Direct comparison of median and ulnar repetitive nerve stimulation in generalized myasthenia gravis.

INTRODUCTION/AIMS: Ulnar nerve repetitive nerve stimulation (RNS) has been traditionally used in the electrophysiological evaluation of myasthenia gravis (MG). However, its low diagnostic sensitivity remains a limitation. Existing data may suggest that median nerve RNS outperforms that of the ulnar nerve, but a direct comparison is currently lacking. The aim of this study was to directly compare the diagnostic yields between median and ulnar nerve RNS in patients with generalized MG. METHODS: We performed a retrospective analysis of patients with MG who underwent median and ulnar nerve RNS at a single tertiary center. RESULTS: RNS studies of median nerve recording from the abductor pollicis brevis and ulnar nerve recording from the adductor digiti minimi were completed in 28 patients with generalized MG. Abnormal RNS was more frequently observed in the median compared with the ulnar nerve (60.7% vs 35.7%, P = .046). The average magnitude of decrement was higher in the median nerve compared with the ulnar nerve (17.3% vs 9.6%, P = .017). Differences between the median and ulnar nerve RNS studies were restricted to patients with mild manifestations (Myasthenia Gravis Foundation of America class II). DISCUSSION: Median nerve RNS has superior diagnostic sensitivity as compared with ulnar nerve RNS in the assessment of mild generalized MG.

Effects of a Single Myofascial Induction Session on Neural Mechanosensitivity in Breast Cancer Survivors: A Secondary Analysis of a Crossover Study.

OBJECTIVES: The purpose of this study was to investigate the short-term effects of myofascial induction on mechanosensitivity of upper limb nerves. METHODS: In this secondary analysis of a randomized, single-blind, placebo-controlled crossover study, 21 breast cancer survivors with stage I-IIIA cancer were randomly allocated to an experimental group (30 minutes of myofascial induction session) or placebo control group (unplugged pulsed 30 minutes of shortwave therapy), with a 4-week washout period between sessions that occurred in a physical therapy laboratory in the Health Science Faculty (University of Granada, Spain). Range of motion (universal goniometry), structural differentiation, symptoms (yes/no), and pressure pain thresholds (electronic algometry) were assessed during neurodynamic tests and attitude toward massage scale as covariate. RESULTS: An analysis of covariance revealed significant time × group interactions for range of motion in affected upper limb nerves (median, P < .001; radial, P = .036; ulnar, P = .002), but not for nonaffected upper limb nerves (median, P = .083; radial, P = .072; ulnar, P = .796). A χ2 or Fisher exact test, as appropriate, also revealed a significant difference (P = .044) in sensitivity for the affected upper limb ulnar nerve in the experimental group, whereas the rest of the assessed nerves (affected and nonaffected upper limb nerves) showed no significant changes in either the experimental or control groups (P > .05). An analysis of covariance revealed no significant interactions on pressure pain thresholds over the nerves for affected (all P > .05) and nonaffected (all P > .05) upper limb nerves. CONCLUSION: A single myofascial induction session may partially improve mechanosensitivity of median, radial, and ulnar nerves and yield positive effects on symptom mechanosensitivity, especially regarding the ulnar nerve in breast cancer survivors.

Object Shape and Surface Topology Recognition Using Tactile Feedback Evoked through Transcutaneous Nerve Stimulation.

Tactile feedback is critical for distinguishing different object properties. In this article, we determined if tactile feedback evoked by transcutaneous nerve stimulation can be used to detect objects of different shape and surface topology. To evoke tactile sensation at different fingers, a 2x8 electrode grid was placed along the subject's upper arm, and two concurrent electrical stimulation trains targeted the median and ulnar nerve bundles, which evoked individually modulated sensations at different fingers. Fingertip forces of the prosthetic hand were transformed to stimulation current amplitude. Object shape was encoded based on finger-object contact timing. Surface topology represented by ridge height and spacing was encoded through current amplitude and stimulation time interval, respectively. The elicited sensation allowed subjects to determine object shape with success rates >84%. Surface topology recognition resulted in success rates >81%. Our findings suggest that tactile feedback evoked from transcutaneous nerve stimulation allows the recognition of object shape and surface topology. The ability to recognize these properties may help improve object manipulation and promote fine control of a prosthetic hand.

