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.

Striatal dopamine correlates to memory and attention in Parkinson's disease

Parkinson's disease (PD) is clinically characterized by motor symptoms, however, specific cognitive impairments are common and poorly understood. This study was designed to assess whether cognitive performances are related to dopamine active transporter (DAT) availability in non-demented PD subjects. Fifty-four non-demented PD patients were enrolled. They underwent [^99mTc] TRODAT-1 SPECT/CT and a comprehensive neuropsychological battery including attention/executive and memory tests. Multiple linear regression controlling the effect of age, disease duration and education was applied. The significance level was set at P values of < 0.02. After controlling the effect of age, disease duration and education, lower scores in Rey's Auditory-Verbal Learning Test (RAVLT)/immediate recall were significantly related with lower uptake values in the less affected striatum and more affected caudate. Lower scores in RAVLT/short-term recall were also significantly associated with lower uptake values in the more affected caudate and reduced performance in Trail Making Test part B was related with reduced DAT values in the less affected anterior putamen. Our findings suggest that reduced DAT availability in both caudate and putamen is related to reduced performances in some memory and attention/executive tasks. Nigrocaudate dysfunction is related to lower memory performance while dopamine depletion in the anterior putamen is related to poorer attention performance. If the dopaminergic defects can mostly explain all the cognitive symptoms or this phenomenon just co-occur with other anatomical and biochemical changes remains unknown. Further studies in larger patient samples are required to clarify this issue.