Evolution of white matter lesions in neurofibromatosis type 1: MR findings.

To characterize further the evolution of white matter lesions in neurofibromatosis type 1, we reviewed 68 MR images in 43 patients (age, 1-31 years), including 25 follow-up studies (mean interval, 27 months). Lesion number, location, morphology, signal characteristics, and contrast enhancement were assessed. Lesion characteristics and changes thereof were correlated with the patients' ages. Thirty-four patients (79%) had white matter lesions. These lesions were hyperintense on T2-weighted images, were isointense on T1-weighted images, and showed no mass effect or contrast enhancement in 31 patients; in three patients, T1-prolongation was observed (one with significant mass effect). None of the lesions evolved into a glioma. The most common locations were the cerebellum (49%), brainstem (22%), and internal capsule (19%). Nineteen patients had white matter lesions and follow-up studies. Lesions decreased in size or number in seven patients (average age, 13 years), showed no change in three (average age, 12 years), increased in size or number in four (average age, 5 years), and showed a mixed pattern (increased/decreased size/number) in four (average age, 7 years). White matter lesions in neurofibromatosis type 1 frequently increase in size or number early in childhood; this did not indicate neoplasia in our study. The lesions tend to resolve with increasing age. Lesion progression in a child more than 10 years old warrants close follow-up to rule out a neoplasm.     

Usefulness of contrast material in MR of patients with neurofibromatosis type 1.

PURPOSEOur objective was to determine the usefulness of routine administration of contrast material in brain MR imaging for the evaluation of areas of probable myelin vacuolization and neoplasms in patients with neurofibromatosis type 1 (NF-1).METHODSWe retrospectively reviewed 112 consecutive contrast-enhanced brain MR studies obtained over a period of 7 years in 109 symptomatic and asymptomatic patients compiled from two institutional NF-1 data bases. MR studies were analyzed for areas of probable myelin vacuolization, with attention to degree of enhancement and its impact on lesion detection and characterization. Usefulness of contrast material was graded as 0 = not useful, 1+ = somewhat useful, and 2+ = useful.RESULTSOf 112 studies, 45% (n = 49) were normal. In the remaining 63 studies, 88 regions of probable myelin vacuolization and 52 tumors were identified. Enhancement was not observed in any regions of probable myelin vacuolization. Enhancement was present in 31% of tumors, and, of these, was found to be useful in 44%, somewhat useful in 12%, and not useful in 44%. For enhancing tumors, contrast agent was useful for lesion detection in 19% and for lesion characterization in 25%.CONCLUSIONContrast administration is useful in baseline MR studies to maximize tumor detection and characterization, to add confidence to the diagnosis of benign probable myelin vacuolization, and to document stability of neoplasms on follow-up examinations.     

Septo-optic dysplasia: MR imaging

Septo-optic dysplasia is the diagnosis when optic nerve hypoplasia is seen in conjunction with dysgenesis of the septum pellucidum. Nearly two-thirds of these patients have hypothalamic-pituitary dysfunction, and half have schizencephaly. The disorder is difficult to classify because of the diversity of clinical and pathologic manifestations. Magnetic resonance images of 11 patients with clinical and radiographic evidence of septo-optic dysplasia were reviewed retrospectively. The "syndrome" appears to include two subsets of patients whose abnormalities have different embryogenesis and neuropathologic findings. The existence of these two subsets helps to explain the diversity of the clinical and radiologic findings.     

Correlation of prenatal events with the development of polymicrogyria.

We report two cases of polymicrogyria in which maternal insults were well documented during the first half of the second trimester of pregnancy. The clinical histories, MR studies, and, in one patient, autopsy results were carefully reviewed, and the timing and nature of the injuries correlated with known developmental events at the time of the injury. Our results support the theory that polymicrogyria results from injury to, or disruption of normal cellular interactions at, the external limiting membrane (the "glial-pial barrier").     

