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PubMed1990

Contraction characteristics of the human quadriceps muscle during percutaneous electrical stimulation.

Percutaneous electrical stimulation was used to study the force response of the quadriceps muscle. The normal frequency dependence of force was investigated in muscles at rest and after fatiguing contractions. A comparison between force response during fatigue induced by electrical stimulation at different frequencies and by voluntary work suggested equal changes in contractility, irrespective of the fatigue-inducing procedure. In fresh muscle we found a linear relation between stimulation period (10-100 ms) and force. At fatigue the relation changes with maximal deviation from linearity at a 50-ms period (20 Hz). There is a rapid recovery of high frequency force whereas the low frequency response remains low even after 30 min rest. At very low frequencies there is initially unexpectedly high force in fatigued muscle. This could be a result of increased fusion of twitches with initially prolonged relaxation time. To study the twitch summation we compared experimental results in a wide frequency range with computer-simulated twitch summations and present the frequency dependence of summation processes in human quadriceps muscle.

Adult↗

PubMed1998

Advantages and pitfalls of functional electrical stimulation.

Functional electrical stimulation has many theoretical advantages. In clinical practice, very favorable results have been repeatedly presented. The experience now encompasses thirty years and a very large number of incontinent patients. Although the methods are widely used, they are differently appreciated. Problems include the fact that functional electrical stimulation does not belong to the therapeutic traditions in urology and gynecology, there is a need of personal training for successful treatment and there is a lack of systematic studies on different clinical applications. Significant advantages are a rational physiological basis, applicability in a variety of lower urinary tract dysfunctions, few side effects and a potential curative effect.

Electric Stimulation↗

PubMed1986

Treatment of tinnitus by external electrical stimulation.

Transcutaneous electrical stimulation was used in 5 consecutive patients suffering from troublesome tinnitus. The study included three parts. Part one constituted an open trial using the stimulation equipment. During this part, 2 patients reported a reduced subjective tinnitus loudness. These 2 patients proceeded to part two where the effect from the stimulation equipment was compared with the effect from a placebo apparatus in an experimental double-blind trial. One of these 2 patients reported similar effects from active stimulation and placebo, while the other patient reported a constant positive effect from the active stimulation and no effect at all from placebo. The latter patient continued to part three where the effect of the equipment was studied over a 3-month period. Throughout the study, continuous self-recordings of the complaints was used. The results show that the electrical stimulation had a genuine tinnitus-reducing effect in one patient, remaining over a 3-month period, a positive placebo effect in one patient, but no effect in 3 patients. To determine the applicability of this method in the clinical population, carefully designed outcome studies, with appropriate control conditions, are required.

Adult↗

PubMed1990

Mandibular reconstruction using electrically stimulated periosteum.

Electrically stimulated periosteum (ESP) grafting to a 12-year-old female patient who had had a segmental mandibulectomy in the anterior region following a diagnosis of Ewing's sarcoma was tried for the mandibular reconstruction. One year after the ESP transplantation, examination of the patient showed that fine, radio-opaque bone formation had occurred. The new technique consists of 1) electrical stimulation of the tibial periosteum with 20 microamperes for five weeks, and then 2) ESP transplantation into a titanium mesh tray placed in the mandibulectomized region. In the present report, these new procedures are detailed, and the process of calcification in the transplanted ESP is discussed.

Bone Transplantation↗

PubMed1989

Restoration of gait during two to three weeks of therapy with multichannel electrical stimulation.

Multichannel electrical stimulation was applied in 20 patients with hemiplegia secondary to stroke or head injury using a six-channel microprocessor stimulator-stride analyzer to restore independent gait and to reestablish a normal gait pattern in a two- to three-week therapy period. The therapy was followed up at every session by a stride analyzer incorporated into the stimulator. At the beginning and at the end of the therapy period, each subject's gait was measured with a ground reaction measuring system. Statistical results and observations are presented for the group of 20 subjects, and a detailed description of the results is given for one subject who is representative of the whole group. According to the measured gait characteristics, gait improved significantly in all subjects during the therapy period, resulting in a partly or completely independent gait. The subjects' posture and endurance also improved, and they spontaneously learned how to use a crutch. The measurements and visual assessment of the subjects' progress indicate that the described treatment protocol offers good prospects for faster and more efficient gait rehabilitation in severely impaired patients. To determine the efficacy of gait therapy with multichannel electrical stimulation, a comparative study of conventional therapeutic methods and the method described in this article should be conducted.

