Standardised Neuropsychological Assessment for the Selection of Patients Undergoing DBS for Parkinson's Disease

Non-Motor Effects of Low-Frequency Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease: A Systematic Review

INTRODUCTION

Deep brain stimulation of the subthalamic nucleus is an effective therapy for the motor symptoms of Parkinson's disease (PD). Typically, stimulation is applied at a high frequency (≥100 Hz) to alleviate motor symptoms. However, the effects on non-motor symptoms can be variable. Low-frequency oscillations are increasingly recognized as playing an important role in the non-motor functions of the subthalamic nucleus. Therefore, it has been hypothesized that low-frequency stimulation of the subthalamic nucleus (<100 Hz) may have a direct effect on these non-motor functions, thereby preferentially impacting non-motor symptoms of PD. Despite important therapeutic implications, the literature on this topic has not been summarized.

METHOD

To understand the current state of the field, we performed a comprehensive systematic review of the literature assessing the non-motor effects of low-frequency stimulation of the subthalamic nucleus in PD. We performed a supplementary meta-analysis to assess the effects of low- versus high-frequency stimulation on verbal fluency outcomes.

RESULTS

Our search returned 7,009 results, of which we screened 4,199 results. A total of 145 studies were further assessed for eligibility, and a total of 21 studies met our inclusion criteria, representing 297 patients. These studies were a mix of case reports and control trials. The four clinical outcomes measured were sleep, sensory perception, cognition, and mood. A supplementary meta-analysis of six studies investigating the impact of low-frequency stimulation on verbal fluency did not find any significant results when pooling across subgroups.

CONCLUSION

LFS of the STN may have benefits on a range of cognitive and affective symptoms in PD. However, current studies in this space are heterogeneous, and the effect sizes are small. Factors that impact outcomes can be divided into stimulation and patient factors. Future work should consider the interactions between stimulation location and stimulation frequency as well as how these interact depending on the specific non-motor phenotype.

The Instrumental Activities of Daily Living in Parkinson’s Disease Patients Treated by Subthalamic Deep Brain Stimulation

Background

Everyday functioning and instrumental activities of daily living (IADL) play a vital role in preserving the quality of life in patients with Parkinson’s disease (PD) after deep brain stimulation of the subthalamic nucleus (STN-DBS).

Objective

The main goal of the current study was to examine IADL change in pre-and post-surgery of the STN-DBS. We also analyzed the influence of the levodopa equivalent daily dose (LEDD) and global cognitive performance (Dementia Rating Scale; DRS-2) as covariates in relation to IADL.

Methods

Thirty-two non-demented PD patients were administered before and after STN-DBS neurosurgery the Penn Parkinson’s Daily Activities Questionnaire (PDAQ; self-report), the DRS-2 and Beck Depression Inventory (BDI-II) to assess IADL change, global cognition, and depression.

Results

We found a positive effect of STN-DBS on IADL in the post-surgery phase. Moreover, lower global cognition and lower LEDD are predictive of lower IADL in both pre-surgery and post-surgery examinations.

Summary/Conclusion

STN-DBS in PD is a safe method for improvement of everyday functioning and IADL. In the post-surgery phase, we show a relation of IADL to the severity of cognitive impairment in PD and to LEDD.

Neural signatures of hyperdirect pathway activity in Parkinson's disease

Parkinson's disease (PD) is characterised by the emergence of beta frequency oscillatory synchronisation across the cortico-basal-ganglia circuit. The relationship between the anatomy of this circuit and oscillatory synchronisation within it remains unclear. We address this by combining recordings from human subthalamic nucleus (STN) and internal globus pallidus (GPi) with magnetoencephalography, tractography and computational modelling. Coherence between supplementary motor area and STN within the high (21-30 Hz) but not low (13-21 Hz) beta frequency range correlated with 'hyperdirect pathway' fibre densities between these structures. Furthermore, supplementary motor area activity drove STN activity selectively at high beta frequencies suggesting that high beta frequencies propagate from the cortex to the basal ganglia via the hyperdirect pathway. Computational modelling revealed that exaggerated high beta hyperdirect pathway activity can provoke the generation of widespread pathological synchrony at lower beta frequencies. These findings suggest a spectral signature and a pathophysiological role for the hyperdirect pathway in PD.

