Inge W.M. van Uden

Cigarette smoking is associated with reduced microstructural integrity of cerebral white matter

Cigarette smoking doubles the risk of dementia and Alzheimers disease. Various pathophysiological pathways have been proposed to cause such a cognitive decline, but the exact mechanisms remain unclear. Smoking may affect the microstructural integrity of cerebral white matter. Diffusion tensor imaging is known to be sensitive for microstructural changes in cerebral white matter. We therefore cross-sectionally studied the relation between smoking behaviour (never, former, current) and diffusion tensor imaging parameters in both normal-appearing white matter and white matter lesions as well as the relation between smoking behaviour and cognitive performance. A structured questionnaire was used to ascertain the amount and duration of smoking in 503 subjects with small-vessel disease, aged between 50 and 85 years. Cognitive function was assessed with a neuropsychological test battery. All subjects underwent 1.5 Tesla magnetic resonance imaging. Using diffusion tensor imaging, fractional anisotropy and mean diffusivity were calculated in both normal-appearing white matter and white matter lesions. A history of smoking was associated with significant higher values of mean diffusivity in normal-appearing white matter and white matter lesions (P-trend for smoking status = 0.02) and with poorer cognitive functioning compared with those who never smoked. Associations with smoking and loss of structural integrity appeared to be strongest in normal-appearing white matter. Furthermore, the duration of smoking cessation was positively related to lower values of mean diffusivity and higher values of fractional anisotropy in normal-appearing white matter [β = -0.004 (95% confidence interval -0.007 to 0.000; P = 0.03) and β = 0.019 (95% confidence interval 0.001-0.038; P = 0.04)]. Fractional anisotropy and mean diffusivity values in normal-appearing white matter of subjects who had quit smoking for >20 years were comparable with subjects who had never smoked. These data suggest that smoking affects the microstructural integrity of cerebral white matter and support previous data that smoking is associated with impaired cognition. Importantly, they suggest that quitting smoking may reverse the impaired structural integrity.

Gait in Elderly With Cerebral Small Vessel Disease

Background and Purpose— Gait disorders are common in the elderly and are related to loss of functional independence and death. White matter lesions (WMLs) may be related, but only a minority of individuals with WMLs has gait disorders. Probably other factors are involved, including location and the independent effect of frequently coinciding lacunar infarcts, the other aspect of cerebral small vessel disease. The aim of our study was to investigate the effect of both the severity and location of both WMLs and lacunar infarcts on gait. Methods— Four hundred thirty-one independently living, nondemented elderly aged between 50 and 85 years with cerebral small vessel disease were included in this analysis and underwent MRI scanning. The number and location of lacunar infarcts were rated and WML volume was assessed by manual segmentation with automated delineating of different regions. Gait was assessed quantitatively with an electronic walkway as well as the semiquantitatively Tinetti and Timed-Up-and-Go test. Results— WMLs and lacunar infarcts were both independently associated with most gait parameters with stride length as the most sensitive parameter related to WMLs. WMLs in the sublobar (basal ganglia/internal capsule) and limbic areas and lacunar infarcts in the frontal lobe and thalamus were related to a lower velocity. Conclusions— Cerebral small vessel disease is related to gait disturbances. Because small vessel disease may, in part, be preventable, it should be regarded as a potentially important target for postponing gait impairment.

Diffusion tensor imaging and cognition in cerebral small vessel disease: the RUN DMC study.