Adolescent↗

PubMed1999

Commercial implementation of postmortem electrical stimulation.

Postmortem electrical stimulation (ES) of meat-producing species is not a new technology but has recently been adapted for commercial use with poultry. Unlike its use in red meats to reduce the inherent toughness and facilitate grading, the application of ES in poultry is to reduce the need for aging carcasses before deboning by reducing the toughening that occurs when the meat is deboned early after death. The current practice of aging intact carcasses or breast halves 4 h or more prior to deboning costs the industry millions of dollars in lost yield and creates logistical problems in plants. Electrical stimulation reduces the need for aging by accelerating the energy depletion involved in rigor mortis development to reduce the shortening-related toughness of early deboning. Some ES systems have the additional effect of inducing physical disruption in the muscle, reducing muscle integrity and counteracting the toughness induced by early deboning. Several ES systems have been reported in the literature with some having been recently developed into commercial-scale devices. With this new technology and the growing pressure on processors to maximize operating efficiencies, processors will need to evaluate their tenderness management programs and customer demands to determine the role ES can play in their operations.

Animals↗

PubMed2005

Driving gastric electrical activity with electrical stimulation.

Gastric electrical stimulation (GES) therapy is generating a lot of interest, but it is still investigational. Its efficacy in driving gastric electrical activity and improving motility, and the ideal frequency for bringing this about are still controversial. In this study, a rule-based computer model of tissue electrical response to stimulation was developed to examine the interaction between tissue electrical refractoriness and the onset of tissue activation. The results were compared to response to GES in 8 dogs implanted with electrodes and strain gauges and stimulated at frequencies ranging from 3 to 30 cycles/min. Simulated electrical control activity at an intrinsic frequency of 5/min was entrained from 2.0 cycles/min to 7.92 cycles/min. The regularity of the ECA elicited by stimulation depended on the number of pulses injected. Electrical stimulation in canine stomach entrained the native electrical control activity from a baseline average of 5.14 +/- 0.32 cycles/min up to 9.2 cycles/min. Contractile response to stimulation at 20-30 cycles/min were significantly higher (p < 0.05). Computer simulation of GES may be a useful tool to complement and reduce some of the costs associated with empirical studies of gastric electrical stimulation in establishing its possible use in treating drug refractory gastroparesis.

Animals↗

PubMed2004

The effect of joint angle on the timing of muscle contractions elicited by neuromuscular electrical stimulation.

Neuromuscular electrical stimulation was used to evoke isometric knee extension contractions in seven individuals with spinal cord injury (SCI) and the time for knee extension torque to rise and fall was measured across a range of knee angles. The stimulated muscles took more than twice as long to develop 50% of maximum torque at an angle of 15 degrees, compared to an angle of 90 degrees. This time difference comprised both an increased delay before torque rose above resting levels (31 +/- 3 ms at 90 degrees, 67 +/- 24 ms at 15 degrees), and a prolonged duration over which torque was rising (72 +/- 14 ms at 90 degrees, 140 +/- 62 ms at 15 degrees). There was no change, however, in the time taken for torque to fall after cessation of stimulation at different knee angles (58 +/- 5-ms delay, 60 +/- 11-ms fall time). The difference in torque rise time with joint angle has implications for modeling functional activities that differ greatly in their joint angles. This study provides regression equations whereby activation times for the quadriceps muscles of individuals with SCI can be predicted for specific angles of knee flexion.

Adult↗

PubMed1975

Optimal parameters for eliciting cardio-acceleration by electrical stimulation of the ventromedial hypothalamus.

The ventromedial hypothalamus of the unrestrained cat was stimulated electrically through permanent electrodes. The stimulation parameters, amplitude, duration and frequency of the square wave pulses were combined to produce a 20% increase of the resting heart rate value. The total electric charge for each parametric combination was calculated. The charge per stimulation (10 s) varied from about 1 to 100 micro-coulombs, depending on the parametric combination used. The response could therefore not be expressed as a function of the charge but depended on the individual parametric combinations. The relation among the stimulation parameters and the total amount of electric charge of the pulses was estimated by the correlation technique. The results suggested that about 60% of the variation in the electric charge resulting in the constant response was due to the variation of the pulse repetition frequency. The optimal parameters for eliciting cardio-acceleration in the cat by stimulation of the ventromedial hypothalamus seem to be pulse durations between 0.1 and 0.5 ms and pulse repetition frequencies below 100 P/s, with pulse amplitude as the dependent variable.

