Alzheimer's disease (AD) can present with non-amnestic clinical syndromes. We investigated whether there is an imaging signature of AD pathology in these atypical subjects. We identified 14 subjects that had pathological AD, a non-amnestic presentation (i.e. atypical AD), and MRI. These subjects were matched to 14 with clinical and pathological AD (i.e. typical AD), 14 with the same non-amnestic presentations with frontotemporal lobar degeneration (FTLD) pathology, and 20 controls. Voxel-based morphometry and region-of-interest (ROI) analysis were used to assess patterns of grey matter loss. Loss was observed in the temporoparietal cortex in both typical and atypical AD, and showed significantly greater loss than FTLD. However, the medial temporal lobes were more severely affected in typical AD and FTLD compared to atypical AD. A ratio of hippocampal and temporoparietal volumes provided excellent discrimination of atypical AD from FTLD subjects. Temporoparietal atrophy may therefore provide a useful marker of the presence of AD pathology even in subjects with atypical clinical presentations, especially in the context of relative sparing of the hippocampus.
Alzheimer's disease; pathology; voxel-based morphometry; atypical presentation; frontotemporal lobar degeneration; temporoparietal cortex; hippocampus
Lewy pathology occurs in 8–17% of neurologically-normal people >age 60, termed incidental Lewy body disease, (iLBD). It is often assumed to represent preclinical Parkinson disease (PD). However, some iLBD cases have diffuse pathology inconsistent with preclinical PD. We analyzed iLBD cases (α-synuclein immunohistochemistry) using the Braak PD staging scheme and determined if some had a neuropathological pattern suggestive of preclinical Dementia with Lewy bodies (DLB). Of the 235 brains examined, 34 had iLBD (14.5%) and all but one could be assigned a Braak PD stage. The distribution of α-synuclein pathology in the 33 cases fell into three patterns: (1) Diffuse cortical and subcortical α-synuclein pathology; (2) No cortical a-synuclein pathology, but a caudal-to-rostral ascending pattern, primarily involving brainstem; (3) Intermediate between these two categories. Also, 6/33 cases failed to follow the pattern of contiguous spread proposed by Braak. These findings suggest dichotomy in the distribution of iLBD: some cases fit the Braak ascending scheme, conceptually consistent with preclinical PD, whereas others displayed prominent cortical involvement that might represent preclinical DLB.
incidental Lewy body disease; parkinson disease; dementia with Lewy bodies
In the past 10 years, there has been a virtual explosion in the literature concerning the construct of mild cognitive impairment. The interest in this topic demonstrates the increasing emphasis on the identification of the earliest features of cognitive disorders such as Alzheimer’s disease and other dementias. Mild cognitive impairment represents the earliest clinical features of these conditions and, hence, has become a focus of clinical, epidemiological, neuroimaging, biomarker, neuropathological, disease mechanism and clinical trials research. This review summarizes the progress that has been made while also recognizing the challenges that remain.
Mild cognitive impairment; Alzheimer’s disease; Imaging; Cognitive decline
Defining the nature of the contribution of stroke to cognitive impairment remains challenging.
We randomly selected Olmsted County, MN residents aged 70–89 years on October 1, 2004 and invited eligible non-demented subjects to participate. Participants (n = 2,050) were evaluated with an informant interview, a neurological evaluation, and neuropsychological testing. Neuropsychological testing included 9 tests to assess memory, attention and executive function, visuospatial cognition and language. Subjects were diagnosed by consensus as cognitively normal, MCI (either amnestic (a-) or non-amnestic (na-)), or dementia. A history of stroke was obtained from the subject and confirmed in the medical record. We computed the odds ratios (OR) for a clinical diagnosis of MCI or for scoring in the lowest quartile on each cognitive domain.
There were 1640 cognitively normal and 329 MCI subjects, 241 a-MCI and 88 na-MCI. In fully adjusted models with non-demented subjects only, a history of stroke was associated with a higher odds ratio (OR) of na-MCI (OR= 2.85, 95% CI 1.61 – 5.04) than a-MCI (OR= 1.77, 95% CI 1.14 – 2.74). A history of stroke was also associated with impaired function in each cognitive domain except memory. The association was strongest for attention and executive function (OR=2.48, 95% CI 1.73 – 3.53). APOE e4 genotype was associated only with a-MCI and with impaired memory function.
