Abductor Digiti Minimi Muscle Research Articles

Anatomical study of the human sole of the foot by 4-dimensional CT angiographic vascular imaging – its suitability as composite tissue allotransplantation graft for foot defects

The reconstruction of the weight-bearing sole is a challenge for every plastic surgeon. Composite tissue allotransplantation (CTA) of the sole of the foot may be a good therapeutic option for patients with large defects in the weight bearing area of the foot. As part of the preparation for a CTA of the sole, we sought to prepare for technical aspects related to preparation and perfusion of the human sole, on the basis of a systematic anatomical study, in combination with 4-dimensional computed tomography-angiography. An anatomical study was performed on 10 cadaver feet. CT images of the feet were prepared in a GE light speed 16-line computed tomogram (CT) before and after the preparation of the sole. After each CT scan, contrast medium was injected in 0.2 ml steps over the posterior tibial artery. Good images of the vessels of the sole from all 10 feet were achieved after recovery of the posterior tibial artery with accessory veins, the tibial nerve, the medial calcaneal branches from the posterior tibial artery, the abductor hallucis, digitorum brevis, abductor digiti minimi, lumbricales and interossea plantares muscles, even after preparation of the soles. With this systematic anatomical preparation of the soles of the feet from human cadaver preparations, in combination with 4-dimensional CT angiography, we were able to demonstrate the technical feasibility of sole transplantation. CT angiography should be performed preoperatively, in order to demonstrate that the vessels are patent as pedicle for the sole of the foot.

Recurrent CSPs after Transcranial Magnetic Stimulation of Motor Cortex in Restless Legs Syndrome

Aims. The aim of this study was to investigate the motor control and central silent period (CSP) in restless legs syndrome (RLS). Methods. Transcranial magnetic stimulation was focused on the dominant and nondominant hemispheric areas of motor cortex in six subjects with RLS and six controls. The responses were recorded on the contralateral abductor digiti minimi (ADM) and tibialis anterior (TA) muscles with intramuscular needle electrodes. Results. No significant differences were found in the motor conduction or central motor conduction time, in the latency, or in the duration of the CSPs between or within the groups, but multiple CSPs were observed in both groups. The number of the CSPs was significantly higher in both ADMs and in the dominant TA (P ≤ 0.01) in the RLS group compared to the controls. Conclusion. Descending motor pathways functioned correctly in both groups. The occurrence of the recurrent CSPs predominantly in the RLS group could be a sign of a change of function in the inhibitory control system. Further research is needed to clarify the role of the intramuscular recording technique and especially the role of the subcortical generators in the feedback regulation of the central nervous system in RLS.

Focal hand dystonia

To examine whether the corticospinal system emanating from the primary motor cortex may be organized to facilitate generation of dystonic movements. In this cross-sectional observational study, finger movement (FM) representations were assessed in 10 patients with focal hand dystonia (FHD) and 10 matched healthy controls by transcranial magnetic stimulation during rest. Evoked finger movements of the right hand were recorded using an instrumented data glove. Patterns of finger joint movements were analyzed using cluster analysis. Principal component analysis and centers of gravity for finger movement representations and motor evoked potentials recorded from the abductor pollicis brevis and abductor digiti minimi muscles were computed. For comparison, high-resolution somatosensory evoked potentials (SSEP) were recorded after electrical stimulation of the thumb (D1) or little finger (D5) in the same patients. Source reconstruction for the N20 SSEP component was performed using a dual-dipole model. Stimulation of the resting motor cortex did not reveal overt abnormalities in FHD, neither with respect to finger joint movement patterns nor with respect to the topologic organization of finger movements or intrinsic hand muscle representations. However, in line with previous reports, the distance between the dipole sources of D1 and D5 in the somatosensory cortex (S1) was smaller in patients with FHD, suggesting disruption of homuncular finger representations in S1. Our findings may imply that abnormality of motor organization in focal hand dystonia arises principally only during activation, when abnormal somatosensory representations are functionally integrated.

