[en] We hypothesize that surgical decompression for Chiari malformation type 1 (CM-1) is associated with statistically significant decrease in tonsillar pulsatility and that the degree of pulsatility can be reliably assessed regardless of the experience level of the reader. An Institutional Review Board (IRB)-approved Health Insurance Portability and Accountability Act (HIPAA)-compliant retrospective study was performed on 22 children with CM-1 (8 males; mean age 11.4 years) who had cardiac-gated true-FISP sequence and phase-contrast cerebrospinal fluid (CSF) flow imaging as parts of routine magnetic resonance (MR) imaging before and after surgical decompression. The surgical technique (decompression with or without duraplasty) was recorded for each patient. Three independent radiologists with different experience levels assessed tonsillar pulsatility qualitatively and quantitatively and assessed peritonsillar CSF flow qualitatively. Results were analyzed. To evaluate reliability, Fleiss kappa for multiple raters on categorical variables and intra-class correlation for agreement in pulsatility ratings were calculated. After surgical decompression, the degree of tonsillar pulsatility appreciably decreased, confirmed by t test, both qualitatively (p values <0.001, <0.001, and 0.045 for three readers) and quantitatively (amount of decrease/p value for three readers 0.7 mm/<0.001, 0.7 mm/<0.001, and 0.5 mm/0.022). There was a better agreement among the readers in quantitative assessment of tonsillar pulsatility (kappa 0.753-0.834), compared to qualitative assessment of pulsatility (kappa 0.472-0.496) and qualitative assessment of flow (kappa 0.056 to 0.203). Posterior fossa decompression with duraplasty led to a larger decrease in tonsillar pulsatility, compared to posterior fossa decompression alone. Tonsillar pulsatility in CM-1 is significantly reduced after surgical decompression. Quantitative assessment of tonsillar pulsatility was more reliable across readers than qualitative assessments of tonsillar pulsatility or CSF flow. (orig.)

[en] Magnetic resonance images of children with hydrocephalus often include a rim of hyperintensity in the periventricular white matter (halo). The purpose of this study was to decide between the hypothesis that the halo is caused by cerebrospinal fluid (CSF) flow during the cardiac cycle, and the alternate hypothesis that the halo is caused by anatomical changes (stretching and compression of white matter). Participants were selected from a multicenter imaging study of pediatric hydrocephalus. We compared 19 children with hydrocephalus to a group of 52 controls. We quantified ventricle enlargement using the frontal-occipital horn ratio. We conducted qualitative and quantitative analysis of diffusion tensor imaging in the corpus callosum and posterior limb of the internal capsule. Parameters included the fractional anisotropy (FA), mean diffusivity, axial diffusivity and radial diffusivity. The halo was seen in 16 of the 19 children with hydrocephalus but not in the controls. The corpus callosum of the hydrocephalus group demonstrated FA values that were significantly decreased from those in the control group (P = 4 . 10^-6), and highly significant increases were seen in the mean diffusivity and radial diffusivity in the hydrocephalus group. In the posterior limb of the internal capsule the FA values of the hydrocephalus group were higher than those for the control group (P = 0.002), and higher values in the hydrocephalus group were also noted in the axial diffusivity. We noted correlations between the diffusion parameters and the frontal-occipital horn ratio. Our results strongly support the hypothesis that the halo finding in hydrocephalus is caused by structural changes rather than pulsatile CSF flow. (orig.)

[en] Purpose: Though radiation therapy is generally considered the most effective treatment for unresectable pilocytic astrocytomas in children, there are few data to support this claim. To examine the efficacy of radiation therapy for pediatric pilocytic astrocytomas, we retrospectively reviewed the experience at our institution. Methods and Materials: Thirty-five patients 18 years old or younger with unresectable tumors and without evidence of neurofibromatosis have been treated since 1982. Patients were treated with local radiation fields to a median dose of 54 Gy. Six patients were treated with radiosurgery to a median dose of 15.5 Gy. Five patients were treated with initial chemotherapy and irradiated after progression. Results: All patients were alive after a median follow-up of 5.0 years. However, progression-free survival was 68.7%. None of 11 infratentorial tumors progressed compared with 6 of 20 supratentorial tumors. A trend toward improved progression-free survival was seen with radiosurgery (80%) compared with external beam alone (66%), but this difference did not reach statistical significance. Eight of the 9 patients progressing after therapy did so within the irradiated volume. Conclusions: Although the survival of these children is excellent, almost one third of patients have progressive disease after definitive radiotherapy. Improvements in tumor control are needed in this patient population, and the optimal therapy has not been fully defined. Prospective trials comparing initial chemotherapy to radiation therapy are warranted.