Diana Truran

Measurement of hippocampal subfields and age-related changes with high resolution MRI at 4T.

Histological studies suggest that hippocampal subfields are differently affected by aging and Alzheimer’s disease (AD). The aims of this study were: (1) To test if hippocampal subfields can be identified and marked using anatomical landmarks on high resolution MR images obtained on a 4T magnet. (2) To test if age-specific volume changes of subfields can be detected. Forty-two healthy controls (21–85 years) and three AD subjects (76–86 years) were studied with a high resolution T2 weighted fast spin echo sequence. The entorhinal cortex (ERC), subiculum, CA1, CA2 and CA3/4 and dentate were marked. A significant correlation between age and CA1 (r = −0.51, p = 0.0002) which was most pronounced in the seventh decade of life was found in healthy controls. In AD subjects, CA1 and subiculum were smaller than in age-matched controls. These preliminary findings suggest that measurement of hippocampal subfields may be helpful to distinguish between normal aging and AD.

Magnetic Resonance Imaging of Hippocampal Subfields in Posttraumatic Stress Disorder

CONTEXT Most neuroimaging studies of posttraumatic stress disorder (PTSD) have focused on potential abnormalities in the whole hippocampus, but the subfields of this structure, which have distinctive histological characteristics and specialized functions, have not been investigated. Studies of individual subfields may clarify the role of the hippocampus in PTSD. OBJECTIVE To determine if PTSD is associated with structural alterations in specific subfields of the hippocampus. DESIGN Case-control study. PARTICIPANTS A total of 17 male veterans with combat trauma and PTSD (mean [SD] age, 41 [12] years) and 19 age-matched male veterans without PTSD who were recruited from the outpatient mental health clinic of the San Francisco Veterans Affairs Medical Center and by advertising in the community. INTERVENTIONS High-resolution magnetic resonance imaging at 4 T. MAIN OUTCOME MEASURE Volumes of hippocampal subfields. RESULTS Posttraumatic stress disorder was associated with 11.4% (1.5%) (P = .02) smaller mean (SD) cornu ammonis 3 (CA3)/dentate gyrus subfield volumes, irrespective of age-related alterations, whereas other subfields were spared. Age was associated with reduced volume of the CA1 subfield (P = .03). Total hippocampal volume was also reduced in PTSD by a mean (SD) of 6.5% (0.6%) but, related to both PTSD (P = .05) and age (P = .01), was consistent with the measurements in the subfields. CONCLUSIONS The findings indicate for the first time in humans that PTSD is associated with selective volume loss of the CA3/dentate gyrus subfields, consistent with animal studies, implying that chronic stress suppresses neurogenesis and dendritic branching in these structures.

Neuropsychological dysfunction and neuroimaging abnormalities in neurologically intact adults with sickle cell anemia

CONTEXT Sickle cell anemia (SCA) is a chronic illness causing progressive deterioration in quality of life. Brain dysfunction may be the most important and least studied problem affecting individuals with this disease. OBJECTIVE To measure neurocognitive dysfunction in neurologically asymptomatic adults with SCA vs healthy control individuals. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study comparing neuropsychological function and neuroimaging findings in neurologically asymptomatic adults with SCA and controls from 12 SCA centers, conducted between December 2004 and May 2008. Participants were patients with SCA (hemoglobin [Hb] SS and hemoglobin level < or = 10 mg/dL) aged 19 to 55 years and of African descent (n = 149) or community controls (Hb AA and normal hemoglobin level) (n = 47). Participants were stratified on age, sex, and education. MAIN OUTCOME MEASURES The primary outcome measure was nonverbal function assessed by the Wechsler Adult Intelligence Scale, third edition (WAIS-III) Performance IQ Index. Secondary exploratory outcomes included performance on neurocognitive tests of executive function, memory, attention, and language and magnetic resonance imaging measurement of total intracranial and hippocampal volume, cortical gray and white matter, and lacunae. RESULTS The mean WAIS-III Performance IQ score of patients with SCA was significantly lower than that of controls (adjusted mean, 86.69 for patients with SCA vs 95.19 for controls [mean difference, -5.50; 95% confidence interval {CI}, -9.55 to -1.44]; P = .008), with 33% performing more than 1 SD (<85) below the population mean. Among secondary measures, differences were observed in adjusted mean values for global cognitive function (full-scale IQ) (90.47 for patients with SCA vs 95.66 for controls [mean difference, -5.19; 95% CI, -9.24 to -1.13]; P = .01), working memory (90.75 vs 95.25 [mean difference, -4.50; 95% CI, -8.55 to -0.45]; P = .03), processing speed (86.50 vs 97.95 [mean difference, -11.46; 95% CI, -15.51 to -7.40]; P < .001), and measures of executive function. Anemia was associated with poorer neurocognitive function in older patients. No differences in total gray matter or hippocampal volume were observed. Lacunae were more frequent in patients with SCA but not independently related to neurocognitive function. CONCLUSION Compared with healthy controls, adults with SCA had poorer cognitive performance, which was associated with anemia and age.

