Mitsuhiko Kodama

Premotor potential study in carpal tunnel syndrome

Introduction: Premotor potentials (PMPs) precede compound muscle action potentials evoked from the second lumbrical muscle after median nerve stimulation. Although PMP has been identified as a median sensory nerve action potential, few reports have documented the significance of PMP parameters for diagnosing carpal tunnel syndrome (CTS). Methods: We investigated the relationships between PMP parameters and results of 6 standard median nerve conduction studies in 74 CTS hands. Results: Significant correlations were noted in all comparisons. PMP conduction velocity was strongly correlated with the sensory conduction velocity between wrist and digit 2 (r2 = 0.91). Moreover, PMP parameters were significantly correlated with neurophysiological severity of CTS. Conclusion: Measuring PMP parameters with a second lumbrical–interosseous study may be useful for diagnosing CTS. Muscle Nerve, 2012

Effect of low-frequency repetitive transcranial magnetic stimulation combined with physical therapy on L-dopa-induced painful off-period dystonia in Parkinson's disease.

Previous research has shown that low-frequency repetitive transcranial magnetic stimulation over the primary motor area and supplementary motor area can reduce l-dopa-induced dyskinesias in Parkinsons disease; however, it involved only patients with peak-dose or diphasic dyskinesia. We report a case of a patient with severely painful off-period dystonia in the unilateral lower limb who underwent 0.9-Hz subthreshold repetitive transcranial magnetic stimulation over contralateral primary motor area and supplementary motor area. Repetitive transcranial magnetic stimulation over the primary motor area significantly reduced the painful dystonia and walking disturbances but repetitive transcranial magnetic stimulation over the supplementary motor area did not. The cortical silent period also prolonged after repetitive transcranial magnetic stimulation over the primary motor area. At 5 mos of approximately once a week repetitive transcranial magnetic stimulation over the primary motor area, the Unified Parkinsons Disease Rating Scale motor score also improved. This report shows that repetitive transcranial magnetic stimulation over the inhibitory primary motor area can be useful for rehabilitating patients with Parkinsons disease with off-period dystonia and suggests that this treatment should be further verified in such patients.

Modulation of cortical and spinal inhibition with functional recovery of upper extremity motor function among patients with chronic stroke

PURPOSE We hypothesized that recovery of upper extremity motor function is associated with reduction of intracortical inhibition and improved reciprocal inhibition. This study examines the relationships of functional recovery in chronic stroke with the intracortical inhibition and spinal reciprocal inhibition. METHODS Participants were 61 patients with chronic hemiparetic stroke. The participants were applied hybrid assistive neuromuscular dynamic stimulation (HANDS) therapy for 3 weeks. The Fugl-Meyer test upper extremity motor score (FM) and modified Ashworth scale (MAS) were assessed before (T0), immediately after (T1) and 3 months after (T2) the end of HANDS therapy. A paired pulse TMS paradigm was applied to assess short intracortical inhibition (SICI). Reciprocal inhibition (RI) was assessed with H reflex conditioning-test paradigm. RESULTS FM and MAS were improved until T2. The change of FM from T0 to T2 was positively correlated with the change in affected SICI from T0 toT1. The change of wrist MAS from T0 to T1 was positively correlated with the change of RI. CONCLUSIONS In chronic stroke patients with moderate or severe hemiparesis, well-recovered patients showed disinhibition of ipsilesional hemisphere and increased resiprocal inhibition of forearm.

The origin of the premotor potential recorded from the second lumbrical muscle in normal man

OBJECTIVE When recording with a palm electrode, a premotor potential precedes the compound muscle action potential (CMAP), evoked from the second lumbrical (2L) muscle following median nerve stimulation. The purpose of this study was to determine the origin of the premotor potential from the 2L. METHODS We recorded potentials with multi-channel electrodes in the palm and finger in a bipolar or referential manner, stimulating the second digit or median nerve at the wrist. RESULTS We recorded the traveling nearfield sensory nerve action potential (SNAP) and stationary negative potential in the palm. The peak latency of the stationary negative potential was the same as the one of the near-field potential of the digital sensory fibers at the base of the second finger. The onset of the premotor potential from the 2L muscle is aligned to the palmar SNAP in a bipolar manner by antidromic stimulation. CONCLUSIONS We conclude that the premotor potential from the 2L muscle is composed of a SNAP arising from antidromically activated palm sensory branches and a far-field potential generated by the median digital nerve fibers as they pass from the palm into the second finger. SIGNIFICANCE Our results might be useful for evaluating the 2L-interossei test for diagnosing carpal tunnel syndrome.

Swallowing appliance: intraoral reshaping prosthesis for dysphagia secondary to oral floor cancer: a pilot study.

ABSTRACTPatients with oral floor cancer often have difficulty swallowing solid foods. The aim of this study was to improve the propulsion of solid foods using a swallowing appliance (SW-A). Subjects comprised three patients with oral floor cancer who had undergone curative surgery. Each participant was asked to swallow gelatin under three conditions: without an SW-A, with a maxillary SW-A, and with both maxillary and mandibular SW-As. This procedure was repeated thrice with three volumes of gelatin (2.5, 5, and 7.5 ml), with videofluorographic swallowing study. Swallowing was assessed on the basis of whether the participant could propel the gelatin from the oral cavity to the pharynx. No subject could propel 2.5 ml of gelatin to the pharynx without an SW-A or with only a maxillary SW-A in place. When both SW-As were used, all subjects could propel all three volumes of gelatin. The mandibular SW-A complemented the compensatory effects of the maxillary SW-A.