Postsurgical Electrical Stimulation Enhances Recovery Following Surgery for Severe Cubital Tunnel Syndrome: A Double-Blind Randomized Controlled Trial.

BACKGROUND: Patients with severe cubital tunnel syndrome often have poor functional recovery with conventional surgical treatment. Postsurgical electrical stimulation (PES) has been shown to enhance axonal regeneration in animal and human studies. OBJECTIVE: To determine if PES following surgery for severe cubital tunnel syndrome would result in better outcomes compared to surgery alone. METHODS: Patients with severe cubital tunnel syndrome in this randomized, double-blind, placebo-controlled trial were randomized in a 1:2 ratio to the control or stimulation groups. Control patients received cubital tunnel surgery and sham stimulation, whereas patients in the stimulation group received 1-h of 20 Hz PES following surgery. Patients were assessed by a blinded evaluator annually for 3 yr. The primary outcome was motor unit number estimation (MUNE) and secondary outcomes were grip and key pinch strength and McGowan grade and compound muscle action potential. RESULTS: A total of 31 patients were enrolled: 11 received surgery alone and 20 received surgery and PES. Three years following surgery, MUNE was significantly higher in the PES group (176 ± 23, mean + SE) compared to controls (88 ± 11, P < .05). The mean gain in key pinch strength in the PES group was almost 3 times greater than in the controls (P < .05). Similarly, other functional and physiological outcomes showed significantly greater improvements in the PES group. CONCLUSION: PES enhanced muscle reinnervation and functional recovery following surgery for severe cubital tunnel syndrome. It may be a clinically useful adjunct to surgery for severe ulnar neuropathy, in which functional recovery with conventional treatment is often suboptimal.

Object stiffness recognition using haptic feedback delivered through transcutaneous proximal nerve stimulation.

OBJECTIVE: Haptic feedback is crucial when we manipulate objects. Information pertaining to an object's stiffness in particular can help facilitate fine motor control. In this study, we seek to determine whether objects of different stiffness levels can be recognized using haptic feedback provided by transcutaneous electrical stimulation of peripheral nerves. APPROACH: Using a stimulation electrode grid placed along the medial side of the upper arm, the median and ulnar nerve bundles were targeted to evoke haptic sensation on the palmar side of the hand. Stimulation current amplitude was modulated in real-time with the fingertip force recorded from a sensorized prosthetic hand. In order to evaluate which stimulation pattern was more critical, object stiffness was encoded either by the rate of change of the stimulus amplitude or the level of peak stimulus amplitude, as the prosthesis grasped the objects. MAIN RESULTS: Both encoding methods allowed the subjects to differentiate objects of different stiffness levels with >90% accuracy. No significant difference was observed between the two encoding methods, which indicated that both the rate of change of the stimulation amplitude and the peak stimulation amplitude could effectively provide stiffness information of the objects. SIGNIFICANCE: The outcomes suggest that it is possible to elicit haptic sensations describing various object stiffness levels using transcutaneous nerve stimulation. The haptic feedback associated with object stiffness can facilitate object manipulation/interactions. It may also improve user experience during human-machine interactions, when object stiffness information is incorporated.

Multichannel Nerve Stimulation for Diverse Activation of Finger Flexors.

OBJECTIVE: Neuromuscular electrical stimulation (NMES) is a common approach to restore muscle strength of individuals with a neurological injury but restoring hand dexterity is still a challenge. This study sought to quantify the diversity of finger movements elicited by a multichannel nerve stimulation technique. METHODS: A 2 × 8 stimulation grid, placed on the upper arm along the ulnar and median nerves, was used to activate different finger flexors by automatically switching between randomized bipolar electrodes. The forces from each individual finger as well as the high-density electromyogram (HDEMG) of the intrinsic and extrinsic flexors were recorded. The elicited finger forces were categorized using hierarchical clustering, and the 2D correlation of the spatial patterns of muscle activation was also calculated. RESULTS: A wide range of movement patterns were identified, including multi-finger and single-digit movements. Additionally, a number of electrode pairs elicited similar finger movements. The muscle activation patterns showed similar and distinct spatial patterns, signifying activation redundancy. CONCLUSION: These results revealed the diversity of elicitable finger movements and muscle activations. The system redundancy can be explored to compensate for system instability due to fatigue or electrode shift. The outcomes can also enable the development of an automatic calibration of the stimulation.

