Cerebellar cleft: a form of prenatal cerebellar disruption

In contrast to malformations, cerebellar disruptions have attracted little interest in the literature. We draw attention for the first time to the hypothesis that cerebellar clefts are residual changes following a prenatal cerebellar insult, and represent disruptions. We reviewed the clinical records and MR findings of six patients with a cerebellar cleft, two of whom also had prenatal MRI at 24 weeks of gestation. The clefts were located in the left cerebellar hemisphere in five cases, in the right in one patient. Other typical findings included disorderly alignment of the cerebellar folia and fissures, irregular gray/white matter junction, and abnormal arborization of the white matter in all patients. The cerebellar cleft extended into the fourth ventricle in three cases, and in two children cystic cortical lesions were seen. Supratentorial schizencephaly was found in two patients. In two patients there was a documented fetal cerebellar hemorrhage at 24 weeks of gestation. We conclude that cerebellar clefts are residual changes resulting from a prenatal cerebellar insult and consequently represent disruptions rather than primary malformations. The supratentorial findings are also in agreement with an acquired lesion. The outcome in these children was variable, mainly depending of the presence of supratentorial lesions.

Assessment of brain growth in early childhood using deformation-based morphometry

We present methods for the quantitative analysis of brain growth based on the registration of longitudinal MR image data with the use of Jacobian determinant maps to characterise neuroanatomical changes. The individual anatomies, growth maps and tissue classes are also spatially normalised in an 'average space' and aggregated to provide atlases for the population at each timepoint. The average space representation is obtained using the average intersubject transformation within each timepoint. In an exemplar study, this approach is used to assess brain development in 25 infants between 1 and 2 years, and we show consistency in growth estimates between registration and segmentation approaches.

Cranial ultrasound in metabolic disorders presenting in the neonatal period: characteristic features and comparison with MR imaging

BACKGROUND AND PURPOSE

Brain imaging is an integral part of the diagnostic work-up for metabolic disorders, and the bedside availability of cranial ultrasonography (cUS) allows very early brain imaging in symptomatic neonates. Our aim was to investigate the role and range of abnormalities seen on cUS in neonates presenting with metabolic disorders. A secondary aim, when possible, was to address the question of whether brain MR imaging is more informative by comparing cUS to MR imaging findings.

MATERIALS AND METHODS

Neonates with a metabolic disorder who had at least 1 cUS scan were eligible. cUS images were reviewed for anatomic and maturation features, cysts, calcium, and other abnormalities. When an MR imaging scan had been obtained, both sets of images were compared.

RESULTS

Fifty-five infants (35 also had MR imaging) were studied. The most frequent findings were in oxidative phosphorylation disorders (21 cUS and 12 MR imaging): ventricular dilation (11 cUS and 6 MR imaging), germinolytic cysts (GLCs; 7 cUS and 5 MR imaging), and abnormal white matter (7 cUS and 6 MR imaging); in peroxisomal biogenesis disorders (13 cUS and 9 MR imaging): GLCs (10 cUS and 6 MR imaging), ventricular dilation (10 cUS and 5 MR imaging), abnormal cortical folding (8 cUS and 7 MR imaging), and lenticulostriate vasculopathy (8 cUS); in amino acid metabolism and urea cycle disorders (14 cUS and 11 MR imaging): abnormal cortical folding (9 cUS and 4 MR imaging), abnormal white matter (8 cUS and 8 MR imaging), and hypoplasia of the corpus callosum (7 cUS and 6 MR imaging); in organic acid disorders (4 cUS and 2 MR imaging): periventricular white matter echogenicity (2 cUS and 1 MR imaging); and in other disorders (3 cUS and 1 MR imaging): ventricular dilation (2 cUS and 1 MR imaging). cUS findings were consistent with MR imaging findings. cUS was better for visualizing GLCs and calcification. MR imaging was more sensitive for subtle tissue signal intensity changes in the white matter and abnormality in areas difficult to visualize with cUS, though abnormalities of cortical folding suggestive of polymicrogyria were seen on cUS.

