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Study Design Case report. Introduction A severe wrist fracture can cause permanent physical disabilities and deformities, leading to limit patients in their occupation and social environment. Purpose of the Study We aim at presenting a treatment protocol and the functional outcome of a patient with severe clinical state after a rare wrist fracture. Methods We provided physical therapy intervention associated with serious games for muscle strengthening. Results and Discussion There was an increase in strengthening and a decrease in Disability of the Arm, Shoulder and Hand score and Patient Rated Wrist Evaluation scores. The International Classification of Functioning scores have changed from severe to light or to absent in many of the domains. Conclusion The use of serious games combined with a conventional physical therapy intervention played a fundamental role in recovery and return to work activities, and there was also an important recovery of general health condition.

Purpose Targeted muscle reinnervation (TMR) has emerged as a treatment for, and prevention of, symptomatic neuromas and has been reported to be of benefit in the hand. Anatomical studies establishing landmarks for consistent identification of the motor entry points (MEPs) to the intrinsic muscles have not been performed. The purpose of this study was to provide details regarding the MEPs to the intrinsic muscles, determine which MEPs are identifiable dorsally, and develop recommended sensory to MEP nerve coaptations for prophylactic TMR at the time of ray amputation or for management of symptomatic neuromas. Methods Motor entry points to the intrinsic hand muscles were dissected in 5 fresh latex-injected cadavers. Number of MEPs, diameter, surface of entry, and distance from dorsal (Lister tubercle) and volar (hamate hook) landmarks were recorded for each target muscle. The digital sensory nerve diameters were measured for size comparison. Results Motor entry points were identified to all 19 intrinsic muscles through a volar approach and 12 through a dorsal approach. For all fingers, at least 2 MEPs were consistently identified dorsally at the base of each amputation site innervating expendable muscles. Motor entry points to the thenar muscles were only reliably identified through a volar approach. Two recommended nerve coaptations for each digit amputation were identified. All had a favorable sensory-to-MEP diameter ratio less than 2:1. Conclusions The intrinsic hand muscles have MEPs at consistent distances from bony landmarks both dorsally and volarly. Clinical relevance These results can be applied clinically to assist surgeons in identifying the locations of MEPs to the intrinsic muscles when performing TMR in the hand for both neuroma treatment and prevention.

Objective To explore the diagnostic accuracy of the split-hand index (SHI) for amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) using sonographic assessment of muscle thickness. Methods We performed a prospective sonographic assessment of hand muscle thickness in 59 controls, 87 patients with ALS, and 33 patients with SMA. We determined the diagnostic accuracy of SHI for differentiating patients with ALS and SMA from controls. Results Patients with ALS and SMA had significantly lower muscle thickness and SHI values compared with controls. SHI showed excellent diagnostic accuracy for differentiating ALS from controls, and good diagnostic accuracy for differentiating SMA from controls. Conclusions SHI determined by sonographic measurement of hand muscle thickness seems to be a promising tool for the diagnosis of ALS and may be added easily when performing neuromuscular ultrasound. Significance SHI determined by sonographic measurement of hand muscle thickness can differentiate between healthy subjects and patients with ALS and SMA.

Background Reward-based feedback given during motor learning has been shown to improve the retention of the behaviour being acquired. Interestingly, applying transcranial direct current stimulation (tDCS) during learning over the primary motor cortex (M1), an area associated with motor retention, also results in enhanced retention of the newly formed motor memories. However, it remains unknown whether combining these distinct interventions result in an additive benefit of motor retention. Methods We investigated whether combining both interventions while participants learned to account for a visuomotor transformation results in enhanced motor retention (total n = 56; each group n = 14). To determine whether these interventions share common physiological mechanisms underpinning learning, we assessed motor cortical excitability and inhibition (i.e. SICI) on a hand muscle before and after all participants learned the visuomotor rotation using their entire arm and hand. Results We found that both the Reward-Stim (i.e. reward + tDCS) and Reward-Sham (i.e. reward-only) groups had increased retention at the beginning of the retention phase, indicating an immediate effect of reward on behaviour. However, each intervention on their own did not enhance retention when compared to sham, but rather, only the combination of both reward and tDCS demonstrated prolonged retention. We also found that only the Reward-Stim group had a significant reduction in SICI after exposure to the perturbation. Conclusions We show that combining both interventions are additive in providing stronger retention of motor adaptation. These results indicate that the reliability and validity of using tDCS within a clinical context may depend on the type of feedback individuals receive when learning a new motor pattern., Highlights • Concurrently administering reward and M1 tDCS during learning results in enhanced motor retention. • The combination of these interventions also leads to a reduction in M1 inhibitory mechanisms. • No benefits of motor retention were found when reward or M1 tDCS were given alone.

Objective There is still insufficient knowledge about natural history in adult spinal muscular atrophy, thus valid markers for treatment and disease monitoring are urgently needed. Methods We studied hand muscle innervation pattern of 38 adult genetically confirmed 5q spinal muscular atrophy (SMA) patients by the motor unit number index (MUNIX) method. Data were compared to healthy controls and amyotrophic lateral sclerosis (ALS) patients and systematically correlated to typical disease-relevant scores and other clinical as well as demographic characteristics. Results Denervation of hand muscles in adult SMA was not evenly distributed. By calculation of the MUNIX ratios, we identified a specific hand muscle wasting pattern for SMA which is different to the split hand in ALS. Furthermore, MUNIX parameters strongly correlated with established disease course parameters independent of disease stages. Conclusion We found a pathophysiological remarkable denervation pattern of hand muscles, a ‘reversed split hand’. MUNIX of single hand muscles correlated well with disease severity and thus represents an easily available biomarker for adult SMA. Significance Our data show the power of the MUNIX method as a biomarker for upcoming questions in adult SMA.

