MRI = Excellent soft tissue contrast of macroscopic anatomy of the brain, but conventional MRI may not always demonstrate microstructural development and disease processes. DTI is a MR technique that provides a quantitative measure of water diffusion in tissue. DTI has the potential to reveal subtle white matter abnormalities that are not demonstrated on conventional MRI and so may be useful in investigating white matter development and pathology in the preterm brain. DTI is essentially similar to DWI, but more directions of diffusion sensitization are measured to enable anisotropy to be calculated more accurately than the three directions used in DW imaging.
1. 70% of all genes are expressed in the brain. 2. To assay brain connectivity in both structural and functional level, has unique potential as a tool for characterising functional genetics in neural circuitry. 3. Imaging genetics typically involves first identifying a meaningful variation in the DNA sequence, such as the William Syndrome,
The image on th eleft is from the paper by Behrens et al. and shows thalamo-cortical projections in the adult. Colours are different, but here purple represents fronto-temporal, orange = motor, blue = somatosensory and yellow = parieto/occipital cortex. The central image is of an infant with no abnormality on MRI and is broadly similar to the adult. The image on the right is the infant with lesions. Connections appear diminished, more so on the ipsilateral side to the porencephalic cyst. Could not visualise connections from the sensory cortex on the side. The frontal/temporal cortex appears to connect to the region of the mediodorsal nucleus, the occipital/parietal cortex projects to the region of the pulvinar. Connections from the motor region project to the ventrolateral nuclei and those from the somatosensory region connect to the ventral posterior nucleus.
Distribution of probability that MRI examination of the posterior limb of the internal capsule will correctly assign neurodevelopmental prognosis after neonatal encephalopathy Predictive probability = 94% (95% CI 89-99%) ( density curve: Rutherford et al Pediatrics 1998;102:323-328)
Diffusion weighted image (Cowan et al Neuropediatrics 1994;25:172-175)
24 weeks gestation Term (Battin et al Lancet 1997;349:1741)
The commonest ‘lesion’ in preterm infants at term: Diffuse Excessive High Signal Intensity on T2 weighted images (DEHSI) (Maalouf et al J Pediatr 1999;135:351) DEHSI
Insulae to Lingula Superior frontal to medial orbital Superior frontal to anterior orbital Brain regions where connections are strongest in young adults Robinson et al, in progress Caudate to Substantia Nigra Postcentral to Superior Frontal
Thalamus to thalamus Posterior cingulate to pallidum Brain regions where connections are strongest in older adults Robinson et al, in progress Thalamus to putamen Thalamus to insula
Future uses of MRI in Neonatal Medicine <ul><li>Diagnose serious brain pathology </li></ul><ul><li>Assign prognosis </li></ul><ul><li>Understand brain growth and development </li></ul><ul><li>Investigate brain function </li></ul><ul><li>In clinical trials of neuroprotectants </li></ul>
References <ul><li>Ancel P.Y, Livinec F., Larroque B, Marret S, Arnaud C, Pierrat V, Dehan M, N'Guyen S, Escande B, Burguet A, Thiriez G, Picaud J-C, André M, Bréart G, Kaminski M and the EPIPAGE Study Group. Cerebral palsy among very preterm children in relation to gestational age and neonatal ultrasound abnormalities: The EPIPAGE Cohort Study. Paediatrics, 2006; 117: 828-835 </li></ul><ul><li>de Vries L. S. , Inge-Lot C, Van Haastert PPT, MA, Karin J. Radermaker K.J, Koopman C and Groenendaal F. Ultrasound abnormalities preceeding cerebral palsy in high risk preterm infants. Journal of Pediatrics, 2004; 144: 815-20 </li></ul><ul><li>O’Shea MT, Kuban CK, Allred NE, Paneth N, Pagano M, Dammann O, Bostic L Brooklier K, McQuiston S, Miller A, Pasternak S, Plesha-Troyke S, Price J, Romano E, Solomon K.M, Jacobson A, Westra S, Leviton A and for the Extremely Low Gestational Age Newborns Study Investigators. Neonatal cranial ultrasound lesions and developmental delays at 2 years of age among extremely low gestational age children. Pediatrics, 2008; 122: 662-66916. </li></ul><ul><li>Woodward LJ, Anderson PJ, Austin NC, Howard K, Inder TE. Neonatal MRI to predict neurodevelopmental outcomes in preterm infants. N Engl J Med 2006; 355(7):685-694. </li></ul>