Abstract
Chronic visceral pain (CVP) syndromes are persistently painful disorders with a remarkable lack of effective treatment options. This study aimed at evaluating the effects of different neuromodulation techniques in patients with CVP on cortical activity, through electreocephalography (EEG) and on pain perception, through clinical tests. A pilot crossover randomized controlled study. Out-patient. Adults with CVP (>3 months). Participants received four interventions in a randomized order: (1) transcranial pulsed current stimulation (tPCS) and active transcranial direct current stimulation (tDCS) combined, (2) tPCS alone, (3) tDCS alone, and (4) sham condition. Resting state quantitative electroencephalography (qEEG) and pain assessments were performed before and after each intervention. Results were compared with a cohort of 47 healthy controls. We enrolled six patients with CVP for a total of 21 visits completed. Compared with healthy participants, patients with CVP showed altered cortical activity characterized by increased power in theta, alpha and beta bands, and a significant reduction in the alpha/beta ratio. Regarding tES, the combination of tDCS with tPCS had no effect on power in any of the bandwidths, nor brain regions. Comparing tPCS with tDCS alone, we found that tPCS induced higher increase in power within the theta and alpha bandwidths. This study confirms that patients with CVP present abnormal EEG-indexed cortical activity compared with healthy controls. Moreover, we showed that combining two types of neurostimulation techniques had no effect, whereas the two interventions, when applied individually, have different neural signatures.
Highlights
Visceral pain results from nociceptor activation in thoracic, pelvic, or abdominal visceral organs [1]
Chronic visceral pain patients and healthy controls (HCs) were similar for age (t = 0.885; p = 0.432), gender (χ2 = 0.24; p = 0.622), and level of education (t = 2.47; p = 0.122)
The present study yielded interesting findings: [1] patients with chronic visceral pain (CVP) display abnormal neural activity compared with healthy controls, as indexed by Quantitative Electroencephalography (qEEG); [2] EEG captured cortical changes following tES, similar to what was observed in healthy controls, while no clinical improvement was noticed; [3] combining tDCS with tPCS does not induce specific changes in neural activity; [4] tDCS and tPCS have different neural signature
Summary
Visceral pain results from nociceptor activation in thoracic, pelvic, or abdominal visceral organs [1]. While acute pain has the vital role of preventing tissue damage, maladaptive processes may convert it into chronic [2], leading to chronic visceral pain (CVP), a condition featured by several maladaptive neural changes, one of them being central sensitization [3]. Simis et al showed that patients with pelvic pain had significantly lower levels of N-acetylaspartate (NAA) and creatinophosphocreatine (Cr), reflecting loss of neuronal integrity in the primary motor cortex compared with healthy participants. This evidence highlights the process of maladaptive plasticity in neural circuits involved in pain modulation [6]. The investigation of cortical oscillation patterns by means of electroencephalography (EEG) is still at its infancy in patients with CVP
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