May 8, 2017Neurology
A study recently reported the Annals of Neurology (2017;81:549-559), was performed to determine clinical and neuropathological outcomes following a clinical diagnosis of mild cognitive impairment (MCI). For the study, data were drawn from a large autopsy series (N=1,337) of individuals followed longitudinally from normal or MCI status to death, derived from 4 Alzheimer Disease (AD) Centers in the United States.
Study participants had a mean follow-up was 7.9 years. Of the 874 individuals ever diagnosed with MCI, final clinical diagnoses were varied: 39.2% died with an MCI diagnosis, 46.8% with a dementia diagnosis, and 13.9% with a diagnosis of intact cognition. The latter group, however, had pathological features resembling those with a final clinical diagnosis of MCI. In terms of non-AD pathologies, both primary age-related tauopathy (p<0.05) and brain arteriolosclerosis pathology (p<0.001) were more severe in MCI than cognitively intact controls. Among the group that remained MCI until death, mixed AD neuropathologic changes (ADNC; >1 comorbid pathology) were more frequent than pure ADNC pathology (55% vs 22%); suspected non-Alzheimer pathology comprised the remaining 22% of cases. A majority (74%) of subjects who died with MCI were without high-level ADNC, Lewy body disease, or hippocampal sclerosis pathologies; this group was enriched in cerebrovascular pathologies. Subjects who died with dementia and were without severe neurodegenerative pathologies tended to have cerebrovascular pathology and carry the MCI diagnosis for a longer interval.
The authors concluded that MCI diagnosis usually was associated with comorbid neuropathologies. However, less than one-quarter of MCI cases showed pure AD at autopsy.