Electrode location and clinical outcome in hippocampal electrical stimulation for mesial temporal lobe epilepsy.

PURPOSE: To study the clinical outcome in hippocampal deep brain stimulation (DBS) for the treatment of patients with refractory mesial temporal lobe epilepsy (MTLE) according to the electrode location. METHODS: Eight MTLE patients implanted in the hippocampus and stimulated with high-frequency DBS were included in this study. Five underwent invasive recordings with depth electrodes to localize ictal onset zone prior to chronic DBS. Position of the active contacts of the electrode was calculated on postoperative imaging. The distances to the ictal onset zone were measured as well as atlas-based hippocampus structures impacted by stimulation were identified. Both were correlated with seizure frequency reduction. RESULTS: The distances between active electrode location and estimated ictal onset zone were 11±4.3 or 9.1±2.3mm for patients with a >50% or <50% reduction in seizure frequency. In patients (N=6) showing a >50% seizure frequency reduction, 100% had the active contacts located <3mm from the subiculum (p<0.05). The 2 non-responders patients were stimulated on contacts located >3mm to the subiculum. CONCLUSION: Decrease of epileptogenic activity induced by hippocampal DBS in refractory MTLE: (1) seems not directly associated with the vicinity of active electrode to the ictal focus determined by invasive recordings; (2) might be obtained through the neuromodulation of the subiculum.

Direct electrical stimulation using a battery-operated device for induction and modulation of colonic contractions in pigs.

Direct electrical stimulation of the colon offers a promising approach for the induction of propulsive colonic contractions by using an implantable device. The objective of this study was to assess the feasibility to induce colonic contractions using a commercially available battery-operated stimulator (maximum pulse width of 1 ms and maximum amplitude of 10 V). Three pairs of pacing electrodes were inserted into the cecal seromuscular layer of anesthetized pigs. During a first set of in vivo experiments conducted on six animals, a pacing protocol leading to cecum contractions was determined: stimulation bursts with 1 ms pulse width, 10 V amplitude (7-15 mA), 120 Hz frequency, and 30-s burst duration, repeated every 2-5 min. In a second testing phase, an evaluation of the pacing protocol was performed in four animals (120 stimulation bursts in total). By using the battery-operated stimulator, contractions of the cecum and movement of contents could be induced in 92% of all stimulations. A cecal shortening of about 30% and an average intraluminal pressure increase of 10.0 +/- 6.0 mmHg were observed.

Epileptogenic zone, electrode location and clinical outcome in hippocampal electrical stimulation for mesial temporal lobe epilepsy : a correlation study

Objectif : Etudier les résultats cliniques du traitement de patients atteints pai- une épilepsie mésiale du lobe temporal (MTLE) réfractaire, par stimulation cérébrale profonde (DBS) de l'hippocampe, en fonction de l'emplacement de l'électrode. Méthodes : Huit patients atteints de MTLE implantés dans l'hippocampe et stimulés par DBS à haute fréquence ont été inclus dans cette étude. Cinq ont subi des enregistrements invasifs avec des électrodes profondes dans le but d'estimer la localisation du foyer ictal avant de procéder à une DBS chronique. La position des contacts actifs de l'électrode a été mesurée en utilisant une imagerie post-opératoire. Les distances par rapport au foyer ictal ont été calculées, et les structures hippocampiques influencées par la stimulation ont été identifiées au moyen d'un atlas neuro-anatomique. Ces deux paramètres ont été corrélés avec la réduction de la fréquence d'apparition des crises. Résultats : Les distances entre la localisation estimée des contacts actifs de l'électrode et le foyer ictal étaient respectivement 11.0 +/- 4.3 ou 9.1 +/- 2.3 mm pour les patients présentant une réduction de > 50% ou < 50% de la fréquence des crises. Chez les patients (N = 6) montrant une réduction de > 50% de la fréquence des crises, 100% avaient des contacts actifs situés à < 3 mm du subiculum (p < 0,05). Les 2 patients ne répondant pas au traitement étaient stimulés par des contacts situés à > 3mm du subiculum. Conclusion : La diminution de l'activité épileptogène induite par DBS sur l'hippocampe dans les cas de MTLE réfractaires : 1) ne semble pas directement liée à la proximité des contacts actifs de l'électrode au foyer ictal déterminé par les enregistrements invasifs ; 2) pourrait être obtenue par une neuro-modulation du subiculum.

