Related Experiment Videos
In vitro MR microscopy of the hippocampus in Alzheimer's disease
C T Huesgen1, P C Burger, B J Crain
1Department of Pathology, Duke University, Durham, NC.
Abstract:
We used MR microscopy at 7 tesla to identify the anatomy of the degenerating hippocampus in Alzheimer's disease (AD), which we then correlated with the histopathologic findings in the same specimens. The specimens studied were resected postmortem from 13 patients with confirmed AD and from nine age-matched controls. We imaged the specimens in the coronal plane using either three-dimensional Fourier encoding or single-slice Carr, Purcell, Meiboom, Gill (CPMG) spin echo sequences. On all specimens imaged with the CPMG pulse sequence, we calculated the T2 relaxation times for subfields within the hippocampus. Histologic sections were taken from each specimen and compared with the corresponding MR image. Using histologic boundaries, we quantified the number of neuritic plaques and neurofibrillary tangles in each hippocampal subfield. We measured the area, morphometric characteristics, and width of identifiable signal variant regions on each image and compared these measurements with the histopathologic findings. The mean cross-sectional area of the hippocampus in AD was decreased by 31% compared with the control group. This atrophy was highly correlated with tangle counts within the hippocampus, but not with plaque counts. The width of the gray matter in hippocampal area CA1, as identified by MR, correlated with the total area of the hippocampus. An age-related decrease in the size of a low-signal region that corresponds histologically to input projections comprising part of the perforant pathway was identified. Measurements of the T2 relaxation times of hippocampal subfields showed little regional variability and were not accurate indicators of disease presence or severity (p > 0.05).
Insights
Alzheimer's disease (AD) causes significant hippocampal atrophy, strongly correlating with neurofibrillary tangles but not plaques. Advanced MR microscopy reveals these changes in postmortem brain tissue.
Area of Science:
- Neuroimaging
- Neuropathology
- Alzheimer's Disease Research
Background:
- Alzheimer's disease (AD) is characterized by progressive neurodegeneration, particularly affecting the hippocampus.
- Accurate in vivo or ex vivo assessment of AD-related hippocampal changes is crucial for understanding disease mechanisms.
Purpose of the Study:
- To utilize high-field (7 Tesla) MR microscopy to identify and characterize the anatomical changes in the degenerating hippocampus in AD.
- To correlate MR imaging findings with detailed histopathologic data (neuritic plaques and neurofibrillary tangles) in postmortem human brain specimens.
Main Methods:
- Postmortem hippocampal specimens from 13 AD patients and 9 controls were imaged using 7T MR microscopy (3D Fourier encoding and CPMG spin echo sequences).
- T2 relaxation times were calculated for hippocampal subfields.
- Histologic sections were analyzed to quantify plaque and tangle loads.
- MR imaging measurements (area, morphometrics, signal variations) were compared with histopathology.
Main Results:
- A significant 31% decrease in mean hippocampal cross-sectional area was observed in AD patients compared to controls.
- Hippocampal atrophy strongly correlated with neurofibrillary tangle burden, but not with neuritic plaque counts.
- MR-identified gray matter width in CA1 correlated with overall hippocampal area.
- An age-related decrease in a low-signal region of the perforant pathway was noted.
- T2 relaxation times showed limited regional variability and were not reliable indicators of AD presence or severity.
Conclusions:
- High-field MR microscopy can effectively visualize and quantify hippocampal atrophy in Alzheimer's disease.
- Neurofibrillary tangles, rather than plaques, are the primary correlate of hippocampal volume loss in AD.
- MR imaging metrics, particularly hippocampal volume, show strong correlation with neuropathologic hallmarks of AD.