Adult-onset genetic leukoencephalopathies: a MRI pattern-based approach in a comprehensive study of 154 patients.

Inherited white matter diseases are rare and heterogeneous disorders usually encountered in infancy. Adult-onset forms are increasingly recognized. Our objectives were to determine relative frequencies of genetic leukoencephalopathies in a cohort of adult-onset patients and to evaluate the effectiveness of a systematic diagnostic approach. Inclusion criteria of this retrospective study were: (i) symmetrical involvement of white matter on the first available brain MRI; (ii) age of onset above 16 years. Patients with acquired diseases were excluded. Magnetic resonance imaging analysis identified three groups (vascular, cavitary and non-vascular/non-cavitary) in which distinct genetic and/or biochemical testing were realized. One hundred and fifty-four patients (male/female = 60/94) with adult-onset leukoencephalopathies were identified. Mean age of onset was 38.6 years. In the vascular group, 41/55 patients (75%) finally had a diagnosis [including CADASIL (cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy, n = 32) and COL4A1 mutation, n = 7]. In the cavitary group, 13/17 (76%) patients had a diagnosis of EIF2B-related disorder. In the third group (n = 82), a systematic biological screening allowed a diagnosis in 23 patients (28%) and oriented direct genetic screening identified 21 additional diseases (25.6%). Adult-onset genetic leukoencephalopathies are a rare but probably underestimated entity. Our study confirms the use of a magnetic resonance imaging-based classification with a final diagnosis rate of 64% (98/154) cases.

Neuropsychological and 18FDG-PET studies in a family with idiopathic basal ganglia calcifications.

Idiopathic basal ganglia calcification (FIBGC) is a rare autosomal dominant neurodegenerative disease, the main clinical signs of which are parkinsonism, cognitive deterioration and/or psychiatric troubles. Familial forms are rare. The underlying basis is not known. We performed detailed neurological, neuropsychological, brain CT scans and MRI evaluations in 15 patients of a large FIBGC family. Three patients also underwent a (18)FDG-PET scan study not previously performed in patients with FIBGC. Basal ganglia calcifications were present in 8 individuals, 3 of which had schizophrenia-like psychosis, cognitive and/or extrapyramidal signs. The mean age at disease onset was 34.0+/-3.6 years. Two patients had moderate executive dysfunction, whereas the proband had more severe dementia. (18)FDG uptake was significantly reduced in striatal or cortical areas, including the precuneus, posterior cingulate and superior temporal gyri. This study shows that calcifications and striatal neuronal degeneration can occur independently, and that functional changes in cortical areas can be observed early in FIBGC. Hypometabolism in the precuneus and posterior cingulate gyrus, which are involved in episodic memory processing, could be responsible for the episodic memory deficit found in the patients. Whether the underlying mechanism involves a neuronal loss or a functional alteration remains to be elucidated.

Functional imaging of working memory in Parkinson's disease: compensations and deficits.

BACKGROUND AND PURPOSE: Over and above typical motor alterations, executive and working memory (WM) impairment can also occur in early idiopathic Parkinson's disease (PD). We aimed to investigate the compensatory neural processes involved in WM performance, as well as the networks involved in the long-term memory transfer from short-term stores in PD. METHODS: Relative cerebral blood flow (rCBF) was mapped with H2O(15)-PET in eight treated nondemented PD patients while performing a WM verbal double-task (Brown-Peterson paradigm) using both short (6-second) and long (18-second) delays. RESULTS: As compared to nine age-matched healthy subjects, performance of the PD group was only slightly reduced on the short-delay but markedly impaired on the long-delay task. Underlying the relatively preserved short-delay performance, the PD group exhibited overactivation of prefrontal and parietal areas involved in attention-demanding processes, suggestive of efficient compensatory processes. Further supporting this, significant positive correlations were found between short-delay performance and rCBF in the bilateral inferior parietal cortex. In contrast, the lack of overactivation with the long-delay task together with posterior cingulate hypoactivation would support the idea of functional disconnection impairing transfer of information from prefrontal onto (para)limbic areas. These findings suggest novel areas of investigation into early cognitive impairments in PD.

Reduced thalamic and cerebellar rest metabolism in relapsing-remitting multiple sclerosis, a positron emission tomography study: correlations to lesion load.

