Accuracy of Cardiac Innervation Scintigraphy for Mild Cognitive Impairment With Lewy Bodies

Abstract

ObjectiveTo provide evidence that cardiac I-123-metaiodobenzylguanidine sympathetic innervation imaging (MIBG) scintigraphy differentiates probable mild cognitive impairment with Lewy bodies (MCI-LB) from mild cognitive impairment due to Alzheimer disease (MCI-AD), we scanned patients with MCI and obtained consensus clinical diagnoses of their MCI subtype. We also performed baseline FP-CIT scans to compare the accuracy of MIBG and FP-CIT.MethodsWe conducted a prospective cohort study into the accuracy of cardiac MIBG scintigraphy in the diagnosis of MCI-LB. Follow-up clinical assessment was used to diagnose MCI-AD (no core features of MCI-LB and normal FP-CIT), probable MCI-LB (2 or more core features, or 1 core feature with abnormal FP-CIT), or possible MCI-LB (1 core feature or abnormal FP-CIT). For the comparison between MIBG and FP-CIT, only core clinical features were used for diagnosis.ResultsWe recruited 95 people with mild cognitive impairment. Cardiac MIBG was abnormal in 22/37 probable and 2/15 possible MCI-LB cases and normal in 38/43 MCI-AD cases. The sensitivity in probable MCI-LB was 59% (95% confidence interval [CI], 42%–75%), specificity 88% (75%–96%), and accuracy 75% (64%–84%). The positive likelihood ratio was 5.1 and negative likelihood ratio 0.46. With symptom-only diagnoses, the accuracies were 79% for MIBG (95% CI, 68%–87%) and 76% for FP-CIT (95% CI, 65%–85%).ConclusionsCardiac MIBG appears useful in early disease, with an abnormal scan highly suggestive of MCI-LB. Validation in a multicenter setting is justified.Classification of EvidenceThis study provides Class I evidence that cardiac MIBG distinguishes MCI-LB from MCI-AD.

Assessment of autonomic symptoms may assist with early identification of mild cognitive impairment with Lewy bodies

“…Cardiac scintigraphy with MIBG is a biomarker for DLB 29 and in this cohort we recently reported that MIBG also had diagnostic accuracy in distinguishing MCI-LB from MCI-AD, 12 providing further evidence that autonomic nervous system involvement is present at the MCI stage. However, we did not find any clear association between cardiac denervation assessed with MIBG imaging and autonomic symptoms within MCI-LB.…”

“…Dopaminergic 123I‐N‐fluoropropyl‐2β‐carbomethoxy‐3β‐(4‐iodophenyl) single‐photon emission computed tomography (FP‐CIT) and cardiac MIBG imaging were carried out, as previously described 12,14 . FP‐CIT images were visually rated as normal or abnormal by a five‐person panel of experienced image analysts, blind to clinical information 14 .…”

“…All participants underwent detailed medical review and cognitive assessment, 13 and imaging 12,14,15 at baseline which have been previously reported, with further longitudinal review at approximately annual follow-ups.…”

“…cardiac MIBG imaging were carried out, as previously described. 12,14 FP-CIT images were visually rated as normal or abnormal by a fiveperson panel of experienced image analysts, blind to clinical information. 14 MIBG images were classified as abnormal given a heart: mediastinum uptake ratio (HMR) of <1.86 based on data from locally-recruited healthy controls.…”

“…6,7 Recent efforts have led to the characterisation of the cognitive prodrome of DLB -mild cognitive impairment (MCI) with Lewy bodies (MCI-LB) -in research settings, with autonomic symptoms included as supportive clinical features. 8 While previous research has suggested that a retrospective history of autonomic dysfunction is common in DLB, 9 that individuals with pure autonomic failure are at high risk of later conversion to DLB, 10 MCI-LB may feature greater heart rate variability than in AD, 11 and that MCI-LB may be characterised by abnormal cardiac metaiodobenzylguanidine (MIBG) imaging of the sympathetic nervous system, 12 it is yet unclear whether MCI-LB features greater severity of autonomic symptoms when prospectively assessed, and whether these may differentiate MCI-LB from normal ageing or AD.…”