Nonmotor symptoms contribute to early Parkinson’s subtypes

By Eleanor McDermid, Senior medwireNews Reporter

Researchers have characterized four distinct subgroups of patients with early Parkinson’s disease (PD), distinguished by both motor and nonmotor symptoms.

“[T]he identification of these subgroups ought to serve more as a model for testing hypotheses, rather than as a definitive classification system,” caution study author Paolo Barone (University of Salerno, Italy) and colleagues.

Their cluster analysis of 100 newly diagnosed outpatients with PD confirmed two previously described categories: patients with young age at onset and mild motor impairment and older patients with more rapid progression.

However, they also identified “two distinct subgroups of patients, which have been profiled according to both presence and relevance of NMS [nonmotor symptoms].”

This gave four groups: benign pure motor; benign mixed motor-nonmotor; nonmotor dominant; and motor dominant.

Barone et al recognize that “benign” may be an “inappropriate” term to describe a condition such as PD. They explain that benign is intended to indicate relatively “slow short-term progression and possibly longer time span to reach such milestones as motor complications, falls, and dementia.”

Of the two benign groups, the mixed motor-nonmotor group had a low Unified PD Rating Scale (UPDRS)-III score and a low progression rate, but had mild depression, anxiety, and frontal cognitive impairment, and intermediate NMS scores, with sexual function particularly affected.

The benign pure motor group had intermediate UPDRS-III scores, and an intermediate rate of progression over 2 years of follow-up, but they had no psychiatric or neurocognitive complaints and very low NMS scores.

The nonmotor-dominant group also had intermediate UPDRS-III scores and progression rates, but additionally had intermediate psychiatric and cognitive problems, and high NMS scores, particularly for urinary symptoms.

“Identification of clinical subgroups with almost equivalent motor disability and different non-motor involvement may be crucial, suggesting that independent processes are responsible for motor and non-motor symptoms,” notes the team in PLoS One.

The group with dominant motor symptoms had high UPDRS-III scores, high depression, anxiety, and frontal cognitive impairment, but intermediate NMS scores. As expected, this group had the highest progression rate, requiring markedly higher levodopa equivalent daily doses than the other groups by the 2-year follow-up.

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