Infratentorial pediatric brain tumors: the value of new imaging modalities. (25/77)

The correct assessment of the four most frequent infratentorial brain tumors in children (medulloblastoma, ependymoma, pilocytic astrocytoma and infiltrating glioma) has always been problematic. They are known to often resemble one another on conventional magnetic resonance (MR) imaging. We tested the hypothesis whether the combined strength of diffusion-weighted imaging (DWI) and proton MR spectroscopy (MRS) could help differentiate these tumors. Seventeen children with untreated posterior fossa tumors were investigated between January 2005 and January 2006 with conventional MR imaging and combined DWI and MR spectroscopy using a single-voxel technique at short and long echo time (TE) of 30 ms and 135 ms respectively. Apparent diffusion coefficient (ADC) values were retrieved after regions of interest were manually positioned within non necrotic tumor core. Water signal was quantified and metabolite signals were compared and analyzed using linear discriminant analysis. When a combination of ADC values and normalized metabolites was used, all tumors could be discriminated against one other. This could only be achieved when metabolites were normalized using water as an internal standard. They could not be discriminated when using metabolite ratios or ADC values alone, nor could they be differentiated using creatine (Cr) as an internal reference even in combination with ADC values. In conclusion, linear discriminant analysis and multiparametric combination of DWI and MRS, although not replacing histology, fully discriminates the four most frequent posterior fossa tumors in children, but metabolites have to be normalized using water and not Cr signal as an internal reference.  (+info)

Comparison of FSE T2W and 3D FIESTA sequences in the evaluation of posterior fossa cranial nerves with MR cisternography. (26/77)

PURPOSE: The aim of this study was to compare 3D fast imaging with steady state acquisition (3D FIESTA) to fast spin echo T2-weighted (FSE T2W) MRI sequences in the imaging of cisternal parts of cranial nerves V-XII. MATERIALS AND METHODS: We retrospectively evaluated the temporal MRI sequences of 50 patients (F:M ratio, 27:23; mean age, 44.5 +/- 15.9 years) who were admitted to our hospital with vertigo, tinnitus, and hearing loss. In all, we evaluated 800 nerves. Two radiologists, working independently, divided the imaging findings into 3 groups: 0 (not visualized), 1 (partially visualized), and 2 (completely visualized). RESULTS: The rate of visualization of these cranial nerves with FSE T2W and 3D FIESTA sequences, respectively, (partially and completely visualized) were as follows: nerve V (100% and 100%); nerve VI (43% and 98%); nerve VII (100% and 100%); nerve VIII (100% and 100%); nerve IX-XI complex (67% and 100%); nerve XII (2% and 91%). CONCLUSION: 3D FIESTA sequences are superior to FSE T2W sequences in the imaging of cisternal parts of the posterior fossa nerves. 3D FIESTA sequences may be used for obtaining high-resolution MR cisternography images.  (+info)

Ganglioneuroblastoma of the cerebellum: neuroimaging and pathological features of a case. (27/77)

OBJECTIVE: To report a case of ganglioneuroblastoma of cerebellum, with emphasis to the neuroimaging and pathological findings. CASE REPORT: A one year and eight-month-old girl presented with a two-month history of hypoactivity and tremor in the legs. The MRI showed an enhancing cerebellar mass hypointense on T1 and hyperintense on T2-weighted images. The patient underwent a craniotomy with resection of the lesion. The histological and immunohistochemical studies defined the diagnosis of ganglioneuroblastoma. CONCLUSION: The MRI findings of our case showed no features which could help in the differentiation between ganglioneuroblastoma and the other common types of posterior fossa neoplasms in the pediatric population.  (+info)

Meningioma in the posterior fossa without dural attachment. (28/77)

A 14-year-old boy presented with a very rare meningioma in the posterior cranial fossa without dural attachment. Magnetic resonance imaging revealed a 3-cm, well-circumscribed, heterogeneously enhanced, round mass without dural tail sign in the right side of the posterior fossa. Right vertebral angiography revealed very faint tumor staining supplied by the right posterior inferior cerebellar artery. Total removal of the tumor was performed. Intraoperatively, the mass exhibited no attachment to the dura mater, cerebellar parenchyma, or choroid plexus, but was firmly attached to the arachnoid tissue near the foramen of Luschka. Histological and immunohistochemical studies established the diagnosis of meningothelial meningioma (World Health Organization grade I).  (+info)

Duraplasty in the posterior fossa using a boat-shaped sheet of expanded polytetrafluoroethylene. (29/77)

