Dopamine Transporter Loss Visualized With FP-CIT SPECT in the Differential Diagnosis of Dementia With Lewy Bodies

Background

Dementia with Lewy bodies (DLB) is a common form of late-life dementia that can be difficult to differentiate from other disorders, especially Alzheimer disease (AD), during life. At autopsy the striatal dopaminergic transporter is reduced.

Objectives

To examine the extent and pattern of dopamine transporter loss using iodine I 123–radiolabeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (FP-CIT) with single-photon emission computed tomography (SPECT) in DLBs compared with other dementias and to assess its potential to enhance a differential diagnosis.

Design

Cohort study comparing FP-CIT with criterion standard of consensus clinical diagnosis.

Setting

General hospital.

Participants

One hundred sixty-four older subjects (33 healthy older control subjects, 34 with NINCDS/ADRDA [National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer's Disease and Related Disorders Association]-confirmed AD, 23 with consensus guideline–confirmed DLB, 38 with United Kingdom's Parkinson Disease Society Brain Bank–confirmed Parkinson disease [PD], and 36 with PD and dementia).

Interventions

Injection of¹²³I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane with SPECT scan performed at 4 hours.

Main Outcome Measures

Visual ratings of scans and region of interest analysis.

Results

Significant reductions (P<.001) in FP-CIT binding occurred in the caudate and anterior and posterior putamens in subjects with DLB compared with subjects with AD and controls. Transporter loss in DLBs was of similar magnitude to that seen in PD, but with a flatter rostrocaudal (caudate-putamen) gradient (P= .001), while the greatest loss in all 3 areas was seen in those who had PD and dementia. Both region of interest analysis and visual ratings provided good separation between DLBs and AD (region of interest: sensitivity, 78%; specificity, 94%; positive predictive value, 90%) but not among subjects with DLB, PD, and PD with dementia.

Conclusions

Dopamine transporter loss can be detected in vivo using FP-CIT SPECT in DLB. Further studies, especially of subjects with DLB without PD, are required to fully establish use in clinical practice.