BACKGROUND Cerebral small vessel disease (SVD) is very common in elderly and related to cognition, although this relation is weak. This might be because the underlying pathology of white matter lesions (WML) is diverse and cannot be properly appreciated with conventional FLAIR MRI. In addition, conventional MRI is not sensitive to early loss of microstructural integrity of the normal appearing white matter (NAWM), which might be an important factor. Diffusion tensor imaging (DTI) provides alternative information on microstructural white matter integrity and we have used this to investigate the relation between white matter integrity, in both WML and NAWM, and cognition among elderly with cerebral SVD. METHODS The RUN DMC study is a prospective cohort study among 503 independently living, non-demented elderly with cerebral SVD aged between 50 and 85 years. All subjects underwent MRI and DTI scanning. WML were segmented manually. We measured mean diffusivity (MD) and fractional anisotropy (FA), as assessed by DTI in both WML and NAWM. RESULTS Inverse relations were found between MD in the WML and NAWM and global cognitive function (β=-.11, p<0.05; β=-.18, p<0.001), psychomotor speed (β=-.15, p<0.01; β=-.18, p<0.001), concept shifting (β=-.11, p<0.05; β=-.10, p<0.05) and attention (β=-.12, p<0.05; β=-.15, p<0.001). The relation between DTI parameters in both WML and NAWM and cognitive performance was most pronounced in subjects with severe WML. CONCLUSION DTI parameters in both WML and NAWM correlate with cognitive performance, independent of SVD. DTI may be a promising tool in exploring the mechanisms of cognitive decline and could function as a surrogate marker for disease progression in therapeutic trials. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Hypertension and cerebral diffusion tensor imaging in small vessel disease.

Background and Purpose— Hypertension is a risk factor for cerebral small vessel disease, which includes white matter lesions (WML) and lacunar infarcts. These lesions are frequently observed on MRI scans of elderly people and play a role in cognitive decline. Preferably, one would like to evaluate the effect of hypertension before fluid-attenuated inversion recovery visible macrostructural lesions occur, possibly by investigating its effect on the microstructural integrity of the white matter. Diffusion tensor imaging provides measures of structural integrity. Methods— In 503 patients with small vessel disease, aged between 50 and 85 years, we cross-sectionally studied the relation between blood pressure, hypertension, and hypertension treatment status and diffusion tensor imaging parameters in both normal-appearing white matter (NAWM) and WMLs. All of the subjects underwent 1.5-T MRI and diffusion tensor imaging scanning. Fractional anisotropy and mean diffusivity were calculated in both NAWM and WMLs. Results— Increased blood pressure and hypertension were significantly related to lower fractional anisotropy in both NAWM and WMLs and to higher mean diffusivity in WMLs. For hypertensives, odds ratios for the risk of impaired microstructural integrity (fractional anisotropy) were 3.1 (95% CI: 1.8 to 5.7) and 2.1 (95% CI: 1.2 to 3.5) in NAWM and WMLs, respectively, compared with normotensives. Fractional anisotropy odds ratios for treated uncontrolled subjects were 6.5 (95% CI: 3.3 to 12.7) and 2.7 (95% CI: 1.5 to 5.1) in NAWM and WMLs, respectively, compared with normotensives. Conclusions— Our data show that diffusion tensor imaging may be an appropriate tool to monitor the effect of blood pressure and the response to treatment on white matter integrity, probably even before the development of WMLs on fluid-attenuated inversion recovery.

Diffusion tensor imaging of the hippocampus and verbal memory performance: the RUN DMC study.

Background: Cerebral small vessel disease (SVD) and hippocampal atrophy are related to verbal memory failures and may ultimately result in Alzheimers disease. However, verbal memory failures are often present before structural changes on conventional MRI appear. Changes in microstructural integrity of the hippocampus, which cannot be detected with conventional MRI, may be the underlying pathological substrate. With diffusion tensor imaging (DTI), we investigated the relation between the microstructural integrity of the hippocampus and verbal memory performance in 503 nondemented elderly with SVD. Methods: The Radboud University Nijmegen Diffusion tensor and Magnetic resonance imaging Cohort study is a prospective cohort study among 503 nondemented elderly with cerebral SVD aged between 50 and 85 years. All participants underwent T1 MPRAGE, fluid‐attenuated inversion recovery, DTI scanning and the Rey Auditory Verbal Learning Test. After manual segmentation of the hippocampi, we calculated the mean diffusivity (MD) and fractional anisotropy in both hippocampi. The relation between memory performance and hippocampal DTI parameters was adjusted for age, sex, education, depressive symptoms, hippocampal, and white‐matter lesions volume and lacunar infarcts. Results: We found inverse relations between hippocampal MD and verbal memory performance (β = −0.22; P < 0.001), immediate recall (β = −0.22; P < 0.001), delayed recall (β = −0.20; P < 0.001), and forgetting rate (β = −0.13; P = 0.025), most pronounced in participants with a normal hippocampal volume. Conclusion: Microstructural integrity of the hippocampus assessed by DTI is related to verbal memory performance in elderly with SVD, also in participants with an intact appearing hippocampus. Changes in hippocampal microstructure may be an early marker of underlying neurodegenerative disease, before macrostructural (i.e., volumetric) changes occur. Hum Brain Mapp, 2012.

