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OBJECTIVE: A growing number of studies are showing positive effects of deep brain stimulation (DBS) in the caudal zona incerta (cZi) in various tremor disorders, as well as motor symptoms of Parkinson’s disease (PD). The focus of the present study was to evaluate short- and long-term cognitive effects of bilateral cZi DBS in patients with PD.

METHODS: Twenty-five nondemented patients with advanced PD were recruited to participate in a randomized trial of cZi DBS versus best medical treatment (BMT). The patients in the BMT group were offered surgery after 6 months. Neuropsychological evaluations focusing on assessing verbal and visuospatial memory, attention, and executive function were conducted at baseline and at 6 and 24 months after surgery. Self-reported measures of depression, anxiety, and change in "frontal" behaviors were also completed at all assessment points.

RESULTS: Bilateral cZi DBS in patients with PD generated few adverse cognitive effects. At the short-term follow-up after 6 months, no differences were found between patients randomized to BMT and patients randomized to DBS with regard to most of the cognitive domains assessed. A transient improvement in anxiety was, however, found in the surgical group. At the long-term follow-up 24 months after cZi DBS, no major changes in global cognitive functioning were found, although a decline in attention and self-reported executive function was noted.

CONCLUSIONS: With the exception of a decline in attention and self-reported executive function, bilateral cZi DBS for PD in appropriately screened patients appears to be generally safe with regard to cognitive function, both in the short- and long-term perspective.

OBJECTIVE: The ventral intermediate nucleus (VIM) of the thalamus is currently the established target in the use of deep brain stimulation (DBS) to treat essential tremor (ET). In recent years, the caudal zona incerta (cZi), a brain target commonly used during the lesional era, has been revived as the primary target in a number of DBS studies that show evidence of the efficacy of cZi targeting in DBS treatment for controlling the symptoms of ET. The authors sought to obtain comprehensive neuropsychological data and thoroughly investigate the cognitive effects of cZi targeting in patients with ET treated with DBS.

METHODS: Twenty-six consecutive patients with ET who received DBS with cZi as the target at our department from December 2012 to February 2017 were included in this study. All patients were assessed using a comprehensive neuropsychological test battery covering the major cognitive domains both preoperatively and 12 months postoperatively.

RESULTS: The results show no major adverse effects on patient performance on the tests of cognitive function other than a slight decline of semantic verbal fluency.

CONCLUSIONS: This study indicates that the cZi is a safe target from a cognitive perspective in the treatment of ET with DBS.

Essential tremor (ET) is characterized by bilateral upper limb postural and/or kinetic tremor, but also cognitive deficits. Tremor in ET, as well as aspects of cognitive deficits associated with ET, have been suggested to be linked to dysfunction in the cerebello-thalamo-cerebral circuit. In ET patients with disabling and medically intractable motor symptoms, Deep Brain Stimulation (DBS) is effective in reducing tremor. DBS in the caudal Zona incerta (cZi) has been shown to modulate the activity of the sensorimotor cerebello-cerebral circuit during motor tasks. Whether the activity in the cerebello-cerebral circuit is modulated by DBS during tasks involving working memory is unknown. The present study therefore aimed to investigate the possible effects of cZi DBS on working-memory processing in ET patients by means of task-based blood oxygen level-dependent (BOLD) fMRI.

Thirteen ET patients completed a working-memory task during DBS OFF and ON conditions. The task involved three conditions: maintenance, manipulation, and control. Behaviorally, there was no significant effect from DBS on accuracy, but a marginally significant Task x DBS interaction was detected for response times (RTs). However, post hoc comparisons for each condition failed to reach statistical significance. FMRI analyses revealed that DBS did not alter BOLD signal in regions of interest (lateral prefrontal cortex, parietal cortex, and the cerebellum), or in a complementary whole-brain analysis.

The present study indicates that DBS in the cZi in patients with ET has at most marginal effects on working memory, which is consistent with the results of pre- and post-DBS neuropsychological assessment showing minimal cognitive effects of surgery.

Purpose: The aim of this study was to evaluate cognitive effects 12 months after Deep Brain Stimulation (DBS) of the Bed Nucleus of Stria Terminalis (BNST) in patients with refractory Obsessive–Compulsive Disorder (OCD).

Methods: Eight patients (5 female; mean ± SD age 36 ± 15) with OCD were included. A neuropsychological test battery covering verbal and spatial episodic memory, executive function, and attention was administered preoperatively and 12 months after surgery. Medical records were used as a source for descriptive data to probe for any changes not covered by standardized checklists and the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the primary outcome measure.

Results: At 12 months, seven patients showed response to DBS: three were full responders (i.e., Y-BOCS ≥ 35% improvement), and four were partial responders (Y-BOCS 25–34% improvement). Relative to baseline, there was a slight decline on visuo-spatial learning (p = 0.027), and improved performance on the Color-Word Interference inhibition/switching subtest (p = 0.041), suggesting improvement in cognitive flexibility.

Conclusions: DBS in the BNST for treatment refractory OCD generates very few adverse cognitive effects and improves cognitive flexibility after 12 months of stimulation. The improvement in Y-BOCS and the absence of major cognitive side effects support the BNST as a potential target for DBS in severe OCD.