Prodromal characteristics of Dementia with Lewy Bodies: baseline results of the Memento nationwide cohort


 Background: Isolated subjective cognitive impairment (SCI) and mild neurocognitive impairment (MCI) are prodromal phase of dementia with Lewy bodies (DLB). Memento is a nationwide study of patients with SCI and MCI with clinic, neuropsychology, biology and brain imaging data. We aimed to compare SCI and MCI patients with symptoms of prodromal DLB to others in this study at baseline. Methods: Participants of the French Memento cohort study recruited for either SCI or MCI. Among them, 892 were included in the Lewy sub-study, designed to search specifically for symptoms of DLB. Probable prodromal DLB group (pro-DLB) was done using a two-criteria cut-off score among the four core clinical features of DLB. This Pro-DLB group was compared to two other groups at baseline: one without any core symptoms (NS group), and the one with one core symptom (1S group). A comprehensive cognitive battery, questionnaires on behavior, neurovegetative and neurosensory symptoms, brain 3D volumetric MRI, CSF, FDG PET and amyloid PET were done.Results: The Pro-DLB group comprised 148 patients (16.6%). This group showed more multidomain (59.8%) MCI with slower processing speed and a higher proportion of patients with depression, anxiety, apathy, constipation, rhinorrhea, sicca syndrome, and photophobia. The Pro-DLB group had isolated lower P-Tau and on brain MRI widening of sulci including fronto-insular, occipital, and olfactory sulci (FDR corrected). Conclusions: Patients with symptoms of prodromal DLB are cognitively slower, with more behavioral disorders, autonomic symptoms, and photophobia. Biomarkers confirmed the non-Alzheimer profile. The occipital, fronto-insular, and olfactory bulb involvement on brain MRI was consistent with symptoms and known neuropathology. The next step will be to study the clinical, biological, and imaging evolution of these patients.Trial registration: Clinicaltrials.gov, NCT01926249 .


Introduction
The description of the prodromal phase of dementia with Lewy bodies (pro-DLB) is just emerging, in contrast to the description of the prodromal phase of Alzheimer's disease [1]. There is nevertheless a consensus on the key symptoms of pro-DLB, combining rapid eye movement (REM) sleep behavior disorders (RBD), cognitive and alertness uctuations, hallucinations, and parkinsonism [1]. The presence of 2 of the 4 key symptoms with mild cognitive impairment (MCI) indicates probable prodromal pro-DLB [1]. Beyond the key symptoms of the disease, other symptoms have been described as prodromal, such as autonomic dysfunction symptoms, including constipation or erectile dysfunction [2,3] or behavioral symptoms such as depression [4,5]. Delirium could also occur in the prodromal phase of DLB [6]. Prospective cohorts are needed in the context of pro-DLB to better determine the different characteristics of this disease [5,7,8].
Previous studies have described the cognitive pattern of pro-DLB. The MCI pattern was amnestic multidomain in 33% to 50% of patients, non-amnestic multidomain in 24% to 39%, and non-amnestic unidomain in 27% to 49% [9][10][11]. Even if the cognitive pro le in pro-DLB highlights the fact that cognitive di culties are diffuse, attentional/executive and visuo-constructive tests appear to be the best predictor of DLB [9,11]. Few studies exist on cerebrospinal uid (CSF) in pro-DLB: the analysis of Tau, P-Tau and Abeta-42 is normal in most cases [5,12]. Reduced insular cortical thinning [13] and a decrease in gray matter concentration [14] have been demonstrated in pro-DLB patients using image processing on brain MRI T1 sequences. Pro-DLB patients have antero-superior insula atrophy when compared to healthy controls [13], and more preserved hippocampi when compared to pro-AD patients [1]. FP-CIT dopaminergic SPECT is a recognized biomarker of DLB. However, in the prodromal phase, this biomarker is not su ciently sensitive: the value of FP-CIT in distinguishing probable pro-DLB from pro-AD is 61% for sensitivity and 89% for speci city [15].
In a large prospective cohort of patients attending memory clinics presenting either subjective cognitive impairment (SCI) and MCI patients, we undertook an ancillary study aiming to detect symptoms of DLB in a longitudinal framework. The aim of the present study was to compare MCI and SCI patients with symptoms of prodromal DLB to others at the baseline for different characteristics: clinical, neuropsychological, cerebrospinal uid (CSF), brain MRI, 18-Fluoro-Desoxy-Glucose (FDG) PET, and amyloid PET one.

