Measuring impulsivity in Parkinson's disease: a correlational and structural neuroimaging study using different tests.

BACKGROUND AND PURPOSE: Impulsivity is an aspect of personality and a major component of multiple neuropsychiatric conditions. In Parkinson's disease, it has been associated with the expression of impulse control disorders, a highly prevalent non-motor complication. Even though multiple tests of impulsivity have been used in this context, the impact of test choice has not been addressed. The aim was to evaluate whether different impulsivity measures in Parkinson's disease share substantial inter-scale and anatomical correlations or rather mirror different underlying phenomena. METHODS: In a consecutive sample of 89 Parkinson's disease patients without impulse control disorders, four common tests were evaluated assessing different aspects of impulsivity: impulsiveness trait, decisions under implicit risk with and without losses, and delay discounting. Correlations among test scores were analysed and each score was used as a regressor in a set of grey matter volume (GMV) voxel-based morphometry analyses to explore their brain structural correlates. RESULTS: No significant correlations were found between the different impulsivity tests. Furthermore, their structural brain correlates were divergent. Impulsiveness trait appeared to be associated with lower GMV in dorsal-lateral prefrontal cortices, implicit risk (with losses) with higher GMV in the left nucleus accumbens and lower left insular GMV, implicit risk (without losses) with higher GMV in the left lingual gyrus and lower GMV in the gyri recti and delay discounting with higher GMV in the left nucleus accumbens. CONCLUSIONS: In Parkinson's disease, different impulsivity measures reflect very dissimilar behavioural and brain structural correlates. Our results suggest that parkinsonian impulsivity is not a unitary phenomenon but rather a heterogeneous entity.

Visual hallucinations in patients with acute stroke: a prospective exploratory study.

BACKGROUND AND PURPOSE: The incidence, underlying physiopathology, features and association with lesion topography of visual hallucinations in acute stroke have scarcely been investigated. METHODS: Patients with a diagnosis of acute stroke (ischaemic or haemorrhagic) in any vascular territory, admitted within 24 h after the onset of symptoms, were consecutively included in the study. Patients with a previous history of psychosis or cognitive impairment were excluded. They and/or their caregivers answered a structured hallucination and sleep questionnaire at admission, within the first 15 days and at the clinical follow-up 3-6 months after discharge. Lesion location (IMAIOS online atlas) and leukoaraiosis (Wahlund scale) were determined by magnetic resonance imaging or computed tomography scan. Subsets of patients also underwent a neuropsychological evaluation (N = 50) and an electroencephalogram (N = 33) before discharge. RESULTS: In all, 77 patients with a mean age of 71 ± 12 years were included of whom 57.1% were men. The incidence of visual hallucinations was 16.7%. These hallucinations were mostly complex, in black and white and self-limited. The appearance of hallucinations was not influenced by age, sex, neuropsychological performance during admission or modified Rankin scale score at discharge. Visual hallucinations were associated with occipital cortex lesions (P = 0.04), and with sleep disturbances during and before admission (P = 0.041 and P = 0.03 respectively). CONCLUSIONS: Visual hallucinations are relatively frequent in patients with acute stroke and they are self-limited. Patients with occipital lesions and sleep disturbances are more likely to suffer them.

Widespread Increased Diffusivity Reveals Early Cortical Degeneration in Huntington Disease.

BACKGROUND AND PURPOSE: Huntington disease is a devastating genetic neurodegenerative disorder for which no effective treatment is yet available. Although progressive striatal atrophy is its pathologic hallmark, concomitant cortical deterioration is assumed to occur, but it is poorly characterized. Our objective was to study the loss of cortical integrity and its association with clinical indicators throughout the course of the disease. MATERIALS AND METHODS: Using a cohort of 39 patients with Huntington disease and 25 controls with available MR imaging (T1WI and DTI), we compared cortical atrophy and intracortical diffusivity across disease stages. Intracortical diffusivity is a DTI-derived metric that has recently been suggested to detect incipient neuronal death because water can diffuse more freely in cortical regions with reduced neural density. RESULTS: We observed progressive thinning and increasing diffusivity within the cerebral cortex of patients with Huntington disease (P < .05, corrected for multiple comparisons). Most important, in the absence of pronounced atrophy, widespread increased diffusivity was already present in individuals with premanifest Huntington disease, correlating, in turn, with clinical and disease-specific progression markers. CONCLUSIONS: Intracortical diffusivity may be more sensitive than cortical thinning for tracking early neurodegeneration in Huntington disease. Moreover, our findings provide further evidence of an early cortical compromise in Huntington disease, which contributes to our understanding of its clinical phenotype and could have important therapeutic implications.