Study on variation trend of repetitive nerve stimulation waveform in amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease involving both upper and lower motor neurons with no effective cure. Electrophysiological studies have found decremental responses during low-frequency repetitive nerve stimulation (RNS) except for diffused neurogenic activities. However, the difference between ALS and generalized myasthenia gravis (GMG) in terms of waveform features is unclear. In the current study, we explored the variation trend of the amplitudes curve between ALS and GMG with low-frequency, positive RNS, and the possible mechanism is discussed preliminarily. METHODS: A total of 85 ALS patients and 41 GMG patients were recruited. All patients were from Peking Union Medical College Hospital (PUMCH) between July 1, 2012 and February 28, 2015. RNS study included ulnar nerve, accessory nerve and facial nerve at 3 Hz and 5 Hz stimulation. The percentage reduction in the amplitude of the fourth or fifth wave from the first wave was calculated and compared with the normal values of our hospital. A 15% decrease in amplitude is defined as a decrease in amplitude. RESULTS: The decremental response at low-frequency RNS showed the abnormal rate of RNS decline was 54.1% (46/85) in the ALS group, and the results of different nerves were 54.1% (46/85) of the accessory nerve, 8.2% (7/85) of the ulnar nerve and 0% (0/85) of the facial nerve stimulation, respectively. In the GMG group, the abnormal rate of RNS decline was 100% (41/41) at low-frequency RNS of accessory nerves. However, there was a significant difference between the 2 groups in the amplitude after the sixth wave. CONCLUSIONS: Both groups of patients are able to show a decreasing amplitude of low-frequency stimulation RNS, but the recovery trend after the sixth wave has significant variation. It implies the different pathogenesis of NMJ dysfunction of these 2 diseases.

Reduced muscle fatigue using kilohertz-frequency subthreshold stimulation of the proximal nerve.

OBJECTIVE: Conventional electrical stimulation techniques targeting the motor points often induce early muscle fatigue onset that can limit clinical applications. In our current study, we evaluated the muscle activation and force generation during fatigue using a novel stimulation technique. APPROACH: Clustered subthreshold 80 µs current pulses at 10 kHz (high-frequency mode, HF) were delivered transcutaneously to activate the median and ulnar nerve bundles and induce dispersed activations of motor units. Conventional stimulation technique with 800 µs pulses at 30 Hz (low-frequency mode, LF) served as a control condition. Fatigue was evoked by delivering the stimuli continuously for 5 min, with matched initial contraction force (approximately 30% of maximal voluntary contraction) between the HF and LF modes. The elicited finger flexion forces and the muscle activation patterns quantified by high-density electromyogram (EMG) from the finger flexor muscles were compared. MAIN RESULTS: Our results revealed that the elicited force was prolonged under the HF stimulation mode, manifested as a slower decay of the force, a smaller absolute force decline, a higher force plateau, and a larger force-time integral, in comparison with the LF mode. The force-to-EMG ratio under the HF stimulation was also consistently higher than that under the LF mode. In addition, the EMG spatial distribution showed that the muscle activation tended to be more spread-out under the HF mode compared with the LF mode. These results indicated that the HF stimulation induced a higher efficiency of muscle activation, which can potentially reduce muscle fatigue. SIGNIFICANCE: Our findings revealed that the subthreshold kilohertz nerve stimulation can induce temporally and spatially dispersed activation of different motor units with more efficient activation patterns. The reduced muscle fatigue can have a prominent advantage in neural rehabilitation involving transcutaneous electrical nerve stimulations.

Improved muscle activation using proximal nerve stimulation with subthreshold current pulses at kilohertz-frequency.

