The aim was to survey the range of cerebral injury and abnormalities of cerebral development in infants born between 23 and 30 weeks' gestation using serial MRI scans of the brain from birth, and to ...correlate those findings with neurodevelopmental outcome after 18 months corrected age.
Between January 1997 and November 2000, consecutive infants born at < 30 weeks' gestational age underwent serial MRI brain scans from birth until term-equivalent age. Infants were monitored after 18 months of age, corrected for prematurity, with the Griffiths Mental Development Scales and neurologic assessment.
A total of 327 MRI scans were obtained from 119 surviving infants born at 23 to 30 weeks of gestation. Four infants had major destructive brain lesions, and tissue loss was seen at term for the 2 survivors. Fifty-one infants had early hemorrhage; 50% of infants with term scans after intraventricular hemorrhage had ventricular dilation. Twenty-six infants had punctate white matter lesions on early scans; these persisted for 33% of infants assessed at term. Early scans showed cerebellar hemorrhagic lesions for 8 infants and basal ganglia abnormalities for 17. At term, 53% of infants without previous hemorrhage had ventricular dilation and 80% of infants had diffuse excessive high signal intensity within the white matter on T2-weighted scans. Complete follow-up data were available for 66% of infants. Adverse outcomes were associated with major destructive lesions, diffuse excessive high signal intensity within the white matter, cerebellar hemorrhage, and ventricular dilation after intraventricular hemorrhage but not with punctate white matter lesions, hemorrhage, or ventricular dilation without intraventricular hemorrhage.
Diffuse white matter abnormalities and post-hemorrhagic ventricular dilation are common at term and seem to correlate with reduced developmental quotients. Early lesions, except for cerebellar hemorrhage and major destructive lesions, do not show clear relationships with outcomes.
To compare findings on hard copies of cranial ultrasound (US) and magnetic resonance imaging (MRI) obtained between birth and term in a group of preterm infants.
Infants born at or below a ...gestational age of 30 weeks who underwent cranial US scan and MRI on the same day were eligible for this study. Infants underwent, whenever possible, 3 scans between birth and term. We calculated the predictive probability (PP) of US findings as a predictor of findings on MRI.
Sixty-two paired MRI and US studies were performed between birth and term in 32 infants born at a median gestational age of 27 (range: 23-30) weeks and a median birth weight of 918 (530-1710) grams. US predicted some MRI findings accurately: germinal layer hemorrhage (GLH) on US had a PP of 0.8 with a 95% confidence interval of (0.70-0.90) for the presence of GLH on MRI, intraventricular hemorrhage (IVH) on US had a PP of 0.85 (0.76-0.94) for the presence of IVH on MRI, and severe white matter (WM) echogenicity on US had a PP of 0.96 (0.92-1.0) for the presence of WM hemorrhagic parenchymal infarction on MRI. Other MRI changes were less well-predicted: mild or no WM echogenicity on US had a PP of 0.54 (0.41-0.66) for the presence of normal WM signal intensity on MRI, and moderate or severe WM echogenicity on US had a PP of 0.54 (0.42-0.66) for the presence of small petechial WM hemorrhage and/or diffuse excessive high-signal intensity (DEHSI) in the WM on T2-weighted images on MRI. However, mild/moderate or severe WM echogenicity on US scans performed at >/=7 days after birth had a PP of 0.72 (0.58-0.87) for the presence of WM hemorrhage and/or DEHSI on MRI. There were no cases of cystic periventricular leukomalacia.
US accurately predicted the presence of GLH, IVH, and hemorrhagic parenchymal infarction on MRI. However, its ability to predict the presence of DEHSI and small petechial hemorrhages in the WM on T2 weighted images is not as good, but improves on scans performed at >/=7 days after birth. In addition, normal WM echogenicity on US is not a good predictor of normal WM signal intensity on MRI.