Diffusion Tensor Imaging and Gait in Elderly Persons With Cerebral Small Vessel Disease

Background and Purpose— Although cerebral small vessel disease, including white matter lesions (WML) and lacunar infarcts, is associated with gait disturbances, not all individuals with small vessel disease have these disturbances. Identical-appearing WML on MRI could reflect different degrees of microstructural integrity. Moreover, conventional MRI does not assess the integrity of normal-appearing white matter (NAWM). We therefore investigated the relation between white matter integrity assessed by diffusion tensor imaging in WML, NAWM, several regions of interest, and gait. Methods— A total of 484 nondemented elderly persons between 50 and 85 years old with cerebral small vessel disease were included in this analysis and underwent MRI and diffusion tensor imaging scanning. Mean diffusivity and fractional anisotropy within WML, NAWM, and regions of interest were related to quantitative and semiquantitative gait parameters. Results— Mean diffusivity in the WML was inversely related with gait (velocity &bgr;=−0.15; P=0.002). For the fractional anisotropy, this relation was less evident. The same was found in the NAWM (velocity &bgr;=−0.21; P<0.001) and for some parameters also after additional adjustment for WML and lacunar infarcts. Conclusion— This study indicates that integrity of both WML and NAWM, beyond the detection limit of conventional MRI, is associated with gait disturbances.

Location Sensitive Deep Convolutional Neural Networks for Segmentation of White Matter Hyperintensities

The anatomical location of imaging features is of crucial importance for accurate diagnosis in many medical tasks. Convolutional neural networks (CNN) have had huge successes in computer vision, but they lack the natural ability to incorporate the anatomical location in their decision making process, hindering success in some medical image analysis tasks. In this paper, to integrate the anatomical location information into the network, we propose several deep CNN architectures that consider multi-scale patches or take explicit location features while training. We apply and compare the proposed architectures for segmentation of white matter hyperintensities in brain MR images on a large dataset. As a result, we observe that the CNNs that incorporate location information substantially outperform a conventional segmentation method with handcrafted features as well as CNNs that do not integrate location information. On a test set of 50 scans, the best configuration of our networks obtained a Dice score of 0.792, compared to 0.805 for an independent human observer. Performance levels of the machine and the independent human observer were not statistically significantly different (p-value = 0.06).

Cerebral microbleeds are related to subjective cognitive failures: the RUN DMC study

Cerebral small vessel disease (SVD), including white matter lesions (WML) and lacunar infarcts, is related to objective cognitive impairment but also to subjective cognitive failures (SCF). SCF have reported to be an early predictor of dementia. Cerebral microbleeds (MB) are another manifestation of SVD and have been related to cognitive impairment, but the role of MB in SCF has never been studied. We therefore investigated whether MB are related to SCF among non-demented elderly individuals with SVD, independent of coexisting WML and lacunar infarcts. The RUN DMC study is a prospective cohort study among 503 older persons with cerebral SVD between 50 and 85 years of age. All participants underwent FLAIR and T2* scanning. SCF, subjective memory failures (SMF), and subjective executive failures (SEF) were assessed. The relation between SCF and the presence, number and location of MB was assessed by linear regression analyses adjusted for age, sex, education, depressive symptoms, cognitive function, total brain volume, normalized hippocampal volume, territorial infarcts, WML, and lacunar infarcts. MB were present in 11%. We found a relation between the presence, total number and lobar located MB, and SCF, SMF, and SEF and the reported progression of these failures, especially in participants with good objective cognitive function. In conclusion, MB are related to SCF independent of co-existing WML and lacunar infarcts, especially in those with good objective cognitive performance. These results suggest that MB are associated with the earliest manifestations of cognitive impairment. MB may help us to understand the role of the ever-expanding spectrum of SVD in cognitive impairment.