OBJECTIVE: Transcutaneous electrical nerve stimulation can help individuals with neurological disorders to regain their motor function by activating muscles externally. However, conventional stimulation technique often induces near-simultaneous recruitment of muscle fibers, leading to twitch forces time-locked to the stimulation. APPROACH: To induce less synchronized activation of finger flexor muscles, we delivered clustered narrower pulses to the proximal segment of the median and ulnar nerves at a carrier frequency of either 10 kHz (with an 80 µs pulse width) or 7.14 kHz (with a 120 µs pulse width) (high-frequency mode, HF), and different clustered pulses were delivered at a frequency of 30 or 40 Hz. Conventional stimulation with pulse frequency of 30 or 40 Hz (low-frequency mode, LF) was used for comparison. With matched elicited muscle forces between the HF and LF modes, the force variation, the high-density electromyogram (EMG) signals recorded at the finger flexor muscles and stimulation-induced-pain levels were compared. MAIN RESULTS: The compound action potentials in the 10 kHz HF mode revealed a significant difference (i.e. a lower amplitude and area, and a wider duration) compared with the LF mode, indicating cancellations of asynchronized action potentials. A smaller fluctuation in the elicited forces in the 10 kHz mode further demonstrated the less synchronized activation of different motor units. These effects tended to be weaker in the 7.14 kHz HF condition. However, the levels of pain sensation was not reduced in the HF mode potentially due to the high charge density used in the HF mode. Our findings indicated that different nerve fibers were recruited asynchronously through summations of different numbers of subthreshold depolarizations in the HF mode. SIGNIFICANCE: Compared with the LF mode, the HF mode stimulation was capable of activating the nerve fibers in a less synchronized way, which is more similar to the physiological activation pattern.

Ulnar Nerve Conduction Block Using Surface Kilohertz Frequency Alternating Current: A Feasibility Study.

The aim of this study was to test the effects of kilohertz frequency alternating current (KHFAC) surface stimulation applied to the ulnar nerve on force and myoelectrical activity of the abductor digiti minimi (ADM) muscle. Eighteen healthy volunteers (age: 27.6 ± 7.9 years; 10 males, 8 females) were included in the study. Each subject participated in one session during which a biphasic 7 kHz rectangular pulse was delivered above the medial epicondyle of the humerus to induce ulnar nerve blocking. ADM electromyographic (EMG) activity and contraction force were measured before (Pre), immediately after, and following 5 and 10 min post stimulation (post 1, post 2). The results showed that EMG activity decreased immediately after stimulation compared to prestimulation, it returned to the level of prestimulation at 5 min (post 1), and decreased again at 10 min (post 2). Furthermore, analysis of compound adjusted z-score indicated significant decrease of force and myoelectrical activity immediately, and 10 min post stimulation. The findings, which demonstrate that KHFAC surface stimulation of the ulnar nerve may decrease the motor activity of intrinsic hand muscle, can help to develop future methods of neuromodulation to treat hand spasticity.

The effect of high-tone external muscle stimulation on symptoms and electrophysiological parameters of uremic peripheral neuropathy.

OBJECTIVE AND DESIGN: Peripheral neuropathy is a devastating uremic complication that causes debilitating pain and movement limitation. The aim of the study was to assess the influence of high-tone external muscle stimulation (HTEMS) therapy on clinical and electrophysiologycal parameters in hemodialysis patients with uremic peripheral neuropathy. PATIENTS AND INTERVENTIONS: The study group consisted of 28 chronic hemodialysis patients (mean age 71.6 ± 8.6 y, median 74 y) on maintenance dialysis for 3 - 187 months (median 31 months). Eight persons (28.9%) were diabetics. All of them exhibited overt peripheral neuropathy and had undergone pharmacological therapy without improvement. All subjects were treated with HTEMS for 1 h during a hemodialysis session, 3 times weekly for 12 weeks. The dialysis parameters (duration of the session, blood and dialysate flow) were constant during the treatment period. Electrophysiological evaluation before and after intervention included assessment of sensory nerves (ulnar nerve, sural nerve) and motor nerves (ulnar nerve, peroneal nerve). The examined nerve conduction parameters were conduction velocity, amplitude, distal latency and F-wave latency. RESULTS: In the questionnaire 18 persons (64%) reported improvement of general well-being after HTEMS therapy, 17 persons (61%) felt an increase of physical capacity, and 16 persons (57%) experienced a decreased feeling of cold feet. The electrophysiological findings were obtained in 19 patients who completed the examination before and after the course of HTEMS. A significant improvement was noted in the motor conduction velocity of the ulnar nerve; respective values were 48.53 ± 6.14 vs. 51.50 ± 5.51 m/s, p = 0.03. CONCLUSION: The study demonstrated for the first time that the subjective amelioration of uremic peripheral neuropathy by HTEMS treatment is associated with significant improvement in an objective electrophysiological parameter, motor conduction velocity of the ulnar nerve.