To define magnetic resonance imaging (MRI) appearances of the brain in extremely preterm infants between birth and term, a sequential cohort of infants born at a gestational age <30 weeks was studied ...with a dedicated neonatal magnetic resonance scanner. Images of infants (n = 41) with a median gestational age of 27 weeks (range 23 to 29 weeks) were initially obtained at a median age of 2 days (range 1 to 20 days) and then repeatedly studied; 29 (71%) infants had MRI at a median gestational age of 43 weeks (range 38 to 52 weeks) (term MRI). On the initial MRI scan 28 of 41 infants had abnormalities: either intraventricular hemorrhage, germinal layer hemorrhage, ventricular dilatation, or diffuse and excessive high signal intensity in the white matter on T
2 -weighted images. When magnetic resonance images for preterm infants at term gestation were compared with those of infants in the control group born at term, 22 of 29 infants had dilatation of the lateral ventricles, 24 of 29 had squaring of the anterior or posterior horns of the lateral ventricles, 11 of 29 had a widened interhemispheric fissure or extracerebral space, and 22 of 29 had diffuse and excessive high signal intensity in the white matter. There were no cases of cystic periventricular leukomalacia. We conclude that MRI abnormalities are commonly seen in the brain of preterm infants on whom images are obtained within 48 hours of birth and that further abnormalities develop between birth and term. A characteristic appearance of diffuse and excessive high signal intensity in the white matter on T
2 -weighted images is associated with the development of cerebral atrophy and may be a sign of white matter disease. These MRI appearances may help account for the high incidence of neurodevelopmental impairment in extremely preterm infants. (J Pediatr 1999;135:351-7)
MR imaging was performed in very preterm infants by using an MR imager in the neonatal intensive care unit. The aims of this study were to assess the development of myelination in the preterm brain ...based on MR imaging findings and to compare the ability of T1-weighted conventional spin-echo, inversion recovery fast spin-echo, and T2-weighted fast spin-echo MR imaging to show myelination in these infants.
MR imaging was performed for 26 preterm infants with a median gestational age of 28 weeks who had normal neurodevelopmental outcomes at 2 years corrected age.
Myelin was evident in the gracile and cuneate nuclei and fasciculi, vestibular nuclei, cerebellar vermis, inferior and superior cerebellar peduncles, dentate nucleus, medial longitudinal fasciculus, medial geniculate bodies, subthalamic nuclei, inferior olivary nuclei, ventrolateral nuclei of the thalamus, decussation of the superior cerebellar peduncles, medial lemnisci, lateral lemnisci, and inferior colliculi at < or = 28 weeks gestational age. From this gestational age, myelination was not visualized at any new site until 36 weeks gestational age, when myelin was visualized in the corona radiata, posterior limb of the internal capsule, corticospinal tracts of the precentral and postcentral gyri, and lateral geniculate bodies. T2-weighted fast spin-echo MR imaging showed myelin in gray matter nuclei at an earlier gestational age than did T1-weighted conventional spin-echo or inversion recovery fast spin-echo MR imaging. T1-weighted conventional spin-echo MR imaging showed myelin earlier in some white matter tracts in the preterm brain.
Myelination was evident in numerous gray and white matter structures in the very preterm brain. A knowledge of myelination milestones will allow delays to be detected at an early stage.
To investigate preterm infants, we have installed in our neonatal intensive care unit a dedicated magnetic resonance (MR) imaging system which was specifically designed for neonatal use. The aim of ...this study was to describe the MR appearances of the brain in preterm infants who were first scanned between 25 and 32 weeks gestational age (GA) and to outline changes to the brains of these infants between their first scan and term.
Preterm infants of 25 to 32 weeks GA were imaged using the 1T neonatal MR system (Oxford Magnet Technology, Eyensham, Oxfordshire, England/Picker International, Cleveland, OH). The scanning protocol included T1-weighted conventional spin echo (repetition time TR, 600; echo time, 20 ms), inversion recovery fast spin echo (TR, 3530; effective echo time, 30; inversion time, 950 ms), and T2-weighted fast spin echo (TR, 3500; effective echo time, 208 ms) sequences.
Seventeen infants of median 28 weeks GA (range, 24 to 31 weeks) at birth were imaged a total of 53 times between birth and term. The median number of images per infant was two (range, 1 to 9). In infants of < 30 weeks GA, the germinal matrix was visualized at the margins of the lateral ventricles. It had a short T1 and short T2 and the bulk of it involuted at between 30 and 32 weeks GA. The white matter had a relatively homogeneous low signal except for bands of altered signal (probably originating from regions containing radial glia and migrating cells) which were most apparent anterolateral and posterolateral to the lateral ventricles. Myelination was seen in the posterior brainstem, cerebellum, and region of the ventrolateral nuclei of the thalamus. Infants had very little cortical folding at 25 weeks GA but this developed later in an orderly fashion.
The neonatal MR system allowed extremely preterm infants to be studied safely with MR imaging. The images acquired demonstrated the germinal matrix, early myelination, and early cortical folding. Evolution of these features was demonstrated with serial studies.
