Electrical stimulation of motor cortex for pain control: a combined PET-scan and electrophysiological study

Abstract

Although electrical stimulation of the precentral gyrus (MCS) is emerging as a promising technique for pain control, its mechanisms of action remain obscure, and its application largely empirical. Using positron emission tomography (PET) we studied regional changes in cerebral flood flow (rCBF) in 10 patients undergoing motor cortex stimulation for pain control, seven of whom also underwent somatosensory evoked potentials and nociceptive spinal reflex recordings. The most significant MCS-related increase in rCBF concerned the ventral-lateral thalamus, probably reflecting cortico-thalamic connections from motor areas. CBF increases were also observed in medial thalamus, anterior cingulate/orbitofrontal cortex, anterior insula and upper brainstem; conversely, no significant CBF changes appeared in motor areas beneath the stimulating electrode. Somatosensory evoked potentials from SI remained stable during MCS, and no rCBF changes were observed in somatosensory cortex during the procedure. Our results suggest that descending axons, rather than apical dendrites, are primarily activated by MCS, and highlight the thalamus as the key structure mediating functional MCS effects. A model of MCS action is proposed, whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in pain-related structures receiving afferents from these nuclei, including the medial thalamus, anterior cingulate and upper brainstem. MCS could influence the affective-emotional component of chronic pain by way of cingulate/orbitofrontal activation, and lead to descending inhibition of pain impulses by activation of the brainstem, also suggested by attenuation of spinal flexion reflexes. In contrast, the hypothesis of somatosensory cortex activation by MCS could not be confirmed by our results.

The neural correlates of maternal and romantic love

“…The activity obtained in that study overlaps precisely with that obtained here with both maternal and romantic love and may well reflect this sensory -emotive component that is common to and crucial for such caring relationships (Harlow, 1958). By contrast, the anterior part of the insula (not activated here) contains a distinct functional subdivision, and is consistently activated by negative stimuli (Augustine, 1996;Buchel et al, 1998;Coghill et al, 1994;Garcia-Larrea et al, 1999;Kosslyn et al, 1996;Phillips et al, 1997).…”

Imagerie fonctionnelle cérébrale appliquée à l’analyse des phénomènes douloureux

“…D'autres équipes ont inventorié les réponses des patients atteints de douleurs rhumatismales, de fibromyalgie, d'algodystrophie, de syndrome de l'intestin irritable et d'autres situations de douleurs chro-ne concernaient pas les aires à proximité de l'électrode mais plutôt les aires à distance dans le thalamus, le cortex cingulaire rostral ou la SGPA [47][48][49], et que les activités dans ces deux dernières aires étaient corrélées à l'effet antalgique [49]. Ces données nous ont rappelé que la neurostimulation de la SGPA avait été développée, de manière empirique elle aussi, avec certains succès thérapeutiques, dans les années 1950, et que le cortex cingulaire rostral pouvait être considéré comme une cible potentielle pour la neurostimulation de ces patients.…”

Effectiveness of transcranial direct current stimulation for the management of neuropathic pain after spinal cord injury: a meta-analysis

“…12 The mechanism by which tDCS is able to relieve pain is not entirely known; however, it is believed that tDCS may improve pain processing due to a modulatory effect on central pathways, the same pathways targeted by antidepressant pharmacotherapy. 11,[13][14] Given the refractory nature of NP in a post SCI population, it is important to uncover new modalities for treatment. Until recently, there were too few studies evaluating the effectiveness of tDCS for NP among individuals post SCI; however, an increase in interest in this field has led to several new studies to assess.…”