[Value of perfusion MRI in the study of pilocytic astrocytoma and hemangioblastoma: preliminary findings]

Arterial Spin-Labeling Perfusion Lightbulb Sign: An Imaging Biomarker of Pediatric Posterior Fossa Hemangioblastoma

BACKGROUND AND PURPOSE

Hemangioblastoma is a rare vascular tumor that occurs within the central nervous system in children. Differentiating hemangioblastoma from other posterior fossa tumors can be challenging on imaging, and preoperative diagnosis can change the neurosurgical approach. We hypothesize that a "lightbulb sign" on the arterial spin-labeling (ASL) sequence (diffuse homogeneous intense hyperperfusion within the solid component of the tumor) will provide additional imaging finding to differentiate hemangioblastoma from other posterior fossa tumors.

MATERIALS AND METHODS

In this retrospective comparative observational study, we only included pathology-proved cases of hemangioblastoma, while the control group consisted of other randomly selected pathology-proved posterior fossa tumors from January 2022 to January 2024. Two blinded neuroradiologists analyzed all applicable MRI sequences, including ASL sequence if available. ASL was analyzed for the lightbulb sign. Disagreements between the radiologists were resolved by a third pediatric neuroradiologist. χ2 and Fisher exact test were used to analyze the data.

RESULTS

Ninety-five patients were enrolled in the study; 57 (60%) were boys. The median age at diagnosis was 8 years old (interquartile range: 3-14). Of the enrolled patients, 8 had hemangioblastoma, and 87 had other posterior fossa tumors, including medulloblastoma (n = 31), pilocytic astrocytoma (n = 23), posterior fossa ependymoma type A (n = 16), and other tumors (n = 17). The comparison of hemangioblastoma versus nonhemangioblastoma showed that peripheral edema (P = .02) and T2-flow void (P = .02) favor hemangioblastoma, whereas reduced diffusion (low ADC) (P = .002) and ventricular system extension (P = .001) favor nonhemangioblastoma tumors. Forty-two cases also had ASL perfusion sequences. While high perfusion favors hemangioblastoma (P = .03), the lightbulb sign shows a complete distinction because all the ASL series of hemangioblastoma cases (n = 4) showed the lightbulb sign, whereas none of the nonhemangioblastoma cases (n = 38) showed the sign (P < .001).

CONCLUSIONS

Lightbulb-like intense and homogeneous hyperperfusion patterns on ASL are helpful in diagnosing posterior fossa hemangioblastoma in children.

Evaluation of the Value of Perfusion-Weighted Magnetic Resonance Imaging in the Differential Diagnosis of Sellar and Parasellar Tumors

The purpose of this study was to assess the value of perfusion-weighted imaging (PWI) in the differential diagnosis of sellar and parasellar tumors, as an additional sequence in the magnetic resonance imaging (MRI) protocol. Analysis was based on a substantial group of subjects and included 124 brain and pituitary MRI examinations with a dynamic susceptibility contrast (DSC) PWI sequence. The following perfusion parameters were determined for the tumors: relative cerebral blood volume (rCBV), relative peak height (rPH) and relative percentage of signal intensity recovery (rPSR). To ensure greater repeatability, each of the aforementioned parameters was calculated as: arithmetic mean of the values of the whole tumor, arithmetic mean of the maximum values on each axial slice within the tumor and maximum values derived from the whole tumor. In our study, we established that meningiomas compared to both non-functional and hormone-secreting pituitary adenomas (pituitary neuroendocrine tumors-PitNET) had significantly higher values of rCBV with cut-off points set at 3.45 and 3.54, respectively (mean rCBV). Additionally, meningiomas presented significantly higher maximum and mean maximum rPH values compared to adenomas. DSC PWI imaging adds significant value to conventional MRI examinations and can be helpful in differentiating equivocal pituitary tumors.