Emotional valence modulates putative mirror neuron activity

Mirror neurons are thought to facilitate emotion processing, but it is unclear whether the valence of an emotional presentation (positive or negative) can influence subsequent mirror neuron activity. Participants completed a transcranial magnetic stimulation experiment that involved stimulation of the primary motor cortex, and electromyography recording from contralateral hand muscles. This was performed while participants viewed videos of either a static hand or a transitive hand action preceded by either a positive or negative stimulus. Corticospinal excitability facilitation during action observation was significantly greater following the presentation of negative (relative to positive) stimuli; this was evident for the first dorsal interosseous muscle (which was central to the observed grasp), but not for the abductor digiti minimi muscle. This study provides evidence that emotional valence can modulate mirror neuron activity, which may reflect an adaptive mechanism.

Increased probability of repetitive spinal motoneuron activation by transcranial magnetic stimulation after muscle fatigue in healthy subjects

Triple stimulation technique (TST) has previously shown that transcranial magnetic stimulation (TMS) fails to activate a proportion of spinal motoneurons (MNs) during motor fatigue. The depression in size of the TST response, but no attenuation of the conventional motor-evoked potential, suggested increased probability of repetitive spinal MN activation during exercise, even if some MNs failed to discharge by the brain stimulus. Here we used a modified TST [quadruple stimulation (QuadS) and quintuple stimulation (QuintS)] to examine the influence of fatiguing exercise on second and third MN discharges after a single TMS in healthy subjects. This method allows an estimation of the percentage of double and triple discharging MNs. Following a sustained contraction of the abductor digiti minimi muscle at 50% maximal force maintained to exhaustion, the size of QuadS and QuintS responses increased markedly, reflecting that a greater proportion of spinal MNs was activated two or three times by the transcranial stimulus. The size of QuadS responses did not return to precontraction levels during 10-min observation time, indicating long-lasting increase in excitatory input to spinal MNs. In addition, the postexercise behavior of QuadS responses was related to the duration of the contraction, pointing to a correlation between repeated activation of MNs and the subject's ability to maintain force. In conclusion, the study confirmed that an increased fraction of spinal MNs fire more than once in response to TMS when the muscle is fatigued. Repetitive MN firing may provide an adaptive mechanism to maintain motor unit activation and task performance during sustained voluntary activity.

Assessment of the Electrophysiological Properties of the Muscle Fibers of a Transplanted Hand

The muscle fibers in a transplanted hand remain denervated for a long period of time after the transplant. This prolonged inactivity may change the electrophysiological membrane properties of muscle fibers, as observed in long-term denervation. We investigated whether electrophysiological properties of the muscle fibers are preserved in a transplanted hand even after several months of denervation. Specifically, we assessed the dependence of muscle fiber conduction velocity (CV) on discharge rate in motor units of the abductor digiti minimi muscle. Surface electromyography signals were recorded from the transplanted hand of a patient who was 35 years of age at the time of the transplant. In each of 11 experimental sessions performed over a period of 23 months after the transplant, the subject was asked to linearly increase the activation or to maintain a maximum activation of the abductor digiti minimi muscle for 60 sec. Individual motor unit action potentials were identified from the electromyography recordings and muscle fiber CV was estimated for each action potential as a function of the time interval separating the action potential from the preceding discharge (interspike interval [ISI]). The baseline (ISI >1000 msec) CV was 3.8±0.3 m/sec. CV decreased monotonically with increasing ISI (R=0.95). For ISI in the range 0 to 10 msec, muscle fiber CV was 24.9%±16.3% higher than the baseline value (P<0.05). The results indicate that in the investigated muscle, the baseline value of CV and its dependency on discharge rate were similar as in able-bodied individuals, despite a period of several months of denervation.