Intrinsic hand muscles are densely located in the hand, and the myoelectric observation from the surface is sometimes unreliable because of some outside influences that may interfere with the signals. In the present study, we evaluated the activities of multiple interosseous hand-muscles which densely located in the hand, through analyzing the surface electromyographic signals during finger-oriented tasks using univariate and multivariate logistic regression models. Ten healthy subjects participated in our experiment, and isometrically exercised each finger one by one in flexed form. The result of a univariate analysis with the power and amplitude domain predictor variables of the surface electromyographic signals showed significant consistency between the activated finger and the inserted finger of the dorsal interosseous muscles to the proximal phalanx (P < 0.001). Meanwhile, the results of a multivariate analysis showed a higher correlation of the regression model of the fourth dorsal interosseous muscle during the action of the ring finger using frequency-domain variables (the Nagelkerke R2 = 0.716 when the median frequency was used), compared to the model without the frequency-domain variables (the Nagelkerke R2 = 0.583). Our result showed that the logistic regression models have a particular possibility for the analysis of the surface electromyographic signals of densely located hand-muscle activities related to the finger-oriented tasks.

In this study, we investigated the electrophysiologic recovery of the abductor pollicis brevis (APB) muscle after contralateral seventh cervical (cC7) nerve transfer for the treatment of global brachial plexus avulsion (GBPA). We retrospectively analyzed the electromyography records of 95 patients with GBPA, comprising 81 men and 14 women, focusing on the motor unit potential (MUP) recovery of the APB. All patients underwent cC7-median nerve (MN) transfer. The cC7 nerve was transferred to the MN alone in 58 patients (One-Nerve Group), whereas 37 patients underwent cC7 transfer to the MN and another nerve (Two-Nerve Group). Fifty-three patients (MUP Group) exhibited MUP recovery of the APB, whereas 42 patients did not (No-MUP Group). The MUP Group comprised 32 patients from the One-Nerve Group and 21 patients from the Two-Nerve Group. The mean age of the MUP Group was significantly lower than that of the No-MUP Group. In summary, electrophysiologic recovery of the APB was common in patients with GBPA after cC7-MN transfer, indicating that it may be possible to restore the function of the intrinsic muscles of the hand after GBPA. The rehabilitation strategy for patients with GBPA, which overlooks the restoration of intrinsic hand muscle function, may require amendment.

The object of this study was to clarify how the motor imagery of foot muscle relaxation influences corticospinal excitability for the ipsilateral hand. Twelve participants volitionally relaxed their right foot from a dorsiflexed position (actual relaxation), or imaged the same movement (imagery relaxation) in response to an auditory cue. Transcranial magnetic stimulation (TMS) was delivered to the hand area of the left primary motor cortex at different time intervals after an auditory cue. Motor evoked potentials (MEPs) were recorded from the right extensor carpi radialis (ECR) and flexor carpi radialis (FCR). MEP amplitudes of ECR and FCR caused by single-pulse TMS temporarily decreased during both actual relaxation and imagery relaxation as compared with those of the resting control. A correlation of MEP amplitude between actual relaxation and imagery relaxation was observed. Our findings indicate that motor imagery of muscle relaxation of the foot induced a reduction of corticospinal excitability in the ipsilateral hand muscles. This effect is likely produced via the same mechanism that functions during actual muscle relaxation.

This study was to apply the newly developed electrical impedance myography (EIM) technique to examine hand muscles in patients with an incomplete cervical spinal cord injury (SCI).EIM was performed on the thenar, hypothenar, and first dorsal interosseous (FDI) muscles of SCI (n=16) and age-matched healthy control (n=18) subjects. By sending low intensity and high frequency current through the skin and measuring the consequent voltage, EIM estimates the major impedance parameters, which include resistance (R), reactance (X) and phase angle (θ).The SCI group had lower reactance and phase angle (p0.0001) as compared to the control group in all three muscles, and lower resistance in the thenar muscle (p0.05). The SCI group also demonstrated a smaller anisotropy in resistance (p0.0001) and larger anisotropy in phase angle (p0.05) compared to those from healthy controls.The reduced reactance and phase angle of paralyzed muscles could be due tochanges of membrane integrity and fat infiltration, whereas the change in the anisotropy may reflect the rearrangement of muscle fiber geometry.The EIM provides a quick and convenient tool for examination of muscle alterations after SCI.

Until the early 5th century BC, Phaleron Bay was the main port of ancient Athens (Greece). On its shore, archaeologists have discovered one of the largest known cemeteries in ancient Greece, including a range of burial forms, simple pits, cremations, larnaces (clay tubs), and series of burials of male individuals who appear to have died violent deaths, referred to here as “atypical burials”. Reconstructing the osteobiographies of these individuals will help create a deeper understanding of the socio-political conditions preceding the rise of Classical Athens. Here, we assess the habitual manual behavior of the people of Archaic Phaleron (ca. 7th – 6th cent. BC), relying on a new and precise three-dimensional method for reconstructing physical activity based on hand muscle attachment sites. This approach has been recently validated on laboratory animal samples as well as on recent human skeletons with a detailed level of long-term occupational documentation (i.e., the mid-19th century Basel Spitalfriedhof sample). Our Phaleron sample consists of 48 adequately preserved hand skeletons, of which 14 correspond to atypical burials. Our results identified consistent differences in habitual manual behaviors between atypical burials and the rest. The former present a distinctive power-grasping tendency in most skeletons, which was significantly less represented in the latter (p-values of

The aim of this study is to determine the effect of form factors (curvature rate, depth) of mobile devices on hand comfort when using large-screen curved mobile devices. To that end, four muscles (APB, APL, FDI, EDC) were selected and mockups for experiment were developed with four curvature rate levels (flat/100/200/300R) and five depth levels (3/5/7/9/11 mm). User experiment was conducted using three interactions (tapping, dragging, and texting) that usually take place on smartphones. EMG signal of each participant was measured. Combination of curvature and depth could maximize the physical comfort of hands and fingers through the experiment so that the interaction effect between form factors and tasks could be identified. Our results revealed that only APL and FDI had statistically significant muscle activity amounts across the curvature rates. With respect to effect of depth, all four muscles showed statistically significant difference in muscle activity. Moreover, results from the interaction effect among task levels of two tasks (target location of tapping and direction of dragging) and two form factors showed no interaction effect in either tapping or texting. The results of this study could be used to determine the optimal range for form factors of curved screen mobile devices in terms of physical comfort of the hand while using large-screen devices.

