Neuroimaging in dementia

Rapid eye movement sleep loss associated cytomorphometric changes and neurodegeneration

Rapid eye movement sleep (REMS) is essential for leading normal healthy living at least in higher-order mammals, including humans. In this review, we briefly survey the available literature for evidence linking cytomorphometric changes in the brain due to loss of REMS. As a mechanism of action, we add evidence that REMS loss elevates noradrenaline (NA) levels in the brain, which affects neuronal cytomorphology. These changes may be a compensatory mechanism as the changes return to normal after the subjects recover from the loss of REMS or if during REMS deprivation, the subjects are treated with NA-adrenoceptor antagonist prazosin (PRZ). We had proposed earlier that one of the fundamental functions of REMS is to maintain the level of NA in the brain. We elaborate on this idea to propose that if REMS loss continues without recovery, the sustained level of NA breaks down neurophysiologically active compensatory mechanism/s starting with changes in the neuronal cytomorphology, followed by their degeneration, leading to acute and chronic pathological conditions. Identification of neuronal cytomorphological changes could prove to be of significance for predicting future neuronal (brain) damage as well as an indicator for REMS health. Although current brain imaging techniques may not enable us to visualize changes in neuronal cytomorphology, given the rapid technological progress including use of artificial intelligence, we are optimistic that it may be a reality soon. Finally, we propose that maintenance of optimum REMS must be considered a criterion for leading a healthy life.

The use of MRI, CT and lumbar puncture in dementia diagnostics: data from the SveDem Registry

BACKGROUND/AIMS

The use of structural brain imaging [computed tomography (CT)/magnetic resonance imaging (MRI)] and the analysis of cerebrospinal fluid biomarkers are included in the guidelines for the diagnosis of dementia. The influence of variables such as age, gender and disease severity on the use of MRI, CT and lumbar puncture (LP) for the differential diagnosis of dementia and the consonance with the recommendations of the Swedish national guidelines were investigated.

METHODS

From the National Swedish Dementia Registry (SveDem), 17,057 newly diagnosed dementia patients were included in our study, with the majority from specialist care units (90%).

RESULTS

In the diagnostic workup, a CT was performed in 87%, MRI in 16% and LP in 40% of the cases. Age (p < 0.001) and cognitive status (p < 0.001) significantly influenced the use of MRI, CT or LP. Older patients with severe dementia were often investigated with CT. LP and MRI were used more often when less common dementia disorders were suspected.

CONCLUSION

Our findings indicate that age, severity of cognitive impairment and the type of dementia disorder suspected are determinants for the choice of CT, MRI or LP. The majority of the dementia workups in specialist care units follow the recommendations of the Swedish national guidelines where CT is performed as a basic workup, and MRI and LP are chosen when extended workup is needed. .

Resolution of neuropsychological and FDG-PET abnormalities in a patient with neuropsychiatric systemic lupus erythematosus

Many patients with systemic lupus erythematosus have central nervous system involvement. Routine diagnostic studies may not yield evidence of neuropsychiatric dysfunction and are therefore not useful as objective measures to monitor treatment response. We present a case of a 64-year-old woman whom we diagnosed with systemic lupus erythematosus by the American College of Rheumatology criteria after she reported recent cognitive decline. Neuropsychological assessment showed prominent deficits, and an F-18 fluorodeoxyglucose positron emission tomography scan of the brain showed significant abnormalities. Both the neuropsychiatric and scan abnormalities improved dramatically with immunosuppressive treatment. F-18 fluorodeoxyglucose positron emission tomography shows promise in the diagnosis and treatment monitoring of patients who have lupus with neuropsychiatric involvement.

Effects of MRI scan acceleration on brain volume measurement consistency

PURPOSE

To evaluate the effects of recent advances in magnetic resonance imaging (MRI) radiofrequency (RF) coil and parallel imaging technology on brain volume measurement consistency.

