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Difference between revisions of "Bilateral Trigeminal neuromotor organic symmetry"
Bilateral Trigeminal neuromotor organic symmetry (view source)
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[[File:Potenziale Evocato della Radice Trigeminale.jpg | [[File:Potenziale Evocato della Radice Trigeminale.jpg|left]] | ||
In order to achieve a complete clinical evaluation of mastication, an in-depth neurophysiopathological assessment of masticatory muscles control is required. Electromyography technique (EMG) is widely used for this purpose, but failed to provide convincing results. | <translate>In order to achieve a complete clinical evaluation of mastication, an in-depth neurophysiopathological assessment of masticatory muscles control is required. Electromyography technique (EMG) is widely used for this purpose, but failed to provide convincing results</translate>. | ||
<translate>The aim of this work was to describe our quantitative objectivation of the motor control of the masticatory muscles and to verify the hypothesis to consider the bilateral Root Motor Evoked Potentials as an electrophysiological normalization factor</translate>. | |||
{{ArtBy| | {{ArtBy| | ||
| autore = Gianni Frisardi | | autore = Gianni Frisardi | ||
| autore2 = | | autore2 = Şükrü Okkesim | ||
| autore3 = | | autore3 = Alice Bisirri | ||
| autore4 = | | autore4 = Flavio Frisardi | ||
| autore5 = | | autore5 = Pier Paolo Valentini | ||
| autore6 = | | autore6 = | ||
}} | }} | ||
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===<sub>b</sub>R-MEPs stability and synchronicity=== | ===<sub>b</sub>R-MEPs stability and synchronicity=== | ||
[[File:TCS - Motor Evoked Potentials of trigeminal roots in open bite patient.jpg|thumb|'''Figure 2''': Motor evoked potentials elicited by transcranial electrical stimulation of both trigeminal roots]] | [[File:TCS - Motor Evoked Potentials of trigeminal roots in open bite patient.jpg|thumb|'''Figure 2''': Motor evoked potentials elicited by transcranial electrical stimulation of both trigeminal roots]] | ||
Another essential element to support the proposed normalization factor is its stability and synchronicity in the neuromuscular response. | Another essential element to support the proposed normalization factor is its stability and synchronicity in the neuromuscular response. | ||
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We have to add to these biases an even more limiting phenomenon than the intracranial current distribution with vectorial summation and collision current phenomena. However, the morphology of the <sub>b</sub>R-MEPs (Figure 2) and the difference in latency and amplitude (0.04 msec and 400 μV, respectively) reported in Table 2, confirm the high stability and synchronicity of the <sub>b</sub>R-MEPs. Keep in mind that, in order to extract the maximum efficiency from the normalization model proposed, any functional tests, such as trigeminal reflexes, must be performed in the same session and, therefore, with the same electrode arrangement. This way it will significantly reduce distortion due to the recording geometry. | We have to add to these biases an even more limiting phenomenon than the intracranial current distribution with vectorial summation and collision current phenomena. However, the morphology of the <sub>b</sub>R-MEPs (Figure 2) and the difference in latency and amplitude (0.04 msec and 400 μV, respectively) reported in Table 2, confirm the high stability and synchronicity of the <sub>b</sub>R-MEPs. Keep in mind that, in order to extract the maximum efficiency from the normalization model proposed, any functional tests, such as trigeminal reflexes, must be performed in the same session and, therefore, with the same electrode arrangement. This way it will significantly reduce distortion due to the recording geometry. | ||
====Organic symmetry==== | ====Organic symmetry==== | ||
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A reflex opening of the jaw, resulting from the simultaneous relaxation of jaw closers and contraction of jaw openers, not only helps to avoid injuries to the oral tissues, but also could contribute to coordinating rhythmic masticatory movements.<ref>Shigenaga Y, Yoshida A, Mitsuhiro Y, Tsuru K, Doe K (1988) Morphological and functional properties of trigeminal nucleus oralis neurons projecting to the trigeminal motor nucleus of the cat. Brain Res 461: 143-149.</ref>The stimulus applied to one side evokes the reflex bilaterally in a nearly symmetrical fashion. The symmetrical output is characteristic of most of the jaw movements induced by sensory signals both from the peripheral tissue and from those generated by signals coming from the cerebral cortex. | A reflex opening of the jaw, resulting from the simultaneous relaxation of jaw closers and contraction of jaw openers, not only helps to avoid injuries to the oral tissues, but also could contribute to coordinating rhythmic masticatory movements.<ref>Shigenaga Y, Yoshida A, Mitsuhiro Y, Tsuru K, Doe K (1988) Morphological and functional properties of trigeminal nucleus oralis neurons projecting to the trigeminal motor nucleus of the cat. Brain Res 461: 143-149.</ref>The stimulus applied to one side evokes the reflex bilaterally in a nearly symmetrical fashion. The symmetrical output is characteristic of most of the jaw movements induced by sensory signals both from the peripheral tissue and from those generated by signals coming from the cerebral cortex. | ||
Previous studies <ref>Nakamura Y, Nagashima H, Mori S (1973) Bilateral effects of the afferent impulses from the masseteric muscle on the trigeminal motoneuron of the cat. Brain Res 57: 15-27.</ref> | Previous studies have shown that peripheral stimulation evokes inhibitory postsynaptic potentials (IPSPs) in bilateral jaw-closer motor neurons.<ref>Nakamura Y, Nagashima H, Mori S (1973) Bilateral effects of the afferent impulses from the masseteric muscle on the trigeminal motoneuron of the cat. Brain Res 57: 15-27.</ref> This bilateral inhibition is mediated, at least in part, by supra- and juxta-trigeminal neurons with bifurcating axons projecting to both the right and the left masseter motor neurons. The goal of a recent study was to morphologically analyse how the functional symmetry of the masticatory system might be reflected in the organisation of pre-motor neurons and how it could be able to mediate excitation of jaw-opener motor-neurons.<ref>Yoshida A, Yamamoto M, Moritani M, Fukami H, Bae YC, et al. (2005) Bilateral projection of functionally characterized trigeminal oralis neurons to trigeminal motoneurons in cats. Brain Res 1036: 208-212.</ref> | ||
It has been demonstrated that in the masticatory system, where symmetrical motor output is the rule, employing neurons with bifurcating axons as a pre-motor element might be a common strategy for mediation of both peripheral and central signals. | It has been demonstrated that in the masticatory system, where symmetrical motor output is the rule, employing neurons with bifurcating axons as a pre-motor element might be a common strategy for mediation of both peripheral and central signals. | ||