Focal atrophy on MRI and neuropathologic classification of dementia with Lewy bodies

Role of neuroimaging in multidisciplinary approach towards Non-Alzheimer's dementia

Dementia is defined as chronic deterioration of intellectual function and cognitive skills significant enough to interfere with the ability to perform daily activities. Recent advances in the treatment of dementia have renewed interest in the use of various neuroimaging techniques that can assist in the diagnosis and differentiation of various subtypes. Neuroimaging and computational techniques have helped the radiological community to monitor disease progression of various neurodegenerative conditions presenting with dementia, such as Alzheimer disease, frontotemporal lobe dementia (FTLD), progressive supranuclear palsy (PSP) and multisystem atrophy-cerebellar variant (MSA-C), and their response to newer therapies. Prompt identification of treatable or reversible forms of dementia, such as tumours, subdural haemorrhage and intracranial dAVF, is crucial for the effective management of these conditions. It is also prudent to recognize the imaging spectrum of metabolic, infective and autoimmune diseases with rapidly progressing dementia, such as methanol toxicity, central pontine myelinolysis (CPM), delayed post hypoxic leukoencephalopathy (DPHL), HIV, Creutzfeldt-Jakob Disease (CJD), Sjogren's syndrome, multiple sclerosis (MS), radiation necrosis and Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS), which are difficult to treat and often require palliative care. This pictorial review emphasizes various non-Alzheimer’s dementia entities and discusses their imaging highlights.

Teaching Points

• Non Alzheimer’s dementia constitutes a broad spectrum of conditions.

• Neuroimaging plays an important role in differentiating treatable from irreversible dementia.

• Neuroimaging is often non-specific in early stages of neurodegenerative conditions with dementia.

• Neuroimaging plays an important role in the multimodal approach towards management of dementia.

Neuropathologic correlates of regional brain volumes in a community cohort of older adults

The objective of this work was 2-fold: to generate macrostructural brain signatures of age-related neuropathologies in a community cohort of older adults and to determine the contribution of brain macrostructure to the variation in antemortem cognition after accounting for the contributions of neuropathologies and demographics. Cerebral hemispheres from 165 participants of 2 cohort studies of aging were imaged with magnetic resonance imaging ex vivo (mean age at death = 90 years; standard deviation = 6 years). The volumes of white matter and 42 gray matter regions were measured. The same hemispheres also underwent neuropathologic examination. Alzheimer's disease pathology was negatively associated with volumes of mainly temporal, frontal, and parietal gray matter regions, and with total white matter volume (p < 0.05, false discovery rate-corrected). A negative association was also detected between hippocampal sclerosis and volumes of the hippocampus, as well as other temporal and frontal gray matter regions (p < 0.05, false discovery rate-corrected). The volume of mainly medial temporal lobe regions explained an additional 5%-6% of the variation in antemortem cognition, above and beyond what was explained by neuropathologies and demographics.

Olfactory function and neuropsychological profile to differentiate dementia with Lewy bodies from Alzheimer's disease in patients with mild cognitive impairment: A 5-year follow-up study

BACKGROUND

Mild cognitive impairment (MCI) is a well-known precursor of Alzheimer's disease (AD) but often also precedes dementia with Lewy bodies (DLB). The early differentiation of DLB from AD is important to delay disease progression. Olfactory dysfunction is a well-known early sign of both AD and Lewy body disorders, including Parkinson's disease (PD) and DLB. Thus, the aim of the present study was to determine whether olfactory and neuropsychological tests can aid in the differentiation of DLB from AD at the MCI stage.

METHODS

The present study included 122 MCI patients who were monitored until they developed dementia or until their condition stabilized; the follow-up period averaged 4.9 years (range: 3.9-6.2 years). Baseline olfactory function as measured with the Cross-Cultural Smell Identification (CCSI) test and neuropsychological data were compared.

