White matter integrity on fractional anisotropy maps in encephalopathic neonates post hypothermia therapy with normal-appearing MR imaging.

BACKGROUND: Neonatal encephalopathy (NE) is a clinically defined neurological syndrome commonly caused by ischemia. OBJECTIVE: We investigated white matter integrity in children with NE using diffusion tensor imaging (DTI) and examined the hypothesis that white matter insults not visible on conventional MRI may have abnormal fractional anisotropy (FA) on DTI. MATERIALS AND METHODS: DTI was performed on 36 term encephalopathic neonates who had hypothermia therapy. Of these, 12 neonates had normal conventional MRI findings (NNE) and 24 neonates had abnormal MRI findings (ANE). Twelve term-equivalent premature neonates with normal clinical neuroimaging and neurological function served as the control group. RESULTS: We found significant reductions in measured FA in white matter in the ANE neonates compared to the control group. There were, however, no significant differences in measured FA in white matter between the NNE and the control group. CONCLUSION: We did not find white matter changes detectable by DTI in encephalopathic neonates post hypothermia with normal conventional MRI findings. Further studies would be required to determine whether this unexpected finding is a direct result of neuroprotective effects of hypothermia, or more sophisticated measures of FA are required to detect subtle white matter injury.

Dialysis disequilibrium syndrome occurring during continuous renal replacement therapy.

The dialysis disequilibrium syndrome (DDS) is characterized by progressive neurological symptoms and signs attributable to cerebral edema that occurs due to fluid shifts into the brain following a relatively rapid decrease in serum osmolality during hemodialysis (HD). Since continuous renal replacement therapy (CRRT) is less efficient at solute clearance than intermittent HD, it seems logical that this mode of therapy is less likely to cause DDS. This entity has not been previously reported to occur with this modality. Here, we report two cases of DDS associated with CRRT that provide insights into its pathophysiological mechanisms and suggest strategies for its prevention.

Magnetic resonance imaging in the analysis of pediatric orbital tumors: utility of diffusion-weighted imaging.

PURPOSE: To identify common radiographic features of pediatric orbital tumors by the use of magnetic resonance imaging (MRI) techniques, diffusion-weighted imaging (DWI), fat saturated T2, and pre- and postgadolinium T1. DWI is hypothesized to help identify and predict the malignancy of specific brain tumors. To our knowledge, a similar analysis in which the authors have used this combination of MRI techniques has not been performed with orbital tumors. METHODS: We performed a retrospective chart review of all patients younger than 18 years of age, each diagnosed with an orbital mass lesion, imaged by MRI from 2005 to 2008. The MR images were analyzed by use of the aforementioned techniques. RESULTS: Mass lesions identified in the chart review included rhabdomyosarcoma (n = 4), myofibroma (n = 2), hemangioma (n = 4), lymphangioma (n = 2), neurofibroma (n = 4), Langerhans histiocytosis (n = 2), and one of each of the following: giant cell tumor, meningioma, lymphoid hyperplasia of the lacrimal gland (chronic sclerosing sialadenitis), optic nerve glioma, lipodermoid, and dermoid. DWI was used to differentiate tumors into those with increased diffusion, restricted diffusion, and a mixed diffusion pattern. Capillary hemangiomas and rhabdomyosarcomas 2 tumors with potentially overlapping appearances with traditional MRI techniques had contrasting appearances with DNI. CONCLUSIONS: DWI can help to distinguish among certain pediatric orbital tumors when combined with traditional MRI techniques. This technique may thus be considered an additional tool to help, refine the differential diagnosis of orbital tumors in children.

Postoperative cerebellar mutism syndrome following treatment of medulloblastoma: neuroradiographic features and origin.

OBJECT: The origin and long-term outcome of cerebellar mutism syndrome (CMS), a postoperative syndrome of diminished speech, hypotonia, and ataxia that affects approximately 25% of patients with medulloblastoma, is poorly elucidated. The current study was undertaken to determine factors associated with development of CMS, a means to determine its severity or cause, and outcomes of patients with this syndrome. METHODS: The study included 28 children with medulloblastoma who either underwent an operation or were referred to the authors' institution soon after surgery. Eleven (39%) of these children had CMS. The preoperative, immediate postoperative, and 1-year postoperative MR images were reviewed by a neuroradiologist blinded to diagnosis of CMS. The severity of mutism and neurological and neurocognitive outcomes were examined. RESULTS: Preoperative MR images showed no differences in tumor size, hydrocephalus, or peritumoral edema in patients with and without CMS. An association with brainstem invasion was significant (p < 0.05), and there was a trend toward an association with involvement of the cerebellomedullary angle (p = 0.08). Images obtained immediately postoperatively showed cerebellar edema in 92% of all patients; there were trends for more middle and superior cerebellar peduncle edema in patients with CMS (p = 0.05 and 0.07, respectively). At 1 year postoperatively, patients with CMS showed more moderate to severe atrophy/gliosis of total cerebellum (p < 0.01), vermis (p < 0.01), and brainstem (p < 0.05). Mean IQ was 16 points lower in patients with CMS (IQ = 84.2 +/- 15.8) compared with those without CMS (IQ = 100.4 +/- 17.4), with a trend toward significance (p = 0.07). CONCLUSIONS: This study demonstrates that CMS is associated with postoperative damage to the cerebellum and brainstem, damage not predicted by immediate postoperative MR imaging, and with poorer associated functional outcome.

The cerebellar mutism syndrome and its relation to cerebellar cognitive function and the cerebellar cognitive affective disorder.