Magnetic resonance imaging (MRI) is the main tool for detecting central nervous system lesions in MS. However, classical anatomical MRI is unable to assess exactly disease related injury in normal-appearing brain tissue and to give information about the functional consequences of the disease, explaining weak correlation frequently observed between lesion load and clinical data. Recently, functional brain imaging techniques have provided new insights concerning pathophysiological processes of the disease. Among them Positron Emission Tomography (PET), a sensitive technique to evaluate functional consequences of tissue injury in other neurological diseases, has rarely been used in MS. Seventeen Relapsing-Remitting (RR-) MS patients with low disability at the early stage of the disease underwent measurements of cerebral metabolic rate of glucose (rCMRglu) in resting state by PET using [(18)F] fluorodeoxyglucose (FDG) and assessment of regional cortical and white matter lesion volume (LV), using an in-house-developed semi-automatic method, was done at the same time on MRI. rCMRglu of MS patients was compared with rCMRglu of 18 normal control subjects using univariate SPM99 analysis through Matlab 5 and correlations between rCMRglu and LV were tested using multivariate linear regression using SPM99. Statistical threshold was set at p<0.05 corrected for multiple comparisons and correlations. Compared to controls, reduced rCMRglu was found in the right thalamus (p<0.001), in bilateral cerebellum (p<0.05 for right and p<0.01 for left) and the posterior part of left inferior parietal cortex (p<0.05). In addition, higher rCMRglu in patients compared to controls was observed in left inferior frontal cortex, left (anterior part) and right inferior parietal cortex (p<0.001). rCMRglu in right thalamus correlates negatively with different LV: total LV, total juxtacortical and/or overlapping cortico-subcortical LV, total and frontal deep white matter LV. rCMRglu of the right superior frontal cortex negatively correlated with total and parieto-occipital deep white matter LV. The results of this study, performed in a group of recent RR-MS patients with low disability, suggest that demyelinating lesions in MS mainly have a remote effect on cortical, basal ganglia and cerebellum metabolism and that regional cortical compensatory mechanisms may be observed concurrently.

Fatigue is associated with metabolic and density alterations of cortical and deep gray matter in Relapsing-Remitting-Multiple Sclerosis patients at the earlier stage of the disease: A PET/MR study.

BACKGROUND: Fatigue is a common but complex symptom of multiple sclerosis. A central origin is now suggested as a key feature of its pathophysiology and gray matter (GM) structure seems to be (particularly) involved in the neurobiological basis of fatigue in multiple sclerosis (MS) patients. METHODS: We investigated, in a cohort of 17 Relapsing-Remitting-MS patients recruited within three years of disease diagnosis, the link between fatigue severity evaluated by the EMIF-SEP (a validated self-report questionnaire in French), and metabolic and density alterations of GM using positron emission tomography (PET) and magnetic resonance (MR) imaging using SPM5 (statistical parametric morphometry) analysis and voxel-based-morphometry. RESULTS: Compared to patients without fatigue-MS (NF-MS) group, patients with fatigue-MS (F-MS) had significant reduction (with correctedp<0.05) of GM density in clusters located in the bilateral middle, superior and inferior frontal cortex and in left temporal and parietal cortex. In addition, the total score for fatigue was negatively correlated with GM density in the same regional areas for the whole group. Total fatigue score was negatively correlated with GM density in bilateral thalamus (correctedp=0.04) and with rest cerebral metabolic rate of glucose (rCMRglu) in the basal ganglia (correctedp<0.05). Juxtacortical and/or overlapping corticosubcortical lesion volume in frontal and temporal areas were significantly higher in the F-MS group compared to NF-MS patients. CONCLUSIONS: These results add new data suggesting that fatigue is associated with functional and structural changes of cerebral gray matter especially in frontal cortex and basal ganglia.

Working memory and dopamine: clinical and experimental clues.

Working memory has been successively considered as a mnesic or executive process. The cognitive processes involved in working memory and the executive functions are closely linked. Most authors currently agree that executive functions include planning, attentional maintenance, mental flexibility and attentional inhibition. Considering that the role of the central administrator, the main module of the working memory model, is to manage new situations, inhibit old non-pertinent schemes, or carry out attentional control, it is clear that it involves the different executive processes mentioned above. Therefore, even though the working memory model has its origins in the classic concept of short-term memory, it is now situated at the interface between memory and executive functions. The identification of the neuroanatomical support of these processes has been widely explored for many years. The involvement of monoaminergic neurotransmitter systems, and in particular of the dopaminergic system, in these complex cognitive functions has been suggested by numerous studies, both in humans and in non-human primates.