Effect of somatosensory stimulation of two and three nerves on upper limb function in healthy individuals.

BACKGROUND AND PURPOSE: Improvement in motor function has been reported in healthy subjects following somatosensory stimulation (SS) of individual upper limb peripheral nerves. This effect could have beneficial applications in rehabilitation, but there is little knowledge of the effects of stimulating multiple upper limb nerves. This study evaluated the effects of SS of two and three nerves on hand function. METHODS: A single blind within-group repeated measures design was utilized. Ten healthy subjects (27.1 ± 5.4 years [mean ± SD], three men) were recruited and, after a familiarization session, were given SS to the ipsilateral hand in a randomized order to two (ulnar and median) and three (ulnar, median and radial) nerves on two occasions separated by at least one week. The time required to complete the Jebsen-Taylor Hand Function Test (JTHFT) and handgrip strength of the ipsilateral hand were measured before and immediately after each SS session. RESULTS: Total JTHFT time decreased significantly by an average of 3.58 ± 2.75 s (9.9%; P = 0.003) and 4.10 ± 3.20 s (11.6%; P = 0.003) following SS to two and three nerves, respectively, but no difference between the two was found. Handgrip strength decreased significantly by 1.82 ± 1.91 kgf (P = 0.015) following SS to three nerves only. CONCLUSIONS: This study suggests that SS of three nerves may facilitate motor training but may also induce a reduction in muscle performance. Further studies are needed to determine the clinical implications of these findings for neurological rehabilitation.

Frequency-dependent tuning of the human motor system induced by transcranial oscillatory potentials.

Different corticothalamic brain modules intrinsically oscillate at a "natural frequency" in a topographically organized manner. In "quiescent" human sensorimotor regions, the main detectable oscillatory activity peaks at ∼20 Hz, and partly contributes to determine the state of corticospinal excitability. Here, we showed that the transcranial application of an imperceptible, short-lasting (90 s) electric field oscillating at a physiological range increases corticospinal excitability online, with well defined frequency dependence and regional specificity. Indeed, the size of motor evoked potentials (MEPs) induced by navigated single-pulse TMS over the motor cortex significantly increased only during the local application of transcranial alternating current stimulation (tACS) at 20 Hz (ß range). Other tACS frequencies (5, 10, and 40 Hz) applied on the motor cortex did not impact MEPs' size. Moreover, tACS applied on a control site (parietal cortex) and on a peripheral site (ulnar nerve) also failed to modulate MEPs. These results help clarifying the functional significance of the 20 Hz idling ß rhythm of sensorimotor regions and suggest potential clinical applications of this approach.

Peripheral nerve stimulation in intractable neuropathic pain.

Peripheral nerve stimulation (PNS) is a neurostimulation analgesic technique. PNS is utilized to treat peripheral neuropathic pain. It is highly sophisticated and a specialized technique used where other forms of treatment have failed. This paper describes the PNS procedure, its therapeutic principles, indications, and the comprehensive care for patients after the PNS implant. First, we summarize our experience using this type of invasive treatment. In the second part, a case of intractable neuropathic pain following repeated surgery to the ulnar nerve is reported. Prior to PNS, the patient underwent multiple types of antineuralgic treatment with no significant result. Only after the PNS application, was a significant analgesic effect achieved.

Localization of cervical and cervicomedullary stimulation leads for pain treatment using median nerve somatosensory evoked potential collision testing.

