- Email: [email protected]
PO12.4 Reciprocal Inhibition in Essential Tremor
2009 Asian and Oceanian Congress of Clinical Neurophysiology
PO12. Transcranial Magnetic Stimulation PO12.1 Hemispheric Asymmetry of Surround Inhibition in the Human Motor System Hae-Won Shin1,2 *, Young H. Sohn1 1 Dept. of Neurology and Brain Research Institute, Yonsei University College of Medicine, Korea, 2 Parkinson/Alzheimer Center, Dept. of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Korea E-mail address: [email protected] Background: Handedness is the most prominent human behavioral asymmetry and refers either to hand preference or to the asymmetrical performance of motor tasks. Surround inhibition (SI) in the motor system is an essential mechanism for the selective execution of desired movements. Because appropriate movement selection is essential for the successful performance of various motor tasks, functional operation of SI could be an important factor in deciding hand dominance. Methods: Ten healthy, right-handed volunteers participated in this study. Trasncranial magnetic stimulation (TMS) was set to be triggered by self-initiated flexion of the index finger at different intervals between EMG onset and TMS triggering. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of the control TMS at rest. Normalized MEP amplitudes of the adductor digiti minimi (ADM) and the flexor digitorum superficialis (FDS) muscles were compared between the dominant and non-dominant hands. Results: MEPs were suppressed or unchanged in the dominant ADM during index finger movement while MEPs were significantly enhanced in the dominant FDS. In the non-dominant ADM, MEPs were unchanged but not suppressed during index finger movement, while MEPs were significantly enhanced in the non-dominant FDS, similar to the dominant FDS. Compared to the resting state, ADM MEP amplitudes were significantly reduced at intervals of 3, 15, 40 ms during self-triggered TMS in the dominant hand, while those were unchanged at all intervals in the nondominant hand. MEP amplitudes of the dominant ADM were significantly more suppressed than those of the non-dominant ADM at intervals of 3, 15, and 40 ms. Conclusion: These results suggest that the functional operation of SI in the motor system is more efficient in the dominant hand than the nondominant hand. More efficient SI in the dominant hand could lead to greater dexterity in the dominant hand. PO12.2 Colchicine-Induced Fatigue: A Transcranial Magnetic Stimulation Study Kwong-Kum Liao1 *, Yung-Yang Lin1,2 1 Dept. of Neurology, Taipei Veterans General Hospital, Taiwan, 2 Dept. of Physiology, National Yang Ming University, Taiwan E-mail address: [email protected] Background: Fatigue without weakness was noted in eight patients with colchicine myopathy (CM). Using transcranial magnetic stimulation (TMS), we investigated if fatigue of our CM patients was in part associated with supraspinal mechanisms and if there was plastic changes in the brain due to myopathy. Methods: Eight CM patients and fifteen healthy controls participated in this study. Fatigue severity scale was used to assess the fatigue severity in each subject and the Borg scale was used to assess how hard a subject perceived exertion in fatiguing exercise test. In addition to the clinical assessments, TMS was performed before and after fatiguing exercise test. Results: CM patients had higher fatigue severity scale and higher Borg scale. However, TMS study did not show any significant group difference in motor cortical excitability both before and after fatiguing task. Conclusions: The present results demonstrate that motor cortex plasticity is not induced to compensate the muscle weakness in CM patients. Because the physiological changes during fatiguing exercise test were comparable between CM and control groups, supraspinal mechanisms underlying fatigue could also be similar between the two groups.
S81 PO12.3 Triple Stimulation Technique in Amyotrophic Lateral Sclerosis Patients Hyun Dong Park *, Hee-Kyung Park, Hee Jin Kim, Hyung Young Kim, Hee-Tae Kim, Juhan Kim, Seung Hyun Kim Dept. of Neurology, Hanyang University Hospital, Korea E-mail address: [email protected] Background: Amyotrophic lateral sclerosis (ALS) is progressive degenerative disease with loss of corticospinal and spinal motor neurons. Motor evoked potentials (MEPs) by conventional single-pulse transcranial magnetic stimulation (TMS) was used for estimation of loss of upper motor neuron (UMN). However, conventional MEP parameters are not related to the number of upper motor neuron loss. We used triple stimulation technique (TST) to estimate quantitative loss of upper motor neuron in ALS patients. Methods: Nine ALS patients and 12 healthy control subjects were enrolled in the study. According to the EL Escorial criteria, 1 patient was diagnosed as suspected, possible in 5 patients, and 3 patients were definite. All patients were examined by conventional MEP and TST. For quantification of upper motor neuron loss, mean central motor conduction time (CMCT), mean MEP amplitude/compound muscle action potential (CMAP) Erb ratio, mean TST amplitude ratio and mean area ratio were compared. Results: In healthy control subjects, mean CMCT was 4.12(±0.88) ms, mean MEP amplitude/CMAP Erb ratio was 0.66(±0.11), mean TST amplitude ratio was 0.87(±0.12), and mean area ratio 0.89(±0.14). In ALS patients, mean CMCT was 5.07(±1.02) ms, mean MEP amplitude/CMAP Erb ratio was 0.46(±0.23), mean TST amplitude ratio was 0.57(±0.19), and mean area ratio 0.54(±0.16). In these parameters, TST amplitude ratio showed positive correlations with weakness as 89% sensitivity in ALS patients. Conclusions: TST provides a quantitative tool for assessing UMN loss. TST might be more sensitive and useful in the diagnosis of UMN involvement than conventional MEP in ALS patients. PO12.4 Reciprocal Inhibition in Essential Tremor Ha-Neul Lee *, Hyun Young Kim, Seong-Ho