Assessing Nigrostriatal Dopaminergic Pathways via 123I-FP-CIT SPECT in Dementia With Lewy Bodies in a Psychiatric Patient Cohort

Clinical presentations and diagnostic application of proposed biomarkers in psychiatric-onset prodromal dementia with Lewy bodies

Research criteria for the diagnosis of prodromal dementia with Lewy bodies (DLB) include three clinical subtypes: mild cognitive impairment with Lewy bodies (MCI-LB), delirium-onset prodromal DLB, and psychiatric-onset prodromal DLB. Late-onset psychiatric manifestations are at a higher risk of developing dementia, but its relation to prodromal DLB remains unclear. In addition to the risk of severe antipsychotic hypersensitivity reactions, accurate discrimination from non-DLB cases is important due to the potential differences in management and prognosis. This article aims to review a rapidly evolving psychiatric topic and outline clinical pictures of psychiatric-onset prodromal DLB, including the proposed biomarker findings of MCI-LB: polysomnography-confirmed rapid eye movement sleep behaviour disorder, cardiac [123I]metaiodobenzylguanidine scintigraphy, and striatal dopamine transporter imaging. We first reviewed clinical pictures of patients with autopsy-confirmed DLB. Regarding clinical reports, we focused on the patients who predominantly presented with psychiatric manifestations and subsequently developed DLB. Thereafter, we reviewed clinical studies regarding the diagnostic applications of the proposed biomarkers to patients with late-onset psychiatric disorders. Clinical presentations were mainly late-onset depression and psychosis; however, other clinical manifestations were also reported. Psychotropic medications before a DLB diagnosis may cause extrapyramidal signs, and potentially influences the proposed biomarker findings. These risks complicate clinical manifestation interpretation during the management of psychiatric symptoms. Longitudinal follow-up studies with standardised evaluations until conversion to DLB are needed to investigate the temporal trajectories of core features and proposed biomarker findings. In patients with late-onset psychiatric disorders, identification of patients with psychiatric-onset prodromal DLB provides the opportunity to better understanding the distinct prognostic subgroup that is at great risk of incident dementia. Advances in the establishment of direct biomarkers for the detection of pathological α-synuclein may encourage reorganising the phenotypic variability of prodromal DLB.

Mild cognitive impairment in dementia with Lewy bodies: an update and outlook

Dementia with Lewy bodies (DLB), the second most common degenerative neurocognitive disorder after Alzheimer disease (AD), is frequently preceded by a period of mild cognitive impairment (MCI), in which cognitive decline is associated with impairment of executive functions/attention, visuospatial deficits, or other cognitive domains and a variety of noncognitive and neuropsychiatric symptoms, many of which are similar but less severe than in prodromal AD. While 36-38% remain in the MCI state, at least the same will convert to dementia. Biomarkers are slowing of the EEG rhythms, atrophy of hippocampus and nucleus basalis of Meynert, temporoparietal hypoperfusion, signs of degeneration of the nigrostriatal dopaminergic, cholinergic and other neurotransmitter systems, and inflammation. Functional neuroimaging studies revealed disturbed connectivity of frontal and limbic networks associated with attention and cognitive controls, dopaminergic and cholinergic circuits manifested prior to overt brain atrophy. Sparse neuropathological data showed varying Lewy body and AD-related stages associated with atrophy of entorhinal, hippocampal, and mediotemporal cortices. Putative pathomechanisms of MCI are degeneration of limbic, dopaminergic, and cholinergic systems with Lewy pathology affecting specific neuroanatomical pathways associated with progressing AD-related lesions, but many pathobiological mechanisms involved in the development of MCI in LBD remain to be elucidated as a basis for early diagnosis and future adequate treatment modalities to prevent progression of this debilitating disorder.

Psychiatric onset of prodromal dementia with Lewy bodies: Current insights into neuroimaging tools

PURPOSE

Our article is dedicated to describing the state-of-the-art in imaging techniques for assessing prodromal dementia with Lewy bodies (pro-DLB) with a psychiatric-onset.

MATERIALS AND METHODS

Imaging biomarker techniques are discussed.

