Fiber-tracking techniques can predict the degree of neurologic impairment for periventricular leukomalacia

Does motor deficit in children with cerebral palsy correlate with diffusion tensor metrics abnormalities in thalamocortical pathways?

Background

Cerebral palsy (CP) is a group of motor-impairment signs secondary to many disorders that interfere with early brain development and are usually related to white matter injury in children. Most studies are focused on the study of motor tracts, mainly the corticospinal tract (CST). Diffusion tensor imaging (DTI) is a reliable imaging modality providing an appropriate method of detection of white matter microstructure abnormalities. The purpose of this study is to investigate the relationship between DTI observed motor CST injury, sensory pathways (thalamic radiations) injury, and motor functions.

Results

This study shows significant involvement (reduction in DTI fiber count) of the superior thalamic radiation (in severe cases) with atrophy of the anterior thalamic radiations (ATR) or posterior thalamic radiations (PTR) in most cases with a significant reduction in fractional anisotropy (FA) and elevation in mean diffusivity (MD) values. In addition, the degree of motor affection shows a significant negative correlation with FA and a significant positive correlation with MD values. Diffusion tensor imaging shows a significant reduction in FA within the examined tracts between CP and control at the Rt CST, Lt CST, Rt corticothalamic radiation (CTR), and Lt CTR with significant cutoff values of ≤ 0.449, ≤ 0.472, ≤ 0.432, and ≤ 0.44, respectively.

Conclusions

This study demonstrates disruption of thalamocortical and corticospinal tracts in CP patients, which reflects that both sensory and motor tract affection have a valuable role in the pathophysiology of motor dysfunction in CP patients.

Comparison of fractional anisotropy and apparent diffusion coefficient among hypoxic ischemic encephalopathy stages 1, 2, and 3 and with nonasphyxiated newborns in 18 areas of brain

Purpose

To determine the area and extent of injury in hypoxic encephalopathy stages by diffusion tensor imaging (DTI) using parameters apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values and their comparison with controls without any evidence of asphyxia. To correlate the outcome of hypoxia severity clinically and significant changes on DTI parameter.

Materials and Methods

DTI was done in 50 cases at median age of 12 and 20 controls at median age of 7 days. FA and apparent diffusion coefficient (ADC) were measured in several regions of interest (ROI). Continuous variables were analyzed using Student's t-test. Categorical variables were compared by Fisher's exact test. Comparison among multiple groups was done using analysis of variance (ANOVA) and post hoc Bonferroni test.

Results

Abnormalities were more easily and accurately determined in ROI with the help of FA and ADC values. When compared with controls FA values were significantly decreased and ADC values were significantly increased in cases, in ROI including both right and left side of thalamus, basal ganglia, posterior limb of internal capsule, cerebral peduncle, corticospinal tracts, frontal, parietal, temporal, occipital with P value < 0.05. The extent of injury was maximum in stage-III. There was no significant difference among males and females.

Conclusion

Compared to conventional magnetic resonance imaging (MRI), the evaluation of FA and ADC values using DTI can determine the extent and severity of injury in hypoxic encephalopathy. It can be used for early determination of brain injury in these patients.

Structural network performance for early diagnosis of spastic cerebral palsy in periventricular white matter injury

Periventricular white matter injury (PWMI) is a common cause of spastic cerebral palsy (SCP). Diffusion tensor imaging (DTI) shows high sensitivity but moderate specificity for predicting SCP. The limited specificity may be due to the diverse and extensive brain injuries seen in infants with PWMI. We enrolled 72 infants with corrected age from 6 to 18 months in 3 groups: PWMI with SCP (n = 20), non-CP PWMI (n = 19), and control (n = 33) groups. We compared DTI-based brain network properties among the three groups and evaluated the diagnostic performance of brain network properties for SCP in PWMI infants. Our results show abnormal global parameters (reduced global and local efficiency, and increased shortest path length), and local parameters (reduced node efficiency) in the PWMI with SCP group. On logistic regression, the combined node efficiency of the bilateral precentral gyrus and right middle frontal gyrus had a high sensitivity (90%) and specificity (95%) for differentiating PWMI with SCP from non-CP PWMI, and significantly correlated with the Gross Motor Function Classification System scores. This study confirms that DTI-based brain network has great diagnostic performance for SCP in PWMI infants, and the combined node efficiency improves the diagnostic accuracy.

Specific White Matter Lesions Related to Motor Dysfunction in Spastic Cerebral Palsy: A Meta-analysis of Diffusion Tensor Imaging Studies

BACKGROUND

Assessing motor impairment in spastic cerebral palsy is a key factor in the treatment and rehabilitation of patients. We intend to investigate the correlation between diffusion tensor imaging properties of sensorimotor pathways and motor function in spastic cerebral palsy using meta-analysis, and to determine specific white matter lesions that are closely related to motor dysfunction in spastic cerebral palsy.

METHODS

We conducted a literature search of PubMed, Embase, Scopus, and Web of Science databases to identify trials published from January 1999 to January 2019 that had evaluated the correlation between fractional anisotropy and motor function scores in spastic cerebral palsy. Correlation coefficient (r) values were extracted for each study, and the extent of r was quantitatively explored. The r values between fractional anisotropy within different sensorimotor pathways and motor function scores were pooled respectively.

RESULTS

Nineteen studies involving 504 children with spastic cerebral palsy, were included. Fractional anisotropy in both sensory and motor pathways significantly correlated with motor function scores. However, compared with the corticospinal tract and thalamic radiation, fractional anisotropy in the posterior limb of the internal capsule correlated more strongly with gross motor function classification system and upper limb motor function (r = -0.71, 95% confidence interval [CI] -0.80 to -0.60; r = 0.73, 95% CI 0.60-0.82, respectively; P < .05).

CONCLUSIONS

Fractional anisotropy within the posterior limb of the internal capsule is more closely related to motor dysfunction and can potentially be a biomarker for evaluating the degree of motor impairment in spastic cerebral palsy.

Neuroplasticity in cerebral visual impairment (CVI): Assessing functional vision and the neurophysiological correlates of dorsal stream dysfunction

Cerebral visual impairment (CVI) results from perinatal injury to visual processing structures and pathways and is the most common individual cause of pediatric visual impairment and blindness in developed countries. While there is mounting evidence demonstrating extensive neuroplastic reorganization in early onset, profound ocular blindness, how the brain reorganizes in the setting of congenital damage to cerebral (i.e. retro-geniculate) visual pathways remains comparatively poorly understood. Individuals with CVI exhibit a wide range of visual deficits and, in particular, present with impairments of higher order visual spatial processing (referred to as "dorsal stream dysfunction") as well as object recognition (associated with processing along the ventral stream). In this review, we discuss the need for ongoing work to develop novel, neuroscience-inspired approaches to investigate functional visual deficits in this population. We also outline the role played by advanced structural and functional neuroimaging in helping to elucidate the underlying neurophysiology of CVI, and highlight key differences with regard to patterns of neural reorganization previously described in ocular blindness.

Motor Abilities in Adolescents Born Preterm Are Associated With Microstructure of the Corpus Callosum

Background: Preterm birth is associated with increased risk of neuromotor impairment. Rates of major neuromotor impairment (cerebral palsy) have decreased; however, in a large proportion of those who do not develop cerebral palsy impaired neuromotor function is observed and this often has implications for everyday life. The aim of this study was to investigate motor performance in preterm born adolescents without cerebral palsy, and to examine associations with alterations of motor system pathway structure. Design/Methods: Thirty-two adolescents (12 males) without cerebral palsy, born before 33 weeks of gestation (mean 27.4 weeks, SD 2.4; birth weight mean 1,084.5 g; SD 387.2), treated at a single tertiary unit, were assessed (median age 16 years; min 14, max 18). Timed performance and quality of movements were assessed with the Zürich Neuromotor Assessment. Neuroimaging included Diffusion Magnetic Resonance Imaging for tractography of the major motor tracts and measurement of fractional anisotropy as a measure of microstructure of the tracts along the major motor pathways. Separate analyses were conducted for areas with predominantly single and predominantly crossing fiber regions. Results: Motor performance in both tasks assessing timed performance and quality of movements, was poorer than expected in the preterm group in relation to norm population. The strongest significant correlations were seen between performance in tasks assessing movement quality and fractional anisotropy in corpus callosum fibers connecting primary motor, primary somatosensory and premotor areas. In addition, timed motor performance was significantly related to fractional anisotropy in the cortico-spinal and thalamo-cortical to premotor area fibers, and the corpus callosum. Conclusions: Impairments in motor abilities are present in preterm born adolescents without major neuromotor impairment and in the absence of focal brain injury. Altered microstructure of the corpus callosum microstructure appears a crucial factor, in particular for movement quality.

