Patients with motor symptoms on the right side would have a more pronounced cognitive decline and a higher risk of dementia, while those with symptoms on the left side would more often develop psychiatric problems such as depression, anxiety and alteration of emotions recognition. These are the conclusions of a team from the University of Geneva and the University Hospitals in Geneva according to a review of 80 studies on the influence on the side of the first motor symptoms on the trajectory of those who are non-motors and on the response to treatments.
If the analysis notes variable results from one study to another, it retains that taking into account the asymmetry of motor symptoms in the diagnosis and treatment of Parkinson’s disease could improve the personalization of care. These results are published in npj Parkinson’s Diseasea group’s review Springer Nature.
In Parkinson’s disease, motor symptoms on the right side represent signs of dysfunction of the left hemisphere of the brain, and vice versa for symptoms on the left side with the right hemisphere.
Dementia biomarkers in the event of a predominance on the right
The analysis led by this Swiss team shows that the asymmetry of the motor symptoms allows you to establish phenotypes of patients from the diagnosis, or even in the prodromic phase. Patients with predominant motor symptoms on the right have memory, executive function and language disorders, “Probably due to the damage of the left hemisphere”, as well as greater vulnerability to apathy. In these patients, some studies find dementia biomarkers (atrophy of the left hemisphere and blood tests). While those with left predominance are more inclined to visuospatial and emotional deficits, “Probably due to the damage of the right hemisphere”.
In addition to the progression of the disease, motor asymmetry could affect responses to treatment, such as deep brain stimulation and dopaminergic agonists. Indeed“The clinical benefits of brain stimulation seem very dependent on the asymmetry of motor symptoms”, lit-on. According to studies, patients with left predominance are more vulnerable to post-stimulation neuropsychological decline but more inclined to improve psychiatric symptoms. For those with straight predominance, they would be less prone to cognitive side effects but more exposed to emotional symptoms.
For the research team, the next step is to answer several methodological questions, for example “How can the asymmetry of the disease be measured reliably on the basis of observable symptoms?” »» or “Can similar patterns be found in other disorders associated with Parkinson’s disease? ».