Twitch potentia induced by two different modalities of neuromuscular electrical stimulation: implications for motor unit recruitment.

INTRODUCTION: We tested the hypothesis that twitch potentiation would be greater following conventional (CONV) neuromuscular electrical stimulation (50-µs pulse width and 25-Hz frequency) compared with wide-pulse high-frequency (WPHF) neuromuscular electrical stimulation (1-ms, 100-Hz) and voluntary (VOL) contractions, because of specificities in motor unit recruitment (random in CONV vs. random and orderly in WPHF vs. orderly in VOL). METHODS: A single twitch was evoked by means of tibial nerve stimulation before and 2 s after CONV, WPHF, and VOL conditioning contractions of the plantar flexors (intensity: 10% maximal voluntary contraction; duration: 10 s) in 13 young healthy subjects. RESULTS: Peak twitch increased (P<0.05) after CONV (+4.5±4.0%) and WPHF (+3.3±5.9%), with no difference between the 2 modalities, whereas no changes were observed after VOL (+0.8±2.6%). CONCLUSIONS: Our results demonstrate that presumed differences in motor unit recruitment between WPHF and CONV do not seem to influence twitch potentiation results.

A new paradigm of neuromuscular electrical stimulation for the quadriceps femoris muscle.

PURPOSE: Neuromuscular electrical stimulation (NMES) with large electrodes and multiple current pathways (m-NMES) has recently been proposed as a valid alternative to conventional NMES (c-NMES) for quadriceps muscle (re)training. The main aim of this study was to compare discomfort, evoked force and fatigue between m-NMES and c-NMES of the quadriceps femoris muscle in healthy subjects. METHODS: Ten healthy subjects completed two experimental sessions (c-NMES and m-NMES), that were randomly presented in a cross-over design. Maximal electrically evoked force at pain threshold, self-reported discomfort at different levels of evoked force, and fatigue-induced force declines during and following a series of 20 NMES contractions were compared between c-NMES and m-NMES. RESULTS: m-NMES resulted in greater evoked force (P < 0.05) and lower discomfort in comparison to c-NMES (P < 0.05-0.001), but fatigue time course and magnitude did not differ between the two conditions. CONCLUSIONS: The use of quadriceps m-NMES appears legitimate for (re)training purposes because it generated stronger contractions and was less discomfortable than c-NMES (due to multiple current pathways and/or lower current density with larger electrodes).

Brain energy consumption induced by electrical stimulation promotes systemic glucose uptake.

BACKGROUND: Controlled transcranial stimulation of the brain is part of clinical treatment strategies in neuropsychiatric diseases such as depression, stroke, or Parkinson's disease. Manipulating brain activity by transcranial stimulation, however, inevitably influences other control centers of various neuronal and neurohormonal feedback loops and therefore may concomitantly affect systemic metabolic regulation. Because hypothalamic adenosine triphosphate-sensitive potassium channels, which function as local energy sensors, are centrally involved in the regulation of glucose homeostasis, we tested whether transcranial direct current stimulation (tDCS) causes an excitation-induced transient neuronal energy depletion and thus influences systemic glucose homeostasis and related neuroendocrine mediators.METHODS: In a crossover design testing 15 healthy male volunteers, we increased neuronal excitation by anodal tDCS versus sham and examined cerebral energy consumption with (31)phosphorus magnetic resonance spectroscopy. Systemic glucose uptake was determined by euglycemic-hyperinsulinemic glucose clamp, and neurohormonal measurements comprised the parameters of the stress systems.RESULTS: We found that anodic tDCS-induced neuronal excitation causes an energetic depletion, as quantified by (31)phosphorus magnetic resonance spectroscopy. Moreover, tDCS-induced cerebral energy consumption promotes systemic glucose tolerance in a standardized euglycemic-hyperinsulinemic glucose clamp procedure and reduces neurohormonal stress axes activity.CONCLUSIONS: Our data demonstrate that transcranial brain stimulation not only evokes alterations in local neuronal processes but also clearly influences downstream metabolic systems regulated by the brain. The beneficial effects of tDCS on metabolic features may thus qualify brain stimulation as a promising nonpharmacologic therapy option for drug-induced or comorbid metabolic disturbances in various neuropsychiatric diseases.