OBJECT: Spinal cord stimulation (SCS) is being currently used to treat medically refractory pain syndromes involving the face, trunk, and extremities. Unlike thoracic SCS surgery, during which patients can be awakened from conscious sedation to confirm good lead placement, safe placement of paddle leads in the cervical spine has required general anesthesia. Using intraoperative neurophysiological monitoring, which is routinely performed during these cases at the authors' institution, the authors developed an electrophysiological technique to intraoperatively lateralize lead placement in the cervical epidural space. METHODS: Data from 44 patients undergoing median and tibial nerve somatosensory evoked potential (SSEP) monitoring during cervical laminectomy or hemilaminectomy for placement or replacement of dorsal column stimulators were retrospectively reviewed. Paddle leads were positioned laterally or just off midline and parallel to the axis of the cervical spinal cord to effectively treat what was most commonly a predominant unilateral pain syndrome. During SSEP recording, the spinal cord stimulator was activated at 1.0 V and increased in increments of 1.0 V to a maximum of 6.0 V. A unilateral reduction or abolishment of SSEP amplitude was regarded as an indicator of lateralized placement of the stimulator. A bilateral diminutive effect on SSEPs was interpreted as a midline or near midline lead placement. RESULTS: Epidural stimulation abolished or significantly reduced SSEP amplitudes in all patients undergoing placement for a unilateral pain syndrome. In 15 patients, electrodes were repositioned intraoperatively to achieve the most robust SSEP amplitude reduction or abolishment using the lowest epidural stimulation intensity. In all cases in which a significant unilateral reduction in SSEP was observed, the patient reported postoperative sensory alterations in target locations predicted by intraoperative SSEP changes. Placement of cervical spinal cord stimulators for bilateral pain syndromes often resulted in bilateral but asymmetrical SSEP changes. In no cases were significant SSEP changes, other than those induced using the device to directly stimulate the dorsal surface of the spinal cord, observed. No case of new postoperative neurological deficit was observed. CONCLUSIONS: Somatosensory evoked potentials can be used safely and successfully for predicting the lateralization of cervical spinal cord stimulator placement. Moreover, they can also intraoperatively alert the surgical team to inadvertent displacement of a lead during anchoring. Further studies are needed to determine whether apart from assisting with proper lateralization, SSEP collision testing may help to optimize electrode positioning and improve pain control outcomes.

Estimation and pharmacodynamic consequences of the minimum effective anesthetic volumes for median and ulnar nerve blocks: a randomized, double-blind, controlled comparison between ultrasound and nerve stimulation guidance.

BACKGROUND: Nerve stimulation and ultrasound guidance are the most popular techniques for peripheral nerve blocks. However, the minimum effective anesthetic volume (MEAV) in selected nerves for both techniques and the consequences of decreasing the local anesthetic volume on the pharmacodynamic characteristics of nerve block remain unstudied. We designed a randomized, double-blind controlled comparison between neurostimulation and ultrasound guidance to estimate the MEAV of 1.5% mepivacaine and pharmacodynamics in median and ulnar nerve blocks. METHODS: Patients scheduled for carpal tunnel release were randomized to ultrasound guidance (UG) or neurostimulation (NS) groups. A step-up/step-down study model (Dixon method) was used to determine the MEAV with nonprobability sequential dosing based on the outcome of the previous patient. The starting dose of 1.5% mepivacaine was 13 and 11 mL for median and ulnar nerves at the humeral canal. Block success/failure resulted in a decrease/increase of 2 mL. A blinded physician assessed sensory blockade at 2-minute intervals for 20 minutes. Block onset time and duration were noted. RESULTS: The MEAV50 (SD) of the median nerve was lower in the UG group 2 (0.1) mL (95% confidence interval [CI] = [1, 96] to [2, 04]) than in the NS group 4 (3.8) mL (95% CI = [2, 4] to [5, 6]) (P = 0.017). There was no difference for the ulnar nerve between UG group 2 (0.1) mL (95% CI = [1, 96] to [2, 04]) and NS group 2.4 (0.6) mL (95% CI = [2, 1] to [2, 7]). The duration of sensory blockade was significantly correlated to local anesthetic volume, but onset time was not modified. CONCLUSION: Ultrasound guidance selectively provided a 50% reduction in the MEAV of mepivacaine 1.5% for median nerve sensory blockade in comparison with neurostimulation. Decreasing the local anesthetic volume can decrease sensory block duration but not onset time.

Effects of combined peripheral nerve stimulation and brain polarization on performance of a motor sequence task after chronic stroke.

