Conventional magnetic resonance imaging key features for distinguishing pathologically confirmed corticobasal degeneration from its mimics: a retrospective analysis of the J-VAC study.

PURPOSE: Due to the indistinguishable clinical features of corticobasal syndrome (CBS), the antemortem differentiation between corticobasal degeneration (CBD) and its mimics remains challenging. However, the utility of conventional magnetic resonance imaging (MRI) for the diagnosis of CBD has not been sufficiently evaluated. This study aimed to investigate the diagnostic performance of conventional MRI findings in differentiating pathologically confirmed CBD from its mimics. METHODS: Semiquantitative visual rating scales were employed to assess the degree and distribution of atrophy and asymmetry on conventional T1-weighted and T2-weighted images. Additionally, subcortical white matter hyperintensity (SWMH) on fluid-attenuated inversion recovery images were visually evaluated. RESULTS: In addition to 19 patients with CBD, 16 with CBD mimics (progressive supranuclear palsy (PSP): 9, Alzheimer's disease (AD): 4, dementia with Lewy bodies (DLB): 1, frontotemporal lobar degeneration with TAR DNA-binding protein of 43 kDa(FTLD-TDP): 1, and globular glial tauopathy (GGT): 1) were investigated. Compared with the CBD group, the PSP-CBS subgroup showed severe midbrain atrophy without SWMH. The non-PSP-CBS subgroup, comprising patients with AD, DLB, FTLD-TDP, and GGT, showed severe temporal atrophy with widespread asymmetry, especially in the temporal lobes. In addition to over half of the patients with CBD, two with FTLD-TDP and GGT showed SWMH, respectively. CONCLUSION: This study elucidates the distinct structural changes between the CBD and its mimics based on visual rating scales. The evaluation of atrophic distribution and SWMH may serve as imaging biomarkers of conventional MRI for detecting background pathologies.

Pure argyrophilic grain disease revisited: independent effects on limbic, neocortical, and striato-pallido-nigral degeneration and the development of dementia in a series with a low to moderate Braak stage.

Agyrophilic grains (AGs) are age-related limbic-predominant lesions in which four-repeat tau is selectively accumulated. Because previous methodologically heterogeneous studies have demonstrated inconsistent findings on the relationship between AGs and dementia, whether AGs affect cognitive function remains unclear. To address this question, we first comprehensively evaluated the distribution and quantity of Gallyas-positive AGs and the severity of neuronal loss in the limbic, neocortical, and subcortical regions in 30 cases of pure argyrophilic grain disease (pAGD) in Braak stages I-IV and without other degenerative diseases, and 34 control cases that had only neurofibrillary tangles with Braak stages I-IV and no or minimal Aß deposits. Then, we examined whether AGs have independent effects on neuronal loss and dementia by employing multivariate ordered logistic regression and binomial logistic regression. Of 30 pAGD cases, three were classified in diffuse form pAGD, which had evident neuronal loss not only in the limbic region but also in the neocortex and subcortical nuclei. In all 30 pAGD cases, neuronal loss developed first in the amygdala, followed by temporo-frontal cortex, hippocampal CA1, substantia nigra, and finally, the striatum and globus pallidus with the progression of Saito AG stage. In multivariate analyses of 30 pAGD and 34 control cases, the Saito AG stage affected neuronal loss in the amygdala, hippocampal CA1, temporo-frontal cortex, striatum, globus pallidus, and substantia nigra independent of the age, Braak stage, and limbic-predominant age-related TDP-43 encephalopathy (LATE-NC) stage. In multivariate analyses of 23 pAGD and 28 control cases that lacked two or more lacunae and/or one or more large infarctions, 100 or more AGs per × 400 visual field in the amygdala (OR 10.02, 95% CI 1.12-89.43) and hippocampal CA1 (OR 12.22, 95% CI 1.70-87.81), and the presence of AGs in the inferior temporal cortex (OR 8.18, 95% CI 1.03-65.13) affected dementia independent of age, moderate Braak stages (III-IV), and LATE-NC. Given these findings, the high density of limbic AGs and the increase of AGs in the inferior temporal gyrus may contribute to the occurrence of dementia through neuronal loss, at least in cases in a low to moderate Braak stage.