Advanced magnetic resonance imaging findings of cerebellar hemangioblastomas: A report of three cases and a literature review

On conventional magnetic resonance imaging (MRI), hemangioblastomas typically appear as mural nodules with an adjacent surrounding cyst or a solid mass in the cerebellum. However, hemangioblastomas sometimes cannot be reliably distinguished using this imaging technique from other tumors, especially pilocytic astrocytomas and metastatic tumors, because of their similar imaging findings and locations. Herein, we report three cases of cerebellar hemangioblastomas and review their findings on conventional and advanced MRI, including diffusion-weighted imaging (DWI), dynamic susceptibility-weighted contrast-enhanced perfusion-weighted imaging (DSC-PWI), and magnetic resonance spectroscopy (MRS). Solid contrast-enhanced lesions of hemangioblastomas showed increased apparent diffusion coefficient values on DWI, increased relative cerebral blood volume ratio on DSC-PWI, and high lipid/lactate peak on MRS. Therefore, advanced MRI techniques can be helpful in understanding the pathological and metabolic changes of hemangioblastomas and may be useful for their characterization.

Cerebellar hemangioblastoma: Case report with review of the literature

Originally recognized by Cushing and Bailey, hemangioblastoma is a developmental vascular neoplasm that is predominantly found in the posterior fossa. It is a highly vascularized tumor, with well-differentiated histologic features. Although rare, it remains the most common primary tumor of cerebellum in adults, along with metastases. MRI is the gold standard, allowing a precise characterization of the lesion's features, and its relationship with the surrounding structures. We report the case of a patient with a cerebellar symptomatology, in whom brain MRI raises the diagnosis of hemangioblastoma, which was then confirmed by histopathologic examination.

Pediatric Cerebellar Pilomyxoid Astrocytoma: Clinical and Radiological Findings in Three Cases

Pilomyxoid astrocytomas (PMA) is a particular form of glial tumors distinct from pilocytic astrocytomas (PA). On the last 2016 WHO classification for CNS tumours, no definite grade assignment was proposed for these lesions. They may be more aggressive with a different clinical course compared to PA due to their greater propensity for local recurrence and cerebrospinal dissemination. Most cases arise from the hypothalamic region. Only few studies reported cerebellar localization of the lesion. We report 3 pediatric cases treated for pediatric PMA of the posterior fossa. Clinical, radiological, and prognostic features were reviewed. The age of our patients was between 1 and 9 years old. Signs of intracranial hypertension were found in all patients. One of them presented an increased head circumference and the 2 others had a cerebellar syndrome. Brain CT-scan and MRI displayed a large wellcircumscribed intra-axial solid and cystic posterior fossa tumor. Total surgical resection was performed for all tumors. After a 2 years follow up, no signs of recurrence were noticed. In the literature, PMA been reported with overwhelming majority in children aged between 2 months and 4 years. Despite of many pathological similarities with PAs, PMAs have some specific features in histology, leading to their identification as independent type of glioma. Radiological differential diagnosis between PMAs and Pas can be made using arterial spin labeling imaging, which shows low perfusion parameters in PAs. Clinical and radiological follow up are mandatory do to different natural history and higher rates of local recurrence of this tumor compared to PA. Prognosis is favorable when complete surgical exeresis is possible.

A solitary hemangioblastoma of the posterior brain fossa: the role of radiotherapy

We report here the case of a patient admitted for management of posterior fossa cerebral hemangioblastoma. A 16-year-old male patient with a history of intracranial hypertension syndrome consisting of progressively worsening headache, vomiting, especially morning and jet vomiting, and decreased visual acuity. The patient's symptomatology worsened a few days later with the appearance of a disturbance of balance with enlargement of the sustentation polygon. The patient initially benefited from a brain computed tomography (CT) scan that objectified a solidocystic process of the posterior brain fossa. The patient then underwent a surgical excision that was considered partial and the diagnosis of hemangioblastoma was made on the surgical specimen. Since the surgical removal was partial the patient was referred to our training where he received external radiotherapy on his hemangioblastoma of the posterior brain fossa. The patient was examined one month after the end of irradiation; he presented a spectacular improvement in his neurological symptomatology with a clear regression of balance disorders. The standard treatment for cerebellar hemangioblastoma is complete microsurgical removal, but our results show a high level of efficacy for fractional photon radiotherapy after partial surgery of this benign tumour.

