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P846: The effect of hand dominance on peripheral nerve excitability
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
Poster session 48. Excitability of nerve and muscle P843 Influence of anesthetic agents on sensory nerve excitability testing in mice Y. Osaki, H. Nodera, Y. Shimatani, B. Chimeglkham, R. Kaji Tokushima university, neurology, Tokushima, Japan Introduction: Nerve excitability study in experimental animals can directly test a hypothesis at a molecular level by a specific pharmacological agent or a genetic model. Unlike human subjects, animal study is often performed under anesthesia, however, the anesthetic effects on peripheral nerve excitability has not been fully investigated. Methods: We performed nerve excitability testing under two commonly used anesthetic agents in normal male mice: (1) 1.5% isoflurane inhalation (N=10) and (2) the triple agents – medetomidine (0.3 mg/kg), midazoram (4 mg/kg) and btorphanol (5 mg/kg) – intraperitoneal injection (N=10). Sensory nerve at the tail was orthodromically recorded, immediately after the animal was under control for maximal duration of 2 hours to assess the time course of the excitability changes. QtracS software (Digitimer, UK) was used. Result: Threshold changes by long hyperpolarizing stimulation (i.e., threshold electrotonus and current-threshold relationship) increased approximately 30 minutes after induction of anesthesia that sustained thereafter. By contrast, recovery cycle, strength-duration time constant and depolarizing threshold electrotonus showed no remarkable change during the recording. Conclusion: The results suggest anesthetic blockade of HCN channels which are activated by long hyperpolarizing current. When we assess the nerve excitability in experimental animals, the influence of anesthesia on nerve excitability should be taken into account.
P844 H-reflex recovery cycle as an electrophysiological correlate of spasticity A. Karakus 1 , B. Cengiz 1 , M. Zinnuroglu 2 1 Gazi University, Neurology, Ankara, Turkey; 2 Gazi University, Physical Medicine and Rehabilitation, Ankara, Turkey Objective: To investigate correlation between spasticity and spinal cord excitability, the recovery cycle of the H reflex (HRRC) was assessed using novel threshold tracking method. Method: A subset of patients with spastic paraparesis (11) were recruited for the study. Before HRRC, muscle strength and spasticity (with modified Ashworth Scale) of lower limbs were evaluated. HRRC was performed with two equal suprathreshold stimulus paradigm with different (between 2-200 ms) interstimulus intervals (ISIs) by using the threshold tracking method. Results: Preliminary results indicate that there is good correlation between inhibition of HRRC at ISIs of 56-2 ms and modified Ashworth scale scores (r>0.740). Conclusions: Findings of the study suggest that HRRC using the novel threshold tracking method is a good electrophysiological correlate of spasticity.
S267
Methods: We performed excitability studies of the median nerve at the wrist in 5 MMN and 7 CIDP patients with nerve conduction abnormalities in the forearm segment and 10 normal controls. Tests were performed following warming to 37°C and cooling to 25°C. Results in MMN and CIDP were compared with those in normal controls. Inverse modeling was used to interpret the results. Results: Following warming, MMN patients showed fanning-out and increased accommodation of threshold electrotonus, shortened refractory period and increased superexcitability. In CIDP, stimulus-response slope was decreased, rheobase was increased, threshold electrotonus showed fanning-out and refractory period was shortened. Inverse modeling showed decreased fast K-conductance, increased myelin conductance and hyperpolarization-activated cation conductance in MMN and increased myelin conductance and hyperpolarization-activated cation conductance in CIDP. Following cooling, changes in excitability-indices were largely similar in all groups. Conclusions: The present findings support permanent axonal hyperpolarization and demyelination in MMN, demyelination in CIDP, and normal effects of cooling on ion-channels in both diseases.