BACKGROUND AND PURPOSE: Recent work demonstrated that application of peripheral nerve and cortical stimulation independently can induce modest improvements in motor performance in patients with stroke. The purpose of this study was to test the hypothesis that combining peripheral nerve stimulation (PNS) to the paretic hand with anodal direct current stimulation (tDCS) to the ipsilesional primary motor cortex (M1) would facilitate beneficial effects of motor training more than each intervention alone or sham (tDCS(Sham) and PNS(Sham)). METHODS: Nine chronic stroke patients completed a blinded crossover designed study. In separate sessions, we investigated the effects of single applications of PNS+tDCS, PNS+tDCS(Sham), tDCS+PNS(Sham), and PNS(Sham)+tDCS(Sham) before motor training on the ability to perform finger motor sequences with the paretic hand. RESULTS: PNS+tDCS resulted in a 41.3% improvement in the number of correct key presses relative to PNS(Sham)+tDCS(Sham), 15.4% relative to PNS+tDCS(Sham), and 22.7% relative to tDCS+PNS(Sham). These performance differences were maintained 1 and 6 days after the end of the training. CONCLUSIONS: These results indicate that combining PNS with tDCS can facilitate the beneficial effects of training on motor performance beyond levels reached with each intervention alone, a finding of relevance for the neurorehabilitation of motor impairments after stroke.

Increased pinch strength in acute and subacute stroke patients after simultaneous median and ulnar sensory stimulation.

BACKGROUND: Peripheral nerve stimulation may induce cortical adaptations as it improves pinch strength in chronic stroke patients immediately after stimulation. OBJECTIVE: Test the effects of peripheral sensory stimulation on pinch strength in patients with acute and subacute stroke. METHODS: Stroke patients (N = 20) who had onset less than 6 months previously and could voluntarily pinch the thumb to the index finger participated in a randomized, single-blinded, controlled study. Ten patients received 2 hours of simultaneous electrical stimulation over the median and ulnar nerves at the wrist to the level of appreciating paresthesias (peripheral sensory stimulation group). Ten control patients received stimulation to the level of perception (sham-control group). Pinch strength of the thumb pad to tip and to lateral side of the index finger of the paretic hand and the Action Research Arm test were tested before and immediately after the stimulation. RESULTS: Lateral and tip pinch strength were significantly increased in both groups (P < .05). Mean +/- SD of increased lateral pinch strength of peripheral sensory stimulation and sham-control groups were 1.24 +/- 0.54 pounds and 0.20 +/- 0.28 pounds, respectively. Mean +/- SD of increased tip pinch strength of peripheral sensory stimulation and sham-control groups were 1.00 +/- 0.72 pounds and 0.37 +/- 0.36 pounds, respectively. Increase pinch strength of the peripheral sensory stimulation group was greater than the sham-control group, with significant difference (P < .05). The Action Research Arm test was not significantly changed after stimulation in both groups (P > .05). CONCLUSION: Peripheral sensory stimulation of the paretic hand may increase pinch strength of acute and subacute stroke patients immediately after stimulation.

Sensory integration in writer's cramp: comparison with controls and evaluation of botulinum toxin effect.

OBJECTIVE: Abnormal temporal and spatial sensory integration have been described in mixed groups of dystonic patients. We tested somatosensory integration and the effect of botulinum toxin (BoNT) in patients with writer's cramp (WC). METHODS: Median and ulnar SEPs were recorded in 29 WC patients and in 10 controls. We performed: individual and simultaneous stimulation of median and ulnar nerves (MU) and paired stimulation of median nerve at interstimulus-interval (ISI) of 40 and 100 ms. All the trials were repeated after blinded randomized treatment with placebo or BoNT-A. RESULTS: We found no differences between patients and controls in standard SEPs. Spatial (except for N9) and temporal suppression after ISI 40 were present in both groups for all the waves; after ISI 100, suppression was present only for N70. There were no differences between patients and controls. After BoNT-A treatment, no changes were observed. CONCLUSIONS: In contrast with previous findings in heterogeneous dystonic groups, and although some studies suggest impairment of spatial and temporal sensory discrimination in patients with focal dystonia, in our large cohort of patients with WC we found no evidence of abnormal somatosensory integration investigated by means of SEPs and no changes in somatosensory variables after BoNT-A treatment. SIGNIFICANCE: Our findings may suggest pathophysiological differences between focal and generalized dystonia, and may also point to an inferior sensitivity of SEPs in detecting abnormalities in sensory discrimination as compared to methods based on subjective discrimination.