Posterior fossa tumors in children: Radiological tips & tricks in the age of genomic tumor classification and advance MR technology

Imaging plays a major role in the comprehensive assessment of posterior fossa tumor in children (PFTC). The objective is to propose a global method relying on the combined analysis of radiological, clinical and epidemiological criteria, (taking into account the child's age and the topography of the lesion) in order to improve our histological approach in imaging, helping the management and approach for surgeons in providing information to the patients' parents. Infratentorial tumors are the most frequent in children, representing mainly medulloblastoma, pilocytic astrocytoma and brainstem glioma. Pre-surgical identification of the tumor type and its aggressiveness could be improved by the combined analysis of key imaging features with epidemiologic data.

The role of diffusion and perfusion magnetic resonance imaging in differentiation of haemangioblastomas and pilocytic astrocytomas

Purpose

Haemangioblastomas (HABLs) and pilocytic astrocytomas (PAs) are brain tumours presenting similar appearance and location in conventional magnetic resonance (MR) imaging. The purpose of our study was to determine whether a detailed analysis of diffusion (DWI) and perfusion (PWI) characteristics can be useful in preoperative differentiation of these tumours.

Material and methods

The study group consisted of biopsy proven six HABLs and six PAs, which underwent preoperative standard MR examinations including PWI and DWI. In PWI relative cerebral blood volume (rCBV) and the shape of perfusion curves (parameters of peak height - rPH and percentage of signal recovery - rPSR) were analysed. All perfusion parameters were measured for the entire tumour core (mean rCBV, mean rPH, mean rPSR) and in regions with maximal values (max rCBV, max rPH, max rPSR). In DWI parameters of apparent diffusion coefficient (ADC) from the entire tumour core (mean ADC) and in regions with minimal values (min ADC) were evaluated.

Results

Compared to PAs, HABLs presented significantly higher rCBV and rPH values and lower mean rPSR value. PAs showed significantly lower rCBV and rPH values and higher mean rPSR value. Mean rCBV showed no overlap in the values between HABLs and PAs, and thus it provided the highest accuracy in differentiating between them. Max rPSR, mean ADC, and min ADC did not show any significant differences.

Conclusions

High rCBV values and deep perfusion curves with only partial return to the baseline are characteristic features of HABLs differentiating them from PAs, which show lower rCBV values and perfusion curves overshooting the baseline. Diffusion parameters are not useful in differentiation of these tumours.

Differentiating Hemangioblastomas from Brain Metastases Using Diffusion-Weighted Imaging and Dynamic Susceptibility Contrast-Enhanced Perfusion-Weighted MR Imaging

BACKGROUND AND PURPOSE

On DWI and DSC-PWI, hemangioblastomas and brain metastases may exhibit different signal intensities depending on their cellularity and angiogenesis. The purpose of this study was to evaluate whether a hemangioblastoma can be differentiated from a single brain metastasis with DWI and DSC-PWI.

MATERIALS AND METHODS

We retrospectively reviewed DWI, DSC-PWI, and conventional MR imaging of 21 patients with hemangioblastomas and 30 patients with a single brain metastasis. Variables of minimum ADC and relative ADC were acquired by DWI and the parameter of relative maximum CBV, by DSC-PWI. Minimum ADC, relative ADC, and relative maximum CBV values were compared between hemangioblastomas and brain metastases by using the nonparametric Mann-Whitney test. The sensitivity, specificity, positive and negative predictive values, accuracy, and the area under the receiver operating characteristic curve were determined.

