White matter abnormalities in children with idiopathic developmental delay

Reduced Cortical Complexity in Children with Developmental Delay in Saudi Arabia

INTRODUCTION

Developmental delay (DD) is a neurodevelopmental disorder characterized by delays in multiple domains. The investigation of brain structure in DD has been enhanced by advanced neuroimaging techniques that can identify regional surface deformities. Neuroimaging studies have identified structural brain abnormalities in individuals with DD, but research specific to the Saudi Arabian population is limited. In this study, we examine the neuroanatomical abnormalities in the cortical and subcortical regions of Saudi Arabian children with DD.

METHOD

A T1-weighted, 1-mm-thick MRI was used to acquire structural brain images of 29 children with DD and age-matched healthy controls.

RESULTS

Analysis of the MRI data revealed significant differences in several cortical and subcortical structures of gray matter (GM) and white matter (WM) in several brain regions of the DD group. Specifically, significant deformities were observed in the caudate nucleus, globus pallidus, frontal gyrus, pars opercularis, pars orbitalis, cingulate gyrus, and subcallosal gyrus. These findings suggest disrupted neurodevelopment in these regions, which may contribute to the cognitive, motor, and behavioral impairments commonly observed in individuals with DD.

CONCLUSIONS

The present study provides valuable insights into the neuroanatomical differences in Saudi Arabian children with DD. Our results provide evidence for cortical and subcortical abnormalities in DD. Deformities in the observed regions may contribute to cognitive impairment, emotional dysregulation, mood disorders, and language deficits commonly observed in DD. The structural analysis may enable the identification of neuroanatomical biomarkers to facilitate the early diagnosis or progression of DD. These results suggest that lower cortical complexity in DD children due to alterations in networks may play a critical role in early brain development.

Magnetic resonance imaging brain yield in developmental delay: A developing country perspective

BACKGROUND

Developmental delay (DD) is an important neuro-morbidity in children affecting the quality of life. MRI plays a crucial role by delineating the underlying structural, metabolic, and genetic abnormalities.

AIM

To determine the yield of MRI brain in delineating the various underlying abnormalities and etiological factors in children with DD and to correlate these findings with the clinical presentation.

METHODS

This cross-sectional study enrolled 50 children with the developmental delay between 6 months to 6 years of age.

OUTCOMES AND RESULTS

The mean age was 31.32 ± 20.56 months. The sensitivity of MRI was 72%. 81.3% of the children with microcephaly had abnormal MRI. The most common underlying etiology was hypoxic-ischemic encephalopathy (42%), followed by congenital/developmental defects and metabolic diseases (10% each). The most commonly involved region of the cerebral cortex was the occipital lobe (44%) because of the high occurrence of coexisting hypoglycemic brain injury, which is extremely common in developing countries and rare in developed countries, with 80% of them having visual abnormalities. Frontal lobe involvement was significantly more in children with abnormal motor findings and behavioral changes. Cortical grey matter abnormalities were significantly more in children with seizures.

CONCLUSION AND IMPLICATIONS

It is to be emphasized that children with developmental delays should be evaluated with MRI whenever possible. Apart from hypoxic-ischemic encephalopathy, other etiologies should also be looked for.

Characterization of MRI White Matter Signal Abnormalities in the Pediatric Population

(1) Background and Purpose: The aim of this study was to retrospectively characterize WMSAs in an unselected patient cohort at a large pediatric neuroimaging facility, in order to learn more about the spectrum of the underlying disorders encountered in everyday clinical practice. (2) Materials and Methods: Radiology reports of 5166 consecutive patients with standard brain MRI (2006-2018) were searched for predefined keywords describing WMSAs. A neuroradiology specialist enrolled patients with WMSAs following a structured approach. Imaging characteristics, etiology (autoimmune disorders, non-genetic hypoxic and ischemic insults, traumatic white matter injuries, no final diagnosis due to insufficient clinical information, "non-specific" WMSAs, infectious white matter damage, leukodystrophies, toxic white matter injuries, inborn errors of metabolism, and white matter damage caused by tumor infiltration/cancer-like disease), and age/gender distribution were evaluated. (3) Results: Overall, WMSAs were found in 3.4% of pediatric patients scanned at our and referring hospitals within the ten-year study period. The majority were found in the supratentorial region only (87%) and were non-enhancing (78% of CE-MRI). WMSAs caused by autoimmune disorders formed the largest group (23%), followed by "non-specific" WMSAs (18%), as well as non-genetic hypoxic and ischemic insults (17%). The majority were therefore acquired as opposed to inherited. Etiology-based classification of WMSAs was affected by age but not by gender. In 17% of the study population, a definite diagnosis could not be established due to insufficient clinical information (mostly external radiology consults). (4) Conclusions: An "integrated diagnosis" that combines baseline demographics, including patient age as an important factor, clinical characteristics, and additional diagnostic workup with imaging patterns can be made in the majority of cases.