MATERIALS AND METHODS

In all, 103 whole-brain MRI volumes were acquired at a clinical 3T MRI, equipped with a 12- and 32-channel head coil, using the T1-weighted protocol as employed in the Alzheimer's Disease Neuroimaging Initiative study with parallel imaging accelerations ranging from 1 to 5. An experienced reader performed qualitative ratings of the images. For quantitative analysis, differences in composite width (CW, a measure of image similarity) and boundary shift integral (BSI, a measure of whole-brain atrophy) were calculated.

RESULTS

Intra- and intersession comparisons of CW and BSI measures from scans with equal acceleration demonstrated excellent scan-rescan accuracy, even at the highest acceleration applied. Pairs-of-scans acquired with different accelerations exhibited poor scan-rescan consistency only when differences in the acceleration factor were maximized. A change in the coil hardware between compared scans was found to bias the BSI measure.

CONCLUSION

The most important findings are that the accelerated acquisitions appear to be compatible with the assessment of high-quality quantitative information and that for highest scan-rescan accuracy in serial scans the acquisition protocol should be kept as consistent as possible over time.

Multiple pathologies are common in Alzheimer patients in clinical trials

OBJECTIVE

To determine the frequency of multiple pathology [Alzheimer Disease (AD) plus Vascular Dementia and/or Dementia with Lewy Bodies] in patients enrolled in clinical trials of AD therapy, and to compare the cognitive and functional assessments between patients with pure AD and AD with multiple pathology.

METHODS

We conducted a retrospective analysis of patients with a clinical diagnosis of AD who were enrolled in AD therapy clinical trials and subsequently received an autopsy for confirmation of their diagnosis from 2000 to 2009. Performance on cognitive screening tests, namely Modified Mini Mental state (3MS) exam, Mini Mental state Exam (MMSE) and Functional Rating Scale (FRS) were compared between patients with pure AD and multiple pathology.

RESULTS

Autopsy reports were available for 16/47 (34%) of deceased patients. Of these 16 patients, 5 (31%) had pure AD pathology, 10 (63%) had AD with other pathology, and 1 (6%) had non-AD pathology. Compared to patients with pure AD, patients with AD mixed with other pathology had poorer baseline FRS in problem-solving (p<0.01) and community affairs (p<0.02).

CONCLUSION

While the strict enrollment criteria for clinical trials identified the presence of AD pathology in the majority of cases (15/16), multiple pathology was more common than pure AD in our series of autopsied patients. Premortem biomarkers that can distinguish between pure AD and AD with multiple pathology will be beneficial in future clinical trials and dementia patient management.

Characterization of frontotemporal dementia and/or amyotrophic lateral sclerosis associated with the GGGGCC repeat expansion in C9ORF72

