Biomedical subjects

Olga Kapellou

Publications and source records attributed to Olga Kapellou.

6 recordsLinked to original sources

PubMed2006

Abnormal deep grey matter development following preterm birth detected using deformation-based morphometry.

Preterm birth is a leading risk factor for neurodevelopmental and cognitive impairment in childhood and adolescence. The most common known cerebral abnormality among preterm infants at term equivalent age is a diffuse white matter abnormality seen on magnetic resonance (MR) images. It occurs with a similar prevalence to subsequent impairment, but its effect on developing neural systems is unknown. MR images were obtained at term equivalent age from 62 infants born at 24-33 completed weeks gestation and 12 term born controls. Tissue damage was quantified using diffusion-weighted imaging, and deformation-based morphometry was used to make a non-subjective survey of the whole brain to identify significant cerebral morphological alterations associated with preterm birth and with diffuse white matter injury. Preterm infants at term equivalent age had reduced thalamic and lentiform volumes without evidence of acute injury in these regions (t = 5.81, P < 0.05), and these alterations were more marked with increasing prematurity (t = 7.13, P < 0.05 for infants born at less than 28 weeks) and in infants with diffuse white matter injury (t = 6.43, P < 0.05). The identification of deep grey matter growth failure in association with diffuse white matter injury suggests that white matter injury is not an isolated phenomenon, but rather, it is associated with the maldevelopment of remote structures. This could be mediated by a disturbance to corticothalamic connectivity during a critical period in cerebral development. Deformation-based morphometry is a powerful tool for modelling the developing brain in health and disease, and can be used to test putative aetiological factors for injury.

Adolescent↗

PubMed2006

Abnormal cortical development after premature birth shown by altered allometric scaling of brain growth.

BACKGROUND: We postulated that during ontogenesis cortical surface area and cerebral volume are related by a scaling law whose exponent gives a quantitative measure of cortical development. We used this approach to investigate the hypothesis that premature termination of the intrauterine environment by preterm birth reduces cortical development in a dose-dependent manner, providing a neural substrate for functional impairment. METHODS AND FINDINGS: We analyzed 274 magnetic resonance images that recorded brain growth from 23 to 48 wk of gestation in 113 extremely preterm infants born at 22 to 29 wk of gestation, 63 of whom underwent neurodevelopmental assessment at a median age of 2 y. Cortical surface area was related to cerebral volume by a scaling law with an exponent of 1.29 (95% confidence interval, 1.25-1.33), which was proportional to later neurodevelopmental impairment. Increasing prematurity and male gender were associated with a lower scaling exponent (p < 0.0001) independent of intrauterine or postnatal somatic growth. CONCLUSIONS: Human brain growth obeys an allometric scaling relation that is disrupted by preterm birth in a dose-dependent, sexually dimorphic fashion that directly parallels the incidence of neurodevelopmental impairments in preterm infants. This result focuses attention on brain growth and cortical development during the weeks following preterm delivery as a neural substrate for neurodevelopmental impairment after premature delivery.

Biometry↗

PubMed2006

Axial and radial diffusivity in preterm infants who have diffuse white matter changes on magnetic resonance imaging at term-equivalent age.

OBJECTIVE: Diffuse excessive high signal intensity (DEHSI) is observed in the majority of preterm infants at term-equivalent age on conventional MRI, and diffusion-weighted imaging has shown that apparent diffusion coefficient values are elevated in the white matter (WM) in DEHSI. Our aim was to obtain diffusion tensor imaging on preterm infants at term-equivalent age and term control infants to test the hypothesis that radial diffusivity was significantly different in the WM in preterm infants with DEHSI compared with both preterm infants with normal-appearing WM on conventional MRI and term control infants. METHODS: Diffusion tensor imaging was obtained on 38 preterm infants at term-equivalent age and 8 term control infants. Values for axial (lambda1) and radial [(lambda2 + lambda3)/2] diffusivity were calculated in regions of interest positioned in the central WM at the level of the centrum semiovale, frontal WM, posterior periventricular WM, occipital WM, anterior and posterior portions of the posterior limb of the internal capsule, and the genu and splenium of the corpus callosum. RESULTS: Radial diffusivity was elevated significantly in the posterior portion of the posterior limb of the internal capsule and the splenium of the corpus callosum, and both axial and radial diffusivity were elevated significantly in the WM at the level of the centrum semiovale, the frontal WM, the periventricular WM, and the occipital WM in preterm infants with DEHSI compared with preterm infants with normal-appearing WM and term control infants. There was no significant difference between term control infants and preterm infants with normal-appearing WM in any region studied. CONCLUSIONS: These findings suggest that DEHSI represents an oligodendrocyte and/or axonal abnormality that is widespread throughout the cerebral WM.