RESULTS

During the follow-up period, 32 subjects developed probable AD (MCI-AD), 18 had probable DLB (MCI-DLB), 45 did not convert to dementia (MCI-stable), and eight developed a non-AD/DLB dementia. The mean CCSI score (95% confidence interval [CI]) in patients with MCI-DLB (4.6; 95% CI: 4.0-5.3) was significantly lower than that of MCI-AD patients (6.4; 95% CI: 6.0-6.7, p<0.001) and MCI-stable patients (7.3; 95% CI: 6.9-7.8, p<0.001). The area under the curve of the receiver operating characteristic to discriminate MCI-DLB from MCI-AD using CCSI scores was (0.84; 95% CI: 0.72-0.97). Frontal-executive function and visuospatial ability was worse in patients with MCI-DLB, while verbal recognition memory impairment was greater in those with MCI-AD.

CONCLUSION

Olfactory and neuropsychological tests can help predict conversion to DLB or AD in patients with MCI.

White matter integrity in dementia with Lewy bodies: a voxel-based analysis of diffusion tensor imaging

Many patients with dementia with Lewy bodies (DLB) have overlapping Alzheimer's disease (AD)-related pathology, which may contribute to white matter (WM) diffusivity alterations on diffusion tensor imaging (DTI). Consecutive patients with DLB (n = 30), age- and sex-matched AD patients (n = 30), and cognitively normal controls (n = 60) were recruited. All subjects underwent DTI, 18F 2-fluoro-deoxy-d-glucose, and (11)C Pittsburgh compound B positron emission tomography scans. DLB patients had reduced fractional anisotropy (FA) in the parietooccipital WM but not elsewhere compared with cognitively normal controls, and elevated FA in parahippocampal WM compared with AD patients, which persisted after controlling for β-amyloid load in DLB. The pattern of WM FA alterations on DTI was consistent with the more diffuse posterior parietal and occipital glucose hypometabolism of 2-fluoro-deoxy-d-glucose positron emission tomography in the cortex. DLB is characterized by a loss of parietooccipital WM integrity, independent of concomitant AD-related β-amyloid load. Cortical glucose hypometabolism accompanies WM FA alterations with a concordant pattern of gray and WM involvement in the parietooccipital lobes in DLB.

Brain imaging in the differential diagnosis of young-onset dementias

Young-onset dementia is a broad category of diseases that affect adults before the age of 65, with devastating effects on individuals and families. Neuroimaging plays a clear and ever-expanding role in the workup of these diseases. MRI demonstrates classic patterns of atrophy that help to confirm the clinical diagnosis and may predict the underlying disease. Functional nuclear imaging, such as PET, demonstrates areas of brain dysfunction even in the absence of visible atrophy. These techniques can inform important aspects of the care of young-onset dementia, such as the underlying pathologic condition, treatment, and prognosis.

Assessment of regional gray matter loss in dementia with Lewy bodies: a surface-based MRI analysis

OBJECTIVE

To compare magnetic resonance imaging (MRI) patterns of cortical thinning in subjects with dementia with Lewy bodies (DLB), Alzheimer's disease (AD), and normal aging and investigate the relationship between cortical thickness and clinical measures.

METHODS

Study participants (31 DLB, 30 AD, and 33 healthy comparison subjects) underwent 3-Tesla T1-weighted MRI and completed clinical and cognitive assessments. We used the FreeSurfer analysis package to measure cortical thickness and investigated the patterns of cortical thinning across groups.

RESULTS

Cortical thinning in AD was found predominantly in the temporal and parietal areas extending into the frontal lobes (N = 63, df = 59, t >3.3, p <0.005, FDR-corrected). In DLB, cortical thinning was less diffuse with focal areas of cortical change predominantly affecting posterior structures (inferior parietal, posterior cingulate, and fusiform gyrus) (N = 64, df = 60, t >3.6, p <0.005, FDR-corrected). The average reduction in cortical thickness in medial temporal lobe structures was less in DLB (6%-10%) than in AD (15%-24%), and similar to the reduction in cortical thickness observed in other regions including inferior parietal, precuneus, and posterior cingulate (6%-9%). Associations between cortical thickness and clinical measures (MMSE and verbal fluency) were also observed in DLB (N = 31, df = 27, t >2.8, p <0.01 uncorrected).