P846 The effect of hand dominance on peripheral nerve excitability Y. Tsuji 1 , Y.-I. Noto 1 , K. Shiga 2 , M. Nakagawa 3 , T. Mizuno 1 1 Graduate School of Medical Science, Kyoto Prefectural University of Medicine, neurology, Kyoto, Japan; 2 Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Medical Education and Primary Care, Kyoto, Japan; 3 North Medical Center, Kyoto Prefectural University of Medicine, Kyoto, Japan Question: The threshold tracking technique has been used for exploring the peripheral nerve excitability in normal subjects and patients with various neuromuscular diseases. Murray et al. reported that nerve excitability of the median and ulnar nerve was significantly different in normal subjects by using threshold tracking. However, it is unclear whether hand dominance can affect the peripheral nerve excitability. The aim of this study is to elucidate whether the properties in nerve excitability of the dominant hands are different from those of the non-dominant hands. Methods: Both median nerves were examined in healthy subjects using Trond NF program with Qtrac® system. Nerve excitability parameters were compared between dominant hands and non-dominant hands. In each individual, the dominant hand was determined by Edinburgh Handedness Inventory.
P845 Interpretation of excitability studies in multifocal motor neuropathy and chronic inflammatory demyelinating polyneuropathy D. Straver 1 , L. van Schelven 2 , L. van den Berg 1 , H. Franssen 1 1 UMC Utrecht, Brain Center Rudolf Magnus, Utrecht, Netherlands; 2 UMC Utrecht, Medical Technology and Clinical Physics, Utrecht, Netherlands Question: Pathophysiology of multifocal motor neuropathy (MMN) and chronic inflammatory demyelinating polyneuropathy (CIDP) is not fully understood. Nerve excitability studies have been performed to improve understanding of disease mechanisms, but results were difficult to interpret. Although cold paresis is frequently reported in MMN and was attributed to depolarized nerve lesions, effects of cooling on excitability were not previously studied in MMN and CIDP. The aim of this study was to explore nerve excitability in MMN and CIDP to assess changes in passive and active axonal membrane properties.
Figure 1. Comparison of the threshold tracking in dominant hand and non-dominant hand.
S268
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
Results: All subjects (n=10, 8 men and 2 women; aged 24-45 years) were right-handed. Strength-duration time constant (SDTC) demonstrated no difference between dominant hands [0.37±0.084 ms] and non-dominant hands [0.37±0.074 ms] (p=0.872). Second, all parameters in threshold electrotonus tracking showed no difference in hand dominance (TEh [90–100ms]; −117.3±13.6% [dominant hands], −116.4±7.8% [non-dominant hands], p=0.846, TEd [90–100ms]; 44.6±4.6% [dominant hands], 45.0±3.0% [non-dominant hands], p=0.794). In recovery cycle testing, no side difference was noted both in superexcitability and in subexcitability. Conclusions: Nerve excitability measures in dominant hands were not different from those in non-dominant hands. This study provides the practical basis for the hypothesis that it may be unnecessary to consider the handedness when exploring nerve excitability in patients with neuromuscular diseases.
the excitability of the facial nerve, the facial F waves were elicited by the paired stimulation (interstimulus interval (ISI): 40ms (during voluntary contraction of the silent period) or 80ms (during late phase of the silent period)). 2) To examine the silent period of the hemifacial spasm, the baseline activity was obtained in the mentalis muscle following the zygomatic branch stimulation. Results: 1) The F waves elicited by the second stimulation were enhanced (ISI: 40ms) and inhibited (ISI: 80ms). 2) The silent period was recorded in the mentalis muscles by the zygomatic branch stimulation in the patients with hemifacial spasm. Conclusions: The silent period expresses the facial nerve excitability as well as the facial nerve F waves elicited by paired stimulation. The silent period was recorded by not innervating nerve stimulation in the hemifacial spasm as well as the abnormal muscle responses.