CONCLUSION

A wide range of abnormalities is seen using cUS in neonatal metabolic disorders. cUS is a reliable bedside tool for early detection of cysts, calcium, structural brain abnormalities, and white matter echogenicity, all suggestive of metabolic disorders.

Postmortem brain MRI with selective tissue biopsy as an adjunct to autopsy following neonatal encephalopathy

Following the death of a neonate it is essential that parents are given full and accurate information about the probable cause of death. Perinatal autopsy often adds new information or may even change the presumed diagnosis [Cartlidge PH, Dawson AT, Stewart JH, Vujanic GM. Value and quality of perinatal and infant postmortem examinations: cohort analysis of 400 consecutive deaths. Br Med J 1995;310(6973):155-8; Khong TY. Falling neonatal autopsy rates. Br Med J 2002;324(7340):749-50] informing decisions regarding the management of any future pregnancy. Autopsy can be considered the "gold standard" for the identification of antecedent events leading to a neonatal death. However, recent events in the UK have added to an already declining rate in neonatal autopsies [Brodlie M, Laing IA. Ten years of neonatal autopsies in tertiary referral centre: retrospective study. Br Med J 2002;324(7340):761-3]. To try and redress this balance the Chief Medical Officer has recommended that research should be commissioned into the use of non-invasive imaging to provide a similar standard of information [The Chief Medical Officer. The removal, retention and use of human organs and tissues from post mortem examination. London, England: The Stationary Office, Department of Health; 2001]. Previous publications on postmortem MRI have focused largely on investigation of the foetus and of still birth [Griffiths PD, Variend D, Evans M, Jones A, Wilkinson ID, Paley MNJ, et al. Postmortem MR imaging of the fetal and stillborn central nervous system. Am J Neuroradiol 2003;24(1):22-7; Whitby EH, Paley MN, Cohen M, GriffithsPD. Postmortem MR imaging of the fetus: an adjunct or a replacement for conventional autopsy? Semin Fetal Neonatal Med 2005;10(5):475-83]. We report our experience on the use of postmortem brain MRI combined with selective tissue biopsy, in six neonatal deaths in the setting of a large district general hospital.

Prediction of specific absorption rate in mother and fetus associated with MRI examinations during pregnancy

There is uncertainty regarding the risk posed by magnetic resonance imaging (MRI) examinations to pregnant patients. The most frequently used methods, such as single-shot fast spin echo (ssFSE), often require operation at the specific absorption rate (SAR) limits imposed by safety guidelines. With the introduction of higher-field systems, such limits will be even more significant for fetal imaging. An electromagnetic solver based on the time domain finite integration technique (FIT) was used to predict SAR in an anatomically realistic model of a pregnant patient (28 weeks' gestation) associated with the radiofrequency (RF) fields from birdcage body coils typical of 1.5 T and 3 T MRI systems (i.e., operating at approximately 64 and 127 MHz, respectively). The results suggest that 1) the highest local SAR is in the mother, with the fetus being exposed to a peak of approximately 40-60% of that value at 64 MHz, increasing to approximately 50-70% at 127 MHz; 2) compliance with U.S. Food and Drug Administration (FDA) and International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines requires control of SAR values averaged over 1 g or 10 g of tissue, respectively; and 3) compliance with Medical Device Agency (MDA) guidelines requires control of the maximum SAR(10g) within the fetus.

Magnetic resonance imaging of preterm brain injury

Magnetic resonance imaging (MRI) has proved to be a valuable tool for monitoring development and pathology in the preterm brain. This imaging modality is useful for assessing numerous pathologies including periventricular leukomalacia, intraventricular haemorrhage/germinal layer haemorrhage, and periventricular haemorrhagic infarction, and can help to predict outcome in these infants. MRI has also allowed the detection of posterior fossa lesions, which are not easily seen with ultrasound. Additionally, and perhaps most relevant, quantitative MR studies have shown differences between the normal appearing preterm brain at term equivalent age and term born infants, confirming that the brain develops differently in the ex utero environment. Further studies using quantifiable MR techniques will improve our understanding of the effects of the ex utero environment, including aspects of neonatal intensive care on the developing brain.

