Quantitative diffusion tensor imaging and intellectual outcomes in spina bifida: laboratory investigation

Thalamic connectivity topography in newborns with spina bifida: association with neurological functional level but not developmental outcome at 2 years

Spina bifida affects spinal cord and cerebral development, leading to motor and cognitive delay. We investigated whether there are associations between thalamocortical connectivity topography, neurological function, and developmental outcomes in open spina bifida. Diffusion tensor MRI was used to assess thalamocortical connectivity in 44 newborns with open spina bifida who underwent prenatal surgical repair. We quantified the volume of clusters formed based on the strongest probabilistic connectivity to the frontal, parietal, and temporal cortex. Developmental outcomes were assessed using the Bayley III Scales, while the functional level of the lesion was assessed by neurological examination at 2 years of age. Higher functional level was associated with smaller thalamo-parietal, while lower functional level was associated with smaller thalamo-temporal connectivity clusters (Bonferroni-corrected P < 0.05). Lower functional levels were associated with weaker thalamic temporal connectivity, particularly in the ventrolateral and ventral anterior nuclei. No associations were found between thalamocortical connectivity and developmental outcomes. Our findings suggest that altered thalamocortical circuitry development in open spina bifida may contribute to impaired lower extremity function, impacting motor function and independent ambulation. We hypothesize that the neurologic function might not merely be caused by the spinal cord lesion, but further impacted by the disruption of cerebral neuronal circuitry.

A spatio-temporal atlas of the developing fetal brain with spina bifida aperta

Background: Spina bifida aperta (SBA) is a birth defect associated with severe anatomical changes in the developing fetal brain. Brain magnetic resonance imaging (MRI) atlases are popular tools for studying neuropathology in the brain anatomy, but previous fetal brain MRI atlases have focused on the normal fetal brain. We aimed to develop a spatio-temporal fetal brain MRI atlas for SBA. Methods: We developed a semi-automatic computational method to compute the first spatio-temporal fetal brain MRI atlas for SBA. We used 90 MRIs of fetuses with SBA with gestational ages ranging from 21 to 35 weeks. Isotropic and motion-free 3D reconstructed MRIs were obtained for all the examinations. We propose a protocol for the annotation of anatomical landmarks in brain 3D MRI of fetuses with SBA with the aim of making spatial alignment of abnormal fetal brain MRIs more robust. In addition, we propose a weighted generalized Procrustes method based on the anatomical landmarks for the initialization of the atlas. The proposed weighted generalized Procrustes can handle temporal regularization and missing annotations. After initialization, the atlas is refined iteratively using non-linear image registration based on the image intensity and the anatomical land-marks. A semi-automatic method is used to obtain a parcellation of our fetal brain atlas into eight tissue types: white matter, ventricular system, cerebellum, extra-axial cerebrospinal fluid, cortical gray matter, deep gray matter, brainstem, and corpus callosum. Results: An intra-rater variability analysis suggests that the seven anatomical land-marks are sufficiently reliable. We find that the proposed atlas outperforms a normal fetal brain atlas for the automatic segmentation of brain 3D MRI of fetuses with SBA. Conclusions: We make publicly available a spatio-temporal fetal brain MRI atlas for SBA, available here:  https://doi.org/10.7303/syn25887675. This atlas can support future research on automatic segmentation methods for brain 3D MRI of fetuses with SBA.

The impact of cerebral anomalies on cognitive outcome in patients with spina bifida: A systematic review

BACKGROUND

Spina bifida is the most common congenital birth defect affecting the central nervous system. Given the frequent association of cerebral anomalies, spina bifida is not a single developmental abnormality of the central nervous system. Patients with spina bifida typically perform below average on cognitive tasks. It has been hypothesized that associated cerebral anomalies as well negatively affect cognition in spina bifida patients.

OBJECTIVE

This study aims to review the impact of cerebral anomalies on cognitive outcome in patients with spina bifida.

METHODS

A systematic search of multiple databases, including Pubmed, Embase, Web of Science and The Cochrane Central Register of Controlled Trials, was performed. All relevant primary research articles were included. All included articles were methodologically evaluated using a critical appraisal checklist.