Brain Magnetic Resonance Imaging-Based Evaluation of Pediatric Patients With Developmental Delay: A Cross-Sectional Study

Background

Developmental delay refers to the insufficient acquisition of age-appropriate developmental milestones. According to World Health Organization, approximately 5% of all children under the age of 14 years display some developmental disability.

Aim and objective

Our objective was to investigate the prevalence of abnormal magnetic resonance imaging (MRI) brain findings in pediatric patients with non-syndromic developmental delay and to establish the utility of MRI for the same.

Material and Method

This cross-sectional study prospectively enrolled 60 pediatric patients (three months to 12 years) and data were analyzed using SPSS software.

Result

Abnormalities on MRI were seen in 80% of cases, with findings indicating perinatal hypoxic insult (36.67%) being the most common, followed by structural abnormalities of the brain (20%). There was no significant difference in the prevalence of abnormal findings when classified by gender or age, or between global developmental delay (GDD) alone and GDD with epilepsy. However, perinatal hypoxic insult was significantly associated with GDD with epilepsy rather than GDD alone (p < 0.01).

Conclusion

In this study, brain MRI provides a high yield of abnormal findings and helps calculate the relative prevalence of various common etiologies in non-syndromic developmental delay. This study supports several international guidelines that include MRI as the first-line investigation for non-syndromic developmental delay.

Changes of Neural Pathways after Vojta Approach in a Child with Developmental Delay

The development of motor function is related to the development of neural pathways in the white matter. Children with developmental delay (DD) and hypotonia have reduced motor function, and their neural pathways are observed differently from those of typically developed children. We investigated changes in neural pathways through diffusion tensor imaging (DTI) after utilizing the Vojta approach. The participant was a child with DD and hypotonia, and had delayed motor function. Although he had no brain damage on magnetic resonance imaging findings, damage to the neural pathway was confirmed through DTI due to cytomegalovirus infection in the mother's womb. From 11 months of age, the Vojta approach was performed for a total of 8 months. In this study, we found that in CST, the left FA and right TV increased in follow-up DTI more than in the initial DTI. In CRP, Wallerian degeneration was observed in the left FA, MD, and TV in follow-up DTI. GMFM-88 improved after intervention. The structural change of neural pathways through the Vojta approach influenced the improvement of gross motor function. Therefore, it is thought that the Vojta approach can be suggested as a meaningful intervention for children with DD and hypotonia.

Congenital Hearing Loss Is Associated With a High Incidence of Central Nervous System Abnormalities

OBJECTIVE(S)

To assess the incidence of central nervous system abnormalities in pediatric subjects with sensorineural hearing loss (SNHL).

METHODS

One hundred forty-three pediatric subjects evaluated for SNHL at a single academic center from 2007 to 2014 were included and divided into eight diagnosis groups based on etiology of SNHL. One hundred forty-three age- and gender-matched control subjects with no known brain-related pathology or history of hearing loss were included as healthy controls for comparison. Two neuroradiologists independently evaluated magnetic resonance imaging (MRI) and computed tomography (CT) scans for each subject. Comparison of abnormal cerebral development was performed using an ordinal logistic regression model. Concordance between CT and MRI of the temporal bone was assessed using the kappa statistic.