Animals↗

PubMed1988

Electrical stimulation of cochlear efferents at the round window reduces auditory desensitization in guinea pigs. I. Dependence on electrical stimulation parameters.

Electrical stimulation at the round window with pulsed short trains has been shown to elicit classical efferent effects on N1 amplitudes at the cochlea. This report demonstrates that round window stimulation as a continuous burst can reduce temporary threshold shifts (TTS) caused by a simultaneous monaural loud sound exposure. This result is similar to recent reports that stimulation of the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle can reduce TTS. Like COCB stimulation at the brainstem, the effect of round window stimulation could be abolished by strychnine, with a time course paralleling the blocking action of strychnine on the traditional COCB effects of pulsed short trains on N1 amplitudes. This report also established parameters for optimal effects of the round window stimulus and found them to be similar to the optimal parameters for the effects of brainstem stimulation on TTS. Tonic effects on TTS were also observed, with reductions in TTS being obtained as much as 7 min after a 1 min-long round window stimulus. Such tonic effects did not appear to be due to persistent effects at the cochlea but were suggested to be due to a long term resetting of some central site activated by antidromic stimulation from the round window.

Animals↗

PubMed1996

Electrical stimulation of the lingual musculature in obstructive sleep apnea.

The influence of lingual muscle activity on airflow dynamics in the upper airway was examined in nine patients with obstructive sleep apnea. Muscles that retract the tongue (hyoglossus and styloglossus) and protrude the tongue (genioglossus) were selectively stimulated electrically during sleep with fine wire electrodes placed intramuscularly transorally. We confirmed that stimulation with 50 Hz and 40-microseconds pulse duration did not elicit changes in electroencephalographic patterns or heart rate or alter airflow after the stimulation burst had ceased. The highest stimulus intensity that did not arouse patients from sleep was then utilized to examine the effect of lingual muscle recruitment on airflow dynamics during steady-state periods of inspiratory airflow limitation. When applying a stimulus burst during single inspirations, maximal inspiratory airflow decreased by 239 +/- 177 ml/s (P < 0.05) during retractor stimulation, whereas maximal inspiratory airflow increased by 217 +/- 93 ml/s during protrusor stimulation (P < 0.001) compared with breaths immediately before and after the stimulated breath. When consecutive inspirations were stimulated repeatedly, protrusor stimulation decreased the frequency of obstructive breathing episodes in four patients breathing at 3.9 +/- 3.4 (SD) cmH2O nasal pressure. The findings suggest that stimulation of the lingual muscles can increase or decrease airflow depending on the specific muscles stimulated without arousing patients from sleep.

Adult↗

PubMed1989

Effects of electrical stimulation of the superior cervical ganglia on the number of "synaptic" ribbons and the activity of melatonin-forming enzymes in the rat pineal gland.

Melatonin metabolism in the mammalian pineal gland is under the clear influence of sympathetic fibers originating in the superior cervical ganglia (SCG). Previous studies suggested that pineal "synaptic" ribbons (SR) as well are regulated by the gland's sympathetic innervation. To gain more insight into the mechanisms involved, we examined the effects of sympathetic stimulation on SR number and on the activity of melatonin forming enzymes, serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT). The SCG in adult male rats were stimulated electrically during daytime for either 15 or 120 min. Immediately following stimulation, the glands were removed and processed for electron microscopy and for the determination of NAT and HIOMT activities. No differences in pineal SR number, size or location were found in rats stimulated with either parameters when compared with sham-stimulated or control animals. While the activity of HIOMT remained unchanged, the activity of NAT was also unaltered following 15 min of stimulation, but was augmented approximately three-fold in animals stimulated for 120 min. It is concluded that if SR in the rat pineal gland are under sympathetic control, the regulation is different from that involved in melatonin formation.

Acetylserotonin O-Methyltransferase↗

PubMed1991

Different mechanisms of action of agents acting on beta-adrenoceptors in barium-stimulated and electrically-stimulated rat vas deferens.