Low-frequency oscillations of the neural drive to the muscle are increased with experimental muscle pain

We investigated the influence of nociceptive stimulation on the accuracy of task execution and motor unit spike trains during low-force isometric contractions. Muscle pain was induced by infusion of hypertonic saline into the abductor digiti minimi muscle of 11 healthy men. Intramuscular EMG signals were recorded from the same muscle during four isometric contractions of 60-s duration at 10% of the maximal force [maximal voluntary contraction (MVC)] performed before injection (baseline), after injection of isotonic (control) or hypertonic saline (pain), and 15 min after pain was no longer reported. Each contraction was preceded by three 3-s ramp contractions from 0% to 10% MVC. The low-frequency oscillations of motor unit spike trains were analyzed by the first principal component of the low-pass filtered spike trains [first common component (FCC)], which represents the effective neural drive to the muscle. Pain decreased the accuracy of task performance [coefficient of variation (CoV) for force: baseline, 2.8 ± 1.8%, pain, 3.9 ± 1.8%; P < 0.05] and reduced motor unit discharge rates [11.6 ± 2.3 pulses per second (pps) vs. 10.7 ± 1.7 pps; P < 0.05]. Motor unit recruitment thresholds (2.2 ± 1.2% MVC vs. 2.4 ± 1.6% MVC), interspike interval variability (18.4 ± 4.9% vs. 19.1 ± 5.4%), strength of motor unit short-term synchronization [common input strength (CIS) 1.02 ± 0.44 vs. 0.83 ± 0.22], and strength of common drive (0.47 ± 0.08 vs. 0.47 ± 0.06) did not change across conditions. The FCC signal was correlated with force (R = 0.45 ± 0.06), and the CoV for FCC increased in the painful condition (5.69 ± 1.29% vs. 7.83 ± 2.61%; P < 0.05). These results indicate that nociceptive stimulation increased the low-frequency variability in synaptic input to motoneurons.

Evaluation of spinal and bulbar muscular atrophy by the clustering index method

A reliable electrophysiological marker for clinical trials is increasingly needed in spinal and bulbar muscular atrophy (SBMA). We previously developed a quantitative analysis method for surface electromyography (SEMG), the clustering index (CI) method. Our purpose was to test the utility of the CI method for evaluating lower motor neuron involvement in SBMA patients. Subjects included 29 SBMA patients and 27 healthy controls. The recording electrode was placed over the abductor digiti minimi (ADM) muscle with a proximal reference. The Z-score, based on the CI method, was compared with compound muscle action potential (CMAP) amplitude and motor unit number estimation (MUNE), with regard to sensitivity. The Z-scores of the CI method, CMAP amplitude, and MUNE were abnormal in 100%, 72%, and 93% of the patients, respectively. Interrater reliability of the CI method was sufficiently high. The CI method is promising as a non-invasive electrophysiological marker in SBMA.

Treatment of a Type 3B Hypoplastic Thumb Using Extra Phalanges From the Contralateral Duplicated Thumb: Case Report

A boy was born with a right duplicated thumb (Wassel type 6) and a left radial club hand (type 3) associated with a hypoplastic thumb (type 3B). He underwent surgical centralization of the left wrist when he was 13 months old. At age 38 months, he underwent reconstruction of the carpometacarpal joint of the hypoplastic left thumb. This procedure involved transplantation of the radial ray of the right duplicated thumb to the base of the left thumb. When he was 6 years old, the patient underwent an abductor digiti minimi muscle transfer to create opposition for the left thumb and deepening of the first web. At the final follow-up, he could grasp items in the first web space and pick up small items between the thumb and other digits of the left hand. The treatment represents a method of using otherwise discarded tissues for effective reconstruction.

Mirroring avatars: dissociation of action and intention in human motor resonance

Observation of others' actions induces a subliminal activation of motor pathways (motor resonance) that is mediated by the mirror neuron system and reflects the motor program encoding the observed action. Whether motor resonance represents the movements composing an action or also its motor intention remains of debate, as natural actions implicitly contain their motor intentions. Here, action and intention are dissociated using a natural and an impossible action with the same grasping intention: subjects observe an avatar grasping a ball using either a natural hand action ('palmar' finger flexion) or an impossible hand action ('dorsal' finger flexion). Motor-evoked potentials (MEPs), elicited by single transcranial magnetic stimulation of the hand area in the primary motor cortex, were used to measure the excitability modulation of motor pathways during observation of the two different hand actions. MEPs were recorded from the opponens pollicis (OP), abductor digiti minimi (ADM) and extensor carpi radialis (ECR) muscles. A significant MEP facilitation was found in the OP, during observation of the grasping phase of the natural action; MEPs in the ADM were facilitated during observation of the hand opening phase of the natural action and of both opening and grasping phases of the impossible action. MEPs in the ECR were not affected. As different resonant responses are elicited by the observation of the two different actions, despite their identical intention, we conclude that the mirror neuron system cannot utilize the observer's subliminal motor program in the primary motor cortex to encode action intentions.

