When caution becomes neglect: Deep brain stimulation and cognitive impairment in Parkinson's disease.

Over the past 25 years, a prevailing clinical dogma has held that significant cognitive impairment constitutes a contraindication to the use of Deep Brain Stimulation in Parkinson's disease. Whilst multiple studies, excluding such patients, have repeatedly emphasised the motoric benefits of this approach, less consideration has been given to the consequences of excluding this cohort. However, emerging evidence suggests that Deep Brain Stimulation in Parkinson's Disease patients with moderate cognitive impairment not only allows for significant reductions in dopaminergic therapy (typically alleviating many non-motor symptoms) but also favours survival and reduced admissions into institutional care. These small studies have not demonstrated significantly increased surgical or stimulation related complications in such patients and would suggest that further prospective studies, specifically evaluating this approach are warranted. Indeed, in the absence of a successful disease modifying therapy, exclusion from Deep Brain Stimulation often commits these advanced patients to a trajectory of ineffective pharmacological complexity. Alternative infusion therapies are associated with high discontinuation rates whilst escalating dopaminergic therapy, frequently exacerbates non-motor complications, including orthostatic hypotension, hallucinations, somnolence, and cognitive fluctuations. This flawed treatment strategy further accelerates functional decline, hospitalisation, and institutionalisation. Therefore, a reluctance or failure to offer Deep Brain Stimulation, where appropriate, may inadvertently consign patients to poorer long-term outcomes.