Brain↗

PubMed2005

Can clinical signs identify newborns with neuromuscular disorders?

OBJECTIVE: To evaluate retrospectively the prevalence of neuromuscular disorders in 83 newborns referred to a tertiary care center because of hypotonia and weakness and/or contractures, with a possible diagnosis of neuromuscular disorder. We also aimed to establish whether clinical signs could help to identify infants with neuromuscular disorders. STUDY DESIGN: Sixty-six of the 83 infants who fulfilled the inclusion criteria (79.5%) had an identifiable disorder, which was a neuromuscular disorder in 39 (46.9%). RESULTS: Absent or extremely reduced antigravity movements were mainly found in infants with neuromuscular disorders (sensitivity and specificity 97.4% and 75%), whereas partial range antigravity movements were more frequent in infants with other diagnosis. Contractures were mainly found in infants with peripheral nerve or muscle involvement but also were relatively frequent in infants with genetic or metabolic syndromes (sensitivity 69.2%, specificity 61.3%). Reduced fetal movements and abnormal liquor were frequent but not present consistently in infants with neuromuscular disorders (sensitivity 46.1% and 38.4%) and were found rarely in infants with other disorders (specificity 88.6% and 75.0%). CONCLUSIONS: Severe muscle weakness and contractures are the most reliable indicators of a neuromuscular disorder and should be carefully assessed in an infant with neonatal hypotonia.

Algorithms↗

PubMed2004

Diffusion-weighted magnetic resonance imaging in term perinatal brain injury: a comparison with site of lesion and time from birth.

OBJECTIVE: The aim of this study was to establish a more objective method for confirming tissue injury in term neonates who present with early seizures that are believed to be hypoxic-ischemic in origin. METHODS: We studied the relationship between contemporaneous diffusion-weighted magnetic resonance imaging and conventional magnetic resonance imaging in 63 symptomatic term-born neonates and 15 control term infants performed in the neonatal period. Apparent diffusion coefficients (ADC) were obtained for multiple regions of the brain. RESULTS: ADC values in the 15 control infants were 1 (1-1.15) (median [range]) x 10(-3)/mm2/second in the thalami and 1.1 (1-1.3) x 10(-3)/mm2/second in the lentiform nuclei, 1.5 (1.3-1.7) x 10(-3)/mm2/second in the centrum semiovale, 1.6 (1.46-1.7) x 10(-3)/mm2/second in the anterior white matter (WM), and 1.55 (1.35-1.85) x 10(-3)/mm2/second in the posterior WM with little variation over time. ADC values were significantly reduced in the first week after severe injury to either WM or basal ganglia and thalami (BGT), but values normalized at the end of the first week and then increased during week 2. ADC values were either normal or increased in moderate BGT and WM lesions when compared with controls. ADC values < 1.1 x 10(-3)/mm2/second were always associated with WM infarction and values <0.8 x 10(-3)/mm2/second with thalamic infarction. CONCLUSION: A reduced ADC soon after delivery allows the presence of tissue infarction to be confirmed at a time when conventional imaging changes may be subtle. However, as both moderate WM and BGT lesions may have normal or increased ADC values, a normal ADC value during the first week does not signify normal tissue. ADC values should always be measured in combination with visual analysis of both conventional and diffusion-weighed images for maximum detection of pathologic tissue, and the timing of the scan needs to be taken into account when interpreting the results.

Brain↗

PubMed2003

Diffusion-weighted imaging of the brain in preterm infants with focal and diffuse white matter abnormality.

OBJECTIVE: The most common finding on magnetic resonance imaging (MRI) of the brain in preterm infants at term-equivalent age is diffuse excessive high signal intensity (DEHSI) in the white matter. It is unclear whether DEHSI represents a biological abnormality. This study used diffusion-weighted imaging (DWI) to compare apparent diffusion coefficient (ADC) values in DEHSI with infants with normal imaging and those with overt brain damage to determine whether DEHSI shows the diffusion characteristics of normal or abnormal tissue. METHODS: MRI, using conventional and diffusion-weighted imaging (DWI), was performed in 50 preterm infants at term-equivalent age using a 1.5 Tesla MR scanner. The infants were divided into 3 groups on the basis of their MRI results: 1) normal white matter, 2) DEHSI, or 3) overt white matter pathology. ADC values were measured in the frontal, central, and posterior white matter at the level of the centrum semiovale. ADC values in the 3 groups of preterm infants were compared using a 1-way analysis of variance with a Bonferroni test for multiple comparisons. RESULTS: ADC values were significantly higher in infants with DEHSI and infants with overt white matter pathology than in infants with normal white matter. There was no significant difference between ADC values in infants with DEHSI and those with overt white matter pathology. CONCLUSIONS: This study provides objective evidence that DEHSI represents diffuse white matter abnormality.

Body Water↗