Intrauterine T-cell activation and increased proinflammatory cytokine concentrations in preterm infants with cerebral lesions

Brain injury is common in very preterm infants, and intrauterine infection is a frequent antecedent of preterm birth. We examined the relation of cerebral damage to intrauterine antigen exposure and inflammation in 50 infants who were born at 23-29 weeks' gestation. Higher concentrations of cytokines (tumour necrosis factor alpha [TNF-alpha], and interleukins [IL], 1beta, 6, and 10) and CD45RO(+) T lymphocytes in umbilical blood predicted cerebral lesions detected by magnetic resonance imaging very soon after delivery. Our results suggest that infants who mount an immune response in utero are at higher risk of cerebral lesions.

How to perform diffusion-weighted imaging

Diffusion-weighted imaging (DWI) has become an invaluable tool in the management of patients with stroke. DWI relies on detecting the random diffusion of water molecules. In normal tissues this movement may be restricted by the presence of cellular structures, which provide a barrier to free movement. This occurs in myelinated white matter, where movement is restricted more across than along fibres. This directional dependence is termed anisotropic restricted diffusion. The diffusion of water molecules can be made the dominant contrast mechanism within an image by applying large magnetic field gradients. The pulsed gradient spin echo (PGSE) sequence provides sensitivity to diffusion with gradient pulses either side of the 180 degrees refocusing pulse. This sequence is generally heavily T2 weighted. In order to detect normal anisotropic properties within the different components of the medullary core, association, commissural and projection fibres, DWI must be performed with sensitisation in at least three directions. PGSE sequences have been used to obtain the diffusion coefficient (D*), a measure of mobility at the molecular level within tissue. In acute infarction D* is increased; in brain death it is decreased. Diffusion contrast needs to be optimised in relation to the highly T2-dependent nature of PGSE sequences. This also requires a more detailed knowledge of how D* changes in disease, but information on nonischaemic neurological conditions is still very limited.

Diffusion-weighted imaging in neonates

Diffusion-weighted imaging (DWI) can readily be performed in the neonate, although currently studies remain a few years behind-those carried out on adults. DWI relies on the random diffusion of water molecules. As for the adult population, a pulsed gradient spin echo sequence (PGSE) with cardiac gating can be used to exploit the effect of diffusion on image contrast and to determine the apparent diffusion coefficient (D*) for tissues or fluids. Anisotropic properties caused by the restriction of the movement of water molecules may be demonstrated. In the neonatal brain restricted motion can be detected in both myelinated and unmyelinated white matter tracts. DWI has been used to study changes in global and focal ischaemic injury to the neonatal brain. A decreased D* may be documented after an ischaemic insult followed by a gradual increase. These changes are consistent with animal data but show a slower time course. Intervention following perinatal ischaemic injury must be started within hours. DWI detects early ischaemic injury and may therefore be a useful tool for identifying those infants who could benefit from intervention.

Comparison of findings on cranial ultrasound and magnetic resonance imaging in preterm infants

OBJECTIVE

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.

PARTICIPANTS AND METHODS

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.

RESULTS

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.

CONCLUSION

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.

Diffusion-weighted imaging of the brain in neonates and infants

Diffusion-weighted imaging provides novel and interesting insights into normal development and pathologic processes occurring in neonates and infants. Both myelinated and unmyelinated white matter show restricted diffusion. Focal infarction in perinatal stroke and more global injury associated with hypoxic ischemia encephalopathy produce high-signal lesions in the brain, in the acute phase. Diffusion-weighted imaging also demonstrates abnormalities of a variety of other diseases, when conventional imaging is relatively uninformative.

Pilot study of treatment with whole body hypothermia for neonatal encephalopathy

BACKGROUND

There is extensive experimental evidence to support the investigation of treatment with mild hypothermia after birth asphyxia. However, clinical studies have been delayed by the difficulty in predicting long-term outcome very soon after birth and by concern about adverse effects of hypothermia.