In this population-based sample of non-demented persons, a history of stroke was particularly associated with na-MCI and with impairment in non-memory cognition. APOE e4 genotype was associated with memory impairment and a-MCI.
There are little data on the relationship between Lewy body disease and mild cognitive impairment syndromes. The Mayo Clinic aging and dementia databases in Rochester, Minnesota, and Jacksonville, Florida were queried for cases who were diagnosed with mild cognitive impairment between 1 January 1996 and 30 April 2008, were prospectively followed and were subsequently found to have autopsy-proven Lewy body disease. The presence of rapid eye movement sleep behaviour disorder was specifically assessed. Mild cognitive impairment subtypes were determined by clinical impression and neuropsychological profiles, based on prospective operational criteria. The diagnosis of clinically probable dementia with Lewy bodies was based on the 2005 McKeith criteria. Hippocampal volumes, rate of hippocampal atrophy, and proton magnetic resonance spectroscopy were assessed on available magnetic resonance imaging and spectroscopy scans. Eight subjects were identified; six were male. Seven developed dementia with Lewy bodies prior to death; one died characterized as mild cognitive impairment. The number of cases and median age of onset (range) for specific features were: seven with rapid eye movement sleep behaviour disorder—60 years (27–91 years), eight with cognitive symptoms—69 years (62–89 years), eight with mild cognitive impairment—70.5 years (66–91 years), eight with parkinsonism symptoms—71 years (66–92 years), six with visual hallucinations—72 years (64–90 years), seven with dementia—75 years (67–92 years), six with fluctuations in cognition and/or arousal—76 years (68–92 years) and eight dead—76 years (71–94 years). Rapid eye movement sleep behaviour disorder preceded cognitive symptom onset in six cases by a median of 10 years (2–47 years) and mild cognitive impairment diagnosis by a median of 12 years (3–48 years). The mild cognitive impairment subtypes represented include: two with single domain non-amnestic mild cognitive impairment, three with multi-domain non-amnestic mild cognitive impairment, and three with multi-domain amnestic mild cognitive impairment. The cognitive domains most frequently affected were attention and executive functioning, and visuospatial functioning. Hippocampal volumes and the rate of hippocampal atrophy were, on average, within the normal range in the three cases who underwent magnetic resonance imaging, and the choline/creatine ratio was elevated in the two cases who underwent proton magnetic resonance spectroscopy when they were diagnosed as mild cognitive impairment. On autopsy, six had neocortical-predominant Lewy body disease and two had limbic-predominant Lewy body disease; only one had coexisting high-likelihood Alzheimer's disease. These findings indicate that among Lewy body disease cases that pass through a mild cognitive impairment stage, any cognitive pattern or mild cognitive subtype is possible, with the attention/executive and visuospatial domains most frequently impaired. Hippocampal volume and proton magnetic resonance spectroscopy data were consistent with recent data in dementia with Lewy bodies. All cases with rapid eye movement sleep behaviour disorder and mild cognitive impairment were eventually shown to have autopsy-proven Lewy body disease, indicating that rapid eye movement sleep behaviour disorder plus mild cognitive impairment probably reflects brainstem and cerebral Lewy body disease.
