The significance of medial temporal lobe atrophy

Background: Medial temporal lobe atrophy (MTA) is a sensitive radiologic marker for Alzheimer disease (AD) and associated with cognitive impairment. The value of MTA in the oldest old (>85 years old) is largely unknown. Methods: A total of 132 formalin-fixed brains from the Vantaa 85+ community-based study were subjected to postmortem MRI. Visual ratings of MTA were determined in a blinded fashion and compared with neuropathologic findings and clinical assessment (dementia according to Diagnostic and Statistical Manual of Mental Disorders-III-R). Results: A strong relationship was found between MTA scores and Alzheimer pathology (p < 0.001). The previously proposed cutoff MTA score >2 correctly excluded subjects with no or borderline Alzheimer-type pathology (45/48), but was not very sensitive for AD (modified National Institute on Aging-Reagan Institute criteria). MTA scores >2 were also found in subjects with other primary neurodegenerative hippocampal pathology including hippocampal sclerosis, Lewy-related pathology, and argyrophilic grain disease, either alone or in combination with Alzheimer-type pathology. High MTA scores were associated with clinical dementia—in this subgroup, sensitivity was 63% and specificity 69% for AD. Conclusion: Medial temporal lobe atrophy (MTA) on postmortem MRI is sensitive to primary degenerative hippocampal pathology in the very old, but not specific for Alzheimer-type pathology. MTA scores of 2 or less are not frequently associated with dementia. GLOSSARY: AD = Alzheimer disease; AgD = argyrophilic grain disease; CERAD = Consortium to Establish a Registry for Alzheimer’s Disease; DLB = dementia with Lewy bodies; HS = hippocampal sclerosis; L-rP = Lewy-related pathology; MCI = mild cognitive impairment; MTA = medial temporal lobe atrophy.