Indications, perspectives et limites de la stimulation électrique épidurale en cas d'artériopathie périphérique ou coronarienne [Indications, limits and future of epidural spinal cord electrical stimulation for coronary and peripheral artery disease]

The electrical stimulation of the dorsal columns of the spinal cord exerts a dual analgesic and vasodilatory effect on ischemic tissues. It is increasingly considered a valuable method to treat severe and otherwise intractable coronary and peripheral artery disease. The quality of the results depends from both a strict selection of the patients by vascular specialists and the frequency and quality of the follow-up controls. However the indications, limits, mode of action and results of spinal cord stimulation are still poorly understood. This article, based on a personal experience of 164 implantations for peripheral and coronary artery disease, aims to draw attention to this technique and to provide information on recent and future developments.

Electrical stimulation induces propagated colonic contractions in an experimental model.

BACKGROUND: Direct colonic electrical stimulation may prove to be a treatment option for specific motility disorders such as chronic constipation. The aim of this study was to provoke colonic contractions using electrical stimulation delivered from a battery-operated device. METHODS: Electrodes were inserted into the caecal seromuscular layer of eight anaesthetized pigs. Contractions were induced by a neurostimulator (Medtronic 3625). Caecal motility was measured simultaneously by video image analysis, manometry and a technique assessing colonic transit. RESULTS: Caecal contractions were generated using 8-10 V amplitude, 1000 micros pulse width, 120 Hz frequency for 10-30 s, with an intensity of 7-15 mA. The maximal contraction strength was observed after 20-25 s. Electrical stimulation was followed by a relaxation phase of 1.5-2 min during which contractions propagated orally and aborally over at least 10 cm. Spontaneous and stimulated caecal motility values were significantly different for both intraluminal pressure (mean(s.d.) 332(124) and 463(187) mmHg respectively; P < 0.001, 42 experiments) and movement of contents (1.6(0.9) and 3.9(2.8) mm; P < 0.001, 40 experiments). CONCLUSION: Electrical stimulation modulated caecal motility, and provoked localized and propagated colonic contractions.

Assessment of quadriceps muscle inactivation with a new electrical stimulation paradigm.

INTRODUCTION: In this study we evaluated the validity of garment-based quadriceps stimulation (GQS) for assessment of muscle inactivation in comparison with femoral nerve stimulation (FNS). METHODS: Inactivation estimates (superimposed doublet torque), self-reported discomfort, and twitch and doublet contractile properties were compared between GQS and FNS in 15 healthy subjects. RESULTS: Superimposed doublet torque was significantly lower for GQS than for FNS at 20% and 40% maximum voluntary contraction (MVC) (P < 0.01), but not at 60%, 80%, and 100% MVC. Discomfort scores were systematically lower for GQS than for FNS (P < 0.05). Resting twitch and doublet peak torque were lower for GQS, and time to peak torque was shorter for GQS than for FNS (P < 0.01). CONCLUSIONS: GQS can be used with confidence for straightforward evaluation of quadriceps muscle inactivation, whereas its validity for assessment of contractile properties remains to be determined. Muscle Nerve 51: 117-124, 2015.

Spatial distribution of motor units recruited during electrical stimulation of the quadriceps muscle versus the femoral nerve.