RESULTS

In total 27 articles were included in this systematic review. A significant impact of different cerebral anomalies on cognition was found. More specifically, hydrocephalus, Chiari malformation type II and anomalies of the corpus callosum, central executive network, default mode network, cortical thickness and gyrification, fornix, grey matter volume and total brain volume were found to have a significant impact on cognitive outcome. The presence of a CSF shunt was also negatively associated with cognition. The results on Chiari malformation type II decompression and CSF shunt complications are inconsistent.

CONCLUSION

Associated cerebral anomalies have a significant impact on cognitive outcome in patients with spina bifida. The interrelatedness of the different cerebral anomalies makes it difficult to distinguish their individual impact on cognition.

Intelligence Quotient in Patients with Myelomeningocele: A Review

It has been proposed that hydrocephalus in children with myelomeningocele (MMC) can indicate a low intelligence quotient (IQ). Others have argued that it is not the mere presence of hydrocephalus but the superimposition of cerebrospinal fluid (CSF) infections, multiple shunt procedures, and other CNS complications that lead to the lowering of IQ in these patients.

In this paper, we review the literature to clarify the information about IQ in patients with MMC and whether it changes after infections and shunt procedures. We have also considered the other factors that could be involved in the IQ development of these patients and the differences revealed by the brain imaging of individuals with MMC.

The consensus remains that patients with MMC, with or without complications, tend to have a lower IQ than those without MMC. Hydrocephalus appears to decrease the IQ further in MMC patients. Some have proposed that prenatal repair of the MMC lesion reduces the need for ventricular shunting after birth, thus decreasing the risk of shunt complications such as a CNS infection, which can have a negative effect on IQ. More studies are needed to assess other risk factors (apart from folate deficiency) and genetic factors that could contribute to the development of MMC and their possible effects on patient IQ.

Ventricular volume and neurocognitive outcome after endoscopic third ventriculostomy: is shunting a better option? A review

BACKGROUND

Shunts are generally associated with a smaller post-treatment ventricular size in comparison to endoscopic third ventriculostomy (ETV).

METHODS

To determine whether such a difference in ventricular size has neurocognitive implications, we reviewed the current literature pertaining to the (1) neurocognitive sequelae of hydrocephalus, (2) neurocognitive outcome after ETV, (3) extent of reversal of neurocognitive changes associated with hydrocephalus after shunting, and (4) data on correlation between post-treatment ventricular volume and neurocognitive outcome after ETV.

RESULTS

Collectively, the results of the available studies should call into question the correlation between the residual postoperative ventricular volume and neurocognitive outcome.

CONCLUSION

The available literature is so far in support of ETV as a valid and effective treatment modality in hydrocephalic patients. No sufficient evidence is available to justify resorting to shunting on the premise that it is associated with a better neurocognitive outcome.

Gray matter integrity within regions of the dorsolateral prefrontal cortical-subcortical network predicts executive function and fine motor dexterity in spina bifida

OBJECTIVES

This study examined microstructural properties of cortical and subcortical gray matter components of the dorsolateral prefrontal (DLPFC) cortical-subcortical circuit in relation to parent-rated executive function and fine motor dexterity performance in youth with spina bifida myelomeningocele (SBM). Aberrant gray matter integrity of the DLPFC, basal ganglia nuclei, and thalamus were hypothesized to differentially relate to neurobehavioral outcomes.

METHODS

Forty-nine youth between 8 and 18 years (M = 12.34) old with SBM underwent a 3T MRI including diffusion tensor imaging. Neurobehavioral measures of parent-rated executive function and fine motor dexterity were obtained from a standardized neuropsychological evaluation. Relations among indices of gray matter microstructural integrity (mean diffusivity [MD], fractional anisotropy [FA], cortical thickness) and neurobehavior were examined using 3 correlational methods to enhance reliability of brain-behavior relations.

RESULTS

In SBM, higher FA values in the caudate were associated with poorer behavioral regulation. Higher FA values in the putamen and greater DLPFC thickness were both associated with poorer fine motor dexterity.