CONCLUSION

Cortical thickness may be a sensitive measure for characterising gray matter loss in DLB and highlights important structural imaging differences between the conditions.

Dementia with Lewy bodies: basis of cingulate island sign

OBJECTIVES

To investigate clinical, imaging, and pathologic associations of the cingulate island sign (CIS) in dementia with Lewy bodies (DLB).

METHODS

We retrospectively identified and compared patients with a clinical diagnosis of DLB (n=39); patients with Alzheimer disease (AD) matched by age, sex, and education (n=39); and cognitively normal controls (n=78) who underwent 18F-fluorodeoxyglucose (FDG) and C11 Pittsburgh compound B (PiB)-PET scans. Among these patients, we studied those who came to autopsy and underwent Braak neurofibrillary tangle (NFT) staging (n=10).

RESULTS

Patients with a clinical diagnosis of DLB had a higher ratio of posterior cingulate to precuneus plus cuneus metabolism, cingulate island sign (CIS), on FDG-PET than patients with AD (p<0.001), a finding independent of β-amyloid load on PiB-PET (p=0.56). Patients with CIS positivity on visual assessment of FDG-PET fit into the group of high- or intermediate-probability DLB pathology and received clinical diagnosis of DLB, not AD. Higher CIS ratio correlated with lower Braak NFT stage (r=-0.96; p<0.001).

CONCLUSIONS

Our study found that CIS on FDG-PET is not associated with fibrillar β-amyloid deposition but indicates lower Braak NFT stage in patients with DLB. Identifying biomarkers that measure relative contributions of underlying pathologies to dementia is critical as neurotherapeutics move toward targeted treatments.

Pattern of brain atrophy rates in autopsy-confirmed dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is characterized by preserved whole brain and medial temporal lobe volumes compared with Alzheimer's disease dementia (AD) on magnetic resonance imaging. However, frequently coexistent AD-type pathology may influence the pattern of regional brain atrophy rates in DLB patients. We investigated the pattern and magnitude of the atrophy rates from 2 serial MRIs in autopsy-confirmed DLB patients (n = 20) and mixed DLB/AD patients (n = 22), compared with AD (n = 30) and elderly nondemented control subjects (n = 15), followed antemortem. DLB patients without significant AD-type pathology were characterized by lower global and regional rates of atrophy, similar to control subjects. The mixed DLB/AD patients displayed greater atrophy rates in the whole brain, temporoparietal cortices, hippocampus and amygdala, and ventricle expansion, similar to AD patients. In the DLB and DLB/AD patients, the atrophy rates correlated with Braak neurofibrillary tangle stage, cognitive decline, and progression of motor symptoms. Global and regional atrophy rates are associated with AD-type pathology in DLB, and these rates can be used as biomarkers of AD progression in patients with LB pathology.

Comparison of (123)I-MIBG myocardial scintigraphy, brain perfusion SPECT, and voxel-based MRI morphometry for distinguishing between dementia with Lewy bodies and Alzheimer's disease

OBJECTIVE

This study aimed to compare the diagnostic value of (123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy, N-isopropyl-p[(123)I]iodoamphetamine (IMP) brain perfusion single-photon emission computed tomography (SPECT), and brain magnetic resonance imaging (MRI) voxel-based morphometry (VBM) for the differentiation of dementia with Lewy bodies (DLB) and Alzheimer's disease (AD).

METHODS

Thirty-five and 34 patients with probable DLB and probable AD, respectively, were enrolled. All patients underwent (123)I-MIBG myocardial scintigraphy, (123)I-IMP brain perfusion SPECT, and brain MRI. For (123)I-MIBG imaging, we calculated early and delayed heart-to-mediastinum (H/M) uptake ratios. Three-dimensional stereotactic surface projections (3D-SSP) were used to analyze the results of (123)I-IMP SPECT. VBM with statistical parametric mapping 8 plus diffeomorphic anatomical registration using exponentiated Lie algebra (DARTEL) was used to analyze the brain MRI data.

