Electrostimulation of the white matter of the posterior insula and medial operculum: perception of vibrations, heat, and pain

Abstract

This study aimed to characterize the sensory responses observed when electrically stimulating the white matter surrounding the posterior insula and medial operculum (PIMO). We reviewed patients operated on under awake conditions for a glioma located in the temporoparietal junction. Patients' perceptions were retrieved from operative reports. Stimulation points were registered in the Montreal Neurological Institute template. A total of 12 stimulation points in 8 patients were analyzed. Painful sensations in the contralateral leg were reported (5 sites in 5 patients) when stimulating the white matter close to the parcel OP2/3 of the Glasser atlas. Pain had diverse qualities: burning, tingling, crushing, or electric shock. More laterally, in the white matter of OP1, pain and heat sensations in the upper part of the body were described (5 sites in 2 patients). Intermingled with these sites, vibration sensations were also reported (3 sites in 2 patients). Based on the tractograms of 44 subjects from the Human Connectome Project data set, we built a template of the pathways linking the thalamus to OP2/3 and OP1. Pain sites were located in the thalamo-OP2/3 and thalamo-OP1 tracts. Heat sites were located in the thalamo-OP1 tract. In the 227 awake surgeries performed for a tumor located outside of the PIMO region, no patients ever reported pain or heat sensations when stimulating the white matter. Thus, we propose that the thalamo-PIMO connections constitute the main cortical inputs for nociception and thermoception and emphasize that preserving these fibers is of utmost importance to prevent the postoperative onset of a debilitating insulo-opercular pain syndrome.

Low-intensity focused ultrasound to the human insular cortex differentially modulates the heartbeat-evoked potential: a proof-of-concept study

“…Afferent information from internal organs travel via the vagus and glossopharyngeal nerves to the brainstem and thalamic targets and integrate with lamina I spinothalamic projections before relaying to the insula and dorsal anterior cingulate cortex (dACC) [1,2,[6][7][8][9]. Both the PI and the dACC receive direct afferent interoceptive information through two distinct thalamic nuclei while the AI communicates with PI and dACC without directly receiving this information, suggesting complementary but specific roles in interoceptive processing [1,7,[10][11][12]. This makes the insular subregions and the dACC intriguing targets for both the pathophysiologic investigation and neuromodulation therapies across a range of mental health and chronic pain conditions that may involve brain-body dysregulation [13][14][15][16][17][18][19].…”