Objective C8-dominant innervation of ulnar-innervated and T1-dominant innervation of median-innervated intrinsic hand muscles have been suggested, although less is known regarding forearm muscles. We aimed to determine myotomal innervation of the forearm muscles based on the clinical and electromyographial findings of patients with C8 or T1 lesions. Methods Medical Research Council scale and EMG findings were retrospectively reviewed in 16 patients with C8 lesions (2 postmedian sternotomy C8 plexopathy and 14 C8 radiculopathy) and 9 patients with T1-dominant lesions (8 true neurogenic thoracic outlet syndrome and 1 T1 radiculopathy). Results Clinical and EMG findings revealed T1-dominant innervation of the flexor digitorum superficialis, flexor digitorum profundus of the index finger, abductor pollicis brevis, and flexor pollicis longus muscles, and C8-dominant innervation of the flexor carpi ulnaris, flexor digitorum profundus of the little finger, and digit extensors innervated by the posterior interosseous nerve. The first dorsal interosseous, and abductor digiti minimi muscles seem to be innervated by both C8 and T1 roots. Conclusions C8-dominant innervation of ulnar-innervated muscles and T1-dominant innervation of median-innervated muscles are also evident for forearm flexor muscles. Significance Such an additional evidence for myotomal innervation will improve localization in clinical as well as electrophysiological diagnoses.

The human hand is a complex structure that performs various functions for activities of daily living and occupations. This paper presents a literature review on the methodologies used to evaluate hand functions from a biomechanics standpoint, including anthropometry, kinematics, kinetics, and electromyography (EMG). Anthropometry describes the dimensions and measurements of the hand. Kinematics includes hand movements and the range of motion of finger joints. Kinetics includes hand models for tendon and joint force analysis. EMG is used on hand muscles associated with hand functions and with signal-processing technology.

Elders mostly suffer from degeneration, which causes problems of their daily lives. Aging has become a big issue of scientific researches nowadays. Elders mostly live alone or alone with their spouse. Since they prefer cooking themselves to eating out, cooking still plays an important role of their lives. Associated with high temperature, cooking behaviours are known to be high-risk tasks in our houses. Heavy kitchenware may also enhance the risk of suffering from carpal tunnel syndromes. With the lost of muscle mass and the cognitive degeneration, it will be far more dangerous for elders work in the kitchen. Morphological functional innovation is a method combined with functional innovation and morphological chart. The process of this method is to analyse functions of current products, and then re-compose these functions by morphological chart after adding expected new functions. Solutions were filtered by the method Analysis of Interconnected Decision Areas (AIDA), and use Analytic Hierarchy Process (AHP) to chose the final solution. For the result, a glove, wristband and elbow band composes this wearing aid system. In this wearing aid system, we reformed the glove by adding ribbons, so as to imitate the muscle structure of our palm and forearm in an easy way. Our idea is to make a wearing system that has the same function with our hand muscles. Similar to the “exoskeleton” concept, our design is pretty much like an “exomuscle” system. In this research, we have also evaluated our wearing aid system. We determine the difference before and after wearing our system by collecting and analysing the EMG data. Experiments have shown that our exomuscle system does have some effects. The results show that the difference before and after wearing the exomuscle system is significant, and mutual effect happened. We have collected data from biceps, flexor digitorum superficialis (FDS) and flexor carpi radialis (FCR), and after wearing the aid system, the loading of FDS and Biceps reduces while the loading of FCR increases. The loading decrease of FDS tells us that the aid certainly helps grip power, and the loading increase of FCR reveals that it may cause more ulnar deviation.

Background Effects of age on the assessment of intracortical inhibition with paired-pulse transcranial magnetic stimulation (TMS) have been variable, which may be due to between-study differences in test TMS intensity and test motor evoked potential (MEP) amplitude. Objective To investigate age-related differences in short- (SICI) and long-interval intracortical inhibition (LICI) across a range of test TMS intensities and test MEP amplitudes. Methods In 22 young and 18 older subjects, SICI and LICI were recorded at a range of test TMS intensities (110%–150% of motor threshold) while the first dorsal interosseous (FDI) muscle was at rest, or producing a precision grip of the index finger and thumb. Data were subsequently compared according to the amplitude of the MEP produced by the test alone TMS. Results When pooled across all test TMS intensities, SICI in resting muscle and LICI in active muscle were similar in young and older adults, whereas SICI in active muscle and LICI in resting muscle were reduced in older adults. Regrouping data based on test MEP amplitude demonstrated similar effects of age for SICI and LICI in resting muscle, whereas more subtle differences between age groups were revealed for SICI and LICI in active muscle. Conclusions Advancing age influences GABA-mediated intracortical inhibition, but the outcome is dependent on the experimental conditions. Age-related differences in SICI and LICI were influenced by test TMS intensity and test MEP amplitude, suggesting that these are important considerations when assessing intracortical inhibition in older adults, particularly in an active muscle.

Introduction Transcranial magnetic stimulation (TMS) can be used to map the corticomotor representations of hand muscles in the precentral gyrus. The spatial peak of the corticomotor representations is often not located in the primary motor hand area (M1HAND), but shows an anterior shift towards the caudal part of dorsal premotor cortex (PMd). Here we used magnetic resonance imaging (MRI) to test the hypothesis that the “hand knob” of the precentral gyrus shows different structural properties in individuals with a clear “premotor” representation compared to individuals with a preponderant “primary-motor” representation of hand muscles. Methods Twenty-four volunteers (mean age: 24.3 ± 0.9 SE, 12 women) underwent whole-brain structural MRI and sulcus-shape based TMS mapping of the right precentral gyrus. High-resolution T1-weighted MRIs were used for neuronavigation of TMS and to calculate regional cortical thickness of the precentral gyrus. We also performed quantitative multiparameter mapping of the longitudinal relaxation rate (R1 = 1/T1) as an index of cortical myelination and simulated the electric field strength induced by TMS at motor threshold (—E—) in the hand-knob region (SimNIBS software). Sulcus-shape based TMS mapping was used to obtain mediolateral and posterior-anterior corticomotor excitability profiles of the left abductor digiti minimi and first dorsal interosseus muscles. Results In 14 out of 24 individuals (58%), TMS mapping disclosed a clear spatial peak in the PMd (referred to as “PMd” subjects”), whereas the remaining 10 subjects (42%) showed maximal motor responses more posteriorly in M1HAND (referred to as M1HAND subjects). Motor threshold was not different between the two groups (p = 0.265). Compared “PMd” subjects, “M1” subjects displayed a higher electric field strength in the very rostral part of the M1HAND in the transition zone from the wall to the crown of the precentral gyrus (p = 0.01). In addition, “PMd” subjects showed an overall increase of regional myelination in the precentral gyrus relative to the “M1” subjects (mixed model ANOVA: F(1,18) = 5.362, p = 0.033). No difference between two groups was evident for curvature and cortical thickness. Conclusion Differences in location of the “motor hot spot” are associated with differences in microstructure in the precentral gyrus and the magnitude of the induced electrical field. The results support the notion of two distinct functional and microstructural phenotypes of corticomotor hand representations in human precentral gyrus. They also underscore the usefulness of electrical field modelling to account for inter-individual differences in the biophysiological effects of TMS in the human brain.

