Cognitive decline is common with the progression of Parkinson's disease (PD). Different candidate biomarkers are currently studied for the risk of dementia in PD. Several studies have shown that quantitative EEG (QEEG) is a promising predictor of PD-related cognitive decline. In this paper we briefly outline the basics of QEEG analysis and analyze the recent publications addressing the predictive value of QEEG in the context of cognitive decline in PD. The MEDLINE database was searched for relevant publications from January 01, 2005, to March 02, 2015. Twenty-four studies reported QEEG findings in various cognitive states in PD. Spectral and connectivity markers of QEEG could help to discriminate between PD patients with different level of cognitive decline. QEEG variables correlate with tools for cognitive assessment over time and are associated with significant hazard ratios to predict PD-related dementia. QEEG analysis shows high test-retest reliability and avoids learning effects associated with some neuropsychological testing; it is noninvasive and relatively easy to repeat.

Objective: We investigated quantitative electroencephalography (qEEG) and clinical parameters as potential risk factors of severe cognitive decline in Parkinson’s disease.Methods: We prospectively investigated 37 patients with Parkinson’s disease at baseline and follow-up (after 3 years). Patients had no severe cognitive impairment at baseline. We used a summary score of cognitive tests as the outcome at follow-up. At baseline we assessed motor, cognitive, and psychiatric factors; qEEG variables [global relative median power (GRMP) spectra] were obtained by a fully automated processing of high-resolution EEG (256-channels). We used linear regression models with calculation of the explained variance to evaluate the relation of baseline parameters with cognitive deterioration.Results: The following baseline parameters significantly predicted severe cognitive decline: GRMP theta (4–8 Hz), cognitive task performance in executive functions and working memory.Conclusions: Combination of neurocognitive tests and qEEG improves identification of patients with higher risk of cognitive decline in PD.

Objective: To investigate the incidence of serious adverse events (SAE) of subthalamic deep brain stimulation (STN-DBS) in elderly patients with Parkinson's disease (PD).Methods: We investigated a group of 26 patients with PD who underwent STN-DBS at mean age 63.2 ± 3.3 years. The operated patients from the EARLYSTIM study (mean age 52.9 ± 6.6) were used as a comparison group. Incidences of SAE were compared between these groups.Results: A higher incidence of psychosis and hallucinations was found in these elderly patients compared to the younger patients in the EARLYSTIM study (p < 0.01).Conclusions: The higher incidence of STN-DBS-related psychiatric complications underscores the need for comprehensive psychiatric pre- and postoperative assessment in older DBS candidates. However, these psychiatric SAE were transient, and the benefits of DBS clearly outweighed its adverse effects.

Background DBS is commonly used to treat Parkinson's disease (PD). DBS is not considered to cause major cognitive side effects, but some research groups have reported that it can cause decreased verbal fluency. The influence of age on DBS cognitive outcome is unclear. We investigated the possible influence of patients' age, level of education, disease duration, disease progression, depression, and levodopa equivalent dose (LED) on verbal fluency performance in patients with PD who underwent DBS of the subthalamic nucleus (STN‐DBS). In this article, we investigated the influence of demographic and clinical parameters, especially age, on cognitive performance post‐DBS in PD patients. Methods Forty‐three patients with PD and without major psychiatric illness (according to Diagnostic and Statistical Manual of Mental Disroders, Fourth Edition) were enrolled in the study. Median age was 64.0 years (range, 46–77). In 21 patients, the indication for DBS was established on clinical grounds in keeping with international guidelines; these patients underwent STN‐DBS, and the remaining 22 did not. Cognitive performance in both groups was assessed by standard neuropsychological test batteries at baseline and after median follow‐up of 7 months. Results A statistically significant decline in the semantic category of verbal fluency task was found in the STN‐DBS group (P < 0.01). Linear regression model revealed an influence of age (P < 0.01) and disease duration (P < 0.01) in relation to this decline. Conclusions This study confirms previous findings that verbal fluency declines after STN‐DBS in PD patients in comparison to PD patients without DBS. This decline is related to age and disease duration.