Difference between revisions of "Trigeminal Nociceptive Evaluation in TMD Patients by studying CO2-Laser Evoked Potentials and Masseter Laser Silent Periods"

Trigeminal Nociceptive Evaluation in TMD Patients by studying CO2-Laser Evoked Potentials and Masseter Laser Silent Periods (view source)

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-Temporomandibular dysfunction (TMD) comprises a group of painful conditions affecting the masticatory muscles and temporomandibular joint (TMJ). Despite extensive research, the pathophysiology and etiology of TMD remain unclear, with hypotheses largely unproven. Electromyographic (EMG) studies have identified alterations in the voluntary or reflex activity of the masticatory muscles in TMD patients, though these findings have not provided consistent diagnostic criteria. Recent studies refute the idea of muscle or central nervous system hyperactivity in TMD, while somatosensory system evaluations have yielded conflicting results. In this study, we aimed to investigate whether patients with unilateral chronic craniofacial pain exhibit hyposensitivity to phasic nociceptive stimuli in the trigeminal area and whether chronic pain modulates brainstem reflex circuits, specifically laser silent periods (LSP). Our results indicate that TMD patients show reduced sensitivity to phasic nociceptive stimuli, with a significant reduction in laser-evoked potential (LEP) amplitude, particularly on the painful side. Moreover, LSPs were absent in most patients, suggesting bilateral inhibition of brainstem nociceptive reflexes. These findings point to dysfunctions in the nociceptive pathways mediating and integrating phasic nociceptive inputs in TMD patients, though it remains unclear whether this dysfunction is a cause or consequence of chronic pain.
+'''Abstract:''' Temporomandibular dysfunction (TMD) comprises a group of painful conditions affecting the masticatory muscles and temporomandibular joint (TMJ). Despite extensive research, the pathophysiology and etiology of TMD remain unclear, with hypotheses largely unproven. Electromyographic (EMG) studies have identified alterations in the voluntary or reflex activity of the masticatory muscles in TMD patients, though these findings have not provided consistent diagnostic criteria. Recent studies refute the idea of muscle or central nervous system hyperactivity in TMD, while somatosensory system evaluations have yielded conflicting results. In this study, we aimed to investigate whether patients with unilateral chronic craniofacial pain exhibit hyposensitivity to phasic nociceptive stimuli in the trigeminal area and whether chronic pain modulates brainstem reflex circuits, specifically laser silent periods (LSP). Our results indicate that TMD patients show reduced sensitivity to phasic nociceptive stimuli, with a significant reduction in laser-evoked potential (LEP) amplitude, particularly on the painful side. Moreover, LSPs were absent in most patients, suggesting bilateral inhibition of brainstem nociceptive reflexes. These findings point to dysfunctions in the nociceptive pathways mediating and integrating phasic nociceptive inputs in TMD patients, though it remains unclear whether this dysfunction is a cause or consequence of chronic pain.
 ===Introduction===
 The term temporomandibular dysfunction (TMD) refers to a group of painful syndromes affecting the masticatory muscles and the temporomandibular joint (TMJ)<ref name="Dworkin1992">Dworkin SF, LeResche L. Research diagnostic criteria for temporomandibular disorders: review, criteria, examinations, and specifications. J Craniomandib Disord 1992; 6: 301-355.</ref>. Nosographic classifications of TMD vary widely as they may involve different pathophysiological mechanisms, and the etiological factors are often unknown<ref name="Green2000">Green S. Case presentation: resolution of an oral lesion as a result of orofacial myofunctional therapy. Int J Orofacial Myology 2000; 26: 53-56.</ref>. Many of the hypotheses proposed to explain its pathophysiology and etiology remain largely unproven<ref name="Fricton1995">Fricton JR, Dubner R. Orofacial Pain and Temporomandibular Disorders, Advances in Pain Research and Therapy, vol. 21, Raven Press, New York; 1995.</ref><ref name="Sessle1995">Sessle BJ, Bryant PS, Dionne RA. Temporomandibular Disorders and Related Pain Conditions, Progress in Pain Research and Management, vol. 4, IASP Press, Seattle, WA, 1995.</ref>. Electromyographic (EMG) alterations of the voluntary or reflex activity of the masticatory muscles have often been found in association with TMD; however, EMG studies have neither provided reliable criteria nor clarified the pathogenesis of this controversial syndrome<ref name="Svensson2001">Svensson P, Graven-Nielsen T. Craniofacial muscle pain: review of mechanisms and clinical manifestations. J Orofacial Pain 2001; 15: 117-145.</ref>.