RESULTS

(123)-I-2-ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl) nortropane single photon emission computed tomography (123I-FP-CIT SPECT) seems to be a promising method as it reveals abnormalities in pro-DLB with a psychiatric-onset. New potential biomarkers can be revealed via novel techniques, such as manual segmentation in magnetic resonance imaging (MRI), which helps detect atrophy of the substantia innominata in pro-DLB with a psychiatric-onset as opposed to an onset with mild cognitive impairment (MCI). FDG-PET can also help us distinguish patients with mixed pro-DLB from those pro-DLB patients with a psychiatric-onset or MCI-onset. Changes in large-scale networks in the posterior standard mode and in attentional networks could be early signs in resting-state functional MRI to characterise pro-DLB.

CONCLUSIONS

In conclusion, there is a wide range of techniques that need to be explored in large-scale studies and are of promising value in understanding pro-DLB with a psychiatric-onset.

Contribution of amyloid and putative Lewy body pathologies in neuropsychiatric symptoms

OBJECTIVES

Neuropsychiatric symptom could be useful for detecting patients with prodromal dementia. Similarities and differences in the NPSs between preclinical/prodromal Alzheimer's disease (AD) and prodromal Parkinson's disease dementia (PDD)/Dementia with Lewy bodies (DLB) may exist. This study aimed to compare the NPSs between preclinical/prodromal AD and prodromal PDD/DLB.

METHODS

One hundred and three participants without dementia aged ≥50 years were included in this study. The mild behavioral impairment (MBI) total score and the MBI scores for each domain were calculated using the neuropsychiatric inventory questionnaire score. Participants were divided into five groups based on the clinical diagnosis by neurologists or psychiatrists in each institution based on the results of the amyloid positron emission tomography and dopamine transporter single photon emission computed tomography (DAT-SPECT): Group 1: amyloid-positive and abnormal DAT-SPECT, Group 2: amyloid-negative and abnormal DAT-SPECT, Group 3: amyloid-positive and normal DAT-SPECT, Group 4: mild cognitive impairment unlikely due to AD with normal DAT-SPECT, and Group 5: cognitively normal with amyloid-negative and normal DAT-SPECT.

RESULTS

The MBI abnormal perception or thought content scores were significantly higher in Group 1 than Group 5 (Bonferroni-corrected p = 0.012). The MBI total score (Bonferroni-corrected p = 0.011) and MBI impulse dyscontrol score (Bonferroni-corrected p = 0.033) in Group 4 were significantly higher than those in Group 5.

CONCLUSION

The presence of both amyloid and putative Lewy body pathologies may be associated with psychotic symptoms.

The diagnostic performance of functional dopaminergic scintigraphic imaging in the diagnosis of dementia with Lewy bodies: an updated systematic review

INTRODUCTION

Dopaminergic scintigraphic imaging is a cornerstone to support the diagnosis in dementia with Lewy bodies. To clarify the current state of knowledge on this imaging modality and its impact on clinical diagnosis, we performed an updated systematic review of the literature.

METHODS

This systematic review was carried out according to PRISMA guidelines. A comprehensive computer literature search of PubMed/MEDLINE, EMBASE, and Cochrane Library databases for studies published through June 2022 was performed using the following search algorithm: (a) "Lewy body" [TI] OR "Lewy bodies" [TI] and (b) ("DaTscan" OR "ioflupane" OR "123ip" OR "123?ip" OR "123 ip" OR "123i-FP-CIT" OR "FPCIT" OR "FP-CIT" OR "beta?CIT" OR "beta CIT" OR "CIT?SPECT" OR "CIT SPECT" OR "Dat?scan*" OR "dat scan*" OR "dat?spect*" OR "SPECT"). Risk of bias and applicability concerns of the studies were evaluated using the QUADAS-2 tool.