Potential dopaminergic deficit in patients with geriatric psychiatric disorders as revealed by DAT-SPECT: a cross-sectional study.

BACKGROUND: It has been reported that patients with geriatric psychiatric disorders include many cases of the prodromal stages of neurodegenerative diseases. Abnormal 123I-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl) nortropane dopamine transporter single-photon emission computed tomography (DAT-SPECT) reveals a nigrostriatal dopaminergic deficit and is considered useful to detect dementia with Lewy bodies and Parkinson's disease as well as progressive supranuclear palsy and corticobasal degeneration. We aimed to determine the proportion of cases that are abnormal on DAT-SPECT in patients with geriatric psychiatric disorders and to identify their clinical profile. METHODS: The design is a cross-sectional study. Clinical findings of 61 inpatients aged 60 years or older who underwent DAT-SPECT and had been diagnosed with psychiatric disorders, but not neurodegenerative disease or dementia were analysed. RESULTS: 36 of 61 (59%) had abnormal results on DAT-SPECT. 54 of 61 patients who had DAT-SPECT (89%) had undergone 123I-metaiodobenzylguanidine myocardial scintigraphy (123I-MIBG scintigraphy); 12 of the 54 patients (22.2%) had abnormal findings on 123I-MIBG scintigraphy. There were no cases that were normal on DAT-SPECT and abnormal on 123I-MIBG scintigraphy. DAT-SPECT abnormalities were more frequent in patients with late-onset (55 years and older) psychiatric disorders (69.0%) and depressive disorder (75.7%), especially late-onset depressive disorder (79.3%). CONCLUSION: Patients with geriatric psychiatric disorders include many cases showing abnormalities on DAT-SPECT. It is suggested that these cases are at high risk of developing neurodegenerative diseases characterised by a dopaminergic deficit. It is possible that patients with geriatric psychiatric disorders with abnormal findings on DAT-SPECT tend to show abnormalities on DAT-SPECT first rather than on 123I-MIBG scintigraphy.

Clinical course of pathologically confirmed corticobasal degeneration and corticobasal syndrome.

The clinical presentation of corticobasal degeneration is diverse, while the background pathology of corticobasal syndrome is also heterogeneous. Therefore, predicting the pathological background of corticobasal syndrome is extremely difficult. Herein, we investigated the clinical findings and course in patients with pathologically, genetically and biochemically verified corticobasal degeneration and corticobasal syndrome with background pathology to determine findings suggestive of background disorder. Thirty-two patients were identified as having corticobasal degeneration. The median intervals from the initial symptoms to the onset of key milestones were as follows: gait disturbance, 0.0 year; behavioural changes, 1.0 year; falls, 2.0 years; cognitive impairment, 2.0 years; speech impairment, 2.5 years; supranuclear gaze palsy, 3.0 years; urinary incontinence, 3.0 years; and dysphagia, 5.0 years. The median survival time was 7.0 years; 50% of corticobasal degeneration was diagnosed as corticobasal degeneration/corticobasal syndrome at the final presentation. Background pathologies of corticobasal syndrome (n = 48) included corticobasal degeneration (33.3%), progressive supranuclear palsy (29.2%) and Alzheimer's disease (12.5%). The common course of corticobasal syndrome was initial gait disturbance and early fall. In addition, corticobasal degeneration-corticobasal syndrome manifested behavioural change (2.5 years) and cognitive impairment (3.0 years), as the patient with progressive supranuclear palsy-corticobasal syndrome developed speech impairment (1.0 years) and supranuclear gaze palsy (6.0 years). The Alzheimer's disease-corticobasal syndrome patients showed cognitive impairment (1.0 years). The frequency of frozen gait at onset was higher in the corticobasal degeneration-corticobasal syndrome group than in the progressive supranuclear palsy-corticobasal syndrome group [P = 0.005, odds ratio (95% confidence interval): 31.67 (1.46-685.34)]. Dysarthria at presentation was higher in progressive supranuclear palsy-corticobasal syndrome than in corticobasal degeneration-corticobasal syndrome [P = 0.047, 6.75 (1.16-39.20)]. Pyramidal sign at presentation and personality change during the entire course were higher in Alzheimer's disease-corticobasal syndrome than in progressive supranuclear palsy-corticobasal syndrome [P = 0.011, 27.44 (1.25-601.61), and P = 0.013, 40.00 (1.98-807.14), respectively]. In corticobasal syndrome, decision tree analysis revealed that 'freezing at onset' or 'no dysarthria at presentation and age at onset under 66 years in the case without freezing at onset' predicted corticobasal degeneration pathology with a sensitivity of 81.3% and specificity of 84.4%. 'Dysarthria at presentation and age at onset over 61 years' suggested progressive supranuclear palsy pathology, and 'pyramidal sign at presentation and personality change during the entire course' implied Alzheimer's disease pathology. In conclusion, frozen gait at onset, dysarthria, personality change and pyramidal signs may be useful clinical signs for predicting background pathologies in corticobasal syndrome.