Characterisation of the Corticospinal Tract Using Diffusion Magnetic Resonance Imaging in Unilateral and Bilateral Cerebral Palsy Patients

Background

Neuroimaging is increasingly used to locate the lesion that causes cerebral palsy (CP) and its extent in the brains of CP patients. Conventional structural magnetic resonance imaging (MRI) does not indicate the connectional pattern of white matter; however, with the help of diffusion MRI, fibre tracking of white matter can be done.

Methods

We used diffusion MRI and probabilistic tractography to identify the putative white matter connectivity in the brains of 10 CP patients. We tracked the corticospinal tract (CST) of the patients’ upper and lower limbs and calculated the white matter connectivity, as indexed by streamlines representing the probability of connection of the CST.

Results

Our results show that diffusion MRI with probabilistic tractography, while having some relation with the clinical diagnosis of CP, reveals a high degree of individual variation in the streamlines representing the CST for upper and lower limbs.

Conclusion

Diffusion MRI with probabilistic tractography provides the state of connectivity from lesioned areas to other parts of the brain and is potentially beneficial to be used as an adjunct to the clinical management of CP, providing a means to monitor intervention outcomes.

Early Diagnosis of Spastic Cerebral Palsy in Infants with Periventricular White Matter Injury Using Diffusion Tensor Imaging

BACKGROUND AND PURPOSE

Periventricular white matter injury is the common cause of spastic cerebral palsy. However, the early diagnosis of spastic cerebral palsy still remains a challenge. Our aim was to investigate whether infants with periventricular white matter injury with bilateral spastic cerebral palsy have unique lesions different from those in infants without cerebral palsy and to evaluate the efficiency of DTI in the early diagnosis of spastic cerebral palsy.

MATERIALS AND METHODS

Infants with periventricular white matter injury and controls underwent MR imaging at 6-18 months of age. Fractional anisotropy was calculated from DTI. Cerebral palsy was diagnosed by 24-30 months of age. Subjects were divided into 3 groups: infants with periventricular white matter injury with bilateral spastic cerebral palsy, infants with periventricular white matter injury without cerebral palsy, and controls. Tract-Based Spatial Statistics and Automated Fiber Quantification were used to investigate intergroup differences. Receiver operating characteristic curves were used to assess the diagnostic accuracy of spastic cerebral palsy. Correlations between motor function scores and fractional anisotropy were evaluated along white matter tracts.

RESULTS

There were 20, 19, and 33 subjects in periventricular white matter injury with spastic cerebral palsy, periventricular white matter injury without cerebral palsy, and control groups, respectively. Decreased fractional anisotropy in the corticospinal tract was only observed in infants with periventricular white matter injury with spastic cerebral palsy, whereas decreased fractional anisotropy in the posterior thalamic radiation and genu and splenium of the corpus callosum was seen in both periventricular white matter injury subgroups. Fractional anisotropy in the corticospinal tract at the internal capsule level was effective in differentiating infants with periventricular white matter injury with spastic cerebral palsy from those without cerebral palsy by a threshold of 0.53, and it had strong correlations with motor function scores.

CONCLUSIONS

Corticospinal tract lesions play a crucial role in motor impairment related to spastic cerebral palsy in infants with periventricular white matter injury. Fractional anisotropy in the corticospinal tract at the internal capsule level could aid in the early diagnosis of spastic cerebral palsy with high diagnostic accuracy.

Cerebellar peduncle injury predicts motor impairments in preterm infants: A quantitative tractography study at term-equivalent age

PURPOSE

Cerebellar injury is well established as an important finding in preterm infants with cerebral palsy (CP). In this study, we investigated associations between injury to the cerebellar peduncles and motor impairments in preterm infants using quantitative tractography at term-equivalent age, which represents an early phase before the onset of motor impairments.

METHODS

We studied 64 preterm infants who were born at <33 weeks gestational age. These infants were divided into three groups: CP, Non-CP (defined as infants with periventricular leukomalacia but having normal motor function), and a Normal group. Diffusion tensor imaging was performed at term-equivalent age and motor function was assessed no earlier than a corrected age of 2 years. Using tractography, we measured fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the superior cerebellar peduncles (SCP) and middle cerebellar peduncles (MCP), as well as the motor/sensory tracts.

RESULTS

The infants in the CP group had significantly lower FA of the SCP and sensory tract than those in the other groups. There was no significant difference in FA and ADC of the motor tract among the three groups. Severity of CP had a significant correlation with FA of the MCP, but not with the FA of other white matter tracts.

CONCLUSION

Our results suggested that the infants with CP had injuries of the ascending tracts (e.g. the SCP and sensory tract), and that additional MCP injury might increase the severity of CP. Quantitative tractography assessment at term-equivalent age may be useful for screening preterm infants for prediction of future motor impairments.

Diffusion Tensor Tractography of the Cerebellar Peduncles in Prematurely Born 7-Year-Old Children

The objective of this study was to correlate neurodevelopmental outcome of preterm-born children and their perinatal clinical and imaging characteristics with diffusion magnetic resonance imaging (MRI) measures of the three cerebellar peduncles at age 7. Included in this prospective longitudinal study were 140 preterm-born children (<30 weeks gestation) who underwent neurodevelopmental assessment (IQ, motor, language, working memory) and diffusion-weighted imaging (DWI) at age 7 years. White matter tracts in the superior, middle, and inferior cerebellar peduncles were delineated using regions of interest drawn on T2-weighted images and fractional anisotropy (FA) maps. Diffusion measures (mean diffusivity (MD) and FA) and tract volumes were calculated. Linear regression was used to assess relationships with outcome. The severity of white matter injury in the neonatal period was associated with lower FA in the right superior cerebellar peduncle (SCP) and lower tract volumes of both SCPs and middle cerebellar peduncles (MCPs). In the MCP, higher IQ was associated with lower MD in the whole group and higher FA in right-handed children. In the SCP, lower motor scores were associated with higher MD and higher language scores were associated with higher FA. These associations remained significant in multivariable models. This study adds to the body of literature detailing the importance of cerebellar involvement in cognitive function related to reciprocal connections with supratentorial structures.

Disentangling How the Brain is "Wired" in Cortical (Cerebral) Visual Impairment

Cortical (cerebral) visual impairment (CVI) results from perinatal injury to visual processing structures and pathways of the brain and is the most common cause of severe visual impairment or blindness in children in developed countries. Children with CVI display a wide range of visual deficits including decreased visual acuity, impaired visual field function, as well as impairments in higher-order visual processing and attention. Together, these visual impairments can dramatically influence a child's development and well-being. Given the complex neurologic underpinnings of this condition, CVI is often undiagnosed by eye care practitioners. Furthermore, the neurophysiological basis of CVI in relation to observed visual processing deficits remains poorly understood. Here, we present some of the challenges associated with the clinical assessment and management of individuals with CVI. We discuss how advances in brain imaging are likely to help uncover the underlying neurophysiology of this condition. In particular, we demonstrate how structural and functional neuroimaging approaches can help gain insight into abnormalities of white matter connectivity and cortical activation patterns, respectively. Establishing a connection between how changes within the brain relate to visual impairments in CVI will be important for developing effective rehabilitative and education strategies for individuals living with this condition.

The Potential for Advanced Magnetic Resonance Neuroimaging Techniques in Pediatric Stroke Research

BACKGROUND

This article was written to provide clinicians and researchers with an overview of a number of advanced neuroimaging techniques in an effort to promote increased utility and the design of future studies using advanced neuroimaging in childhood stroke. The current capabilities of advanced magnetic resonance imaging techniques provide the opportunity to build on our knowledge of the consequences of stroke on the developing brain. These capabilities include providing information about the physiology, metabolism, structure, and function of the brain that are not routinely evaluated in the clinical setting.

METHODS

During the Proceedings of the Stroke Imaging Laboratory for Children Workshop in Toronto in June 2015, a subgroup of clinicians and imaging researchers discussed how the application of advanced neuroimaging techniques could further our understanding of the mechanisms of stroke injury and repair in the pediatric population. This subgroup was established based on their interest and commitment to design collaborative, advanced neuroimaging studies in the pediatric stroke population.

RESULTS

In working toward this goal, we first sought to describe here the magnetic resonance imaging techniques that are currently available for use, and how they have been applied in other stroke populations (e.g., adult and perinatal stroke).

