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Can we reduce the asymmetry of between-hemisphere motor excitability in the lower limb after stroke?
284
Abstracts
high temporal resolution, and can also discriminate necessary from coactivated brain areas. Desmurget et al (1999) showed that online correction for reaching to an altered target can be disturbed using TMS over the lPPC. In this study, we developed an fMRI localizer to assess lPPC sub-regions that are involved in online motor control. Subsequently, we tested these sites with event-related TMS. Using closed-loop reaching (with visual hand feedback) allows investigating the processes involved in body’s effectors representation in addition to environment representation during goal-directed reaching, by introducing different visual perturbations. The fMRI localizer consists of blocks for fixation, saccades, and reaching with an MR-compatible joystick. Within the reaching blocks, different visual perturbations (including none) were randomized in a fast eventrelated design. The different perturbation conditions were contrasted against the unperturbed reaching to assess online-correction activation. Nine right-handed subjects were tested. On group level, different visual perturbations resulted in spatial different activation patterns in the lPPC. In addition, we observed pronounced inter-individual differences in activation. Maxima from the group analyses and the individuals own maxima were used as stimulation sites for the subsequent TMS study. Four of the subjects were tested so far using event-related TMS on target alteration. Despite huge inter-individual differences in BOLD activation, we could demonstrate a closer match of TMS effect localization with subject’s individual activation than with group activation (fig. 1). This finding shows that TMS is capable of investigating sub-regions of the lPPC. Furthermore, it stresses the importance of individual analyses when investigating functions located there. The next step is to map the other visual perturbations.
Stimulation (iRTMS) and inhibitory Paired Associative Stimulation (iPAS) applied to the contralesional motor system, and facilitatory anodal Transcranial Direct Current Stimulation (aTDCS) applied to the ipsilesional motor system. These protocols have been used to manipulate motor cortical excitability and enhance upper limb motor recovery after stroke but research conducted to explore their effect on the lower limb is limited. The present study followed our recent experiment where we used iPAS to redress the asymmetry of between-hemisphere motor excitability in chronic stroke patients during walking. Inhibitory cathodal TDCS was not included in the present study because a study demonstrated cathodal TDCS does not induce an inhibitory effect on lower limb motor cortex. Results: All three protocols induced robust facilitation in the paretic Tibialis Anterior, Medial Gastrocnemius, Medial Hamstring and Vastus Lateralis. Peak modulation of motor evoked potentials (MEPs) averaged for all paretic muscles was: 133% of pre-stimulation values for iPAS; 129% for iRTMS and 126% for aTDCS. ANOVA did not reveal a main effect of stimulation type. A main effect of hemisphere was revealed for all three stimulation types indicating likely transcallosal disinhibition of the lesioned hemisphere with iPAS and iRTMS, and an up-regulation of the lesioned hemisphere with facilitatory aTDCS. Conclusion: These results suggest that these protocols are promising candidate priming mechanisms for subsequent application in walking training studies.
Clinical Studies Poster Only 144
Maintenance rTMS can decrease tinnitus chronically
Mennemeier M1, Chelette K1, Myhill J1, Bartel T1, Triggs W2, Kimbrell T1, Winham W1, Dornhoffer J1, 1University of Arkansas for Med Scs (Little Rock, AR, US); 2University of Florida (Gainesville, FL, US)
TMS Poster Only 143
Can we reduce the asymmetry of between-hemisphere motor excitability in the lower limb after stroke?
