Plantar Nerve Stimulation Research Articles

Anatomical Exploration of the KI1 Acupoint: Implications for Medial and Lateral Plantar Nerve Stimulation.

Background and Objectives: This study aims to identify the precise anatomical location and therapeutic mechanisms of the KI1 acupoint (Yongquan) in relation to foot muscles and nerves, known for treating neurological disorders and pain. Materials and Methods: Dissection of six cadavers at Chungnam National University College of Medicine examined KI1's relation to the foot's four-layer structure. Results: The KI1 acupoint was located in the superficial and deep layers of the plantar foot, adjacent to significant nerves like the medial and lateral plantar nerves. Differences in the acupoint's exact location between genders were noted, reflecting variances in foot morphology. KI1 acupuncture was found to stimulate the muscle spindles and nerve fibers essential for balance and bipedal locomotion. This stimulation may enhance sensory feedback, potentially improving cognitive functions and balance control. Conclusions: This anatomical insight into KI1 acupuncture underpins its potential in neurological therapies and pain management.

Neuromodulation of spinal reflex pathway for the treatment of detrusor overactivity by medial plantar nerve stimulation at surface of sole of foot in patients with spinal cord injury.

Suprasacral spinal cord lesions are prone to have neurogenic detrusor overactivity leading to urinary incontinence. Current medical management has known side-effects and often surgical managements are irreversible. Electrical stimulation to modulate spinal reflex pathway having same nerve root as urinary bladder is reported in the literature. This study aimed to reduce detrusor overactivity in patients with spinal cord injury (SCI) using surface electrical stimulation of medial plantar nerve at the sole of foot. Twenty adults with SCI having episode of at least 1 leak/day due to detrusor overactivity as diagnosed by cystometrogram (CMG), were on clean intermittent catheterization and ankle jerk was present consented for the study. Participants were asked to maintain bladder diary a week before and during 2 weeks of treatment. CMG was done on day-0 and day-14. cmcUroModul@tor®, an inhouse developed electrical stimulator was used for ½ h daily for period of 2 weeks. Patient satisfaction feedback questionnaire was taken on completion of treatment. CMG data were analyzed using Wilcoxon signed-ranked test while bladder diary was analyzed using binomial distribution. P < 0.05 was considered as statistically significant. Institutional Review Board (IRB) and ethics committee of Christian Medical College, Vellore, approved the study (CMC/IRB/11061). Statistical significant improvement in maximum detrusor pressure (P = 0.03) and cystometric capacity (P = 0.04) was observed. Of 20 subjects, 18 showed improvement in bladder diary. Neuromodulation of medial plantar nerve at sole of foot by surface electrical stimulation is non-invasive, cost-effective, and alternative simple treatment modality for urinary incontinence due to detrusor overactivity.

Transcutaneous medial plantar nerve stimulation in women with idiopathic overactive bladder.

To define transcutaneous medial plantar nerve stimulation (T-MPNS) as a new neuromodulation method and assess the efficacy of T-MPNS on quality of life (QoL) and clinical parameters associated with incontinence in women with idiopathic overactive bladder (OAB). Twenty-one women were included in this study. All women received T-MPNS. Two self-adhesive surface electrodes were positioned with the negative electrode near the metatarsal-phalangeal joint of the great toe on the medial aspect of the foot and the positive electrode 2 cm inferior-posterior of the medial malleolus (in front of the medio-malleolar-calcaneal axis). T-MPNS was performed 2 days a week, 30 minutes a day, for a total of 12 sessions for 6 weeks. Women were evaluated for incontinence severity (24-h pad test), 3-day voiding diary, symptom severity (Overactive Bladder Questionnaire [OAB-V8]), QoL (Quality of Life-Incontinence Impact Questionnaire [IIQ-7]), positive response and cure-improvement rates, and treatment satisfaction at baseline and at the 6th week. Statistically significant improvement was found in the severity of incontinence, frequency of voiding, incontinence episodes, nocturia, number of pads, symptom severity, and QoL parameters at the 6th week compared with baseline. Treatment satisfaction, treatment success, and cure or improvement rates were found to be high at the 6th week. T-MPNS was first described in the literature as a new neuromodulation method. We conclude that T-MPNS is effective on both clinical parameters and QoL associated with incontinence in women with idiopathic OAB. Randomized controlled multicenter studies are needed to validate the effectiveness of T-MPNS.