CONCLUSION

Behavioral regulation and FA in the caudate related to behavioral inhibition in SBM. Similarly, associations between fine motor dexterity and indices of gray matter integrity in the putamen and DLPFC support fronto-striatal involvement in motor control in SBM. Examination of these neurobehavioral correlates revealed a pattern of attenuated behavioral impairments when gray matter structure was more similar to that of typically developing youth. (PsycINFO Database Record

Long-term neurofunctional outcome, executive functioning, and behavioral adaptive skills following fetal myelomeningocele surgery

BACKGROUND

Myelomeningocele (MMC) represents the first nonlethal anomaly to be treated by prenatal intervention. Case series and a prospective, randomized study show that fetal surgery for MMC before 26 weeks' gestation may preserve neurological function. Long-term follow-up is a fundamental component to evaluate the overall efficacy of any new medical or surgical procedure. To further delineate the long-term impact of fMMC surgery, we continued to follow children treated in our institution before the Management of Myelomeningocele Study trial by the means of parental questionnaires to assess changes in functional, developmental, and cognitive status as these unique patients grow older.

OBJECTIVE

The objective of the study was to evaluate the long-term neurological outcome, executive functioning (EF), and behavioral adaptive skills (BAS) following fetal myelomeningocele (fMMC) surgery.

STUDY DESIGN

Prior to the Management of Myelomeningocele Study trial, 54 patients underwent fMMC surgery at our institution. Parents of 42 children (78%) participated in structured questionnaires focusing on neurofunctional outcome. EF and BAS were measured by the Behavior Rating Inventory of Executive Function (BRIEF) and the Adaptive Behavioral Assessment System II. The BRIEF is organized into 3 primary indices including the following: Global Executive Composite, Metacognition Index, and Behavioral Regulation Index. The Adaptive Behavioral Assessment System II results in a general adaptive composite score. Based on SD intervals, EF and BAS were categorized as being average, borderline, or impaired.

RESULTS

At a median follow-up age of 10 years (range, 8-14 years), 33 (79%) are community ambulators, 3 (9%) are household ambulators, and 6 (14%) are wheelchair dependent. Preschool ambulation was predictive of long-term ambulation (P < .01), whereas the need for tethered cord surgery was associated with persistent deterioration of ambulatory status (P = .007). Normal bladder function was found in 26%. Although the majority scored within the average range for the Behavioral Regulation Index, Metacognition Index, and Global Executive Composite indices, significantly more children who had fMMC surgery had deficits in EF in all 3 BRIEF indices compared with the population norms. The general adaptive composite scores were also more likely to fall below average following fMMC surgery. Normal early neurodevelopmental outcomes were predictive of normal EF and BAS (P < .01). Need for shunting was associated with a significant impairment of BAS (P = .02).

CONCLUSION

The present study suggests that fMMC surgery improves long-term functional outcome. The majority of fMMC children can successfully complete everyday tasks at home and at school. Abnormalities of BAS appear to be more common than impairments in EF and therefore offer an area for early screening and interventional therapy for these at-risk children. Non-shunted fMMC children with normal early neurodevelopmental outcome are less likely to experience problems with EF and BAS. fMMC surgery improves long-term ambulatory status. Symptomatic spinal cord tethering with or without intradural inclusion cyst is associated with functional loss. More than expected fMMC children are continent, but bowel and bladder control continue to be an ongoing challenge for the fMMC children.

Structural differences in basal ganglia of elite running versus martial arts athletes: a diffusion tensor imaging study

The aim of this study was to use diffusion tensor imaging (DTI) to characterize and compare microscopic differences in white matter integrity in the basal ganglia between elite professional athletes specializing in running and martial arts. Thirty-three young adults with sport-related skills as elite professional runners (n = 11) or elite professional martial artists (n = 11) were recruited and compared with non-athletic and healthy controls (n = 11). All participants underwent health- and skill-related physical fitness assessments. Fractional anisotropy (FA) and mean diffusivity (MD), the primary indices derived from DTI, were computed for five regions of interest in the bilateral basal ganglia, including the caudate nucleus, putamen, globus pallidus internal segment (GPi), globus pallidus external segment (GPe), and subthalamic nucleus. Results revealed that both athletic groups demonstrated better physical fitness indices compared with their control counterparts, with the running group exhibiting the highest cardiovascular fitness and the martial arts group exhibiting the highest muscular endurance and flexibility. With respect to the basal ganglia, both athletic groups showed significantly lower FA and marginally higher MD values in the GPi compared with the healthy control group. These findings suggest that professional sport or motor skill training is associated with changes in white matter integrity in specific regions of the basal ganglia, although these positive changes did not appear to depend on the type of sport-related motor skill being practiced.