Effects of heavy drinking, binge drinking, and family history of alcoholism on regional brain metabolites.

BACKGROUND The main goals are to investigate the effects of chronic active heavy drinking on N-acetylaspartate (NAA) and other metabolites throughout the brain and to determine whether they are affected by family history (FH) of alcoholism and long-term drinking pattern. METHODS Forty-six chronic heavy drinkers (HD) and 52 light drinkers (LD) were recruited from the community and compared on measures of regional brain structure using magnetic resonance imaging and measures of common brain metabolites in gray matter (GM) and white matter (WM) of the major lobes, subcortical nuclei, brainstem, and cerebellum using short-echo time magnetic resonance spectroscopic imaging. Regional atrophy-corrected levels of NAA, myoinositol (mI), creatine, and choline-containing metabolites were compared as a function of group, FH of alcoholism, and bingeing. RESULTS Frontal WM NAA was lower in FH-negative HD than FH-positive HD and tended to be lower in women than men. Creatine-containing metabolites in parietal GM were higher in HD than LD. FH-negative compared with FH-positive HD also had more mI in the brainstem and tended to have lower NAA and more mI in frontal GM. Although parietal GM NAA was not significantly lower in HD than LD, it was lower in non-binge drinkers than bingers. Frontal WM NAA was lower in HD than LD, with the difference driven by a small number of women, FH-negative HD, and older age. Lower frontal WM NAA in HD was associated with lower executive and working memory functions and with lower P3b amplitudes at frontal electrodes. CONCLUSIONS Community-dwelling HD who are not in alcoholism treatment have brain metabolite changes that are associated with lower brain function and are likely of behavioral significance. Age, FH, and binge drinking modulate brain metabolite abnormalities. Metabolite changes in active HD are less pronounced and present with a different spatial and metabolite pattern than reported in abstinent alcoholics.

Evidence for ongoing brain injury in human immunodeficiency virus-positive patients treated with antiretroviral therapy.

Treatment with antiretroviral therapy (ART) has greatly reduced the incidence of dementia. The goal of this longitudinal study was to determine if there are ongoing macrostructural brain changes in human immunodeficiency virus—positive (HIV+) individuals treated with ART. To quantify brain structure, three-dimensional T1-weighted magnetic resonance imaging (MRI) scans were performed at baseline and again after 24 months in 39 HIV+ patients on ART and 30 HIV− controls. Longitudinal changes in brain volume were measured using tissue segmentation within regions of interest and deformation morphometry. Measured by tissue segmentation, HIV+ patients on ART had significantly (all P <.05) greater rates of white matter volume loss than HIV− control individuals. Compared with controls, the subgroup of HIV+ individuals on ART with viral suppression also had significantly greater rates of white matter volume loss. Deformation morphometry confirmed these results with more specific spatial localization. Deformation morphometry also detected greater rates of gray matter and white matter loss in the subgroup of HIV+ individuals with detectable viral loads. These results provide evidence of ongoing brain volume loss in HIV+ individuals on stable ART, possibly suggesting ongoing cerebral injury. The presence of continuing injury raises the possibility that HIV+ individuals—even in the presence of viral suppression in the periphery—are at greater risk for future cognitive impairments and dementia and possibly faster cognitive decline. Therefore, HIV+ individuals on ART should be monitored for cognitive decline, and treatments that reduce ongoing neurological injury should be considered.

Chronic divalproex sodium use and brain atrophy in Alzheimer disease

Objective: We evaluated the effect of the divalproex sodium formulation of valproic acid on brain volumes using MRI in people with mild to moderate Alzheimer disease (AD) and assessed for changes associated with behavioral and cognitive effects. Methods: Eighty-nine of 313 participants randomized to divalproex or placebo in a 24-month, parallel-group trial received MRI scans at baseline and 12 months. Interval MRI annual percent changes in whole brain, ventricular, and hippocampal volumes were the primary outcomes of interest. Change from baseline in clinical outcomes was assessed at 6-month intervals. Results: There were no baseline differences between active treatment and placebo groups in age, education, brain volumes, clinical rating scores, or APOE ϵ4 carrier status. The group treated with divalproex showed a greater rate of decline in left and right hippocampal and brain volumes (−10.9% and −12.4% vs −5.6% and −6.3%, and −3.5% vs −1.4%, respectively), and a greater rate of ventricular expansion (24.5% vs 9.9%) (p < 0.001). Mini-Mental State Examination scores showed a more rapid decline with divalproex through month 12 (placebo = −2.0 ± 4.3, divalproex = −3.9 ± 4.0) (p = 0.037), although there were no changes on other cognitive, behavioral, or functional ratings at 12 and 24 months. Conclusions: Divalproex treatment was associated with accelerated brain volume loss over 1 year and perhaps with greater cognitive impairment. The long-term clinical effects of these changes are not known.

Insomnia severity is associated with a decreased volume of the CA3/dentate gyrus hippocampal subfield.