The postoperative cerebellar mutism syndrome (CMS), consisting of diminished speech output, hypotonia, ataxia, and emotional lability, occurs after surgery in up to 25% of patients with medulloblastoma and occasionally after removal of other posterior fossa tumors. Although the mutism is transient, speech rarely normalizes and the syndrome is associated with long-term adverse neurological, cognitive, and psychological sequelae. The clinical, neuroradiographic, and neuropsychological findings associated with CMS as well as possible mechanisms of injury are reviewed. Theories about the pathophysiology of CMS have evolved along with our understanding of the cerebellum as an important structure in the distributive neurocircuitry underlying complex speech, cognition, and behavior. CMS shares many similarities with the cerebellar cognitive affective syndrome, more commonly described in adults and consisting of disturbances of executive function, visuospatial skills, nonmotor language, and affect regulation. Future directions include more thorough neuropsychological characterization, functional and diffusion tensor imaging studies, and investigations into the underlying differences that may make some patients more vulnerable to CMS.

Diffusion-weighted MR imaging of early methotrexate-related neurotoxicity in children.

BACKGROUND AND PURPOSE: Methotrexate is a major cause of treatment-related acute neurotoxicity in children with hematologic malignancies. The purpose of this study was to investigate whether diffusion-weighted MR imaging (DWI) detects acute methotrexate white matter neurotoxicity in this patient population. METHODS: Six children-three female and three male-with hematologic malignancies were studied at time of onset of neurologic dysfunction during the delayed intensification or consolidation phase of therapy, when intensive intrathecal methotrexate is given. MR imaging including DWI was performed on 1.5 T MR scanners. RESULTS: DWI demonstrated abnormal restriction of motion of water in the centrum semiovale in all six patients. This finding correlated to the acute onset of hemiparesis or aphasia. Fluid-attenuated inversion recovery imaging was not positive at this time, but it was positive in all five patients in whom follow-up imaging was performed. CONCLUSION: Early detection of methotrexate white matter injury by DWI has the potential to alert the oncologist to this event and provide a technique by which treatment of neurotoxicity can be monitored.

Choroid plexus carcinomas in children: MRI features and patient outcomes.

Choroid plexus carcinomas (CPC) are rare malignant intracranial neoplasms usually occurring in young children. The objectives of this study were to characterize the preoperative MRI features of CPC, determine the frequency of disseminated disease in the CNS at diagnosis, and assess patient outcomes. The preoperative cranial MR images of 11 patients with CPC were retrospectively reviewed for lesion location, lesion size, un-enhanced and enhanced MRI signal characteristics, and presence of disseminated intracranial tumor. Postoperative cranial and spinal MRI images were reviewed for residual, recurrent, and/or disseminated tumor. The study group included six male and five female patients ranging in age from 5 months to 5.3 years (median= 1.8 years). CPC were located in the lateral (n = 8), fourth (n = 1), and third (n = 1) ventricles, and foramen of Luschka (n = 1). Mean tumor size was 5.2 cm x 4.9 cm x 5.0 cm. On short-TR images, CPC had heterogeneous, predominantly intermediate signal with foci of high signal in 45% of lesions from areas of hemorrhage. On long-TR/long-TE images, solid portions of CPC typically had heterogeneous, intermediate-to-slightly-high signal. Small zones of low signal on long-TR/long-TE images were seen in 55% of the lesions secondary to areas of hemorrhage and/or calcifications. Tubular flow voids representing blood vessels were seen in 55% of the lesions. Zones of high signal comparable to CSF were seen in 64% of CPC secondary to cystic/necrotic zones. All CPC showed prominent contrast enhancement. Irregular enhancing margins suggesting subependymal invasion were seen in 73% of the lesions. Findings consistent with edema in the brain adjacent to the enhancing lesions were seen in 73% of CPC. CPC caused hydrocephalus in 82% of patients at diagnosis. Two patients died from hemorrhagic complications from surgical biopsies. Disseminated tumor in the leptomeninges was present in 45% of patients at diagnosis and was associated with a poor prognosis. The 1-year and 5-year survival probabilities were 55% and 45%, respectively. In conclusion, MRI features commonly associated with CPC include large intraventricular lesions with irregular enhancing margins; heterogeneous signal on long TR/long TE images and short-TR images; edema in adjacent brain; hydrocephalus; and presence of disseminated tumor. MRI evidence of disseminated tumor at diagnosis is associated with a poor prognosis.

Dose reduction fluoroscopy in pediatrics.

BACKGROUND: It is essential that we find ways to reduce radiation exposure to children and maintain image quality. OBJECTIVES: We compared radiation dose, image quality, and spatial resolution when continuous and pulse fluoroscopy with a full and half dose are applied to a phantom. The film-screen technique was compared to fluoroscopy with the digitized spot technique (fluoro grab image) in procedures such as voiding cystourethrogram (VCUG). MATERIALS AND METHODS: Using a 15.1-cm Plexiglas phantom, we obtained dosimetry in milligrays (mGy), spatial resolution in number of line pairs per millimeter (lp/mm), and threshold contrast resolution in number of visible holes. To measure total radiation dose, we calculated the average elapsed fluoroscopy time for VCUG to be approximately 3 min and estimated the average number of exposures as 10. Dosimetry was obtained for full dose and half dose continuous, for 15 pulses per second (pps), 7.5 pps, and 3.75 pps. These were also calculated with normal, magnification 1, and magnification 2 factors. RESULTS: Results of the two most relevant parameters are shown: continuous full-dose fluoroscopy, 3 min, 10 photo spots, total dose of 28.7 mGy with 2 lp/mm of resolution and a threshold contrast of 2.2%, versus 3.75 pps half-dose fluoroscopy, 3 min, grab images, total dose of 3.7 mGy with 1.9 lp/mm of resolution and a threshold contrast of 2.3%. CONCLUSION: With minimal loss of resolution there is significant dose reduction (87%) when using 3.75 pps with digitized imaging.