RESULTS

Both the minimum ADC values and relative ADC ratios were significantly higher in hemangioblastomas compared with brain metastases (P < .001 for both minimum ADC values and relative ADC ratios). The same was true for the relative maximum CBV ratio (P < .002). The threshold value of ≥6.59 for relative maximum CBV provided sensitivity, specificity, and accuracy of 95.24%, 53.33%, and 70.59%, respectively, for differentiating hemangioblastomas from brain metastases. Compared with relative maximum CBV, relative ADC had high sensitivity (95.24%), specificity (96.67%), and accuracy (96.08%) using the threshold value of ≥1.54. The optimal threshold value for minimum ADC was ≥1.1 × 10^-3 mm²/s.

CONCLUSIONS

DWI and DSC-PWI are helpful in the characterization and differentiation of hemangioblastomas from brain metastases. DWI appears to be the most efficient MR imaging technique for providing a distinct differentiation of the 2 tumor types.

High accuracy of arterial spin labeling perfusion imaging in differentiation of pilomyxoid from pilocytic astrocytoma

INTRODUCTION

Pilomyxoid astrocytoma (PMA) is a relatively new tumor entity which has been added to the 2007 WHO Classification of tumors of the central nervous system. The goal of this study is to utilize arterial spin labeling (ASL) perfusion imaging to differentiate PMA from pilocytic astrocytoma (PA).

METHODS

Pulsed ASL and conventional MRI sequences of patients with PMA and PA in the past 5 years were retrospectively evaluated. Patients with history of radiation or treatment with anti-angiogenic drugs were excluded.

RESULTS

A total of 24 patients (9 PMA, 15 PA) were included. There were statistically significant differences between PMA and PA in mean tumor/gray matter (GM) cerebral blood flow (CBF) ratios (1.3 vs 0.4, p < 0.001) and maximum tumor/GM CBF ratio (2.3 vs 1, p < 0.001). Area under the receiver operating characteristic (ROC) curves for differentiation of PMA from PA was 0.91 using mean tumor CBF, 0.95 using mean tumor/GM CBF ratios, and 0.89 using maximum tumor/GM CBF. Using a threshold value of 0.91, the mean tumor/GM CBF ratio was able to diagnose PMA with 77 % sensitivity, 100 % specificity, and a threshold value of 0.7, provided 88 % sensitivity and 86 % specificity. There was no statistically significant difference between the two tumors in enhancement pattern (p = 0.33), internal architecture (p = 0.15), or apparent diffusion coefficient (ADC) values (p = 0.07).

CONCLUSION

ASL imaging has high accuracy in differentiating PMA from PA. The result of this study may have important applications in prognostication and treatment planning especially in patients with less accessible tumors such as hypothalamic-chiasmatic gliomas.

Differentiation of hemangioblastomas from pilocytic astrocytomas using 3-T magnetic resonance perfusion-weighted imaging and MR spectroscopy

INTRODUCTION

Hemangioblastomas and pilocytic astrocytomas (PAs) present similar imaging features on conventional MR imaging, making differential diagnosis a challenge. The purpose of this study was to evaluate the usefulness of dynamic susceptibility-weighted contrast-enhanced perfusion-weighted imaging (DSC-PWI) and proton MR spectroscopic imaging in the differentiation of hemangioblastomas and PAs.

METHODS

A 3.0-T MR imaging unit was used to perform DSC-PWI and conventional MR imaging on 14 patients with hemangioblastomas and 22 patients with PAs. Four patients with hemangioblastomas and 10 PA patients also underwent proton MR spectroscopy. Parameters of relative peak height (rPH) and relative percentage of signal intensity recovery (rPSR) were acquired by DSC-PWI and variables of N-acetylaspasrtate (NAA)/creatine (Cr), choline (Cho)/Cr, and lactate-lipid (Lac-Lip)/Cr by MR spectroscopy. The sensitivity, specificity, and the area under the receiver operating characteristic curve of all analyzed parameters at respective cutoff values were determined.

