Biomedical subjects

Thomas J Eluvathingal

Publications and source records attributed to Thomas J Eluvathingal.

4 recordsLinked to original sources

PubMed2006

Diffusion tensor imaging-based tissue segmentation: validation and application to the developing child and adolescent brain.

We present and validate a novel diffusion tensor imaging (DTI) approach for segmenting the human whole-brain into partitions representing grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF). The approach utilizes the contrast among tissue types in the DTI anisotropy vs. diffusivity rotational invariant space. The DTI-based whole-brain GM and WM fractions (GMf and WMf) are contrasted with the fractions obtained from conventional magnetic resonance imaging (cMRI) tissue segmentation (or clustering) methods that utilized dual echo (proton density-weighted (PDw)), and spin-spin relaxation-weighted (T2w) contrast, in addition to spin-lattice relaxation weighted (T1w) contrasts acquired in the same imaging session and covering the same volume. In addition to good correspondence with cMRI estimates of brain volume, the DTI-based segmentation approach accurately depicts expected age vs. WM and GM volume-to-total intracranial brain volume percentage trends on the rapidly developing brains of a cohort of 29 children (6-18 years). This approach promises to extend DTI utility to both micro and macrostructural aspects of tissue organization.

Adolescent↗

PubMed2006

Diffusion tensor imaging of the corticospinal tract following cerebral hemispherectomy.

Following cerebral hemispherectomy, the corticospinal tract is believed to undergo reorganizational changes, which can induce enhanced function of the contralateral motor pathway and mediate partial recovery of motor function. The aim of this study was to use diffusion tensor imaging to investigate the effects of hemispherectomy on the corticospinal tract, with particular attention to the corticospinal tract contralateral to the resection. Diffusion tensor imaging would presumably detect microstructural abnormalities through quantitative measurements of the fiber tract integrity and orientation. Four patients with anatomic hemispherectomy and three patients with subtotal hemispherectomy were examined and compared with age-matched normal controls. Apparent diffusion coefficient and fractional anisotropy values were measured in regions along the corticospinal tract: internal capsule, cerebral peduncle, rostral pons, midpons, and caudal pons. None of the patients with anatomic hemispherectomy or subtotal hemispherectomy showed significant changes in either apparent diffusion coefficient or fractional anisotropy values in the corticospinal tract contralateral to the resected hemisphere, whereas increased apparent diffusion coefficient and decreased fractional anisotropy were observed in the ipsilateral rostral pons, midpons, and caudal pons of all patients with anatomic hemispherectomy, as well as in the ipsilateral cerebral peduncle of one patient with subtotal hemispherectomy. Increased apparent diffusion coefficient values were also noted in the ipsilateral internal capsule of the same patient. This study revealed no evidence of significant reinforcement of the contralateral corticospinal tract in patients with hemispherectomy, at least from diffusion tensor imaging measurements, but suggests that wallerian degeneration most likely occurs in the ipsilateral motor pathway.

Adolescent↗

PubMed2006

Cerebellar lesions in tuberous sclerosis complex: neurobehavioral and neuroimaging correlates.

We assessed the structural and functional imaging features of cerebellar lesions and their neurobehavioral correlates in a large cohort of patients with tuberous sclerosis complex. A consecutive series of 78 patients with tuberous sclerosis complex underwent magnetic resonance imaging (MRI) and positron emission tomography (PET) studies with [(18)F]fluorodeoxyglucose (FDG) and alpha-[(11)C]methyl-l-tryptophan (AMT) as part of their evaluation for epilepsy surgery. Neurobehavioral assessment included the Gilliam Autism Rating Scales (GARS) and the Vineland Adaptive Behavior Scales (VABS). Twenty-one patients (27%) had cerebellar lesions (10 boys; mean age 9 +/- 8 years; 9 had right-sided, 10 had left-sided, and 2 had bilateral cerebellar lesions). The lesions showed decreased glucose metabolism (0.79 +/- 0.10) and increased (1.04 +/- 0.10) AMT uptake compared with the normal (nonlesional) cerebellar cortex. Comparisons between patients with (n = 20) and without (n = 57) a cerebellar lesion on neurobehavioral functioning, controlling for the number and location of cortical tubers, revealed that the cerebellar lesion group had higher overall autistic symptomatology. Within-group analyses of the cerebellar lesion group revealed that children with right-sided cerebellar lesions had higher social isolation and communicative and developmental disturbance compared with children with left-sided cerebellar lesions. The side of the cerebellar lesion was not related to adaptive behavior functioning. These findings provide additional empiric support for a role of the cerebellum in autistic symptomatology. Further investigation of the potential role of the right cerebellum in autism, particularly with regard to the dentatothalamofrontal circuit, is warranted.

Adolescent↗

PubMed2006

Abnormal brain connectivity in children after early severe socioemotional deprivation: a diffusion tensor imaging study.

OBJECTIVES: We previously reported that children who were subjected to early socioemotional deprivation in Romanian orphanages showed glucose hypometabolism in limbic and paralimbic structures, including the orbital frontal gyrus, infralimbic prefrontal cortex, hippocampus/amygdala, lateral temporal cortex, and the brainstem. The present study used diffusion tensor imaging tractography to examine the integrity of white matter tracts that connect these brain regions. METHODS: Fractional anisotropy and apparent diffusion coefficient for uncinate fasciculus, stria terminalis, fornix, and cingulum were measured in 7 right-handed children (5 girls and 2 boys; mean age: 9.7 +/- 2.6 years) with a history of early severe socioemotional deprivation in Eastern European orphanages and compared with similar measurements in 7 right-handed normal children (4 girls and 3 boys; mean age: 10.7 +/- 2.8 years). RESULTS: Neuropsychological assessment of the orphans verified the relatively mild specific cognitive impairment and impulsivity consistent with previous studies of children who were adopted from Romanian orphanages. Fractional anisotropy values in the left uncinate fasciculus were decreased significantly in the early deprivation group compared with control subjects. Apparent diffusion coefficient values for the early deprivation group tended to be greater than that in control subjects in all of the tracts measured, without reaching statistical significance. CONCLUSION: Our study demonstrates in children who experienced socioemotional deprivation a structural change in the left uncinate fasciculus that partly may underlie the cognitive, socioemotional, and behavioral difficulties that commonly are observed in these children.

Brain↗