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The Memento cohort is a clinic-based study aimed to investigate the evolution of a large variety of cognitive symptoms and subjective complaints over time, without any speci c a priori hypothesis regarding the relationship with incident dementia.

Study Recruitment
Eligible adult participants for the Memento study, and therefore for Lewy Memento sub-study, had to undergo at baseline all clinical examinations, brain MRI and blood sampling. All participants had to have visual and auditory acuity compatible with neuropsychological testing and be a liated to a health insurance scheme. The participants were screened for either MCI or SCI and they were recruited consecutively. MCI was de ned as 1) performing worse than one standard deviation from the mean (compared to age and education norms) in one or more cognitive domains (memory, language, praxis, attention, executive functions, speed processing, visual spatial abilities), this deviation being identi ed for the rst time through cognitive tests performed recently, i.e. less than 6 months before the screening phase, and 2) having a Clinical Dementia Rating scale score ≤0.5 and being non-demented. The battery of neuropsychological tests and detailed aspects of the inclusion/exclusion criteria were described previously for the Memento cohort [16].

Standard Protocol Approvals, Registrations, and Patient Consents
All participants provided written informed consent for the Memento cohort and the Lewy Memento sub-study, and the protocol was approved by the ethics committee (Comité de Protection des Personnes Sud-Ouest et Outre Mer III). The protocol is registered in ClinicalTrials.gov (Identi er: NCT01926249, https://clinicaltrials.gov/ct2/show/NCT01926249).

Study Examinations
The baseline data collected at the memory clinic were described previously [16]. The Lewy Memento sub-study included three additional sections added to the basic Memento package. The rst section focused on key symptoms of DLB: features of parkinsonism were evaluated using the Uni ed Parkinson's Disease Rating Scale (UPDRS, part III), including akinesia, amimia and rigidity (rated from 0 [no symptoms] to 4 [serious symptoms]) and falls. Fluctuations were assessed with the Mayo Clinic Fluctuations Scale [17] and the Newcastle-upon-Tyne Clinician Assessment of Fluctuation scale (CAF) [18]. The Hallucinations Parkinson's disease-associated psychotic symptoms questionnaire was used to evaluate the presence of hallucinations [19]. RBD was evaluated using a questionnaire based on the article by Gjerstad et al., 2008 [20] simpli ed into two questions for the patient and the caregiver, one concerning movements during sleep and the other concerning vivid dreams and nightmares. The second section focused on autonomic disorders and sensorineural symptoms and included: 5 minutes lying and standing blood pressure at 1, 2, and 3 minutes with a heart rate measurement; questionnaire on dry eyes, mouth, and nose, rhinorrhea, lacrimation, and salivation, constipation, libido and erectile dysfunction and photophobia. Each item was rated from 'no symptom = 0' to 'daily symptom = 2'.
The third section focused on neuropsychological aspects with the following sub-tests using the Visual Object and Space Perception Battery (VOSP) allowing the evaluation of visuo-perceptual and visuo-spatial abilities: "Incomplete Letters"; "Position Discrimination" and "Number Location". The DSM IV MINI500 test was used for the diagnosis of major depression.