Four-repeat tauopathies and late-onset psychiatric disorders: Etiological relevance or incidental findings?

Argyrophilic grain disease (AGD), progressive supranuclear palsy (PSP) and corticobasal degeneration are four-repeat (4R) tauopathies that develop in the presenium or later. Whether these diseases are associated with the occurrence of late-onset psychiatric disorders remains unclear. To facilitate the accumulation of clinicopathological findings regarding this issue, we here present a selected series of 11 cases that clinically developed psychotic disorder (n = 7; age at onset: 41-75 years), depressive disorder (n = 1; 49 years), bipolar disorder (n = 2; 32 and 37 years) and somatoform disorder (n = 1; 88 years), and had at least one pathological hallmark of these tauopathies. The mean age at death was 74.3 years. No case showed dementia, at least in the early stage of the course. Nine cases had AGD. Granular fuzzy astrocytes in the amygdala were noted in all AGD cases and one non-AGD case. Two AGD cases had tufted astrocytes (TAs) in the amygdala but not in the frontal cortex and striatum. Three AGD and two non-AGD cases had TAs in the frontal cortex and/or striatum but not in the amygdala. One AGD case had a small number of astrocytic plaques in the frontal cortex, striatum and globus pallidus. Only one case was diagnosed as atypical PSP according to the NINDS-PSP neuropathological criteria. No case had high-level Alzheimer's disease pathology, Lewy body disease or limbic-predominant age-related TDP-43 encephalopathy. Two cases had mild neuronal loss in the hippocampus and substantia nigra, respectively. Clinicopathological studies focusing especially on early changes of 4R tauopathies, as well as the development of surrogate markers of these diseases, may be necessary for better understanding of the pathogenic backgrounds of late-onset psychiatric disorders.

Facial expression recognition in mild cognitive impairment and dementia: is the preservation of happiness recognition hypothesis true?

AIM: Social cognition encompasses facial expression recognition (FER), theory of mind, and empathy. Although studies examining FER in large numbers of patients with mild cognitive impairment (MCI) or dementia are rare, relative preservation of happiness recognition in dementia was reported in some studies. In this study, we examined performance on FER tests and its relationship to clinical demographics and other cognitive function test scores in patients with cognitive decline. METHODS: The present study administered an FER test and several cognitive tests to outpatients at a memory clinic. The FER test presents four facial expressions (happiness, surprise, anger, and sadness). A total of 187 patients were placed in one of the three groups based on their cognitive status: dementia group (n = 63), MCI group (n = 92), and normal cognition group (n = 32). RESULTS: The total scores on the FER test significantly differed among the three groups (normal > MCI > dementia). In the recognition of happiness and surprise, the dementia group had significantly lower scores than the normal cognition group. There were no significant differences in the recognition of anger and sadness scores among the three groups. The FER scores for happiness and surprise were primarily related to executive function scores, but the FER scores for anger and sadness were primarily related to age. CONCLUSIONS: We note the difference in recognition of causative factors among the four emotions (happiness, surprise, anger, sadness). Our study raises serious doubts about the preservation of happiness recognition hypothesis in dementia based on FER tests.

