We often estimate an unknown value based on available relevant information, a process known as cognitive estimation. In this study, we assess the cognitive and neuroanatomic basis for quantitative estimation by examining deficits in patients with focal neurodegenerative disease in frontal and parietal cortex. Executive function and number knowledge are key components in cognitive estimation. Prefrontal cortex has been implicated in multilevel reasoning and planning processes, and parietal cortex has been associated with number knowledge required for such estimations. We administered the Biber cognitive estimation test (BCET) to assess cognitive estimation in 22 patients with prefrontal disease due to behavioral variant frontotemporal dementia (bvFTD), to 17 patients with parietal disease due to corticobasal syndrome (CBS) or posterior cortical atrophy (PCA) and 11 patients with mild cognitive impairment (MCI). Both bvFTD and CBS/PCA patients had significantly more difficulty with cognitive estimation than controls. MCI were not impaired on BCET relative to controls. Regression analyses related BCET performance to gray matter atrophy in right lateral prefrontal and orbital frontal cortices in bvFTD, and to atrophy in right inferior parietal cortex, right insula, and fusiform cortices in CBS/PCA. These results are consistent with the hypothesis that a frontal-parietal network plays a crucial role in cognitive estimation.
cognitive estimation; behavioral variant frontotemporal degeneration; corticobasal syndrome; posterior cortical atrophy; prefrontal cortices; parietal cortices
To examine how phenotype affects longitudinal decline on the Mini-Mental State Examination (MMSE) in patients with frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD)
The MMSE is the most commonly administered assessment for dementia severity; however, the effects of phenotype on longitudinal MMSE performance in FTLD and AD have not been extensively studied.
Data from 185 patients diagnosed with AD (n=106) and three FTLD (n=79) phenotypes (behavioral variant frontotemporal dementia [bvFTD], nonfluent agrammatic variant of primary progressive aphasia [nfaPPA], and semantic variant PPA [svPPA]) were collected for up to 52 months since initial evaluation.
Differential rates of decline were noted in that MMSE scores declined more precipitously for AD and svPPA compared to bvFTD and nfaPPA patients (p=0.001). The absolute 4-year MMSE decline given median baseline MMSE for bvFTD (14.67, 95% confidence interval [CI]: 14.63-14.71) and nfaPPA (11.02, 95% CI: 10.98-11.06) were lower than svPPA (22.32, 95% CI: 22.29-22.34) or AD (22.24, 95% CI: 22.22-22.26).
These data suggest that within-group AD and FTLD phenotypes present distinct patterns of longitudinal decline on the MMSE. MMSE may not be adequately sensitive to track disease progression in some phenotypes of FTLD.
MMSE; Alzheimer's disease; frontotemporal lobe dementia; longitudinal assessment
Patients with the semantic variant of primary progressive aphasia, also known as semantic dementia, and Alzheimer’s disease have deficits in semantic memory. However, few comparative studies have been performed to determine whether these patient groups have distinct semantic memory impairments. We asked 15 patients with semantic variant primary progressive aphasia and 57 patients with Alzheimer’s disease to judge semantic category membership of coloured photos and printed words that are members of familiar natural and manufactured categories, and we related performance to grey matter atrophy. We found that both semantic variant primary progressive aphasia and Alzheimer’s disease are significantly impaired on this task. Moreover, patients with semantic variant primary progressive aphasia had a significantly more prominent deficit for natural objects than their own deficit judging manufactured objects. Both semantic variant primary progressive aphasia and Alzheimer’s disease had atrophy that included portions of the left temporal lobe. Regression analyses related performance in semantic variant primary progressive aphasia to ventral and medial portions of the left temporal lobe, while regression analyses in Alzheimer’s disease related performance to these ventral and medial temporal areas as well as lateral temporal-parietal regions in the left hemisphere. We conclude that both semantic variant primary progressive aphasia and Alzheimer’s disease are significantly impaired in a simple category membership judgement task and the selective impairment for natural kinds in semantic variant primary progressive aphasia is related in part to disease in visual association cortex in ventral–medial portions of the left temporal lobe. We discuss factors that may contribute to the semantic memory deficit in semantic variant primary progressive aphasia.
semantic memory; Alzheimer’s disease; semantic dementia; temporal lobe; category-specific
A brief speech expression protocol that can be administered and scored without special training would aid in the differential diagnosis of the 3 principal forms of primary progressive aphasia (PPA): nonfluent/agrammatic PPA, logopenic variant PPA, and semantic variant PPA.