RESULTS

The area under the receiver operating characteristic curves (AUC) for discriminating DLB and AD was highest (0.882) for the delayed H/M ratio on (123)I-MIBG scintigraphy. AUC for z-score measurement in the occipital lobe was 0.818 and that for the extent of gray matter (GM) atrophy in the whole brain was 0.788. AUC for the combination of 3D-SSP and VBM analysis was 0.836. The respective sensitivities and specificities for distinguishing DLB from AD were 97.1 and 100 % for the delayed H/M ratio using (123)I-MIBG scintigraphy; 88.6 and 73.5 % for the occipital lobe z-score using 3D-SSP analysis; 85.7 and 64.7 % for the extent of whole brain GM atrophy using voxel-based MRI morphometry; and 91.4 and 76.5 % for the combination of 3D-SSP analysis and VBM.

CONCLUSIONS

(123)I-MIBG myocardial scintigraphy was superior to brain perfusion SPECT and brain MRI using an advanced statistical technique to differentiate DLB and AD.

Neuroimaging characteristics of dementia with Lewy bodies

This review summarises the findings and applications from neuroimaging studies in dementia with Lewy bodies (DLB), highlighting key differences between DLB and other subtypes of dementia. We also discuss the increasingly important role of imaging biomarkers in differential diagnosis and outline promising areas for future research in DLB. DLB shares common clinical, neuropsychological and pathological features with Parkinson’s disease dementia and other dementia subtypes, such as Alzheimer’s disease. Despite the development of consensus diagnostic criteria, the sensitivity for differential diagnosis of DLB in clinical practice remains low and many DLB patients will be misdiagnosed. The importance of developing accurate imaging markers in dementia is highlighted by the potential for treatments targeting specific molecular abnormalities as well as the responsiveness to cholinesterase inhibitors and marked neuroleptic sensitivity of DLB. We review various brain imaging techniques that have been applied to investigate DLB, including the characteristic nigrostriatal degeneration in DLB using positron emission tomography (PET) and single-photon emission computed tomography (SPECT) tracers. Dopamine transporter loss has proven to reliably differentiate DLB from other dementias and has been incorporated into the revised clinical diagnostic criteria for DLB. To date, this remains the 'gold standard' for diagnostic imaging of DLB. Regional cerebral blood flow, 18 F-fluorodeoxygluclose-PET and SPECT have also identified marked deficits in the occipital regions with relative sparing of the medial temporal lobe when compared to Alzheimer’s disease. In addition, structural, diffusion, and functional magnetic resonance imaging techniques have shown alterations in structure, white matter integrity, and functional activity in DLB. We argue that the multimodal identification of DLB-specific biomarkers has the potential to improve ante-mortem diagnosis and contribute to our understanding of the pathological background of DLB and its progression.

Neuroimaging in dementia

Over the last few years, advances in neuroimaging have generated biomarkers, which increase diagnostic certainty, provide valuable information about prognosis, and suggest a particular pathology underlying the clinical dementia syndrome. We aim to review the evidence for use of already established imaging modalities, along with selected techniques that have a great potential to guide clinical decisions in the future. We discuss structural, functional and molecular imaging, focusing on the most common dementias: Alzheimer's disease, fronto-temporal dementia, dementia with Lewy bodies and vascular dementia. Finally, we stress the importance of conducting research using representative cohorts and in a naturalistic set up, in order to build a strong evidence base for translating imaging methods for a National Health Service. If we assess a broad range of patients referred to memory clinic with a variety of imaging modalities, we will make a step towards accumulating robust evidence and ultimately closing the gap between the dramatic advances in neurosciences and meaningful clinical applications for the maximum benefit of our patients.