mild cognitive impairment; dementia; dementia with Lewy bodies; Lewy body disease; neuropathology
The behavioural variant of frontotemporal dementia is a progressive neurodegenerative syndrome characterized by changes in personality and behaviour. It is typically associated with frontal lobe atrophy, although patterns of atrophy are heterogeneous. The objective of this study was to examine case-by-case variability in patterns of grey matter atrophy in subjects with the behavioural variant of frontotemporal dementia and to investigate whether behavioural variant of frontotemporal dementia can be divided into distinct anatomical subtypes. Sixty-six subjects that fulfilled clinical criteria for a diagnosis of the behavioural variant of frontotemporal dementia with a volumetric magnetic resonance imaging scan were identified. Grey matter volumes were obtained for 26 regions of interest, covering frontal, temporal and parietal lobes, striatum, insula and supplemental motor area, using the automated anatomical labelling atlas. Regional volumes were divided by total grey matter volume. A hierarchical agglomerative cluster analysis using Ward's clustering linkage method was performed to cluster the behavioural variant of frontotemporal dementia subjects into different anatomical clusters. Voxel-based morphometry was used to assess patterns of grey matter loss in each identified cluster of subjects compared to an age and gender-matched control group at P < 0.05 (family-wise error corrected). We identified four potentially useful clusters with distinct patterns of grey matter loss, which we posit represent anatomical subtypes of the behavioural variant of frontotemporal dementia. Two of these subtypes were associated with temporal lobe volume loss, with one subtype showing loss restricted to temporal lobe regions (temporal-dominant subtype) and the other showing grey matter loss in the temporal lobes as well as frontal and parietal lobes (temporofrontoparietal subtype). Another two subtypes were characterized by a large amount of frontal lobe volume loss, with one subtype showing grey matter loss in the frontal lobes as well as loss of the temporal lobes (frontotemporal subtype) and the other subtype showing loss relatively restricted to the frontal lobes (frontal-dominant subtype). These four subtypes differed on clinical measures of executive function, episodic memory and confrontation naming. There were also associations between the four subtypes and genetic or pathological diagnoses which were obtained in 48% of the cohort. The clusters did not differ in behavioural severity as measured by the Neuropsychiatric Inventory; supporting the original classification of the behavioural variant of frontotemporal dementia in these subjects. Our findings suggest behavioural variant of frontotemporal dementia can therefore be subdivided into four different anatomical subtypes.
behavioural variant frontotemporal dementia; atrophy; cluster analysis; voxel-based morphometry
Corticobasal degeneration (CBD) is a neurodegenerative disease characterized pathologically by neuronal loss, gliosis and tau deposition in neocortex, basal ganglia and brainstem. Typical clinical presentation is known as corticobasal syndrome (CBS) and involves the core features of progressive asymmetric rigidity and apraxia, accompanied by other signs of cortical and extrapyramidal dysfunction. Asymmetry is also emphasized on neuroimaging.
To describe a series of cases of CBD with symmetric clinical features and to compare clinical and imaging features of these symmetric CBD cases (S-CBD) to typical cases of CBS with CBD pathology.
All cases of pathologically confirmed CBD from the Mayo Clinic Rochester database were identified. Clinical records were reviewed and quantitative volumetric analysis of symmetric atrophy on head MRI using atlas based parcellation was performed. Subjects were classified as S-CBD if no differences had been observed between right- and left-sided cortical or extrapyramidal signs or symptoms. S-CBD cases were compared to 10 randomly selected typical CBS cases.
Five cases (2 female) met criteria for S-CBD. None had limb dystonia, myoclonus, apraxia or alien limb phenomena. S-CBD cases had significantly less asymmetric atrophy when compared with CBS cases (p=0.009); they were also younger at onset (median 61 versus 66 years, p<0.05) and death (67 versus 73 years, p<0.05). Family history was present in 40% of S-CBD cases.
CBD can have a symmetric presentation, clinically and radiologically, in which typical features of CBS, such as limb apraxia, myoclonus, dystonia and alien limb phenomenon, may be absent.
Corticobasal degeneration; Corticobasal syndrome; Symmetric CBD; Atlas Based Parcellation; Pathology
The rarity of young-onset dementia (YOD), the broad differential diagnosis and unusual clinical presentations present unique challenges to correctly recognize the condition and establish an accurate diagnosis. Limited data exist regarding clinical features associated with dementia prior to the age of 45.
We retrospectively assessed cognitive and noncognitive neurological characteristics of 235 patients who presented for evaluation of YOD to investigate the clinical characteristics of YOD compared to later-onset dementias and to identify clinical features associated with specific etiologies that may aid in the evaluation of YOD.
Multiple cognitive domains were affected in most patients, and no significant differences in affected domains existed between groups. Early psychiatric and behavioral features occurred at very high frequencies. Nearly 80% of this YOD cohort had additional noncognitive symptoms or signs as a feature of their disease. Chorea was strongly associated with Huntington disease. Parkinsonism was not seen in patients having an autoimmune/inflammatory etiology.
