Deep Brain Stimulation and Cognitive Decline in Parkinson’s Disease: A Clinical Review

Abstract

Parkinson’s disease is a common and often debilitating disorder, with a growing prevalence accompanying global population aging. Current drug therapy is not satisfactory enough for many patients, especially after a few years of symptom progression. This is mainly due to the motor complications that frequently emerge as disease progresses. Deep brain stimulation (DBS) is a useful therapeutic option in carefully selected patients that significantly improves motor symptoms, functional status, and quality of life. However, cognitive impairment may limit patient selection for DBS, as patients need to have sufficient mental capabilities in order to understand the procedure, as well as its benefits and limitations, and cooperate with the medical team throughout the process of selection, surgery, and postsurgical follow-up. On the other hand it has been observed that certain aspects of cognitive performance may decline after DBS, namely when the therapeutic target is the widely used subthalamic nucleus. These are important pieces of information for patients, their families, and health care professionals. This manuscript reviews these aspects and their clinical implications.

Parkinson's disease cluster: the wind of change

“…None of these therapies have, so far, shown to be getting any closer to preventing disease progression and are, therefore, essentially symptomatic or palliative. Despite the efficacy of dopaminergic therapies in improving motor function and overall quality of life, they fail to prevent disease progression, and are associated with important complications [8][9][10]. This is consistent with the notion that the upstream molecular processes responsible for the cascade of pathological events are not yet being targeted by therapies currently available or under clinical development.…”

Characterizing Motor and Cognitive Effects Associated With Deep Brain Stimulation in the GPi of Hemi-Parkinsonian Rats

“…The benefits of DBS are strongly tied to the stimulation amplitude and frequency, and generally must be tuned in order to maximize efficacy of the treatment [17], [18], [25], [30]. This is true not only in computational and experimental studies in animals, but in human studies as well [3], [4]. Although global motor improvement was not found, the quantified behavior is interesting in relation to the other variables examined throughout the experiment.…”

Does early verbal fluency decline after STN implantation predict long-term cognitive outcome after STN-DBS in Parkinson's disease?

“…Even though the procedure is not considered to cause major cognitive side-effects, it is associated with changes in executive function, in particular decreased verbal fluency (VF) [2]. Several factors are thought to predict cognitive decline following STN-DBS, such as advanced age, axial signs, levodopa resistant symptoms, visual hallucinations, vascular lesion load, and poor baseline cognitive performance [3,4]. Higher formal education, higher levodopa equivalent dose, and younger age at onset also correlate with cognitive worsening after STN-DBS in PD [5].…”