We used a picture-description task to elicit a short speech sample, and we evaluated impairments in speech-sound production, speech rate, lexical retrieval, and grammaticality. We compared the results with those obtained by a longer, previously validated protocol and further validated performance with multimodal imaging to assess the neuroanatomical basis of the deficits.
We found different patterns of impaired grammar in each PPA variant, and additional language production features were impaired in each: nonfluent/agrammatic PPA was characterized by speech-sound errors; logopenic variant PPA by dysfluencies (false starts and hesitations); and semantic variant PPA by poor retrieval of nouns. Strong correlations were found between this brief speech sample and a lengthier narrative speech sample. A composite measure of grammaticality and other measures of speech production were correlated with distinct regions of gray matter atrophy and reduced white matter fractional anisotropy in each PPA variant.
These findings provide evidence that large-scale networks are required for fluent, grammatical expression; that these networks can be selectively disrupted in PPA syndromes; and that quantitative analysis of a brief speech sample can reveal the corresponding distinct speech characteristics.
Patients with amyotrophic lateral sclerosis (ALS) have a motor disorder and cognitive difficulties, including difficulty with action verbs. However, the basis for the action verb impairment is unknown. Thirty-six participants with ALS and 22 with Parkinson’s disease (PD) were assessed on a simple, two-alternative forced-choice associativity judgment task, where performance was untimed and did not depend on motor functioning. We probed 120 frequency-matched action verbs, cognition verbs, concrete nouns and abstract nouns. Performance was related to T1 MRI imaging of gray matter atrophy. Patients with ALS were significantly impaired relative to healthy senior control participants only for action verbs. Patients with PD did not differ from controls for all word categories. Regression analyses related action verb performance in ALS to motor-associated cortices, but action verb judgments in PD were not related to cortical atrophy. These findings are consistent with the hypothesis that action verb difficulty in ALS is related in part to the degradation of action-related conceptual knowledge represented in motor-associated cortex.
Comprehension; Amyotrophic lateral sclerosis; Parkinson’s disease
To evaluate the interrater reliability of the new International Behavioural Variant FTD Criteria Consortium (FTDC) criteria for behavioral variant frontotemporal dementia (bvFTD).
Twenty standardized clinical case modules were developed for patients with a range of neurodegenerative diagnoses, including bvFTD, primary progressive aphasia (nonfluent, semantic, and logopenic variant), Alzheimer disease, and Lewy body dementia. Eighteen blinded raters reviewed the modules and 1) rated the presence or absence of core diagnostic features for the FTDC criteria, and 2) provided an overall diagnostic rating. Interrater reliability was determined by κ statistics for multiple raters with categorical ratings.
The mean κ value for diagnostic agreement was 0.81 for possible bvFTD and 0.82 for probable bvFTD (“almost perfect agreement”). Interrater reliability for 4 of the 6 core features had “substantial” agreement (behavioral disinhibition, perseverative/compulsive, sympathy/empathy, hyperorality; κ = 0.61–0.80), whereas 2 had “moderate” agreement (apathy/inertia, neuropsychological; κ = 0.41–0.6). Clinician years of experience did not significantly influence rater accuracy.
The FTDC criteria show promise for improving the diagnostic accuracy and reliability of clinicians and researchers. As disease-altering therapies are developed, accurate differential diagnosis between bvFTD and other neurodegenerative diseases will become increasingly important.
An increasingly varied clinical spectrum of cases with amyotrophic lateral sclerosis (ALS) has been identified, and objective criteria for clinical trial eligibility is necessary.
We sought to develop a cerebrospinal fluid (CSF) biomarker sensitive and specific for the diagnosis of ALS.
Academic medical center.
51 individuals with ALS and 23 individuals with a disorder associated with a four-repeat tauopathy (4R-tau).
MAIN OUTCOME MEASURE
CSF level of tau phosophorylated at threonine 181 (ptau), and ratio of ptau to total tau (ttau).
Using a cross-validation prediction procedure, we found significantly reduced CSF levels of ptau and ptau:ttau in ALS relative to 4R-tau and to controls. In the validation cohort, the receiver operating characteristic area under the curve for the ptau:ttau ratio was 0.916, and the comparison of ALS to 4R-tau showed sensitivity=92% and specificity=91.7%. Correct classification based on low CSF ptau:ttau was confirmed in 18 (85.7%) of 21 cases with autopsy-proven or genetically-determined disease. In patients with available measures, ptau:ttau in ALS correlated with clinical measures of disease severity such as Mini Mental State Exam (n=51) and ALS Functional Rating Scale-Revised (n=42), and regression analyses related ptau:ttau to MRI (n=10) evidence of disease in the corticospinal tract and white matter projections involving prefrontal cortex.