The rarity of YOD and the high frequency of early psychiatric features led to frequent misdiagnosis early in the clinical course. The high frequency of noncognitive symptoms and signs may aid clinicians in distinguishing patients requiring a more extensive evaluation for YOD.
Young-onset dementia; Cognitive decline, age of onset; Presenile dementia, clinical features
The purpose of this study was to compare the diagnostic accuracy of glucose metabolism and amyloid deposition as demonstrated by 18F-FDG and Pittsburg Compound B (PiB) PET to evaluate subjects with cognitive impairment.
Subjects were selected from existing participants in the Mayo Alzheimer’s Disease Research Center or Alzheimer’s Disease Patient Registry programs. A total of 20 healthy controls and 17 amnestic mild cognitive impairment (aMCI), 6 nonamnestic mild cognitive impairment (naMCI), and 13 Alzheimer disease (AD) subjects were imaged with both PiB and 18F-FDG PET between March 2006 and August 2007. Global measures for PiB and 18F-FDG PET uptake, normalized to cerebellum for PiB and pons for 18F-FDG, were compared. Partial-volume correction, standardized uptake value (SUV), and cortical ratio methods of image analysis were also evaluated in an attempt to optimize the analysis for each test.
Significant discrimination (P < 0.05) between controls and AD, naMCI and aMCI, naMCI and AD, and aMCI and AD by PiB PET measurements was observed. The paired groupwise comparisons of the global measures demonstrated that PiB PET versus 18F-FDG PET showed similar significant group separation, with only PiB showing significant separation of naMCI and aMCI subjects.
PiB PET and 18F-FDG PET have similar diagnostic accuracy in early cognitive impairment. However, significantly better group discrimination in naMCI and aMCI subjects by PiB, compared with 18F-FDG, was seen and may suggest early amyloid deposition before cerebral metabolic disruption in this group.
PET; dementia; 18F-FDG; PiB
Frontotemporal dementia and amyotrophic lateral sclerosis are neurodegenerative diseases associated with TAR DNA-binding protein 43– and ubiquitin-immunoreactive pathologic lesions.
To determine whether survival is influenced by symptom of onset in patients with frontotemporal dementia and amyotrophic lateral sclerosis.
Design, Setting, and Patients
Retrospective review of patients with both cognitive impairment and motor neuron disease consecutively evaluated at 4 academic medical centers in 2 countries.
Main Outcome Measures
Clinical phenotypes and survival patterns of patients.
A total of 87 patients were identified, including 60 who developed cognitive symptoms first, 19 who developed motor symptoms first, and 8 who had simultaneous onset of cognitive and motor symptoms. Among the 59 deceased patients, we identified 2 distinct subgroups of patients according to survival. Long-term survivors had cognitive onset and delayed emergence of motor symptoms after a long monosymptomatic phase and had significantly longer survival than the typical survivors (mean, 67.5 months vs 28.2 months, respectively; P<.001). Typical survivors can have simultaneous or discrete onset of cognitive and motor symptoms, and the simultaneous-onset patients had shorter survival (mean, 19.2 months) than those with distinct cognitive or motor onset (mean, 28.6 months) (P=.005).
Distinct patterns of survival profiles exist in patients with frontotemporal dementia and motor neuron disease, and overall survival may depend on the relative timing of the emergence of secondary symptoms.
To explore whether associations of potential risk factors for incidental Lewy Body Disease (iLBD) may be similar to Parkinson Disease (PD).
Design, Setting, and Patients
We identified brain-autopsied residents of Olmsted County, MN and immediate vicinity(1988–2004), age>60, without evidence of neurodegenerative disease or tremor, and evaluated by at least one physician within one year of death. Analysis for “incidental” Lewy pathology was done blinded to clinical abstraction.
Main Outcome Measures
Whether risk factors previously associated with PD in Olmsted County, MN are also associated with iLBD.