Numerous kindreds with familial frontotemporal dementia and/or amyotrophic lateral sclerosis have been linked to chromosome 9, and an expansion of the GGGGCC hexanucleotide repeat in the non-coding region of chromosome 9 open reading frame 72 has recently been identified as the pathogenic mechanism. We describe the key characteristics in the probands and their affected relatives who have been evaluated at Mayo Clinic Rochester or Mayo Clinic Florida in whom the hexanucleotide repeat expansion were found. Forty-three probands and 10 of their affected relatives with DNA available (total 53 subjects) were shown to carry the hexanucleotide repeat expansion. Thirty-six (84%) of the 43 probands had a familial disorder, whereas seven (16%) appeared to be sporadic. Among examined subjects from the 43 families (n = 63), the age of onset ranged from 33 to 72 years (median 52 years) and survival ranged from 1 to 17 years, with the age of onset <40 years in six (10%) and >60 in 19 (30%). Clinical diagnoses among examined subjects included behavioural variant frontotemporal dementia with or without parkinsonism (n = 30), amyotrophic lateral sclerosis (n = 18), frontotemporal dementia/amyotrophic lateral sclerosis with or without parkinsonism (n = 12), and other various syndromes (n = 3). Parkinsonism was present in 35% of examined subjects, all of whom had behavioural variant frontotemporal dementia or frontotemporal dementia/amyotrophic lateral sclerosis as the dominant clinical phenotype. No subject with a diagnosis of primary progressive aphasia was identified with this mutation. Incomplete penetrance was suggested in two kindreds, and the youngest generation had significantly earlier age of onset (>10 years) compared with the next oldest generation in 11 kindreds. Neuropsychological testing showed a profile of slowed processing speed, complex attention/executive dysfunction, and impairment in rapid word retrieval. Neuroimaging studies showed bilateral frontal abnormalities most consistently, with more variable degrees of parietal with or without temporal changes; no case had strikingly focal or asymmetric findings. Neuropathological examination of 14 patients revealed a range of transactive response DNA binding protein molecular weight 43 pathology (10 type A and four type B), as well as ubiquitin-positive cerebellar granular neuron inclusions in all but one case. Motor neuron degeneration was detected in nine patients, including five patients without ante-mortem signs of motor neuron disease. While variability exists, most cases with this mutation have a characteristic spectrum of demographic, clinical, neuropsychological, neuroimaging and especially neuropathological findings.

Advances in structural and molecular neuroimaging in Alzheimer's disease

Longer life expectancies lead to increases in the prevalence of age-associated illnesses. The number of Australians with dementia is predicted to rise, from 234,000 in 2009 to over 1 million by 2050, as a result of the increased prevalence of Alzheimer's disease (AD), the leading cause of dementia in the elderly. Early diagnosis of AD will become more important as disease-modifying therapies emerge within the next decade. Advances in molecular neuroimaging with amyloid-β-specific radioligands for positron emission tomography, aided by magnetic resonance imaging techniques, allow detection of AD years before symptoms of dementia develop. Longitudinal prospective studies, such as the Australian Imaging Biomarkers and Lifestyle (AIBL) study of ageing, will determine the sensitivity and specificity of these analysis techniques for diagnosing AD and predicting cognitive decline.

Voxel-based morphometric study of brain volume changes in patients with Alzheimer's disease assessed according to the Clinical Dementia Rating score

We evaluated the volume reduction of gray matter (GM) and white matter (WM) in patients with an Alzheimer's disease (AD) assessment based on the Clinical Dementia Rating (CDR) score. Patients with AD (n=61), with no subcortical WM ischemia, and healthy control patients (n=33) underwent T1-weighted spoiled gradient echo sequences, which were analyzed using voxel-based morphometry. Global GM volume reduction was observed in patients with a CDR score of 1 or a CDR score of 2, and WM volume reduction was observed in patients with a CDR score of 2. Regional GM volume reduction was found in the right inferior frontal gyrus, bilateral dorso-lateral and medial temporal lobes; WM volume reduction was found in the bilateral temporal subcortex (family-wise error, p<0.01). A CDR score of 0.5 was associated with volume reduction in the left olfactory gyrus. The peak z-score and spatial extent of volume reduction increased with increasing CDR score and were higher on the left side. GM volume reduction increased with increasing CDR scores and suggests a possible pathomechanism of AD.

Measurement of precuneal and hippocampal volumes using magnetic resonance volumetry in Alzheimer's disease

Background and Purpose

Alzheimer's disease (AD) is associated with structural alterations in the medial temporal lobe (MTL) and functional alterations in the posterior cortical region, especially in the early stages. However, it is unclear what mechanisms underlie these regional discrepancies or whether the posterior cortical hypometabolism reflects disconnection from the MTL lesion or is the result of local pathology. The precuneus, an area of the posteromedial cortex that is involved in the early stages of AD, has recently received a great deal of attention in functional neuroimaging studies. To assess the relationship between the precuneus and hippocampus in AD, we investigated the volumes of these two areas using a magnetic resonance volumetric method.