P847 Signs of motoneuronal hyperexcitability with reinnervation after peripheral nerve lesions
P849 The relationship between muscle strength and transcranial stimulation motor evoked potential
M. Neves Cardoso 1 , C. Krarup 2 , J. Valls-Solé 3 1 Centro Hospitalar do Porto, Neurophysiology, Oporto, Portugal; 2 Copenhagen University Hospital, Clinical Neurophysiology, Copenhagen, Denmark; 3 Hospital Clinic, University of Barcelona, EMG Unit, Neurology, Barcelona, Spain
D. Mishima, T. Suwa, K. Mii National Hospital Organization Sagamihara National Hospital, Neurosurgery, Sagamihara, Japan
Question: Several abnormalities complicate reinnervation after complete section of a peripheral nerve. Axonal growth may lead to abnormal branching and reinnervation errors. Enhancement of excitability at motoneuronal level may entail generation of abnormal reflex responses. We examined the neurophysiological characteristics of these two types of abnormalities in 20 patients with complete traumatic section of either ulnar or median nerves. Methods: Patients were examined at predetermined periods between 3 and 24 months after the lesion. We recorded the motor and sensory nerve action potentials and performed needle electromyography in the affected muscles. For comparison, we also analyzed the motor and sensory nerve conduction of the same nerves in the contralatreral (unimpaired) extremity. For the analysis of abnormal sensorimotor responses, we recorded with needle EMG the muscle action potentials elicited by cutaneous stimulation to territories supplied by the impaired nerve and by unimpaired neighbour nerves. Results: We recorded two types of responses: The first response, of relatively short latency (12 to 45 ms), consistently appeared at the same latency with repeated stimuli. The second response, of longer latency (48 to 114 ms), appeared less constantly and had a noticeable latency variation with repeated stimuli. Only the second response was elicited with stimuli applied to unimpaired nerves. In both cases, response latency progressively shortened with successive exams. Conclusions: At least two types of abnormal muscle action potentials can be elicited by sensory stimuli during reinnervation after a mixed nerve lesion: Axo-axonic or ephaptic responses at relatively short latency and transynaptic reflex responses at longer latency.
Question: Transcranial electrical stimulation Motor evoked potential (TCSMEP) has been used as an intraoperative monitoring of motor functions. But TCS-MEP has inherent variability. This variability has disturbed that we push forward an analysis of TCS-MEP. How can we resolve this variability problem? We tried to show the absolute relationship between muscle strength and TCS-MEP by the unique method. Methods: We hypothesized that the fluctuation of MEP amplitudes took the distribution of the amount according to Gaussian distribution in the same condition. And the mean values of MEP amplitudes were measured within the constant period. The effects on motor tracts were digitized by using the ratio of the mean values that were measured before and after the invasive maneuvers. And we investigated the correlations between those ratios and the changes of muscle strength. TCS-MEP were monitored at 26 operations of 18 intramedurally spinal cord tumor cases. TCS-MEP was in the habit of recording every 10 minutes at the direct manipulation to spinal cord after the dura matter incision. 150 muscles’ data were analyzed. All muscles’ innervation was under the tumor level in spinal cord. We gathered the MEP data in two periods. One was in one hour before tumor resection, and the other was in one hour after tumor resection. And the change ratios of MEP amplitude by one operation were described with the ratio of two mean values in each period (MEP amplitude ratio). We classified the muscle strength in six phases using Medical Research Council’s Manual Muscle Testing (MMT). The change of muscle strength were showed by the difference of two MMT values (dMMT) that were measured just before operation and at the time when postoperative awaking enough. All MEP amplitude rate values were classified in each dMMT groups (Fig. 1).
P848 Silent period in the mentalis muscle in healthy subjects and hemifacial spasm M. Ishikawa 1 , N. Kiryu 2 , M. Ikoda 1 , Y. Tanaka 1 Saitama Medical Center, Jichi Medical University, Neurosurgery, Saitama, Japan; 2 Saitama Medical Center, Jichi Medical University, Clinical Physiology, Saitama, Japan 1
Question: Action potentials of a voluntary contracting muscle undergo a transient suppression during continued effort after electrical stimulation of the nerve innervating the muscle. We reported this silent period in the mentalis muscle (J Clin Neurophysiol 2001). 1) How is the excitability of the facial nerve during this silent period? 2) Can the electrical stimulation of the zygomatic branch not innervating the mentalis muscle induce this silent period in the mentalis muscle in patinets with hemifacial spasm? Methods: The marginal mandibular branch 1) or the zygomatic branch 2) of the facial nerve was stimulated at a frequency of 1Hz, a stimulus intensity of supramaximum during slight voluntary contraction of the mentalis muscle and the baseline contained evidence of random muscle activity was obtained electromyographically in the mentalis muscle. 1) To estimate
Figure 1. The relationship between the change of MEP amplitude and the change of muscle strength by one surgery.
Result: Between adjacent dMMT groups, the significant difference was not found in two-side statistical test. However, the mean and median values of the dMMT group which muscle strength more decreased were smaller. We found the positive relation between the change of MEP amplitude by one surgery and postoperative muscle strength (Fig. 2).