Factors associated with development and distribution of granular/fuzzy astrocytes in neurodegenerative diseases.

Granular/fuzzy astrocytes (GFAs), a subtype of "aging-related tau astrogliopathy," are noted in cases bearing various neurodegenerative diseases. However, the pathogenic significance of GFAs remains unclear. We immunohistochemically examined the frontal cortex, caudate nucleus, putamen and amygdala in 105 cases composed of argyrophilic grain disease cases (AGD, N = 26), and progressive supranuclear palsy (PSP, N = 10), Alzheimer's disease (AD, N = 20) and primary age-related tauopathy cases (PART, N = 18) lacking AGD, as well as 31 cases bearing other various neurodegenerative diseases to clarify (i) the distribution patterns of GFAs in AGD, and PSP, AD and PART lacking AGD, (ii) the impacts of major pathological factors and age on GFA formation and (iii) immunohistochemical features useful to understand the formation process of GFAs. In AGD cases, GFAs consistently occurred in the amygdala (100%), followed by the putamen (69.2%) and caudate nucleus and frontal cortex (57.7%, respectively). In PSP cases without AGD, GFAs were almost consistently noted in all regions examined (90-100%). In AD cases without AGD, GFAs were less frequent, developing preferably in the putamen (35.0%) and caudate nucleus (30.0%). PART cases without AGD had GFAs most frequently in the amygdala (35.3%), being more similar to AGD than to AD cases. Ordered logistic regression analyses using all cases demonstrated that the strongest independent factor of GFA formation in the frontal cortex and striatum was the diagnosis of PSP, while that in the amygdala was AGD. The age was not significantly associated with GFA formation in any region. In GFAs in AGD cases, phosphorylation and conformational change of tau, Gallyas-positive glial threads indistinguishable from those in tufted astrocytes, and the activation of autophagy occurred sequentially. Given these findings, AGD, PSP, AD and PART cases may show distinct distributions of GFAs, which may provide clues to predict the underlying processes of primary tauopathies.

Sally-Anne test and regional cerebral blood flow in Alzheimer's disease dementia.

AIM: It was recently reported that theory of mind is disturbed in mild Alzheimer's disease dementia (ADD). Some studies have reported reduced scores of ADD patients on false belief tests, even on first-order false belief tests. However, few studies have pursued the neural substrate of false belief tests in patients with ADD in a real-world setting. METHODS: Sixty-three patients with ADD from outpatient units took the Sally-Anne test and underwent brain single-photon emission computed tomography. Of these patients, 29 answered the Sally-Anne test correctly (successful group) and 34 incorrectly (unsuccessful group). We compared the regional cerebral blood flow between the successful and unsuccessful groups. RESULTS: A comparison of the two groups showed a significantly lower uptake in the bilateral posterior cingulate gyrus in the unsuccessful group than in the successful group. CONCLUSIONS: The posterior cingulate gyrus is known to be particularly activated when individuals remember personal events and infer the mental states of others. We suppose that memory or mentalization in the posterior cingulate gyrus-or both-is essential for patients with ADD to be able to pass the Sally-Anne test.

Patient affect and caregiver burden in dementia.