RESULTS

Higher rPH but lower rPSR values were detected in hemangioblastomas compared to PAs. The NAA/Cr ratio was significantly lower in hemangioblastomas compared with PAs. The threshold values ≥3.2 for rPH provide sensitivity, specificity, positive predictive values, and negative predictive values of 85.7, 95.5, 92.3, and 91.3%, respectively, for differentiating hemangioblastomas from PAs. The optimal threshold values were ≤0.9 for rPSR and ≤1.5 for NAA/Cr ratios in tumor.

CONCLUSION

Significantly higher rPH and lower NAA/Cr were seen in patients with hemangioblastomas when compared with PA patients, suggesting that DSC-PWI and proton MR spectroscopy are helpful in the characterization and differentiation of these two types of tumors.

Surgical resection of sporadic and hereditary hemangioblastoma: Our 10-year experience and a literature review

Background:

Hemangioblastomas (HBLs) are benign neoplasms that contribute to 1-2.5% of intracranial tumors and 7-12% of posterior fossa lesions in adult patients. HBLs either evolve hereditarily in association with von Hippel–Lindau disease (vHL) or, more prevalently, as solitary sporadic tumors. Only few authors have reported on the clinical presentation and the neurological outcome of HBL.

Methods:

We retrospectively analyzed the clinical, radiological, surgical, and histopathologic records of 24 consecutive patients (11 men, 13 women; mean age 51.3 years) with HBL of the posterior cranial fossa, who had been treated at our center between 2001 and 2012. We reviewed the current literature, and discussed our findings in the context of previous publications on HBL. The study protocol was approved by the local ethics committee (14-101-0070).

Results:

Mean time to diagnosis was 14 weeks. The extent of resection (EOR) was total in 20 and near total in 4 patients. Four patients required revision within 24 h because of relevant postoperative bleeding. One patient died within 14 days. One patient required permanent shunting. At discharge, 75% of patients [n = 18, modified Rankin scale (mRS) 0-1] showed no or at least resolved symptoms. Mean follow-up was 21 months. Two recurrences were detected during follow-up.

Conclusions:

In comparison to other benign entities of the posterior fossa, time to diagnosis was significantly shorter for HBL. This finding indicates the rather aggressive biological behavior of these excessively vascularized tumors. In our series, however, the rate of complete resection was high, and morbidity and mortality rates were within the reported range.

Perfusion imaging in brain disease

Perfusion CT or MRI have been extensively developed over the last years and are accessible on most imaging machines. Perfusion CT has taken a major place in the assessment of a stroke. Its role has to be specified for the diagnosis and treatment of the vasospasm, complicating a subarachnoid hemorrhage. Perfusion MRI should be included in the assessment of any brain tumor, both at the time of the diagnosis as well as in the post-treatment monitoring. It is included in the multimodal approach required for the optimum treatment of this disease. The applications in epilepsy and the neurodegenerative diseases are in the evaluation process.

Conventional and advanced MRI features of pediatric intracranial tumors: posterior fossa and suprasellar tumors

OBJECTIVE

In this article, we review the most common posterior fossa and suprasellar intracranial neoplasms in the pediatric population. We briefly discuss basic MRI concepts used in the initial evaluation of a pediatric brain tumor and then discuss sophisticated MRI techniques that give insight into the physiology and chemical makeup of these tumors to help the radiologist make a more specific diagnosis.

CONCLUSION

Diagnosis and treatment of pediatric CNS tumors necessitate a multi-disciplinary approach and require expertise and diligence of all parties involved. Imaging is an essential component has evolved greatly over the past decade. We are becoming better at making a preoperative diagnosis of that tumor type, detecting recurrence, and guiding surgical management to avoid injury to vital brain structures.

Sporadic intracranial haemangioblastomas: surgical outcome in a single institution series

BACKGROUND

Haemangioblastomas are benign vascular tumours that may appear sporadically or in von Hippel-Lindau disease. Despite their higher incidence, sporadic haemangioblastomas have been less studied than syndromic ones. In this article, we evaluate the specific features, outcome and quality of life of patients with intracranial sporadic haemangioblastomas (ISHs) operated on in our institution.