1. The relaxation induced by beta-adrenoceptor agonists in rat vas deferens was examined under two different experimental conditions: on electrically-induced twitch responses (35 V, 3 ms, 0.07 Hz), and on contractions induced by single doses of barium chloride (300 microM). The experiments were performed in vasa of reserpine-treated rats, after blockade of alpha-adrenoceptors and extraneuronal uptake with dibenamine (10 microM, 30 min), and neuronal uptake with cocaine (10 microM). 2. When twitch responses were used, the values of pD2, interpolated from cumulative concentration-response curves for isoprenaline (Iso), adrenaline (Ad), and noradrenaline (NA) showed a rank order of potency consistent with the presence of beta 2-adrenoceptors (Iso greater than Ad much greater than NA). 3. When twitch responses were used, the non-selective beta-antagonist, propranolol, caused a concentration-dependent parallel shift to the right of Iso concentration-response curves. Similar shifts were obtained by use of the beta 2-antagonist, isopropylmethoxamine (IMA), and higher doses of the beta 1-antagonist, practolol, according to the expectations from receptor occupation theory. Practolol presented the lowest value of pKB, 5.03, corroborating the presence of beta 2-adrenoceptors. 4. When twitch responses were used, and Ad or NA employed instead of Iso, the antagonists produced shifts of concentration-response curves which were smaller than expected from theory, precluding the determination of pKB values. This indicates that other mechanisms are involved besides an interaction with a single population of postsynaptic beta 2-adrenoceptors. 5. When barium chloride was used instead of twitch responses, although the potencies of Iso and Ad were increased respectively by about 30 fold and 5 fold, the rank order of potency was still consistent with an interaction with beta 2-adrenoceptors. In addition, the antagonists produced parallel and concentrationdependent shifts of the curves of all the agonists, as expected from receptor theory. The values of pKB for a given antagonist were not modified by interchanging the agonists used, indicating a typical interaction with a single population of beta 2-adrenoceptors. When compared to the field-stimulated vas, the values of pKB for propranolol and IMA against isoprenaline were respectively 1.3 and 0.6 log units larger. These results suggest the beta l-adrenoceptor agents act by different mechanisms of action in barium-stimulated and electrically-stimulated vas. 6. It is suggested that when barium is used, the effects of agents acting on beta l-adrenoceptors are mediated only by postsynaptic beta 2-receptors, while other complicating factors, probably nerve-dependent presynaptic mechanisms, may be involved with electrical stimulation.

Adrenergic beta-Agonists↗

PubMed1995

VEGF gene expression is upregulated in electrically stimulated rat skeletal muscle.

Vascular endothelial growth factor (VEGF; also called vascular permeability factor) is a secreted mitogen with distinct target cell specificity for vascular endothelial cells. Hypoxia upregulates VEGF expression, making it a likely mediator of the angiogenesis that occurs in poorly perfused tissues. The purpose of this study was to determine whether VEGF gene expression is upregulated in chronically stimulated skeletal muscles, where hypoxia is thought to trigger the growth of blood vessels. The right anterior tibialis and extensor digitorum longus muscles of 12 rats were stimulated electrically (10 Hz, 300 microseconds pulses) for up to 21 days by way of the peroneal motor nerve. The contralateral muscles served as control. Northern analysis showed that VEGF mRNA levels increased by approximately sixfold after 4 days of stimulation and then decreased gradually over the next several days. VEGF mRNA levels were still elevated by two- to threefold after 21 days of stimulation. Higher VEGF mRNA levels in the early stages of muscle stimulation and gradually decreasing levels in later stages are consistent with a metabolic hypothesis in which tissue oxygenation controls VEGF expression. These studies support the hypothesis that VEGF has a physiological role in promoting angiogenesis in stimulated skeletal muscle.

Animals↗

PubMed1980

Reflex bladder activity induced by electrical stimulation of hind limb somatic afferents in the cat.

Methods used and results obtained in a study of reflex responses of the bladder were as follows. Intravesical pressure was recorded continuously by the balloon method in chloralose--urethane anaesthetized cats. Various afferent fibres of hind limb cutaneous and muscle nerves were stimulated electrically, and the resulting changes in vesical functions were examined. It was found that: (1) when the bladder was nearly empty and quiescent, repetitive stimulation of group III (thin myelinated) and IV (non-myelinated) cutaneous or muscle afferent fibres of hind limb nerves caused a reflex increase in the vesical tonus. This somato-vesical excitatory reflex was propriospinal with its efferent are mainly in the pelvic nerves; (2) when there were spontaneous, large (amplitude above 300--400 mm H2O), rhythmic (about 1.0--2.5/min) micturition contractions of the expanded bladder, these contractions were inhibited by repetitive stimulation of the group III and IV cutaneous or muscle afferent fibres of hind limb nerves. The inhibition was sometimes followed by subsequent larger micturition contractions. The efferent arc for this somato-vesical inhibitory reflex was also in the pelvic nerves. Supraspinal structures were essential for producing the micturition contractions; (3) stimulation of group III and IV afferent fibres together was more effective than stimulation of the group III afferent fibres alone in activating either the excitatory or inhibitory somato-vesical reflex pathways.