Central motor conduction studies and diagnostic magnetic resonance imaging in children with severe primary and secondary dystonia

Dystonia in childhood has many causes. Imaging may suggest corticospinal tract dysfunction with or without coexistent basal ganglia damage. There are very few published neurophysiological studies on children with dystonia; one previous study has focused on primary dystonia. We investigated central motor conduction in 62 children (34 males, 28 females; age range 3-19y, mean age 10y 8mo, SD 4y 8mo) with severe dystonia to evaluate corticospinal tract integrity before consideration for deep brain stimulation. Distal motor and F-wave latencies were measured in the ulnar and/or posterior tibial nerves. Transcranial magnetic stimulation was applied over the motor cortex and motor-evoked potentials were recorded in the activated abductor digiti minimi and/or abductor hallucis muscles. Central motor conduction time (CMCT) was calculated using the F-wave method. CMCT was normal in 50 out of 62 patients; 12 patients showed prolonged CMCT to upper and/or lower limbs. Most children with severe primary and secondary dystonia had normal CMCT, indicating corticospinal tract integrity despite abnormal imaging in 42 out of 50 patients. Abnormal CMCT was found in two out of 12 patients with normal imaging. This study provides new CMCT data for children with severe primary and secondary dystonia. Over 50% of children with evidence of periventricular white-matter damage from magnetic resonance imaging had normal CMCT, challenging traditional pathophysiological models. This is consistent with recent diffusion tensor imaging in children with periventricular white-matter damage, showing disruption of sensory connections rather than corticospinal tract damage. CMCT helps refine our understanding of imaging changes in complex motor disorders of childhood.

Immediate versus delayed electrical stimulation boosts botulinum toxin effect: A pilot study

Movement DisordersVolume 26, Issue 9 p. 1785-1786 Letters: New Observation Immediate versus delayed electrical stimulation boosts botulinum toxin effect: A pilot study† Alessandro Picelli MD, Alessandro Picelli MD Neuromotor and Cognitive Rehabilitation Research Center, Department of Neurological Neuropsychological, Morphological and Movement Sciences, University of Verona Verona, Italy PhD course in Experimental Physical Medicine and Rehabilitation applied to Human Locomotor System, University of Rome “La Sapienza”, Rome, ItalySearch for more papers by this authorNicola Smania MD, Corresponding Author Nicola Smania MD nicola.smania@univr.it Neuromotor and Cognitive Rehabilitation Research Center, Department of Neurological Neuropsychological, Morphological and Movement Sciences, University of Verona Verona, ItalyNeuromotor and Cognitive Rehabilitation Research Center, Department of Neurological, Neuropsychological, Morphological and Movement Sciences, University of Verona, ItalySearch for more papers by this authorIlaria Storti MD, Ilaria Storti MD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this authorDaniele Munari PT, Daniele Munari PT Neuromotor and Cognitive Rehabilitation Research Center, Department of Neurological Neuropsychological, Morphological and Movement Sciences, University of Verona Verona, ItalySearch for more papers by this authorCarla Fontana MD, Carla Fontana MD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this authorAntonio Fiaschi MD, Antonio Fiaschi MD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this authorValter Santilli MD, Valter Santilli MD PhD course in Experimental Physical Medicine and Rehabilitation applied to Human Locomotor System, University of Rome “La Sapienza”, Rome, Italy Department of Physical Medicine and Rehabilitation, University of Rome “La Sapienza”, Rome, ItalySearch for more papers by this authorStefano Tamburin MD, PhD, Stefano Tamburin MD, PhD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this author Alessandro Picelli MD, Alessandro Picelli MD Neuromotor and Cognitive Rehabilitation Research Center, Department of Neurological Neuropsychological, Morphological and Movement Sciences, University of Verona Verona, Italy PhD course in Experimental Physical Medicine and Rehabilitation applied to Human Locomotor System, University of Rome “La Sapienza”, Rome, ItalySearch for more papers by this authorNicola Smania MD, Corresponding Author Nicola Smania MD nicola.smania@univr.it Neuromotor and Cognitive Rehabilitation Research Center, Department of Neurological Neuropsychological, Morphological and Movement Sciences, University of Verona Verona, ItalyNeuromotor and Cognitive Rehabilitation Research Center, Department of Neurological, Neuropsychological, Morphological and Movement Sciences, University of Verona, ItalySearch for more papers by this authorIlaria Storti MD, Ilaria Storti MD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this authorDaniele Munari PT, Daniele Munari PT Neuromotor and Cognitive Rehabilitation Research Center, Department of Neurological Neuropsychological, Morphological and Movement Sciences, University of Verona Verona, ItalySearch for more papers by this authorCarla Fontana MD, Carla Fontana MD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this authorAntonio Fiaschi MD, Antonio Fiaschi MD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this authorValter Santilli MD, Valter Santilli MD PhD course in Experimental Physical Medicine and Rehabilitation applied to Human Locomotor System, University of Rome “La Sapienza”, Rome, Italy Department of Physical Medicine and Rehabilitation, University of Rome “La Sapienza”, Rome, ItalySearch for more papers by this authorStefano Tamburin MD, PhD, Stefano Tamburin MD, PhD Department of Neurological, Neuropsychological Morphological and Movement Sciences Neurology Section, University of Verona Verona, ItalySearch for more papers by this author First published: 29 April 2011 https://doi.org/10.1002/mds.23678Citations: 11 † Relevant conflicts of interest/financial disclosures: : Nothing to report. Full financial disclosures and author roles may be found in the online version of this article. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume26, Issue91 August 2011Pages 1785-1786 RelatedInformation

