Capítulo I. Población estudiantil
I.III Procesos y resultados educativos
Exact electrode localisation and precise methods for coordinate identification are important factors to compare the outcome of SNr-DBS. To investigate whether there is an interrelation between the determined electrode coordinates and the FOG outcome, we calculated the correlation between the single electrode coordinates, the x-, y- and z-coordinate, and the change of the FOG outcome of the FOG-AC during the ‘immediate testing’ phase (Δ StimOff - [STN+SNr]) for all active electrode contacts.
Figure 53 to Figure 64 show that there is no strong positive or negative correlation between our determined electrode coordinates and the FOG outcome. All results were statistically non-significant. The coefficient of correlation (r) ranged from -0,19 to 0.5.
Figure 51 Box plots of PDQ-39,
‘communication’ domain.
x-axis = therapeutic condition, y-axis = score, [STNmono] = standard STN stimulation, [STN+SNr] = combined STN and SNr stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata.
Figure 52 Box plots of PDQ-39, ‘bodily
discomfort’ domain.
x-axis = therapeutic condition, y-axis = score, [STNmono] = standard STN stimulation, [STN+SNr] = combined STN and SNr stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata.
85 Left SNr
Right SNr
Figure 53 Correlation between the x-coordinate of the left SNr and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 54 Correlation between the y-coordinate of the left SNr and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 55 Correlation between the z-coordinate of the left SNr and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 56 Correlation between the x-coordinate of the right SNr and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 57 Correlation between the y-coordinate of the right SNr and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
86 Left STN
Figure 58 Correlation between the z-coordinate of the right SNr and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 59 Correlation between the x-coordinate of the left STN and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 60 Correlation between the y-coordinate of the left STN and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 61 Correlation between the z-coordinate of the left STN and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
87 Right STN
Safety measures
No suicidality was reported in any patient (Weiss et al., 2013). On group level, no change was found concerning the BDI. During [STN+SNr], PD1 presented with increased BDI scores compared to [STNmono]. The score after the ‘3-week follow-up’ in the [STN+SNr] condition was 18 and after three weeks of constant [STNmono] stimulation 7. PD7 had a former personal history of hallucinations, which was documented in the preoperative recordings, and he developed visual benign hallucinations with retained insight (item 2, UPDRS I) during the [STN+SNr] condition. At group level, item 2 of the UPDRS I was unchanged Figure 62 Correlation between the x-coordinate
of the right STN and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 63 Correlation between the y-coordinate of the right STN and the FOG outcome.
[STN+SNr] = combined STN and SN
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
Figure 64 Correlation between the z-coordinate of the right STN and the FOG outcome.
[STN+SNr] = combined STN and SNr
stimulation, STN = subthalamic nucleus, SNr = substantia nigra pars reticulata, r = correlation coefficient.
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between the two therapeutic conditions. Psychosis did not occur in any patient. Concerning the evaluation of the BIS, the segmental symptoms (items 20-26, UPDRS III) and motor fluctuations (UPDRS IV), the comparison of [STN+SNr] and [STNmono] showed no difference between the two treatments.
Adverse events
Before entering the study, several strategies were applied to optimise the efficacy of DBS, such as the optimisation of the electrode geometry and the programming of the electrodes by titration of subthalamic and nigral stimulation parameters. Effects and side effects were carefully evaluated. Nevertheless, control over the current spread during the stimulation is limited (Kringelbach et al., 2007).
Despite the best effort of minimizing the chance of occurring adverse events, the probability of the appearance of any side effects is high, hence an accurate observation and reporting of these effects is greatly important for the interpretation of the clinical applicability of the evaluated therapeutic strategy. Our patients were instructed to be watchful concerning side effects and to report them to the study site as soon as they occur during the ‘3-week follow-up’. In the final analysis, no serious adverse events were observed in both treatment arms. During [STN+SNr] treatment, no acute side effects were observed in the ‘immediate testing’ but during the ‘3-week follow-up’ four adverse events were reported. Two patients (PD2 and PD 9) suffered from a delayed onset of relevant dyskinesias within the first days after introduction of [STN+SNr]. PD2 came on day two after the introduction of [STN+SNr] and required therapy adjustment according to the intention-to-treat principle. The stimulation amplitudes were lowered on both active caudal contacts, the SNr-contacts by -0.4V and the symptoms resolved completely within a short time. PD9 informed the study site for therapy adjustment after he had already independently conducted a self- administered reduction of the daily levodopa dosage by 125 mg. This reduction ameliorated the dyskinesias but as they did not disappear completely, the patient was rescheduled and the SNr amplitudes were additionally lowered by -0.1V on both sides. After these interventions, the dyskinesias completely
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resolved in both patients and they could stick to the schedule and completed the ‘3-week follow-up’ period according to the intention-to-treat-principle.
At the ‘3-week follow-up’ visit, one patient (PD 8) reported that few intermittent episodes of double vision occurred during the [STN+SNr] condition. They lasted for a few seconds and were not highly bothersome for the patient, hence the patient did not contact the study site before the ‘3-week follow-up’ visit.
PD7 and his caregiver reported an initial improvement of FOG during the first two weeks of the [STN+SNr] condition, however increased immobility and recurrent falls occurred during the third week of the ‘3-week follow-up’.
Four patients wished to discontinue standard STN stimulation [STNmono] prematurely (PD3, PD7, PD10, PD11) due to more pronounced gait impairment, immobility and falls. No patient discontinued the ‘3-week follow-up’ prematurely during the [STN+SNr] condition (Weiss et al., 2013).
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