Poster session 48. Excitability of nerve and muscle P843 Influence of anesthetic agents on sensory nerve excitability testing in mice Y. Osaki, H. Nodera, Y. Shimatani, B. Chimeglkham, R. Kaji Tokushima university, neurology, Tokushima, Japan Introduction: Nerve excitability study in experimental animals can directly test a hypothesis at a molecular level by a specific pharmacological agent or a genetic model. Unlike human subjects, animal study is often performed under anesthesia, however, the anesthetic effects on peripheral nerve excitability has not been fully investigated. Methods: We performed nerve excitability testing under two commonly used anesthetic agents in normal male mice: (1) 1.5% isoflurane inhalation (N=10) and (2) the triple agents – medetomidine (0.3 mg/kg), midazoram (4 mg/kg) and btorphanol (5 mg/kg) – intraperitoneal injection (N=10). Sensory nerve at the tail was orthodromically recorded, immediately after the animal was under control for maximal duration of 2 hours to assess the time course of the excitability changes. QtracS software (Digitimer, UK) was used. Result: Threshold changes by long hyperpolarizing stimulation (i.e., threshold electrotonus and current-threshold relationship) increased approximately 30 minutes after induction of anesthesia that sustained thereafter. By contrast, recovery cycle, strength-duration time constant and depolarizing threshold electrotonus showed no remarkable change during the recording. Conclusion: The results suggest anesthetic blockade of HCN channels which are activated by long hyperpolarizing current. When we assess the nerve excitability in experimental animals, the influence of anesthesia on nerve excitability should be taken into account.
P844 H-reflex recovery cycle as an electrophysiological correlate of spasticity A. Karakus 1 , B. Cengiz 1 , M. Zinnuroglu 2 1 Gazi University, Neurology, Ankara, Turkey; 2 Gazi University, Physical Medicine and Rehabilitation, Ankara, Turkey Objective: To investigate correlation between spasticity and spinal cord excitability, the recovery cycle of the H reflex (HRRC) was assessed using novel threshold tracking method. Method: A subset of patients with spastic paraparesis (11) were recruited for the study. Before HRRC, muscle strength and spasticity (with modified Ashworth Scale) of lower limbs were evaluated. HRRC was performed with two equal suprathreshold stimulus paradigm with different (between 2-200 ms) interstimulus intervals (ISIs) by using the threshold tracking method. Results: Preliminary results indicate that there is good correlation between inhibition of HRRC at ISIs of 56-2 ms and modified Ashworth scale scores (r>0.740). Conclusions: Findings of the study suggest that HRRC using the novel threshold tracking method is a good electrophysiological correlate of spasticity.
S267
Methods: We performed excitability studies of the median nerve at the wrist in 5 MMN and 7 CIDP patients with nerve conduction abnormalities in the forearm segment and 10 normal controls. Tests were performed following warming to 37°C and cooling to 25°C. Results in MMN and CIDP were compared with those in normal controls. Inverse modeling was used to interpret the results. Results: Following warming, MMN patients showed fanning-out and increased accommodation of threshold electrotonus, shortened refractory period and increased superexcitability. In CIDP, stimulus-response slope was decreased, rheobase was increased, threshold electrotonus showed fanning-out and refractory period was shortened. Inverse modeling showed decreased fast K-conductance, increased myelin conductance and hyperpolarization-activated cation conductance in MMN and increased myelin conductance and hyperpolarization-activated cation conductance in CIDP. Following cooling, changes in excitability-indices were largely similar in all groups. Conclusions: The present findings support permanent axonal hyperpolarization and demyelination in MMN, demyelination in CIDP, and normal effects of cooling on ion-channels in both diseases.