Methods

Twenty-three subjects with AD and 14 healthy age-matched controls underwent T1-weighted three-dimensional volumetric brain magnetic resonance imaging. Volumetric measurements were performed in the precuneus and hippocampus.

Results

Compared to controls, AD patients exhibited a significant reduction in total precuneal volume, which was more prominent on the right side, and significant bilateral reductions in hippocampal volume. No correlation was found between the total volumes of the precuneus and hippocampus in the AD group.

Conclusions

These results suggest that volumetric measurements of both the precuneus and hippocampus are useful radiological indices for the diagnosis of AD. Furthermore, the lack of correlation is attributable to local pathology rather than being a secondary consequence of MTL pathology.

The value of PET in mild cognitive impairment, typical and atypical/unclear dementias: A retrospective memory clinic study

This retrospective study examined the role of [(18)F]fluorodeoxyglucose positron emission tomography (FDG-PET) in the diagnosis of atypical/unclear dementias in a memory clinic setting. A total of 94 patients with a diagnosis of mild cognitive impairment (MCI) or dementia, who had a PET study within 2 months of their diagnosis, were reevaluated at 5 and 18 months. Results showed that PET was associated with a change in diagnosis in 29% of patients and a 64% increase in the use of cholinesterase inhibitors (ChEIs). PET significantly lowered the number of atypical/unclear diagnoses from 39.4% to 16% and nearly 30% of these were found to have a typical Alzheimer's disease (AD) pattern of hypometabolism. In conclusion, the addition of PET to the investigation of atypical/unclear cases of dementia helped generating a more accurate diagnosis and initiating earlier treatment. PET was of limited contribution to typical AD and frontotemporal dementia (FTD) cases. This study provides guiding evidence about the true value of PET imaging in the day-to-day challenge of dementia diagnosis.

Brain morphology in older African Americans, Caribbean Hispanics, and whites from northern Manhattan

BACKGROUND

Aging is accompanied by a decrease in brain volume and by an increase in cerebrovascular disease.

OBJECTIVE

To examine the effects of age, sex, race/ethnicity, and vascular disease history on measures of brain morphology, including relative brain volume, ventricular volume, hippocampus and entorhinal cortex volumes, and white matter hyperintensity (WMH) burden, in a large community-based cohort of racially/ethnically diverse older adults without dementia.

DESIGN

The associations of age, sex, race/ethnicity, and self-reported vascular disease history with brain morphology were examined in a cross-sectional study using multiple linear regression analyses. Sex x race/ethnicity interactions were also considered.

SETTING

The Washington Heights-Inwood Columbia Aging Project, a community-based epidemiological study of older adults from 3 racial/ethnic groups (white, Hispanic, and African American) from northern Manhattan.

PARTICIPANTS

Beginning in 2003, high-resolution quantitative magnetic resonance (MR) images were acquired in 769 participants without dementia.

MAIN OUTCOME MEASURES

Relative brain volume (total brain volume/intracranial volume), ventricular volume, and hippocampus and entorhinal cortex volumes were derived manually on high-resolution MR images. White matter hyperintensities were quantified semiautomatically on fluid-attenuated inversion recovery-T2-weighted MR images.

RESULTS

Older age was associated with decreased relative brain volume and with increased ventricular and WMH volumes. Hispanic and African American participants had larger relative brain volumes and more severe WMH burden than white participants, but the associations of these variables with age were similar across racial/ethnic groups. Compared with men, women had larger relative brain volumes. Vascular disease was associated with smaller relative brain volume and with higher WMH burden, particularly among African Americans.

CONCLUSIONS

Older age and vascular disease, particularly among African Americans, are associated with increased brain atrophy and WMH burden. African American and Hispanic subjects have larger relative brain volumes and more WMH than white subjects. Racial/ethnic group differences in WMH severity seem to be partially attributable to differences in vascular disease. Future work will focus on the determinants and cognitive correlates of these differences.