BACKGROUND: Numerous studies focusing on the burden of caregivers of dementia patients have been published. However, there have been few studies focusing on positive affect as an important factor affecting the caregiver burden, and only a few studies comparing the caregiver burden between different dementia diseases have been reported. METHODS: Three hundred and thirty-seven consecutive caregivers of people with dementia participated in this study. The caregiver burden was evaluated by the short version of the Japanese version of the Zarit Burden Interview. RESULTS: Positive affect scores had a significant relationship with the scores of the short version of the Zarit Burden Interview. Caregivers for patients with dementia with Lewy bodies or frontotemporal dementia suffered from a greater burden than those for patients with Alzheimer's disease dementia. CONCLUSIONS: The caregiver burden differed between people caring for patients with different dementia diseases. Positive affect of dementia patients has a significant relationship with caregiver burden, independently from neuropsychiatric symptoms of patients.

Validation of Addenbrooke's cognitive examination III for detecting mild cognitive impairment and dementia in Japan.

BACKGROUND: Early detection of mild cognitive impairment (MCI) and dementia is very important to begin appropriate treatment promptly and to prevent disease exacerbation. We investigated the screening accuracy of the Japanese version of Addenbrooke's Cognitive Examination III (ACE-III) to diagnose MCI and dementia. METHODS: The original ACE-III was translated and adapted to Japanese. It was then administered to a Japanese population. The Hasegawa Dementia Scale-revised (HDS-R) and Mini-mental State Examination (MMSE) were also applied to evaluate cognitive dysfunction. In total, 389 subjects (dementia = 178, MCI = 137, controls = 73) took part in our study. RESULTS: The optimal ACE-III cut-off scores to detect MCI and dementia were 88/89 (sensitivity 0.77, specificity 0.92) and 75/76 (sensitivity 0.82, specificity 0.90), respectively. ACE-III was superior to HDS-R and MMSE in the detection of MCI or dementia. The internal consistency, test-retest reliability, and inter-rater reliability of ACE-III were excellent. CONCLUSIONS: ACE-III is a useful cognitive test to detect MCI and dementia. ACE-III may be widely useful in clinical practice.

Astrocytic Tau Pathologies in Argyrophilic Grain Disease and Related Four-repeat Tauopathies.

Neurodegenerative diseases in which tau accumulation plays a cardinal role in the pathogenic process are called tauopathies, and when tau isoforms having four repeats of the microtubule binding sites, four-repeat tau, are selectively accumulated as pathological hallmarks, the term four-repeat tauopathy is used. The major four-repeat tauopathies are progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and argyrophilic grain disease (AGD). Historically, neuronal cytopathologies, e.g., neurofibrillary tangles and ballooned neurons, were emphasized as characteristic lesions in PSP and CBD. Now, however, astrocytic tau pathologies, i.e., tufted astrocytes (TAs) and astrocytic plaques (APs), are considered to be highly disease-specific lesions. Although granular/fuzzy astrocytes (GFAs) frequently develop in the limbic system in AGD cases, the specificity is not conclusive yet. Some AGD cases have a few TAs, and to a lesser frequency, a few APs in the frontal cortex and subcortical nuclei. The number of astrocytic tau pathologies including TAs and GFAs increases with the progression of AGD. In this paper, histopathological features of astrocytic tau pathologies in PSP, CBD, and AGD are first reviewed. Then, recent findings regarding the coexistence of these tauopathies are summarized from a viewpoint of astrocytic tau pathologies. Further biochemical and pathological studies focusing tau-positive astrocytic lesions may be useful to increase understanding of the pathological process in four-repeat tauopathies and to develop novel therapeutic strategies for patients with these diseases.

Neuropathological comorbidity associated with argyrophilic grain disease.