CONCLUSIONS

With the continued improvement in advanced neuroimaging techniques, including shorter acquisition times, there is an opportunity to apply these techniques to their full potential in the research setting and learn more about the effects of stroke in the developing brain.

Longitudinal change in white matter in preterm infants without magnetic resonance imaging abnormalities: Assessment of serial diffusion tensor imaging and their relationship to neurodevelopmental outcomes

PURPOSE

We used diffusion tensor imaging (DTI) to evaluate longitudinal changes in fractional anisotropy (FA) of white matter tracts in preterm infants without abnormal magnetic resonance imaging (MRI) findings. Imaging was conducted at term equivalent age (TEA) and 1year of corrected age. Furthermore, we assessed correlations between FA and neurodevelopmental outcomes at 3years of corrected age to investigate brain prematurity of preterm infants without MRI abnormalities.

METHODS

Preterm infants underwent serial MRI at TEA and 1year of corrected age. Of these, 13 infants entered a retrospective study, undergoing neurodevelopmental assessment at 3years of corrected age. These infants were divided into two groups depending on gestational age (GA): <26weeks and ⩾26weeks. DTI-based tractography was performed to obtain the FA of the motor tract, sensory tract, superior cerebellar peduncle, middle cerebellar peduncle, and corpus callosum. FA was compared between two groups, and correlations between FA and neurodevelopmental outcomes were assessed.

RESULTS

FA of the splenium at TEA was significantly different between the two groups divided according to GA. However, this difference was no longer observed at 1year of corrected age. There was no correlation between FA of the splenium at TEA and neurodevelopmental assessment scores at 3years of corrected age.

CONCLUSIONS

At TEA, FA of the splenium was lower in younger GA infants without MRI abnormalities, but this may not affect subsequent neurodevelopmental outcomes.

Cerebral versus Ocular Visual Impairment: The Impact on Developmental Neuroplasticity

Cortical/cerebral visual impairment (CVI) is clinically defined as significant visual dysfunction caused by injury to visual pathways and structures occurring during early perinatal development. Depending on the location and extent of damage, children with CVI often present with a myriad of visual deficits including decreased visual acuity and impaired visual field function. Most striking, however, are impairments in visual processing and attention which have a significant impact on learning, development, and independence. Within the educational arena, current evidence suggests that strategies designed for individuals with ocular visual impairment are not effective in the case of CVI. We propose that this variance may be related to differences in compensatory neuroplasticity related to the type of visual impairment, as well as underlying alterations in brain structural connectivity. We discuss the etiology and nature of visual impairments related to CVI, and how advanced neuroimaging techniques (i.e., diffusion-based imaging) may help uncover differences between ocular and cerebral causes of visual dysfunction. Revealing these differences may help in developing future strategies for the education and rehabilitation of individuals living with visual impairment.

Neonatal diffusion tensor brain imaging predicts later motor outcome in preterm neonates with white matter abnormalities

BACKGROUND

White matter (WM) abnormalities associated with prematurity are one of the most important causes of neurological disability that involves spastic motor deficits in preterm newborns. This study aimed to evaluate regional microstructural changes in diffusion tensor imaging (DTI) associated with WM abnormalities.

METHODS

We prospectively studied extremely low birth weight (ELBW; <1000 g) preterm infants who were admitted to the Neonatal Intensive Care Unit of Hanyang University Hospital between February 2011 and February 2014. WM abnormalities were assessed with conventional magnetic resonance (MR) imaging and DTI near term-equivalent age before discharge. Region-of-interests (ROIs) measurements were performed to examine the regional distribution of fractional anisotropy (FA) values.

RESULTS

Thirty-two out of 72 ELBW infants underwent conventional MR imaging and DTI at term-equivalent age. Ten of these infants developed WM abnormalities associated with prematurity. Five of ten of those with WM abnormalities developed cerebral palsy (CP). DTI in the WM abnormalities with CP showed a significant reduction of mean FA in the genu of the corpus callosum (p = 0.022), the ipsilateral posterior limb of the internal capsule (p = 0.019), and the ipsilateral centrum semiovale (p = 0.012) compared to normal WM and WM abnormalities without CP. In infants having WM abnormalities with CP, early FA values in neonatal DTI revealed abnormalities of the WM regions prior to the manifestation of hemiparesis.

CONCLUSIONS

DTI performed at term equivalent age shows different FA values in WM regions among infants with or without WM abnormalities associated with prematurity and/or CP. Low FA values of ROIs in DTI are related with later development of spastic CP in preterm infants with WM abnormalities.

Whole-Brain DTI Assessment of White Matter Damage in Children with Bilateral Cerebral Palsy: Evidence of Involvement beyond the Primary Target of the Anoxic Insult

BACKGROUND AND PURPOSE

Cerebral palsy is frequently associated with both motor and nonmotor symptoms. DTI can characterize the damage at the level of motor tracts but provides less consistent results in nonmotor areas. We used a standardized pipeline of analysis to describe and quantify the pattern of DTI white matter abnormalities of the whole brain in a group of children with chronic bilateral cerebral palsy and periventricular leukomalacia. We also explored potential correlations between DTI and clinical scale metrics.

MATERIALS AND METHODS

Twenty-five patients (mean age, 11.8 years) and 25 healthy children (mean age, 11.8 years) were studied at 3T with a 2-mm isotropic DTI sequence. Differences between patients and controls were assessed both voxelwise and in ROIs obtained from an existing DTI atlas. Clinical metrics included the Gross Motor Function Classification System, the Manual Ability Classification System, and intelligence quotient.

RESULTS

The voxel-level and ROI-level analyses demonstrated highly significant (P < .001) modifications of DTI measurements in patients at several levels: cerebellar peduncles, corticospinal tracts and posterior thalamic radiations, posterior corpus callosum, external capsule, anterior thalamic radiation, superior longitudinal fasciculi and corona radiata, optic nerves, and chiasm. The reduction of fractional anisotropy values in significant tracts was between 8% and 30%. Statistically significant correlations were found between motor impairment and fractional anisotropy in corticospinal tracts and commissural and associative tracts of the supratentorial brain.

CONCLUSIONS

We demonstrated the involvement of several motor and nonmotor areas in the chronic damage associated with periventricular leukomalacia and showed new correlations between motor skills and DTI metrics.

Degenerative changes of the corticospinal tract in pediatric patients showing deteriorated motor function: A diffusion tensor tractography study

OBJECTIVE

We attempted to demonstrate the corresponding degenerative changes of the affected corticospinal tract (CST) in pediatric patients with deteriorated motor function using diffusion tensor tractography (DTT).

METHODS

We recruited three pediatric patients (corrected age: 2, 6 and 47 months, respectively) who showed impaired motor function.

RESULTS

DTT in each patient showed interruption of the CSTs of the hemisphere contralateral to the side of motor impairment. Despite motor impairment and abnormal DTT findings, none of the three patients received rehabilitative therapy. The patients (corrected age: 9, 53 and 59 months, respectively) and their parents visited our clinic again due to deterioration of motor functions. Follow-up DTT of all evaluated patients showed significant degenerative changes in the affected CSTs in accordance with the aggravation of motor impairment.

CONCLUSION

We presented degenerative changes of the affected CSTs in pediatric patients according to the deterioration of motor function.

Fractional anisotropy in children with dystonia or spasticity correlates with the selection for DBS or ITB movement disorder surgery

INTRODUCTION

There is increasing interest in neurosurgical interventions for hypertonicity in children and young people (CAYP), which often presents with a mixture of dystonia and spasticity. Significant spasticity would usually be considered a contraindication for deep brain stimulation (DBS) and more suitably treated with intrathecal baclofen (ITB). We aimed to explore whether white matter microstructure, as measured by Fractional Anisotropy (FA), differed between CAYP selected for DBS compared to ITB surgery.

METHODS

We retrospectively analysed Diffusion Tensor Imaging for 31 CAYP selected for DBS surgery (14 primary dystonia, 17 secondary dystonia) and 10 CAYP selected for ITB surgery. A voxel-wise comparison of FA values was performed using tract-based spatial statistics, comparing primary and secondary dystonia groups to the ITB group, and the two dystonia groups.

RESULTS

Widespread areas of reduced FA were demonstrated in ITB compared to either DBS group and in CAYP with secondary compared to primary dystonia. These changes were not restricted to motor pathways. Region of interest (ROI) analysis from the corticospinal tract (CST) demonstrated groupwise differences but overlapping values at the individual level.