Dynamic characteristics of a manual task can affect the control of hand muscles due to the difference in biomechanical/physiological characteristics of the muscles and sensory afferents in the hand. We aimed to examine the effects of task dynamics on the coordination of hand muscles, and on the motor adaptation to external assistance. Twenty-four healthy subjects performed one of the two types of a finger extension task, isometric dorsal fingertip force production (static) or isokinetic finger extension (dynamic). Subjects performed the tasks voluntarily without assistance, or with a biomimetic exotendon providing targeted assistance to their extrinsic muscles. In unassisted conditions, significant between-task differences were found in the coordination of the extrinsic and intrinsic hand muscles, while the extrinsic muscle activities were similar between the tasks. Under assistance, while the muscle coordination remained relatively unaffected during the dynamic task, significant changes in the coordination between the extrinsic and intrinsic muscles were observed during the static task. Intermuscular coherence values generally decreased during the static task under assistance, but increased during the dynamic task (all p-values 0.01). Additionally, a significant change in the task dynamics was induced by assistance only during static task. Our study showed that task type significantly affect coordination between the extrinsic and intrinsic hand muscles. During the static task, a lack of sensory information from musculotendons and joint receptors (more sensitive to changes in length/force) is postulated to have resulted in a neural decoupling between muscles and a consequent isolated modulation of the intrinsic muscle activity.

Summary Motivating stimuli provoke action tendencies that sometimes lead to unwanted behavior (e.g., eating chocolate when trying to diet) [1–4]. Implementing control over these provocations is essential to healthy functioning [1, 5]; however, few laboratory-based models of such control exist. Here we developed a novel task in which thirsty human subjects made instrumental responses to obtain a juice reward (Go trials) or were required to withhold responding (NoGo trials) in the presence of a rewarded (CS+) or unrewarded (CS−) conditioned stimulus. For Go trials, single-pulse transcranial magnetic stimulation revealed a rapid increase in motor activity for CS+ versus CS−, preceding more vigorous instrumental responding. Critically, successful NoGo trials resulted in suppression of motor activity for CS+, but not CS−. Moreover, while there was broad excitation in the hand muscles in Go trials, suppression in NoGo trials was selective to the effector that could obtain reward. These results show that response suppression can be triggered by a motivational stimulus, thus providing a richer model of self-control than classic cognitive psychology paradigms.

The aim of the present study was to assess whether peripheral mechanisms, mediated through axonal dysfunction, may contribute to development of the split-hand in amyotrophic lateral sclerosis (ALS).Median and ulnar nerve motor axonal excitability studies were undertaken on 21 ALS patients with motor responses recorded over the abductor pollicis brevis (APB), abductor digit minimi (ADM) and first dorsal interosseous (FDI) muscles, and results compared to 24 controls.The split-hand index (SI), an objective biomarker of preferential atrophy of APB and FDI muscles, was significantly reduced in ALS (SI(ALS) 7.8 ± 1.7, SICONTROLS 13.1 ± 1.1, P0.0001). Axonal excitability studies identified significant prolongation of strength-duration time constant in ALS patients when recording over the APB (P0.05) and ADM axons (P0.05) but not FDI axons (P=0.22). Greater changes in depolarising threshold electrotonus were also evident across the range of intrinsic hand muscles and were accompanied by increases of superexcitability in APB (P0.01) and FDI (P0.05) axons.The present study reinforces the significance of the split-hand phenomenon in ALS and argues against a significant peripheral contribution in the underlying development.Axonal dysfunction may appear as a downstream process that develops secondary to the intrinsic pathophysiological origins of ALS.

The purpose of this study was to investigate the extent to which correlated neural inputs, quantified as EMG-EMG coherence across intrinsic and extrinsic hand muscles, varied as a function of wrist angle during a constant force precision grip task. Eight adults (5 males; mean age 29 years) participated in the experiment. Subjects held an object using a two-digit precision grip at a constant force at a flexed, neutral, and extended wrist posture, while the EMG activity from intrinsic and extrinsic hand muscles was recorded through intramuscular fine-wire electrodes. The integral of z-transformed coherence computed across muscles pairs was greatest in the flexed wrist posture and significantly greater than EMG-EMG coherence measured in the neutral and extended wrist posture (P < 0.01 and 0.05, respectively). Furthermore, EMG-EMG coherence did not differ statistically between the extrinsic and intrinsic muscle pairs, even though it tended to be greater for the extrinsic muscle pair (P ≥ 0.063). These findings lend support to the notion of a functional role of correlated neural inputs to hand muscles for the task-dependent coordination of hand muscle activity that is likely mediated by somatosensory feedback.

Muscle fatigue is known to be associated with a deteriorated muscle coordination and impaired movement performance in variety of voluntary movements. The aim of this study was to investigate the generally underexplored effect of muscle fatigue on both the coordination between grip force (GF; the force component perpendicular to the hand–object contact area that provides friction) and load force (LF; the parallel force component that can move the object or support the body) as well as movement performance in manipulation tasks. Fifteen participants performed a variety of static and dynamic manipulations both with and without a preceding procedure designed to fatigue the arm and hand muscles. The tasks involved exertion of ramp-and-hold and oscillation patterns of LF against an externally fixed instrumented device, and a simple lift of a freely moving device. The results revealed a fatigue-associated decrease in GF scaling (i.e., the magnitude of GF relative to LF) and GF–LF coupling (correlation between GF and LF), while the task performance regarding the accuracy of exertion of the prescribed LF profiles remained unaffected. We conclude that muscle fatigue both partly decouples GF from LF and reduces the overall GF magnitude, which could potentially explain why hand-held objects are more likely to drop when manipulated with fatigued muscles. However, the unaffected task performance could be explained either by the relatively low level of muscle forces required by the tested tasks, the moderate level of the fatigue imposed, or both.

