Cecilia Parazzini

Demonstration of acute ischemic lesions in the fetal brain by diffusion magnetic resonance imaging

The possibility of detecting acute hypoxic‐ischemic brain lesions by prenatal magnetic resonance imaging or ultrasound is low. We present a case of a fetus with a vein of Galen arteriovenous malformation in whom prenatal diffusion‐weighted magnetic resonance imaging at 33 weeks of gestation clearly detected cerebral acute ischemic lesions, associated with remarkable decrease of the average apparent diffusion coefficient, whereas T2‐weighted imaging was still not informative.

Early Cerebral Lesions in Cytomegalovirus Infection: Prenatal MR Imaging

PURPOSE To assess the diagnostic and prognostic value of fetal cerebral magnetic resonance (MR) imaging of congenital cytomegalovirus (CMV) infection in comparison with that of level II ultrasonography (US). MATERIALS AND METHODS Institutional review board approval and informed consent for fetal MR imaging and data collection were obtained. Thirty-eight fetuses with CMV infection, examined by using serial level II US, underwent fetal MR imaging (mean gestational age, 25 weeks; age range at first fetal MR examination, 20-34 weeks). The frequency of pathologic findings at US (29 cases with transabdominal examination and nine cases with both transabdominal and transvaginal examination) and MR imaging was calculated, and a comparison between techniques by considering number (paired Student t test) and type (McNemar test) of finding was made. A comparison (paired Student t test) in cases of repeated fetal (nine of 38) and/or postnatal (14 of 38) MR imaging was obtained. Diagnostic and prognostic sensitivity was calculated for both techniques. RESULTS US and MR imaging findings were both normal in 47% of cases (18 of 38). Abnormal studies were reported in 26% (10 of 38) of US and 53% (20 of 38) of MR imaging cases. In 47% of cases (18 of 38), MR imaging provided additional information (P = .0002). MR imaging had better results than US in detecting polar temporal lesions (P = .0001), microencephaly (P = .03), and cortical anomalies (P = .06). In 44.5% of cases (four of nine), the second fetal MR examination results showed new findings (P = .05). In 79% of cases, postnatal MR imaging results confirmed prenatal findings (P = .08). MR imaging had higher sensitivity than US in detecting brain anomalies (92% vs 38%) and in predicting symptomatic infection (83% vs 33%). US and MR imaging revealed low positive predictive values (29% vs 36%). CONCLUSION Fetal MR imaging results can show abnormalities in the fetal brain after CMV infection, even when US results are normal. The early detection of some brain abnormalities, such as microencephaly and cortical anomalies, may substantially influence the prognosis of fetal infection.

Magnetic resonance imaging assessment of brain maturation in preterm neonates with punctate white matter lesions

IntroductionEarly white matter (WM) injury affects brain maturation in preterm infants as revealed by diffusion tensor imaging and volumetric magnetic resonance (MR) imaging at term postmenstrual age (PMA). The aim of the study was to assess quantitatively brain maturation in preterm infants with and without milder forms of WM damage (punctate WM lesions, PWML) using conventional MRI.MethodsBrain development was quantitatively assessed using a previously validated scoring system (total maturation score, TMS) which utilizes four parameters (progressive myelination and cortical infolding, progressive involution of glial cell migration bands and germinal matrix tissue). PWML were defined as foci of increased signal on T1-weighted images and decreased signal on T2-weighted images with no evidence of cystic degeneration. A group of 22 preterm infants with PWML at term PMA (PWML group) were compared with 22 matched controls with a normal MR appearance.ResultsThe two groups were comparable concerning gestational age, birth weight and PMA. TMS was significantly lower in the PWML group than in the control group (mean TMS 12.44 ± 2.31 vs 14.00 ± 1.44; P = 0.011). Myelination (mean 2.76 ± 0.42 PWML group vs 3.32 ± 0.55 control group, P = 0.003) and cortical folding (3.64 ± 0.79 vs 4.09 ± 0.43, P = 0.027) appeared to be significantly delayed in babies with PWML.ConclusionConventional MRI appears able to quantify morphological changes in brain maturation of preterm babies with PWML; delayed myelination and reduced cortical infolding seem to be the most significant aspects.

