J Orofac Pain
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The purpose of this article is to review the pharmacological treatment of neuropathic trigeminal pain by means of a systematic review. A number of randomized controlled trials and important historical and uncontrolled studies in trigeminal neuralgia and postherpetic neuralgia were identified. ⋯ It does not respond to the usual drugs used for other neuropathic pains. The drug therapy of trigeminal postherpetic neuralgia is similar to that of other neuropathic trigeminal pain conditions.
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Neuropathic trigeminal pain conditions are more common than is generally appreciated. Sites inside the mouth as well as involvement of extraoral tissues are common manifestations of these disorders. There is a general lack of recognition of the complex characteristics of neuropathic trigeminal pain that frequently lead to mischaracterization of the nature of the complaint. ⋯ Relative to etiology, the records review revealed that most onsets were associated with a specific dental treatment or odontogenic symptom that resulted in a dental diagnosis or treatment. Initial treatment modalities that either caused the pain or were used to address painful symptoms commonly included replacement of restorations, endodontic therapy, apicectomy, extraction, splint therapy, and occlusal equilibration. Correct diagnosis, and particularly early definitive diagnosis, of neuropathic trigeminal pain is crucial to avoid invasive and potentially more damaging forms of treatment.
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Transmission of noxious-stimulus-evoked inputs in the spinal and trigeminal systems is mediated primarily through excitatory glutamatergic synapses using alpha amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA), kainate and N-methyl-D-aspartate (NMDA) subtypes of glutamate receptors. Glutamatergic synapses exhibit multiple forms of short-lasting and long-lasting synaptic plasticity. Persistent enhancement of nociceptive transmission, known as "central sensitization," is a form of lasting plasticity that is similar mechanistically to long-term potentiation of glutamatergic transmission in other regions of the central nervous system. ⋯ Central sensitization is thus an expression of increased synaptic gain at glutamatergic synapses in central nociceptive-transmission neurons and thereby contributes importantly to pain hypersensitivity. In addition, recent evidence has revealed a new player in the mechanisms underlying pain hypersensitivity following nerve injury--microglia. Understanding of the roles of microglia may lead to new strategies for the diagnosis and management of neuropathic pain.
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Nerve signals arising from sites of tissue or nerve injury lead to long-term changes in the central nervous system and contribute to hyperalgesia and the amplification and persistence of pain. These nociceptor activity-dependent changes are referred to as central sensitization. Central sensitization involves an increase in the excitability of medullary dorsal horn (subnucleus caudalis) and spinal dorsal horn neurons brought about by a series of events including neuronal depolarization; removal of the voltage-dependent magnesium block of the N-methyl-D-aspartate (NMDA) receptor; release of calcium from intracellular stores; phosphorylation of the NMDA, alpha amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA), and neurokinin (NK) 1 receptors via activation of protein kineses; a change in the neuron's excitability; and an increase in synaptic strength. ⋯ In contrast, the ventral pole of the Vi/Vc is unique. In addition to its role in the nociceptive sensory processing of deep tissues, it is involved bilaterally in somatovisceral and somatoautonomic processing, activation of the pituitary-adrenal axis, and descending modulatory control. The findings support our overall hypothesis that the ventral pole of Vi/Vc is involved in the coordination of bilateral sensorimotor functions of the trigeminal system associated with the response to deep tissue injury.
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Comparative Study
Comparison of algometry and palpation in the recognition of temporomandibular disorder pain complaints.
To determine the construct validity of algometry and to compare it with that of palpation, and to compare tenderness of masticatory muscle sites and the temporomandibular joint (TMJ) on palpation and on algometry. ⋯ Construct validity of algometry in the recognition of TMD pain complaints is comparable to that of palpation, and differences in tenderness on palpation and on algometry are found between masticatory muscle sites and the TMJ.