De nition of the Groups
The pro-DLB group included patients with SCI or MCI, and with at least two of the core features of DLB ( uctuations, RBD, hallucinations, and parkinsonism) during the rst visit. The one symptom group (1S) included patients with only one key DLB symptom, and the no symptom group (NS) patients without any core features of DLB. Each symptom was considered to be present as follows: for RBD if the score was 2/2; for hallucinations, if sensation of passage, sensation of presence, illusions, non-visual and visual hallucinations and delusion were detected; for uctuations, if a cut-off score of 2/4 or over on the Mayo Clinic Fluctuations Scale was recorded (caregiver or patients); for parkinsonism, if one criterion among akinesia, rigidity, amimia, or falls was present, as described in the McKeith et al., criteria [1].

Imaging and Cerebrospinal Fluid
Neuroimaging acquisitions (brain MRI, 18F-FDG PET, amyloid PET) were coordinated by the Center for Automated Treatment of Images (CATI), a platform dedicated to multicenter neuroimaging [21]. The MRI and PET protocols as well as standardization and quality control procedures were described previously [16]. In our sample, brain MRI was available for 98.0% of participants (88% on a 3.0 T MRI scan, 1.5 T otherwise). FDG PET, amyloid-PET and lumbar puncture were optional and were performed in respectively 68.6%, 30.8%, and 19.5% of participants. Detailed CSF and blood analysis aspects were described previously [16]. Apolipoprotein E (APOE) genotypes were determined by KBiosciences (Hoddesdon, the UK).

Data and Statistics
The data presented are those obtained at the rst Lewy Memento visit. The cognitive de cit categories (isolated SCI or MCI staging according to Petersen's criteria [22]) were based on the results of the neuropsychological battery. As previously described [23], we focused on 4 items of the Instrumental Activities of Daily Living (IADL) questionnaire (ability to use the telephone, mode of transport, responsibility for his own medication, and ability to handle nances) as a proxy of dependence. Blood pressure was measured in three steps: after 5 min of rest in the supine position and after 1 min and 3 min in the standing position. Hypotension was de ned as a decrease of at least 20 mmHg between the supine position and the standing position for systolic blood pressure, and 10 mmHg for diastolic blood pressure. We de ned pathological levels of CSF biomarkers as follows: Abeta42: lower than 750 pg/mL, P-Tau: higher than 60 pg/mL, Total Tau: higher than 350 pg/mL and Abeta42/40: lower than 0.065 [24]. Brain MRI biomarkers of interest were hippocampal volume (mean of both hemispheres), obtained using the SACHA software [25], brain parenchymal fraction (BPF) computed from SPM8 software, and total white matter hyperintensities (WMH) using the WHASA software [26]. Mean and regional cortical thicknesses by hemisphere were obtained using FreeSurfer 5.3. Cortical sulcus modi cations were studied: the average distance between the two walls of the pial surface was computed. This distance provides an estimation of the local atrophy leading the fold to open up [27]. Mean and regional FDG-PET singular uptake value ratios (SUVRs) were normalized to the cerebellum [28]. The amyloid PET ( orbetapir or utemetamol) pipeline of analysis was described previously [29].
Data are presented with numbers and percentages for qualitative variables, and with medians and rst and third quartile for qualitative variables. Comparisons across subgroups were done using Fisher's Chi-square tests or Kruskal-Wallis tests, as appropriate.
The associations between groups and biomarkers were assessed using logistic regressions for dichotomous variables (i.e. pathological level of Abeta-42, Total Tau, P-Tau and amyloid PET status) and linear regressions for MRI and FDG PET measures. Associations were adjusted for age, gender, education, and APOE. For brain MRI markers, additional adjustment covariates were the type of MRI (manufacturer and magnet size), and intracranial volume (except for BPF). Comparisons were considered statistically signi cant for P-values below α=0.05. For FDG PET and MRI, when analyses were done at a regional level (a ROI or a sulcus), we used the false discovery rate (FDR) method. Analyses were performed using SAS version 9.4 software (SAS Institute, Cary, NC).