Differential vulnerability of white matter structures to experimental infantile hydrocephalus detected by diffusion tensor imaging

PURPOSE

The differential vulnerability of white matter (WM) to acute and chronic infantile hydrocephalus and the related effects of early and late reservoir treatment are unknown, but diffusion tensor imaging (DTI) could provide this information. Thus, we characterized WM integrity using DTI in a clinically relevant model.

METHODS

Obstructive hydrocephalus was induced in 2-week-old felines by intracisternal kaolin injection. Ventricular reservoirs were placed 1 (early) or 2 (late) weeks post-kaolin and tapped frequently based solely on neurological deficit. Hydrocephalic and age-matched control animals were sacrificed 12 weeks postreservoir. WM integrity was evaluated in the optic system, corpus callosum, and internal capsule prereservoir and every 3 weeks using DTI. Analyses were grouped as acute (<6 weeks) or chronic (≥6 weeks).

RESULTS

In the corpus callosum during acute stages, fractional anisotropy (FA) decreased significantly with early and late reservoir placement (p = 0.0008 and 0.0008, respectively), and diffusivity increased significantly in early (axial, radial, and mean diffusivity, p = 0.0026, 0.0012, and 0.0002, respectively) and late (radial and mean diffusivity, p = 0.01 and 0.0038, respectively) groups. Chronically, the corpus callosum was thinned and not detectable by DTI. FA was significantly lower in the optic chiasm and tracts (p = 0.0496 and 0.0052, respectively) with late but not early reservoir placement. In the internal capsule, FA in both reservoir groups increased significantly with age (p < 0.05) but diffusivity remained unchanged.

CONCLUSIONS

All hydrocephalic animals treated with intermittent ventricular reservoir tapping demonstrated progressive ventriculomegaly. Both reservoir groups demonstrated WM integrity loss, with the CC the most vulnerable and the optic system the most resilient.

Structure, integrity, and function of the hypoplastic corpus callosum in spina bifida myelomeningocele

Although there are many studies of people with complete or partial hypogenesis of the corpus callosum (CC), little is understood about the hypoplastic CC in which all structures are present but thinned. Spina bifida myelomeningocele (SBM) is a model organism for such studies because many have either a hypogenetic or hypoplastic CC. We used diffusion tensor tractography (DTT) to evaluate the hypoplastic CC in SBM and its relation to interhemispheric functions and intelligence quotient (IQ). Participants were individuals with SBM and an intact or hypoplastic CC (n=28), who were compared to a typically developing comparison group (n=32). Total and regional DTT volume and integrity measures (fractional anisotropy, axial diffusivity, and radial diffusivity) of the CC were related to measures of intelligence (IQ), bimanual motor functioning, and dichotic auditory performance. As predicted, DTT showed variations in volume and integrity that were maximized in the entire CC and the posterior CC. IQ correlated with entire CC volume, anterior and posterior regional CC volumes, and also with measures of integrity. Bimanual motor functioning correlated with the anterior and posterior volumes of the CC but not with any integrity measures. Axial diffusivity in the posterior CC was negatively correlated with right ear dichotic listening performance. The hypoplastic CC is not macrostructurally or microstructurally intact in SBM, even when it appears radiologically intact. Both volume and integrity of the posterior regions were related to reductions in IQ and to interhemispheric processing. These findings may transfer to other disorders characterized by a hypoplastic CC.

