Difference between revisions of "Trigeminal Nervous System Segmentation"

[[File:Laser_Evoked_Potentials_-_Blink_reflex_-_Masseter_Silent_Period.jpg|left|thumb|'''<translate>Figure</translate> 9:'''  Laser stimulation that evoke a Blink reflex (BR), a Masseter Inhibitor Reflex (MIR) and Evoked Potentials Laser (LEPs)]]The perception threshold has been determined by the limits method in two sets of intensity by increasing or decreasing the trigger stimulation. The intensity of the laser beam is fixed at 1.5 the perceptual threshold. With regard to LEP (LEP: Laser Evoked Potentials), signals are recorded through the top-disk electrodes (Cz) with two references for each side on the ear lobes (A1, A2). Two blocks of eight to 12 tests each are mediated off-line. Signs are amplified, filtered (0.5–50 Hz), and stored by means of an analyser for biopotential (Premiere, Medelec, UK). For each block, we have measured the latency of the N and P components and the peak-to-peak width of the potential evoked.<ref>Romaniello, A., et al., ''[https://www.ncbi.nlm.nih.gov/pubmed/?term=Assessment+of+nociceptive+trigeminal+pathways+by+laser-evoked+potentials+and+laser+silent+periods+in+patients+with+painful+temporomandibular+disorders.+Pain%2C+2003 Assessment of nociceptive trigeminal pathways by laser-evoked potentials and laser silent periods in patients with painful temporomandibular disorders.]'' Pain, 2003. 103(1-2): p. 31-9. </ref> For LSPs, the same parameters were used as described above, but the recording is performed on masseter muscles. The area was subtracted from the 100-ms curve prior to adjusted and mediated laser stimulus (pre-analysis). The duration of the registered EMG activity is 400 ms, of which 100 ms corresponds to pre-stimulus and 300 ms in the post-stimulus period. The EMG signals are amplified, filtered (20 Hz–1 kHz), and sampled at 4 kHz. Subjects are asked to tighten their teeth with the maximum muscular strength to determine the EMG activity corresponding to the Maximum Volunteer Contraction (MVC: Maximum Voluntary Contraction) of masseter muscles and at different levels (15–25%), (35–45%), (55-65%), and (75–85%) of MVC. Subjects receive visual feedback with markers on the computer screen, which clearly indicates when the default level is reached. As one can see in Figure 19, the results of the following work are schematized in accordance with the type of test performed. With a laser stimulation in the skin region corresponding to the emergence of the supraorbital nerve (V1), we can have a Blink Reflex as a reflected response (BR) and notice the perfect symmetry of the responses on sides R1 and R2. Stimulation in the perioral region will result in a reflex response from the masseterini muscles called Laser Silent Period (LSP: Laser Silent Period). We might note that, in this test, a slight asymmetry of the track—mainly caused by the different degree of motoneural recruitment in the maximum intercuspidation. The registration on the scalp determines the potential laser summers of the trigeminal somatosensory area (LEPs) and measure the negative and positive spikes (N and P). Here, too, we witness a high level of symmetry.

The Exposed Laser procedure is very interesting because—as shown in Figure 19—there is evidence of a high symmetry of the blue component of the Blink reflex (R2 right and left) that corresponds to the motor nerve activity of the facial nerve; a relative somatosensory symmetry might be detected(N2 and P2, while a clear asymmetry of the MCV masseterin (MIR) is denoted in the width of the motor unit by both stimulus and post-inhibition. This introduces an important concept of the neural symmetry that might reveal an extraordinarily fascinating world of neurophysiopathological notions in the field of mastication.