Patterns of damage in the mature neonatal brain

Patterns of damage in the mature neonatal brain can be subdivided into focal, multifocal and diffuse. The main cause of diffuse brain damage in the term newborn is hypoxic–ischaemic encephalopathy (HIE). HIE is still the major recognized perinatal cause of neurological morbidity in full-term newborns. MRI offers today the highest sensitivity in detecting acute anoxic injury of the neonatal brain. Conventional acquisition techniques together with modern diffusion techniques can identify typical patterns of HIE injury, even in the early course of the disease. However, even though highly suggestive, these patterns cannot be considered as pathognomonic. Perinatal metabolic disease such as kernicterus and severe hypoglycaemia should be differentiated from classic HIE. Other conditions, such as infections, non-accidental injury and rarer metabolic diseases can be misinterpreted as HIE in their early course when diffuse brain swelling is still the predominant MRI feature. Diffusion techniques can help to differentiate different types of diffuse brain oedema. Typical examples of focal injuries are arterial or venous infarctions. In arterial infarction, diffusion techniques can define more precisely than conventional imaging the extent of focal infarction, even in the hyperacute phase. Moreover, diffusion techniques provide quantitative data of acute corticospinal tract injury, especially at the level of the cerebral peduncles. Venous infarction should be suspected in every case of unexplained cerebral haematoma in the full-term newborn. In the presence of spontaneous bleeding, venous structures should always be evaluated by MR angiography.

Magnetic resonance imaging of fetal cerebellar development.

In the last few years fetal magnetic resonance imaging (MRI) has been proposed as a second level technique in the evaluation of fetal brain anomalies. It has been demonstrated that MRI is highly accurate in illustrating the morphologic changes of developing brain and fetal brain abnormalities being a useful procedure when ultrasonography is inconclusive or doubtful. Starting from the 19–20 weeks gestational age (GA), MRI can reliably depict fetal brain anatomy and locating pathology, offering a robust and reliable tool in the assessment of fetal CNS diseases. In this review bothin vivo MRI quantitative and qualitative data about fetal cerebellar development are presented and compared with ultrasonography data. Fetal cerebellar development is gradual, steady, and largely comparable to the development of the supratentorial brain. Archicerebellar (flocculo-nodular lobe) and paleocerebellar (vermis) structures develop first, whereas neocerebellum (cerebellar hemispheres) develop slowly and largely after birth.

Association of syndromic mental retardation with an Xq12q13.1 duplication encompassing the oligophrenin 1 gene

OPHN1 mutations cause a syndromic form of mental retardation (MR) characterized by cerebellar hypoplasia, early hypotonia, motor and speech delay, with occasional seizures and strabismus. Here we report on a familial chromosome duplication spanning about 800 Kb of Xq12q13.1, associated with MR and a distinctive phenotype in the affected male, but not in his heterozygous mother. The parents were healthy and non‐consanguineous with a history of three pregnancies. The first resulted in the birth of a boy with MR, motor impairment and seizures. The second pregnancy was terminated because of trisomy 18. At the time of the third, the first affected boy was analyzed by array‐CGH, which revealed a 800 Kb duplication at Xq12q13.1, encompassing three genes, including OPHN1. This mutation was inherited from his healthy mother and was not present in any of the three maternal brothers. To our knowledge this is the first report of a clinical phenotype associated with duplication of Xq12q13.

