Structural and diffusion MRI measures of the hippocampus and memory performance.

Hippocampal atrophy on MRI and changes in diffusion tensor imaging (DTI) measures of the hippocampus have been reported in patients with Alzheimer's disease. We examined the association between hippocampal volumes, DTI measures of the hippocampus and memory performance in 892 non-demented persons (age ≥ 55 years) across different age groups. Hippocampal volume was segmented on 3D volumetric MRI scans. The segmentations were co-registered to mean diffusivity (MD) and fractional anisotropy (FA) maps to yield mean hippocampal MD and FA measurements. Higher MD of the hippocampus was associated with impaired verbal memory performance. In all persons ≥ 55 years, a higher MD of the hippocampus was associated with a worse memory performance. Hippocampal volumes were very weakly positively associated with delayed recall and only in persons > 65 years. FA of the hippocampus was not associated with memory performance. Follow-up studies will be needed to determine whether higher MD of hippocampus at younger ages could be an earlier marker of incident Alzheimer's disease than hippocampal volume.

Viral encephalitis associated with rituximab maintenance therapy: two cases and a review of literature.

Rituximab is increasingly used in the treatment of CD20-positive B-cell-mediated disease. Prolonged use may cause B-cell dysfunction, dose-dependent T-cell dysfunction, and hypogammaglobulinaemia and result in severe non-neutropenic infections. We present two cases of viral encephalitis in patients treated with rituximab maintenance therapy: one patient presented with deafness; the other patient with paroxysmal light flashes, apraxia, and weakness.

Hippocampal, amygdalar, and global brain atrophy in different apolipoprotein E genotypes.

The epsilon4 allele of the APOE gene increases the risk for AD, whereas the epsilon2 allele may be protective. The authors assessed the impact of APOE genotype on hippocampal, amygdalar, and global brain atrophy as putative markers of preclinical AD in a nondemented population. Carriers of epsilon4 had significantly more hippocampal and amygdalar atrophy than epsilon3epsilon3 subjects, but not more global brain atrophy. Carriers of epsilon2 did not have less brain atrophy than epsilon3epsilon3 subjects.

Homocysteine and cognitive function in the elderly: the Rotterdam Scan Study.

BACKGROUND: Elevated plasma total homocysteine (tHcy) concentrations are associated with AD and vascular dementia, but the relation with cognitive performance in nondemented elderly people is not known. OBJECTIVE: To examine the association of tHcy and cognitive function in the elderly, and assess whether this may be mediated by structural brain changes on MRI. METHODS: The Rotterdam Scan Study is a population-based study of 1,077 nondemented elderly. Cognitive performance was assessed, and compound scores were constructed for psychomotor speed, memory function, and global cognitive function. Cerebral infarcts, white matter lesions, and generalized brain atrophy were measured on MRI. The cross-sectional relationship between tHcy levels and neuropsychological test scores was assessed by multiple regression. RESULTS: Mean tHcy level was 11.5 micro mol/L (SD 4.1). Increasing tHcy levels were associated with lower scores for psychomotor speed, memory function, and global cognitive function, and this was largely due to the association with tHcy levels in the upper quintile (>14 micro mol/L). Adjusted differences between test scores of participants in the upper quintile as compared with the lower four quintiles of tHcy were -0.26 (95% CI: -0.37; -0.14) for psychomotor speed, -0.13 (95% CI: -0.27; 0.01) for memory function, and -0.20 (95% CI: -0.30; -0.11) for global cognitive function. These associations were not mediated by structural brain changes on MRI. CONCLUSION: Elevated tHcy levels are associated with decreased cognitive performance in nondemented elderly people, and the relation was most marked for psychomotor speed. This association was independent of structural brain changes on MRI.

Human brain chemical shift imaging at age 60 to 90: analysis of the causes of the observed sex differences in brain metabolites.