Molecular imaging of Alzheimer disease pathology

Development of molecular imaging agents for fibrillar β-amyloid positron-emission tomography during the past decade has brought molecular imaging of Alzheimer disease pathology into the spotlight. Large cohort studies with longitudinal follow-up in cognitively normal individuals and patients with mild cognitive impairment and Alzheimer disease indicate that β-amyloid deposition can be detected many years before the onset of symptoms with molecular imaging, and its progression can be followed longitudinally. The utility of β-amyloid PET in the differential diagnosis of Alzheimer disease is greatest when there is no pathologic overlap between 2 dementia syndromes, such as in frontotemporal lobar degeneration and Alzheimer disease. However β-amyloid PET alone may be insufficient in distinguishing dementia syndromes that commonly have overlapping β-amyloid pathology, such as dementia with Lewy bodies and vascular dementia, which represent the 2 most common dementia pathologies after Alzheimer disease. The role of molecular imaging in Alzheimer disease clinical trials is growing rapidly, especially in an era when preventive interventions are designed to eradicate the pathology targeted by molecular imaging agents.

Regional proton magnetic resonance spectroscopy patterns in dementia with Lewy bodies

Magnetic resonance spectroscopy (MRS) characteristics of dementia with Lewy bodies (DLB) Alzheimer's disease (AD) and cognitively normal controls were compared. DLB (n = 34), AD (n = 35), and cognitively normal controls (n = 148) participated in a MRS study from frontal, posterior cingulate, and occipital voxels. We investigated DLB patients with preserved hippocampal volumes to determine the MRS changes in DLB with low probability of overlapping AD pathology. DLB patients were characterized by decreased N-acetylaspartate/creatine (NAA/Cr) in the occipital voxel. AD patients were characterized by lower NAA/Cr in the frontal and posterior cingulate voxels. Normal NAA/Cr levels in the frontal voxel differentiated DLB patients with preserved hippocampal volumes from AD patients. DLB and AD patients had elevated choline/creatine, and myo-Inositol/creatine in the posterior cingulate. MRS abnormalities associated with loss of neuronal integrity localized to the occipital lobes in DLB, and the posterior cingulate gyri and frontal lobes in AD. This pattern of MRS abnormalities may have a role in differential diagnosis of DLB and in distinguishing DLB patients with overlapping AD pathology.

Effects of baseline CSF α-synuclein on regional brain atrophy rates in healthy elders, mild cognitive impairment and Alzheimer's disease

Background

Cerebrospinal fluid (CSF) α-synuclein is reduced in synucleinopathies, including dementia with Lewy bodies, and some studies have found increased CSF α-synuclein in Alzheimer’s disease (AD). No study has explored effects of CSF α-synuclein on brain atrophy. Here we tested if baseline CSF α-synuclein affects brain atrophy rates and if these effects vary across brain regions, and across the cognitive spectrum from healthy elders (NL), to patients with mild cognitive impairment (MCI) and AD.

Methods

Baseline CSF α-synuclein measurements and longitudinal structural brain magnetic resonance imaging was performed in 74 NL, 118 MCI patients and 55 AD patients. Effects of baseline CSF α-synuclein on regional atrophy rates were tested in 1) four pre-hoc defined regions possibly associated with Lewy body and/or AD pathology (amygdala, caudate, hippocampus, brainstem), and 2) all available regions of interest. Differences across diagnoses were tested by assessing the interaction of CSF α-synuclein and diagnosis (testing NL versus MCI, and NL versus AD).

Results

The effects of CSF α-synuclein on longitudinal atrophy rates were not significant after correction for multiple comparisons. There were tendencies for effects in AD in caudate (higher atrophy rates in subjects with higher CSF α-synuclein, P=0.046) and brainstem (higher atrophy rates in subjects with lower CSF α-synuclein, P=0.063). CSF α-synuclein had significantly different effects on atrophy rates in NL and AD in brainstem (P=0.037) and caudate (P=0.006).