Presence of Key Symptoms
The demographic characteristics and cognitive and behavioral ndings for the three groups are provided in Table 1. Within the Pro-DLB group, 103 (69.6%) patients had two core features of DLB, 36 (24.3%) had three core features, and 9 (6.1%) had four core features. The most frequent symptoms of hallucinations in the Pro-DLB group were passage sensation (26.7% of patients), presence sensation (24.3%), and well-formed visual hallucinations (17.6%). For parkinsonism, the most frequent symptom in this group was amimia, found in 37.2% of patients. On the Mayo Clinic Fluctuations Scale, the two items most frequently present in the Pro-DLB group were drowsiness (53.4% of patients) and cognitive uctuations expressed through changes in thought or language (32.0%). The CAF score was abnormal in 21.7% of patients in the Pro-DLB group, 7.6% of patients in the 1S group, and 2% in the NS group. Table 1 Characteristics of the groups. Group with at least 2 DLB core features (pro-DLB), group with only one DLB core feature (1S group), and group without any core DLB feature (NS group).

Autonomic and Sensorineural Symptoms
Autonomic symptoms were more frequent in the Pro-DLB group than in the other two groups ( Table 2). The most frequent in the Pro-DLB group were sicca syndrome (especially dry mouth) (43.8%), constipation (34.7%), sexual dysfunction (including decreased libido or erectile dysfunction, 32.8%), and rhinorrhea (27.9%). Photophobia was quite frequent in this group (36.3%). There was no difference in the cardiovascular metrics across groups. Table 2 Autonomic and sensorineural symptoms in the prodromal dementia with Lewy bodies patients' group (pro-DLB group), compared to the group with only one core feature (1S), and the group without any DLB core feature (NS)

Cognitive, Functional and Behavioral Results
Overall, our results depict a more impaired cognitive, functional, and behavioral pro le in the Pro-DLB group than in the other two groups ( Table 1). The median MMSE was slightly lower in the pro-DLB group (P=.02). The cognitive complaint was more severe in the Pro-DLB group, whether at the memory (P=.0021) or attention level (P<.0001). No cognitive impairment was detected (i.e. SCI pro le) in 19.7% of Pro-DLB, 25.6% of 1S and 27.4% of NS patients. The cognitive pro le in the Pro-DLB group was for most patients multidomain; semantic uency, Trail Making Test A (TMTA), fragmented letters and position discrimination of the Visual Object and Space Perception (VOSP) battery were more de cient in the Pro-DLB group than in the other two groups ( Table 1).
The scores on the functional scales were also worse in the Pro-DLB group: the CDR 0.5 was more frequent (60.4%) than in the 1S group (47.6%) or the NS group (48.6%) (P=.037); a restriction of IADL was found in 29.1% of patients in the prodromal group, compared to 18.5% in the 1S group, and 15.8% in the NS group (P=.0031).
On the NPI-C, when compared to the other two groups, a higher proportion of patients in the pro-DLB group presented symptoms of anxiety (P=.0033), apathy (P<.0001), and depression (P=.0032). According to the scores on the questionnaire for depression (MINI 500), 26.2% of the Pro-DLB group could be considered to have major depression (P<.0001).

Genetic, Alzheimer's Biomarkers and FDG PET Results
The acceptance rates were comparable across the groups for all examinations, but lower in the Pro-DLB group for amyloid PET (21%, P=.04). In terms of genetic aspects, no difference was found for ApoE4 status (P=.53; Table 1). The CSF biomarker analysis showed that the pro-DLB group had lower P-Tau (50.6 versus 57.1 pg/ml for the NS group; P=.031) but this was not signi cant after adjustment ( Figure 1, Table 3, P=.15). The proportion of patients with abnormal CSF biomarkers was signi cantly higher for P-Tau and Tau in the NS group ( Figure 2). For FDG PET and amyloid PET, local and global analysis did not nd any differences between the groups.