Cognitive challenges in persons with spina bifida: Bearing on urological dysfunctions?

Aim

To evaluate if adult persons with spina bifida (SB) who have urinary tract complications have cognitive difficulties that can be identified by neuropsychological tests.

Methods

All individuals with SB ≥ 18 years of age registered at a regional outpatient clinic (n = 219) were invited, of which, 154 persons were included. Neuropsychological assessment of their cognitive status was performed with Wechsler Adult Intelligence Scale®—Fourth Edition: Coding, Block design, Arithmetic's, FAS (word generation), Rey Auditory Verbal Test for learning, and delayed recall 30 min. Bladder and bowel function were assessed with questions used by the Nordic Spinal Cord Injury Registry (NSCIR) in structured interviews, by questionnaires, and by chart reviews.

Results

Average neuropsychological test results for this SB population was shown to be approximately 1 SD under the median for the general population. The Coding test showed significantly lower test results as compared with the whole SB group in persons with urinary tract complications, especially urinary tract infections, reduced kidney function, dependent emptying of the bladder, and the bowel and accidental bowel leakage. The Arithmetic's test showed a significant difference between subgroups in all parameters except reduced kidney function whereas the other neuropsychological tests were significantly correlated with some but not all urological parameters.

Conclusion

We propose neuropsychological testing with primarily two tests to find those persons with SB who, due to cognitive challenges, might need extra support to minimize urological complications.

Subthalamic Nucleus Stimulation Does Not Have Any Acute Effects on Verbal Fluency or on Speed of Word Generation in Parkinson's Disease

BACKGROUND

Deep brain stimulation of the subthalamic nucleus (STN-DBS) has been shown to be generally safe from a cognitive perspective, with consistent evidence that the major impact of STN-DBS in Parkinson's disease (PD) is on verbal fluency.

OBJECTIVE

The aim of this study was first to identify the influence of acute manipulation of STN-DBS in PD on the number and time pattern of word generation on different verbal fluency (VF) tasks, phonemic, switching, and cued switching, and second to determine whether cueing improved VF and if cueing effects interacted with STN-DBS effects.

METHODS

Parallel versions of these three verbal fluency tasks were completed by 31 patients with Parkinson's disease who had had bilateral DBS of the STN, twice, with DBS On and Off, with the order counterbalanced across patients.

RESULTS

There was no effect of acute STN-DBS on the total number of words generated during verbal fluency. As expected, the number of words generated significantly declined over the six 10-second intervals of the verbal fluency tasks, but this time pattern of word generation was not altered by STN-DBS. External cueing significantly increased the number of words generated relative to an uncued switching verbal fluency task, but the cueing effect on VF was not altered by STN-DBS.

CONCLUSION

In conclusion, (i) acute STN-DBS manipulation did not alter either verbal fluency performance or the time pattern of word generation and (ii) external cueing significantly improved verbal fluency performance both with STN-DBS On and Off.

Presurgical Psychological Evaluation: Risk Factor Identification and Mitigation

Presurgical psychological evaluations (PPEs) are becoming an established component of the surgical process, though methods of conducting PPEs are variable. There is a lack of clarity about the goals of PPEs, the types of information that should be included, and the process for integrating information and making recommendations to the referring physicians/surgeons. This review proposes an empirically supported model for PPEs that is systematic, but flexible enough to be utilized across the broad range of surgical evaluations. This five-step method is termed the Risk Identification and Mitigation (RIM) model and is discussed in detail. The RIM model presented in this review can both serve as a structure to be utilized in under-researched PPE areas and as a stimulus for future empirical investigations.