Jayaram G, Stinear J, Northwestern University (Chicago, US) Objective: Recent advances in our understanding of neuroplastic mechanisms following stroke are driving the search for a protocol that utilizes metaplasticity to enhance walking recovery. In healthy individuals balanced between-hemisphere motor excitability is maintained via transcallosal inhibitory connections, whereby each hemisphere acts to inhibit the other. Balanced transcallosal inhibition sustains the symmetry of between-hemisphere corticomotor excitability and assists the performance of bimanual voluntary movements. This notion raised the hypothesis that reducing the asymmetry in transcallosal inhibition following stroke would prime the motor system prior to training and lead to improvements in walking recovery. Methods: To test the first part of this hypothesis, we examined three neuromodulatory protocols during walking in 10 chronic subcortical stroke patients They were: inhibitory Repetitive Transcranial Magnetic
Objective: Tinnitus, phantom sound perception like ringing, affects 50 million people in the U.S alone. No widely efficacious treatment for tinnitus exists. Tinnitus is linked to maladaptive reorganization of auditory cortex following peripheral injury or disease; indicated both by excessive spread of cortical activity in response to external sound and by asymmetric increases in resting metabolic activity in the temporal lobe. A week long course of low frequency rTMS applied over auditory cortex can reduce tinnitus in .50% of patients but relapse typically occurs in 5 to 10 days. No previous study of tinnitus examined change in cortical metabolism following rTMS. We obtained resting FDG PET scans before and after rTMS to determine if change in cortical metabolism relates to improvement. We also provided maintenance rTMS as symptoms returned to promote long term change. Method: Ten patients with subjective tinnitus were assessed using questionnaires, rating scales, and resting FDG PET/CT scans both before and after rTMS. TMS was targeted over regions of interest (ROIs) in the temporal lobe showing increased, asymmetric activity on PET using the Brainsight system. Using a crossover design, patients received one week of active (1800 pulses at 1Hz and 110% of MT x 5 days) and sham rTMS (electrical scalp stimulation paired with a sham coil). Treatment responders also received 1-3 maintenance rTMS sessions as needed when symptoms returned. Result: Tinnitus decreased after active but not sham treatment in 5 patients (50%). PET activity decreased in the ROIs targeted for active treatment but change in PET did not correlate well with change in tinnitus perception. Tinnitus returned within 5-10 days in those who initially responded to treatment. One to three maintenance rTMS session could reliably reduce tinnitus in all 5 patients. Two patients no longer required any maintenance rTMS. Two had complete resolution in the ear contralateral to rTMS but mild recurrence in the ipsilateral ear. One had decreased but recurrent tinnitus in both ears. Conclusion: The inhibitory effect of 1 Hz rTMS was validated by repeat PET scans; however, the disconnect between change in PET and change in
Abstracts
high temporal resolution, and can also discriminate necessary from coactivated brain areas. Desmurget et al (1999) showed that online correction for reaching to an altered target can be disturbed using TMS over the lPPC. In this study, we developed an fMRI localizer to assess lPPC sub-regions that are involved in online motor control. Subsequently, we tested these sites with event-related TMS. Using closed-loop reaching (with visual hand feedback) allows investigating the processes involved in body’s effectors representation in addition to environment representation during goal-directed reaching, by introducing different visual perturbations. The fMRI localizer consists of blocks for fixation, saccades, and reaching with an MR-compatible joystick. Within the reaching blocks, different visual perturbations (including none) were randomized in a fast eventrelated design. The different perturbation conditions were contrasted against the unperturbed reaching to assess online-correction activation. Nine right-handed subjects were tested. On group level, different visual perturbations resulted in spatial different activation patterns in the lPPC. In addition, we observed pronounced inter-individual differences in activation. Maxima from the group analyses and the individuals own maxima were used as stimulation sites for the subsequent TMS study. Four of the subjects were tested so far using event-related TMS on target alteration. Despite huge inter-individual differences in BOLD activation, we could demonstrate a closer match of TMS effect localization with subject’s individual activation than with group activation (fig. 1). This finding shows that TMS is capable of investigating sub-regions of the lPPC. Furthermore, it stresses the importance of individual analyses when investigating functions located there. The next step is to map the other visual perturbations.
