Longitudinal evolution of cortical thickness signature reflecting Lewy body dementia in isolated REM sleep behavior disorder:a prospective cohort study

Background The isolated rapid-eye-movement sleep behavior disorder(iRBD)is a prodromal condition of Lewy body disease including Parkinson’s disease and dementia with Lewy bodies(DLB).We aim to investigate the longitudinal evolution of DLB-related cortical thickness signature in a prospective iRBD cohort and evaluate the possible predictive value of the cortical signature index in predicting dementia-first phenoconversion in individuals with iRBD.Methods We enrolled 22 DLB patients,44 healthy controls,and 50 video polysomnography-proven iRBD patients.Participants underwent 3-T magnetic resonance imaging(MRI)and clinical/neuropsychological evaluations.We characterized DLB-related whole-brain cortical thickness spatial covariance pattern(DLB-pattern)using scaled subprofile model of principal components analysis that best differentiated DLB patients from age-matched controls.We analyzed clinical and neuropsychological correlates of the DLB-pattern expression scores and the mean values of the whole-brain cortical thickness in DLB and iRBD patients.With repeated MRI data during the follow-up in our prospective iRBD cohort,we investigated the longitudinal evolution of the cortical thickness signature toward Lewy body dementia.Finally,we analyzed the potential predictive value of cortical thickness signature as a biomarker of phenoconversion in iRBD cohort.Results The DLB-pattern was characterized by thinning of the temporal,orbitofrontal,and insular cortices and relative preservation of the precentral and inferior parietal cortices.The DLB-pattern expression scores correlated with attentional and frontal executive dysfunction(Trail Making Test-A and B:R=−0.55,P=0.024 and R=−0.56,P=0.036,respectively)as well as visuospatial impairment(Rey-figure copy test:R=−0.54,P=0.0047).The longitudinal trajectory of DLB-pattern revealed an increasing pattern above the cut-off in the dementia-first phenoconverters(Pearson’s correlation,R=0.74,P=6.8×10−4)but no significant change in parkinsonism-first phenoconverters(R=0.0063,P=0.98).The mean value of the whole-brain cortical thickness predicted phenoconversion in iRBD patients with hazard ratio of 9.33[1.16-74.12].The increase in DLB-pattern expression score discriminated dementia-first from parkinsonism-first phenoconversions with 88.2%accuracy.Conclusion Cortical thickness signature can effectively reflect the longitudinal evolution of Lewy body dementia in the iRBD population.Replication studies would further validate the utility of this imaging marker in iRBD.