CONCLUSIONS AND RELEVANCE
CSF ptau:ttau may be a candidate biomarker to provide objective support for the diagnosis of ALS.
amyotrophic lateral sclerosis; cerebrospinal fluid; phosphorylated tau; biomarker
Grammatical comprehension difficulty is an essential supporting feature of the non-fluent/agrammatic variant of primary progressive aphasia (naPPA), but well-controlled clinical measures of grammatical comprehension are unavailable.
To develop a measure of grammatical comprehension and examine this comparatively in PPA variants and behavioural-variant frontotemporal degeneration (bvFTD) and to assess the neuroanatomic basis for these deficits with volumetric grey matter atrophy and whole-brain fractional anisotropy (FA) in white matter tracts.
Academic medical centre.
39 patients with variants of PPA (naPPA=12, lvPPA=15 and svPPA=12), 27 bvFTD patients without aphasia and 12 healthy controls.
Main outcome measure
Grammatical comprehension accuracy.
Patients with naPPA had selective difficulty understanding cleft sentence structures, while all PPA variants and patients with bvFTD were impaired with sentences containing a centre-embedded subordinate clause. Patients with bvFTD were also impaired understanding sentences involving short-term memory. Linear regressions related grammatical comprehension difficulty in naPPA to left anterior-superior temporal atrophy and reduced FA in corpus callosum and inferior frontal-occipital fasciculus. Difficulty with centre-embedded sentences in other PPA variants was related to other brain regions.
Conclusions and relevance
These findings emphasise a distinct grammatical comprehension deficit in naPPA and associate this with interruption of a frontal-temporal neural network.
This study establishes that sparse canonical correlation analysis (SCCAN) identifies generalizable, structural MRI-derived cortical networks that relate to five distinct categories of cognition. We obtain multivariate psychometrics from the domain-specific sub-scales of the Philadelphia Brief Assessment of Cognition (PBAC). By using a training and separate testing stage, we find that PBAC-defined cognitive domains of language, visuospatial functioning, episodic memory, executive control, and social functioning correlate with unique and distributed areas of gray matter (GM). In contrast, a parallel univariate framework fails to identify, from the training data, regions that are also significant in the left-out test dataset. The cohort includes164 patients with Alzheimer’s disease, behavioral-variant frontotemporal dementia, semantic variant primary progressive aphasia, nonfluent/agrammatic primary progressive aphasia, or corticobasal syndrome. The analysis is implemented with open-source software for which we provide examples in the text. In conclusion, we show that multivariate techniques identify biologically-plausible brain regions supporting specific cognitive domains. The findings are identified in training data and confirmed in test data.
Alzheimer disease; Frontotemporal lobar degeneration; Philadelphia Brief Assessment of Cognition; PBAC; MRI; Sparse canonical correlation analysis
Significant heterogeneity in clinical features of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) cases with the pathogenic C9orf72 expansion (C9P) have been described. To clarify this issue, we compared a large C9P cohort with carefully matched non-expansion (C9N) cases with a known or highly-suspected underlying TDP-43 proteinopathy.
A retrospective-cohort study using available cross-sectional and longitudinal clinical and neuropsychological data, MRI voxel-based morphometry (VBM) and neuropathological assessment from 64 C9P cases (ALS=31, FTLD=33) and 79 C9N cases (ALS=36, FTLD=43).
C9P cases had an earlier age of onset (p=0.047), and in the subset of deceased patients, an earlier age of death (p=0.014) than C9N. C9P had more rapid progression than C9N: C9P ALS cases had a shortened survival (2.6±0.3 years) compared to C9N ALS (3.8±0.4 years; log-rankλ2=4.183,p=0.041), and C9P FTLD showed a significantly greater annualized rate of decline in letter fluency (4.5±1.3words/year) than C9N FTLD (1.4±0.8words/year, p=0.023). VBM revealed greater atrophy in the right fronto-insular, thalamus, cerebellum and bilateral parietal regions for C9P FTLD relative to C9N FTLD, and regression analysis related verbal fluency scores to atrophy in frontal and parietal regions. Neuropathologic analysis found greater neuronal loss in the mid-frontal cortex in C9P FTLD, and mid-frontal cortex TDP-43 inclusion severity correlated with poor letter fluency performance.
