Cardiac ¹²³I-MIBG scintigraphy: A window into the brain in Parkinsonism?

Excerpt

Parkinson’s disease (PD) and other forms of neurodegenerative parkinsonism are multisystem disorders affecting several components of the central and peripheral nervous system.1,2 ¹²³I-meta-iodobenzylguanidine (¹²³I-MIBG) is a false adrenergic neurotransmitter analog of norepinephrine, and cardiac ¹²³I-MIBG scintigraphy can be used to evaluate noradrenergic postganglionic cardiac innervation. The use of cardiac ¹²³I-MIBG scintigraphy has been established in the differential diagnosis of Lewy body diseases (PD and dementia with Lewy bodies). This is because patients with Lewy body diseases display a significantly lower myocardial ¹²³I-MIBG uptake in comparison to healthy controls and individuals with other parkinsonian syndromes such as multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration.3,4 However, the role of cardiac ¹²³I-MIBG scintigraphy in parkinsonism is not limited to diagnosis. This imaging technique could also help detect early markers of neurodegeneration that predate the clinical diagnosis of PD, which is a prerequisite step in the development of disease-modifying therapies.5 A recent study by Takahashi et al showed a strong quantitative correlation between cardiac ¹²³I-MIBG uptake and corresponding sympathetic axon loss in the cardiac tissue samples of 23 patients with autopsy-confirmed Lewy body diseases.6 This study confirmed the potential use of cardiac ¹²³I-MIBG scintigraphy as a biomarker of cardiac sympathetic axon loss and Lewy body pathology. Moreover, cardiac ¹²³I-MIBG scintigraphy may have significant clinical implications. Changes in ¹²³I-MIBG uptake over time may help to characterize patients with PD, identify clinical phenotypes, and aid in predicting prognosis.7 Finally, cardiac ¹²³I-MIBG scintigraphy may be used as a pathophysiological indicator in PD and related disorders. For the past 20 years, genetic research has led to the identification of several monogenic forms of PD and of numerous genetic risk factors, yet little is known about the cardiac autonomic innervation in these patients.8 …