Discussion: With the possible exception of caudate and brainstem, the overall weak effects of CSF α-synuclein on atrophy rates in NL, MCI and AD argues against CSF α-synuclein as a biomarker related to longitudinal brain atrophy in these diagnostic groups. Any effects of CSF α-synuclein may be attenuated by possible simultaneous occurrence of AD-related neuronal injury and concomitant Lewy body pathology, which may elevate and reduce CSF α-synuclein levels, respectively.

Nonamnestic mild cognitive impairment progresses to dementia with Lewy bodies

OBJECTIVE

To determine the rate of progression of mild cognitive impairment (MCI) to dementia with Lewy bodies (DLB).

METHODS

We followed 337 patients with MCI in the Mayo Alzheimer's Disease Research Center (range 2-12 years). Competing risks survival models were used to examine the rates of progression to clinically probable DLB and Alzheimer disease (AD). A subset of patients underwent neuropathologic examination.

RESULTS

In this clinical cohort, 116 remained as MCI, while 49 progressed to probable DLB, 162 progressed to clinically probable AD, and 10 progressed to other dementias. Among nonamnestic MCI, progression rate to probable DLB was 20 events per 100 person-years and to probable AD was 1.6 per 100 person-years. Among amnestic MCI, progression rate to probable AD was 17 events per 100 person-years, and to DLB was 1.5 events per 100 person-years. In 88% of those who developed probable DLB, the baseline MCI diagnosis included attention and/or visuospatial deficits. Those who developed probable DLB were more likely to have baseline daytime sleepiness and subtle parkinsonism. In 99% of the clinically probable AD group, the baseline MCI diagnosis included memory impairment. Neuropathologic confirmation was obtained in 24 of 30 of those with clinically probable AD, and in 14 of 18 of those with clinically probable DLB.

CONCLUSION

In a clinical sample, patients with nonamnestic MCI were more likely to develop DLB, and those with amnestic MCI were more likely to develop probable AD.

Clinical and multimodal biomarker correlates of ADNI neuropathological findings

Background

Autopsy series commonly report a high percentage of coincident pathologies in demented patients, including patients with a clinical diagnosis of dementia of the Alzheimer type (DAT). However many clinical and biomarker studies report cases with a single neurodegenerative disease. We examined multimodal biomarker correlates of the consecutive series of the first 22 Alzheimer’s Disease Neuroimaging Initiative autopsies. Clinical data, neuropsychological measures, cerebrospinal fluid Aβ, total and phosphorylated tau and α-synuclein and MRI and FDG-PET scans.

Results

Clinical diagnosis was either probable DAT or Alzheimer’s disease (AD)-type mild cognitive impairment (MCI) at last evaluation prior to death. All patients had a pathological diagnosis of AD, but only four had pure AD. A coincident pathological diagnosis of dementia with Lewy bodies (DLB), medial temporal lobe pathology (TDP-43 proteinopathy, argyrophilic grain disease and hippocampal sclerosis), referred to collectively here as MTL, and vascular pathology were present in 45.5%, 40.0% and 22.7% of these patients, respectively. Hallucinations were a strong predictor of coincident DLB (100% specificity) and a more severe dysexecutive profile was also a useful predictor of coincident DLB (80.0% sensitivity and 83.3% specificity). Occipital FDG-PET hypometabolism accurately classified coincident DLB (80% sensitivity and 100% specificity). Subjects with coincident MTL showed lower hippocampal volume.

Conclusions

Biomarkers can be used to independently predict coincident AD and DLB pathology, a common finding in amnestic MCI and DAT patients. Cohorts with comprehensive neuropathological assessments and multimodal biomarkers are needed to characterize independent predictors for the different neuropathological substrates of cognitive impairment.

MRI and pathology of REM sleep behavior disorder in dementia with Lewy bodies

OBJECTIVE

To determine structural MRI and digital microscopic characteristics of REM sleep behavior disorder in individuals with low-, intermediate-, and high-likelihood dementia with Lewy bodies (DLB) at autopsy.