Stimulation (iRTMS) and inhibitory Paired Associative Stimulation (iPAS) applied to the contralesional motor system, and facilitatory anodal Transcranial Direct Current Stimulation (aTDCS) applied to the ipsilesional motor system. These protocols have been used to manipulate motor cortical excitability and enhance upper limb motor recovery after stroke but research conducted to explore their effect on the lower limb is limited. The present study followed our recent experiment where we used iPAS to redress the asymmetry of between-hemisphere motor excitability in chronic stroke patients during walking. Inhibitory cathodal TDCS was not included in the present study because a study demonstrated cathodal TDCS does not induce an inhibitory effect on lower limb motor cortex. Results: All three protocols induced robust facilitation in the paretic Tibialis Anterior, Medial Gastrocnemius, Medial Hamstring and Vastus Lateralis. Peak modulation of motor evoked potentials (MEPs) averaged for all paretic muscles was: 133% of pre-stimulation values for iPAS; 129% for iRTMS and 126% for aTDCS. ANOVA did not reveal a main effect of stimulation type. A main effect of hemisphere was revealed for all three stimulation types indicating likely transcallosal disinhibition of the lesioned hemisphere with iPAS and iRTMS, and an up-regulation of the lesioned hemisphere with facilitatory aTDCS. Conclusion: These results suggest that these protocols are promising candidate priming mechanisms for subsequent application in walking training studies.
Clinical Studies Poster Only 144
Maintenance rTMS can decrease tinnitus chronically
Mennemeier M1, Chelette K1, Myhill J1, Bartel T1, Triggs W2, Kimbrell T1, Winham W1, Dornhoffer J1, 1University of Arkansas for Med Scs (Little Rock, AR, US); 2University of Florida (Gainesville, FL, US)
TMS Poster Only 143
Can we reduce the asymmetry of between-hemisphere motor excitability in the lower limb after stroke?
Jayaram G, Stinear J, Northwestern University (Chicago, US) Objective: Recent advances in our understanding of neuroplastic mechanisms following stroke are driving the search for a protocol that utilizes metaplasticity to enhance walking recovery. In healthy individuals balanced between-hemisphere motor excitability is maintained via transcallosal inhibitory connections, whereby each hemisphere acts to inhibit the other. Balanced transcallosal inhibition sustains the symmetry of between-hemisphere corticomotor excitability and assists the performance of bimanual voluntary movements. This notion raised the hypothesis that reducing the asymmetry in transcallosal inhibition following stroke would prime the motor system prior to training and lead to improvements in walking recovery. Methods: To test the first part of this hypothesis, we examined three neuromodulatory protocols during walking in 10 chronic subcortical stroke patients They were: inhibitory Repetitive Transcranial Magnetic
Objective: Tinnitus, phantom sound perception like ringing, affects 50 million people in the U.S alone. No widely efficacious treatment for tinnitus exists. Tinnitus is linked to maladaptive reorganization of auditory cortex following peripheral injury or disease; indicated both by excessive spread of cortical activity in response to external sound and by asymmetric increases in resting metabolic activity in the temporal lobe. A week long course of low frequency rTMS applied over auditory cortex can reduce tinnitus in .50% of patients but relapse typically occurs in 5 to 10 days. No previous study of tinnitus examined change in cortical metabolism following rTMS. We obtained resting FDG PET scans before and after rTMS to determine if change in cortical metabolism relates to improvement. We also provided maintenance rTMS as symptoms returned to promote long term change. Method: Ten patients with subjective tinnitus were assessed using questionnaires, rating scales, and resting FDG PET/CT scans both before and after rTMS. TMS was targeted over regions of interest (ROIs) in the temporal lobe showing increased, asymmetric activity on PET using the Brainsight system. Using a crossover design, patients received one week of active (1800 pulses at 1Hz and 110% of MT x 5 days) and sham rTMS (electrical scalp stimulation paired with a sham coil). Treatment responders also received 1-3 maintenance rTMS sessions as needed when symptoms returned. Result: Tinnitus decreased after active but not sham treatment in 5 patients (50%). PET activity decreased in the ROIs targeted for active treatment but change in PET did not correlate well with change in tinnitus perception. Tinnitus returned within 5-10 days in those who initially responded to treatment. One to three maintenance rTMS session could reliably reduce tinnitus in all 5 patients. Two patients no longer required any maintenance rTMS. Two had complete resolution in the ear contralateral to rTMS but mild recurrence in the ipsilateral ear. One had decreased but recurrent tinnitus in both ears. Conclusion: The inhibitory effect of 1 Hz rTMS was validated by repeat PET scans; however, the disconnect between change in PET and change in