RATIONALE AND OBJECTIVES: To assess whether differences in cerebral atrophy and white matter lesions or in the presence of lactate and lipid signals can explain the observed differences in brain choline, creatine, and N-acetylaspartate levels between healthy elderly women and men. METHODS: In addition to standard magnetic resonance imaging of the brain, an 8 x 8 x 2-cm3 supraventricular transverse brain volume parallel to the canthomeatal line was examined by magnetic resonance spectroscopy (automated 1H chemical shift imaging) in 540 healthy elderly persons. RESULTS: At P = 0.01, 0.001, and 0.0001, choline differed between women and men in 14, 9, and 5 of 36 voxels, respectively. On correction for cerebral atrophy (more frequent in men than in women), white matter lesions (more frequent in women), and lactate and lipid (more frequent in women), the differences in choline were reduced to 13, 6, and 3. Sex differences for creatine and N-acetylaspartate were similar but less numerous after correction. CONCLUSIONS: Elderly women and men in the general population show differences in the levels of creatine, N-acetylaspartate, and especially choline in portions of the brain. The sex-related differences in brain metabolite levels cannot be explained by differences in cerebral atrophy or other aging-related phenomena (white matter lesions, lactate, lipid).

Serum carotenoids and cerebral white matter lesions: the Rotterdam scan study.

OBJECTIVES: To study the relation between serum levels of carotenoids and white matter lesions (WMLs) on magnetic resonance imaging (MRI). DESIGN: Evaluation of cross-sectional data from a cohort study. SETTING: The Rotterdam Scan Study. PARTICIPANTS: Two hundred and three nondemented older persons, age 60 to 90, from the Rotterdam Scan Study. MEASUREMENTS: Serum levels of carotenoids were determined. WMLs on MRIs were rated separately into periventricular and subcortical WMLs. Odds ratios (ORs) for the presence of severe WMLs (upper decile) were calculated per standard deviation (SD) increase in serum carotenoid level and per SD increase in overall carotenoid serum level. Effect modification by smoking status was studied through stratified analyses. RESULTS: Increasing levels of all the separate carotenoids were associated with less severe periventricular WMLs, which reached statistical significance for the overall carotenoid serum level (OR 0.4 per SD; 95% confidence interval (CI) = 0.2-0.9). We found no association between carotenoid levels and the presence of severe subcortical WMLs (OR 1.2 per SD; 95% CI = 0.7-2.0). The association of carotenoid levels with severe periventricular WMLs was more marked in those who ever smoked (OR 0.1 per SD; 95% CI = 0.0-0.9) than in those who had never smoked (OR 0.9 per SD; 95% CI = 0.4-2.1). CONCLUSIONS: These findings are compatible with the view that high levels of carotenoids may protect against WMLs in the periventricular region, in particular in smokers. Longitudinal studies with repeated measurements of both carotenoids and WMLs are necessary to explore this hypothesis further.

History of depression, depressive symptoms, and medial temporal lobe atrophy and the risk of Alzheimer disease.

BACKGROUND: Depression may increase risk for Alzheimer disease (AD), but it is not clear whether this risk is mediated by structural brain changes. We determined whether history of depressive episodes and presence of depressive symptoms were associated with smaller hippocampal and amygdalar volumes and with increased risk for incident AD. METHODS: Within the Rotterdam Scan Study 503 persons, aged 60-90 years at baseline and without dementia, reported their history of depressive episodes. Depressive symptoms were assessed with the Center for Epidemiologic Studies Depression Scale. Volumetric assessment of the hippocampus and amygdala was performed using three-dimensional MRI. All subjects were followed for an average of 6 years for development of AD, diagnosed according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria. RESULTS: A total of 134 subjects (26.6%) reported a history of depression (88 reported an onset <60 years and 46 a late onset). Multiple linear regression analyses did not reveal a significant association with hippocampal or amygdalar volume for any of the depression parameters. During follow-up, 33 persons developed AD. Cox regression analyses showed that subjects with early onset depression had an increased risk for AD (HR 3.76; 95% CI 1.41 to 10.06), independent of hippocampal and amygdalar volume, whereas this risk was 2.34 (95% CI 0.82 to 6.69) in subjects with a late-onset depression. Depressive symptoms at baseline were not associated with increased risk for AD. CONCLUSION: History of depression, and particularly an early onset, but not presence of depressive symptoms increased the risk for Alzheimer disease. This risk was not mediated by smaller hippocampal or amygdalar volumes.