MRI Results
Among 892 patients, 874 (98%, comparable across groups) patients had a brain MRI. No difference was found for hippocampal volume (P=.61), total intracranial volume (P=.41), mean cortical thickness (P=.36), ROI cortical thickness (P=.26), or white matter hypersignals volume (P=.094) ( Table 3). The BPF was signi cantly different across groups (P=.015, Table 3), but the decrease was observed only in the 1S group (P=.004). Focal cortical thickness analysis found a lower cortical thickness in the left fusiform (P=.0088) and right superior temporal (P=.024) gyri in the Pro-DLB group, but not if FDR-corrected. Sulcus-based brain MRI analysis, FDR-corrected, showed fold opening of different sulci combining the fronto-insular, occipital, temporal and olfactory regions in the 1S and Pro-DLB groups ( Figure 3). Table 3 Associations between the three groups of patients and biomarkers. Prodromal dementia with Lewy bodies group (pro-DLB), group with one core symptom (1S group), group without any core DLB symptoms (NS group)

Discussion
We describe here a large nationwide study that speci cally addressed the prodromal phase of dementia with Lewy bodies, at the baseline of the study. Clinically, patients in the Pro-DLB group were more likely to have symptoms of RBD and hallucinations, particularly passage and presence hallucinations. Among uctuations, drowsiness and cognitive uctuations were frequent in the Pro-DLB group. The most frequent symptom of parkinsonism in the Pro-DLB group was amimia. Sicca syndrome, constipation, sexual dysfunction, and rhinorrhea were the most frequent autonomic symptoms and photophobia was rather frequent, in the Pro-DLB group when compared to 1S and NS groups. Pro-DLB patients usually had a multidomain cognitive pro le, with attentional and memory complaints. Concerning behavior, the Pro-DLB group had an over-representation of depression and anxiety. Cross-sectional brain imaging analysis showed a global decrease in brain volume (BPF) in the 1S group and a fold opening of occipital, olfactory, temporal, and fronto-insular regions in the 1S and pro-DLB groups. These results might suggest that a weak and localized atrophy process could be in progress.

Clinical Issues
The proportion of patients with probable pro-DLB in this study (16.6%) is consistent with the proportion of DLB in neuropathological studies, where it is between 4% and 24.7% of demented people [30]. Seventy-ve percent of patients of the Pro-DLB group in our study presented RBD, the same proportion as in autopsy con rmed DLB demented patients [31]. Asking about hallucinations at an early stage makes it possible to have a description of them not by relatives but by the patients themselves. The most frequent symptoms were passage (26.7% of patients) and presence (24.3%) hallucinations, which is consistent with a previous study on MCI patients [32]. Globally, 63.5% of the pro-DLB group had hallucinations and 31% had at least two types of hallucinations. Pro-DLB patients had delusion in 12.8%. Delusion was previously described as a way of entering in the disease [33].
We found symptoms of anxiety and depression respectively in 61% and 49.2% and a diagnosis of major depression in 26.2%. In this connection, a Japanese study reported that 14% of people aged over 50 years hospitalized for depression had prodromal or demented DLB [4]. For uctuations, more than half of the Pro-DLB group reported drowsiness, before cognitive uctuations. The scales for uctuations detected uctuations in the pro-DLB group in 21.7% of patients with CAF and 42.6% with the Mayo Clinic Fluctuations Scale. Using the latter scale, such uctuations were previously reported in 76% of pro-DLB cases [34]. Parkinsonism was very discreet in our pro-DLB patients. A decrease in facial expression was the most common motor symptom in our study. This is consistent with a study of 26 prodromal DLB patients that found this to be an early symptom [35].
Autonomic dysfunction symptoms increased in parallel with DLB symptoms. Sicca syndrome was the autonomic dysfunction symptom most frequently described by patients, twice as many as in the NS group. To our best knowledge, this has never been described before in prodromal DLB or even in DLB. Sicca syndrome is a key symptom of primary Sjogren's syndrome during which dementia could appear [36]. In contrast, facial secretion symptoms, such as rhinorrhea, lacrimation and salivation, were also frequently found in our study. In prodromal DLB increased saliva was previously described [37,38] unlike rhinorrhea and lacrimation.
The frequency of constipation is rather heterogeneous depending on the studies and countries: a study in the general population in France previously found a frequency of 22.4% [39]. In the Pro-DLB group, we found a frequency of 34.7% against 15% in the NS group. This symptom has been described as occurring 9.3 years before the dementia phase of DLB [2]. Erectile dysfunction is an early symptom of DLB [35]. In our study, the frequency of sexual dysfunction (including erectile dysfunction but also a decrease or abolition of libido) in Pro-DLB group was 32.8%. In practice, autonomic disorders should therefore be systematically looked for in a context of mild cognitive disorder, particularly in the case of sicca syndrome, constipation, and rhinorrhea. The description of photophobia in Parkinson's disease was recently done but not in DLB [40]. In our study, the higher the number of core symptoms of DLB present, the higher the frequency of photophobia, with a maximum of 36.3% in the Pro-DLB group.
Globally, the 1S group could represent a possible pro-DLB group and, interestingly, the proportion of usual symptoms of DLB was intermediate between the NS group and the probable pro-DLB group: this was the case for autonomic, sensorineural, and behavioral symptoms. The 1S group therefore could correspond to an intermediate phase.