CONCLUSIONS

DTI measures may contribute to decision making for CAYP selection for movement disorder surgery. Significant differences in CAYP with secondary dystonia selected for DBS surgery compared to CAYP selected for ITB pump implants, suggesting that more extensive white matter injury may be a feature of the spastic motor phenotype. Altered white matter microstructure could potentially explain the reduced responsiveness to interventions such as DBS in secondary compared to primary dystonia.

Regional vulnerability of longitudinal cortical association connectivity: Associated with structural network topology alterations in preterm children with cerebral palsy

Preterm born children with spastic diplegia type of cerebral palsy and white matter injury or periventricular leukomalacia (PVL), are known to have motor, visual and cognitive impairments. Most diffusion tensor imaging (DTI) studies performed in this group have demonstrated widespread abnormalities using averaged deterministic tractography and voxel-based DTI measurements. Little is known about structural network correlates of white matter topography and reorganization in preterm cerebral palsy, despite the availability of new therapies and the need for brain imaging biomarkers. Here, we combined novel post-processing methodology of probabilistic tractography data in this preterm cohort to improve spatial and regional delineation of longitudinal cortical association tract abnormalities using an along-tract approach, and compared these data to structural DTI cortical network topology analysis. DTI images were acquired on 16 preterm children with cerebral palsy (mean age 5.6 ± 4) and 75 healthy controls (mean age 5.7 ± 3.4). Despite mean tract analysis, Tract-Based Spatial Statistics (TBSS) and voxel-based morphometry (VBM) demonstrating diffusely reduced fractional anisotropy (FA) reduction in all white matter tracts, the along-tract analysis improved the detection of regional tract vulnerability. The along-tract map-structural network topology correlates revealed two associations: (1) reduced regional posterior-anterior gradient in FA of the longitudinal visual cortical association tracts (inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, optic radiation, posterior thalamic radiation) correlated with reduced posterior-anterior gradient of intra-regional (nodal efficiency) metrics with relative sparing of frontal and temporal regions; and (2) reduced regional FA within frontal-thalamic-striatal white matter pathways (anterior limb/anterior thalamic radiation, superior longitudinal fasciculus and cortical spinal tract) correlated with alteration in eigenvector centrality, clustering coefficient (inter-regional) and participation co-efficient (inter-modular) alterations of frontal-striatal and fronto-limbic nodes suggesting re-organization of these pathways. Both along tract and structural topology network measurements correlated strongly with motor and visual clinical outcome scores. This study shows the value of combining along-tract analysis and structural network topology in depicting not only selective parietal occipital regional vulnerability but also reorganization of frontal-striatal and frontal-limbic pathways in preterm children with cerebral palsy. These finding also support the concept that widespread, but selective posterior-anterior neural network connectivity alterations in preterm children with cerebral palsy likely contribute to the pathogenesis of neurosensory and cognitive impairment in this group.

Prediction of Motor Recovery Using Diffusion Tensor Tractography in Supratentorial Stroke Patients With Severe Motor Involvement

OBJECTIVE

To investigate whether early stage diffusion tensor tractography (DTT) values predict motor function at 3 months after onset in supratentorial stroke patients with severe motor involvement.

METHODS

A retrospective study design was used to analyze medical records and neuroimaging data of 49 supratentorial stroke patients with severe motor involvement. Diffusion tensor imaging was assessed within 3 weeks after stroke in all patients. Three-dimensional tractography of the ipsilateral corticospinal tract (CST) was performed using the fiber assignment of the continuous tracking algorithm. The two-step DTT analysis was used. The first step was classification according to ipsilateral CST visualization. The second step was a quantitative analysis of the visible-CST group parameters. Motor function was assessed at 2 weeks and at 3 months after stroke. Comparative and correlation analyses were performed between DTT-derived measures and motor assessment scores.

RESULTS

Motor function of the upper extremity at 3 months after stroke was significantly higher in the visible-CST group than that in the nonvisible-CST group (p<0.05). Early stage fractional anisotropy was of DTT correlated significantly with upper extremity motor function at 3 months after stroke in the visible-CST group (p<0.05).

CONCLUSION

These results demonstrate that early DTT-derived measures predict motor recovery in the upper extremity at 3 months after onset in supratentorial stroke patients with severe motor involvement.

Corticospinal Tract Injury Precedes Thalamic Volume Reduction in Preterm Infants with Cystic Periventricular Leukomalacia

OBJECTIVES

To measure both fractional anisotropy (FA) values in the corticospinal tracts (CSTs) and volume of the thalami in preterm infants with cystic periventricular leukomalacia (c-PVL) and to compare these measurements with control infants.

STUDY DESIGN

Preterm infants with c-PVL and controls with magnetic resonance imaging data acquired between birth and term equivalent age (TEA) were retrospectively identified in 2 centers. Tractography of the CST and segmentation of the thalamus were performed, and values from infants with c-PVL and controls were compared.

RESULTS

Thirty-three subjects with c-PVL and 31 preterm controls were identified. All had at least 1 scan up to TEA, and multiple scans were performed in 31 infants. A significant difference in FA values of the CST was found between cases and controls on the scans both before and at TEA. Absolute thalamic volumes were significantly reduced at TEA but not on the earlier scans. Data acquired in infancy showed lower FA values in infants with c-PVL.

CONCLUSIONS

Damage to the CST can be identified on the early scan and persists, whereas the changes in thalamic volume develop in the weeks between the early and term equivalent magnetic resonance imaging. This may reflect the difference between acute and remote effects of the extensive injury to the white matter caused by c-PVL.

Motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment: a diffusion tensor imaging study

Previous diffusion tensor imaging (DTI) studies regarding pediatric patients with motor dysfunction have confirmed the correlation between DTI parameters of the injured corticospinal tract and the severity of motor dysfunction. There is also evidence that DTI parameters can help predict the prognosis of motor function of patients with cerebral palsy. But few studies are reported on the DTI parameters that can reflect the motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment. In the present study, 36 pediatric patients with hemiplegic cerebral palsy were included. Before and after rehabilitation treatment, DTI was used to measure the fiber number (FN), fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of bilateral corticospinal tracts. Functional Level of Hemiplegia scale (FxL) was used to assess the therapeutic effect of rehabilitative therapy on clinical hemiplegia. Correlation analysis was performed to assess the statistical interrelationship between the change amount of DTI parameters and FxL. DTI findings obtained at the initial and follow-up evaluations demonstrated that more affected corticospinal tract yielded significantly decreased FN and FA values and significantly increased ADC value compared to the less affected corticospinal tract. Correlation analysis results showed that the change amount of FxL was positively correlated to FN and FA values, and the correlation to FN was stronger than the correlation to FA. The results suggest that FN and FA values can be used to evaluate the motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment and FN is of more significance for evaluation.

Prediction of motor outcomes and activities of daily living function using diffusion tensor tractography in acute hemiparetic stroke patients

[Purpose] The efficacy of diffusion tensor imaging in the prediction of motor outcomes and activities of daily living function remains unclear. We evaluated the most appropriate diffusion tensor parameters and methodology to determine whether the region of interest- or tractography-based method was more useful for predicting motor outcomes and activities of daily living function in stroke patients. [Subjects and Methods] Diffusion tensor imaging data within 10 days after stroke onset were collected and analyzed for 25 patients. The corticospinal tract was analyzed. Fractional anisotropy, number of fibers, and apparent diffusion coefficient were used as diffusion tensor parameters. Motor outcomes and activities of daily living function were evaluated on the same day as diffusion tensor imaging and at 1 month post-onset. [Results] The fractional anisotropy value of the affected corticospinal tract significantly correlated with the motor outcome and activities of daily living function within 10 days post-onset and at 1 month post-onset. Tthere were no significant correlations between other diffusion tensor parameters and motor outcomes or activities of daily living function. [Conclusion] The fractional anisotropy value of the affected corticospinal tract obtained using the tractography-based method was useful for predicting motor outcomes and activities of daily living function in stroke patients.