INTRODUCTION: In this study we investigated differences in the spatial recruitment of motor units (MUs) in the quadriceps when electrical stimulation is applied over the quadriceps belly versus the femoral nerve. METHODS: M-waves and mechanical twitches were evoked using over-the-quadriceps and femoral nerve stimulation of gradually increasing intensity from 22 young, healthy subjects. Spatial recruitment was investigated using recruitment curves of M-waves recorded from the vastus medialis (VM) and vastus lateralis (VL) and of twitches recorded from the quadriceps. RESULTS: At maximal stimulation intensity (Imax), no differences were found between nerve and over-the-quadriceps stimulation. At submaximal intensities, VL M-wave amplitude was higher for over-the-quadriceps stimulation at 40% Imax, and peak twitch force was greater for nerve stimulation at 60% and 80% Imax. CONCLUSIONS: For the VM, MU spatial recruitment during nerve and over-the-quadriceps stimulation of increasing intensity occurred in a similar manner, whereas significant differences were observed for the VL. Muscle Nerve, 2013.

Extra Forces induced by wide-pulse, high-frequency electrical stimulation: Occurrence, magnitude, variability and underlying mechanisms.

OBJECTIVE: In contrast to conventional (CONV) neuromuscular electrical stimulation (NMES), the use of "wide-pulse, high-frequencies" (WPHF) can generate higher forces than expected by the direct activation of motor axons alone. We aimed at investigating the occurrence, magnitude, variability and underlying neuromuscular mechanisms of these "Extra Forces" (EF). METHODS: Electrically-evoked isometric plantar flexion force was recorded in 42 healthy subjects. Additionally, twitch potentiation, H-reflex and M-wave responses were assessed in 13 participants. CONV (25Hz, 0.05ms) and WPHF (100Hz, 1ms) NMES consisted of five stimulation trains (20s on-90s off). RESULTS: K-means clustering analysis disclosed a responder rate of almost 60%. Within this group of responders, force significantly increased from 4% to 16% of the maximal voluntary contraction force and H-reflexes were depressed after WPHF NMES. In contrast, non-responders showed neither EF nor H-reflex depression. Twitch potentiation and resting EMG data were similar between groups. Interestingly, a large inter- and intrasubject variability of EF was observed. CONCLUSION: The responder percentage was overestimated in previous studies. SIGNIFICANCE: This study proposes a novel methodological framework for unraveling the neurophysiological mechanisms involved in EF and provides further evidence for a central contribution to EF in responders.

Responders to Wide-Pulse, High-Frequency Neuromuscular Electrical Stimulation Show Reduced Metabolic Demand: A 31P-MRS Study in Humans.

Conventional (CONV) neuromuscular electrical stimulation (NMES) (i.e., short pulse duration, low frequencies) induces a higher energetic response as compared to voluntary contractions (VOL). In contrast, wide-pulse, high-frequency (WPHF) NMES might elicit-at least in some subjects (i.e., responders)-a different motor unit recruitment compared to CONV that resembles the physiological muscle activation pattern of VOL. We therefore hypothesized that for these responder subjects, the metabolic demand of WPHF would be lower than CONV and comparable to VOL. 18 healthy subjects performed isometric plantar flexions at 10% of their maximal voluntary contraction force for CONV (25 Hz, 0.05 ms), WPHF (100 Hz, 1 ms) and VOL protocols. For each protocol, force time integral (FTI) was quantified and subjects were classified as responders and non-responders to WPHF based on k-means clustering analysis. Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated. Phosphocreatine depletion (ΔPCr) was assessed using 31P magnetic resonance spectroscopy. Responders developed four times higher FTI's during WPHF (99 ± 37 ×103 N.s) than non-responders (26 ± 12 ×103 N.s). For both responders and non-responders, CONV was metabolically more demanding than VOL when ΔPCr was expressed relative to the FTI. Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s). Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders. WPHF could therefore be considered as the less demanding NMES modality-at least in this subgroup of subjects-by possibly exhibiting a muscle activation pattern similar to VOL contractions.

Electrical colonic stimulation reduces mean transit time in a porcine model.