Of 235 subjects, 34 had iLBD(14.5%). The overall risk factor profiles for iLBD and PD were fairly similar between the two sets of OR estimates, with 11/16 ORs in the same direction. Prior Olmsted County studies documented 7 risk factors with statistically significant associations with PD; for two of these, the ORs for iLBD were in the same direction and statistically significant (physician, caffeine), whereas for three, they were in the same direction but not significant (education, head injury, number-of-children); they were in the opposite direction but not statistically significant for 2 (depression, anxiety). ILBD was not associated with various end-of-life conditions or causes-of-death, although they were slightly older and more likely cachectic.
Based on this exploratory study, iLBD and PD appear to have similar risk factor profiles. Thus, at least some cases of ILBD might represent preclinical PD, arrested PD or a partial syndrome due to a lesser burden of causative factors. ILBD is not explained by non-specific end-of-life brain insults.
To characterize a cohort of individuals who have experienced rapidly progressive dementia with onset prior to age 45.
Very little data regarding the clinical features or clinical spectrum of rapidly progressive young-onset dementia (RP-YOD) is available, primarily consisting of case reports or small series.
A search of the Mayo Clinic medical record was employed to identify patients who had onset prior to age 45 of rapidly progressive dementia. All available medical records, laboratory data, neuroimaging studies, and pathological data were reviewed.
Twenty-two patients met the pre-defined inclusion and exclusion criteria. Behavioral and affective disorders, cerebellar dysfunction and visual and/or oculomotor dysfunction were common early clinical features within the cohort, as were clinical features often associated with Creutzfeldt-Jakob disease (CJD). Diagnostic testing identified an etiology in most patients.
Presentations of RP-YOD result from a variety of etiologies and significant overlap in clinical features is observed. Clinical features often associated with CJD appear to be common within the entire cohort of RP-YOD patients. Diagnostic studies aided in establishing a diagnosis in most patients, however five had uncertain diagnoses despite exhaustive evaluation.
rapidly progressive dementia; young-onset dementia; presenile dementia; Creutzfeldt-Jakob disease; young-onset
Neurodegenerative dementias are typically characterized by an insidious onset and a relatively slowly progressive course. Less common are patients with a rapidly progressive course to death.
To characterize patients with a neurodegenerative disease and a rapidly progressive course to death.
Tertiary Care Medical Center.
Using a text word search for “rapid” and “dementia” in the same sentence, the Mayo Clinic Medical Records Linkage system was used to identify all patients evaluated between 1/1/00−9/30/07 with brain autopsy (N=96). Of these 96, we included only those with disease duration of <4 years to death and with histological diagnosis of a neurodegenerative disease.
We identified 22 cases (10 males). Although 36% were Creutzfeldt-Jakob disease (CJD), the rest included frontotemporal lobar degenerative with motor neuron degeneration (FTLD-MND; 23%); a tauopathy (progressive supranuclear palsy or corticobasal degeneration; 18%); diffuse Lewy body disease (DLBD; 14%) or Alzheimer's disease 9%. All CJD cases died ≤12 months after onset while the others had illness duration of >12 months. Notably, all three DLBD patients, but no others, initially experienced a transient postoperative- or illness-associated encephalopathy, then relative normality for two years, before a rapidly progressive dementia and decline to death in 4−12 months.
Based on this cohort, although CJD is the most likely cause of a rapidly progressive neurodegenerative dementia, FTLD-MND, DLBD, tauopathies and Alzheimer's disease can also cause a rapidly progressive dementia. If illness duration is beyond 12-months, a non-CJD neurodegenerative disease may be more likely the diagnosis, than CJD.
Frontotemporal lobar degeneration (FTLD) can be classified based on the presence of the microtubule associated protein tau and the TAR DNA binding protein-43 (TDP-43). Future treatments will likely target these proteins; therefore it is important to identify biomarkers to help predict protein biochemistry.
To determine whether there is an MRI signature pattern of tau or TDP-43 using a large cohort of FTLD subjects and to investigate how patterns of atrophy change according to disease severity using a large autopsy-confirmed cohort of FTLD subjects.
