Theoretically 'best' electrode configurations in SCS for chronic back pain and clinical experience: do they match ? Preliminary results of a prospective study.

Abstract

Introduction: Stimulation of the greater occipital nerve (C2) might have a beneficial effect in occipital neuralgia, primary headache syndromes and fibromyalgia. Possible explanations can be found in the connection with neurons of the trigeminal nerve in the Trigemino-Cervical complex. However, PET data have shown differences in brain activation during stimulation, as did unpublished fMRI results by the authors. LORETA imaging results during occipital nerve stimulation are presented, showing differences in cortical activation in a group of fibromyalgia patients. Materials and methods: 9 patients, suffering from fibromyalgia were implanted with a greater occipital nerve stimulator in order to treat their pain. EEG recordings were acquired in the following situations: a) a stimulation off b) stimulation at effective treatment settings c) stimulation at non-effective treatment settings. The EEGs were recorded with a 19-channel EEG according to the 19/20 system, 500Hz sampling rate, eyes closed situation. After artifact removal, including removal of the stimulation artifact by independent component analysis (ICA) Current Source Densities were calculated using sLORETA and t-within tests were performed. Results: Significant results were found in the comparison between the measurements during stimulation and without stimulation. The following cortical regions were involved: cingulate gyrus, somatosensory cortex, hippocampal area and insula. Conclusion: These results show differences in cortical current source density during stimulation. This might suggest that subcutaneous stimulation of the greater occipital nerve, not only influences the peripheral nervous system, but the central nervous system as well. Further research including functional MR imaging and PET-scan data combined with EEG data might be useful to verify these and extend these results to subcortical structures.