Comparison of Cerebral Glucose Metabolism between Possible and Probable Multiple System Atrophy

F-18 FP-CIT PET in Multiple System Atrophy of the Cerebellar Type: Additional Role in Treatment

We evaluated the difference in the status of dopamine transporters (DATs) depending on Parkinsonism, cerebellar, and autonomic features using F-18 FP-CIT positron emission tomography (PET) in multiple system atrophy with cerebellar ataxia (MSA-C). We also assessed whether the DAT PET could be useful in the management of MSA-C. Forty-nine patients who were clinically diagnosed as possible to probable MSA-C were included. Based on the F-18 FP-CIT PET results, patients were classified into normal (n = 25) and abnormal (n = 24) scan groups. There were statistically significant differences in rigidity, bradykinesia, postural instability, asymmetry, and specific uptake ratio (SUR) between the two groups but no significant differences in tremor and cerebellar/autonomic symptoms. Dopaminergic medications were administered to 22 patients. All seven patients with normal scans showed no change, while 10 of the 15 patients with abnormal scans showed clinical improvement. There was a trend of a negative correlation between levodopa equivalent dose and SUR, but it was not statistically significant. DAT imaging, such as F-18 FP-CIT PET, may be useful in predicting the response to dopaminergic medication regardless of cerebellar/autonomic symptoms in MSA-C. In addition to being used for the diagnosis of the disease, it may be used as a treatment decision index.

A systematic review of lessons learned from PET molecular imaging research in atypical parkinsonism

PURPOSE

To systematically review the previous studies and current status of positron emission tomography (PET) molecular imaging research in atypical parkinsonism.

METHODS

MEDLINE, ISI Web of Science, Cochrane Library, and Scopus electronic databases were searched for articles published until 29th March 2016 and included brain PET studies in progressive supranuclear palsy (PSP), multiple system atrophy (MSA), and corticobasal syndrome (CBS). Only articles published in English and in peer-reviewed journals were included in this review. Case-reports, reviews, and non-human studies were excluded.

RESULTS

Seventy-seven PET studies investigating the dopaminergic system, glucose metabolism, microglial activation, hyperphosphorilated tau, opioid receptors, the cholinergic system, and GABA_A receptors in PSP, MSA, and CBS patients were included in this review. Disease-specific patterns of reduced glucose metabolism have shown higher accuracy than dopaminergic imaging techniques to distinguish between parkinsonian syndromes. Microglial activation has been found in all forms of atypical parkinsonism and reflects the known distribution of neuropathologic changes in these disorders. Opioid receptors are decreased in the striatum of PSP and MSA patients. Subcortical cholinergic dysfunction was more severe in MSA and PSP than Parkinson's disease patients although no significant changes in cortical cholinergic receptors were seen in PSP with cognitive impairment. GABA_A receptors were decreased in metabolically affected cortical and subcortical regions in PSP patients.

CONCLUSIONS

PET molecular imaging has provided valuable insight for understanding the mechanisms underlying atypical parkinsonism. Changes at a molecular level occur early in the course of these neurodegenerative diseases and PET imaging provides the means to aid differential diagnosis, monitor disease progression, identify of novel targets for pharmacotherapy, and monitor response to new treatments.