Browsing by Subject "transcranial magnetic stimulation"

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  • Sathyan, Sabin; Tolmacheva, Aleksandra; Tugin, Sergei; Mäkelä, Jyrki P.; Shulga, Anastasia; Lioumis, Pantelis (2021)
    Paired associative stimulation (PAS) is a stimulation technique combining transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS) that can induce plastic changes in the human motor system. A PAS protocol consisting of a high-intensity single TMS pulse given at 100% of stimulator output (SO) and high-frequency 100-Hz PNS train, or "the high-PAS " was designed to promote corticomotoneuronal synapses. Such PAS, applied as a long-term intervention, has demonstrated therapeutic efficacy in spinal cord injury (SCI) patients. Adding a second TMS pulse, however, rendered this protocol inhibitory. The current study sought for more effective PAS parameters. Here, we added a third TMS pulse, i.e., a 20-Hz rTMS (three pulses at 96% SO) combined with high-frequency PNS (six pulses at 100 Hz). We examined the ability of the proposed stimulation paradigm to induce the potentiation of motor-evoked potentials (MEPs) in five human subjects and described the safety and tolerability of the new protocol in these subjects. In this study, rTMS alone was used as a control. In addition, we compared the efficacy of the new protocol in five subjects with two PAS protocols consisting of PNS trains of six pulses at 100 Hz combined with (a) single 100% SO TMS pulses (high-PAS) and (b) a 20-Hz rTMS at a lower intensity (three pulses at 120% RMT). The MEPs were measured immediately after, and 30 and 60 min after the stimulation. Although at 0 and 30 min there was no significant difference in the induced MEP potentiation between the new PAS protocol and the rTMS control, the MEP potentiation remained significantly higher at 60 min after the new PAS than after rTMS alone. At 60 min, the new protocol was also more effective than the two other PAS protocols. The new protocol caused strong involuntary twitches in three subjects and, therefore, its further characterization is needed before introducing it for clinical research. Additionally, its mechanism plausibly differs from PAS with high-frequency PNS that has been used in SCI patients.
  • Hernandez-Pavon, Julio C.; Makela, Niko; Lehtinen, Henri; Lioumis, Pantelis; Makela, Jyrki P. (2014)
  • Shulga, A.; Savolainen, S.; Kirveskari, E.; Mäkelä, J.P. (2020)
    Introduction: Paired associative stimulation (PAS) is a combination of transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS) and induces plastic changes in the human corticospinal tract. We have previously shown that PAS consisting of TMS pulses given at 100% of stimulator output and high-frequency PNS is beneficial for motor rehabilitation of patients with a chronic incomplete spinal cord injury (SCI). The therapeutic possibilities of this PAS variant for walking rehabilitation of paraplegic patients are unexplored. Case presentation: A 47-year old man with traumatic incomplete paraplegia (AIS D, neurological level T7) received PAS to his left leg for 3 months at 12 months post injury (PAS1) and for an additional 3 months at 24 months post injury (PAS2). The right leg had normal AIS scores and was not stimulated. Before PAS, the patient was nonambulatory, could not stand without weight support, and was consequently not eligible for conventional walking rehabilitation. After PAS1, the patient could stand for 1.5 min and take 13 steps (24 steps in follow up) on parallel bars without weight support and was enrolled into conventional walking rehabilitation. He achieved independent walking ability with a rollator. During PAS2, walking distance increased 2.4 times faster than during the preceding year. The left leg AIS score and spinal cord independence measure mobility subscore increased. No adverse effects were detected. Discussion: This is the first report of PAS with a high-frequency peripheral component that enabled and promoted walking rehabilitation. Together with previous reports on this technique, this result encourages further research into its therapeutic potential and mechanism. © 2020, The Author(s).
  • De Geeter, N.; Lioumis, P.; Laakso, A.; Crevecoeur, G.; Dupre, L. (2016)
    When delivered over a specific cortical site, TMS can temporarily disrupt the ongoing process in that area. This allows mapping of speech-related areas for preoperative evaluation purposes. We numerically explore the observed variability of TMS responses during a speech mapping experiment performed with a neuronavigation system. We selected four cases with very small perturbations in coil position and orientation. In one case (E) a naming error occurred, while in the other cases (NEA, B, C) the subject appointed the images as smoothly as without TMS. A realistic anisotropic head model was constructed of the subject from T1-weighted and diffusion-weighted MRI. The induced electric field distributions were computed, associated to the coil parameters retrieved from the neuronavigation system. Finally, the membrane potentials along relevant white matter fibre tracts, extracted from DTI-based tractography, were computed using a compartmental cable equation. While only minor differences could be noticed between the induced electric field distributions of the four cases, computing the corresponding membrane potentials revealed different subsets of tracts were activated. A single tract was activated for all coil positions. Another tract was only triggered for case E. NEA induced action potentials in 13 tracts, while NEB stimulated 11 tracts and NEC one. The calculated results are certainly sensitive to the coil specifications, demonstrating the observed variability in this study. However, even though a tract connecting Broca's with Wernicke's area is only triggered for the error case, further research is needed on other study cases and on refining the neural model with synapses and network connections. Case-and subject-specific modelling that includes both electromagnetic fields and neuronal activity enables demonstration of the variability in TMS experiments and can capture the interaction with complex neural networks.
  • Tolmacheva, Aleksandra; Savolainen, Sarianna; Kirveskari, Erika; Lioumis, Pantelis; Kuusela, Linda; Brandstack, Nina; Ylinen, Aarne; Mäkelä, Jyrki P.; Shulga, Anastasia (2017)
    A large proportion of spinal cord injuries (SCI) are incomplete. Even in clinically complete injuries, silent non-functional connections can be present. Therapeutic approaches that can strengthen transmission in weak neural connections to improve motor performance are needed. Our aim was to determine whether long-term delivery of paired associative stimulation (PAS, a combination of transcranial magnetic stimulation [TMS] with peripheral nerve stimulation [PNS]) can enhance motor output in the hands of patients with chronic traumatic tetraplegia, and to compare this technique with long-term PNS. Five patients (4 males; age 38-68, mean 48) with no contraindications to TMS received 4 weeks (16 sessions) of stimulation. PAS was given to one hand and PNS combined with sham TMS to the other hand. Patients were blinded to the treatment. Hands were selected randomly. The patients were evaluated by a physiotherapist blinded to the treatment. The follow-up period was 1 month. Patients were evaluated with Daniels and Worthingham's Muscle Testing (0-5 scale) before the first stimulation session, after the last stimulation session, and 1 month after the last stimulation session. One month after the last stimulation session, the improvement in the PAS-treated hand was 1.02 +/- 0.17 points (p <0.0001, n = 100 muscles from 5 patients). The improvement was significantly higher in PAS-treated than in PNS-treated hands (176 +/- 29%, p = 0.046, n = 5 patients). Longterm PAS might be an effective tool for improving motor performance in incomplete chronic SCI patients. Further studies on PAS in larger patient cohorts, with longer stimulation duration and at earlier stages after the injury, are warranted.