Muscle-Related Temporomandibular Disorders

Rapid developments in laboratory-based research in the past decade have provided important new insight into the cellular and molecular mechanisms of nociception. However, the integration of the new understanding into clinical practice is hampered by our inability to combine discrete and often disparate bodies of knowledge and to translate new facts into a perspective of disease-specific significance and case-specific relevance. This process is also inhibited by the current classification systems, which focus heavily on the peripheral anatomy and provide little room to incorporate new understanding of the central nervous system (CNS) in the pathogenesis of disease. If central targets become the object of treatment, crude and often invalid measures of CNS, neuroendocrine, and autonomic processes are used as justification. With the widening gap between bench top-derived research data and clinical practice, an effort needs to be made to translate the basic science frontier into meaning for patients. The muscle-related conditions constitute the most enigmatic subset among the remporomandibular disorders (TMD). These conditions also represent the most prevalent presentations among the TMD, with at least 50% of cases falling into this category. Intense research in the past 10 years has resulted in (1) an improved epidemiologic and clinical description of the phenomenon; (2) new understanding of the molecular, neurophysiologic, and psychophysiologic mechanisms of nociception; and (3) the emergence of metabolic, neuroendocrinologic, and genetic findings. Rather than focusing on the dismissal of previous etiologic constructs, this paper attempts to define what the muscle-related TMD are rather than what they are not. Special consideration is given to the large spectrum of case presentations and the fact that the more severe and persistent forms occur in women more often than in men. With this perspective in mind, the intent of this project was to develop a conceptual framework of the pathogenesis and clinical phenomenology of the muscle-related TMD.

allodynia; sensitization; neuroplasticity; neuroendocrine system; autonomic system; gender differences