Magnetic Resonance Imaging-based Comparative Research in Different Mild Cognitive Impairment Subtype

Dementia is one of the main chronic non-communicable diseases associated with disability, institutionalization, and mortality among elderly individuals. Alzheimer's disease (AD) and vascular dementia (VD) are considered to be the main types of dementia. A widely shared view is that future treatment strategies need to focus on treatment of the earliest stages of the disease. Mild cognitive impairment (MCI) constitutes an intermediate stage between normal aging and dementia. Vascular cognitive disorders (VCD) is an umbrella term representing a wide spectrum of cognitive disorder evoked by or associated with vascular causes. It encompasses patients suffering from a range of types of cognitive impairment, from mild impairment to VD. VCD predementia (VCD-P) is at the same stage of MCI. Amnestic MCI (aMCI) is a subtype of MCI, which is also considered to be the clinical transition stage between normal aging and AD, and has been applied to detect the emerging dementia. In VCD, infarcts or profuse white matter disease are considered the cause of cognitive decline. By contrast, AD is one of the most common progressive neurodegenerative disorders thought to be caused by amyloid aggregation and the formation of tau tangles. Both VCD-P and aMCI have a deficit in cognitive domains, and may have the same chief complaints of memory deficit. If it can be clear which will turn into what type of dementia in patients with cognitive impairment stage, it can not only make us more early intervention treatment to the patients, but also can save a lot of social resources and economic costs in clinic. By applying the resting state functional magnetic resonance (fMRI), structural magnetic resonance imaging (sMRI) and diffusion tensor magnetic resonance imaging (DTI) multimodal magnetic resonance (NMR) technology, the project comprehensive analysis comparison of neurodegenerative and blood vessels of brain function in patients with mild cognitive impairment and structural abnormalities connection mode. This project in order to reveal the cognitive impairment disease neural circuits in the development of the network connection and its change rule. People can further understand the pathogenesis of cognitive impairment, discover new will provide a scientific basis for prevention, diagnosis and treatment.

The investigators use both psychological tests and neuroimage to compare the differences between the two groups.

All the participants received a battery of neuropsychological tests to assess general mental status and other cognitive domains, including visual-spatial ability, executive function, language, memory, attention, and general intellectual ability. These tests included the CDR scale, the Mini-Mental State Examination(MMSE), the Montreal Cognitive Assessment(MoCA), clock drawing test (CDT), Auditory Verbal Learning Test (AVLT), activities of daily living scale(ADL) and Hamilton Depression Scale and HIS. All these evaluations were performed by two attending neurologists.

All participants were scanned on a 3.0 T Siemens scanner within a single session.

Each participant received a magnetization prepared rapidly acquired gradient echo (MPRAGE) T1-weighted scan (repetition time [TR], 1900 ms; echo time [TE], 2.2 ms; inversion time, 900 ms; matrix, 256×256; number of excitations, 1; thickness, 1 mm; 176 slices) Resting state functional images were collected using an echo-planar imaging (EPI) sequence with the following parameters: repetition time (TR)= 2000 ms; echo time (TE)=40 ms; flip angle=90°; number of slices=28; slice thickness=4 mm; gap=1 mm; voxel size=4×4×4 mm3; and matrix=64×64. Participants were asked to lie quietly in the scanner with their eyes closed during the data acquisition. This scan lasted for 478 s. For each subject, the first five volumes were discarded to allow for T1 equilibration effects and the adaptation of the subjects to the circumstances, leaving 234 images for further analysis.

The diffusion weighted imaging scans were acquired on a 3.0T Siemens Tim Trio MRI scanner. Three diffusion echo-planar imaging sequence with one zero-weighted image (b =0 s/mm2) and thirty diffusion sensitizing orientations (b =1000 s/mm2) was used with the following specifications: slice thickness=2 mm; 90 slices; repetition time = 11000 ms; echo time = 98 ms; voxel size = 2 mm isotropic; flip angle=90°; acquisition matrix = 128 mm×116 mm .

Inclusion Criteria:

• For all the participants

  1. Right-hand Chinese Han people
  2. Sufficient with Mandarin language

• For VCD-P group,

  1. Clinical diagnosis of Vascular cognitive disorders
  2. Between the stage of cognitive normal and dementia
  3. Clinical diagnosis of subcortical vascular diseases

• For aMCI group

  1. Clinical diagnosis of aMCI
  2. Between the stage of cognitive normal and dementia
  3. The hippocampal atrophy confirmed by structural MRI

Exclusion Criteria:

• psychiatric disease, neurological disorder and systemic disease
• a suffering of visual abnormalities, severe aphasia or palsy
• any medical or psychological conditions