Abstract Electrical stimulation is a new way to treat digestive disorders such as constipation. Colonic propulsive activity can be triggered by battery operated devices. This study aimed to demonstrate the effect of direct electrical colonic stimulation on mean transit time in a chronic porcine model. The impact of stimulation and implanted material on the colonic wall was also assessed. Three pairs of electrodes were implanted into the caecal wall of 12 anaesthetized pigs. Reference colonic transit time was determined by radiopaque markers for each pig before implantation. It was repeated 4 weeks after implantation with sham stimulation and 5 weeks after implantation with electrical stimulation. Aboral sequential trains of 1-ms pulse width (10 V; 120 Hz) were applied twice daily for 6 days, using an external battery operated stimulator. For each course of markers, a mean value was computed from transit times obtained from individual pig. Microscopic examination of the caecum was routinely performed after animal sacrifice. A reduction of mean transit time was observed after electrical stimulation (19 +/- 13 h; mean +/- SD) when compared to reference (34 +/- 7 h; P = 0.045) and mean transit time after sham stimulation (36 +/- 9 h; P = 0.035). Histological examination revealed minimal chronic inflammation around the electrodes. Colonic transit time measured in a chronic porcine model is reduced by direct sequential electrical stimulation. Minimal tissue lesion is elicited by stimulation or implanted material. Electrical colonic stimulation could be a promising approach to treat specific disorders of the large bowel.

Closed loop electrical muscle stimulation in spinal cord injured rehabilitation

The effect of motor training using closed loop controlled Functional Electrical Stimulation (FES) on motor performance was studied in 5 spinal cord injured (SCI) volunteers. The subjects trained 2 to 3 times a week during 2 months on a newly developed rehabilitation robot (MotionMaker?). The FES induced muscle force could be adequately adjusted throughout the programmed exercises by the way of a closed loop control of the stimulation currents. The software of the MotionMaker? allowed spasms to be detected accurately and managed in a way to prevent any harm to the SCI persons. Subjects with incomplete SCI reported an increased proprioceptive awareness for motion and were able to achieve a better voluntary activation of their leg muscles during controlled FES. At the end of the training, the voluntary force of the 4 incomplete SCI patients was found increased by 388% on their most affected leg and by 193% on the other leg. Active mobilisation with controlled FES seems to be effective in improving motor function in SCI persons by increasing the sensory input to neuronal circuits involved in motor control as well as by increasing muscle strength.

Comparison of electrical nerve stimulation, electrical muscle stimulation and magnetic nerve stimulation to assess the neuromuscular function of the plantar flexor muscles.

INTRODUCTION: As it might lead to less discomfort, magnetic nerve stimulation (MNS) is increasingly used as an alternative to electrical stimulation methods. Yet, MNS and electrical nerve stimulation (ENS) and electrical muscle stimulation (EMS) have not been formally compared for the evaluation of plantar flexor neuromuscular function. METHODS: We quantified plantar flexor neuromuscular function with ENS, EMS and MNS in 10 volunteers in fresh and fatigued muscles. Central alterations were assessed through changes in voluntary activation level (VAL) and peripheral function through changes in M-wave, twitch and doublet (PS100) amplitudes. Discomfort associated with 100-Hz paired stimuli delivered with each method was evaluated on a 10-cm visual analog scale. RESULTS: VAL, agonist and antagonist M-wave amplitudes and PS100 were similar between the different methods in both fresh and fatigued states. Potentiated peak twitch was lower in EMS compared to ENS, whereas no difference was found between ENS and MNS for any parameter. Discomfort associated with MNS (1.5 ± 1.4 cm) was significantly less compared to ENS (5.5 ± 1.9 cm) and EMS (4.2 ± 2.6 cm) (p < 0.05). CONCLUSION: When PS100 is used to evaluate neuromuscular properties, MNS, EMS and ENS can be used interchangeably for plantar flexor neuromuscular function assessment as they provide similar evaluation of central and peripheral factors in unfatigued and fatigued states. Importantly, electrical current spread to antagonist muscles was similar between the three methods while discomfort from MNS was much less compared to ENS and EMS. MNS may be potentially employed to assess neuromuscular function of plantar flexor muscles in fragile populations.