Alexander H. Hoon

Sensory and motor deficits in children with cerebral palsy born preterm correlate with diffusion tensor imaging abnormalities in thalamocortical pathways

Aim  Cerebral palsy (CP) is frequently linked to white matter injury in children born preterm. Diffusion tensor imaging (DTI) is a powerful technique providing precise identification of white matter microstructure. We investigated the relationship between DTI‐observed thalamocortical (posterior thalamic radiation) injury, motor (corticospinal tract) injury, and sensorimotor function.

Diffusion tensor imaging of periventricular leukomalacia shows affected sensory cortex white matter pathways

Abstract—The authors used diffusion-tensor imaging to examine central white matter pathways in two children with spastic quadriplegic cerebral palsy. Corticospinal tracts projecting from cortex to brainstem resembled controls. In contrast, posterior regions of the corpus callosum, internal capsule, and corona radiata were markedly reduced, primarily in white matter fibers connected to sensory cortex. These findings suggest that the motor impairment in periventricular leukomalacia may, in part, reflect disruption of sensory connections outside classic pyramidal motor pathways.

Atlas-Based Analysis of Neurodevelopment from Infancy to Adulthood Using Diffusion Tensor Imaging and Applications for Automated Abnormality Detection

Quantification of normal brain maturation is a crucial step in understanding developmental abnormalities in brain anatomy and function. The aim of this study was to develop atlas-based tools for time-dependent quantitative image analysis, and to characterize the anatomical changes that occur from 2years of age to adulthood. We used large deformation diffeomorphic metric mapping to register diffusion tensor images of normal participants into the common coordinates and used a pre-segmented atlas to segment the entire brain into 176 structures. Both voxel- and atlas-based analyses reported a structure that showed distinctive changes in terms of its volume and diffusivity measures. In the white matter, fractional anisotropy (FA) linearly increased with age in logarithmic scale, while diffusivity indices, such as apparent diffusion coefficient (ADC), and axial and radial diffusivity, decreased at a different rate in several regions. The average, variability, and the time course of each measured parameter are incorporated into the atlas, which can be used for automated detection of developmental abnormalities. As a demonstration of future application studies, the brainstem anatomy of cerebral palsy patients was evaluated and the altered anatomy was delineated.

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

BACKGROUND AND PURPOSE: Conventional MR imaging shows evidence of brain injury and/or maldevelopment in 70%–90% of children with cerebral palsy (CP), though its capability to identify specific white matter tract injury is limited. The great variability of white matter lesions in CP already demonstrated by postmortem studies is thought to be one of the reasons why response to treatment is so variable. Our hypothesis is that diffusion tensor imaging (DTI) is a suitable technique to provide in vivo characterization of specific white matter tract lesions in children with CP associated with periventricular leukomalacia (PVL). MATERIALS AND METHODS: In this study, 24 children with CP associated with PVL and 35 healthy controls were evaluated with DTI. Criteria for identification of 26 white matter tracts on the basis of 2D DTI color-coded maps were established, and a qualitative scoring system, based on visual inspection of the tracts in comparison with age-matched controls, was used to grade the severity of abnormalities. An ordinal grading system (0 = normal, 1 = abnormal, 2 = severely abnormal or absent) was used to score each white matter tract. RESULTS: There was marked variability in white matter injury pattern in patients with PVL, with the most frequent injury to the retrolenticular part of the internal capsule, posterior thalamic radiation, superior corona radiata, and commissural fibers. CONCLUSION: DTI is a suitable technique for in vivo assessment of specific white matter lesions in patients with PVL and, thus, a potentially valuable diagnostic tool. The tract-specific evaluation revealed a family of tracts that are highly susceptible in PVL, important information that can potentially be used to tailor treatment options in the future.

Possible Mechanisms in Infants for Selective Basal Ganglia Damage From Asphyxia, Kernicterus, or Mitochondrial Encephalopathies

Magnetic resonance imaging and neuropathologic studies have demonstrated remarkably selective patterns of injury to subregions of the basal ganglia in children. Examples are kernicterus and certain mitochondrial encephalopathies, which cause selective injury to the globus pallidus, and near-total perinatal asphyxia, which causes lesions in the putamen and thalamus. To explain the differential vulnerability of nuclei within millimeters of each other, we hypothesize that their locations within the neurotransmitter-specific circuitry of the basal ganglia motor loop are important. In severe hypoxic-ischemic encephalopathy, excitatory glutamatergic pathways into the putamen and thalamus are overactive, but the globus pallidus might be protected because its activity is silenced by inhibitory neuronal activity. In contrast, the relatively high resting neuronal activity in the globus pallidus might make it more vulnerable to less intense, subacute oxidative stresses from mitochondrial toxins such as bilirubin or from genetic mitochondrial disorders. This hypothesis has implications for designing neuroprotective therapies and for treating associated chronic movement disorders. (J Child Neurol 2000;15:588-591).

