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Objective: We hypothesized that the apparent diffusion coefficient (ADC) and other MRI features can be used to predict medulloblastoma histologic subtypes, as defined by the World Health Organization (WHO) in WHO Classification of Tumours of the Central Nervous System., Materials and Methods: A retrospective review of pediatric patients with medulloblastoma between 1989 and 2011 identified 38 patients with both pretreatment MRI and original pathology slides. The mean and minimum tumor ADC values and conventional MRI features were compared among medulloblastoma histologic subtypes., Results: The cohort of 38 patients included the following histologic subtypes: 24 classic medulloblastomas, nine large cell (LC) or anaplastic medulloblastomas, four desmoplastic medulloblastomas, and one medulloblastoma with extensive nodularity. The median age at diagnosis was 8 years (range, 1-21 years) and the median follow-up time was 33 months (range, 0-150 months). The mean ADC (× 10(-3) mm(2)/s) was lower in classic medulloblastoma (0.733 ± 0.046 [SD]) than in LC or anaplastic medulloblastoma (0.935 ± 0.127) (Mann-Whitney test, p = 0.004). Similarly, the minimum ADC was lower in classic medulloblastoma (average ± SD, 0.464 ± 0.056) than in LC or anaplastic medulloblastoma (0.630 ± 0.053) (p = 0.004). The MRI finding of focal cysts correlated with the classic and desmoplastic subtypes (Fisher exact test, p = 0.026). Leptomeningeal enhancement positively correlated with the LC or anaplastic medulloblastoma subtype and inversely correlated with the classic medulloblastoma and desmoplastic medulloblastoma subtypes (p = 0.04). Ring enhancement correlated with tumor necrosis (p = 0.022) and with the LC or anaplastic medulloblastoma histologic subtype (p < 0.001)., Conclusion: The LC or anaplastic medulloblastoma subtype was associated with increased ADC and with ring enhancement, the latter of which correlated with tumor necrosis. These features could be considered in the evaluation of high-risk medulloblastoma subtypes.

Objective: The purpose of this study was to compare both the volumes of the lateral ventricles and the cerebral white matter with gestational age at birth of children with periventricular white matter (PVWM) T2-signal hyperintensities on MR images. The spectrum of neuromotor abnormalities associated with these hyperintensities was also determined., Materials and Methods: We retrospectively reviewed the MR images of 70 patients who were between the ages of 1 and 5 years and whose images showed PVWM T2-signal hyperintensities. The patients were divided into premature (n = 35 children) and term (n = 35) groups depending on their gestational age at birth. Volumetric analysis was performed on four standardized axial sections using T2-weighted images. Volumes of interest were digitized on the basis of gray-scale densities of signal intensities to define the hemispheric cerebral white matter and lateral ventricles. Age-adjusted comparisons of volumetric measurements between the premature and term groups were performed using analysis of covariance., Results: The volume of the cerebral white matter was smaller in the premature group (54 +/- 2 cm(3)) than in the term group (79 +/- 3 cm(3), p < 0.0001). The volume of the lateral ventricles was greater among the patients in the premature group (30 +/- 2 cm(3)) than among those in the term group (13 +/- 1 cm(3), p < 0.0001). Fifty percent of all the premature children had spastic diplegia or quadriplegia. Thirty-two percent of all the term children had hypotonia. There were patients in both groups whose PVWM T2-signal hyperintensities did not correlate with any neuromotor abnormalities but were associated with seizures or developmental delays., Conclusion: The differences in volumetric measurements of cerebral white matter and lateral ventricles in children with PVWM T2-signal hyperintensities are related to their gestational age at birth. Several neurologic motor abnormalities are found in children with such hyperintensities.

