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Makoto Terumitsu,1,2 Yuhei Takado,3 Ken-Ichi Fukuda,2 Eisuke Kato,2 Sei Tanaka4 1Division of Dental Anesthesiology, Department of Human Biology and Pathophysiology, Health Sciences University of Hokkaido, Hokkaido, Japan; 2Division of Special Needs Dentistry and Orofacial Pain, Department of Oral Health and Clinical Science, Tokyo Dental College, Tokyo, Japan; 3Department of Functional Brain Imaging, Institute of Quantum Medical Sciences, National Institutes for Quantum Science and Technology, Chiba, Japan; 4Department of Oral and Maxillofacial Surgery, Tokyo Dental College, Tokyo, JapanCorrespondence: Makoto Terumitsu, Division of Dental Anesthesiology, Department of Human Biology and Pathophysiology, Health Sciences University of Hokkaido, 1757 Kanazawa, Tobetsu-cho, Ishikari-gun, Hokkaido, 061-0293, Japan, Tel/Fax +81 133 23 1445, Email terumitsu@hoku-iryo-u.ac.jpBackground: Refractory chronic pain in the orofacial region involves central sensitization (CS). However, not all chronic pain patients exhibit CS. An objective assessment of CS may be useful for pain management. Changes in the balance of excitatory and inhibitory neural activity or excessive activity of nerves and glial cells may cause CS and contribute to pain chronification.Patients and Methods: 1H-magnetic resonance spectra were acquired from the anterior cingulate cortex (ACC) and thalamus in 20 patients with chronic orofacial pain and suspected CS, and 21 healthy volunteers, using a single-voxel point-resolved spectroscopy sequence. The patients were assessed using the Central Sensitization Inventory.Results: Aspartate/total creatine (tCr) and glutathione in the ACC were significantly higher in the patient group. However, no significant difference was observed between groups in the neurometabolites measured in the thalamus. Patients also exhibited a tendency for increased gamma-aminobutyric acid (GABA)/tCr in the ACC. There were positive relationships between Central Sensitization Inventory scores and glutamate + glutamine (Glx) in the thalamus, a positive trend for Glx in the ACC and a negative relationship for GABA/tCr in the ACC.Conclusion: The high levels of aspartate/tCr and glutathione in the patient group suggest excitatory neuronal activity and hyperactivity of neurons and glial cells. The correlation analysis results suggest that excitatory and inhibitory neurometabolites are involved in the chronification of orofacial pain, including CS.Keywords: orofacial pain, central sensitization, magnetic resonance spectroscopy, Central Sensitization Inventory, anterior cingulate cortex, thalamus |