Origin of far‐field potentials in the ulnar compound muscle action potential

The compound muscle action potential (CMAP) following ulnar nerve stimulation receives a considerable contribution from far-field potentials (FFPs), although their origin is not entirely clear. We investigated this issue using voluntary contractions. In 7 control subjects, we placed multiple recording electrodes over the motor points of ulnar-innervated muscles. We asked the subjects to perform a weak movement corresponding to the action of each muscle, and identified the single motor unit potentials (MUPs) from that muscle. We summed the MUPs from each individual muscle and reconstructed the CMAPs. The reconstructed CMAPs coincided well with the actual ones. The N1, P1, and early N2 components of the FFPs were generated primarily by palmar, but also by dorsal, interosseous muscles. The abductor digiti minimi muscle usually generated positive-negative biphasic FFPs, and the negative FFP generated the late N2 component. These results should prompt a revision of the theory of FFP generation.

Ulnar Nerve Latency at Above-Elbow Stimulation

The purpose of this study was to obtain the latency norms of ulnar nerve stimulating at 10 cm above the elbow as a complementary test of the segmental conduction velocity criteria used in the American Association of Electrodiagnostic Medicine guideline for ulnar neuropathy at the elbow (UNE). This is a cross-sectional study of 100 subjects recruited to the electrodiagnostic laboratory of an academic medical center and a retrospective analysis of 14 symptomatic patients diagnosed with UNE using the American Association of Electrodiagnostic Medicine practice guideline. Sensory nerve action potential and compound muscle action potential were recorded at the fifth finger and abductor digiti minimi muscle, respectively, with 10-cm above-elbow stimulation and with elbow flexion at 90 degrees. The latency values of ulnar nerve, together with the participant's anthropometric data, were measured and correlated. Afterward, these values were compared with latency values from 14 patients with UNE. Sensory peak and motor onset latency at 10-cm above-elbow stimulation showed mean ± SD values of 8.3 ± 0.7 and 8.0 ± 0.7 msecs, respectively. Latencies were highly correlated with finger-to-arm length (r = 0.87 for sensory and 0.84 for motor). The cutoff values (twice the standard deviation plus the mean) for "abnormal" are 9.7 and 9.4 msecs for sensory and motor latencies, respectively. Applying the motor cutoff value (9.4 msecs) for abnormal, 12 of 14 symptomatic UNE cases were categorized as abnormal, with a sensitivity of 86%. All 14 patients with UNE showed latencies beyond the upper limit of 95% confidence interval of predicted value based on finger-to-arm length. This study provides latency norms of ulnar sensory and motor nerves simulating at 10 cm above the elbow. It can be used as a complementary tool to assess the validity of segmental conduction velocity criteria in the electrodiagnosis of UNE.