Consensus Paper: Radiological Biomarkers of Cerebellar Diseases

Hereditary and sporadic cerebellar ataxias represent a vast and still growing group of diseases whose diagnosis and differentiation cannot only rely on clinical evaluation. Brain imaging including magnetic resonance (MR) and nuclear medicine techniques allows for characterization of structural and functional abnormalities underlying symptomatic ataxias. These methods thus constitute a potential source of radiological biomarkers, which could be used to identify these diseases and differentiate subgroups of them, and to assess their severity and their evolution. Such biomarkers mainly comprise qualitative and quantitative data obtained from MR including proton spectroscopy, diffusion imaging, tractography, voxel-based morphometry, functional imaging during task execution or in a resting state, and from SPETC and PET with several radiotracers. In the current article, we aim to illustrate briefly some applications of these neuroimaging tools to evaluation of cerebellar disorders such as inherited cerebellar ataxia, fetal developmental malformations, and immune-mediated cerebellar diseases and of neurodegenerative or early-developing diseases, such as dementia and autism in which cerebellar involvement is an emerging feature. Although these radiological biomarkers appear promising and helpful to better understand ataxia-related anatomical and physiological impairments, to date, very few of them have turned out to be specific for a given ataxia with atrophy of the cerebellar system being the main and the most usual alteration being observed. Consequently, much remains to be done to establish sensitivity, specificity, and reproducibility of available MR and nuclear medicine features as diagnostic, progression and surrogate biomarkers in clinical routine.

Is fetal magnetic resonance imaging indicated when ultrasound isolated mild ventriculomegaly is present in pregnancies with no risk factors?: Role of MR in fetuses with mild isolated ventriculomegaly on US

Ventriculomegaly (VM) is the most common brain anomaly in prenatal ultrasound (US) diagnosis. There is a general trend to perform fetal magnetic resonance imaging (MRI) when VM is severe (greater than 15 mm) and/or it is not isolated. The role of MRI is debated when VM is borderline (between 10 and 15 mm) and isolated. Some authors have subdivided borderline VM into mild (10 to 12 mm) and moderate (>12 to15 mm). The aim of the study was to evaluate the role of MR in the imaging protocol of fetal cases characterized by mild isolated VM and no risk factors.

Prenatal magnetic resonance imaging of optic nerve head coloboma

Congenital optic nerve head coloboma represents an important cause of childhood visual impairment and blindness; it can be isolated or, more often, it can be associated with several syndromes. Ultrasound has limitations in depicting the posterior aspect of the fetal eye globe, so prenatal information about ocular coloboma are very scarce. The purpose of this paper was to report prenatal magnetic resonance (MR) imaging features of optic nerve head coloboma.

Deep Medullary Vein Involvement in Neonates with Brain Damage: An MR Imaging Study

These investigators report a new finding that may lead to the development of periventricular leukomalacia in premature infants. They analyzed conventional T1 and T2 images in 21 babies who showed areas of low T2 signal corresponding to the deep medullary veins. These abnormalities were found in association with cavities or cysts and, when followed, about 25% of patients developed typical MRI indications of periventricular leukomalacia. The authors suggest these findings may be related to venous thrombosis or engorgement and precede the onset of periventricular leukomalacia. BACKGROUND AND PURPOSE: Different and specific MR imaging patterns of lesions involving WM are widely defined in neonatal encephalopathy. The aim of this study was to describe a novel MR imaging pattern of damage characterized by the abnormal prominence of DMVs in premature and full-term neonates. MATERIALS AND METHODS: Twenty-one (11 premature and 10 full-term) neonates with MR imaging evidence of linear radially oriented fan-shaped lesions in the periventricular WM and without dural venous thrombosis were enrolled in this retrospective study. A total of 37 MR imaging examinations were performed at ages ranging from day 0 to 24 months. RESULTS: According to the appearance of linear anomalies on T2-weighted images, we identified 2 main patterns: T2 hypointense lesions without WM cavitations and T2 hypointense lesions associated with linear cysts. The first pattern was found in 17 examinations performed between 0 and 44 days of life; the second pattern was found in another 14 examinations performed between 6 days and 4 months of life. Five examinations performed between 9 and 24 months of life showed a reduction in volume and hyperintense signal intensity of the periventricular WM on T2-weighted and FLAIR images. CONCLUSIONS: Subtle linear WM lesions with the same anatomic distribution of DMVs may be evident in premature and full-term neonates without signs of major venous thrombosis, both in the acute and subacute phases. Their appearance and evolution suggest that transient DMV engorgement/thrombosis may be responsible for WM damage that can lead to a PVL-like pattern.