Background When using transcranial magnetic stimulation, a stimulation intensity defined as a certain level above the threshold for activation of a hand muscle is commonly used, disregarding the fact that the areas of activation for different muscles may have varying response characteristics intra- and interindividually. Objective To study the response characteristics of different muscles and compare them within and between individuals. Also to investigate the effect of varying stimulation intensity (defined in two different ways) and amplitude criterion for response, on the sizes of the activation areas for different muscles. Methods A system of transcranial magnetic stimulation with navigation capacity where the stimulation intensity can be defined in terms of the electric field strength in the tissue was used. Four different muscles were investigated in healthy adults. The threshold for activation at rest (RMT) of the different muscles and their respective areas of activation were quantified using three different stimulus intensities (100, 110 and 120% RMT) and two criteria for response amplitude (20 and 50 μV). Results Responses could readily be determined using 20 μV as response limit. The RMTs for different muscles varied within and between individuals. The degree to which the area depended on stimulation intensity differed between muscles intra- and interindividually. All results were statistically significant (P Conclusions The response characteristics vary between muscles within an individual and between individuals for a certain muscle. Thus, for optimal accuracy when delineating the activation area, the investigation should be adapted to each particular muscle.

Much of our knowledge on the physiological mechanisms of transcranial magnetic stimulation (TMS) stems from studies which targeted the human motor cortex. Very surprisingly, however, it is still unclear which part of M1 is stimulated by TMS when a muscle twitch is elicited. Considering that the motor cortex consists of functionally and histologically distinct subareas, this also renders the hypotheses on the physiological TMS effects uncertain. I will report on two recent studies which combined electrophysiological measurements of muscle responses to TMS with realistic estimates of the induced electric field, based on the finite-element method (FEM) and MRI-derived individual head models. In the first study, the orientation of a standard figure 8 coil was systematically varied and the field changes in different subparts of the motor cortex were compared with the electrophysiological threshold changes. In the second study, three figure 8 coils having different field decays were used and the differences in the electrophysiological thresholds were correlated with the differences in the calculated field distributions. Both studies consistently demonstrate that TMS stimulates the region around the gyral crown and that the maximal electric field strength in this region is significantly related to the electrophysiological response. Our studies are one of the most extensive comparisons between FEM-based field calculations and physiological TMS effects so far, being based on data for two hand muscles in 9 subjects. The results help to improve our understanding of the basic mechanisms of TMS. They also pave the way for a systematic exploration of realistic field estimates for dosage control in TMS.

Objective To investigate inter-individual variation in the efficiency of magnetic brainstem stimulation (BST) with regard to the stimulation site. Methods We studied 31 healthy subjects, using a right hand muscle as a recording site. Three stimulation sites were compared: BST over the inion (inion BST), and BST over the midpoint between the inion and the right (ipsilateral BST) or left (contralateral BST) mastoid process. Five suprathreshold BSTs were performed for each stimulation site using the same stimulation intensity. The mean peak-to-peak amplitudes of motor evoked potential (MEP) were compared. The active motor threshold (AMT) and onset latency for inion BST and ipsilateral BST were also measured and compared. Results Contralateral BST did not evoke discernible MEPs in most subjects. In 21 subjects (67.7%), ipsilateral BST elicited larger MEPs than inion BST did, and AMT for ipsilateral BST was lower than or equal to the AMT for inion BST in all subjects. Ipsilateral BST elicited shorter latency in such subjects. Conclusions The suitable stimulation site for BST differed among subjects. About two-thirds showed larger MEP to ipsilateral BST. Significance These findings might help us to find an efficient stimulation site for BST in each subject.

Purpose There is a need for objective measures of pediatric intrinsic hand muscle strength as the current standard, the manual muscle test, lacks sensitivity to clinically important changes in muscle strength. We report the development, reliability, and normative values of the Peg Restrained Intrinsic Muscle Evaluator (PRIME), a device that quantifies intrinsic hand muscle strength. Methods Typically developing children, ages 4 to 16 years (n = 119), established normative values of intrinsic strength for thumb palmar abduction, thumb opposition, and index and small finger abduction. A subset of 30 children (15 boys, 15 girls), ages 7 to 16 years, determined inter-rater and intra-rater reliability. We calculated mean, standard deviation, intraclass correlation coefficients, and smallest detectable differences. Results Normative results indicate that gender and age were significant predictors of strength. Although the dominant hand generated higher strength measurements on average, differences were not statistically significant. Mean index and small finger abduction strength was significantly lower than thumb abduction and opposition in both genders. Intraclass correlation coefficients ranged from 0.85 to 0.94 for inter-rater reliability and 0.88 to 0.98 for intra-rater reliability. Bland-Altman plots showed an even distribution across the zero line. Conclusions The PRIME device is a reliable tool for the quantification of intrinsic hand muscle strength in children. Age-specific and gender-specific normative values in typically developing children can serve as a future resource for clinicians treating pediatric hand or neuromuscular conditions. Type of study/level of evidence Diagnostic II.

TMS can be used to map the corticomotor representations of hand muscles (HMs) in the precentral gyrus (PG), whose spatial peak is often not located in the primary motor hand area (M1HAND) but shifts towards the caudal part of dorsal premotor cortex (PMd). We used magnetic resonance imaging (MRI) to test the hypothesis that “hand-knob” of PG shows different structural properties in individuals with a “premotor” representation compared to individuals with a “primary-motor” representation of HMs. Twenty-four volunteers underwent MRI and sulcus-shape-based TMS-mapping of right PG. T1-weighted-MRIs were used for neuronavigation and to calculate cortical-thickness of the PG. We also performed quantitative multiparameter mapping of the longitudinal relaxation rate as an index of cortical myelination and simulated the electric field strength induced by TMS in the hand-knob-region. In 14 out-of 24 individuals (58%), TMS mapping disclosed a spatial peak in the PMd (“PMd-subjects”), whereas the remaining 10 subjects (42%) showed maximal motor response in M1HAND (“M1HAND-subjects”). “M1-subjects” displayed a higher electric field strength in the rostral part of the M1HAND (p = 0.01). “PMd-subjects” showed an increase of regional-myelination in the PG (p = 0.033). The results support the notion of two distinct functional-microstructural phenotypes of corticomotor hand representations in human PG.