P846 The effect of hand dominance on peripheral nerve excitability Y. Tsuji 1 , Y.-I. Noto 1 , K. Shiga 2 , M. Nakagawa 3 , T. Mizuno 1 1 Graduate School of Medical Science, Kyoto Prefectural University of Medicine, neurology, Kyoto, Japan; 2 Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Medical Education and Primary Care, Kyoto, Japan; 3 North Medical Center, Kyoto Prefectural University of Medicine, Kyoto, Japan Question: The threshold tracking technique has been used for exploring the peripheral nerve excitability in normal subjects and patients with various neuromuscular diseases. Murray et al. reported that nerve excitability of the median and ulnar nerve was significantly different in normal subjects by using threshold tracking. However, it is unclear whether hand dominance can affect the peripheral nerve excitability. The aim of this study is to elucidate whether the properties in nerve excitability of the dominant hands are different from those of the non-dominant hands. Methods: Both median nerves were examined in healthy subjects using Trond NF program with Qtrac® system. Nerve excitability parameters were compared between dominant hands and non-dominant hands. In each individual, the dominant hand was determined by Edinburgh Handedness Inventory.
P845 Interpretation of excitability studies in multifocal motor neuropathy and chronic inflammatory demyelinating polyneuropathy D. Straver 1 , L. van Schelven 2 , L. van den Berg 1 , H. Franssen 1 1 UMC Utrecht, Brain Center Rudolf Magnus, Utrecht, Netherlands; 2 UMC Utrecht, Medical Technology and Clinical Physics, Utrecht, Netherlands Question: Pathophysiology of multifocal motor neuropathy (MMN) and chronic inflammatory demyelinating polyneuropathy (CIDP) is not fully understood. Nerve excitability studies have been performed to improve understanding of disease mechanisms, but results were difficult to interpret. Although cold paresis is frequently reported in MMN and was attributed to depolarized nerve lesions, effects of cooling on excitability were not previously studied in MMN and CIDP. The aim of this study was to explore nerve excitability in MMN and CIDP to assess changes in passive and active axonal membrane properties.
Figure 1. Comparison of the threshold tracking in dominant hand and non-dominant hand.
S268
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
Results: All subjects (n=10, 8 men and 2 women; aged 24-45 years) were right-handed. Strength-duration time constant (SDTC) demonstrated no difference between dominant hands [0.37±0.084 ms] and non-dominant hands [0.37±0.074 ms] (p=0.872). Second, all parameters in threshold electrotonus tracking showed no difference in hand dominance (TEh [90–100ms]; −117.3±13.6% [dominant hands], −116.4±7.8% [non-dominant hands], p=0.846, TEd [90–100ms]; 44.6±4.6% [dominant hands], 45.0±3.0% [non-dominant hands], p=0.794). In recovery cycle testing, no side difference was noted both in superexcitability and in subexcitability. Conclusions: Nerve excitability measures in dominant hands were not different from those in non-dominant hands. This study provides the practical basis for the hypothesis that it may be unnecessary to consider the handedness when exploring nerve excitability in patients with neuromuscular diseases.
the excitability of the facial nerve, the facial F waves were elicited by the paired stimulation (interstimulus interval (ISI): 40ms (during voluntary contraction of the silent period) or 80ms (during late phase of the silent period)). 2) To examine the silent period of the hemifacial spasm, the baseline activity was obtained in the mentalis muscle following the zygomatic branch stimulation. Results: 1) The F waves elicited by the second stimulation were enhanced (ISI: 40ms) and inhibited (ISI: 80ms). 2) The silent period was recorded in the mentalis muscles by the zygomatic branch stimulation in the patients with hemifacial spasm. Conclusions: The silent period expresses the facial nerve excitability as well as the facial nerve F waves elicited by paired stimulation. The silent period was recorded by not innervating nerve stimulation in the hemifacial spasm as well as the abnormal muscle responses.
