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Introduction:The burden of non-motor symptoms (NMS) is a major determinant of health-related quality of life in Parkinson's disease (PD), particularly at its late stage. Areas covered: The late stage is usually defined as the period from unstable advanced to the palliative stage, characterized by a combination of emerging treatment-resistant axial motor symptoms (freezing of gait, postural instability, falls and dysphagia), as well as both non-dopaminergic and dopaminergic NMS: cognitive decline, neuropsychiatric symptoms, aspects of dysautonomia, pain and sleep disturbances (insomnia and excessive day-time sleepiness). Here, the authors summarize the current knowledge on NMS dominating the late stage of PD and propose a pragmatic and clinically focused approach for their recognition and treatment. Expert opinion: The NMS progression pattern is complex and remains under-researched. While dopamine-dependent NMS may improve with dopamine replacement therapy, non-dopamine dependent NMS worsen progressively and culminate at the late stages of PD. Furthermore, some PD specific features could interact negatively with other comorbidities, multiple medication use and frailty -the evaluation of these aspects is important in the creation of personalized management plans in the late stage of PD.

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BackgroundSubthalamic deep brain stimulation (DBS) is an established therapy to treat Parkinson’s disease (PD). To maximize therapeutic outcome, optimal DBS settings must be carefully selected for each patient. Unfortunately, this is not always achieved because of: (1) increased technological complexity of DBS devices, (2) time restraints, or lack of expertise, and (3) delayed therapeutic response of some symptoms. Biomarkers to accurately predict the most effective stimulation settings for each patient could streamline this process and improve DBS outcomes.ObjectiveTo investigate the use of evoked potentials (EPs) to predict clinical outcomes in PD patients with DBS.MethodsIn ten patients (12 hemispheres), a monopolar review was performed by systematically stimulating on each DBS contact and measuring the therapeutic window. Standard imaging data were collected. EEG-based EPs were then recorded in response to stimulation at 10 Hz for 50 s on each DBS-contact. Linear mixed models were used to assess how well both EPs and image-derived information predicted the clinical data.ResultsEvoked potential peaks at 3 ms (P3) and at 10 ms (P10) were observed in nine and eleven hemispheres, respectively. Clinical data were well predicted using either P3 or P10. A separate model showed that the image-derived information also predicted clinical data with similar accuracy. Combining both EPs and image-derived information in one model yielded the highest predictive value.ConclusionEvoked potentials can accurately predict clinical DBS responses. Combining EPs with imaging data further improves this prediction. Future refinement of this approach may streamline DBS programming, thereby improving therapeutic outcomes.Clinical trial registrationClinicalTrials.gov, identifier NCT04658641.

Background: Since the inception of DBS, cathodic pulses have been used. Objective: To investigate the effect of anodic and symmetric biphasic pulses on the therapeutic window (TW) in essential tremor (ET) patients. Methods: A randomized, doubled-blinded, cross-over design was used to test the effect of cathodic, anodic and symmetric biphasic pulses (cathode-first and anode-first) on the TW in an acute clinical setting. TW was defined as the difference between the minimal stimulation amplitude provoking side effects and minimal stimulation amplitude inducing tremor arrest. Results: 9 ET patients (10 hemispheres) were included. Anodic stimulation induced a significantly larger TW compared to cathodic stimulation (p ¼ 0.008). Symmetric biphasic stimulation also widened the TW compared to cathodic stimulation for both cathode-(p ¼ 0.047) and anode-first (p ¼ 0.008) biphasic pulses. For both anodic and biphasic pulses, the effect on TW was mainly driven by the change in side effect threshold. The order of the phases in the biphasic pulse had a significant effect on the side effect threshold (p ¼ 0.039), with biphasic-anode first having the highest value. All pulse shapes were safe in the acute setting. Conclusion: Anodic and symmetric biphasic pulses increase TW in ET patients.