Quantitative diffusion tensor imaging in cerebral palsy due to periventricular white matter injury

Abstract

Periventricular white matter injury (PWI) is a major form of brain injury observed in congenital hemiparesis. The aim of this study is to determine the usefulness of diffusion tensor imaging (DTI) and fibre tracking in delineating the primary and secondary degenerative changes in cerebral white matter and deep grey matter in patients with spastic cerebral palsy due to PWI and to look for any possible reorganization of the axonal architecture. Five hemiparetic cerebral palsy patients (median age 14 years) with known PWI were prospectively studied with DTI of the brain at 1.5T and quantitatively compared with five age and sex matched controls. Fibre tracts for various corticofugal, thalamocortical and association tracts were generated and analysed for the DTI fibre count and for diffusion parameters. A region of interest based analysis was performed for the directionally averaged mean diffusivity (D(av)) and fractional anisotropy (FA) values in various white matter locations in the brain and the brainstem and in the deep grey matter nuclei. Group statistics were performed for these parameters using Mann-Whitney U-test comparing the affected sides in patients with either side in controls and the unaffected side in hemiparetics. There was significant reduction in DTI fibre count on the lesional side involving corticospinal tract (CST), corticobulbar tract (CBT) and superior thalamic radiation in the patient group compared with controls. Also there was an increase in DTI fibre count in the unaffected side of the hemiparetic patients in CST and CBT, which reached statistical significance only in CBT. The corpus callosum, cingulum, superior longitudinal fasciculus and middle cerebellar peduncle failed to show any significant change. ROI measurements on the primary site of white matter lesion and the thalamus revealed a significant increase in D(av) and decrease in FA, suggesting primary degeneration. The CST in the brainstem, the body of corpus callosum and the head of caudate and lentiform nuclei showed features of secondary degeneration on the affected side. The CST on the unaffected side of hemiparetics was found to have a significant decrease in D(av) and an increase in FA. Thus the degeneration of various motor and sensory pathways, as well as deep grey matter structures, appears to be important in determining the pathophysiological mechanisms in patients with congenital PWI. Also evidence suggesting the reorganization of sensorimotor tracts in the unaffected side of spastic hemiparetic patients was noted.

Track density imaging (TDI): Validation of super resolution property

“…The basic idea of counting tracks has been around in diffusion MRI for several years (e.g., (Behrens et al, 2003;Roberts et al, 2005;Thomas et al, 2005)). These earlier studies used track-density quantification to estimate the probability of connection between regions, as a tool to parcellate brain structures from probabilistic tractography results, or as a summary parameter to characterise fibre bundles for intra-and inter-subject quantitative analysis.…”

Relation between neuroradiological findings and upper limb function in hemiplegic cerebral palsy

“…On the other hand, some authors showed by diffusion tensor MRI that apart from corticospinal tract damage, children with a periventricular lesion also had involvement of thalamocortical pathways. 32,33 Interestingly, recent imaging studies suggest that motor and sensory reorganization may be mediated by different forms of neuroplasticity. 30,34 Interhemispheric reorganization differences may account for the different levels of sensory and motor outcomes.…”

Diffusion Tensor Imaging in Children with Periventricular Leukomalacia: Variability of Injuries to White Matter Tracts

“…One of the definite advantages of DTI is the possibility of quantitative measurement of tract diameters and tract-specific DTI parameters 27,29,36,57,58 that will be attempted as a complementary study to the present one. However, one potential problem foreseen in these cases and previously discussed is partial volume effects due to the small brain size.…”

“…[19][20][21] Results have provided further understanding of pathogenesis and treatment in a range of neurologic disorders by providing visualization of specific white matter fiber tracts (see review by Horsfield and Jones 22 ). [23][24][25][26][27] Although injury to the corticospinal tracts is thought to be the major determinant of motor impairment in children with PVL, recent studies have shown that sensory pathways, including the posterior thalamic radiation, may be affected instead or, concurrently, 28 indicative of the complexity of white matter involvement in PVL. 29,30 Criteria for DTI-based identification of various white matter tracts at 26 locations were established and applied to 24 children with CP associated with PVL as well as in a group of 35 unaffected controls to further elucidate the diversity of white matter tract injury involvement in PVL.…”