Central and peripheral components of exercise-related fatigability in myotonic dystrophy type 1

Fatigue frequently occurs in myotonic dystrophy type 1 (DM1), but its pathophysiology remains unclear. This study assessed central and peripheral components of exercise-related fatigability in patients with DM1, compared to controls. Examinations were performed before and after a contraction of the abductor digiti minimi (ADM) muscle sustained for 45 s at 60% of maximal voluntary contraction (MVC). Myoelectric activity was recorded using high spatial resolution surface EMG during twitch stimulations and MVC and was characterized by root mean square, mean power frequency (MPF), and muscle fiber conduction velocity (MFCV). Peripheral nerve excitability was assessed by stimulating the ulnar nerve at the wrist with ADM recordings. Motor cortex excitability testing to transcranial magnetic stimulation included measures of intracortical facilitation and inhibition of motor evoked potentials (MEPs) in ADM muscle. At baseline, patients with DM1 showed altered peripheral nerve and cortical excitability (reduced intracortical facilitation) associated with impaired myoelectric properties. During the fatiguing exercise, the force remained stable, while MPF and MFCV decreased in both DM1 and control groups. After exercise, only refractoriness was reduced in patients with DM1, whereas controls showed marked neuromuscular and cortical changes. Patients with DM1 showed altered excitability of various cortical and neuromuscular components at baseline. However, most of excitability parameters did not vary after exercise in patients with DM1, in contrast to controls. This suggests that excitability properties, frankly altered at baseline, were not prone to be affected further after exercise in patients with DM1.

Macro-EMG and MUNE Changes in Patients with Amyotrophic Lateral Sclerosis: One-Year Follow Up

ABSTRACTObjective: We assessed changes in Motor Units (MU) and extent of MU loss using macro-electromyography (macro-EMG) and Motor Unit Number Estimation (MUNE). Methods: We applied these techniques to a sample of 61 Amyotrophic Lateral Sclerosis (ALS) patients basally (T0) and after 4 (T1), 8 (T2), and 12 (T3) months. Macro Motor Unit Potentials (macro-MUPs) were derived from Biceps Brachii (BB) muscle; MUNE was performed both in BB and Abductor Digiti Minimi (ADM) muscles of the same side. Results: Macro-MUPs area resulted in progressive increase at T1, T2, and T3 with respect to T0. Fiber density (FD) at T3 decreases a bit than at T2. Functioning MUS number decreased in both the muscles throughout the entire follow-up with respect to T0 and the rate of MU decrease was similar in both the muscles, but steeper distally. Conclusions and Significance: Macro-EMG increase and FD decrease suggest that a process of MU rearrangement begins to fall after 8 months of disease course. Combined use of macro-EMG and MUNE techniques in ALS patients allows to track over time changes in muscle MU features and number in face of progressive anterior horn cells death during disease's evolution.

Cerebellar brain inhibition is decreased in active and surround muscles at the onset of voluntary movement

Highly selective activation of the desired muscles for each movement and inhibition of adjacent muscles is attributed to surround inhibition (SI) which differentially modulates corticospinal excitability in active and surrounding muscles. Cerebellar brain inhibition (CBI) is another inhibitory neuronal network which is known to be active at rest and during tonic muscle contraction. The way in which CBI may be modulated at movement onset and its relationship with SI has not previously been investigated. We assessed motor evoked potential (MEP) size and CBI in first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscles at rest and during a simple motor task where FDI was an active muscle and ADM was not involved in the movement (surround muscle). At onset of movement, MEP size in ADM was significantly suppressed, confirming the existence of SI. In contrast, CBI in both muscles was found to be significantly decreased at the onset of the movement. This was confirmed even after adjustments for changes in MEP size occurring due to onset of muscle activity in FDI and the effects of SI in ADM. Our findings fail to functionally link SI with CBI, but they do indicate a non-topographically specific modulation of CBI in association with initiation of voluntary movement.