Development of the Corticospinal and Callosal Tracts from Extremely Premature Birth up to 2 Years of Age

White matter tracts mature asymmetrically during development, and this development can be studied using diffusion magnetic resonance imaging. The aims of this study were i. to generate dynamic population-averaged white matter registration templates covering in detail the period from 25 weeks gestational age to term, and extending to 2 years of age based on DTI and fractional anisotropy, ii. to produce tract-specific probability maps of the corticospinal tracts, forceps major and forceps minor using probabilistic tractography, and iii. to assess the development of these tracts throughout this critical period of neurodevelopment. We found evidence for asymmetric development across the fiber bundles studied, with the corticospinal tracts showing earlier maturation (as measured by fractional anisotropy) but slower volumetric growth compared to the callosal fibers. We also found evidence for an anterior to posterior gradient in white matter microstructure development (as measured by mean diffusivity) in the callosal fibers, with the posterior forceps major developing at a faster rate than the anterior forceps minor in this age range. Finally, we report a protocol for delineating callosal and corticospinal fibers in extremely premature cohorts, and make available population-averaged registration templates and a probabilistic tract atlas which we hope will be useful for future neonatal and infant white-matter imaging studies.

Detection of hand and leg motor tract injury using novel diffusion tensor MRI tractography in children with central motor dysfunction

PURPOSE

To examine whether an objective segmenation of corticospinal tract (CST) associated with hand and leg movements can be used to detect central motor weakness in the corresponding extremities in a pediatric population.

MATERIAL AND METHODS

This retrospective study included diffusion tensor imaging (DTI) of 25 children with central paresis affecting at least one limb (age: 9.0±4.2years, 15 boys, 5/13/7 children with left/right/both hemispheric lesions including ischemia, cyst, and gliosis), as well as 42 pediatric control subjects with no motor dysfunction (age: 9.0±5.5years, 21 boys, 31 healthy/11 non-lesional epilepsy children). Leg- and hand-related CST pathways were segmented using DTI-maximum a posteriori (DTI-MAP) classification. The resulting CST volumes were then divided by total supratentorial white matter volume, resulting in a marker called "normalized streamline volume ratio (NSVR)" to quantify the degree of axonal loss in separate CST pathways associated with leg and hand motor functions. A receiver operating characteristic curve was applied to measure the accuracy of this marker to identify extremities with motor weakness.

RESULTS

NSVR values of hand/leg CST selectively achieved the following values of accuracy/sensitivity/specificity: 0.84/0.84/0.57, 0.82/0.81/0.55, 0.78/0.75/0.55, 0.79/0.81/0.54 at a cut-off of 0.03/0.03/0.03/0.02 for right hand CST, left hand CST, right leg CST, and left leg CST, respectively. Motor weakness of hand and leg was most likely present at the cut-off values of hand and leg NSVR (i.e., 0.029/0.028/0.025/0.020 for left-hand/right-hand/left-leg/right-leg). The control group showed a moderate age-related increase in absolute CST volumes and a biphasic age-related variation of the normalized CST volumes, which were lacking in the paretic children.

CONCLUSIONS

This study demonstrates that DTI-MAP classification may provide a new imaging tool to quantify axonal loss in children with central motor dysfunction. Using this technique, we found that early-life brain lesions affect the maturational trajectory of the primary motor pathway which may be used as an effective marker to facilitate evidence-based treatment of paretic children.

White matter tract integrity and developmental outcome in newborn infants with hypoxic-ischemic encephalopathy treated with hypothermia

AIM

To determine whether corpus callosum (CC) and corticospinal tract (CST) diffusion tensor imaging (DTI) measures relate to developmental outcome in encephalopathic newborn infants after therapeutic hypothermia.

METHOD

Encephalopathic newborn infants enrolled in a longitudinal study underwent DTI after hypothermia. Parametric maps were generated for fractional anisotropy, mean, radial, and axial diffusivity. CC and CST were segmented by DTI-based tractography. Multiple regression models were used to examine the association of DTI measures with Bayley-II Mental (MDI) and Psychomotor Developmental Index (PDI) at 15 months and 21 months of age.

RESULTS

Fifty-two infants (males n=32, females n=20) underwent DTI at median age of 8 days. Two were excluded because of poor magnetic resonance imaging quality. Outcomes were assessed in 42/50 (84%) children at 15 months and 35/50 (70%) at 21 months. Lower CC and CST fractional anisotropy were associated with lower MDI and PDI respectively, even after controlling for gestational age, birth weight, sex, and socio-economic status. There was also a direct relationship between CC axial diffusivity and MDI, while CST radial diffusivity was inversely related to PDI.

INTERPRETATION

In encephalopathic newborn infants, impaired microstructural organization of the CC and CST predicts poorer cognitive and motor performance respectively. Tractography provides a reliable method for early assessment of perinatal brain injury.

Low-grade intraventricular hemorrhage disrupts cerebellar white matter in preterm infants: evidence from diffusion tensor imaging

INTRODUCTION

Recent diffusion tensor imaging (DTI) studies have demonstrated that leakage of hemosiderin into cerebrospinal fluid (CSF), which is caused by high-grade intraventricular hemorrhage (IVH), can affect cerebellar development in preterm born infants. However, a direct effect of low-grade IVH on cerebellar development is unknown. Thus, we evaluated the cerebellar and cerebral white matter (WM) of preterm infants with low-grade IVH.

METHODS

Using DTI tractography performed at term-equivalent age, we analyzed 42 infants who were born less than 30 weeks gestational age (GA) at birth (22 with low-grade IVH, 20 without). These infants were divided into two birth groups depending on GA, and we then compared the presence and absence of IVH which was diagnosed by cerebral ultrasound (CUS) within 10 days after birth or conventional magnetic resonance imaging (MRI) at term-equivalent age in each group. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) at the superior cerebellar peduncle (SCP), middle cerebellar peduncle (MCP), motor tract, and sensory tract were measured.

RESULTS

In the SCP, preterm born infants with IVH had lower FA values compared with infants without IVH. In particular, younger preterm birth with IVH had lower FA values in the SCP and motor tract and higher ADC values in the MCP.

CONCLUSION

Low-grade IVH impaired cerebellar and cerebral WM, especially in the SCP. Moreover, younger preterm infants exhibited greater disruptions to cerebellar WM and the motor tract than infants of older preterm birth.

An fNIRS exploratory investigation of the cortical activity during gait in children with spastic diplegic cerebral palsy

OBJECTIVE

The primary aim of this exploratory investigation was to determine if there are differences in cortical activation of children with spastic diplegic cerebral palsy (CP) and typically developing children during gait.

METHODS

Functional near-infrared spectroscopy was used to measure the concentration of oxygenated hemoglobin that was present in the supplementary motor area, pre-central gyrus, post-central gyrus and superior parietal lobule as the children walked on a treadmill. A sagittal plane video was concurrently collected and later digitized to quantify the temporal gait variations.

RESULTS

(1) The children with CP had an increased amount of activation in the sensorimotor cortices and superior parietal lobule during gait, (2) the children with CP had a greater amount of variability or error in their stride time intervals, and (3) an increased amount of error in the temporal gait kinematics was associated with an increased amount of activity across the cortical network.

CONCLUSION

Our results suggest that the perinatal damage and subsequent neural reorganization that occurs with spastic diplegic CP may impact the functional cortical activity for controlling gait. Furthermore, our results imply the increased cortical activity of the somatosensory cortices and superior parietal cortices may underlie the greater amount of error in the temporal gait kinematics.

Advanced fiber tracking in early acquired brain injury causing cerebral palsy

BACKGROUND AND PURPOSE

Diffusion-weighted MR imaging and fiber tractography can be used to investigate alterations in white matter tracts in patients with early acquired brain lesions and cerebral palsy. Most existing studies have used diffusion tensor tractography, which is limited in areas of complex fiber structures or pathologic processes. We explored a combined normalization and probabilistic fiber-tracking method for more realistic fiber tractography in this patient group.

MATERIALS AND METHODS

This cross-sectional study included 17 children with unilateral cerebral palsy and 24 typically developing controls. DWI data were collected at 1.5T (45 directions, b=1000 s/mm(2)). Regions of interest were defined on a study-specific fractional anisotropy template and mapped onto subjects for fiber tracking. Probabilistic fiber tracking of the corticospinal tract and thalamic projections to the somatosensory cortex was performed by using constrained spherical deconvolution. Tracts were qualitatively assessed, and DTI parameters were extracted close to and distant from lesions and compared between groups.

RESULTS

The corticospinal tract and thalamic projections to the somatosensory cortex were realistically reconstructed in both groups. Structural changes to tracts were seen in the cerebral palsy group and included splits, dislocations, compaction of the tracts, or failure to delineate the tract and were associated with underlying pathology seen on conventional MR imaging. Comparisons of DTI parameters indicated primary and secondary neurodegeneration along the corticospinal tract. Corticospinal tract and thalamic projections to the somatosensory cortex showed dissimilarities in both structural changes and DTI parameters.

