Patients with mild cognitive impairment (MCI) at risk for dementia who have preserved hippocampal volume are at increased risk for progression to dementia with Lewy bodies (DLB) rather than Alzheimer’s disease (AD), according to a study published in Neurology.
“Identifying patients with [MCI] who are at risk for [DLB] is critical for early interventions,” the authors wrote. “Better response to cholinesterase inhibitors and neuroleptic sensitivity may need to be addressed in patients with MCI who are likely to progress to probable DLB.”
Hippocampal volumes on magnetic resonance imaging (MRI) are lower with increasing phospho-tau burden. However, hippocampal volumes tend to be preserved regardless of α-synuclein burden. In addition, patients with DLB with little to no AD pathology on autopsy have preserved hippocampal volumes on MRI.
Kejal Kantarci, MD, MS, of Mayo Clinic, Rochester and colleagues investigated whether preserved hippocampal volumes on MRI in patients with MCI predicted progression to probable DLB vs AD dementia. Data was obtained from patients with MCI enrolled in an MRI study at the Mayo Clinic Alzheimer’s Disease Research Center.
Of 160 patients, 20 (13%) progressed to probable DLB and 61 (38%) progressed to AD. Half of the patients who developed probable DLB had nonamnestic MCI at baseline, while the majority (69%) of patients who developed AD had amnestic MCI. The amnestic subtype of MCI has been shown to be associated with AD, while the nonamnestic subtype may indicate a higher risk of progressing to DLB.
Baseline hippocampal volumes were smaller in patients who progressed to AD than in patients who progressed to probable DLB (P <.001). A greater proportion of probable DLB progressors had normal hippocampal volumes than AD progressors (85% vs 39%).
Compared with patients with hippocampal atrophy, patients with normal hippocampal volumes were at higher risk for developing probable DLB (estimated hazard ratio [HR], 4.22; P = .01) and at lower risk for developing AD (estimated HR, 0.56; P = .02).
“Preserved hippocampal volumes are associated with increased risk of probable DLB competing with AD dementia in patients with MCI. Preservation of [hippocampal volume] may support prodromal DLB over AD, particularly in patients with MCI with nonamnestic features,” the authors concluded.
Kantarci K, Lesnick T, Ferman TJ, et al. Hippocampal volumes predict risk of dementia with Lewy bodies in mild cognitive impairment. Neurology. 2016 Nov 2; doi:10.1212/WNL.0000000000003371.