RESULTS

The etiologies of hearing loss in our cohort were 37.8% genetic, 12.6% infectious, 1.4% ototoxin-induced, and 48.3% idiopathic. Brain MRI revealed cerebral developmental abnormalities in defined regions in >30% of the SNHL cohort, significantly more than in normal-hearing pediatric controls. The Sylvian fissure, Virchow-Robin spaces, and lateral ventricles were most commonly affected. In the temporal bone, the percentage of subjects with concordant findings on CT and MRI was ≥92% across all anatomical structures.

CONCLUSION

MRI revealed a high incidence of intracranial abnormalities, suggestive of aberrant development of auditory and nonauditory neural structures associated with SNHL. CT and MRI share a high degree of concordance in detecting temporal bone anomalies. Inclusion of MRI as part of the workup of congenital SNHL may facilitate the detection of developmental anomalies of the brain associated with SNHL.

Is Brain MRI Needed in Diagnostic Evaluation of Mild Intellectual Disability?

AIM

The purpose of our study was to suggest an imaging strategy and guidelines for the selection of the children with mild intellectual disability (ID) for magnetic resonance imaging (MRI), to avoid unnecessary imaging.

METHODS

The brain MRIs and patient reports of 471 children were reviewed for the imaging findings and ID severity. The correlation between the clinical and brain MRI findings was analyzed in the 305 children with mild ID.

RESULTS

Thirty-eight (12.5%) of the children with mild ID had significant abnormal brain MRI findings. Thirty-five of these had other neurological symptoms or diseases in addition to ID, which were an indication for brain MRI. In the logistic regression analysis, seizures (in patients without an epilepsy diagnosis), epilepsy, movement disorders, dysmorphia, encephalitis, traumatic brain injury, and abnormal head size were statistically significant symptoms or comorbidities associated with abnormal MRI findings. Only three children (1.0%) with mild ID had a significant MRI finding without any other clinical symptoms or disease.

CONCLUSION

Routine MRI in children with mild ID without specific neurological symptoms, dysmorphic features, or related diseases is not suggested for revealing an etiology of mild ID. Since children with ID usually need to be sedated for MRI, routine imaging in the diagnostic evaluation of mild ID should be carefully considered. Clinical examination, other symptoms, and related diseases should be carefully assessed to decide the need for MRI.

MRI Evaluation of Global Developmental Delay: A Retrospective Study

Introduction: Global developmental delay (GDD) is defined as a significant delay in one or more developmental domains. Aims and Objectives: To study the prevalence of normal and abnormal magnetic resonance imaging (MRI) in pediatric patients presenting with GDD, and how abnormal MRI helps in the diagnosis of children with GDD. Materials and Methods: This was a retrospective observational study conducted at the King Fahad Specialist Hospital Dammam. MRI of the brain was conducted on 170 patients who were referred by the Pediatric Neurology Department between February 2016 and April 2018. Results: Normal MRI findings were seen in 45.3% and 54.7% had abnormal findings. The ventricles and white matter, mainly the corpus callosum, were the most commonly affected anatomical structures. In 15 (16%) patients, MRI enabled a direct diagnosis, and in 22 (23.6%) MRI suggested a diagnosis which was confirmed by further investigation. Conclusion: The clinical diagnosis of GDD should not be the end point, but rather a springboard for an effective search for causal factors. MRI is the best investigation with a high yield in such patients.

Corpus Callosum: Molecular Pathways in Mice and Human Dysgeneses

The corpus callosum is the largest of the 3 telencephalic commissures in eutherian (placental) mammals. Although the anterior commissure, and the hippocampal commissure before being pushed dorsally by the expanding frontal lobes, cross through the lamina reuniens (upper part of the lamina terminalis), the callosal fibers need a transient interhemispheric cellular bridge to cross. This review describes the molecular pathways that initiate the specification of the cells comprising this bridge, the specification of the callosal neurons, and the repulsive and attractive guidance molecules that convey the callosal axons toward, across, and away from the midline to connect with their targets.

Systematic review of MRI findings in children with developmental delay or cognitive impairment

AIM

To summarize the reported rates of magnetic resonance imaging (MRI) abnormalities in children with isolated global developmental delay (GDD) or intellectual disability (ID).