Objective: The neurotoxic effects of cyclosporine therapy are well known but poorly understood. Imaging studies typically show subcortical edema predominantly affecting the posterior regions of the brain. We sought to determine the causes for these findings by comparing radiographic data with various clinical parameters., Materials and Methods: In a 3-year period, 16 patients with neurologic findings attributed to cyclosporine therapy were examined with CT, MR imaging, or both. In most cases, imaging was performed both at the onset of the neurologic syndrome and after it had resolved. The radiographic findings were evaluated with respect to lesion location and changes over time. Various clinical and laboratory data obtained throughout the patients' hospital course were also reviewed, including cyclosporine levels, blood pressure values, hematologic data, and serum levels of cholesterol, magnesium, creatinine, and albumin., Results: The only major factor associated with the neurotoxic effects of cyclosporine in all patients was systemic hypertension. Microangiopathic hemolytic anemia, thrombocytopenia, and hypoalbuminemia were also common, and patients usually displayed signs of sympathetic overactivation. The onset of neurologic symptoms was unrelated to serum levels of creatinine, magnesium, cholesterol, or cyclosporine. The clinical and radiographic findings of these patients were identical to those previously reported in patients with hypertensive encephalopathy. Findings resolved in all but one patient after reduction of blood pressure, with or without reduction in cyclosporine dose. In four patients, intracranial hemorrhages occurred during the hypertensive episode, resulting in one fatality., Conclusion: The clinical and radiologic findings in patients showing the neurotoxic effects of cyclosporine appear to be identical to those with hypertensive encephalopathy. Other associated factors, such as cyclosporine-induced vasculopathy or hypoalbuminemia may also play a role in the condition, and intracranial hemorrhage may occur owing to associated thrombocytopenia. Symptoms generally resolve after reduction of blood pressure, and follow-up is usually unnecessary in uncomplicated cases.

Arterial dissection occurs when an intimal tear allows blood to enter the arterial wall, potentially compromising the lumen and reducing blood flow. Carotid and vertebral artery dissections typically occur after major trauma, although they also can arise spontaneously or after trivial injury. Arterial dissection has been associated with a variety of factors, including hypertension, fibromuscular dysplasia, Marfan syndrome, cystic medial necrosis, oral contraceptives, drug abuse (sympathomimetics), and infection [1-8]. It is important to recognize arterial dissection early so that prompt treatment can be initiated to prevent ischemic complications [1]. In this essay, we illustrate the use of MR angiography in the diagnosis of carotid and vertebral artery dissection.

Objective: The purpose of this study was to determine by MR imaging the prevalence and types of dysraphic abnormalities of the spinal cord (i.e., myelodysplasias) associated with urogenital and anorectal malformations of childhood., Materials and Methods: Since 1987, 92 patients with imperforate anus complex, cloacal malformation, and cloacal exstrophy have had MR imaging as a screening examination for occult dysraphic myelodysplasia. The prevalence and types of myelodysplasia were determined for each group., Results: The prevalence of dysraphic myelodysplasia in each group of children was 17% (1/6) for low imperforate anus (ectopic anus), 34% (11/32) for high imperforate anus (with fistulization), 46% (19/41) for cloacal malformation, and 100% (13/13) for cloacal exstrophy. The most common abnormalities in each group were tethered cord with intradural or filar lipoma in imperforate anus; low-placed or dysplastic conus medullaris and tethered cord with lipoma or myelolipoma in cloacal malformation; and lipomyelocele, lipomyelomeningocele, or lipomyelocystocele in cloacal exstrophy., Conclusion: Our results show that the prevalence of myelodysplasia as seen on MR imaging is high in patients with urogenital and anorectal anomalies.

Magnetic resonance imaging (MRI) of the spine was used in 37 infants and children to assess the potential of this new technology to evaluate suspected lumbosacral dysraphic myelodysplasia. Eighteen of these patients had correlative metrizamide myelotomography and metrizamide computed tomography (CT). MRI using a spin-echo pulse sequence with short repetition times (TR) and echo delay times (TE) affords optimal delineation of normal and abnormal spinal cord morphology in the lumbosacral region. Coronal projections usually provide an adequate demonstration of the normal conus medullaris for screening purposes; however, multiplanar acquisitions are necessary for more complete delineation of the dysraphic myelopathy. The sensitivity of MRI compares favorably with metrizamide tomography and CT, although these procedures provide somewhat better specificity. These results suggest that MRI is a reliable, noninvasive procedure to screen patients for lumbosacral dysraphism.