Brain magnetic resonance imaging of siblings from families with two or more children with learning or intellectual disabilities and need for full-time special education

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.

Aberrant Structural and Functional Developmental Trajectories in Children With Intellectual Disability

Intellectual disability (ID) is associated with aberrant structural and functional development of the brain, yet how the dynamical developmental changes of the structure and function of ID from childhood to around puberty remains unknown. To explore the abnormal developmental trajectories of structure and function, 40 children with ID aged 6-13 years and 30 sex-, age-, and educational level-matched healthy controls (HC) with age range from 6 to 13 were recruited. The automatic voxel-based morphometry (VBM) and resting-state functional connectivity (FC) analyses were adopted to delineate the structural and functional differences. Significantly decreased total gray matter volume (GMV) and white matter volume (WMV) in children with ID were found, and the developmental trajectories of GMV and WMV in children with ID showed an opposite direction as compared with HC. The voxel-wise VMB analysis further revealed significantly increased GMV in the dorsal medial prefrontal cortex (dmPFC), bilateral orbital part of the inferior frontal gyrus (orb_IFG.L, orb_IFG.R), right cuneus (cuneus.R), and bilateral middle frontal gyrus (MFG.L, MFG.R) in children with ID. The following seed-based whole-brain functional connectivity analyses of the brain areas with changed GMV found decreased FCs between the cuneus.R and left intraparietal sulcus (IPS.L) and between the MFG.R and anterior cingulate cortex (ACC) in children with ID. Moreover, negative correlations between GMV values in the dmPFC, orb_IFG.L, cuneus.R, and intelligence quotient (IQ) scores and positive correlations between the FCs of the cuneus.R with IPS.L and MFG.R with ACC and IQ scores were found in children with ID and HC. Our findings provide evidence for the abnormal structural and functional development in children with ID and highlight the important role of frontoparietal network in the typical development. The abnormal development of GMV and functional couplings found in this study may be the neuropathological bases of children with ID.

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.

The Broad Autism (Endo)Phenotype: Neurostructural and Neurofunctional Correlates in Parents of Individuals with Autism Spectrum Disorders

Autism Spectrum Disorders (ASD) are a set of neurodevelopmental disorders with an early-onset and a strong genetic component in their pathogenesis. According to genetic and epidemiological data, ASD relatives present personality traits similar to, but not as severe as the defining features of ASD, which have been indicated as the "Broader Autism Phenotype" (BAP). BAP features seem to be more prevalent in first-degree relatives of individuals with ASD than in the general population. Characterizing brain profiles of relatives of autistic probands may help to understand ASD endophenotype. The aim of this review was to provide an up-to-date overview of research findings on the neurostructural and neurofunctional substrates in parents of individuals with ASD (pASD). The primary hypothesis was that, like for the behavioral profile, the pASD express an intermediate neurobiological pattern between ASD individuals and healthy controls. The 13 reviewed studies evaluated structural magnetic resonance imaging (MRI) brain volumes, chemical signals using magnetic resonance spectroscopy (MRS), task-related functional activation by functional magnetic resonance imaging (fMRI), electroencephalography (EEG), or magnetoencephalography (MEG) in pASD.The studies showed that pASD are generally different from healthy controls at a structural and functional level despite often not behaviorally impaired. More atypicalities in neural patterns of pASD seem to be associated with higher scores at BAP assessment. Some of the observed atypicalities are the same of the ASD probands. In addition, the pattern of neural correlates in pASD resembles that of adult individuals with ASD, or it is specific, possibly due to a compensatory mechanism. Future studies should ideally include a group of pASD and HC with their ASD and non-ASD probands respectively. They should subgrouping the pASD according to the BAP scores, considering gender as a possible confounding factor, and correlating these scores to underlying brain structure and function. These types of studies may help to understand the genetic mechanisms involved in the various clinical dimension of ASD.

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.