OBJECTIVES

The objectives of this study were to determine whether it is feasible to select infants with a bad neurological prognosis and to begin hypothermic therapy within 6 hours of birth, and to observe the effect of this therapy on relevant physiologic variables.

METHODS

Sixteen newborn infants with clinical features of birth asphyxia (median cord blood pH: 6.74; range: 6.58-7.08) were assessed by amplitude integrated electroencephalography (aEEG), and mild whole body hypothermia was instituted within 6 hours of birth in the 10 infants with an aEEG prognostic of a bad outcome. Rectal temperature was maintained at 33.2 +/- (standard deviation).6 degrees C for 48 hours. Rectal and tympanic membrane temperature, blood pressure, heart rate, blood gases, blood lactate, full blood count, blood electrolytes, high and low shear rate viscosity, and coagulation studies were monitored during and after cooling. A preliminary assessment of neurological outcome was made by repeated magnetic resonance imaging (MRI) and neurological examination.

RESULTS

All infants selected to receive hypothermia developed convulsions and a severe encephalopathy. During 48 hours of hypothermia infants had prolonged metabolic acidosis (median pH: 7.30; base excess: -6.3 mmol x L(-1), a high blood lactate (median lactate: 5.3 mmol x L(-1)) and low blood potassium levels (median value: 3.9 mmol x L(-1)) x Hypothermia was associated with lower heart rate and higher mean blood pressure. However, these changes did not seem to be clinically relevant and no significant complication of hypothermia was encountered. Blood viscosity and coagulation studies were similar during and after cooling. Unusual MRI findings were noted in 3 infants: transverse sinus thrombosis with subsequent small cerebellar infarct; probable thrombosis in the straight sinus; and hemorrhagic cerebral infarction. Six of the 10 cooled infants had minor abnormalities only or normal follow-up neurological examination; 3 infants died and 1 had major abnormalities. None of the 6 infants with a normal aEEG developed severe neonatal encephalopathy or neurological sequel.

CONCLUSIONS

After birth asphyxia infants can be objectively selected by aEEG and hypothermia started within 6 hours of birth in infants at high risk of developing severe neonatal encephalopathy. Prolonged mild hypothermia to 33 degrees C to 34 degrees C is associated with minor physiologic abnormalities. Further studies of both the safety and efficacy of mild hypothermia, including further neuroimaging studies, are warranted.

Reduced development of cerebral cortex in extremely preterm infants

Most growth in cortical connections and complexity occurs after 25 weeks. The cerebral cortex of extremely preterm infants when imaged at gestational age 38-42 weeks had less cortical surface area and was less complex than in normal infants born around term (p<0.0148 and p<0.0002, respectively), despite similar term-corrected cerebral tissue volumes. Since deficits acquired during critical periods of brain development may be permanent, these results suggest a neural substrate for the neurocognitive impairment that is frequent among such preterm infants.

Head growth in infants with hypoxic-ischemic encephalopathy: correlation with neonatal magnetic resonance imaging

OBJECTIVES

The aims of the study were to establish the relationship between head growth in the first year of life with the pattern on injury on neonatal magnetic resonance imaging (MRI) in infants with hypoxic-ischemic encephalopathy (HIE) and to relate these to the neurodevelopmental outcome.

METHODS

Fifty-two term infants who presented at birth with a neonatal encephalopathy consistent with HIE and who had neonatal brain MRI were entered into the study. Head circumference charts were evaluated retrospectively and the head growth over the first year of life compared with the pattern of brain lesions on MRI and with the neurodevelopmental outcome at 1 year of age. Suboptimal head growth was classified as a drop of >2 standard deviations across the percentiles with or without the development of microcephaly, which was classified as a head circumference below the third percentile.