METHODS

Patients with autopsy-confirmed low-, intermediate-, and high-likelihood DLB, according to the probability statement recommended by the third report of the DLB Consortium, and antemortem MRI, were identified (n = 75). The clinical history was assessed for presence (n = 35) and absence (n = 40) of probable REM sleep behavior disorder (pRBD), and patients' antemortem MRIs were compared using voxel-based morphometry. Pathologic burdens of phospho-tau, β-amyloid, and α-synuclein were measured in regions associated with early neuropathologic involvement, the hippocampus and amygdala.

RESULTS

pRBD was present in 21 patients (60%) with high-likelihood, 12 patients (34%) with intermediate-likelihood, and 2 patients (6%) with low-likelihood DLB. Patients with pRBD were younger, more likely to be male (p ≤ 0.001), and had a more frequent neuropathologic diagnosis of diffuse (neocortical) Lewy body disease. In the hippocampus and amygdala, phospho-tau and β-amyloid burden were lower in patients with pRBD compared with those without pRBD (p < 0.01). α-Synuclein burden did not differ in the hippocampus, but trended in the amygdala. Patients without pRBD had greater atrophy of temporoparietal cortices, hippocampus, and amygdala (p < 0.001) than those with pRBD; atrophy of the hippocampus (p = 0.005) and amygdala (p = 0.02) were associated with greater phospho-tau burdens in these regions.

CONCLUSION

Presence of pRBD is associated with a higher likelihood of DLB and less severe Alzheimer-related pathology in the medial temporal lobes, whereas absence of pRBD is characterized by Alzheimer-like atrophy patterns on MRI and increased phospho-tau burden.

Neuropsychiatric features of frontal lobe dysfunction in autopsy-confirmed patients with lewy bodies and "pure" Alzheimer disease

OBJECTIVE

To compare patients with autopsy-confirmed Alzheimer disease (AD) and dementia with Lewy bodies (DLB) on the frequency of behaviors related to frontal system dysfunction and the association of these behaviors with dementia severity.

METHODS

We performed a cross-sectional survey of a longitudinal cohort at a university research center for AD on a volunteer sample of 19 DLB and 38 AD participants with autopsy-confirmed diagnoses, similar in age (DLB: 77.3, AD: 77.5), education (DLB: 15.2, AD: 14.7), and Mini-Mental State Examination (MMSE) score (DLB: 20.6, AD: 20.5), with impairment ranging from mild deficits to moderate dementia. The Frontal Systems Behavior Scale (FrSBe)-Family Rating Form assessing patient apathy, disinhibition, and executive dysfunction by a knowledgeable informant was used.

RESULTS

A two-way analysis of variance with the FrSBe total as the dependent variable revealed a significant MMSE by diagnosis interaction (F(1,53) = 9.34, p = 0.004). Mean FrSBe total for AD patients showed significant impairment across the range of dementia severity, whereas it was relatively preserved for DLB patients in the early stage of disease. The interaction term showed the same pattern for the executive dysfunction (F(1,53) = 7.62, p = 0.008), disinhibition (F(1,53) = 4.90, p = 0.031), and apathy (F(1,53) = 9.77, p = 0.003) subscales.

CONCLUSION

Although frontal behavioral symptoms in AD patients were present regardless of stage of dementia, DLB patients showed significant frontal dysfunction only in later stages. Results suggest that frontal subcortical circuits associated with behaviors assessed by the FrSBe are affected early in AD but not until later stages in DLB. Assessing specific behaviors related to frontal systems, coupled with stage of cognitive decline, may aid in clinical differentiation of AD and DLB.