METHOD

A literature search was conducted using electronic databases for studies reporting the rate of MRI abnormalities in children with clinically diagnosed ID or GDD and no other neurological signs, symptoms, or previously determined aetiology. All investigations with participants from birth to 18years were considered. Study quality was evaluated using the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (MAStARI) critical appraisal checklist items.

RESULTS

Eighteen cross sectional, and 11 case-controlled studies adhered to inclusion criteria. Reported rates of abnormalities ranged from 0% to 98%. When all subjects with developmental delay from all papers were considered (n=2299) the total percentage found to have abnormalities was 38%. Abnormalities led to an etiological diagnosis for delay in 7.9% of cases.

INTERPRETATION

Definitions of abnormalities varied widely between studies, and drastically different rates of abnormalities are reported. Currently available evidence is not of sufficient quality to make firm recommendations on the use of neuroimaging in ID or GDD but MRI should be considered for children that do not have a diagnosis after thorough clinical evaluation.

Development of human white matter fiber pathways: From newborn to adult ages

Major long-range white matter pathways (cingulum, fornix, uncinate fasciculus [UF], inferior fronto-occipital fasciculus [IFOF], inferior longitudinal fasciculus [ILF], thalamocortical [TC], and corpus callosal [CC] pathways) were identified in eighty-three healthy humans ranging from newborn to adult ages. We tracked developmental changes using high-angular resolution diffusion MR tractography. Fractional anisotropy (FA), apparent diffusion coefficient, number, length, and volume were measured in pathways in each subject. Newborns had fewer, and more sparse, pathways than those of the older subjects. FA, number, length, and volume of pathways gradually increased with age and reached a plateau between 3 and 5 years of age. Data were further analyzed by normalizing with mean adult values as well as with each subject's whole brain values. Comparing subjects of 3 years old and under to those over 3 years old, the studied pathways showed differential growth patterns. The CC, bilateral cingulum, bilateral TC, and the left IFOF pathways showed significant growth both in volume and length, while the bilateral fornix, bilateral ILF and bilateral UF showed significant growth only in volume. The TC and CC took similar growth patterns with the whole brain. FA values of the cingulum and IFOF, and the length of ILF showed leftward asymmetry. The fornix, ILF and UF occupied decreased space compared to the whole brain during development with higher FA values, likely corresponding to extensive maturation of the pathways compared to the mean whole brain maturation. We believe that the outcome of this study will provide an important database for future reference.

Magnetic resonance imaging (MRI) evaluation of developmental delay in pediatric patients

INTRODUCTION

Developmental delay is defined as significant delay in one or more developmental domains. Magnetic Resonance Imaging (MRI) is the best modality to investigate such patients. Evaluation of a child with developmental delay is important not only because it allows early diagnosis and treatment but also helpful for parental counseling regarding the outcome of their child and to identify any possible risk of recurrence in the siblings. Thus this study was undertaken to evaluate the developmental delay in Indian children which will help the clinicians in providing an estimation of the child's ultimate developmental potential and organize specific treatment requirement and also relieve parental apprehension.

AIMS AND OBJECTIVES

To study the prevalence of normal and abnormal MRI in pediatric patients presenting with developmental delay and further categorize the abnormal MRI based on its morphological features.

MATERIALS AND METHODS

It is a prospective, observational & descriptive study of MRI Brain in 81 paediatric patients (46 Males and 35 Females), aged between three months to 12 years; presenting with developmental delay in Deccan College of Medical Sciences, Hyderabad; over a period of three years (Sept 2011 to Sept 2014). MRI brain was done on 1.5T Siemens Magnetom Essenza & 0.35T Magnetom C with appropriate sequences and planes after making the child sleep/sedated/ anesthetized. Various anatomical structures like Ventricles, Corpus callosum, etc were systematically assessed. The MRI findings were divided into various aetiological subgroups.