Regaining the function of an impaired limb is highly desirable in individuals experiencing paralysis. One possible avenue to achieve this goal is through rewiring of preserved neural structures to bridge the interrupted pathway using a brain-computer interface. Here we demonstrated that monkeys with subcortical stroke were able to learn to use an artificial cortico-muscular connection (ACMC), brain-controlled functional electrical stimulation to the hand muscles, to regain volitional control of a paralyzed hand. In a targeted manner, the ACMC induced reorganization of cortical activities among an extensive cortical area; the modulating high-gamma activity became concentrated around an arbitrarily selected cortical site controlling stimulation to the muscles. This reorganization could be reset and rapidly reorganized to a new cortical site. Thus, the ACMC imparted a new function for muscle control to a connected cortical site and triggered cortical reorganization in order to restore impaired motor function after stroke.

Introduction The aim of this study is to compare repeater F-wave parameters with CMAP amplitudes recorded from the hand muscles (as indicators of the amount of lower motor neuron [LMN] loss) and with the triple stimulation technique (TST) ratios in the same muscles (as indicators of upper motor neuron [UMN] involvement) in 19 patients with amyotrophic lateral sclerosis (ALS). Methods Ninety F-waves were recorded from thenar and hypothenar muscles by supramaximal stimuli applied to the relevant nerves at the wrist level. Repeater F-waves (Frep) were visually defined as those presented with the same amplitude, latency and shapes. Repeater neuron (RN) index, Frep index, persistances of F-waves, F/M amplitude ratio and the neurophysiologic index (NI) were calculated. By depending our laboratory normals, TST ratio values lower than 82% and 86% were accepted as abnormal showing UMN involvement in thenar and hypothenar muscles respectively. Results TST ratios were abnormal in 13 thenar and 11 hypothenar muscles. None of the Frep parameters showed any significant relationship with the abnormal TST ratios, except the lower Frep index in thenar muscles, in patients with UMN involvement according to low TST ratios. However, there was a strong negative correlation with the CMAP amplitudes and Frep index and RN index values in hypothenar muscle (Spearman’s rho, p Conclusion These findings imply that repeater F waves might be a manifestation of LMN loss more than being a result of UMN involvement.

The Cymanus is a novel flex sensor glove for measuring hand kinematics in primates. It was used to monitor 9 joints of a rhesus macaque performing a grasping task with 25 objects. Over 6 days, the monkey tolerated the glove and showed no significant impairment in performance. The sensors linearly tracked joint angles, with joint trajectories preserved over days. Angular positions discriminated objects as accurately as electromyograms recorded simultaneously from 24 arm and hand muscles, and were maximally informative of object identity at the end of reach-to-grasp. In a further final validation of the glove, muscle activity controlling a joint was correlated with the joint’s angular acceleration 70 ms later.

Charcot Marie Tooth (CMT) disease was first described in 1886. It describes a spectrum of genetic disorders that affects peripheral nerves, either by slowing action potential transmission along the axons, or by reducing the amplitude, or both. It is this variety of underlying genetic findings and subtleties of clinical presentation that has resulted in the varying nomenclature over the years. Patients with CMT commonly present to orthopaedic surgeons with lower and upper limb symptoms including ankle sprains, cavus feet and weakness of the intrinsic hand muscles. More rarely, they present with spinal and hip manifestations. It is not usually a life threatening or painful condition and therefore lends itself to the FRCS (Tr & Orth) exam.

This study investigates the stationarity of steady state mechanomyogram signals for the purpose of determining appropriate features for signal classification. Mechanomyography is the superficial recording of low frequency vibrations detected over contracting muscles. Steady state mechanomyogram signals, recorded at the belly of the extensor digitorum, flexor digitorum superficialis and flexor pollicis longus muscles during functional grasps were tested for weak stationarity. Twenty percent of the contractions were found to be non-stationary, indicating that time frequency methods may be appropriate for automatic pattern recognition of functional grasp from the mechanomyogram. The distribution of the stationary test statistic was dependent on the type of muscle contractions, suggesting that the test statistic itself might be a discriminating feature for mechanomyogram pattern recognition in applications such as multifunction prosthetic control. Since the major known source of non-stationarity was decreasing variance, it is suggested that shifts in the distribution of the test statistic may indicate the time course of relative muscle contributions to functional grasp.

Background Optimising stimulus parameters is important in maximising the efficacy of repetitive transcranial magnetic stimulation (rTMS) in treatment applications. RTMS over motor cortex has been reported as more effective in producing corticospinal inhibition when a monophasic rather than a biphasic stimulus waveform is used. However, non-optimal coil orientation and high intensities of monophasic rTMS may have influenced previous results. Methods In eight healthy subjects, we measured motor evoked potentials (MEPs) in a hand muscle after monophasic and biphasic rTMS (1 Hz for 15 min) over the motor cortex with the coil always in the optimal orientation. MEPs were evoked by both monophasic and biphasic stimuli. Results MEPs were initially significantly reduced after monophasic but not biphasic rTMS. However, a late reduction was seen after biphasic rTMS. Limitations These motor cortical findings may not be directly applicable to prefrontal rTMS. Conclusions This study confirms that low frequency rTMS with monophasic pulses produces more corticospinal inhibition than with biphasic pulses, even when the direction of current and intensity are as well-matched as possible.

Rehabilitation can induce cortical reorganization in chronic stroke patients. In this study we investigated the mechanisms underlying treatment-associated plasticity. Eight patients with a stroke >6 months earlier participated in a 4-week period of physiotherapy based on a forced use concept. Before and after treatment, focal transcranial magnetic stimulation over the affected hemisphere was used to assess the motor output map of the paretic first dorsal interosseous muscle. Using a paired pulse paradigm, intracortical inhibition was investigated at the center of the cortical output map (CoG) and one cm anterior, posterior, lateral and medial of that position. Motor function was evaluated with the Motor Activity Log and the Wolf Motor Function Test. After therapy, the cortical representation size of the affected hand muscle was increased. In each patient, the CoG moved in the direction where intracortical inhibition had been lowest prior to therapy. Significant correlations were found between motor function tests and changes of output map size and CoG shifts, respectively. We conclude that treatment-associated cortical reorganization is influenced by the distribution of inhibitory properties within the representation area prior to therapy, since the CoG moved in the direction of lowest inhibition. The correlations between motor functions and electrophysiological results indicate a functional relevance of the observed reorganization pattern.