Koh, Kyu-Young Lee, Young Joo Lee, Seung Hyun Kim, Juhan Kim, Hee-Tae Kim Dept. of Neurology, College of Medicine, Hanyang University, Korea E-mail address: [email protected] Background: Many neurological disorders present with tremor, including essential tremor (ET), dystonic tremor (DT), Parkinson’s disease, etc. But, these disorders have been misdiagnosed as ET due not only to variable clinical presentation but also to a lack of agreement among movement disorder specialists. Excessive and inappropriate cocontraction of antagonist muscles is characteristic of both voluntary and involuntary movements in patients with dystonia. But, patients with ET do not have this characteristic. Reciprocal inhibition (RI) is that the antagonist muscles are actively inhibited by central mechanism while on contraction of agonist muscles. So, we build hypothesis that RI may be generated normally in patients with ET, but patients with dystonic tremor (DT) may not be. Methods: The subjects of the study were 15 controls, 15 patients with classic ET, 15 patients with DT and 5 patients with ET variant. The RI between the wrist flexors and extensors was obtained. The FCR H-reflex was tested by electrical stimulation of the median nerve in antecubital fossa. A stimulation of the radial nerve in spiral groove, at the time of 1 ms before stimulation of median nerve, was used to evoke disynpatic inhibition of FCR motor neurons. We compared the ratio of conditioned RI and unconditioned RI in patients with ET, ET variant, and DT. Results: Significant difference of RI was observed between classic ET and DT group (P < 0.001). In DT group, less pronounced inhibition was found at first period of RI. In ET group, the inhibition was significant compared with DT group. It was similar with control group. There is much inter-subject variation in patients with ET variant (or isolated head tremor). Conclusions: Our data support the previous findings that less inhibition was observed in patients with DT. Also, we found that there is a relatively pronounced inhibition in patients with classic ET. We suggested RI may be helpful in distinguishing isolated head tremor and DT.
PO12. Transcranial Magnetic Stimulation PO12.1 Hemispheric Asymmetry of Surround Inhibition in the Human Motor System Hae-Won Shin1,2 *, Young H. Sohn1 1 Dept. of Neurology and Brain Research Institute, Yonsei University College of Medicine, Korea, 2 Parkinson/Alzheimer Center, Dept. of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Korea E-mail address: [email protected] Background: Handedness is the most prominent human behavioral asymmetry and refers either to hand preference or to the asymmetrical performance of motor tasks. Surround inhibition (SI) in the motor system is an essential mechanism for the selective execution of desired movements. Because appropriate movement selection is essential for the successful performance of various motor tasks, functional operation of SI could be an important factor in deciding hand dominance. Methods: Ten healthy, right-handed volunteers participated in this study. Trasncranial magnetic stimulation (TMS) was set to be triggered by self-initiated flexion of the index finger at different intervals between EMG onset and TMS triggering. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of the control TMS at rest. Normalized MEP amplitudes of the adductor digiti minimi (ADM) and the flexor digitorum superficialis (FDS) muscles were compared between the dominant and non-dominant hands. Results: MEPs were suppressed or unchanged in the dominant ADM during index finger movement while MEPs were significantly enhanced in the dominant FDS. In the non-dominant ADM, MEPs were unchanged but not suppressed during index finger movement, while MEPs were significantly enhanced in the non-dominant FDS, similar to the dominant FDS. Compared to the resting state, ADM MEP amplitudes were significantly reduced at intervals of 3, 15, 40 ms during self-triggered TMS in the dominant hand, while those were unchanged at all intervals in the nondominant hand. MEP amplitudes of the dominant ADM were significantly more suppressed than those of the non-dominant ADM at intervals of 3, 15, and 40 ms. Conclusion: These results suggest that the functional operation of SI in the motor system is more efficient in the dominant hand than the nondominant hand. More efficient SI in the dominant hand could lead to greater dexterity in the dominant hand. PO12.2 Colchicine-Induced Fatigue: A Transcranial Magnetic Stimulation Study Kwong-Kum Liao1 *, Yung-Yang Lin1,2 1 Dept. of Neurology, Taipei Veterans General Hospital, Taiwan, 2 Dept. of Physiology, National Yang Ming University, Taiwan E-mail address: [email protected] Background: Fatigue without weakness was noted in eight patients with colchicine myopathy (CM). Using transcranial magnetic stimulation (TMS), we investigated if fatigue of our CM patients was in part associated with supraspinal mechanisms and if there was plastic changes in the brain due to myopathy. Methods: Eight CM patients and fifteen healthy controls participated in this study. Fatigue severity scale was used to assess the fatigue severity in each subject and the Borg scale was used to assess how hard a subject perceived exertion in fatiguing exercise test. In addition to the clinical assessments, TMS was performed before and after fatiguing exercise test. Results: CM patients had higher fatigue severity scale and higher Borg scale. However, TMS study did not show any significant group difference in motor cortical excitability both before and after fatiguing task. Conclusions: The present results demonstrate that motor cortex plasticity is not induced to compensate the muscle weakness in CM patients. Because the physiological changes during fatiguing exercise test were comparable between CM and control groups, supraspinal mechanisms underlying fatigue could also be similar between the two groups.
