Behavioural changes after bilateral subthalamic stimulation in advanced Parkinson disease: A systematic review

Abstract

Introduction.

The long-lasting beneficial effects of subthalamic nucleus (STN) deep brain stimulation (DBS) on motor function have now largely been acknowledged. Whereas behavioural changes have been demonstrated in certain case reports and small case series, some authors have not observed behavioural changes at all. The extent to which these changes occur has not yet been established. The aim of the present study was to systematically analyse behavioural changes of bilateral STN DBS.

Materials and methods.

A structured Medline search was conducted using previously described methods. Studies were selected according to specific in- and exclusion criteria. Data on patients, surgical technique, outcome and complications were collected and pooled.

Results.

In total 1398 patients who underwent bilateral STN DBS were included. The total cumulative follow-up period was 1480 patient-years. Cognitive problems were seen in 41%, depression in 8%, and (hypo)mania in 4% of the patients. Anxiety disorders were observed in less than 2%, and personality changes, hypersexuality, apathy, anxiety, and aggressiveness were observed in less than 0.5% of the group studied. About half of the patients did not experience behavioural changes.

Conclusion.

Caregivers should be aware of the extent of these behavioural changes and a risk/benefit evaluation should be performed for individual patients.

Introduction

Bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN), once considered an experimental treatment, is nowadays widely performed in the treatment of advanced Parkinson disease (PD). Many studies have appeared on the short-term effects [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. More recently, four-year [11], [12] and 5 year follow-up [13] effects were reported. Bilateral STN stimulation induced a marked improvement in motor function while off medication and in dyskinesia while on medication. These results reinforce the value of bilateral STN DBS in the long-term treatment of advanced Parkinson disease. On the other hand, STN DBS is accompanied by a new set of side effects and complications, which may occur at any time from surgery to several years postoperatively [14], [15]. These negative effects can be related to the hardware such as infections [14], lead fracture [16], dislocation [17], to the electrode insertion (bleedings) or specifically to the region stimulated [18], [19], [20], [21], [22].

In several case reports and small case series, behavioural changes following STN DBS have been described such as mania [18], [19], [23], [24], depression [6], [10], [13], [21], [22], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37] and cognitive alterations [6], [15], [20], [24], [29], [30], [38], [39], [40], [41], [42]. On the other hand, other authors did not find any negative effect of STN DBS on behaviour [43], [44], [45], [46], [47]. There is an ongoing debate about which specific behavioural changes are related to bilateral STN DBS and to what extent these occur. In the present study, our aim was to systematically analyse these side-effects in reports describing original data on bilateral STN stimulation in advanced PD.