Animals↗

PubMed1995

Electrical stimulation of the centromedian thalamic nucleus in control of seizures: long-term studies.

Five patients with chronic incapacitating seizures averaging 15-5,000/month were selected for study. All patients had more than one seizure type and had received maximal doses of antiepileptic drugs (AEDs). The centromedian thalamic nucleus (CM) was stimulated electrically through bilateral multicontact platinum electrodes stereotaxically placed in CM and connected to internalized pulse generators. Electrophysiologic confirmation of electrode position included thalamically elicited recruiting responses and EEG desynchronization recorded at the scalp. Stimulation parameters were adjusted individually in the range of 450-800-microA intensity, 65 pps, 0.09 ms, in 1-min trains, alternating right and left side stimulation and with 4-min intervals delivered for 2 h/day. Quantitative evaluation included frequency of seizures/month, number of maximal interictal paroxysmal discharges, and frequency of background activities counted in selected scalp EEG samples, taken throughout the observation period (7-33 months). Significance of changes was evaluated by parametric Student's t test. Generalized tonic-clonic seizures (GTC) decreased dramatically, almost disappearing in all cases (p < 0.001), with a significant reduction in interictal paroxysmal discharges (p < 0.01) and a tendency toward an increase in EEG background frequency. Other generalized seizures (atypical absences) decreased significantly, but there was no change in the number of complex partial seizures (CPS). CM stimulation is useful in control of GTC, but its beneficial effect on other seizure types has not been established.

Adult↗

PubMed1982

Electrical stimulation of osteogenesis: studies of the cathode effect on rabbit femur.

Three series of experiments were performed to evaluate the effect of 20 microampère constant direct current on rabbit femora. Stainless steel cathodes were introduced into the medullary cavity and anodes were placed subcutaneously. Both femora were operated on in the same manner but only the right femur was stimulated electrically. The osteogenic effect was determined histomorphometrically in two of the series. No difference in osteogenic response between the right and the left femora was found. In the third series, the femora were divided into proportionally equal parts and bone volume, ash-weight and activity of 85Sr were determined. A non-significant increase in new bone formation in the cathodal region of the right femora was noted. Our conclusion is that direct cathodal current has a weak stimulating effect on new bone formation in rabbit femora.

Animals↗

PubMed2003

Electrical stimulation for intraoperative evaluation of thoracic pedicle screw placement.

STUDY DESIGN: Thoracic pedicle screws were stimulated electrically while recording electromyography (EMG) activity in associated muscle groups intraoperatively. Screw position was then evaluated after surgery using computed tomography (CT). The CT results were compared with evoked EMG threshold values. OBJECTIVE: To report our experience with pedicle screw stimulation in thoracic vertebrae in 22 patients who underwent thoracic level spinal instrumentation from May 1999 to March 2001. SUMMARY OF BACKGROUND DATA: Pedicle screw stimulation for intraoperative assessment of screw placement has been reported in lumbosacral spinal procedures. Evoked EMG thresholds >10 or 11 mA are associated with increased probability of vertebral cortex violation and postoperative complications. Thresholds >15 mA provide a 98% confidence of accurate screw positioning on postoperative CT scans. METHODS: Evoked EMG activity was recorded from ulnar carpal flexors, intercostals, or abdominal muscle groups, depending on the level of screw placement. Postoperative CT scans were read by a staff orthopedic spine surgeon, a senior resident in orthopedics, and a musculoskeletal radiologist. RESULTS: Results of 87 screws are reported. Five screws (5.7%) showed penetration on postoperative CT scans. Six screws (6.9%) had stimulation thresholds < or =11 mA, of which three showed cortical breakthrough. Of the 81 screws with thresholds >11 mA, 79 (97.5%) were within the vertebra. No postoperative neurologic complications were noted in any of the 22 patients. CONCLUSION: These results are consistent with previous studies of lumbosacral pedicle screws. In this series, stimulation thresholds >11 mA have a 97.5% negative predictive value, suggesting that cortical violation is highly unlikely. Although judgment of screw placement should not depend solely on stimulation thresholds, pedicle screw stimulation may provide rapid and useful intraoperative information on screw placement during procedures involving the use of thoracic pedicle screws.

Bone Screws↗