In comparison with people in other occupations, dentists and dental hygienists are at increased risk of developing work-related musculoskeletal disorders, including carpal tunnel syndrome. An important risk factor in dental practice is forceful pinching, which occurs during dental scaling. Ergonomically designed dental instruments may help reduce the prevalence of MSDs among dental practitioners.In the authors' study, 24 dentists and dental hygienists used 10 custom-designed dental scaling instruments with different handle diameters and weights to perform a simulated scaling task. The authors recorded the muscle activity of two extensors and two flexors in the forearm with electromyography, while thumb pinch force was measured by pressure sensors.Handle designs of periodontal instruments had significant (P.05) effects on hand muscle load and pinch force during a manual scaling task. The instrument with a large diameter (10 millimeters) and a light weight (15 grams) required the least amount of muscle load and pinch force. There was a limit to the effect of handle diameter, with diameters larger than 10 mm having no additional benefit; however, the study did not identify a limit to the effect of reducing the weight of the instrument, and therefore instruments lighter than 15 g may require even less pinch force.The results from this study can guide dentists and dental hygienists in selection of dental scaling instruments.

The objectives of this intervention research project were to develop and evaluate engineering controls for the reduction of the upper extremity injury risk in workers in the furniture manufacturing industry. The analysis of OSHA Form 200 logs and surveys of furniture workers revealed that upholsterers, workers who use random orbital sanders and workers who use spray guns are at higher levels of risk of illness than the rest of the working population. An on-site ergonomic analysis of these three jobs was performed and the following risk factors were identified for each of these three work groups: upholsterers—repetitive, high-force pinch grips; sanders—long-duration static grip forces; and sprayers—awkward postures (ulnar wrist deviations and wrist flexion). Engineering interventions in the form of new or modified handtools were then evaluated in the laboratory to assess their effectiveness in reducing exposure to these risk factors. For sanding, an interface was created that secured the hand to the sander with the intention of reducing the need for static grip forces during sanding. A new handtool was created for upholsterers that replaced the repetitive pinch grips with a power grip. Finally, a commercially available spray gun with ergonomic features was evaluated. Each of these modified tools/methods was compared with the standard methods typically used in industry. The results show that most of the intended beneficial effects were realized. The random orbital sander interface reduced extensor muscle activities by an average of 30%. The upholstery handtool reduced the intrinsic hand muscle activities by an average of 51%. The effects of the adapted spray gun were most prominent when working on horizontal surfaces and showed an average reduction of 40° of wrist flexion and 14° of ulnar deviation as compared to the standard pistol grip spray gun in this activity. Relevance to industry The ergonomic intervention research described in this report documents a reduction in exposure to risk factors for upper extremity cumulative trauma disorders for three work activities in the furniture manufacturing industry.

We used transcranial magnetic stimulation (TMS) to investigate ipsilateral motor-evoked potentials (MEPs) in patients with congenital mirror movements together with adult stroke patients with acquired mirror movements on the unaffected hand. In patients with congenital mirror movements, there was an anomaly of corticospinal projections such as large inter-muscle differences in the ratio of the ipsilateral to contralateral corticospinal projections. An electrophysiological finding in stroke patients with acquired mirror movements was ipsilateral MEPs in the unaffected hand muscles after TMS to the damaged hemisphere. This could be explained by the presence of a small cerebral lesion with sparing of the uncrossed corticospinal projections from the damaged motor cortex.

Objectives Repeater F-waves (Freps) were seen in patients with amyotrophic lateral sclerosis (ALS). The factors implicated for the presence and frequency of Freps were loss of the motor neurons and the changes in their excitability. The aim of this study was to assess the Freps in ALS patients and to compare their frequencies in thenar and hypothenar muscles. Methods Sixteen ALS patients and 11 healthy controls were recruited to the study. All patients had ⩾2 mV CMAPs recorded from the hand muscles. Ninety F-waves were recorded from abductor digiti minimi (ADM) and abductor pollicis brevis (APB). The index of repeater neurons (RN) and Freps were calculated. Results Mean index RN and index Freps values of ADM and APB muscles in ALS group (17.1 and 42.6 for ADM and 16.3 and 41.9 for APB) were significantly higher than those of healthy controls (4.7 and 13.9 for APB and 1.5 and 3.6 for ADM). ALS group had a lower persistence of F-waves for both muscles than healthy controls (56.4 and 94.6 for APB and 83.4 and 97.0 for ADM). Freps parameters were not different between thenar and hypothenar muscles, whereas persistence of F-waves was lower in the thenar (56.4%) as compared to the hypothenar (83.4%) muscles. Discussion Similar Freps parameters in the thenar and hypothenar muscles might be caused by the inclusion criteria. Lower F-persistence in the thenar muscles was in accordance with the split-hand phenomenon. Conclusion The assessment of Freps and F persistence may be useful in understanding of the electrophysiological changes in ALS.

In the acute phase after stroke, active finger extension is a strong predictor of long-term dexterity. Transcranial magnetic stimulation (TMS) with surface electromyography of proximal arm and intrinsic hand muscles has proven to be of additional prognostic value to clinical assessment, especially in patients unable to follow instructions. The current study aimed to determine whether TMS of the extensor digitorum communis (EDC) further improves the prognostic accuracy. Motor evoked potentials (MEPs) of the EDC at rest and Fugl-Meyer Assessment (FMA) of the upper extremity were measured in 18 participants within 4 weeks after stroke, and included as independent variables in a multiple linear regression analysis with the FMA at 26 weeks after stroke as dependent variable. The data demonstrated that the EDC resting MEPs had no additional value over clinical predictors, but a large MEP amplitude increased the likelihood of a high FMA score at 26 weeks. An absent EDC resting MEP did not preclude return of dexterity.

Topographic distribution of motoneurons innervating hand muscles through the median (Mn), ulnar (Ul), or radial (Rd) nerves was examined using a retrograde multiple-labeling technique in the macaque monkey. The Mn and Ul motoneurons, i.e. flexor motoneurons, were distributed from C6 to T2 and from C7 to T2 segments of the spinal cord, respectively, while the Rd motoneurons, i.e. extensor motoneurons, were distributed from C4 to T2. The present study further revealed partial intermingling of the cell bodies and partial overlap of the dendritic fields among the motoneurons projecting through different nerves, indicating that subregions of motoneuronal pool participate in coordination between the flexor and extensor, or among the flexor muscles. It was suggested that there exists a control mechanism for precise hand movements in the spinal cord.