RESULTS

There was no statistical difference between the neonatal head circumferences of the infants presenting with HIE and control infants. At 12 months, microcephaly was present in 48% of the infants with HIE, compared with 3% of the controls. Suboptimal head growth was documented in 53% of the infants with HIE, compared with 3% of the controls. Suboptimal head growth was significantly associated with the pattern of brain lesions, in particular to involvement of severe white matter and to severe basal ganglia and thalamic lesions. Suboptimal head growth predicted abnormal neurodevelopmental outcome with a sensitivity of 79% and a specificity of 78%, compared with the presence of microcephaly at 1 year of age, which had a sensitivity of only 65% and a specificity of 73%. The exceptions were explained by infants with only moderate white matter abnormalities who had suboptimal head growth but normal outcome at 1 year of age and by infants with moderate basal ganglia and thalamic lesions only who had normal head growth but significant motor abnormality.

Magnetic resonance imaging of the brain in a cohort of extremely preterm infants

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.

Relationship between MR imaging and histopathologic findings of the brain in extremely sick preterm infants

BACKGROUND AND PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Reproducibility and accuracy of MR imaging of the brain after severe birth asphyxia

BACKGROUND AND PURPOSE

MR imaging of the brain can be used to detect cerebral damage after suspected hypoxic-ischemic injury. This study examines the reproducibility and accuracy of MR imaging soon after severe birth asphyxia.

METHODS

During a 48-month period, full-term newborn neonates, who died within the first week as a result of severe hypoxic ischemic encephalopathy, were included in the study if they had undergone early (<5 days old) MR imaging and postmortem neuropathologic studies. Two trained observers assessed reproducibility by examining multiple brain regions independently with current criteria and then defining and applying improved criteria. Accuracy of MR findings was tested by comparing the brain regions about which the two imaging raters agreed to those regions about which the two pathologists agreed.

RESULTS

Eight neonates, with a median gestational age of 40 weeks (range, 38-40 weeks) and who suffered severe birth asphyxia, were included in the study. In the reproducibility study, MR imaging agreement was moderate when current criteria were used (k = .44). Using the improved criteria, agreement increased considerably (k = .62). Much of this improvement was due to limiting the analyses to the posterior limb of the internal capsule, thalamus, parietal cortex, hippocampus, and medulla. The posterior limb of the internal capsule was the most reliable region analyzed. MR imaging agreement was similar to that achieved by two experienced pathologists reviewing the histologic sections (k = .66). In the accuracy study, MR imaging abnormality was predictive of pathologic abnormality with a sensitivity of .79 and a positive predictive value of 1.0. The predictive value of a single MR imaging abnormality was .79 (95% confidence interval, .61-.96).

CONCLUSION

Criteria that provide substantial reproducibility and accuracy for the interpretation of MR imaging findings very early after birth asphyxia can be derived.

Periventricular haemorrhagic infarct in a preterm neonate

Magnetic resonance imaging (MRI) was performed on an infant born, at 28 weeks gestational age who suffered a sudden episode of bradycardia and desaturation on the 3rd day of life. Imaging demonstrated bilateral germinal layer haemorrhage and intraventricular haemorrhage, with parenchymal involvement in a fan-shaped pattern in the periventricular white matter on the left. These appearances are consistent with a combination of intravascular thrombi and perivascular haemorrhage along the course of the medullary veins. We believe that this is the first report of the MRI appearance of an acute periventricular haemorrhagic infarct associated with a germinal layer haemorrhage/intraventricular haemorrhage in a preterm neonate.