B-10. Electrodiagnostic studies in entrapment neuropathy

Electrodiagnosis of entrapment neuropathy at the upper limb is important to determine the treatment procedure. The median sensory nerve conduction studies and median nerve motor nerve distal latency have conventionally been performed for the diagnosis of carpal tunnel syndrome (CTS), but their sensitivities are not always sufficient. As a result of our research in 104 hands with CTS symptoms, both the ring finger test and second lumbrical–interossei comparison test had especially high sensitivity (92%), and this result supports the practice parameters recommended by the Japanese Society of Neurological Therapeutics. Exact localization of the lesion by electrodiagnosis in patients with ulnar neuropathy at the elbow (UNE) is often difficult because other disorders may mimic its symptoms (e.g., cervical lesion, brachial plexopathy, and Guyon’s canal syndrome). In one of our studies, sensitivity of the ulnar nerve motor nerve conduction velocity across the elbow lacked accuracy (54%). Meanwhile, the short-segment incremental study had the highest sensitivity (82%), maintaining high specificity (95%). In extreme UNEs, the combination of sensory nerve conduction studies evoked from the dorsal ulnar cutaneous branch and the medial antebrachial cutaneous nerve may be helpful in the exclusion of other disorders.

Quantitative evaluation of age-related decline in control of preprogramed movement

In this paper, we examined the age-related changes in control of preprogramed movement, with emphasis on its accuracy. Forty-nine healthy subjects participated in this study, and were divided into three groups depending on their ages: the young group (20–39 years) (n = 16), the middle-age group (40–59 years) (n = 16), and the elderly group (60–79 years) (n = 17). We asked the subjects to perform step-tracking movements of the wrist joint with a manipulandum, and recorded the movements. We evaluated the accuracy of control of preprogramed movement in the three groups in terms of the primary submovement, which was identified as the first segment of the step-tracking movement based on the bell-shaped velocity profile, and calculated the distance between the end position of the primary submovement and the target (i.e. error). The error in the young group was found to be significantly smaller than that in the middle-age and elderly groups, i.e., the error was larger for the higher age groups. These results suggest that young subjects have better control of preprogramed movement than middle-age or elderly subjects. Finally, we examined the temporal property of the primary submovement and its age-related changes. The duration of the primary submovement tended to be longer for the aged groups, although significance was reached only for the elderly group. In particular, the ratio of the duration of the primary submovement to total movement time tended to be lower for the aged groups, suggesting that the proportion of additional movements that are required to compensate for the incomplete control in the preprogramed movement, which are under feedback control, was higher for the aged groups. Consequently, our results indicate that the distance between the end point of the primary submovement and the target center (i.e. error) in the step-tracking movement is a useful parameter to evaluate the age-related changes in control of preprogramed movement.

Feeling of Bodily Congruence to Visual Stimuli Improves Motor Imagery Based Brain-Computer Interface Control

Motor imagery based Brain-Computer Interface (BCI) utilizes an electrophysiological phenomenon of EEG power decrease in alpha frequency band, but its larger inter-subject variability limits the practical use. Here we tested three types of visual feedback objects in BCI from abstract to realistic scenarios during motor imagery to see its effect on self-induced changes of EEG power decrease. Double case study in hemiplegic stroke participants was also conducted to check its feasibility as neuro-facilitatory technique on the motor system. We found that a first person perspective of realistic visual feedback, which copies the participant’s mental image, assisted the user to perform motor imagery resulting in generation of large EEG power decrease. The same result was found also in hemiplegic stroke patients. This study has clear implications for both the mechanism of mental process of motor imagery and the influence of feedback type on BCI performance.

31. Modified second lumbrical-interossei method

This study was aimed to assess a correlation of event-related desynchronization (ERD) with primary motor cortex (M1) excitability during hand motor imagery. M1 excitability was tested by motor evoked potentials (MEPs), intracortical inhibition (ICI) and intracortical facilitation (ICF), using transcranial magnetic stimulation (TMS). Twenty healthy subjects were recruited in this study. Each subject performed 30 trials comprising 7 s of rest followed by 5 s of motor imagery of either right wrist flexion or extension. Subjects received real-time visual feedback of the ERD magnitude of electroencephalogram signals recorded over the hand area of the left M1. TMS was applied to the left M1 when ERD exceeded 5% or 15% thresholds during motor imagery. MEP size, ICI and ICF were recorded from the agonist muscle of the motor imagery. During hand motor imagery with ERD, MEP sizes increased and ICI reduced (p < 0.05), but there was no significant change in ICF. The changes of MEP-size and ICI were correlated with ERD magnitude. Our findings suggest that ERD magnitude may indicate changes of M1 excitability.

Realistic visual feedback enhances event-related desynchronization during feedback-regulated hand motor imagery

regression, called smooth sparse regression, which has a spatio-temporal “smoothing” prior that encourages weights that are close in time and space to have similar values. This causes the classifier to select spatio-temporally continuous groups of features, whereas standard sparse regression classifiers often select a scattered collection of independent features. We applied the proposed method to both simulation data and real MEG data from two separate experiments. We found that the method consistently increases classification accuracy, and produces weight vectors that are more meaningful from a neuroscientific perspective. Research fund: JST PRESTO.