RESULTS

We performed a qualitative analysis of 59 studies. Of the 59 studies, 19 (32%) addressed the diagnostic performance of dopamine transporter imaging, 15 (25%) assessed the identification of dementia with Lewy bodies in the spectrum of Lewy body disease and 18 (31%) investigated the role of functional dopaminergic imaging in distinguishing dementia with Lewy bodies from other dementias. Dopamine transporter loss was correlated with clinical outcomes in 19 studies (32%) and with other functional imaging modalities in 15 studies (25%). Heterogeneous technical aspects were found among the studies through the use of various radioligands, the more prevalent being the [123I]N‑ω‑fluoropropyl‑2β‑carbomethoxy‑3β‑(4‑iodophenyl) nortropane (123I-FP-CIT) in 54 studies (91.5%). Image analysis used visual analysis (9 studies, 15%), semi-quantitative analysis (29 studies, 49%), or a combination of both (16 studies, 27%).

CONCLUSION

Our systematic review confirms the major role of dopaminergic scintigraphic imaging in the assessment of dementia with Lewy bodies. Early diagnosis could be facilitated by identifying the prodromes of dementia with Lewy bodies using dopaminergic scintigraphic imaging coupled with emphasis on clinical neuropsychiatric symptoms. Most published studies use a semi-quantitative analytical assessment of tracer uptake, while there are no studies using quantitative analytical methods to measure dopamine transporter loss. The superiority of a purely quantitative approach to assess dopaminergic transmission more accurately needs to be further clarified.

New Insights into Potential Biomarkers in Patients with Mild Cognitive Impairment Occurring in the Prodromal Stage of Dementia with Lewy Bodies

BACKGROUND

Prodromal dementia with Lewy bodies (DLB) can emerge with the onset of mild cognitive impairment (MCI). Standard biomarkers can help identify such patients to improve therapy and treatment strategies. Our review aims to describe the latest evidence on promising biomarkers in prodromal DLB with MCI onset (MCI-LB).

METHODS

We selected articles on different biomarkers in MCI-LB from PubMed and conducted a narrative review.

RESULTS

We identified potentially promising clinical biomarkers, e.g., (1) assessing autonomic symptoms specifically, (2) describing the cognitive profile in several subdomains including executive and visual functions, and (3) measuring the speed of speech. In addition, we describe the measurement of seeding amplification assays of alpha-synuclein in cerebrospinal fluid as a relevant biomarker for MCI-LB. Electroencephalographic markers, as in calculating the theta/beta ratio or intermittent delta activity, or analyzing peak frequency in electroencephalography-methods also potentially useful once they have been validated in large patient cohorts. The 18F fluorodesoxyglucose positron emission tomography (FDG-PET) technique is also discussed to investigate metabolic signatures, as well as a specific magnetic resonance imaging (MRI) technique such as for the volumetric region of interest analysis.

CONCLUSIONS

These biomarker results suggest that MCI-LB is a promising field for the use of biomarkers other than established ones to diagnose early prodromal DLB. Further large-scale studies are needed to better evaluate and subsequently use these promising biomarkers in prodromal DLB.

Neural basis of impaired narrative discourse comprehension in prodromal and mild dementia with lewy bodies

Narrative discourse (ND) comprehension is a complex task that implies not only linguistic abilities but also other cognitive abilities, including efficient executive functioning. An executive dysfunction has been described in dementia with Lewy bodies (DLB) from the early stage. Here, we question the link between executive dysfunction in DLB and narrative comprehension. The aim of our study was to evaluate ND comprehension and to investigate the neuroanatomical basis for its impairment in the early stage of DLB. DLB patients (N = 26) and controls (N = 19) underwent the ND comprehension test of the Montreal Protocol for Evaluation of Communication (MEC). An additional, qualitative analysis was conducted on their verbal productions. Cognitive tests assessing verbal episodic memory, executive functions, naming and oral syntactic comprehension were also performed. Brain gray matter correlates of the ND comprehension test were examined using voxel-based morphometry (VBM). An ND comprehension impairment was found for prodromal and mild DLB patients as compared to controls. These difficulties were correlated with the Frontal Assessment Battery (FAB) score. ND comprehension impairment in DLB was further characterized by a deficit in the organization and the logic of the discourse. Moreover, VBM analysis revealed a correlation between striatal gray matter volumes and DLB patients’ ability to extract and organize relevant information (p < 0.05, FDR correction, cluster level). The ND comprehension impairment in DLB patients could be related to their executive dysfunction through a deficit of information selection and organization that correlates with the volumetric reduction of striatal gray matter.