Argyrophilic grain disease (AGD) is a common four-repeat tauopathy in elderly people. While dementia is a major clinical picture of AGD, recent studies support the possibility that AGD may be a pathological base in some patients with mild cognitive impairment, late-onset psychosis, bipolar disorder and depression. AGD often coexists with various other degenerative changes. The frequency of AGD in progressive supranuclear palsy (PSP) cases was reported to range from 18.8% to 80%. The frequency of AGD in corticobasal degeneration (CBD) cases tends to be higher than that in PSP cases, ranging from 41.2% to 100%. Conversely, in our previous study of the frequencies of mild PSP and CBD pathologies in AGD cases, five of 20 AGD cases (25%) had a few Gallyas-positive tufted astrocytes, six cases (30%) had a few granular/fuzzy astrocytes, and one case (5.0%) had a few Gallyas-positive astrocytic plaques in the putamen, caudate nucleus and/or superior frontal gyrus. Both Gallyas-positive tufted astrocytes and Gallyas-negative tau-positive granular/fuzzy astrocytes preferentially developed in the putamen, caudate nucleus and superior frontal cortex in AGD cases, being consistent with the predilection sites of Gallyas-positive tufted astrocytes in PSP cases. Further, in AGD cases, the quantities of Gallyas-positive tufted astrocytes, overall tau-positive astrocytes, and tau-positive neurons in the subcortical nuclei and superior frontal cortex were significantly correlated with Saito AGD stage, respectively. The frequency of AGD in AD cases was reported to reach up to 25% when using four-repeat tau immunohistochemistry. Pretangles are essential pathologies in AGD; however, the Braak stage of three-repeat tau-positive NFTs, which may indicate mild AD pathology or primary age-related tauopathy, was not correlated with Saito AGD stage. Clinicians should be aware of the possibility that coexisting AGD may impact clinical and radiological features in cases of other degenerative diseases.

Frontotemporal lobar degeneration due to P301L tau mutation showing apathy and severe frontal atrophy but lacking other behavioral changes: A case report and literature review.

The clinical features in cases that have mutations in the microtubule-associated protein tau gene but lack prominent behavioral changes remain unclear. Here, we describe detailed clinical and pathological features of a case carrying the P301L tau mutation that showed only apathy until the middle stage of the course. The mother of this case was suspected to have mild cognitive decline at age 46. However, before she was fully examined, she had a subarachnoid hemorrhage at age 49 and died at age 53. An autopsy was not done. The proband of this pedigree, a 60-year-old right-handed Japanese man at the time of death, began to make mistakes at work at the age of 51 years. Until age 54, he showed only mild apathy with bradykinesia. Insight was well spared. Parkinsonism and echolalia developed at age 55, and pyramidal signs and oral tendency at age 57. Personality change, disinhibition, stereotypy, or semantic memory impairment was not found throughout the course. The final neurological diagnosis was unspecified dementia. Pathological examination demonstrated numerous round four-repeat tau-positive three-repeat tau-negative or perinuclear ring-like neuronal cytoplasmic inclusions with many ballooned neurons in the frontal and temporal cortices and hippocampus. Genetic analysis using frozen brain tissue demonstrated a P301L tau mutation. Among 31 previously reported cases bearing the P301L tau mutation for which the data regarding initial symptoms are available, one clinical case showed only apathy with depression in the early stage. Given these findings, clinicians should be aware that a clinical course characterized only by apathy for several years, which can be misdiagnosed as a psychiatric disorder, is one of the clinical presentations associated with P301L tau mutation.

Pick's disease with neuronal four-repeat tau accumulation in the basal ganglia, brain stem nuclei and cerebellum.