Relation between smoking and risk of dementia and Alzheimer disease: the Rotterdam Study.

BACKGROUND AND OBJECTIVE: Previous studies relating smoking with the risk of dementia have been inconsistent and limited in their validity by short follow-up times, large intervals between baseline and follow-up assessments, and unspecific determination of dementia diagnosis. We re-assessed after longer follow-up time in the large population-based cohort of the Rotterdam Study whether smoking habits and pack-years of smoking are associated with the risk of dementia, Alzheimer disease (AD), and vascular dementia (VaD). METHODS: Prospective population-based cohort study in 6,868 participants, 55 years or older and free of dementia at baseline. First, Cox proportional hazard models were used to relate smoking status at baseline with the risks of incident dementia, VaD, and AD, using never smokers as the reference category in all analyses. Then Cox proportional hazard models were used to relate pack-years of smoking with the risks of incident dementia, VaD, and AD. To explore the impact of the APOEepsilon4 allele, sex, and age on the association between smoking status and dementia, we repeated all analyses stratifying, in separate models, by APOEepsilon4 genotype, sex, and median of age. RESULTS: After a mean follow-up time of 7.1 years, current smoking at baseline was associated with an increased risk of dementia (HR 1.47, 95% CI 1.18 to 1.86) and AD (HR 1.56, 95% CI 1.21 to 2.02). This increase in disease risk was restricted to persons without the APOEepsilon4 allele. There was no association between current smoking and risk of VaD, and there was no association between past smoking and risk of dementia, AD, or VaD. CONCLUSION: Current smoking increases the risk of dementia. This effect is more pronounced in persons without the APOEepsilon4 allele than APOEepsilon4 carriers.

MR spectroscopy of brain white matter in the prediction of dementia.

BACKGROUND: Previous 1H-MR spectroscopy (MRS) studies compared biochemical spectra of persons with dementia with those of healthy control subjects. Given the long prodromal period of Alzheimer disease (AD), the authors sought to investigate whether biochemical changes can be observed also in the preclinical period. METHODS: The authors prospectively followed 509 elderly persons (ages 60 to 90), who were free of clinical dementia at baseline, for on average 5.9 years. At baseline, 1H-MRS of the brain (1.5 T) was performed in a plane above the lateral ventricles that comprised mainly white matter voxels. Standard ratios of N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) were calculated. Structural MRI was administered to assess white matter lesions and hippocampal atrophy. All persons were followed for incident dementia through repeated neuropsychological testing and linkage with medical records. RESULTS: During follow-up, 37 persons developed dementia, of whom 27 fulfilled criteria for AD. Overall, biochemical ratios on 1H-MRS at baseline were not associated with the risk of incident dementia. However, people with higher Cho/Cr ratios had a higher risk to develop dementia or AD within 4 years (hazard ratio for dementia per SD increase 1.55 [95% CI 1.05 to 2.28]). This association attenuated and became nonsignificant after adjustment for white matter lesions on MRI. CONCLUSION: These data suggest that there are biochemical changes on 1H-MR spectroscopy of brains of persons with presymptomatic dementia.

Association between blood pressure, white matter lesions, and atrophy of the medial temporal lobe.