RESULTS

Normal MRI findings were seen in 32% cases and 68% had abnormal findings of which the proportion of Traumatic/ Neurovascular Diseases, Congenital & Developmental, Metabolic and Degenerative, neoplastic and non specific were 31%, 17%, 10%, 2.5% and 7.5% respectively. The ventricles and white matter mainly the corpus callosum were the most commonly affected anatomical structures. The diagnostic yield was found to be 68% and higher yield was seen in patients presenting with developmental delay plus.

CONCLUSION

The clinical diagnosis of developmental delay should not be the end point, but rather a springboard for an effective search for causal factors. MRI is the best investigation with a high yield in such patients.

Use of the cross-translational model to study self-injurious behavior in human and nonhuman primates

Nonsuicidal self-injurious behavior occurs in the general human population, particularly among teenagers and young adults. Some rhesus macaques also develop self-injurious behavior (SIB) as adolescents or young adults. In both of these cases, the development of harmful behaviors is idiopathic, only coming to the attention of physicians or veterinarians after the disorder is established. Thus, a combination of retrospective, statistical, and empirical procedures are used to understand this disorder. Here, we identify concordances between macaques and humans across five different levels of analysis-(1) form and prevalence, (2) etiology, (3) triggering events, (4) function/maintenance, and (5) therapeutic intervention-and show the value of the cross-translational model (macaques to humans and humans to macaques) in understanding this phenomenon. Substantial concordance is present with respect to the range of severity, the presence of early life stress exposure, and emotional dysregulation. In the macaque model, additional information is available on the hypothalamic-pituitary-adrenal axis stress response system, possible genetic involvement, and the immediate contextual situations that appear to trigger or exacerbate SIB episodes. In contrast, considerably more information is available from human studies on the effectiveness of various treatment regimens. Veterinarians have drawn on this information to explore these therapeutic interventions in monkeys. We expect that models of SIB will continue to have cross-translational impact as scientists and practitioners move from preclinical to clinical research and treatment.

TM4SF20 ancestral deletion and susceptibility to a pediatric disorder of early language delay and cerebral white matter hyperintensities

White matter hyperintensities (WMHs) of the brain are important markers of aging and small-vessel disease. WMHs are rare in healthy children and, when observed, often occur with comorbid neuroinflammatory or vasculitic processes. Here, we describe a complex 4 kb deletion in 2q36.3 that segregates with early childhood communication disorders and WMH in 15 unrelated families predominantly from Southeast Asia. The premature brain aging phenotype with punctate and multifocal WMHs was observed in ~70% of young carrier parents who underwent brain MRI. The complex deletion removes the penultimate exon 3 of TM4SF20, a gene encoding a transmembrane protein of unknown function. Minigene analysis showed that the resultant net loss of an exon introduces a premature stop codon, which, in turn, leads to the generation of a stable protein that fails to target to the plasma membrane and accumulates in the cytoplasm. Finally, we report this deletion to be enriched in individuals of Vietnamese Kinh descent, with an allele frequency of about 1%, embedded in an ancestral haplotype. Our data point to a constellation of early language delay and WMH phenotypes, driven by a likely toxic mechanism of TM4SF20 truncation, and highlight the importance of understanding and managing population-specific low-frequency pathogenic alleles.

Optimizing MR imaging detection of type 2 focal cortical dysplasia: best criteria for clinical practice

BACKGROUND AND PURPOSE

Type 2 FCD is one of the main causes of drug-resistant partial epilepsy. Its detection by MR imaging has greatly improved surgical outcomes, but it often remains overlooked. Our objective was to determine the prevalence of typical MR imaging criteria for type 2 FCD, to provide a precise MR imaging pattern, and to optimize its detection.

MATERIALS AND METHODS

We retrospectively reviewed 1.5T MR imaging of 71 consecutive patients with histologically proved type 2 FCD. The protocol included millimetric 3D T1-weighted, 2D coronal and axial T2-weighted, and 2D or 3D FLAIR images. Two experienced neuroradiologists looked for 6 criteria: cortex thickening, cortical and subcortical signal changes, blurring of the GWM interface, the "transmantle" sign, and gyral abnormalities. The frequency of each sign and their combination were assessed. We compared the delay between epilepsy onset and surgery, taking into account the time of type 2 FCD detection by MR imaging.