Cognitive Pro le
The cognitive pro le of the Pro-DLB group was more multidomain, non-amnestic and amnestic, and less SCI, than the NS and 1S groups. This is consistent with previous studies [9,34,41]. The main characteristics found in the Pro-DLB group was low speed processing, low semantic uency and visuoperceptual and visuo-spatial impairment (Table 1).

Biomarkers
For CSF, the proportion of patients with abnormal Alzheimer's biomarkers was higher in the NS group than in the other two groups but no difference was found for ABeta42 and ABeta42/40, and no difference was found for amyloid PET. These results are consistent with a previous study [12], and argues in favor of the absence of tangles in the Pro-DLB group. However, the number of subjects tested was low, representing less than one third of the cohort.
Brain MRI and FDG PET At the global and focal level, there was no difference between groups for FDG PET. On the contrary, brain MRI showed a smaller BPF in the 1S group. Moreover, the widening of sulci including fronto-insular sulci, occipital, temporo-occipital sulci and olfactory sulci (FDR corrected) in the 1S and pro-DLB groups is of high interest. First, the modi cations in the olfactory sulci are highly consistent with neuropathology, where patients even with incidental Lewy bodies had these lesions in the olfactory bulbs [42]. Second, the fronto-insular involvement in the prodromal phase of DLB has been demonstrated previously, particularly in the anterior part of the insula [13,43]. Third, the temporo-occipital involvement is of interest regarding hallucinations since these regions are in the ventral stream of the visual pathway (the "what" pathway) devoted to visual gnosis.

Limitations
Even if we used different biomarkers, including CSF, amyloid PET, FDG PET and MRI, no speci c biomarker for DLB, such as FP-CIT dopaminergic imaging, was used in our study [15]. The questionnaire used for RBD might be too sensitive; however, the high proportion of RBD in our pro-DLB cohort is quite consistent with previous studies [35,44].

Conclusion
This study provides a description of a nationwide cohort of pro-DLB patients at the baseline of the study. We have reported new, frequently occurring symptoms in this group of patients: sicca syndrome, photophobia, lacrimation, and rhinorrhea. The cognitive pro le, biomarkers, and PET results are consistent with the literature. Changes in brain sulci, particularly olfactory and insula sulci, are also consistent with both neuropathological and other cohort data. The next step will be to investigate the clinical, biological, and imaging evolution of these patients.

Consent for publication
Not applicable.

Consortia
On behalf of the Memento study group CSF, FDG PET and amyloid PET analysis of the three groups: pro-DLB group (2 or more core symptoms of DLB), one symptom group (one core symptom), and no symptom group (no core symptom)