It is very rare that cases of Pick's disease, a representative three-repeat (3R) tauopathy, also have significant four-repeat (4R) tau accumulation. Here, we report a Pick's disease case that clinically showed behavioral variant frontotemporal dementia without motor disturbance during the course, and pathologically had 3R tau-positive Pick bodies as well as numerous 4R tau-positive neuronal cytoplasmic inclusions (NCIs). Abundant 3R tau-positive 4R tau-negative spherical or horseshoe-shaped Pick bodies were found in the frontotemporal cortex, limbic region, striatum and pontine nucleus. On the other hand, many 4R tau-positive, 3R tau-negative, Gallyas-negative dot-, rod- or intertwined skein-like NCIs were found mainly in the subthalamic nucleus, pontine nucleus, inferior olivary nucleus and cerebellar dentate nucleus. Tufted astrocytes, astrocytic plaques, argyrophilic grains or globular glial inclusions were absent. Double-labeling immunofluorescence demonstrated that 3R tau was hardly accumulated in 4R tau-positive inclusions. On tau immunoblotting, while 60 and 64 kDa bands were demonstrated in the frontal cortex, 60, 64 and 68 kDa bands, as well as the 33 kDa tau fragments that are reported to be characteristic of progressive supranuclear palsy brains, were found in the basal ganglia and cerebellum. No mutation was identified in the tau gene. The present case suggests that, although probably rare, some Pick's disease cases have non-negligible 4R tau pathology in the subcortical nuclei, and that such 4R tau pathology can affect the evaluation of the distribution of AT8-positive tau pathology in Pick's disease cases.

Positive affect and regional cerebral blood flow in Alzheimer's disease.

Quality of life (QOL) has been recently recognized as the central purpose of healthcare, and positive affect is one of the core dimension of QOL. However, positive affect among patients with dementia or Alzheimer's disease (AD) has not received much attention in the medical research field. One hundred sixteen consecutive patients with AD were recruited from the outpatient units of the Memory Clinic of Okayama University Hospital. The positive affect score was evaluated using the positive affect domain of the Quality of Life questionnaire for Dementia (QOL-D). Patients underwent brain SPECT with 99mTc-ethylcysteinate dimer. Positive affect scores were inversely related to apathy scores, subjective depressive scores, and delusion scores. After removing the effects of age, sex, duration of education, and cognitive function, positive affect scores showed a significant correlation with regional cerebral blood flow in the left premotor and superior frontal gyri. The left premotor and superior frontal area is significantly involved in the pathogenesis of the decrease of positive affect in AD. Apathy and depression are closely related to the prefrontal area in AD, and they may affect the relationship between positive affect and the left prefrontal area.

Behavioral variant of frontotemporal dementia: Fundamental clinical issues associated with prediction of pathological bases.

Behavioral variant of frontotemporal dementia (bvFTD) is a clinical syndrome characterized mainly by behavioral symptoms due to frontal dysfunction. Major neurodegenerative bases of bvFTD include Pick's disease, frontotemporal lobar degeneration with trans-activation response DNA protein 43-positive inclusions, corticobasal degeneration, and progressive supranuclear palsy. Early disinhibition characterized by socially inappropriate behaviors, loss of manners, and impulsive, rash and careless actions is the most important clinical feature of bvFTD. On the other hand, it was reported that clinical presentations of some Alzheimer's disease cases and patients with psychiatric disorders (e.g., addictive disorders, gambling disorder and kleptomania) often resemble that of bvFTD. Although clinical differentiation of 'true' bvFTD cases with frontotemporal lobar degeneration (FTLD) pathology from mimicking cases without it is not always easy, evaluation of the following features, which were noted in autopsy-confirmed FTLD cases and/or clinical bvFTD cases with circumscribed lobar atrophy, may often provide clues for the diagnosis. (i) The initial symptoms frequently develop at 65 years or younger, and (ii) 'socially inappropriate behaviors' can be frequently interpreted as contextually inappropriate behaviors prompted by environmental visual and auditory stimuli. Taking a detailed history usually reveals various kinds of such behaviors in various situations in everyday life rather than the repetition of a single kind of behavior (e.g., repeated shoplifting). (iii) A correlation between the distribution of cerebral atrophy and neurological and behavioral symptoms is usually observed, and the proportion of FTLD cases with right side-predominant cerebral atrophy may be higher in a psychiatric setting than a neurological setting. Finally, (iv) whether the previous course and the combination of symptoms observed at the first medical visit can be explained by major evolution patterns of clinical syndromes in pathologically confirmed FTLD cases should be considered. These views may provide clues to differentiate FTLD from Alzheimer's disease and to predict a subsequent clinical course and therapeutic interventions needed in the future.