Complex fetal disorders: effect of MR imaging on management--preliminary clinical experience

PURPOSE: To determine the effect of magnetic resonance (MR) imaging findings on management of complex fetal disorders. MATERIALS AND METHODS: MR imaging of the fetus was performed in 25 consecutive pregnant patients referred because of possible complex fetal disorders suspected on the basis of ultrasonographic (US) findings. Spoiled gradient-echo and single-shot rapid acquisition with relaxation enhancement MR imaging were performed in multiple planes anatomic to the fetus during maternal breath holding. RESULTS: In the fetuses in 24 of 25 women, MR studies were technically satisfactory. MR imaging directly influenced fetal care in four (17%) of 24 cases by demonstrating congenital high airway obstruction syndrome, congenital hemochromatosis, unilateral cerebellar deficiency in association with congenital diaphragmatic hernia, and severe facial disfigurement due to a giant anterior neck mass. In eight (33%) cases, MR imaging provided supplementary findings, but did not affect fetal care. In 12 (50%) cases, MR imaging results confirmed US findings. CONCLUSION: In cases of complex fetal disorders, MR imaging results can be used to supplement or confirm US findings and may directly affect management.     

Bilateral frontal polymicrogyria: a newly recognized brain malformation syndrome

BACKGROUND AND OBJECTIVE: Polymicrogyria is a brain malformation characterized by abnormal cortical lamination, excessive cortical folding, and fusion of the cortical molecular layer. Two distinct bilateral localized forms have been described: bilateral perisylvian polymicrogyria, which has proved to be genetically heterogeneous, and bilateral parasagittal parieto-occipital polymicrogyria, which has been described only in sporadic patients. We describe 13 patients with symmetric polymicrogyria of both frontal lobes back to the precentral sulcus: bilateral frontal polymicrogyria (BFP). METHODS: Review of clinical records, brain MRI, and EEG results of 13 patients; correlation with other regional polymicrogyrias. RESULTS: The abnormal cortex extended from the frontal poles anteriorly to the precentral gyrus posteriorly and to the frontal operculum inferiorly and was relatively symmetric in all 13 patients. All patients presented with developmental delay and mild spastic quadriparesis, but variably impaired language development (12/13), mental retardation (11/13), and epilepsy (5/13) also occurred. BFP was sporadic in 13 of 13 patients, but 2 of 13 had consanguineous parents. CONCLUSIONS: BFP extends the spectrum of the recognized bilateral symmetric regional polymicrogyria syndromes.     

Volumetric and surface-based 3D MRI analyses of fetal isolated mild ventriculomegaly

Diagnosis of fetal isolated mild ventriculomegaly (IMVM) is the most common brain abnormality on prenatal ultrasound. We have set to identify potential alterations in brain development specific to IMVM in tissue volume and cortical and ventricular local surface curvature derived from in utero magnetic resonance imaging (MRI). Multislice 2D T2-weighted MRI were acquired from 32 fetuses (16 IMVM, 16 controls) between 22 and 25.5 gestational weeks. The images were motion-corrected and reconstructed into 3D volumes for volumetric and curvature analyses. The brain images were automatically segmented into cortical plate, cerebral mantle, deep gray nuclei, and ventricles. Volumes were compared between IMVM and control subjects. Surfaces were extracted from the segmentations for local mean surface curvature measurement on the inner cortical plate and the ventricles. Linear models were estimated for age-related and ventricular volume-associated changes in local curvature in both the inner cortical plate and ventricles. While ventricular volume was enlarged in IMVM, all other tissue volumes were not different from the control group. Ventricles increased in curvature with age along the atrium and anterior body. Increasing ventricular volume was associated with reduced curvature over most of the ventricular surface. The cortical plate changed in curvature with age at multiple sites of primary sulcal formation. Reduced cortical folding was detected near the parieto-occipital sulcus in IMVM subjects. While tissue volume appears to be preserved in brains with IMVM, cortical folding may be affected in regions where ventricles are dilated.     

Different patterns of cerebellar abnormality and hypomyelination between POLR3A and POLR3B mutations

Background

Mutations of POLR3A and POLR3B have been reported to cause several allelic hypomyelinating disorders, including hypomyelination with hypogonadotropic hypogonadism and hypodontia (4H syndrome). Patients and methods: To clarify the difference in MRI between the two genotypes, we reviewed MRI in three patients with POLR3B mutations, and three with POLR3A mutations. Results: Though small cerebellar hemispheres and vermis are common MRI findings with both types of mutations, MRI in patients with POLR3B mutations revealed smaller cerebellar structures, especially vermis, than those in POLR3A mutations. MRI also showed milder hypomyelination in patients with POLR3B mutations than those with POLR3A mutations, which might explain milder clinical manifestations. Conclusions: MRI findings are distinct between patients with POLR3A and 3B mutations, and can provide important clues for the diagnosis, as these patients sometimes have no clinical symptoms suggesting 4H syndrome.