CONCLUSIONS

Our proposed method offers a sensitive means to explore alterations in WM tracts to further understand pathophysiologic changes following early acquired brain injury.

Diffusion-weighted imaging and magnetic resonance proton spectroscopy following preterm birth

AIM

To study the associations between magnetic resonance proton spectroscopy (MRS) data and apparent diffusion coefficients (ADC) from the preterm brain with developmental outcome at 18 months corrected age and clinical variables.

MATERIALS AND METHODS

A prospective observational cohort study of 67 infants born before 35 weeks gestational age who received both magnetic resonance imaging of the brain between 37 and 44 weeks corrected gestational age and developmental assessment around 18 months corrected age.

RESULTS

No relationships were found between ADC values and MRS results or outcome. MRS ratios involving N-acetyl aspartate (NAA) from the posterior white matter were associated with "severe" and "moderate to severe" difficulties, and fine motor scores were significantly lower in participants with a visible lactate doublet in the posterior white matter. The presence of a patent ductus arteriosus (PDA) was the only clinical factor related to NAA ratios.

CONCLUSION

Altered NAA levels in the posterior white matter may reflect subtle white matter injury associated with neuro-developmental difficulties, which may be related to a PDA. Further work is needed to assess the longer-term neuro-developmental implications of these findings, and to study the effect of PDAs on developmental outcome in later childhood/adolescence.

Correlation between fractional anisotropy and motor outcomes in one-year-old infants with periventricular brain injury

PURPOSE

To determine whether motor outcomes of an exercise intervention beginning at 2 months corrected age (CA) in children with periventricular brain injury (PBI) are correlated with fractional anisotropy (FA) measures derived from diffusion tensor imaging (DTI) at 12 months CA.

MATERIALS AND METHODS

DTI was performed in eight infants with PBI who were randomly assigned to kicking and treadmill stepping exercise or a no-training condition. Development was assessed using the Alberta Infant Motor Scale (AIMS) and the Gross Motor Function Classification System (GMFCS). FA values were derived from regions of interest (ROIs) in the middle third of the posterior limb of the internal capsule (PLIC) and the posterior thalamic radiation (PTR).

RESULTS

Significant correlations were observed between motor development and FA measures. For PLIC, the correlation coefficients were 0.82 between FA and AIMS, and -0.92 between FA and GMFCS, while for PTR the corresponding correlation coefficients were 0.73 and -0.80, respectively.

CONCLUSION

Results of this study suggest that quantitative evaluation of white matter tracts using DTI at 12 months CA may be useful for assessment of brain plasticity in children.

Validation of a brain MRI relaxometry protocol to measure effects of preterm birth at a flexible postnatal age

BACKGROUND

Magnetic resonance imaging (MRI) is a useful tool to study brain growth and organization in preterm neonates for clinical and research purposes, but its practicality can be limited by time and medical constraints. The aim of this study was to determine if MRI relaxometry of the deep nuclei, as opposed to white matter, would reflect the influence of gestational age at birth on structures essential to motor development, regardless of postnatal age at the time of imaging.

RESULTS

This was a prospective observational study of infants without brain injury on conventional neuroimaging who were cared for in the neonatal intensive care unit (NICU) at Vanderbilt. Infants were studied using MRI relaxometry within a 2-month window of postmenstrual term age. In 45 infants, white matter MRI T1 relaxation times were influenced by both gestational age and postnatal age at imaging time (R(2) = 0.19 for gestational age vs. R(2) = 0.34 adjusting for both gestational age and age at imaging; all p < 0.01). Similar results were obtained with T2 relaxation times. In contrast, globus pallidus T1 reflected gestational age but was minimally affected by postnatal age (R(2) = 0.50 vs. 0.57, p < 0.001).

CONCLUSIONS

The results obtained using this imaging protocol are consistent with the slow maturation of the globus pallidus, essential to normal development of complex motor programs into adulthood. Globus pallidus MRI relaxometry measures the impact of gestational age at birth on brain development independent of postnatal age in preterm infants and should prove useful for predictive modeling in a flexible time-window around postmenstrual term age.

Changes in diffusion tensor tractographic findings associated with constraint-induced movement therapy in young children with cerebral palsy

OBJECTIVE

The objective of the study was to determine whether constraint-induced movement therapy (CIMT) could lead to changes in diffusion tensor tractography (DTT) associated with clinical improvement in young children with unilateral cerebral palsy (CP).

METHODS

A standardized pediatric CIMT protocol (4weeks, 120h of constraint) was used on 10 children with unilateral CP who were younger than 5years. DTT was performed in five participants before and after the intervention. Clinical outcome was measured by using the Pediatric Motor Activity Log (PMAL), Quality of Upper Extremity Skills Test (QUEST), and self-care domain of the Pediatric Evaluation of Disability Inventory.

RESULTS

In two patients, the affected corticospinal tract (CST) visible on pretreatment DTT became more prominent on posttreatment DTT. In one patient, the affected CST was not visible on pretreatment DTT, but was visible on posttreatment DTT. All the clinical outcomes significantly improved in the CIMT group compared with the control group. Changes in the PMAL how often scale (PMAL-HO) score significantly differed between the CIMT and control groups.

CONCLUSIONS

Changes in the properties of the affected CST on DTT were accompanied with improved arm function after CIMT in the children with CP.

SIGNIFICANCE

CIMT might lead to CST reorganization in young children with CP.

Children with cerebral palsy have greater stochastic features present in the variability of their gait kinematics

Children with CP have a more variable gait pattern. However, it is currently unknown if these variations arise from deterministic variations that are a result of a change in the motor command or stochastic features that are present in the nervous system. The aim of this investigation was to use a Langevin equation methodology to evaluate the deterministic and stochastic features that are present in the variability of the gait kinematics of children with cerebral palsy (CP). Ten children with spastic diplegic CP and nine typically developing (TD) children participated in this investigation. All of the children walked on a treadmill for 2 min while a three-dimensional motion capture system recorded the step kinematics. Our major findings for this investigation were: (1) children with CP had greater variability in their gait patterns than TD children, (2) the variability of the children with CP and TD children had similar deterministic features, (3) the variability had greater stochastic features for the children with CP, and (4) the increase in the amount of variability was strongly correlated with the increase in stochastic features. These results indicate that the variability seen in the gait patterns of children with CP may be due to the inability to suppress the noise that is present in the neuromuscular system.

Identification and interpretation of microstructural abnormalities in motor pathways in adolescents born preterm

There has been extensive interest in assessing the long-term effects of preterm birth on brain white matter microstructure using diffusion MRI. Our aim in this study is to explore diffusion MRI differences between adolescents born preterm and term born controls, with a specific interest in characterising how such differences are manifested in white matter regions containing predominantly single or crossing fibre populations. Probabilistic high angular resolution tractography together with large deformation spatial normalisation were used to objectively investigate diffusion tensor parameters at regular intervals along fibre tracts of 45 adolescents born before 33 weeks of gestation and 30 term-born typically developing adolescents. Diffusion parameters were significantly different between preterms and controls at several levels along the cortico-spinal, thalamo-cortical and transcallosal pathways. Within the predominantly single fibre regions of the corpus callosum and internal capsule, in the preterms mean diffusivity (MD) was found to be increased while fractional anisotropy (FA) was decreased compared to controls. In contrast, however, where these pathways traversed the centrum semiovale, FA and MD were both significantly increased. The major contributor to reduced FA in preterms in predominantly single fibre regions was the increased radial eigenvalue (i.e. increased radial diffusivity). In predominantly crossing-fibre regions, the tensor eigenvalues are not meaningful, and the observed increase in FA is likely to be due to a decrease in anisotropy in one of the contributing fibre bundles. Similar differences (although less pronounced) were observed after excluding preterms with radiological signs of preterm brain injury from the sample. In summary, white matter microstructure was found to be altered in motor pathways in adolescents born preterm. Disruption of white matter (WM) microstructure in a single fibre region with resulting higher radial diffusivity leads to lower FA, whereas selective disruption of one fibre population in a crossing fibre region is observed to lead to higher FA. These findings challenge the common simplistic interpretation of FA as a measure of WM tract integrity.

