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RELATIONSHIP AMONG TAU, AMYLOID BURDEN AND BRAIN ATROPHY IN EARLY-ONSET ALZHEIMER'S DISEASE AND LATE-ONSET ALZHEIMER'S DISEASE

      Background

      We investigated the relationship among 18F-THK 5351 PET tau retention, amyloid burden and brain atrophy in early-onset Alzheimer's disease (EOAD) and late-onset Alzheimer's disease (LOAD).

      Methods

      We included 158 participants including 54 patients with EOAD (onset age < 65), 41 patients with LOAD (onset age ≥ 65), 8 young participants (age < 50) and 55 elderly participants (age ≥ 50) with normal cognition, who completed 18F-THK5351 PET scans, 18F-flutemetamol (FMM) PET scans and 3T MRI. Brain atrophy was evaluated with cortical thickness and hippocampal volume. To investigate the distinct features of inter-regional correlation of THK and FMM retention, connectivity matrices were calculated in EOAD and LOAD, respectively.

      Results

      Ninety-eight percent (53/54) of patients with EOAD were positive for FMM retention, whereas 82.9 % (34/41) of patients with LOAD were found as FMM positive. LOAD showed significant positive correlation between global FMM retention and global THK retention, cortical THK retention, and THK retention in the lateral temporal cortex. Meanwhile, EOAD did not show any significant correlation between global FMM retention and THK retention. On the contrary, only EOAD patients had significant negative correlation between mean cortical thickness or hippocampal volume and global THK retention, cortical THK retention, or THK retention in the lateral temporal cortex. THK retention in the mesial temporal areas did not have significant correlation with mean cortical thickness or hippocampal volume in any groups. There was no significant correlation between global FMM retention and brain atrophy in any groups. There were positive correlations between THK retention in the frontal, parietal, occipital cortices or precuneus and FMM retention in the frontal, parietal cortices or precuneus. EOAD had weak positive correlation between THK and FMM retention only in the occipital cortex.

      Conclusions

      LOAD showed gradual increase in both tau and amyloid and those two pathologies have association to each other. Whereas, in EOAD, tau and amyloid may develop more abruptly and independently. Brain atrophy was associated with tau burden in EOAD, however, was not correlated with amyloid burden in EOAD or LOAD. These findings suggest LOAD and EOAD may have different courses of pathomechanism.
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