C9P cases may have a shorter survival in ALS and more rapid rate of cognitive decline related to frontal and parietal disease in FTLD. C9orf72 genotyping may provide useful prognostic and diagnostic clinical information for ALS and FTLD patients.
Frontotemporal dementia; Amyotrophic lateral sclerosis; C9orf72; neuropsychological tests; neuroimaging
Frontotemporal lobar degeneration (FTLD) can manifest as a spectrum of clinical syndromes, ranging from behavioural impairment to language or motor dysfunction. Recently, revised diagnostic criteria have been proposed for the behavioural and progressive aphasia syndromes associated with frontotemporal degeneration. The present review will summarize these diagnostic guidelines and highlight some lingering controversies in the classification of FTLD clinical syndromes. We will discuss common tools and methods used to identify the insidious changes of behavioural variant frontotemporal dementia (bvFTD), the value of new, patient-based tasks of orbitofrontal function, and the issue of a benign or ‘phenocopy’ variant of bvFTD. With regard to primary progressive aphasia (PPA), we will discuss the scope of the semantic disorder in semantic-variant PPA, the nature of the speech disorder in non-fluent, agrammatic PPA, and the preliminary utility of a logopenic PPA classification.
When making a decision, humans often have to ‘coordinate’—reach the same conclusion—as another individual without explicitly communicating. Relatively, little is known about the neural basis for coordination. Moreover, previous fMRI investigations have supported conflicting hypotheses. One account proposes that individuals coordinate using a ‘gut feeling’ and that this is supported by insula recruitment. Another account proposes that individuals recruit strategic decision-making mechanisms in prefrontal cortex in order to coordinate. We investigate the neural basis for coordination in individuals with behavioral-variant frontotemporal dementia (bvFTD) who have limitations in social decision-making associated with disease in prefrontal cortex. We demonstrate that bvFTD are impaired at establishing a focal point in a semantic task (e.g. ‘Tell me any boy's name’) that requires coordination relative to a similar, control semantic task that does not. Additionally, coordination limitations in bvFTD are related to cortical thinning in prefrontal cortex. These findings are consistent with behavioral economic models proposing that, beyond a ‘gut feeling’, strategic decision-making contributes to the coordination process, including a probabilistic mechanism that evaluates the salience of a response (e.g. is ‘John’ a frequent boy's name), a hierarchical mechanism that iteratively models an opponent's likely response and a mechanism involved in social perspective taking.
coordination; frontotemporal dementia; MRI; decision making; game theory
Frontotemporal lobar degeneration with motor neuron disease (FTLD-MND) is characterized by neuronal cytoplasmic inclusions containing TDP-43. Apolipoprotein E4 (apoE4), derived from the apoE ε4 allele, enhances brain atrophy in FTLD through unknown mechanisms. Here, we studied two siblings with C9ORF72-linked familial FTLD-MND, an apoE ε4 homozygote and an apoE ε3 homozygote. The apoE ε4 homozygote had more cognitive-behavioral symptoms, fronto-insulo-temporal atrophy, and apoE fragments and aggregates in the anterior cingulate cortex. ApoE formed complexes with TDP-43 that were more abundant in the apoE ε4 homozygote. Although differences seen in a sibling pair could arise due to chance, these findings raise the possibility that apoE4 exacerbates brain pathology in FTLD through formation of neurotoxic apoE fragments and interactions with TDP-43.
Apolipoprotein E; TDP-43; Frontotemporal dementia; Motor neuron disease; Neuropathology
Previous work investigating deficits in self-appraisal in behavioural-variant frontotemporal degeneration (bvFTD) has focused on a single domain: social/behavioural processes. We examined whether a domain-specific versus multi-domain model best explains degraded self-appraisal in bvFTD.
49 patients with bvFTD and 73 patients with Alzheimer’s disease (AD) were administered quantitative assessments of episodic memory, naming and grammatical comprehension. Self-appraisal of cognitive test performance was assessed by asking patients to rate their performance immediately after completing each neuropsychological test. A discrepancy score was created to reflect the difference between patient performance on neuropsychological tests and self-appraisal of their test performance. Self-appraisal for each neuropsychological measure was related to grey matter (GM) density in each group using voxel-based morphometry.
bvFTD patients were poor at evaluating their own performance on all cognitive tests, with no significant correlations between self-appraisal and actual performance. By contrast, poor self-appraisal in AD was restricted to episodic memory performance. Poor self-appraisal on each task in bvFTD and AD was related to reduced GM density in several ventral and rostral medial prefrontal regions. Crucially, poor self-appraisal for all domains in bvFTD was related to a specific area of reduced GM density in the subgenual cingulate (BA 25).