BACKGROUND: Blood pressure level is associated with the risk of clinical Alzheimer disease (AD), yet the underlying mechanisms are unclear. High blood pressure levels may cause cerebral small-vessel pathology, which contributes to cognitive decline in patients with AD. Alternatively, in persons with high blood pressure, increased numbers of neurofibrillary tangles and amyloid plaques at autopsy have also been observed, suggesting direct links between blood pressure and AD. OBJECTIVE: To investigate the association of blood pressure and markers of small-vessel disease (white matter lesions [WMLs] on MRI) with hippocampal and amygdalar atrophy on MRI-potential in vivo indicators of Alzheimer pathology. METHODS: In 1995 to 1996, 511 nondemented elderly subjects (age 60 to 90) underwent MRI. The extent of WMLs was assessed, and volumes of the hippocampus and amygdala were measured. Blood pressure levels were assessed at the time of MRI and 5 years before the MRI. RESULTS: Higher diastolic blood pressure 5 years before MRI predicted more hippocampal atrophy in persons untreated for hypertension (per SD increase -0.10 mL [95% CI -0.19 to -0.02, p = 0.02]). Conversely, in persons treated for hypertension, a low diastolic blood pressure was associated with more severe atrophy. Persons with more WMLs on MRI more often had severe atrophy of the hippocampus and amygdala. CONCLUSION: Blood pressure and indicators of small-vessel disease in the brain may be associated with atrophy of structures affected by Alzheimer pathology.

Hippocampal head size associated with verbal memory performance in nondemented elderly.

The hippocampus plays a crucial role in the consolidation of memory. Anatomically, the hippocampal head, body, and tail are connected to separate regions of the entorhinal cortex, which conveys processed information from the association cortices to the hippocampus. Little is known, however, about the functional segregation along its longitudinal axis. In the present study, we investigated whether the hippocampal head, body, or tail is selectively involved in verbal memory performance. A total of 511 nondemented participants, aged 60-90 years, underwent a three-dimensional HASTE brain scan in a 1.5-T MRI unit. Hippocampal volumes were measured by manual tracing on coronal slices. Segmentation was performed in anterior-posterior direction on the basis of predefined cutoffs allocating 35, 45, and 20% of slices to the head, body, and tail, respectively. Memory performance was assessed by a 15-word learning test including tasks of immediate and delayed recall. To analyze the association between head, body, and tail volumes and memory performance, we used multiple linear regression, adjusting for age, sex, education, and midsagittal area as a proxy for intracranial volume. Participants with larger hippocampal heads scored significantly higher in the memory test, most notably in delayed recall (0.41 word per SD increase in left hippocampal head (95% CI (0.16, 0.67)), 0.33 word per SD increase in right hippocampal head (95% CI 0.06, 0.59)). Our data suggest selective involvement of the hippocampal head in verbal memory, and add to recent findings of functional segregation along the longitudinal axis of the hippocampus.

Type 2 diabetes and atrophy of medial temporal lobe structures on brain MRI.

AIM/HYPOTHESIS: Type 2 diabetes increases the risk not only of vascular dementia but also of Alzheimer's disease. The question remains whether diabetes increases the risk of Alzheimer's disease by diabetic vasculopathy or whether diabetes influences directly the development of Alzheimer neuropathology. In vivo, hippocampal and amygdalar atrophy on brain MRI are good, early markers of the degree of Alzheimer neuropathology. We investigated the association between diabetes mellitus, insulin resistance and the degree of hippocampal and amygdalar atrophy on magnetic resonance imaging (MRI) accounting for vascular pathology. METHODS: Data was obtained in a population-based study of elderly subjects without dementia between 60 to 90 years of age. The presence of diabetes mellitus and, in non-diabetic subjects, insulin resistance was assessed for 506 participants in whom hippocampal and amygdalar volumes on MRI were measured. We assessed the degree of vascular morbidity by rating carotid atherosclerosis, and brain white matter lesions and infarcts on MRI. RESULTS: Subjects with diabetes mellitus had more hippocampal and amygdalar atrophy on MRI compared to subjects without diabetes mellitus. Furthermore, increasing insulin resistance was associated with more amygdalar atrophy on MRI. The associations were not due to vascular morbidity being more pronounced in persons with diabetes mellitus. CONCLUSIONS/INTERPRETATION: Type 2 diabetes is associated with hippocampal and amygdalar atrophy, regardless of vascular pathology. This could suggest that Type 2 diabetes directly influences the development of Alzheimer neuropathology.

