The impact of bilateral subthalamic deep brain stimulation on long-latency event-related potentials

The analysis of long-latency event-related potentials (ERPs) is of importance in the evaluation of certain cognitive functions and in following their subsequent changes. The aim of the present study was to investigate whether deep brain stimulation (DBS) itself can cause changes in the configuration of the ERPs. Using a standard oddball auditory paradigm, we elicited auditory cognitive ERPs in 23 Parkinson's disease patients (in both DBS-ON and DBS-OFF conditions) and in 14 healthy controls. The P200 and P300 amplitudes and latencies, the motor reaction times and the accuracy of button pressing were compared between the DBS-ON and DBS-OFF states and subsequently correlated with the applied stimulation voltage and disease duration. Comparison of the DBS-ON and DBS-OFF conditions revealed that neither the amplitude nor the latency of the examined ERP components changed significantly. However, the behavioral and attentional aspects (e.g. the accuracy of the button pressing responses to the target signal) definitely improved after the DBS was turned on. Positive correlations were demonstrated between the P300 amplitudes over the central and frontal regions and the optimal stimulation voltage and between the disease duration and P300 latencies over the Cz and Fz sites. In conclusion, our data indicate that DBS may have different impacts on various electrophysiological parameters during the oddball paradigm.     

Long descending direct projection from the basal ganglia to the spinal cord: a revival of the extrapyramidal concept

Our retrograde fluorescent labeling study shows that a distinct cell group of the subthalamic nucleus, posited in the basal ganglia, directly sends long descending axons contralaterally to the upper cervical segments (C1-C5) of the spinal cord in the rat. A large population (60-70%) of these subthalamic cells projecting to contralateral spinal levels give off axonal branches innervating the ipsilateral globus pallidus. Now, the classical concept of the 'extrapyramidal' motor system needs to be reconsidered. Furthermore, our results may provide a morphological substrate for the onset of a violent form of dyskinesia, 'hemiballism', which occurs in the contralateral limbs both clinically and experimentally following discrete lesions in the subthalamic nucleus or its fiber connections with the globus pallidus.     

Basal ganglia deep-brain stimulation for treatment of drug-resistant epilepsy: review and current data

The surgical treatment of intractable epilepsies involving eloquent areas of the cortex is still challenging. Deep-brain stimulation could be an alternative to resective surgery because it can modulate the remote control systems of epilepsy, such as the thalamus and basal ganglia. The surgical experience acquired in the field of movement disorder surgery and the low morbidity of this technic could allow one to apply DBS to intractable epilepsies, such as generalized, motor and bitemporal epilepsies. Here we discuss the main experimental and clinical data reported so far in the literature and taken from our own experience.     

Bilateral deep brain stimulation of the subthalamic nucleus: Targeting differences between the first and second side

Introduction and objectivesDeep brain stimulation (DBS) of the subthalamic nucleus (STN) is a recognized treatment for drug-refractory Parkinson's disease (PD). However, the therapeutic success depends on the accuracy of targeting. This study aimed to evaluate potential accuracy differences in the placement of the first and second electrodes implanted, by comparing chosen electrode trajectories, STN activity detected during microelectrode recording (MER), and the mismatch between the initially planned and final electrode positions on each side.Materials and methodsIn this retrospective cohort study, we analyzed data from 30 patients who underwent one-stage bilateral DBS. For most patients, three arrays of microelectrodes were used to determine the physiological location of the STN. Final target location depended also on the results of intraoperative stimulation. The choice of central versus non-central channels was compared. The Euclidean vector deviation was calculated using the initially planned coordinates and the final position of the tip of the electrode according to a CT scan taken at least a month after the surgery.ResultsThe central channel was chosen in 70% of cases on the first side and 40% of cases on the second side. The mean length of high-quality STN activity recorded in the central channel was longer on the first side than the second (3.07 ± 1.85 mm vs. 2.75 ± 1.94 mm), while in the anterior channel there were better MER recordings on the second side (1.59 ± 2.07 mm on the first side vs. 2.78 ± 2.14 mm on the second). Regarding the mismatch between planned versus final electrode position, electrodes on the first side were placed on average 0.178 ± 0.917 mm lateral, 0.126 ± 1.10 mm posterior and 1.48 ± 1.64 mm inferior to the planned target, while the electrodes placed on the second side were 0.251 ± 1.08 mm medial, 0.355 ± 1.29 mm anterior and 2.26 ± 1.47 mm inferior to the planned target.ConclusionThere was a tendency for the anterior trajectory to be chosen more frequently than the central on the second side. There was also a statistically significant deviation of the second electrodes in the anterior and inferior directions, when compared to the electrodes on the first side, suggesting that another cause other than brain shift may be responsible. We should therefore factor this during planning for the second implanted side. It might be useful to plan the second side more anteriorly, possibly reducing the number of MER trajectories tested and the duration of surgery.     

Does subthalamic nucleus deep brain stimulation affect the static balance at different frequencies?

PurposeTo investigate the effects of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) with different stimulation frequencies on static balance.Materials and methodsTwenty patients (15 males and 5 females), aged between 43 and 81 (mean: 60.05 ± 7.4) years, who had been diagnosed with idiopathic Parkinson's disease (PD) and undergone STN-DBS surgery were included in the study. Static balance was assessed with TecnoBody Rehabilitation System at four different frequencies: 230, 130, 90 and 60 Hz and off-stimulation. Static balance tests were ‘stabilometric test, stabilometric compared bipedal closed/opened eye, stabilometric compared mono pedal (right/left foot)’. These tests reported the centre of pressure data ‘ellipse area, perimeter, front/back and mediolateral standard deviations’.ResultsThere were no statically differences between the static balance test results at any frequency (p > 0.05), but results were found better at 90 Hz. Stabilometric compared bipedal opened eye forward–backward standard deviation result was significant between off-stimulation and 130 Hz (p = 0.04). Different frequency stimulation affected the static balance categories percentage with no statistical significance between off-stimulation and others (all p > 0.05).ConclusionThis study showed that STN-DBS did not affect the static balance negatively. Low-frequency (LF) stimulation improved the static equilibrium. Posturography systems will give more precise and quantitative results in similar studies with wide frequency ranges.