Poor self-appraisal in bvFTD affects multiple domains, and this multi-domain impairment pattern is associated with frontal disease in the subgenual cingulate.
Based on the recent literature and collective experience, an international consortium developed revised guidelines for the diagnosis of behavioural variant frontotemporal dementia. The validation process retrospectively reviewed clinical records and compared the sensitivity of proposed and earlier criteria in a multi-site sample of patients with pathologically verified frontotemporal lobar degeneration. According to the revised criteria, ‘possible’ behavioural variant frontotemporal dementia requires three of six clinically discriminating features (disinhibition, apathy/inertia, loss of sympathy/empathy, perseverative/compulsive behaviours, hyperorality and dysexecutive neuropsychological profile). ‘Probable’ behavioural variant frontotemporal dementia adds functional disability and characteristic neuroimaging, while behavioural variant frontotemporal dementia ‘with definite frontotemporal lobar degeneration’ requires histopathological confirmation or a pathogenic mutation. Sixteen brain banks contributed cases meeting histopathological criteria for frontotemporal lobar degeneration and a clinical diagnosis of behavioural variant frontotemporal dementia, Alzheimer’s disease, dementia with Lewy bodies or vascular dementia at presentation. Cases with predominant primary progressive aphasia or extra-pyramidal syndromes were excluded. In these autopsy-confirmed cases, an experienced neurologist or psychiatrist ascertained clinical features necessary for making a diagnosis according to previous and proposed criteria at presentation. Of 137 cases where features were available for both proposed and previously established criteria, 118 (86%) met ‘possible’ criteria, and 104 (76%) met criteria for ‘probable’ behavioural variant frontotemporal dementia. In contrast, 72 cases (53%) met previously established criteria for the syndrome (P < 0.001 for comparison with ‘possible’ and ‘probable’ criteria). Patients who failed to meet revised criteria were significantly older and most had atypical presentations with marked memory impairment. In conclusion, the revised criteria for behavioural variant frontotemporal dementia improve diagnostic accuracy compared with previously established criteria in a sample with known frontotemporal lobar degeneration. Greater sensitivity of the proposed criteria may reflect the optimized diagnostic features, less restrictive exclusion features and a flexible structure that accommodates different initial clinical presentations. Future studies will be needed to establish the reliability and specificity of these revised diagnostic guidelines.
behavioural variant frontotemporal dementia; diagnostic criteria; frontotemporal lobar degeneration; FTD; pathology
The Philadelphia Brief Assessment of the Cognition (PBAC) is a brief dementia-screening instrument. The PBAC assesses five cognitive domains: working memory/executive control; lexical retrieval/language; visuospatial/visuoconstructional operations; verbal/visual episodic memory; and behavior/social comportment. A revised version of the PBAC was administered to 198 participants including patients with Alzheimer’s disease (AD) (n=46) and four groups of patients with frontotemporal dementia (FTD) syndromes: behavioral-variant FTD (bvFTD; n=65), semantic-variant primary progressive aphasia (PPA) (svPPA; n=22), non-fluent/agrammatic-variant PPA (nfaPPA; n=23), and corticobasal syndrome (CBS; n=42), and a group of normal controls (n=15). The total PBAC score was highly correlated with the MMSE. The criterion validity of the PBAC was assessed relative to standard neuropsychological test performance. Using standard neuropsychological test performance as a criterion, the total PBAC score accurately identified the presence and severity of dementia. Intra-class correlations between PBAC subscales and standard neuropsychological tests were highly significant. PBAC subscales demonstrated good clinical utility in distinguishing AD and FTD subtypes using receiver operating characteristic analysis and standard diagnostic performance statistics to determine optimal subscale cut scores. The PBAC is a valid tool and able to assesses differential patterns neuropsychological/behavioral impairment in a broad range of neurodegenerative conditions.