METHODS

Between 1998 and 2010, 38 patients harbouring 38 ISHs were operated on in our department. Their clinical, biological, radiological and surgical features were retrospectively reviewed. All patients were contacted for a quality-of-life (QOL) survey assessed by the Short Form 36 questionnaire (SF36). The mean duration of follow-up was 40 months (13-108 months).

RESULTS

ISH represented 0.9 % of primary intracranial neoplasms treated in our centre during this period. Patients comprised 23 men and 15 women with a mean age of 47 years. None had polycythaemia. Cerebellar locations accounted for 79 % of ISHs, and brainstem ISH with involvement of the floor of the fourth ventricle represented 11 % of ISHs. At last follow-up, two patients harbouring solid medulla oblongata haemangioblastoma had died following severe bulbar syndrome and five patients had died of unrelated causes. One patient had multiple surgeries for three recurrences. Tumoral control was achieved in all cases at last follow-up. Results of the SF-36 questionnaire were as follows: median physical functioning score 100 (range 0-100), median physical problems score 100 (range 0-100), median bodily pain score 100 (range 45-100), median social functioning score 100 (range 25-100), median general mental health score 84 (range 40-92), median emotional problems score 100 (range 0-100), median vitality score 70 (range 35-80) and median general health perceptions score 70 (range 35-100). Mean QOL scores were similar to the general healthy population.

CONCLUSION

Surgery of ISH provides good QOL and tumoral control except for those located in the medulla oblongata. We recommend considering a careful multimodal therapeutic approach, including radiosurgery for these specific locations.

Mean intensity curve on dynamic contrast-enhanced susceptibility-weighted perfusion MR imaging--review of a new parameter to differentiate intracranial tumors

Dynamic susceptibility contrast (DSC) perfusion imaging has been in clinical use for various indications, including characterization and grading of intracranial neoplasms. However, several technical factors can lead to pitfalls in image interpretation. This review discusses the extraction of T1 and T2* information from mean curve analysis of DSC perfusion imaging of various brain tumors, which provides further insights into tumor biology and, thus, may be useful in the differential diagnosis of such tumors. Indeed, by looking at the mean time-signal intensity curve from the tumor bed in addition to the rCBV maps, it is possible to obtain further inferences of capillary density and lesion leakiness. When dynamic contrast enhanced (DCE) T1 perfusion is not available, DSC perfusion with mean curve analysis appears to be a valid alternative for characterizing various brain neoplasms in a routine clinical setting.

[Grading of adults primitive glial neoplasms using arterial spin-labeled perfusion MR imaging]

PURPOSE

We investigated the relationship between tumor blood-flow measurement based on perfusion-imaging by arterial spin-labeling (ASL) and histopathologic findings in adults' primitive glial tumours.

PATIENTS AND METHODS

Thus, 40 primitive brain tumors (8 low-grade and 32 high-grade gliomas according to the Sainte-Anne classification) were imaged using pulsed (n=19) or continuous (n=21) ASL. Relative cerebral blood flow (rCBF=tumoral blood flow/normal cerebral blood flow) between high- and low-grade gliomas were compared.

RESULTS

Using pulsed ASL, differences in mean rCBF were observed in high- and low-grade gliomas although no significant (respectively 1.95 and 1.5). Using continuous ASL, mean rCBF were significantly higher for high-grade than for low-grade gliomas (P<0.05). High-grade gliomas could be discriminated using a CBF threshold of 1.18, with a sensitivity of 88%, specificity of 60%, predictive positive value of 88%, and predictive negative value of 60%.

CONCLUSION

ASL-based perfusion provides a quantitative, non-invasive alternative to dynamic susceptibility contrast perfusion MR methods for evaluating CBF. ASL is a suitable method for gliomas initial staging and could be useful to identify intermediate tumoral evolution.