Electrophysiological features of familial amyloid polyneuropathy in endemic area

The process of deterioration of peripheral nerve function in familial amyloid polyneuropathy (FAP) with amyloidogenic transthyretin (ATTR) Val30Met has not been systematically evaluated hitherto. We performed nerve conduction studies in 69 patients with FAP with ATTR Val30Met from one of the endemic areas in Japan. Sensory conduction velocity (SCV), motor conduction velocity (MCV), the size of the compound muscle action potential (CMAP) and distal latency (DL) were measured in the ulnar and tibial nerves. SCV was evaluated using the orthodromic method with needle recording electrodes. These electrophysiological parameters were compared with clinical stage of FAP and duration of neuropathy. When subjects noted minimal neuropathic symptoms only in the feet, motor and sensory nerve function in both the hands and feet had already been disturbed. Sensory nerve action potential on the foot disappeared more rapidly than CMAP. CMAP on foot muscle rapidly decreased during the initial 2 years and completely disappeared within 10 years. The duration of illness and deterioration parameters (CMAP of the abductor digiti minimi muscle, MCV and SCV of the ulnar nerve and DL of both ulnar and tibial nerves) were linearly correlated. CMAP was the most sensitive and reliable parameter to evaluate motor nerve degeneration in FAP.

Ulnar Nerve Conduction Study of the First Dorsal Interosseous Muscle in Korean Subjects

ObjectiveTo derive normative values for ulnar nerve conduction study of the active recording electrode on the first dorsal interosseous muscle (FDI) and the reference electrode on the proximal phalanx of the thumb.MethodUlnar nerve motor conduction study with FDI and abductor digiti minimi muscle (ADM) recording was performed in 214 hands of 107 healthy subjects. Ulnar NCS was performed with 2 different recording electrode montages (ADM-base of 5th finger; FDI-thumb) and differences in latency and amplitude were compared. Using this technique, the initial positivity of ulnar compound muscle action potential (CMAP) was not observed in any response with FDI recording.ResultsThe maximal values for distal motor latency to the ADM and FDI muscle were 3.8 ms and 4.4 ms, respectively. The maximal difference of distal motor latency between the bilateral FDI recordings was 0.6 ms. The maximal ipsilateral latency difference between ADM and FDI was 1.4 ms.ConclusionPlacement of the reference electrode on the thumb results in a CMAP without an initial positivity and the normative values obtained may be useful in the diagnosis of ulnar neuropathy at the wrist.

Cortico-Cortical Connectivity between Right Parietal and Bilateral Primary Motor Cortices during Imagined and Observed Actions: A Combined TMS/tDCS Study

Previous transcranial magnetic stimulation (TMS) studies showed functional connections between the parietal cortex (PC) and the primary motor cortex (M1) during tasks of different reaching-to-grasp movements. Here, we tested whether the same network is involved in cognitive processes such as imagined or observed actions. Single pulse TMS of the right and left M1 during rest and during a motor imagery and an action observation task (i.e., an index–thumb pinch grip in both cases) was used to measure corticospinal excitability changes before and after conditioning of the right PC by 10 min of cathodal, anodal, or sham transcranial direct current stimulation (tDCS). Corticospinal excitability was indexed by the size of motor-evoked potentials (MEPs) from the contralateral first dorsal interosseous (FDI; target) and abductor digiti minimi muscle (control) muscles. Results showed selective ipsilateral effects on the M1 excitability, exclusively for motor imagery processes: anodal tDCS enhanced the MEPs’ size from the FDI muscle, whereas cathodal tDCS decreased it. Only cathodal tDCS impacted corticospinal facilitation induced by action observation. Sham stimulation was always uneffective. These results suggest that motor imagery, differently from action observation, is sustained by a strictly ipsilateral parieto-motor cortex circuits. Results might have implication for neuromodulatory rehabilitative purposes.