Alzheimer’s disease; Frontotemporal lobar dementia; Frontotemporal dementia; FTD; Philadelphia Brief Assessment of the Cognition; PBAC; Neuropsychological assessment; Philadelphia (repeatable) Verbal Learning Test
This multidisciplinary article compares the pattern of memory loss described in Gabriel García Márquez's One Hundred Years of Solitude to that exhibited by patients with semantic dementia (SD). In his renowned novel, García Márquez depicts the plight of Macondo, a town struck by the dreaded insomnia plague. The most devastating symptom of the plague is not the impossibility of sleep, but rather the loss of ‘the name and notion of things’. In an effort to combat this insidious loss of knowledge, the protagonist, José Arcadio Buendía, ‘marked everything with its name: table, chair, clock, door, wall, bed, pan’. ‘Studying the infinite possibilities of a loss of memory, he realized that the day might come when things would be recognized by their inscriptions but that no one would remember their use’. The cognitive impairments experienced by Macondo's inhabitants are remarkably similar to those observed in SD, a clinical syndrome characterized by a progressive breakdown of conceptual knowledge (semantic memory) in the context of relatively preserved day-to-day (episodic) memory. First recognized in 1975, it is now considered one of the main variants of frontotemporal lobar degeneration. Writing within the realm of magical realism and investigating the power of language as a form of communication, García Márquez provides beautiful descriptions of the loss of ‘the name and notion of things’ typical of the syndrome. He further speculates on ways to cope with this dissolution of meaning, ranging from ‘the spell of an imaginary reality’ to José Arcadio's ‘memory machine’, strategies that resonate with attempts by semantic dementia patients to cope with their disease. Remarkably, García Márquez created a striking literary depiction of collective semantic dementia before the syndrome was recognized in neurology. The novel also provides an inspiring and human account of one town's fight against ‘the quicksand of forgetfulness’.
semantic dementia; Gabriel García Márquez; One Hundred Years of Solitude; magical realism; neurology and literature
Neuropsychological studies have shown that patients with Frontotemporal dementia (FTD) perform worse than patients with Alzheimer’s disease (AD) on tests of conceptualization and verbal fluency, but better on tests of memory and visuospatial functions. However, it is not known if these distinct cognitive profiles are robust enough to be detected using a relatively brief dementia screening instrument such as the Mattis Dementia Rating Scale (MDRS). To address this issue, the MDRS subscale profiles of patients with autopsy-confirmed FTD (n = 17) or AD (n = 34) were compared. Results showed distinct cognitive profiles in which FTD patients performed worse than AD patients on the Initiation/Perseveration and Conceptualization subscales while performing better on the Memory and Construction subscales. The distinct subscale profiles correctly classified 85% of AD patients and 76% of FTD patients. Profiles were maintained in a subset of mildly-to-moderately demented patients (MDRS ≥ 105) and correctly classified 89% of these patients. In addition, FTD patients (mean = 30.0 points/year) declined faster than AD patients (mean = 14.8 points/year) on MDRS total and specific subscale scores. These results suggest that the MDRS may be a useful adjunct to other clinical measures for distinguishing FTD from AD and tracking the progression of the disorder.
Frontotemporal dementia; Alzheimer’s disease; Mattis Dementia Rating Scale; Rate of progression; Cognitive profile; Functional impairment
Behavioral variant frontotemporal dementia (bvFTD) strikes hardest at the frontal lobes, but the sites of earliest injury remain unclear.
To determine atrophy patterns in distinct clinical stages of bvFTD, testing the hypothesis that the mildest stage is restricted to frontal paralimbic cortex.
A bvFTD cohort study.
University hospital dementia clinic.
Patients with bvFTD with Clinical Dementia Rating (CDR) scale scores of 0.5 (n=15), 1 (n=15), or 2 to 3 (n=15) age and sex matched to each other and to 45 healthy controls.
Main Outcome Measures:
Magnetic resonance voxel-based morphometry estimated gray matter and white matter atrophy at each disease stage compared with controls.
Patients with a CDR score of 0.5 had gray matter loss in frontal paralimbic cortices, but atrophy also involved a network of anterior cortical and subcortical regions. A CDR score of 1 showed more extensive frontal gray matter atrophy and white matter losses in corpus callosum and brainstem. A CDR score of 2 to 3 showed additional posterior insula, hippocampus, and parietal involvement, with white matter atrophy in presumed frontal projection fibers.
Very mild bvFTD targets a specific subset of frontal and insular regions. More advanced disease affects white matter and posterior gray matter structures densely interconnected with the sites of earliest injury.