CST recovery in pediatric hemiplegic patients: Diffusion tensor tractography study

Many diffusion tensor imaging (DTI) studies have reported an association between corticospinal tract (CST) injury and motor dysfunction. In this study, we investigated CST recovery in 29 pediatric patients with clinical hemiplegia using DTI. We measured the fractional anisotropy (FA), apparent diffusion coefficient (ADC), and asymmetric anisotropy (AA) of both CSTs. The patients were classified into three groups according to severity of CST disruption of the more affected hemisphere. DTI was followed up for 9.34 ± 2.07 months after initial evaluation. The FA value of the more affected CST showed a significant decrease compared to the opposite side at initial and follow up evaluation, respectively (p<0.05). The FA value of both CSTs showed a significant increase at follow up compared to the initial evaluation, while more changes were observed on the more affected side, compared with the less affected side (p<0.05). AA showed a significant decrease at follow up, and showed significant correlation with interval change of FA value of the more affected side, not with that of the less affected side (r=0.543, p<0.05). 19 patients showed change of CST integrity. In the current study, the results of DTI showed recovery of the CST and provided radiologic evidence for a scientific basis of brain plasticity in pediatric patients.

Effects of chemotherapy on the brain in childhood: diffusion tensor imaging of subtle white matter damage

INTRODUCTION

With reducing mortality in children with hematological malignancies, the survivors' quality of life regarding development of chronic neurological disturbances is important. We aimed to determine whether chemotherapy affects white matter (WM).

METHODS

Using brain diffusion tensor imaging, we evaluated 17 patients (15 with acute lymphoblastic leukemia, 2 with non-Hodgkin's lymphoma; 9 male, 8 female; age, 1.6-13 years) before and after chemotherapy. We measured the quantitative values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) at the regions of interest (ROIs) such as periventricular WM, corona radiata, posterior limb of the internal capsule, and corpus callosum. We assessed sensorimotor and callosal tracts by tractography.

RESULTS

Reduction in FA and increase in ADC were significant at the ROIs of the left and right anterior periventricular WM and corona radiata and at the tract passing through the genu. A significant reduction in FA with a nonsignificant increase in ADC was seen at the ROI of the genu and at the tracts passing through the body and isthmus.

CONCLUSION

Chemotherapy in children with hematological malignancies predominantly affects the frontal WM. This finding might indicate a negative effect of chemotherapy on neurological development in children with hematological malignancies.

Effects of white matter injury on resting state fMRI measures in prematurely born infants

The cerebral white matter is vulnerable to injury in very preterm infants (born prior to 30 weeks gestation), resulting in a spectrum of lesions. These range from severe forms, including cystic periventricular leukomalacia and periventricular hemorrhagic infarction, to minor focal punctate lesions. Moderate to severe white matter injury in preterm infants has been shown to predict later neurodevelopmental disability, although outcomes can vary widely in infants with qualitatively comparable lesions. Resting state functional connectivity magnetic resonance imaging has been increasingly utilized in neurodevelopmental investigations and may provide complementary information regarding the impact of white matter injury on the developing brain. We performed resting state functional connectivity magnetic resonance imaging at term equivalent postmenstrual age in fourteen preterm infants with moderate to severe white matter injury secondary to periventricular hemorrhagic infarction. In these subjects, resting state networks were identifiable throughout the brain. Patterns of aberrant functional connectivity were observed and depended upon injury severity. Comparisons were performed against data obtained from prematurely-born infants with mild white matter injury and healthy, term-born infants and demonstrated group differences. These results reveal structural-functional correlates of preterm white matter injury and carry implications for future investigations of neurodevelopmental disability.

Assessing postural asymmetry with a podoscope in infants with Central Coordination Disturbance

The aim of this study was to digitally evaluate the incidence and severity of postural asymmetry in infants with Central Coordination Disturbance (CCD) by using a computer-aided podoscope (PodoBaby) from CQ Elektronik System. A sample of 120 infants aged from 3 months (± 1 week) to 6 months (± 1 week) took part in the study, of which 60 were diagnosed with CCD by a neurologist using Vojta's method and the remaining half healthy, non-afflicted infants. The relationships between Vojta's method, as a subjective clinical diagnostic tool for assessing the functional performance of infants with CCD, and the postural asymmetry results recorded with the podoscope, were also defined. Each infant was placed on the podoscope and photographed underneath in two positions: first lying on their back and then on their stomach. A symmetry index was used to calculate body asymmetry, i.e., the percent difference of abnormal body posture by favoring one side of the body to the other. The results confirmed that postural asymmetry assessed by the PodoBaby was in line with the earlier clinical diagnosis using Vojta's method. Statistically significant differences in postural asymmetry were also found between the healthy infants and infants with CCD. In addition, significant relationships were demonstrated in the magnitude and direction of asymmetry in the stomach and back positions.

Evaluation of normal appearing spinal cord by diffusion tensor imaging, fiber tracking, fractional anisotropy, and apparent diffusion coefficient measurement in 13 dogs

BACKGROUND

Functional magnetic resonance (fMR) imaging offers plenty of new opportunities in the diagnosis of central nervous system diseases. Diffusion tensor imaging (DTI) is a technique sensitive to the random motion of water providing information about tissue architecture. We applied DTI to normal appearing spinal cords of 13 dogs of different breeds and body weights in a 3.0 T magnetic resonance (MR) scanner. The aim was to study fiber tracking (FT) patterns by tractography and the variations of the fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) observed in the spinal cords of dogs with different sizes and at different locations (cervical and thoracolumbar). For that reason we added a DTI sequence to the standard clinical MR protocol. The values of FA and ADC were calculated by means of three regions of interest defined on the cervical or the thoracolumbar spinal cord (ROI 1, 2, and 3).

RESULTS

The shape of the spinal cord fiber tracts was well illustrated following tractography and the exiting nerve roots could be differentiated from the spinal cord fiber tracts. Routine MR scanning times were extended for 8 to 12 min, depending on the size of the field of view (FOV), the slice thickness, and the size of the interslice gaps. In small breed dogs (<15 kg body weight) the fibers could be tracked over a length of approximately 10 vertebral bodies with scanning times of about 8 min, whereas in large breed dogs (>25 kg body weight) the traceable fiber length was about 5 vertebral bodies which took 10 to 12 min scanning time. FA and ADC values showed mean values of 0.447 (FA), and 0.560×10(-3) mm2/s (ADC), respectively without any differences detected with regard to different dog sizes and spinal cord 45 segments examined.

CONCLUSION

FT is suitable for the graphical depiction of the canine spinal cord and the exiting nerve roots. The FA and ADC values offer an objective measure for evaluation of the spinal cord fiber integrity in dogs.

Interhemispheric and intrahemispheric connectivity and manual skills in children with unilateral cerebral palsy

This study investigated patterns of motor brain activation, white matter (WM) integrity of inter- and intrahemispheric connectivity and their associations with hand function in children with unilateral cerebral palsy (CP-U). Fourteen CP-U (mean age 10.6 ± 2.7 years) and 14 typically developing children (TDC) underwent magnetic resonance imaging. CP-U underwent extensive motor evaluation. Pattern of brain activation during a motor task was studied in 12 CP-U and six TDC, by calculating laterality index (LI) and percent activation in the sensorimotor areas (around the central sulcus), and quantifying the activation in the supplementary motor area (SMA). Diffusivity parameters were measured in CP-U and eight other TDC for the corpus callosum (CC), affected and less affected cortico-spinal tracts (CST), and posterior limb of the internal capsule (PLIC). Abnormal patterns of brain activation were detected in areas around the central sulcus in 9/12 CP-U, with bilateral activation and/or reduced percent activation. More activation in areas around the central sulcus of the affected hemisphere was associated with better hand function. CP-U demonstrated more activation in the SMA when moving the affected hand compared to the less affected hand. CP-U displayed reduced WM integrity compared to TDC, in the midbody and splenium of the CC, affected CST and affected PLIC. WM integrity in these tracts was correlated with hand function. While abnormal pattern of brain activation was detected mainly when moving the affected hand, the integrity of the CC was correlated with function of both hands and bimanual skills. This study highlights the importance of interhemispheric connectivity for hand function in CP-U, which may have clinical implications regarding prognosis and management.