Cerebral white matter lesions and lacunar infarcts contribute to the presence of mild parkinsonian signs

Background and Purpose— Mild parkinsonian signs (MPS) are common in elderly people and may be an early stage of parkinson(ism). They might be related to cerebral small-vessel disease, although this association remains incompletely understood. To identify subjects at early stages of the disease, we investigated whether the presence of MPS was dependent on the severity and location of small-vessel disease, including white matter lesions and lacunar infarcts. Methods— Four hundred thirty individuals, with small-vessel disease, aged between 50 and 85 years, without dementia or parkinsonism, were included in this analysis and underwent MRI scanning. The number and location of lacunar infarcts were rated. White matter lesion volume was assessed by manual segmentation with automated delineating of different regions. Presence of MPS was based on the motor section of the Unified Parkinsons Disease Rating Scale. Associations were determined using logistic regression analysis adjusted for age, sex, and total brain volume. Results— Severe white matter lesions and the presence of lacunar infarcts were independently associated with the presence of MPS (OR, 2.6; 95% CI, 1.3–4.9 and OR, 1.8; 95% CI, 1.0–3.0). Frontal and parietal white matter lesions and, to a lesser extent, lacunar infarcts in the thalamus were associated with a higher risk of MPS. The presence of lacunar infarcts was independently related to the bradykinesia category of parkinsonian signs. Conclusions— This study shows that severe small-vessel disease, especially at certain locations, is associated with MPS signs in older adults. Our findings suggest that small-vessel disease interrupts basal ganglia–thalamocortical circuits involving both the frontal and parietal lobes and hence may result in MPS.

Cerebral small vessel disease and incident parkinsonism: The RUN DMC study

Objective: To investigate the relation between baseline cerebral small vessel disease (SVD) and the risk of incident parkinsonism using different MRI and diffusion tensor imaging (DTI) measures. Methods: In the Radboud University Nijmegen Diffusion Tensor and Magnetic Resonance Cohort (RUN DMC) study, a prospective cohort study, 503 elderly participants with SVD and without parkinsonism were included in 2006. During follow-up (2011–2012), parkinsonism was diagnosed according to UK Brain Bank criteria. Cox regression analysis was used to investigate the association between baseline imaging measures and incident all-cause parkinsonism and vascular parkinsonism (VP). Tract-based spatial statistics analysis was used to identify differences in baseline DTI measures of white matter (WM) tracts between participants with VP and without parkinsonism. Results: Follow-up was available from 501 participants (mean age 65.6 years; mean follow-up duration 5.2 years). Parkinsonism developed in 20 participants; 15 were diagnosed with VP. The 5-year risk of (any) parkinsonism was increased for those with a high white matter hyperintensity (WMH) volume (hazard ratio [HR] 1.8 per SD increase, 95% confidence interval [CI] 1.3–2.4) and a high number of lacunes (HR 1.4 per number increase, 95% CI 1.1–1.8) at baseline. For VP, this risk was also increased by the presence of microbleeds (HR 5.7, 95% CI 1.9–16.8) and a low gray matter volume (HR 0.4 per SD increase, 95% CI 0.2–0.8). Lower fractional anisotropy values in bifrontal WM tracts involved in movement control were observed in participants with VP compared to participants without parkinsonism. Conclusions: SVD at baseline, especially a high WMH volume and a high number of lacunes, is associated with incident parkinsonism. Our findings favor a role of SVD in the etiology of parkinsonism.