Imaging in Movement Disorders

OBJECTIVE This article reviews commonly used imaging modalities in movement disorders, particularly parkinsonism. The review includes the diagnostic utility, role in differential diagnosis, reflection of pathophysiology, and limitations of neuroimaging in the setting of movement disorders. It also introduces promising new imaging modalities and describes the current status of research.

LATEST DEVELOPMENTS Iron-sensitive MRI sequences and neuromelanin-sensitive MRI can be used to directly assess the integrity of nigral dopaminergic neurons and thus may reflect disease pathology and progression throughout the full range of severity in Parkinson disease (PD). The striatal uptake of presynaptic radiotracers in their terminal axons as currently assessed using clinically approved positron emission tomography (PET) or single-photon emission computed tomography (SPECT) imaging correlates with nigral pathology and disease severity only in early PD. Cholinergic PET, using radiotracers that target the presynaptic vesicular acetylcholine transporter, constitutes a substantial advance and may provide crucial insights into the pathophysiology of clinical symptoms such as dementia, freezing, and falls.

ESSENTIAL POINTS In the absence of valid, direct, objective biomarkers of intracellular misfolded α-synuclein, PD remains a clinical diagnosis. The clinical utility of PET- or SPECT-based striatal measures is currently limited given their lack of specificity and inability to reflect nigral pathology in moderate to severe PD. These scans may be more sensitive than clinical examination to detect nigrostriatal deficiency that occurs in multiple parkinsonian syndromes and may still be recommended for clinical use in the future to identify prodromal PD if and when disease-modifying treatments become available. Multimodal imaging to evaluate underlying nigral pathology and its functional consequences may hold the key to future advances.

Address correspondence to Dr Baijayanta Maiti, Department of Neurology, Washington University School of Medicine, Campus Box 8111, 660 S Euclid Ave, Saint Louis, MO 63110, [email protected].

RELATIONSHIP DISCLOSURE: The institution of Dr Maiti has received research support from the National Center for Advancing Translational Sciences and the National Institute of Neurological Disorders and Stroke of the National Institutes of Health. Dr Perlmutter has received personal compensation in the range of $0 to $499 for serving as an officer or member of the Board of Directors for the Parkinson Study Group, and in the range of $500 to $4999 for serving as an officer or member of the Board of Directors for the CHDI Foundation, as an expert witness for Wood, Cooper and Peterson, LLC, and Simmons and Simmons LLP, as a lecturer for Boston University, as an external advisor for Stanford University, and as a visiting professor with Beth Israel Hospital and the University of Pennsylvania. The institution of Dr Perlmutter has received research support from the American Parkinson Disease Association, the Barnes-Jewish Hospital Foundation, the CHDI Foundation, the Huntington Disease Society of America, The Michael J Fox Foundation, the National Institutes of Health, the University of California San Diego, and the University of Western Toronto.

UNLABELED USE OF PRODUCTS/INVESTIGATIONAL USE DISCLOSURE: Drs Maiti and Perlmutter report no disclosures.