Hippocampal Atrophy Subtypes of Alzheimer's Disease Using Automatic MRI in a Memory Clinic Cohort: Clinical
Karin Persson1,2, Trine H Edwin1,2, Anne-Brita Knapskog2
1Norwegian National Advisory Unit on Ageing and Health, Vestfold Hospital Trust, Tønsberg, Norway.
Introduction:
One pathological hallmark of Alzheimer's disease (AD) is atrophy of medial temporal brain regions that can be visualized on magnetic resonance imaging (MRI), but not all patients will have atrophy. The aim was to use MRI to categorize patients according to their hippocampal atrophy status and to present prevalence of the subtypes, difference in clinical symptomatology and progression, and factors associated with hippocampal subtypes.
Methods:
We included 215 patients with AD who had been assessed with the clinically available MRI software NeuroQuant (NQ; CorTechs labs/University of California, San Diego, CA, USA). NQ measures the hippocampus volume and calculates a normative percentile. Atrophy was regarded to be present if the percentile was ≤5. Demographics, cognitive measurements, AD phenotypes, apolipoprotein E status, and results from cerebrospinal fluid and amyloid positron emission tomography analyses were included as explanatory variables of the hippocampal subtypes.
Results:
Of all, 60% had no hippocampal atrophy. These patients were younger and less cognitively impaired concerning global measures, memory function, and abstraction but impaired concerning executive, visuospatial, and semantic fluency, and more of them had nonamnestic AD, compared to those with hippocampal atrophy. No difference in progression rate was observed between the two groups. In mild cognitive impairment patients, amyloid pathology was associated with the no hippocampal atrophy group.
Conclusion:
The results have clinical implications. Clinicians should be aware of the large proportion of AD patients presenting without atrophy of the hippocampus as measured with this clinical MRI method in the diagnostic set up and that nonamnestic phenotypes are more common in this group as compared to those with atrophy. Furthermore, the findings are relevant in clinical trials.
Insights
Many Alzheimer's disease (AD) patients lack hippocampal atrophy on MRI scans. These individuals often present with nonamnestic symptoms and may have amyloid pathology, impacting clinical diagnosis and trials.
Area of Science:
- Neurology
- Radiology
- Gerontology
Background:
- Alzheimer's disease (AD) is characterized by medial temporal lobe atrophy, often visualized via MRI.
- However, not all AD patients exhibit this atrophy, suggesting potential subtypes.
- Understanding these subtypes is crucial for accurate diagnosis and treatment.
Purpose of the Study:
- To categorize Alzheimer's disease (AD) patients based on hippocampal atrophy status using MRI.
- To determine the prevalence of these subtypes.
- To analyze differences in clinical symptomatology, progression, and associated factors.
Main Methods:
- Utilized MRI scans from 215 AD patients assessed with NeuroQuant (NQ) software.
- NQ measures hippocampal volume and calculates a normative percentile; atrophy was defined as ≤5 percentile.
- Demographics, cognitive function, AD phenotypes, APOE status, CSF, and amyloid PET data were analyzed.
Main Results:
- 60% of AD patients showed no hippocampal atrophy.
- This group was younger, less globally impaired, but showed deficits in executive function and fluency.
- Nonamnestic AD phenotypes were more prevalent in the no-atrophy group; no difference in progression was observed.
Conclusions:
- A significant proportion of AD patients lack hippocampal atrophy detectable by clinical MRI.
- Clinicians should consider nonamnestic AD phenotypes in patients without atrophy.
- Findings are relevant for diagnostic approaches and clinical trial designs in AD.
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