Persistent increases in cerebral lactate concentration after birth asphyxia

In this prospective study proton magnetic resonance spectroscopy (1H MRS) was used to test the hypothesis that lactate can be detected later than 1 mo after birth in the brains of infants who display severe neurodevelopmental impairment 1 y after transient perinatal hypoxia-ischemia. Data were obtained from three groups of infants: 1) eight infants suffering birth asphyxia followed by perinatal encephalopathy and abnormal neurodevelopmental outcome at 1 y of age (defined as major neurologic impairment, Griffiths quotient <85%, and low optimality score); 2) 10 infants with signs of perinatal hypoxia-ischemia but normal neurodevelopmental outcome at 1 y; and 3) six control infants with uneventful perinatal courses and normal neurodevelopment at 1 y. Between one and four examinations (median 1) were performed at median (range) 11 (4-68) wk after birth, and the cerebral concentration ratio of lactate to creatine plus phosphocreatine (Cr) calculated from each spectrum. Lactate was detected later than the 1st mo after birth in seven of eight infants with abnormal neurodevelopmental outcome [maximum detected lactate/Cr was median (range) 0.44 (0.24-0.67)]. No lactate was detected later than the 1st mo after birth in infants with normal neurodevelopmental outcome, nor in five of six control subjects, although a small amount of lactate was detected in one control infant (lactate/Cr=0.04). These results suggest that the pathologic postasphyxial process, indicated by persistent cerebral lactate, may not be confined to the period immediately after injury.

Abnormal magnetic resonance signal in the internal capsule predicts poor neurodevelopmental outcome in infants with hypoxic-ischemic encephalopathy

OBJECTIVE

The aim of this study was to establish whether abnormal signal intensity in the posterior limb of the internal capsule (PLIC) on magnetic resonance imaging is an accurate predictor of neurodevelopmental outcome at 1 year of age in infants with hypoxic-ischemic encephalopathy (HIE).

METHODS

We have examined 73 term neonates with HIE between 1 and 17 days after birth with cranial magnetic resonance imaging and related the magnetic resonance imaging findings to neurodevelopmental outcome at 1 year of age.

RESULTS

All infants with an abnormal signal intensity in the PLIC developed neurodevelopmental impairment although in 4 infants with very early scans the abnormal signal was not apparent until up to 4 days after birth. A normal signal intensity was associated with a normal outcome in all but 4 cases; 3 of these infants had minor impairments and all had persistent imaging changes within the white matter. The 4th infant with a normal signal intensity on day 2 died before a further image could be obtained. The absence of normal signal predicted abnormal outcome in term infants with HIE with a sensitivity of 0.90, a specificity of 1.0, a positive predictive value of 1.0, and a negative predictive value of 0.87. The test correctly predicted outcome in 93% of infants with grade II HIE, according to the Sarnat system. Applying a Bayesian approach, the predictive probability of the test (the probability that the test would predict an outcome correctly) was distributed with a mean of 0.94 and 95% confidence limits of 0.89 to 1.0.

CONCLUSION

Abnormal signal intensity in the PLIC is an accurate predictor of neurodevelopmental outcome in term infants suffering HIE.

Magnetic resonance imaging of the brain in very preterm infants: visualization of the germinal matrix, early myelination, and cortical folding

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Detection of subtle changes in the brains of infants and children via subvoxel registration and subtraction of serial MR images

PURPOSE

To compare conventional two-dimensional multisection images with registered three-dimensional volume and subtraction images for detecting subtle changes in the brains of infants and children.

METHODS

Twenty-six patients (24 with hemorrhagic/ischemic lesions) and one each with perinatal infection and Sturge-Weber disease were examined on two or more occasions with conventional multisection T1- and T2-weighted sequences as well as with 3-D T1-weighted volume sequences. A registration program was used to match the volume images to subvoxel dimensions, and subtracted images (second volume set minus the first) were obtained. The multisection images were compared with the 3-D and subtracted images and graded for detection of changes in a variety of brain structures.

RESULTS

In 16% to 33% of comparisons of different structures, the multisection images and the 3-D registered and subtracted images showed changes equally well. The 3-D registered and subtracted images were better than the multisection images in 67% to 84% of comparisons for detection of changes in the cerebral hemispheres, ventricles, brain stem, cerebellum, and in lesions. Statistically significant differences were found between the graded performance of the registered 3-D images and the conventional 2-D images in detecting cerebral infarction and hypoxic ischemic encephalopathy. In the late phase following neonatal cerebral infarction (1 to 11 months), the 3-D registered and subtracted images revealed growth of the brain at the margins of the lesions.

CONCLUSION

Subvoxel registration of serial MR images may be of value in detecting subtle changes in the brains of infants and children.