Clinical Adaptive Test/Clinical Linguistic Auditory Milestone Scale in early cognitive assessment.

Correlations between the Clinical Adaptive Test/Clinical Linguistic Auditory Milestone Scale (CAT/CLAMS) and the Bayley Scales of Infant Development--Mental Scale (BSID) were examined in 61 infants and toddlers with suspected developmental delay. Highly significant correlations were found between the two instruments. Gender, race, and gestational age did not influence the relationship between CAT/CLAMS and BSID scores. The CAT/CLAMS was both sensitive (88%) and specific (67%) for mental retardation (BSID < 70). The CAT/CLAMS correlates with the BSID and can be used as an instrument for detecting cognitive delay.

Quantitative analysis of brain pathology based on MRI and brain atlases—Applications for cerebral palsy

We have developed a new method to provide a comprehensive quantitative analysis of brain anatomy in cerebral palsy patients, which makes use of two techniques: diffusion tensor imaging and automated 3D whole brain segmentation based on our brain atlas and a nonlinear normalization technique (large-deformation diffeomorphic metric mapping). This method was applied to 13 patients and normal controls. The reliability of the automated segmentation revealed close agreement with the manual segmentation. We illustrate some potential applications for individual characterization and group comparison. This technique also provides a framework for determining the impact of various neuroanatomic features on brain functions.

Age-dependent effects of trihexyphenidyl in extrapyramidal cerebral palsy

Trihexyphenidyl (Artane) is a centrally active muscarinic antagonist commonly used to treat patients with generalized dystonia. In a retrospective survey of 22 consecutive children with extrapyramidal cerebral palsy, we evaluated trihexyphenidyl on upper extremity and lower extremity function, expressive language, and drooling. Functional changes were assessed using a parental questionnaire (rating scale 1-5: from 1 = little or no change to 5 = tremendous change, with scores in either a positive or negative direction). Improvements of +4 or +5 were reported in eight children for upper extremity function, in eight children for verbal expressive language, in five for drooling, and in none for lower extremity function. Using bivariate linear regression modeling to investigate variables associated with treatment effects, there was a significant inverse relationship between age at initiation of medication and therapeutic response. Furthermore, beneficial responses were specific to upper-extremity function and expressive language. These results suggest that younger children are more likely to respond to trihexyphenidyl and that primary functional benefits include improved fine motor abilities and expressive language. A prospective masked study with a standardized clinical instrument is needed to confirm these findings.

Brain magnetic resonance imaging in suspected extrapyramidal cerebral palsy: Observations in distinguishing genetic-metabolic from acquired causes

Experienced clinicians recognize that some children who appear to have static cerebral palsy (CP) actually have underlying genetic-metabolic disorders. We report a series of patients with motor disorders seen in children with extrapyramidal CP in whom brain magnetic resonance imaging abnormalities provided important diagnostic clues in distinguishing genetic-metabolic disorders from other causes. One cause of static extrapyramidal CP, hypoxic-ischemic encephalopathy at the end of a term gestation, produces a characteristic pattern of hyperintense signal and atrophy in the putamen and thalamus. Other signal abnormalities and atrophy in the putamen, globus pallidus, or caudate can point to genetic-metabolic diseases, including disorders of mitochondrial and organic acid metabolism. Progress in understanding and treating genetic diseases of the developing brain makes it essential to diagnose disorders that masquerade as static CP. Brain magnetic resonance imaging is a useful diagnostic tool in the initial evaluation of children who appear to have CP.

Maternal estimates of developmental age in preschool children

OBJECTIVE To investigate the accuracy of maternal estimates of developmental age in preschool children with suspected developmental delay. METHODS In a sample of 139 preschool children, aged 5 to 60 months, mothers were asked before evaluation to estimate the developmental age of their child. Maternal estimates were converted to a developmental quotient (DQ) and compared with results from standardized tests of cognitive functioning, adaptive abilities, expressive and receptive language, and visual-motor skills. RESULTS A high correlation was found (r = 0.82; p < 0.0001) between maternal-estimate DQ and actual DQ (mean of test scores). Most mothers estimated within 15% of their childs actual functioning, and 84% of mothers estimated within +/- 5 months of actual functioning. Multiple regression found no factors that would identify mothers who were more or less accurate in estimating developmental age. Maternal-estimate DQ was sensitive (83%) and specific (83%) for mental retardation. CONCLUSION Maternal estimates provide an accurate measure of developmental functioning and could be successfully incorporated into routine developmental surveillance of preschool children.