Quantitative MR and cognitive impairment in cryptogenic localisation-related epilepsy.

For patients with chronic cryptogenic localisation-related epilepsy (CLRE), conventional MRI does not provide measures to discern between patients with or without cognitive complaints. We investigated, in a preliminary study, whether it is possible to detect cerebral biomarkers of cognitive impairment in patients with CLRE using sensitive quantitative MRI techniques. Neuropsychological assessment and quantitative 3.0 T MRI, comprising T2 relaxometry, diffusion tensor imaging, and spectroscopic imaging, were applied to 35 patients with CLRE and 21 healthy controls. Analysis included the left and right hippocampi, and frontal and temporal lobes. Differences between the groups and correlations with cognitive and clinical characteristics were assessed. Patients with epilepsy scored significantly worse on cognitive tasks compared to healthy controls. Significantly larger CSF fractions in the hippocampi and left temporal lobe, a longer T2 relaxation time in the left hippocampus, and a significantly higher concentration of glutamate/glutamine in the left frontal lobe were observed in patients with epilepsy. Moreover, poor memory performance was significantly correlated with larger CSF fractions in the right hippocampus and left temporal lobe in patients. In the temporal lobe, an association between subtle changes in morphology (indicative of atrophy) and memory performance was found, consistent with previous literature. These results may help to explain the alterations in brain functioning in patients with epilepsy.

Affected functional networks associated with sentence production in classic galactosemia.

Patients with the inherited metabolic disorder classic galactosemia have language production impairments in several planning stages. Here, we assessed potential deviations in recruitment and connectivity across brain areas responsible for language production that may explain these deficits. We used functional magnetic resonance imaging (fMRI) to study neural activity and connectivity while participants carried out a language production task. This study included 13 adolescent patients and 13 age- and gender-matched healthy controls. Participants passively watched or actively described an animated visual scene using two conditions, varying in syntactic complexity (single words versus a sentence). Results showed that patients recruited additional and more extensive brain regions during sentence production. Both groups showed modulations with syntactic complexity in left inferior frontal gyrus (IFG), a region associated with syntactic planning, and in right insula. In addition, patients showed a modulation with syntax in left superior temporal gyrus (STG), whereas the controls did not. Further, patients showed increased activity in right STG and right supplementary motor area (SMA). The functional connectivity data showed similar patterns, with more extensive connectivity with frontal and motor regions, and restricted and weaker connectivity with superior temporal regions. Patients also showed higher baseline cerebral blood flow (CBF) in right IFG and trends towards higher CBF in bilateral STG, SMA and the insula. Taken together, the data demonstrate that language abnormalities in classic galactosemia are associated with specific changes within the language network. These changes point towards impairments related to both syntactic planning and speech motor planning in these patients.

Working memory deficits in high-functioning adolescents with autism spectrum disorders: neuropsychological and neuroimaging correlates.

Working memory is a temporary storage system under attentional control. It is believed to play a central role in online processing of complex cognitive information and may also play a role in social cognition and interpersonal interactions. Adolescents with a disorder on the autism spectrum display problems in precisely these domains. Social impairments, communication difficulties, and repetitive interests and activities are core domains of autism spectrum disorders (ASD), and executive function problems are often seen throughout the spectrum. As the main cognitive theories of ASD, including the theory of mind deficit hypotheses, weak central coherence account, and the executive dysfunction theory, still fail to explain the broad spectrum of symptoms, a new perspective on the etiology of ASD is needed. Deficits in working memory are central to many theories of psychopathology, and are generally linked to frontal-lobe dysfunction. This article will review neuropsychological and (functional) brain imaging studies on working memory in adolescents with ASD. Although still disputed, it is concluded that within the working memory system specific problems of spatial working memory are often seen in adolescents with ASD. These problems increase when information is more complex and greater demands on working memory are made. Neuroimaging studies indicate a more global working memory processing or connectivity deficiency, rather than a focused deficit in the prefrontal cortex. More research is needed to relate these working memory difficulties and neuroimaging results in ASD to the behavioral difficulties as seen in individuals with a disorder on the autism spectrum.

Functional MRI in chronic epilepsy: associations with cognitive impairment.

Chronic epilepsy is frequently accompanied by serious cognitive side-effects. Clinical factors are important, but cannot account entirely for this cognitive comorbidity. Therefore, research is focusing on the underlying cerebral mechanisms to understand the development of cognitive dysfunction. In the past two decades, functional MRI techniques have been applied extensively to the study of cognitive impairment in chronic epilepsy. However, because of wide variation in study designs, analysis methods, and data presentation, interpretation of these studies has become increasingly difficult for clinicians. In patients with localisation-related epilepsy, whether findings of functional MRI represent the underlying neuronal substrate for cognitive decline remains a subject of debate.