TOS represents a spectrum of disorders encompassing four related syndromes: arterial compression, venous compression, neurogenic compression, and a poorly defined pain syndrome. Patients can present with signs of arterial insufficiency, venous obstruction, painless wasting of intrinsic hand muscles, and pain. History and physical examination are the most important diagnostic studies, and radiographs of the chest and cervical spine and electromyography/nerve conduction studies are useful to identify other causes of pain and disability. Surgical intervention is indicated for patients failing nonoperative maneuvers and can usually yield satisfactory results. TOS may also be the most underrated, overlooked, and misdiagnosed, and the most important and difficult to manage peripheral nerve compression in the upper extremity.

The aim of this investigation was to establish the clinical and electromyographic pattern of tremor in patients with depression. Twenty-eight patients with depression and tremor and 30 patients with tremor and generalized anxiety disorder were investigated. Tremor was scored clinically by the Webster Tremor Scale. Electromyographic examination of tremor activity from antagonistic hand muscles was performed. Our results revealed in both groups of patients a postural and kinetic tremor with characteristics of an enhanced physiological tremor. Tremor involved only both upper limbs and no other body parts in all patients. In conclusion tremor in depression and generalized anxiety disorder is an enhanced physiological tremor.

The aim was to test the accuracy of muscle volume measurements with a new 3-dimensional (3-D) ultrasound system, which allows a freehand scanning of the transducer with an improved quality of the ultrasound images and therefore the outlines of the muscles. Five resected cadaveric hand muscles were insonated and the muscle volumes calculated by 3-D reconstructions of the acquired 2-D ultrasound sections. Intra-reader, inter-reader and follow-up variability were calculated, as well as the volume of the muscle tissue measured by water displacement. In the results, 3-D ultrasound and water displacement measurements showed an average deviation of 10.1%; Data of 3-D ultrasound measurements were: intra-reader variability 2.8%; inter-reader variability 2.4% and follow-up variability 2.3%. 3-D measurements of muscle volume are valid and reliable. Serial sonographic measurements of muscle may be able to quantitate changes in muscle volume that occur in disease and recovery.

We analysed motor-evoked potentials (MEPs) from the hand muscles during focal transcranial magnetic stimulation (TCS) in both the affected (AH) and the unaffected (UH) hemispheres of 17 monohemispheric stroke patients followed-up in subacute stage. Recording sessions were performed at 2 (T1 session) and 4 (T2 session) months from acute stroke. Clinical and functional scores were evaluated. An age-sex matched group of 20 healthy subjects have been referenced. In T1, relaxed MEPs from AH were smaller than UH (p

This study has compared the topography of the corticomotor representation of an instrinsic hand muscle in the relaxed state and during a low-level voluntary contraction using transcranial magnetic stimulation. It was found that the optimum cortical stimulus site and the surrounding area of excitable cortex were shifted ∼ 6 mm medially as a result of performing a voluntary contraction. This difference may be due to a combination of factors involving the spatial distribution of excitable intracortical fibres, the effects of muscle afferent activity on motor cortex excitability, and task-dependent modifications of corticomotor output.

Objective To evaluate the relation between prehension strength, dexterity and axonal loss in a same cohort of CMT1A patients with valid tools. CMT1A is the most common form of hereditary neuropathy. The upper limb impairment creates a weakness of intrinsic hand muscles, an opposition, prehension strength and axonal loss. Materials/patients and methods Patients were recruited from November 2012 to November 2014 by Physicals Rehabilitation Medicine and Neurologicals consultations of Clermont Ferrand's University Hospital. Measures of strength were evaluated in kilograms (kg) by Jamar and Pince Gauge dynamometers, and dexterity by Sollerman and Nine Hole Peg and Jebsen's tests. Results Thirty-one patients were included. A moderated correlation was find between pinch strength in kg by Pince Gauge, and dexterity by Sollerman ( r = 0.52). No correlation was found between axonal loss evaluated by motor action potential of median nerve, handgrip strength, pince strength or dexterity tests. Discussion/Conclusion This results mention the complexity of prehension, the balance out by the patients CMT1A of their intrinsic hand muscles weakness, and the interest to detect prematurely this impairment in order to limit the deformities and abnormal postures.

Objective We aimed to characterize changes in motor cortex function in Asperger’s syndrome (AS) with MRI-navigated TMS and related abnormalities in fine motor skills. Methods Eight boys with AS (aged 8–11 years) and eight neurotypical controls were studied. Resting motor threshold and motor-evoked potentials were determined for abductor pollicis brevis (APB) muscle. Functional motor areas for six hand muscles (APB, ADM, FDI, FCR, ECR and BB) were mapped at 110% of rMT. Center of gravities of representations and the sizes of representation areas were determined. Both hemispheres were studied. Manual dexterity was assessed by Box and Block Test. Results AS boys had larger arm/hand ratio in left hemisphere ( p = 0.010) and larger left/right ratio for arm ( p = 0.014) than controls. Other TMS-related measures were similar between the groups. AS boys also had poorer manual dexterity than controls ( p = 0.005). Arm/hand representation ratio in the left hemisphere (Spearman’s correlation coefficient − 0.528, p = 0.036) and left/right arm representation ratio (−0.760, p = 0.001) correlated negatively with manual dexterity. Conclusions Sizes of upper arm representation areas are altered in AS and they correlate with fine motor skills. Key message Changes in motor cortex function may partly explain abnormalities and impairments in fine motor skills among children with AS.

To determine whether long and short time exposure of man in 0g alters normal physiological tremor patterns we recorded arm tremor using an accelerometer as well as hand forces and tremor during constant isometric contraction using a load cell. Arm tremor was decreased during both flights in amplitude and frequency. Shortly after the long term flight arm tremor amplitude was increased, indicating adaptive changes in the tonic reflex loop. Isometric hand tremor remained unchanged during the long and short time flight demonstrating that the contractile properties of hand muscles remained constant. Precision of hand force was decreased until the half duration of the long term flight.