter was determined by methylation-specific polymerase-chain-reaction analysis. In all tumours, MGMT protein expression decreased progressively from the inner to the outer layer, and methylation of the MGMT promoter was unrelated to tumour layer. In particular, the MGMT promoter was unmethylated in all layers in 41.7% of tumours, methylated in all layers in 25%, and variably methylated in the three layers in 33.3%. We recorded concordance between MGMT expression and MGMT promoter methylation status within the GBM in only 58.8% of the samples collected. Our data suggest that both MGMT expression and promoter methylation data may be variable throughout GBM and that they may, consequently, depend on the site of surgical sample collection, even in the same patient. However, whereas MGMT expression is pre-operatively predictable when sampling is performed according to the three-layer concentric model, MGMT promoter methylation is not. These results must be considered when sample collection is performed for assessment of MGMT data.