Anatomical and diffusion MRI of deep gray matter in pediatric spina bifida

Individuals with spina bifida myelomeningocele (SBM) exhibit brain abnormalities in cortical thickness, white matter integrity, and cerebellar structure. Little is known about deep gray matter macro- and microstructure in this population. The current study utilized volumetric and diffusion-weighted MRI techniques to examine gray matter volume and microstructure in several subcortical structures: basal ganglia nuclei, thalamus, hippocampus, and amygdala. Sixty-six children and adolescents (ages 8–18; M = 12.0, SD = 2.73) with SBM and typically developing (TD) controls underwent T₁- and diffusion-weighted neuroimaging. Microstructural results indicated that hippocampal volume was disproportionately reduced, whereas the putamen volume was enlarged in the group with SBM. Microstructural analyses indicated increased mean diffusivity (MD) and fractional anisotropy (FA) in the gray matter of most examined structures (i.e., thalamus, caudate, hippocampus), with the putamen exhibiting a unique pattern of decreased MD and increased FA. These results provide further support that SBM differentially disrupts brain regions whereby some structures are volumetrically normal whereas others are reduced or enlarged. In the hippocampus, volumetric reduction coupled with increased MD may imply reduced cellular density and aberrant organization. Alternatively, the enlarged volume and significantly reduced MD in the putamen suggest increased density.

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Spina bifida resulted in reduced hippocampal and enlarged putamen volumes.

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Spina bifida resulted in reduced MD and increased FA in the putamen.

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Periventricular regions were differentiated by increased MD and FA in spina bifida.

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Spina bifida resulted in greater FA for all regions, except the hippocampus.

Age, plasticity, and homeostasis in childhood brain disorders

It has been widely accepted that the younger the age and/or immaturity of the organism, the greater the brain plasticity, the young age plasticity privilege. This paper examines the relation of a young age to plasticity, reviewing human pediatric brain disorders, as well as selected animal models, human developmental and adult brain disorder studies. As well, we review developmental and childhood acquired disorders that involve a failure of regulatory homeostasis. Our core arguments are as follows:

Functional significance of atypical cortical organization in spina bifida myelomeningocele: relations of cortical thickness and gyrification with IQ and fine motor dexterity

The cortex in spina bifida myelomeningocele (SBM) is atypically organized, but it is not known how specific features of atypical cortical organization promote or disrupt cognitive and motor function. Relations of deviant cortical thickness and gyrification with IQ and fine motor dexterity were investigated in 64 individuals with SBM and 26 typically developing (TD) individuals, aged 8-28 years. Cortical thickness and 3D local gyrification index (LGI) were quantified from 33 cortical regions per hemisphere using FreeSurfer. Results replicated previous findings, showing regions of higher and lower cortical thickness and LGI in SBM relative to the TD comparison individuals. Cortical thickness and LGI were negatively associated in most cortical regions, though less consistently in the TD group. Whereas cortical thickness and LGI tended to be negatively associated with IQ and fine motor outcomes in regions that were thicker or more gyrified in SBM, associations tended to be positive in regions that were thinner or less gyrified in SBM. The more deviant the levels of cortical thickness and LGI-whether higher or lower relative to the TD group-the more impaired the IQ and fine motor outcomes, suggesting that these cortical atypicalities in SBM are functionally maladaptive, rather than adaptive.

Decreased activation and increased lateralization in brain functioning for selective attention and response inhibition in adolescents with spina bifida

We used functional magnetic resonance imaging to evaluate functional activity in the brain of adolescents with spina bifida when performing selective attention and response inhibition tasks. We then compared the results to that of age-matched controls. Our results showed that adolescents with spina bifida had decreased frontal and superior parietal activation and more apparently low involvement of left brain hemisphere during these tasks. Our results indicated activation deficits and possibly abnormal functional organization in adolescents with spina bifida and associated pathologies such as hydrocephalus.

Diffusion tensor imaging evaluation of white matter in adolescents with myelomeningocele and Chiari II malformation

BACKGROUND

Macrostructural abnormalities in cerebral white matter in patients with myelomeningocele are well known, but microstructural abnormalities are not as well studied.

OBJECTIVE

The aim of this study was to evaluate cerebral white matter in adolescents with myelomeningocele using diffusion tensor imaging (DTI), and to investigate the effects of ventricular dilation and CSF shunt presence on white matter microstructure in these patients.