Patterns of grey matter loss were assessed using voxel-based morphometry in 37 tau-positive and 44 TDP-43 positive subjects compared to 35 age and gender-matched controls, and compared to each other. Comparisons were also repeated in behavioral variant frontotemporal dementia (bvFTD) subjects (n=15 tau-positive and n=30 TDP-43 positive). Patterns of atrophy were also assessed according to performance on the clinical dementia rating (CDR) scale and mini-mental state examination (MMSE).
The tau-positive and TDP-43 positive groups showed patterns of frontotemporal grey matter loss compared to controls with no differences observed between the groups, for all subjects and for bvFTD subjects. Patterns of grey matter loss increased in a graded manner by CDR and MMSE with loss in the frontal lobes, insula and hippocampus in mild subjects, spreading to the temporal and parietal cortices and striatum in more advanced disease.
There is no signature pattern of atrophy for tau or TDP-43; however patterns of atrophy in FTLD progress with measures of clinical disease severity.
frontotemporal lobar degeneration; autopsy; tau; TAR DNA binding protein-43; voxel-based morphometry; Clinical Dementia Rating Scale; Mini-Mental State Examination
Although it is established that the apolipoprotein E (APOE) e4 allele increases the risk of Alzheimer’s disease (AD), epidemiological studies indicate that genetic risk decreases late in life. This raises the question of whether the effects of APOE on cognition which are seen in midlife arise from a cognitive phenotype of APOE or from the presence of early AD in some APOE-e4 carriers. We addressed this question by comparing the cognitive consequences of variation in the APOE gene between individuals over the age of 80 (old-old) and middle-aged and young-old individuals. A spatially cued discrimination paradigm – previously shown to be sensitive to AD and to APOE genotype – required a speeded categorization of a target letter following cues that were valid, invalid, or neutral in predicting target location. Results revealed greater costs of invalid cues in the APOE-e4 carriers of middle-aged and young-old, but not old-old, groups. The dissipation of the APOE effect in old-old individuals at lower risk of AD suggests that visuospatial attention impairments seen as early as midlife in APOE-e4 carriers may be a preclinical marker of AD.
attention; APOE; phenotype; old-old
The purpose of this study was to use serial imaging to gain insight into the sequence of pathologic events in Alzheimer's disease, and the clinical features associated with this sequence. We measured change in amyloid deposition over time using serial 11C Pittsburgh compound B (PIB) positron emission tomography and progression of neurodegeneration using serial structural magnetic resonance imaging. We studied 21 healthy cognitively normal subjects, 32 with amnestic mild cognitive impairment and 8 with Alzheimer's disease. Subjects were drawn from two sources—ongoing longitudinal registries at Mayo Clinic, and the Alzheimer's disease Neuroimaging Initiative (ADNI). All subjects underwent clinical assessments, MRI and PIB studies at two time points, approximately one year apart. PIB retention was quantified in global cortical to cerebellar ratio units and brain atrophy in units of cm3 by measuring ventricular expansion. The annual change in global PIB retention did not differ by clinical group (P = 0.90), and although small (median 0.042 ratio units/year overall) was greater than zero among all subjects (P < 0.001). Ventricular expansion rates differed by clinical group (P < 0.001) and increased in the following order: cognitively normal (1.3 cm3/year) < amnestic mild cognitive impairment (2.5 cm3/year) < Alzheimer's disease (7.7 cm3/year). Among all subjects there was no correlation between PIB change and concurrent change on CDR-SB (r = −0.01, P = 0.97) but some evidence of a weak correlation with MMSE (r =−0.22, P = 0.09). In contrast, greater rates of ventricular expansion were clearly correlated with worsening concurrent change on CDR-SB (r = 0.42, P < 0.01) and MMSE (r =−0.52, P < 0.01). Our data are consistent with a model of typical late onset Alzheimer's disease that has two main features: (i) dissociation between the rate of amyloid deposition and the rate of neurodegeneration late in life, with amyloid deposition proceeding at a constant slow rate while neurodegeneration accelerates and (ii) clinical symptoms are coupled to neurodegeneration not amyloid deposition. Significant plaque deposition occurs prior to clinical decline. The presence of brain amyloidosis alone is not sufficient to produce cognitive decline, rather, the neurodegenerative component of Alzheimer's disease pathology is the direct substrate of cognitive impairment and the rate of cognitive decline is driven by the rate of neurodegeneration. Neurodegeneration (atrophy on MRI) both precedes and parallels cognitive decline. This model implies a complimentary role for MRI and PIB imaging in Alzheimer's disease, with each reflecting one of the major pathologies, amyloid dysmetabolism and neurodegeneration.
