RESUMO
INTRODUCTION: Spinal neurostimulation is a therapy for otherwise intractable chronic pain. Spinal neurostimulation includes stimulation of the spinal cord (SCS), dorsal root ganglion (DRGS), and dorsal root entry zone (DREZS). New paresthesia-free neurostimulation paradigms may rely on different mechanisms of action from those of conventional tonic neurostimulation. The aim of this systematic review is to assess the existing knowledge on the effect of spinal neurostimulation on somatosensory processing in patients with chronic pain. We therefore reviewed the existing literature on the effect of various spinal neurostimulation paradigms on the supraspinal somatosensory evoked response (SER). MATERIALS AND METHODS: Multiple scientific data bases were searched for studies that assessed the effect of spinal neurostimulation on the supraspinal SER, evoked by painful or nonpainful peripheral stimuli in patients with chronic pain. We found 205 studies, of which 24 were included. Demographic data, study design, and study outcome were extracted. RESULTS: Of the 24 included studies, 23 used electroencephalography to assess the SER; one study used magnetoencephalography. Fifteen studies evaluated tonic SCS; six studies (also) evaluated paresthesia-free paradigms; three studies evaluated the effect of tonic DRGS or DREZS. Sixteen studies used nonpainful stimuli to elicit the SER, 14 observed a decreased SER amplitude. Ten studies used painful stimuli to elicit the SER, yielding mixed results. DISCUSSION: The included studies suggest that both paresthesia-based and paresthesia-free spinal neurostimulation paradigms can decrease (part of) the SER elicited by a nonpainful peripheral stimulus. The observed SER amplitude reduction likely is the effect of various spinal and supraspinal mechanisms of spinal neurostimulation that also contribute to pain relief. CONCLUSIONS: Spinal neurostimulation modulates the processing of a peripherally applied nonpainful stimulus. For painful stimuli, the results are not conclusive. It is not yet clear whether paresthesia-free neurostimulation affects the SER differently from paresthesia-based neurostimulation.
Assuntos
Potenciais Somatossensoriais Evocados , Estimulação da Medula Espinal , Humanos , Potenciais Somatossensoriais Evocados/fisiologia , Estimulação da Medula Espinal/métodos , Medula Espinal/fisiologia , Dor Crônica/terapia , Dor Crônica/fisiopatologiaRESUMO
The performance of time-series classification of electroencephalographic data varies strongly across experimental paradigms and study participants. Reasons are task-dependent differences in neuronal processing and seemingly random variations between subjects, amongst others. The effect of data pre-processing techniques to ameliorate these challenges is relatively little studied. Here, the influence of spatial filter optimization methods and non-linear data transformation on time-series classification performance is analyzed by the example of high-frequency somatosensory evoked responses. This is a model paradigm for the analysis of high-frequency electroencephalography data at a very low signal-to-noise ratio, which emphasizes the differences of the explored methods. For the utilized data, it was found that the individual signal-to-noise ratio explained up to 74% of the performance differences between subjects. While data pre-processing was shown to increase average time-series classification performance, it could not fully compensate the signal-to-noise ratio differences between the subjects. This study proposes an algorithm to prototype and benchmark pre-processing pipelines for a paradigm and data set at hand. Extreme learning machines, Random Forest, and Logistic Regression can be used quickly to compare a set of potentially suitable pipelines. For subsequent classification, however, machine learning models were shown to provide better accuracy.
Assuntos
Algoritmos , Eletroencefalografia , Humanos , Eletroencefalografia/métodos , Algoritmo Florestas Aleatórias , Extremidade Superior , Razão Sinal-Ruído , Processamento de Sinais Assistido por ComputadorRESUMO
OBJECTIVE: The aim of the study was to investigate the functional differences between N20m and P30m components of somatosensory-evoked magnetic cortical field (SEF) in young and senior subjects. METHODS: Twenty-nine healthy subjects, 13 younger (mean age: 21.8years) and 16 senior (63.8 years), participated. Magnetic fields were measured using a 160-channel, whole head MEG. Single- and paired-pulse stimulations of 200 artifact-free MEG signal epochs were averaged separately. We calculated how aging affects recovery function of SEFs. RESULTS: The senior showed a prolonged N20m peak latency compared to the younger, although the P30m peak latency was not significantly different between groups. The N20m ratios at 60 and 80 ms in the senior were significantly increased compared to the ratios in the younger (60 ms: P<0.05, 80 ms: P<0.001). The P30m ratios at inter-stimulus interval (ISI) of 80 and 100 ms showed even disinhibition in the senior than in the younger (P<0.05). The younger also showed a significantly negative correlation between P30m and N20m components' recovery curves (R=0.72, P<0.05). CONCLUSION: Aging-related changes that occurred in recovery functioning were the decrease in N20m component suppression and the increase in P30m component recovery, indicating that the N20m and P30m components have different functions in aging-related recovery changes. SIGNIFICANCE: Our results show that the N20m ratio at an ISI of 80 ms was significantly increased in the senior group, indicating that the second stimulus-evoked SEF was less inhibited by the initial stimulus at this ISI, suggesting less refractory effect or increased disinhibition.