MATERIALS AND METHODS

DTI and T1-weighted 3-D (T1-3-D) MRI were performed on nine adolescents with myelomeningocele and Chiari II malformation and nine age-matched controls. The fractional anisotropy (FA) and mean diffusivity (MD) values were measured and compared.

RESULTS

Significantly decreased FA and increased MD values were observed in most white matter regions and fibers in adolescents with myelomeningocele compared to controls. Further analysis in patients revealed significant changes in DTI parameters in hemispheres with enlarged lateral ventricles compared to those with normal ventricle size. In addition, a significant difference in FA values in the posterior limb of the internal capsule was found in the comparison of hemispheres in patients with or without CSF shunt catheters.

CONCLUSION

This study revealed widespread microstructural abnormalities in white matter in adolescents with myelomeningocele and Chiari II malformation. Ventricular dilation may have additional effects on white matter microstructure in this patient population. CSF shunt diversion effects on white matter may be multifactorial and need further investigation.

Diffusion tensor imaging following shunt in a patient with hydrocephalus

We report on a patient with hydrocephalus who was evaluated by diffusion tensor imaging (DTI) follow-up study before and after a shunt operation. A 48-year-old male patient and 6 age-matched control subjects were evaluated. The patient presented with hydrocephalus due to hemorrhage caused by the rupture of a right middle cerebral artery bifurcation aneurysm. Three longitudinal DTIs were acquired from the patient (pre-shunt, post-shunt 2 weeks, and post-shunt 8 weeks). The fractional anisotrophy values in the adjacent structures of the lateral ventricle, which were increased before the shunt operation, were decreased after the shunt operation. We think that DTI could be a useful tool for the evaluation of hydrocephalus.

Cognitive functions correlate with diffusion tensor imaging metrics in patients with spina bifida cystica

PURPOSE

Spina bifida cystica (SBC) is a group of neurodevelopmental defects caused by improper neural tube closure, which may be responsible for deficits in cognitive functions. The purpose of this study was to examine changes in normal appearing deep gray and white matter brain regions in SBC patients compared with controls through diffusion tensor imaging (DTI) and correlate these changes with neuropsychometric tests.

METHODS

Conventional magnetic resonance imaging and neuropsychometric tests were performed on 13 patients and ten controls. DTI-derived fractional anisotropy (FA) and mean diffusivity (MD) were quantified in different brain regions in controls and patients.

RESULTS

Significantly decreased FA was observed in caudate nuclei, putamen, genu, splenium, and increased FA was found in middle cerebellar peduncle (MCP) in patients compared with controls. We observed significantly increased MD in genu and splenium. However, increased MD was found in fornix of patients compared with controls. Majority of neuropsychological tests were found to be significantly impaired and some of these showed significant correlation with DTI metrics in genu, splenium, and MCP in these patients.

CONCLUSIONS

We conclude that DTI metrics are significantly abnormal in deep gray matter nuclei, genu, splenium, and MCP in SBC patients and may provide microstructural basis for neuropsychological abnormalities in these patients.

Cerebellar motor function in spina bifida meningomyelocele

Spina bifida meningomyelocele (SBM), a congenital neurodevelopmental disorder, involves dysmorphology of the cerebellum, and its most obvious manifestations are motor deficits. This paper reviews cerebellar neuropathology and motor function across several motor systems well studied in SBM in relation to current models of cerebellar motor and timing function. Children and adults with SBM have widespread motor deficits in trunk, upper limbs, eyes, and speech articulators that are broadly congruent with those observed in adults with cerebellar lesions. The structure and function of the cerebellum are correlated with a range of motor functions. While motor learning is generally preserved in SBM, those motor functions requiring predictive signals and precise calibration of the temporal features of movement are impaired, resulting in deficits in smooth movement coordination as well as in the classical cerebellar triad of dysmetria, ataxia, and dysarthria. That motor function in individuals with SBM is disordered in a manner phenotypically similar to that in adult cerebellar lesions, and appears to involve similar deficits in predictive cerebellar motor control, suggests that age-based cerebellar motor plasticity is limited in individuals with this neurodevelopmental disorder.

