Parkinson’s Subtypes Share Early Psychiatric Features, But Diverge as Disease Progresses, Study Suggests

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by Diogo Pinto |

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The Parkinson’s Disease News Today forums are a place to connect with other patients, share tips and talk about the latest research. Check them out today!In the early stages, three motor subtypes of Parkinson’s disease share similar psychiatric and cognitive features, with the distinct psychiatric profiles associated with each type only appearing as the disease progresses, a study suggests.

The study, “Psychiatric profile of motor subtypes of de novo drug-naïve Parkinson’s disease patients,” was published in the journal Brain and Behavior.

Parkinson’s disease is a diverse neurodegenerative disorder with distinct motor and non-motor symptoms. It is already known that different motor subtypes of the disease evolve with different clinical courses and prognoses.

Parkinson’s can be divided into three main clinical subtypes according to the predominant motor features: tremor-dominant, where tremor is a predominant symptom of the disease; akinetic-rigid or postural instability gait difficulty, characterized by stiffness or inflexibility of the muscles; or mixed, with no prevailing motor features.

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Patients diagnosed with akinetic-rigid usually show a faster disease progression and are at higher risk of developing disability and dementia. On the other hand, progression of the tremor-dominant form is slower and associated with less cognitive decline, visual hallucinations, and depression.

These differences are attributed to lower dopamine levels in the brains of akinetic-rigid patients than in those with the tremor-dominant subtype.

Italian researchers studied the psychiatric, cognitive, and motor profiles of these three Parkinson’s subtypes in early, untreated Parkinson’s patients. They used untreated patients to avoid bias of the medication effect.

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They included 68 newly diagnosed Parkinson’s patients, of whom 39 were akinetic-rigid, seven were mixed, and were 22 tremor-dominant. The participants underwent a complete assessment of psychiatric symptoms, including depression, anxiety, and apathy; cognitive issues, such as memory, language, attention; and motor features.

No differences were observed among the three Parkinson’s subtypes in any of the psychiatric and cognitive variables assessed. Researchers hypothesize that psychiatric differences among the three motor subtypes are not present in the very early stages of the disease, suggesting that a possible differentiation emerges only over the progression of the disease and potentially with its interaction with dopaminergic replacement therapy.

“This idea is widely supported by the literature on PD patients with longer disease duration and under antiparkinsonian treatment showing greater cognitive deterioration and psychiatric symptoms in AR patients,” the authors wrote.

“The evolution of psychiatric features is not predictable based on early motor presentation and regular follow-ups are needed to investigate their different possible progression,” they concluded.