Diffuse reduction of white matter connectivity in cerebral palsy with specific vulnerability of long range fiber tracts

Cerebral palsy (CP) is a heterogeneous group of non-progressive motor disorders caused by injury to the developing fetal or infant brain. Although the defining feature of CP is motor impairment, numerous other neurodevelopmental disabilities are associated with CP and contribute greatly to its morbidity. The relationship between brain structure and neurodevelopmental outcomes in CP is complex, and current evidence suggests that motor and developmental outcomes are related to the spatial pattern and extent of brain injury. Given that multiple disabilities are frequently associated with CP, and that there is increasing burden of neurodevelopmental disability with increasing motor severity, global white matter (WM) connectivity was examined in a cohort of 17 children with bilateral CP to test the hypothesis that increased global WM damage will be seen in the group of severely affected (Gross Motor Function Classification Scale (GMFCS) level of IV) as compared to moderately affected (GMFCS of II or III) individuals. Diffusion tensor tractography was performed and the resulting fibers between anatomically defined brain regions were quantified and analyzed in relation to GMFCS levels. Overall, a reduction in total WM connectivity throughout the brain in severe versus moderate CP was observed, including but not limited to regions associated with the sensorimotor system. Our results also show a diffuse and significant reduction in global inter-regional connectivity between severity groups, represented by inter-regional fiber count, throughout the brain. Furthermore, it was also observed that there is a significant difference (p = 0.02) in long-range connectivity in patients with severe CP as compared to those with moderate CP, whereas short-range connectivity was similar between groups. This new finding, which has not been previously reported in the CP literature, demonstrates that CP may involve distributed, network-level structural disruptions.

Physical therapy observation and assessment in the neonatal intensive care unit

This article presents the elements of the Observation and Assessment section of the Infant Care Path for Physical Therapy in the Neonatal Intensive Care Unit (NICU). The types of physical therapy assessments presented in this path are evidence-based and the suggested timing of these assessments is primarily based on practice knowledge from expert therapists, with supporting evidence cited. Assessment in the NICU begins with a thorough review of the health care record. Assessment proceeds by using the least invasive methods of gathering the behavioral, developmental, physiologic, and musculoskeletal information needed to implement a physical therapy plan of care. As the neonate matures and can better tolerate handling, assessment methods include lengthier standardized tests with the psychometric properties needed for informing diagnosis and intervention planning. Standardized tests and measures for screening, diagnosis, and developmental assessment are appraised and special considerations for assessment of neonates in the NICU are discussed.

Diffusion tensor imaging of normal brain development

Diffusion tensor imaging (DTI) is an MRI technique that can measure the macroscopic structural organization in brain tissues. DTI has been shown to provide information complementary to relaxation-based MRI about the changes in the brain's microstructure. In the pediatric population, DTI enables quantitative observation of the maturation process of white matter structures. Its ability to delineate various brain structures during developmental stages makes it an effective tool with which to characterize both the normal and abnormal anatomy of the developing brain. This review will highlight the advantages, as well as the common technical pitfalls of pediatric DTI. In addition, image quantification strategies for various DTI-derived parameters and the normal brain developmental changes associated with these parameters are discussed.

Disruption of raphé serotonergic neural projections to the cortex: a potential pathway contributing to remote loss of brainstem neurons following neonatal hypoxic-ischemic brain injury

Neuronal injury is a key feature of neonatal hypoxic-ischemic (HI) brain injury. However, the mechanisms underpinning neuronal losses, such as in the brainstem, are poorly understood. One possibility is that disrupted neural connections between the cortex and brainstem may compromise the survival of neuronal cell bodies in the brainstem. We investigated whether brainstem raphé serotonergic neurons that project to the cortex are lost after HI. We also tested if neuroinflammation has a role in disrupting brainstem raphé projections. Postnatal day 3 (P3) rats underwent unilateral carotid artery ligation followed by hypoxia (6% oxygen for 30 min). A retrograde tracer, choleratoxin b, was deposited in the motor cortex on P38. On P45 we found that retrogradely labelled neurons in the dorsal raphé dorsal, ventrolateral, interfascicular, caudal and ventral nuclei were lost after P3 HI. All retrogradely labelled neurons in the raphé nuclei were serotonergic. Numbers of retrogradely labelled neurons were also reduced in the ventromedial thalamus and basolateral amygdala. Minocycline treatment (45 mg/kg 2 h post-HI, 22.5 mg/kg daily P4-P9) attenuated losses of retrogradely labelled neurons in the dorsal raphé ventrolateral, interfascicular and ventral raphé nuclei, and the ventromedial thalamus. These results indicate that raphé neurons projecting to the cortex constitute a population of serotonergic neurons that are lost after P3 HI. Furthermore, neuroinflammation has a role in the disruption of raphé and thalamic neural projections. Future studies investigating the cellular mechanisms of axonal degeneration may reveal new targets for interventions to prevent neuronal losses after neonatal HI.

New insights into the pathology of white matter tracts in cerebral palsy from diffusion magnetic resonance imaging: a systematic review

AIM

Structural connectivity analysis using diffusion magnetic resonance imaging (dMRI) and tractography has become the method of choice for studying white matter pathology and reorganization in children with congenital hemiplegia. To evaluate its role in the research domain, we systematically reviewed the literature about children with cerebral palsy (CP) to document common findings and identify strengths and possible limitations of this neuroimaging technology.

METHOD

A literature search was performed for peer-reviewed studies pertaining to dMRI and CP.

RESULTS

Twenty-two studies met the inclusion criteria. The corticospinal tract was studied in greatest detail (18/22). The most common finding was decreased fractional anisotropy and/or increased mean diffusivity, indicating significant loss in the integrity of these corticomotor pathways. Fewer studies assessed ascending sensorimotor pathways including the posterior and superior thalamic radiations, which also showed decreased fractional anisotropy. Anisotropy indices (fractional anisotropy, mean diffusivity) obtained for both corticomotor and sensorimotor tracts were repeatedly shown to correlate with clinical measures. Other tracts studied included commissural and association fibres, which showed conflicting results.

INTERPRETATION

There is sound evidence that dMRI-based connectivity techniques are useful for improving our understanding of the structure-function relationships of corticomotor and sensorimotor neural networks in CP.

Thalamic changes in a preterm sample with periventricular leukomalacia: correlation with white-matter integrity and cognitive outcome at school age

INTRODUCTION

Thalamic abnormalities have been well documented in preterms with periventricular leukomalacia (PVL), although their contribution to long-term cognitive dysfunctions has not been thoroughly investigated.

RESULTS

Significant differences between groups were observed for global thalamic volume. Neuropsychological assessments showed that preterms with PVL scored within the normal range, although significantly below controls in the full intelligence quotient and the specific cognitive domains of processing speed and working memory. Correlations of several thalamic regions with Working Memory Index and FIQ were found in the PVL group. Moreover, thalamic atrophy correlated with white-matter (WM) damage indexes (fractional anisotropy and radial diffusivity) assessed by diffusion tensor imaging.

DISCUSSION

The findings suggest that thalamic damage is a common correlate of WM microstructural alterations and might be involved in the cognitive deficits seen in premature infants with PVL at school age.

METHODS

We analyzed the impact of PVL-associated thalamic injury on cognitive status at school age and its correlation with WM integrity as measured by magnetic resonance imaging techniques. Thalamic volume and shape of 21 preterm children with PVL were compared with those of 11 preterm children of similar gestational age and birth weight with no evidence of focal WM abnormality.

Neuroimaging biomarkers of preterm brain injury: toward developing the preterm connectome

For typically developing infants, the last trimester of fetal development extending into the first post-natal months is a period of rapid brain development. Infants who are born premature face significant risk of brain injury (e.g., intraventricular or germinal matrix hemorrhage and periventricular leukomalacia) from complications in the perinatal period and also potential long-term neurodevelopmental disabilities because these early injuries can interrupt normal brain maturation. Neuroimaging has played an important role in the diagnosis and management of the preterm infant. Both cranial US and conventional MRI techniques are useful in diagnostic and prognostic evaluation of preterm brain development and injury. Cranial US is highly sensitive for intraventricular hemorrhage (IVH) and provides prognostic information regarding cerebral palsy. Data are limited regarding the utility of MRI as a routine screening instrument for brain injury for all preterm infants. However, MRI might provide diagnostic or prognostic information regarding PVL and other types of preterm brain injury in the setting of specific clinical indications and risk factors. Further development of advanced MR techniques like volumetric MR imaging, diffusion tensor imaging, metabolic imaging (MR spectroscopy) and functional connectivity are necessary to provide additional insight into the molecular, cellular and systems processes that underlie brain development and outcome in the preterm infant. The adult concept of the "connectome" is also relevant in understanding brain networks that underlie the preterm brain. Knowledge of the preterm connectome will provide a framework for understanding preterm brain function and dysfunction, and potentially even a roadmap for brain plasticity. By combining conventional imaging techniques with more advanced techniques, neuroimaging findings will likely be used not only as diagnostic and prognostic tools, but also as biomarkers for long-term neurodevelopmental outcomes, instruments to assess the efficacy of neuroprotective agents and maneuvers in the NICU, and as screening instruments to appropriately select infants for longitudinal developmental interventions.