Alzheimer's disease; amyloid imaging; magnetic resonance imaging, longitudinal imaging; mild cognitive impairment; Pittsburgh compound B
Frontotemporal lobar degeneration (FTLD) can be classified based on the presence of the microtubule-associated protein tau and the TAR DNA binding protein-43 (TDP-43). Future treatments will likely target these proteins, therefore it is important to identify biomarkers to help predict protein biochemistry.
To determine whether there is an MRI signature pattern of tau or TDP-43 using a large cohort of FTLD subjects and to investigate how patterns of atrophy change according to disease severity using a large autopsy-confirmed cohort of FTLD subjects.
Patterns of gray matter loss were assessed using voxel-based morphometry in 37 tau-positive and 44 TDP-43-positive subjects compared to 35 age and gender-matched controls, and compared to each other. Comparisons were also repeated in behavioral variant frontotemporal dementia (bvFTD) subjects (n = 15 tau-positive and n = 30 TDP-43-positive). Patterns of atrophy were also assessed according to performance on the Clinical Dementia Rating (CDR) scale and Mini-Mental State Examination (MMSE).
The tau-positive and TDP-43-positive groups showed patterns of frontotemporal gray matter loss compared to controls with no differences observed between the groups, for all subjects and for bvFTD subjects. Patterns of gray matter loss increased in a graded manner by CDR and MMSE with loss in the frontal lobes, insula and hippocampus in mild subjects, spreading to the temporal and parietal cortices and striatum in more advanced disease.
There is no signature pattern of atrophy for tau or TDP-43; however, patterns of atrophy in FTLD progress with measures of clinical disease severity.
Frontotemporal lobar degeneration; Autopsy; Tau; TAR DNA binding protein-43; Voxel-based morphometry; Clinical Dementia Rating Scale; Mini-Mental State Examination
Mutations in the progranulin gene (GRN) are an important cause of frontotemporal lobar degeneration (FTLD) with ubiquitin and TAR DNA-binding protein 43 (TDP43)-positive pathology. The clinical presentation associated with GRN mutations is heterogeneous and may include clinical probable Alzheimer's disease. All GRN mutations identified thus far cause disease through a uniform disease mechanism, i.e. the loss of functional GRN or haploinsufficiency. To determine if expression of GRN in plasma could predict GRN mutation status and could be used as a biological marker, we optimized a GRN ELISA and studied plasma samples of a consecutive clinical FTLD series of 219 patients, 70 control individuals, 72 early-onset probable Alzheimer's disease patients and nine symptomatic and 18 asymptomatic relatives of GRN mutation families. All FTLD patients with GRN loss-of-function mutations showed significantly reduced levels of GRN in plasma to about one third of the levels observed in non-GRN carriers and control individuals (P < 0.001). No overlap in distributions of GRN levels was observed between the eight GRN loss-of-function mutation carriers (range: 53–94 ng/ml) and 191 non-GRN mutation carriers (range: 115–386 ng/ml). Similar low levels of GRN were identified in asymptomatic GRN mutation carriers. Importantly, ELISA analyses also identified one probable Alzheimer's disease patient (1.4%) carrying a loss-of-function mutation in GRN. Biochemical analyses further showed that the GRN ELISA only detects full-length GRN, no intermediate granulin fragments. This study demonstrates that using a GRN ELISA in plasma, pathogenic GRN mutations can be accurately detected in symptomatic and asymptomatic carriers. The ∼75% reduction in full-length GRN, suggests an unbalanced GRN metabolism in loss-of-function mutation carriers whereby more GRN is processed into granulins. We propose that plasma GRN levels could be used as a reliable and inexpensive tool to identify all GRN mutation carriers in early-onset dementia populations and asymptomatic at-risk individuals.
Progranulin; ELISA; frontotemporal lobar degeneration; Alzheimer's disease