Application of sutures between expanded polytetrafluoroethylene (ePTFE) dural substitutes and the dura mater is often frustrating in posterior fossa surgery because of the difficulty in holding the elastic graft in a deep and narrow field. To resolve this problem, we have developed a boat-shaped graft made from a triangular ePTFE sheet by pinching each angle using a suture. Formation of standing edges of the sheet facilitates holding of the flaps for secure and more rapid suturing than the conventional approach using a flat sheet.  (+info)

Multi-institution prospective trial of reduced-dose craniospinal irradiation (23.4 Gy) followed by conformal posterior fossa (36 Gy) and primary site irradiation (55.8 Gy) and dose-intensive chemotherapy for average-risk medulloblastoma. (30/77)

PURPOSE: Limiting the neurocognitive sequelae of radiotherapy (RT) has been an objective in the treatment of medulloblastoma. Conformal RT to less than the entire posterior fossa (PF) after craniospinal irradiation might reduce neurocognitive sequelae and requires evaluation. METHODS AND MATERIALS: Between October 1996 and August 2003, 86 patients, 3-21 years of age, with newly diagnosed, average-risk medulloblastoma were treated in a prospective, institutional review board-approved, multi-institution trial of risk-adapted RT and dose-intensive chemotherapy. RT began within 28 days of definitive surgery and consisted of craniospinal irradiation (23.4 Gy), conformal PF RT (36.0 Gy), and primary site RT (55.8 Gy). The planning target volume for the primary site included the postoperative tumor bed surrounded by an anatomically confined margin of 2 cm that was then expanded with a geometric margin of 0.3-0.5 cm. Chemotherapy was initiated 6 weeks after RT and included four cycles of high-dose cyclophosphamide, cisplatin, and vincristine. RESULTS: At a median follow-up of 61.2 months (range, 5.2-115.0 months), the estimated 5-year event-free survival and cumulative incidence of PF failure rate was 83.0% +/- 5.3% and 4.9% +/- 2.4% (+/- standard error), respectively. The targeting guidelines used in this study resulted in a mean reduction of 13% in the volume of the PF receiving doses >55 Gy compared with conventionally planned RT. The reductions in the dose to the temporal lobes, cochleae, and hypothalamus were statistically significant. CONCLUSION: This prospective trial has demonstrated that irradiation of less than the entire PF after 23.4 Gy craniospinal irradiation for average-risk medulloblastoma results in disease control comparable to that after treatment of the entire PF.  (+info)

Enlargement of postoperative aqueductal air due to elevated body temperature. Case report. (31/77)

Pneumocephalus has been reported after posterior fossa surgery especially with procedures performed in the sitting position. The gravitational effect is the decisive factor in the development of pneumocephalus. The entrapped air in the aqueduct may enlarge due to several factors such as elevated body temperature and may cause to deterioration in neurological status. We report a rare case of tension pneumocephalus associated with the enlargement of massive air in aqueduct due to elevated body temperature, following removal of a cervicomedullary tumor. We believe her neurological deterioration was due to the compression of the reticular formation by dilatation of postoperative air in the aqueduct due to the elevation of her body temperature.  (+info)

The prognostic value of histological grading of posterior fossa ependymomas in children: a Children's Oncology Group study and a review of prognostic factors. (32/77)

We performed a retrospective analysis of 96 pediatric posterior fossa ependymomas in order to determine the prognostic value of histological grade based on the current WHO grading scheme. The patients were selected among Children's Oncology Group (previously Pediatric Oncology Group-POG) patients enrolled in clinical trials, and on the basis of central pathology review, location, and age. We excluded entities such as sub-ependymoma, myxopapillary, or clear-cell ependymoma, after a consensus diagnosis by three neuropathologists. A total of 66 males and 30 females with a median age of 48 months were identified. The group was analyzed to determine the effects of histological grade, age, gender, and extent of resection on event-free and overall survival. Our results showed that extent of resection, age, and histological grade were independent prognostic variables for event-free survival. The relative risk for extent of resection and histological grade was calculated as 3.59 (P<0.001) and 3.58 (P<0.001), respectively. Overall survival significantly correlated with extent of resection and age, but not with histological grade. We compared our results with peer-reviewed publications on pediatric intracranial ependymomas in the English language between 1990 and 2005. Selection criteria identified 32 manuscripts involving 1444 patients. Extent of resection was a significant factor in 21, age in 12, and histological grading in nine of these studies. Other factors reported to be significant by more than one study included tumor location and radiation treatment. Our findings suggest that histological grade (WHO Grade II vs III) is an independent prognostic indicator for event-free survival, but may not be so for overall survival in pediatric posterior fossa ependymomas. We believe that an accurate assessment of the prognostic value of histological grade depends on the selection of a well-characterized clinical cohort of sufficient size, and the inclusion of relevant histological criteria as outlined in the WHO classification scheme.  (+info)