Preschool neurodevelopmental outcome of children following fetal myelomeningocele closure

OBJECTIVE

We sought to investigate the preschool neurodevelopmental outcomes of children following fetal myelomeningocele (fMMC) surgery.

STUDY DESIGN

Prior to the Management of Myelomeningocele Study trial, 54 children underwent fMMC closure at our institution. Thirty (56%) returned at 5 years of age for standardized neurocognitive examination. Scores were grouped as high-average, average, mildly delayed, and severely delayed by SD intervals.

RESULTS

Mean verbal intelligence quotient (VIQ), performance intelligence quotient (PIQ), and full intelligence quotient (FIQ) scores were within normal population range. High-average or average scores for VIQ, PIQ, FIQ, and processing speed were found in 93%, 90%, 90%, and 60%, respectively. Mean FIQ and processing speed of nonshunted children were significantly higher than for those who required shunt placement (P=.02 and P=.01, respectively). Mean VIQ and PIQ tended to be higher in nonshunted fMMC children (P=.05).

CONCLUSION

The majority of fMMC children in this highly selective population had average preschool neurodevelopmental scores. fMMC children who did not require shunt placement were more likely to have better scores.

A diffusion tensor imaging study of deep gray and white matter brain maturation differences between patients with spina bifida cystica and healthy controls

The aim of this study was to use diffusion tensor imaging (DTI) to identify differences in the maturation of deep gray matter (GM) and white matter (WM) between patients with spina bifida cystica (SBC) (n=29) with normal-appearing brains on conventional MRI, and age-matched and sex-matched healthy control participants (n=33). Changes in DTI metrics were calculated using a log-linear regression model. We observed increasing fractional anisotropy (FA) with age in the occipital, fornix, cingulum and middle cerebellar peduncles and decreasing FA with age in the genu and splenium of the corpus callosum (CC) and caudate nuclei in patients compared to controls. Increasing FA values in some of the WM structures probably represent faulty WM maturation, whereas decreasing FA values in the CC represents changes secondary to the affected WM fibers contributing to the CC. DTI changes in deep GM and WM in the absence of any abnormality on conventional MRI might provide the basis for cognitive decline in these patients.

Longitudinal comparison of pre- and postoperative diffusion tensor imaging parameters in young children with hydrocephalus

OBJECT

The goal in this study was to compare the integrity of white matter before and after ventriculoperitoneal (VP) shunt insertion by evaluating the anisotropic diffusion properties with the aid of diffusion tensor (DT) imaging in young children with hydrocephalus.

METHODS

The authors retrospectively identified 10 children with hydrocephalus who underwent both pre- and postoperative DT imaging studies. The DT imaging parameters (fractional anisotropy [FA], mean diffusivity, axial diffusivity, and radial diffusivity) were computed and compared longitudinally in the splenium and genu of the corpus callosum (gCC) and in the anterior and posterior limbs of the internal capsule (PLIC). The patients' values on DT imaging at the pre- and postshunt stages were compared with the corresponding age-matched controls as well as with a large cohort of healthy children in the database.

RESULTS

In the gCC, 7 of 10 children had abnormally low preoperative FA values, 6 of which normalized postoperatively. All 3 of the 10 children who had normal preoperative FA values had normal FA values postoperatively as well. In the PLIC, 7 of 10 children had abnormally high FA values, 6 of which normalized postoperatively, whereas the other one had abnormally low postoperative FA. Of the remaining 3 children, 2 had abnormally low preoperative FA values in the PLIC; this normalized in 1 patient after surgery. The other child had a normal preoperative FA value that became abnormally low postoperatively. When comparing the presurgery frequency of abnormally low, normal, and abnormally high FA values to those postsurgery, there was a statistically significant longitudinal difference in both gCC (p = 0.02) and PLIC (p = 0.002).

CONCLUSIONS

In this first longitudinal DT imaging study of young children with hydrocephalus, DT imaging anisotropy yielded abnormal results in several white matter regions of the brain, and trended toward normalization following VP shunt placement.

