Somatosensory cortex stimulation for deafferentation pain

Functional neuroimaging has demonstrated that a relationship exists between the intensity of deafferentation pain and the degree of deafferentation-related reorganization of the primary somatosensory cortex. It has also revealed that this cortical reorganization can be reversed after the attenuation of pain. Deafferentation pain is also associated with hyperactivity of the somatosensory thalamus and cortex. Therefore, in order to suppress pain, it seems logical to attempt to modify this deafferentation-related somatosensory cortex hyperactivity and reorganization. This can be achieved using neuronavigation-guided transcranial magnetic stimulation (TMS), a technique that is capable of modulating cortical activity. If TMS is capable of suppressing deafferentation pain, this benefit should be also obtained by the implantation of epidural stimulating electrodes over the area of electrophysiological signal abnormality in the primary somatosensory cortex. The first studies demonstrated a statistically significant pain suppression in all patients and a clinically significant pain suppression in 80% of them. This clinical experience suggests that somatosensory cortex stimulation may become a neurophysiology-based new approach for treating deafferentation pain in selected patients. In this chapter, we review the relevant recent reports and describe our studies in this field.