RESULTS

Only 42 patients (59%) had positive MR imaging findings. In this group, a combination of at least 3 criteria was always found. Subcortical signal changes were constant. Three characteristic signs (cortical thickening, GWM blurring, and transmantle sign) were combined in 64% of patients, indicating that MR imaging can be highly suggestive. However, typical features of type 2 FCD were overlooked on initial imaging in 40% of patients, contributing to a delay in referral for surgical consideration (17 versus 11.5 years when initial MR imaging findings were positive).

CONCLUSIONS

A combination of 3 major MR imaging signs allows type 2 FCD to be recognized in clinical practice, thereby enabling early identification of candidates for surgery.

Development and dysgenesis of the cerebral cortex: malformations of cortical development

The cerebral cortex develops in several stages from a pseudostratified epithelium at 5 weeks to an essentially complete cortex at 47 weeks. Cortical connectivity starts with thalamocortical connections in the 3rd trimester only and continues until well after birth. Vascularity adapts to proliferation and connectivity. Malformations of cortical development are classified into disorders of specification, proliferation/apoptosis, migration, and organization. However, all processes are intermingled, as for example a dysplastic cell may migrate incompletely and not connect appropriately. However, this classification is convenient for didactic purposes as long as the complex interactions between the different processes are kept in mind.

[Mental retardation and ADHD]

Hyperactivity syndromes and disorders (ADHD and HKD) include the symptoms of overactivity, inattention, and impulsivity, which occur in many other mental disorders as well, including mental retardation (MR). It is not surprising that symptoms of ADHD occur significantly higher in children with learning disabilities. Dekker and Koot (2003) found a prevalence of 14.8 % for ADHD in Dutch children attending special schools, and Emerson (2003) reported rates of 8.7 % for HKD in children with global learning disability, representing a 10-fold increased risk compared to the prevalence of hyperactivity (0.9 %) in the general population sample. Yet only very few studies have been published concerning ADHD in children with mental retardation. Several features distinguish the diagnoses of ADHD and MR. In contrast to the limited knowledge about the differences and similarities of ADHD and MR, many studies considered stimulant medication as a pharmacological management strategy for children suffering from ADHD, MR, or both. According to these studies, psychostimulants may improve the target symptoms of hyperactivity, impulsivity, disinhibition, and inattention, albeit with caveats: ADHD symptoms in patients with MR may be less responsive to medical treatment than in patients without MR. Moreover, people with MR may be more susceptible to side effects.

Intelligenzminderung

Schwachsinn Der Gebrauch des Terminus »Schwachsinn« ist wegen seines globalen und wenig präzisen Charakters und durch seine historisch und umgangssprachlich bedingte sozial diskriminierende Tönung inzwischen in der wissenschaftlichen Literatur zu Recht weitgehend aufgegeben worden. In der Rechtsprechung speziell in der Forensik ist Schwachsinn als eine schuldausschließende bzw. schuldminderende juristische Kategorie ein nach wie vor gebräuchlicher Begriff.

Reduced cortical thickness in mental retardation

Mental retardation is a developmental disorder associated with impaired cognitive functioning and deficits in adaptive behaviors. Many studies have addressed white matter abnormalities in patients with mental retardation, while the changes of the cerebral cortex have been studied to a lesser extent. Quantitative analysis of cortical integrity using cortical thickness measurement may provide new insights into the gray matter pathology. In this study, cortical thickness was compared between 13 patients with mental retardation and 26 demographically matched healthy controls. We found that patients with mental retardation had significantly reduced cortical thickness in multiple brain regions compared with healthy controls. These regions include the bilateral lingual gyrus, the bilateral fusiform gyrus, the bilateral parahippocampal gyrus, the bilateral temporal pole, the left inferior temporal gyrus, the right lateral orbitofrontal cortex and the right precentral gyrus. The observed cortical thickness reductions might be the anatomical substrates for the impaired cognitive functioning and deficits in adaptive behaviors in patients with mental retardation. Cortical thickness measurement might provide a sensitive prospective surrogate marker for clinical trials of neuroprotective medications.