Homocysteine and brain atrophy on MRI of non-demented elderly.

Patients with Alzheimer's disease have higher plasma homocysteine levels than controls, but it is uncertain whether higher plasma homocysteine levels are involved in the early pathogenesis of the disease. Hippocampal, amygdalar and global brain atrophy on brain MRI have been proposed as early markers of Alzheimer's disease. In the Rotterdam Scan Study, a population-based study of age-related brain changes in 1077 non-demented people aged 60-90 years, we investigated the association between plasma homocysteine levels and severity of hippocampal, amygdalar and global brain atrophy on MRI. We used axial T(1)-weighted MRIs to visualize global cortical brain atrophy (measured semi-quantitatively; range 0-15) and a 3D HASTE (half-Fourier acquisition single-shot turbo spin echo) sequence in 511 participants to measure hippocampal and amygdalar volumes. We had non-fasting plasma homocysteine levels in 1031 of the participants and in 505 of the participants with hippocampal and amygdalar volumes. Individuals with higher plasma homocysteine levels had, on average, more cortical atrophy [0.23 units (95% CI 0.07-0.38 units) per standard deviation increase in plasma homocysteine levels] and more hippocampal atrophy [difference in left hippocampal volume -0.05 ml (95% CI -0.09 to -0.01) and in right hippocampal volume -0.03 ml (95% CI -0.07 to 0.01) per standard deviation increase in plasma homocysteine levels]. No association was observed between plasma homocysteine levels and amygdalar atrophy. These results support the hypothesis that higher plasma homocysteine levels are associated with more atrophy of the hippocampus and cortical regions in elderly at risk of Alzheimer's disease.

Variations in estrogen receptor alpha gene and risk of dementia, and brain volumes on MRI.

The role of estrogens in Alzheimer's disease (AD) is controversial. We investigated the association between well-recognized, and potentially functional, polymorphisms in the estrogen receptor (ER) alpha gene and the risk of AD in a prospective study of 6056 Caucasian older men and women aged 55 years and over. In a subset of 468 participants, we assessed volumes of the hippocampus and amygdala, which have a high density of ER alpha, with brain magnetic resonance imaging (MRI) (1.5 T MR unit). During a total of 35 405 person-years of follow-up (mean per persons 5.8 years), 312 new cases of dementia were detected, of whom 230 were diagnosed with AD. Neither the PvuII nor the XbaI polymorphism or haplotypes thereof were associated with the risk of all-cause dementia or AD. In contrast, we found that nondemented women who carried the PvuII p allele or haplotype 'px' had smaller amygdalar volumes on MRI in an allele-dose-dependent fashion. Total amygdalar volume was 4.50 (SE 0.10) in PP genotype, 4.45 (SE 0.06) in Pp genotype, and 4.18 ml (SE 0.08) in pp genotype (P trend=0.008). Further studies are required to investigate whether this smaller amygdalar volume has functional significance.

MR spectroscopy detection of lactate and lipid signals in the brains of healthy elderly people.

Magnetic resonance spectroscopy was used to assess the presence of brain lactate and lipid signals, frequently associated with the presence of pathology, in healthy persons of 60-90 years old (n = 540). Lactate and lipid signals were observed in, respectively, 25 and 6% of women, and 18 and 2% of men. Upon adjustment for age, and for MRI-detected cerebral atrophy and white matter lesions, the gender differences in lactate and lipid remained the same (p = 0.05 and p = 0.03, respectively). Brain lactate and lipid signals appear to be intrinsic to aging. However, the presence of these metabolites in very focal areas only, rather than in any distributed fashion within the brain (the latter generally the case with cerebral atrophy and white matter lesions), strongly suggests the existence of asymptomatic focal pathology not shown on MRI.