De novo Parkinson disease (PD)-related brain metabolic patterns may be an effective neuroimaging biomarker that highlights metabolic alterations in the prodromal stage of PD, prodromal Lewy bodies, and may significantly predict prospective phenoconversion in isolated rapid eye movement (REM) sleep behavior disorder (RBD), according to study results published in Neurology.

A team of investigators in Korea conducted a prospective cohort study ( Identifier: NCT02984137) to determine whether PD-related brain metabolic patterns may be used as biomarkers in isolated RBD and to compare metabolic patterns derived from long-stand and de novo PD.

Of the 100 individuals included in the analysis, 24 people were healthy controls, 30 people had isolated RBD, 25 people had de novo PD with prolonged RBD symptoms, and 21 people had long-standing PD.

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Movement disorders society-Unified PD Rating Scale motor scores were significantly associated with long-standing PD (P =.013) but not de novo PD with prolonged RBD (P =.076). In a butanol threshold test, de novo PD-related brain metabolic patterns were associated with olfaction (P =.018) among patients with isolated RBD but not in patients with de novo PD and prolonged RBD (P =.21).

In addition to the 30 patients with isolated RBD, 14 more patients from a separate validation sample were included in a longitudinal follow-up to predict disease conversion; 12 patients progressed to develop a neurodegenerative disease (PD, n=7; multiple system atrophy, n=1; dementia with Lewy bodies, n=4).

The mean follow-up was 3.02 years and there was an estimated 35.5% phenoconversion rate at 5 years, with an overall annual conversion rate of 7.1%. While scores for both de novo PD-related brain metabolic patterns and long-standing PD were higher at baseline for disease converters compared with nondisease converters, the larger effect size in de novo PD-related brain metabolic patterns suggested that there is a higher discriminability of future converters with de novo PD-related brain metabolic patterns compared with long-term PD.

In cut-off ranges for the 2 metabolic pattern expressions from 1.5 to 3 standard deviations from normal control value, de novo PD-related brain metabolic patterns significantly predicted phenoconversion in all cut-off ranges (hazard ratio [HR], 5.90~38.6). Long-term PD significantly predicted phenoconversion for partial range of cut-off.

“The [de novo PD-related brain metabolic patterns] can be an efficient biomarker individually applicable in [isolated REM sleep behavior disorder],” the study authors wrote. They concluded, “Validation of the [de novo PD-related brain metabolic patterns] from an independent [de novo PD with prolonged RBD] and [isolated REM sleep behavior disorder] cohort from the different ethnic backgrounds would further enhance the reliability of [de novo PD-related brain metabolic patterns].”


Shin JH, Lee JY, Kim YK, et al. Parkinson disease-related brain metabolic patterns and neurodegeneration in isolated REM sleep behavior disorder. Neurology. Published online May 19, 2021. doi:10.1212/WNL.0000000000012228