The corpus callosum, the other great forebrain commissures, and the septum pellucidum: anatomy, development, and malformation

There are three telencephalic commissures which are paleocortical (the anterior commissure), archicortical (the hippocampal commissure), and neocortical. In non-placental mammals, the neocortical commissural fibers cross the midline together with the anterior and possibly the hippocampal commissure, across the lamina reuniens (joining plate) in the upper part of the lamina terminalis. In placental mammals, a phylogenetically new feature emerged, which is the corpus callosum: it results from an interhemispheric fusion line with specialized groups of mildline glial cells channeling the commissural axons through the interhemispheric meninges toward the contralateral hemispheres. This concerns the frontal lobe mainly however: commissural fibers from the temporo-occipital neocortex still use the anterior commissure to cross, and the posterior occipito-parietal fibers use the hippocampal commissure, forming the splenium in the process. The anterior callosum and the splenium fuse secondarily to form the complete commissural plate. Given the complexity of the processes involved, commissural ageneses are many and usually associated with other diverse defects. They may be due to a failure of the white matter to develop or to the commissural neurons to form or to migrate, to a global failure of the midline crossing processes or to a selective failure of commissuration affecting specific commissural sites (anterior or hippocampal commissures, anterior callosum), or specific sets of commissural axons (paleocortical, hippocampal, neocortical commissural axons). Severe hemispheric dysplasia may prevent the axons from reaching the midline on one or both sides. Besides the intrinsically neural defects, midline meningeal factors may prevent the commissuration as well (interhemispheric cysts or lipoma). As a consequence, commissural agenesis is a malformative feature, not a malformation by itself. Good knowledge of the modern embryological data may allow for a good understanding of a specific pattern in a given individual patient, paving the way for better clinical correlation and genetic counseling.

Reduced cortical folding in mental retardation

BACKGROUND AND PURPOSE

MR is a developmental disorder associated with impaired cognitive functioning and deficits in adaptive behavior. With a 2D region of interest-based GI, a preliminary study reported significantly reduced gyrification in the prefrontal lobe in MR. The purpose of this study was to further investigate the abnormalities of cortical gyrification in MR and to explore the possible causes of these abnormalities.

MATERIALS AND METHODS

Thirteen patients with MR and 26 demographically matched healthy controls were included in this study. A 3D surface-based lGI was calculated as a measure to quantify gyrification. Then vertex-by-vertex contrasts of lGI were performed between patients with MR and healthy controls.

RESULTS

Statistical analysis showed that patients with MR had significantly reduced lGI in multiple brain regions compared with healthy controls. These regions include the lateral and medial prefrontal cortices, the right superior temporal gyrus, the left superior parietal lobe, the bilateral insular and adjacent cortices, and the visual and motor cortices.

CONCLUSIONS

The observed abnormal pattern of cortical gyrification revealed by significant reduction of lGI in multiple brain regions might reflect the developmental disturbance in intracortical organization and cortical connectivities in MR.

Subjects with intellectual disability and familial need for full-time special education show regional brain alterations: a voxel-based morphometry study

Subjects attending full-time special education (SE) often have multifactorial background for their cognitive impairment, and brain MRI may show nonspecific changes. As voxel-based morphometry reveals regional volume differences, we applied this method to 119 subjects with cognitive impairments and familial need for full-time SE--graded into three levels from specific disorders of cognitive processes (level 1) to intellectual disability (IQ <70; level 3)--and to 43 age-matched controls attending mainstream education (level 0). Subjects in SE groups had smaller global brain white matter (WM), cerebrospinal fluid, and total brain volume than controls. Compared with controls, subjects with intellectual disabilities in SE level 3 showed greater regional gray matter volumes bilaterally in the ventral and dorsal anterior cingulate cortex and smaller regional gray matter volumes in the left thalamus and cerebellar hemisphere. Further, they had greater WM volume in the left frontoparietal region and smaller WM volumes in the posterior limbs of the internal capsules. Subjects in SE level 1 and 2 groups showed the same tendency, but the results were nonsignificant. In conclusion, compared with controls, subjects with intellectual disabilities showed in voxel-based morphometry analysis several regional brain alterations.