Movement and pain in fibromyalgia: a co-registration by fNIRS and LEPs

Recent studies by non-invasive stimulation techniques suggested a possible alteration in cortical excitability of motor area in chronic pain patients. However, physical exercise is indicated in the treatment of pain [1]. The complex mechanism of interaction between the motor cortex and pain matrix is not completely clear. Functional Near-Infrared Spectroscopy (fNIRS) is an optical and non-invasive method to monitor brain activity. FNIRS is suitable to measure variations in hemoglobin concentration. The present study aimed to investigate the hemodynamic activity and laser evoked potentials (LEPs) variations during both slow and fast finger tapping task and concomitant painful stimulation on the right and left back hand. We recruited 20 healthy subjects and 35 fibromyalgia patients. A co-registration by fNIRS and LEPs was used to explore motor cortex activation and nociceptive pathways. FNIRS data showed a reduction in motor cortical activation both in movement condition than during concomitant laser stimulation in both hands in FM group compared to controls. There was a slight reduction in N1 amplitude during movement in both groups. Patients presented a strengthening of N2P2 vertex complex during motion unlike the controls. We suggested a possible abnormal interference circuit between motor and pain systems in FM patients.