The MRI Diffusion Tensor Imaging Study Of Behavioural Variant Frontotemporal Dementia

Objective: Frontotemporal dementia(FTD)is a common form of dementia in presenium with features of early onset,rapid progress and obvious impairment on social function.Behavioural variant frontotemporal dementia(bvFTD),one of the four phenotypes of FTD,is characterized by prominent abnormal behavior which may be overlap with other mental disorders,and less obvious cognitive functional impairment during its early phase.As a result,it is hard to diagnose.The purpose of this study is to investigate diagnosis efficiency of the characteristic of early symptoms and brain structural image of bvFTD,and to explore the relationship about MRI diffusion tensor imaging(MRI-DTI)to the early diagnosis of bv-FTD.Methods: 1.Early clinical symptoms of 23 patients with bvFTD diagnosed according to International behavioural variant FTD criteria consortium(FTDC)were retrospectively analyzed.Three of them were with characteristic clinical manifestations.,The characteristic clinical features which extracted from these symptoms were helpful to early diagnosis.2.Patients with bvFTD were assessed with Frontotemporal Dementia Rating Scale(FRS).The relationships among the logic score of FRS,Mini Mental State Examination(MMSE),Activities of Daily Living(ADL)and Clinical Dementia Rating(CDR)were analyzed by correlation analysis.3.Image acquisition was collected by Siemens Verio 3T MRI scanner echo planar imaging(EPI).White matter of eight patients diagnosed as probable bvFTD,eight matched patients with Alzheimer's disease and eight normal controls were assessed using diffusion tensor imaging(DTI)measures of fractional anisotropy(FA)and diffusivity components.After obtaining 3DT1 and diffusion weighted imagines(DWI),statistical analysis was carried out using tract-based spatial statistics(TBSS)to measure FA and mean diffusivity(MD)to explore the characteristic of WM tissue changes in individuals with bvFTD and the value of FA and MD in the diagnosis of the disease.Results: 1.It was rare to see symptoms of bvFTD begin to appear before 40 years old and it was often misdiagnosed as schizophrenia because of apathy and stereotyped behavior in the early stage of FTD.The average onset age of bvFTD group was 51±11 years old,and the average duration of diagnosis was 2.4±1.5 years.Symptoms associated with impaired memory were existed as well in bvFTD.It was shown from this retrospective study that apathy,loss of empathy,executive deficits and impaired memory(>80%)were very common in bvFTD,while the frequency of disinhibition and stereotyped behavior were less than those of reported abroad.2.Both ADL and CDR had a strong negative correlation with FRS and with the value r were-0.685(p<0.001)and-0.696(p<0.001)respectively.There was a positive correlation between FRS and MMSE(r=0.488,p<0.001).3.It was shown from DTI that patients with bvFTD were associated with reductions of FA in bilateral anterior thalamic radiation,cingulum,hippocampal,forceps major,forceps minor,bilateral inferior fronto-occipital fasciculus,inferior longitudinal fasciculus,superior longitudinal fasciculus,uncinate fasciculus compared to controls.Meanwhile,bvFTD was associated with greater reductions of FA in left anterior thalamic radiation,forceps minor,left cingulum and inferior fronto-occipital fasciculus,right inferior longitudinal fasciculus,left uncinate fasciculus compared to Alzheimer's disease.Moreover the white matter degradation seems to be more prominent in FTD than in Alzheimer's disease.Conclusions: It is hard to make an accurate diagnosis in the early stage of bvFTD because of the early symptoms such as apathy,social withdrawal and stereotyped behavior which may be misdiagnosed as other mental disorders.FRS was correlated with ADL and CDR which are common measurements in dementia.It was shown from MRI-DTI that there was significant white matter damage in patients with bvFTD as well.But unlike AD,WM tissue in left anterior thalamic radiation,forceps minor,left cingulum and inferior fronto-occipital fasciculus were more severely damaged and the damage is asymmetric which may be helpful to early diagnosis.