Magnetic resonance spectroscopy in common dementias

Neurodegenerative dementias are characterized by elevated myoinositol and decreased N-acetylaspartate (NAA) levels. The increase in myoinositol seems to precede decreasing NAA levels in Alzheimer's diseases. NAA/myo-inositol ratio in the posterior cingulate gyri decreases with increasing burden of Alzheimer's disease pathologic conditions. Proton magnetic resonance spectroscopy ((1)H MRS) is sensitive to the pathophysiologic processes associated with the risk of dementia in patients with mild cognitive impairment. Although significant progress has been made in improving the acquisition and analysis techniques in (1)H MRS, translation of these technical developments to clinical practice have not been effective because of the lack of standardization for multisite applications and normative data and an insufficient understanding of the pathologic basis of (1)H MRS metabolite changes.

Brain injury biomarkers are not dependent on β-amyloid in normal elderly

OBJECTIVE

The new criteria for preclinical Alzheimer disease (AD) proposed 3 stages: abnormal levels of β-amyloid (stage 1), stage 1 plus evidence of brain injury (stage 2), and stage 2 plus subtle cognitive changes (stage 3). However, a large group of subjects with normal β-amyloid biomarkers have evidence of brain injury; we labeled them as the "suspected non-Alzheimer pathophysiology" (sNAP) group. The characteristics of the sNAP group are poorly understood.

METHODS

Using the preclinical AD classification, 430 cognitively normal subjects from the Mayo Clinic Study of Aging who underwent brain magnetic resonance (MR), (18)fluorodeoxyglucose (FDG), and Pittsburgh compound B positron emission tomography (PET) were evaluated for FDG PET regional volumetrics, MR regional brain volumetrics, white matter hyperintensity volume, and number of infarcts. We examined cross-sectional associations across AD preclinical stages, those with all biomarkers normal, and the sNAP group.

RESULTS

The sNAP group had a lower proportion (14%) with apolipoprotein E ε4 genotype than the preclinical AD stages 2 + 3. The sNAP group did not show any group differences compared to stages 2 + 3 of the preclinical AD group on measures of FDG PET regional hypometabolism, MR regional brain volume loss, cerebrovascular imaging lesions, vascular risk factors, imaging changes associated with α-synucleinopathy, or physical findings of parkinsonism.

INTERPRETATION

Cognitively normal persons with brain injury biomarker abnormalities, with or without abnormal levels of β-amyloid, were indistinguishable on a variety of imaging markers, clinical features, and risk factors. The initial appearance of brain injury biomarkers that occurs in cognitively normal persons with preclinical AD may not depend on β-amyloidosis.

Discrimination of dementia with Lewy bodies from Alzheimer's disease using voxel-based morphometry of white matter by statistical parametric mapping 8 plus diffeomorphic anatomic registration through exponentiated Lie algebra

Introduction

The purpose of this study was to identify brain atrophy specific for dementia with Lewy bodies (DLB) and to evaluate the discriminatory performance of this specific atrophy between DLB and Alzheimer’s disease (AD).

Methods

We retrospectively reviewed 60 DLB and 30 AD patients who had undergone 3D T1-weighted MRI. We randomly divided the DLB patients into two equal groups (A and B). First, we obtained a target volume of interest (VOI) for DLB-specific atrophy using correlation analysis of the percentage rate of significant whole white matter (WM) atrophy calculated using the Voxel-based Specific Regional Analysis System for Alzheimer’s Disease (VSRAD) based on statistical parametric mapping 8 (SPM8) plus diffeomorphic anatomic registration through exponentiated Lie algebra, with segmented WM images in group A. We then evaluated the usefulness of this target VOI for discriminating the remaining 30 DLB patients in group B from the 30 AD patients. Z score values in this target VOI obtained from VSRAD were used as the determinant in receiver operating characteristic (ROC) analysis.

Results

Specific target VOIs for DLB were determined in the right-side dominant dorsal midbrain, right-side dominant dorsal pons, and bilateral cerebellum. ROC analysis revealed that the target VOI limited to the midbrain exhibited the highest area under the ROC curves of 0.75.

Conclusions

DLB patients showed specific atrophy in the midbrain, pons, and cerebellum. Midbrain atrophy demonstrated the highest power for discriminating DLB and AD. This approach may be useful for determining the contributions of DLB and AD pathologies to the dementia syndrome.