Anomalous development of brain structure and function in spina bifida myelomeningocele

Spina bifida myelomeningocele (SBM) is a specific type of neural tube defect whereby the open neural tube at the level of the spinal cord alters brain development during early stages of gestation. Some structural anomalies are virtually unique to individuals with SBM, including a complex pattern of cerebellar dysplasia known as the Chiari II malformation. Other structural anomalies are not necessarily unique to SBM, including altered development of the corpus callosum and posterior fossa. Within SBM, tremendous heterogeneity is reflected in the degree to which brain structures are atypical in qualitative appearance and quantitative measures of morphometry. Hallmark structural features of SBM include overall reductions in posterior fossa and cerebellum size and volume. Studies of the corpus callosum have shown complex patterns of agenesis or hypoplasia along its rostral-caudal axis, with rostrum and splenium regions particularly susceptible to agenesis. Studies of cortical regions have demonstrated complex patterns of thickening, thinning, and gyrification. Diffusion tensor imaging studies have reported compromised integrity of some specific white matter pathways. Given equally complex ocular motor, motor, and cognitive phenotypes consisting of relative strengths and weaknesses that seem to align with altered structural development, studies of SBM provide new insights to our current understanding of brain structure-function associations.

Caudate nuclei volume, diffusion tensor metrics, and T(2) relaxation in healthy adults and relapsing-remitting multiple sclerosis patients: implications for understanding gray matter degeneration

PURPOSE

To investigate the utility of caudate nuclei (CN) macro- and microstructural metrics as markers of gray matter degeneration in healthy adults and relapsing-remitting multiple sclerosis (RRMS) patients.

MATERIALS AND METHODS

The normal age- and pathology-related changes in caudate nuclei volume (CNV), the corresponding diffusion tensor metrics, and the T(2) relaxation times were measured in a cohort of 32 healthy adults (12 men/20 women; age range 21-59 years) and 32 age-matched RRMS patients (8 men/34 women; age range 21-57 years).

RESULTS

Smaller values in both the absolute CNV and the caudate volume ratio relative to the total intracranial volume (CNVp) were observed in the RRMS group relative to healthy controls. The fractional anisotropy (FA), based on the diffusion tensor imaging (DTI) of the CN increased with age in healthy adults (r = 0.52; P = 0.003) but not in patients (r = 0.28; P = 0.12). The caudate FA value was approximately 9% larger in RRMS patients relative to controls (P = 0.001). The mean diffusivity of the CN was greater in the RRMS group compared to controls (P = 0.02). The caudate T(2) relaxation times were smaller in the RRMS group relative to the control group (3% reduction, P = 0.05). T(2) relaxation times did not exhibit age-related changes (P > 0.35) in either cohort. Strong and significant correlations between CNVp and whole-brain lesion load (r = -0.48; P = 0.005) and whole-brain CSF fraction (r = -0.46; P = 0.01) were also noted.

CONCLUSION

These preliminary findings indicate that caudate DTI-derived metrics can serve as potential quantitative radiological markers of MS pathology.

Puppets, robots, critics, and actors within a taxonomy of attention for developmental disorders

This review proposes a new taxonomy of automatic and controlled attention. The taxonomy distinguishes among the role of the attendee (puppet and robot, critic and actor), the attention process (stimulus orienting vs. response control), and the attention operation (activation vs. inhibition vs. adjustment), and identifies cognitive phenotypes by which attention is overtly expressed. We apply the taxonomy to four childhood attention disorders: attention deficit hyperactivity disorder, spina bifida meningomyelocele, traumatic brain injury, and acute lymphoblastic leukemia. Variations in attention are related to specific brain regions that support normal attention processes when intact, and produce disordered attention when impaired. The taxonomy explains group differences in behavioral inattention, hyperactivity, and impulsiveness, as well as medication response. We also discuss issues relevant to theories of the cognitive and neural architecture of attention: functional dissociations within and between automatic and controlled attention; the relative importance of type of brain damage and developmental timing to attention profile; cognitive-energetic models of attention and white matter damage; temporal processing deficits, attention deficits and cerebellar damage; and the issue of cognitive phenotypes as candidate endophenotypes.