P847 Signs of motoneuronal hyperexcitability with reinnervation after peripheral nerve lesions
P849 The relationship between muscle strength and transcranial stimulation motor evoked potential
M. Neves Cardoso 1 , C. Krarup 2 , J. Valls-Solé 3 1 Centro Hospitalar do Porto, Neurophysiology, Oporto, Portugal; 2 Copenhagen University Hospital, Clinical Neurophysiology, Copenhagen, Denmark; 3 Hospital Clinic, University of Barcelona, EMG Unit, Neurology, Barcelona, Spain
D. Mishima, T. Suwa, K. Mii National Hospital Organization Sagamihara National Hospital, Neurosurgery, Sagamihara, Japan
Question: Several abnormalities complicate reinnervation after complete section of a peripheral nerve. Axonal growth may lead to abnormal branching and reinnervation errors. Enhancement of excitability at motoneuronal level may entail generation of abnormal reflex responses. We examined the neurophysiological characteristics of these two types of abnormalities in 20 patients with complete traumatic section of either ulnar or median nerves. Methods: Patients were examined at predetermined periods between 3 and 24 months after the lesion. We recorded the motor and sensory nerve action potentials and performed needle electromyography in the affected muscles. For comparison, we also analyzed the motor and sensory nerve conduction of the same nerves in the contralatreral (unimpaired) extremity. For the analysis of abnormal sensorimotor responses, we recorded with needle EMG the muscle action potentials elicited by cutaneous stimulation to territories supplied by the impaired nerve and by unimpaired neighbour nerves. Results: We recorded two types of responses: The first response, of relatively short latency (12 to 45 ms), consistently appeared at the same latency with repeated stimuli. The second response, of longer latency (48 to 114 ms), appeared less constantly and had a noticeable latency variation with repeated stimuli. Only the second response was elicited with stimuli applied to unimpaired nerves. In both cases, response latency progressively shortened with successive exams. Conclusions: At least two types of abnormal muscle action potentials can be elicited by sensory stimuli during reinnervation after a mixed nerve lesion: Axo-axonic or ephaptic responses at relatively short latency and transynaptic reflex responses at longer latency.
Question: Transcranial electrical stimulation Motor evoked potential (TCSMEP) has been used as an intraoperative monitoring of motor functions. But TCS-MEP has inherent variability. This variability has disturbed that we push forward an analysis of TCS-MEP. How can we resolve this variability problem? We tried to show the absolute relationship between muscle strength and TCS-MEP by the unique method. Methods: We hypothesized that the fluctuation of MEP amplitudes took the distribution of the amount according to Gaussian distribution in the same condition. And the mean values of MEP amplitudes were measured within the constant period. The effects on motor tracts were digitized by using the ratio of the mean values that were measured before and after the invasive maneuvers. And we investigated the correlations between those ratios and the changes of muscle strength. TCS-MEP were monitored at 26 operations of 18 intramedurally spinal cord tumor cases. TCS-MEP was in the habit of recording every 10 minutes at the direct manipulation to spinal cord after the dura matter incision. 150 muscles’ data were analyzed. All muscles’ innervation was under the tumor level in spinal cord. We gathered the MEP data in two periods. One was in one hour before tumor resection, and the other was in one hour after tumor resection. And the change ratios of MEP amplitude by one operation were described with the ratio of two mean values in each period (MEP amplitude ratio). We classified the muscle strength in six phases using Medical Research Council’s Manual Muscle Testing (MMT). The change of muscle strength were showed by the difference of two MMT values (dMMT) that were measured just before operation and at the time when postoperative awaking enough. All MEP amplitude rate values were classified in each dMMT groups (Fig. 1).
P848 Silent period in the mentalis muscle in healthy subjects and hemifacial spasm M. Ishikawa 1 , N. Kiryu 2 , M. Ikoda 1 , Y. Tanaka 1 Saitama Medical Center, Jichi Medical University, Neurosurgery, Saitama, Japan; 2 Saitama Medical Center, Jichi Medical University, Clinical Physiology, Saitama, Japan 1
Question: Action potentials of a voluntary contracting muscle undergo a transient suppression during continued effort after electrical stimulation of the nerve innervating the muscle. We reported this silent period in the mentalis muscle (J Clin Neurophysiol 2001). 1) How is the excitability of the facial nerve during this silent period? 2) Can the electrical stimulation of the zygomatic branch not innervating the mentalis muscle induce this silent period in the mentalis muscle in patinets with hemifacial spasm? Methods: The marginal mandibular branch 1) or the zygomatic branch 2) of the facial nerve was stimulated at a frequency of 1Hz, a stimulus intensity of supramaximum during slight voluntary contraction of the mentalis muscle and the baseline contained evidence of random muscle activity was obtained electromyographically in the mentalis muscle. 1) To estimate
Figure 1. The relationship between the change of MEP amplitude and the change of muscle strength by one surgery.
Result: Between adjacent dMMT groups, the significant difference was not found in two-side statistical test. However, the mean and median values of the dMMT group which muscle strength more decreased were smaller. We found the positive relation between the change of MEP amplitude by one surgery and postoperative muscle strength (Fig. 2).