Objective: The Hammersmith Infant Neurological Examination was performed in a cohort of 74 preterm infants whose gestational age ranged between 24 and 30.5 weeks. The infants were examined between 9 ...and 18 months' chronologic age (6-15 months' corrected age) and scored with the optimality score system previously standardized in a cohort of low-risk term infants. The aim of the study was to establish the frequency distribution of the optimality scores in this cohort and to establish whether the scores can predict locomotor function at 2 years of age. Results: The results showed that this standardized neurologic examination can be performed in preterm infants as early as 9 months' chronologic age to predict motor outcome at 2 years old. The scores showed no significant association with the degree of prematurity or the age of assessment. Conclusion: This examination should be particularly useful in very premature infants who are at high risk of severe neurologic and developmental disabilities and for whom the early prediction of motor function can be difficult. (J Pediatr 2002;140:57-60)
MR imaging can now be used safely in extremely preterm infants. The aim of this study was to compare the MR imaging appearance of the immature brain with neuropathologic findings at postmortem ...examination.
Seven extremely sick preterm infants, born at a median of 24 weeks' gestation, were studied using T1- and T2-weighted MR sequences. Infants died at a median of 3 days after initial MR imaging, and postmortem examinations were carried out.
The cortex and germinal matrix were seen as areas of low signal intensity on T2-weighted images, which corresponded to their highly cellular histologic appearance. The periventricular and subcortical layers of white matter had a high signal intensity, corresponding to high fiber and relatively low cellular density; the intermediate layer of low signal intensity corresponded to a dense band of migrating cells. Regions of acute hemorrhage were seen as low signal intensity and regions of infarction as high signal intensity on T2-weighted images. One infant with mild periventricular leukomalacia had some low signal intensity on T1-weighted images, but no focal changes on T2-weighted images. Regions of neuronal mineralization, seen in association with infarction and capillary proliferation, within the basal ganglia and thalami were characterized by very low signal intensity on T2-weighted images and by very high signal intensity on T1-weighted images. There were no imaging abnormalities detected in regions with more subtle histologic abnormalities, such as increased glial or apoptotic cells.
MR imaging can be used to observe normal developing brain anatomy in extremely premature infants; it can detect areas of hemorrhage and infarction within the developing brain, but conventional MR imaging may not detect more subtle histologic abnormalities.
Noninvasive diagnosis of intestinal necrosis is important in planning surgery in preterm infants with necrotizing enterocolitis (NEC). We aimed to assess the potential of magnetic resonance imaging ...(MRI) for the diagnosis of intestinal necrosis.
Abdominal MRI scans were performed in a group of preterm infants with suspected NEC and compared with surgical findings and to MRI results in a group of control infants. In addition, MRI was performed in 2 preterm infants with suspected NEC who did not require surgery.
Six infants with a median birth weight of 1220 g (range, 760-1770 g) and median gestational age at birth of 30 weeks (range, 28-34 weeks) were studied at a median postnatal age of 10 days (range, 4-19 days). Four infants had a bubble-like appearance in part of the intestinal wall, intramural gas, and an abnormal fluid level within bowel lumen. At surgery, NEC was found in 5 infants and sigmoid volvulus in 1. The site of the bubble-like appearance corresponded to the site of intestinal necrosis at surgery. Four control infants with a median birth weight of 1500 g (range, 730-2130 g) and a median gestational age of 31 weeks (range, 26-36 weeks) had abdominal MRI at a median postnatal age of 8 days (range, 4-70 days). None of the above findings were seen in any control infant. The bubble-like appearance was not seen in the 2 infants with suspected NEC who did not require surgery.
Abdominal MRI allows the noninvasive diagnosis of bowel necrosis. This may aid the timing of surgical intervention in preterm infants with a clinical diagnosis of NEC.gangrene, ischemia, MRI, necrotizing enterocolitis.
Aim: This study looked for evidence of physiological disturbance in preterm infants undergoing magnetic resonance imaging (MRI).
Methods: Intensive care was continued, as appropriate, throughout ...scanning in each infant. The heart rate, oxygen saturation (SaO
2), temperature and mean arterial blood pressure (BP) was monitored during MRI in preterm infants, median gestational age at birth 27 (range 23–32) weeks and median postnatal age at initial MRI, 3 days (range 1–42). The acoustic noise level during imaging was also measured.
Results: 2087 min of data were obtained from 39 examinations in 23 infants. The median heart rate was 159 and no bradycardia <100 or tachycardia >200 bpm occurred. Although 42 episodes of desaturation <90% were detected only three were <80, and these occurred in one infant due to endotracheal tube blockage. The median axillary temperature was 36.9°C (range 35.7–37.8) and median BP (
n=6) was 37 mmHg (24–48). The ambient noise level in the MR system during scanning was 67–72 dBA.
Conclusion: In preterm infants who required intensive care during scanning, MRI could be performed without major physiological instability.
The 1 Tesla MRI system allows easy access to infants for monitoring and treatment during scanning and may be of value in detecting and monitoring abnormalities of the brain during a period of rapid ...growth and when infants are particularly vulnerable to cerebral injury.