S81 PO12.3 Triple Stimulation Technique in Amyotrophic Lateral Sclerosis Patients Hyun Dong Park *, Hee-Kyung Park, Hee Jin Kim, Hyung Young Kim, Hee-Tae Kim, Juhan Kim, Seung Hyun Kim Dept. of Neurology, Hanyang University Hospital, Korea E-mail address: [email protected] Background: Amyotrophic lateral sclerosis (ALS) is progressive degenerative disease with loss of corticospinal and spinal motor neurons. Motor evoked potentials (MEPs) by conventional single-pulse transcranial magnetic stimulation (TMS) was used for estimation of loss of upper motor neuron (UMN). However, conventional MEP parameters are not related to the number of upper motor neuron loss. We used triple stimulation technique (TST) to estimate quantitative loss of upper motor neuron in ALS patients. Methods: Nine ALS patients and 12 healthy control subjects were enrolled in the study. According to the EL Escorial criteria, 1 patient was diagnosed as suspected, possible in 5 patients, and 3 patients were definite. All patients were examined by conventional MEP and TST. For quantification of upper motor neuron loss, mean central motor conduction time (CMCT), mean MEP amplitude/compound muscle action potential (CMAP) Erb ratio, mean TST amplitude ratio and mean area ratio were compared. Results: In healthy control subjects, mean CMCT was 4.12(±0.88) ms, mean MEP amplitude/CMAP Erb ratio was 0.66(±0.11), mean TST amplitude ratio was 0.87(±0.12), and mean area ratio 0.89(±0.14). In ALS patients, mean CMCT was 5.07(±1.02) ms, mean MEP amplitude/CMAP Erb ratio was 0.46(±0.23), mean TST amplitude ratio was 0.57(±0.19), and mean area ratio 0.54(±0.16). In these parameters, TST amplitude ratio showed positive correlations with weakness as 89% sensitivity in ALS patients. Conclusions: TST provides a quantitative tool for assessing UMN loss. TST might be more sensitive and useful in the diagnosis of UMN involvement than conventional MEP in ALS patients. PO12.4 Reciprocal Inhibition in Essential Tremor Ha-Neul Lee *, Hyun Young Kim, Seong-Ho Koh, Kyu-Young Lee, Young Joo Lee, Seung Hyun Kim, Juhan Kim, Hee-Tae Kim Dept. of Neurology, College of Medicine, Hanyang University, Korea E-mail address: [email protected] Background: Many neurological disorders present with tremor, including essential tremor (ET), dystonic tremor (DT), Parkinson’s disease, etc. But, these disorders have been misdiagnosed as ET due not only to variable clinical presentation but also to a lack of agreement among movement disorder specialists. Excessive and inappropriate cocontraction of antagonist muscles is characteristic of both voluntary and involuntary movements in patients with dystonia. But, patients with ET do not have this characteristic. Reciprocal inhibition (RI) is that the antagonist muscles are actively inhibited by central mechanism while on contraction of agonist muscles. So, we build hypothesis that RI may be generated normally in patients with ET, but patients with dystonic tremor (DT) may not be. Methods: The subjects of the study were 15 controls, 15 patients with classic ET, 15 patients with DT and 5 patients with ET variant. The RI between the wrist flexors and extensors was obtained. The FCR H-reflex was tested by electrical stimulation of the median nerve in antecubital fossa. A stimulation of the radial nerve in spiral groove, at the time of 1 ms before stimulation of median nerve, was used to evoke disynpatic inhibition of FCR motor neurons. We compared the ratio of conditioned RI and unconditioned RI in patients with ET, ET variant, and DT. Results: Significant difference of RI was observed between classic ET and DT group (P < 0.001). In DT group, less pronounced inhibition was found at first period of RI. In ET group, the inhibition was significant compared with DT group. It was similar with control group. There is much inter-subject variation in patients with ET variant (or isolated head tremor). Conclusions: Our data support the previous findings that less inhibition was observed in patients with DT. Also, we found that there is a relatively pronounced inhibition in patients with classic ET. We suggested RI may be helpful in distinguishing isolated head tremor and DT.