BACKGROUND Prolonged disruption of sleep in animal studies is associated with decreased neurogenesis in the dentate gyrus. Our objective was to determine whether insomnia severity in a sample of posttraumatic stress disorder (PTSD) patients and control subjects was associated with decreased volume in the CA3/dentate hippocampal subfield. METHODS Volumes of hippocampal subfields in 17 veteran men positive for PTSD (41 +/- 12 years) and 19 age-matched male veterans negative for PTSD were measured with 4-T magnetic resonance imaging. Subjective sleep quality was measured by the Insomnia Severity Index (ISI) and the Pittsburgh Sleep Quality Index. RESULTS Higher scores on the ISI, indicating worse insomnia, were associated with smaller volumes of the CA3/dentate subfields (r = -.48, p < .01) in the combined sample. Adding the ISI score as a predictor for CA3/dentate volume to a hierarchical linear regression model after first controlling for age and PTSD symptoms accounted for a 13% increase in incremental variance (t = -2.47, p = .02). CONCLUSIONS The findings indicate for the first time in humans that insomnia severity is associated with volume loss of the CA3/dentate subfields. This is consistent with animal studies showing that chronic sleep disruption is associated with decreased neurogenesis and dendritic branching in these structures.

Nonlinear time course of brain volume loss in cognitively normal and impaired elders

The goal was to elucidate the time course of regional brain atrophy rates relative to age in cognitively normal (CN) aging, mild cognitively impairment (MCI), and Alzheimers disease (AD), without a priori models for atrophy progression. Regional brain volumes from 147 cognitively normal subjects, 164 stable MCI, 93 MCI-to-AD converters and 111 ad patients, between 51 and 91 years old and who had repeated 1.5 T magnetic resonance imaging (MRI) scans over 30 months, were analyzed. Relations between regional brain volume change and age were determined using generalized additive models, an established nonparametric concept for approximating nonlinear relations. Brain atrophy rates varied nonlinearly with age, predominantly in regions of the temporal lobe. Moreover, the atrophy rates of some regions leveled off with increasing age in control and stable MCI subjects whereas those rates progressed further in MCI-to-AD converters and AD patients. The approach has potential uses for early detection of AD and differentiation between stable and progressing MCI.

Associations between White Matter Hyperintensities and β Amyloid on Integrity of Projection, Association, and Limbic Fiber Tracts Measured with Diffusion Tensor MRI

The goal of this study was to assess the relationship between Aβ deposition and white matter pathology (i.e., white matter hyperintensities, WMH) on microstructural integrity of the white matter. Fifty-seven participants (mean age: 78±7 years) from an ongoing multi-site research program who spanned the spectrum of normal to mild cognitive impairment (Clinical dementia rating 0–0.5) and low to high risk factors for arteriosclerosis and WMH pathology (defined as WMH volume >0.5% total intracranial volume) were assessed with positron emission tomography (PET) with Pittsburg compound B (PiB) and magnetic resonance and diffusion tensor imaging (DTI). Multivariate analysis of covariance were used to investigate the relationship between Aβ deposition and WMH pathology on fractional anisotropy (FA) from 9 tracts of interest (i.e., corona radiata, internal capsule, cingulum, parahippocampal white matter, corpus callosum, superior longitudinal, superior and inferior front-occipital fasciculi, and fornix). WMH pathology was associated with reduced FA in projection (i.e., internal capsule and corona radiate) and association (i.e., superior longitudinal, superior and inferior fronto-occipital fasciculi) fiber tracts. Aβ deposition (i.e., PiB positivity) was associated with reduced FA in the fornix and splenium of the corpus callosum. There were interactions between PiB and WMH pathology in the internal capsule and parahippocampal white matter, where Aβ deposition reduced FA more among subjects with WMH pathology than those without. However, accounting for apoE ε4 genotype rendered these interactions insignificant. Although this finding suggests that apoE4 may increase amyloid deposition, both in the parenchyma (resulting in PiB positivity) and in blood vessels (resulting in amyloid angiopathy and WMH pathology), and that these two factors together may be associated with compromised white matter microstructural integrity in multiple brain regions, additional studies with a longitudinal design will be necessary to resolve this issue.

Measurement of hippocampal subfields and age-related changes with high resolution MRI at 4tesla

Histological studies suggest that hippocampal subfields are differently affected by aging and Alzheimers disease (AD). The aims of this study were: (1) To test if hippocampal subfields can be identified and marked using anatomical landmarks on high resolution MR images obtained on a 4T magnet. (2) To test if age-specific volume changes of subfields can be detected. Forty-two healthy controls (21-85 years) and three AD subjects (76-86 years) were studied with a high resolution T2 weighted fast spin echo sequence. The entorhinal cortex (ERC), subiculum, CA1, CA2 and CA3/4 and dentate were marked. A significant correlation between age and CA1 (r=-0.51, p=0.0002) which was most pronounced in the seventh decade of life was found in healthy controls. In AD subjects, CA1 and subiculum were smaller than in age-matched controls. These preliminary findings suggest that measurement of hippocampal subfields may be helpful to distinguish between normal aging and AD.