Vibration attenuates spasm-like activity in humans with spinal cord injury.

Cutaneous reflexes were tested to examine the neuronal mechanisms contributing to muscle spasms in humans with chronic spinal cord injury (SCI). Specifically, we tested the effect of Achilles and tibialis anterior tendon vibration on the early and late components of the cutaneous reflex and reciprocal Ia inhibition in the soleus and tibialis anterior muscles in humans with chronic SCI. We found that tendon vibration reduced the amplitude of later but not earlier cutaneous reflex in the antagonist but not in the agonist muscle relative to the location of the vibration. In addition, reciprocal Ia inhibition between antagonist ankle muscles increased with tendon vibration and participants with a larger suppression of the later component of the cutaneous reflex had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration attenuates late cutaneous spasm-like reflex activity, likely via reciprocal inhibitory mechanisms, and may represent a method, when properly targeted, for controlling spasms in humans with SCI. The neuronal mechanisms contributing to the generation of involuntary muscle contractions (spasms) in humans with spinal cord injury (SCI) remain poorly understood. To address this question, we examined the effect of Achilles and tibialis anterior tendon vibration at 20, 40, 80 and 120Hz on the amplitude of the long-polysynaptic (LPR, from reflex onset to 500ms) and long-lasting (LLR, from 500ms to reflex offset) cutaneous reflex evoked by medial plantar nerve stimulation in the soleus and tibialis anterior, and reciprocal Ia inhibition between these muscles, in 25 individuals with chronic SCI. We found that Achilles tendon vibration at 40 and 80Hz, but not other frequencies, reduced the amplitude of the LLR in the tibialis anterior, but not the soleus muscle, without affecting the amplitude of the LPR. Vibratory effects were stronger at 80 than 40Hz. Similar results were found in the soleus muscle when the tibialis anterior tendon was vibrated. Notably, tendon vibration at 80Hz increased reciprocal Ia inhibition between antagonistic ankle muscles and vibratory-induced increases in reciprocal Ia inhibition were correlated with decreases in the LLR, suggesting that participants with a larger suppression of later cutaneous reflex activity had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration suppresses late spasm-like activity in antagonist but not agonist muscles, likely via reciprocal inhibitory mechanisms, in humans with chronic SCI. We argue that targeted vibration of antagonistic tendons might help to control spasms after SCI.

Wide-pulse, high-frequency, low-intensity neuromuscular electrical stimulation has potential for targeted strengthening of an intrinsic foot muscle: a feasibility study

BackgroundStrengthening the intrinsic foot muscles is a poorly understood and largely overlooked area. In this study, we explore the feasibility of strengthening m. abductor hallucis (AH) with a specific paradigm of neuromuscular electrical stimulation; one which is low-intensity in nature and designed to interleave physiologically-relevant low frequency stimulation with high-frequencies to enhance effective current delivery to spinal motoneurones, and enable a proportion of force produced by the target muscle to be generated from a central origin. We use standard neurophysiological measurements to evaluate the acute (~ 30 min) peripheral and central adaptations in healthy individuals.MethodsThe AH in the dominant foot of nine healthy participants was stimulated with 24 × 15 s trains of square wave (1 ms), constant current (150% of motor threshold), alternating (20 Hz–100 Hz) neuromuscular electrical stimulation interspersed with 45 s rest. Prior to the intervention, peripheral variables were evoked from the AH compound muscle action potential (Mwave) and corresponding twitch force in response to supramaximal (130%) medial plantar nerve stimulation. Central variables were evoked from the motor evoked potential (MEP) in response to suprathreshold (150%) transcranial magnetic stimulation of the motor cortex corresponding to the AH pathway. Follow-up testing occurred immediately, and 30 min after the intervention. In addition, the force-time-integrals (FTI) from the 1st and 24th WPHF trains were analysed as an index of muscle fatigue. All variables except FTI (T-test) were entered for statistical analysis using a single factor repeated measures ANOVA with alpha set at 0.05.ResultsFTI was significantly lower at the end of the electrical intervention compared to that evoked by the first train (p < 0.01). Only significant peripheral nervous system adaptations were observed, consistent with the onset of low-frequency fatigue in the muscle. In most of these variables, the effects persisted for 30 min after the intervention.ConclusionsAn acute session of wide-pulse, high-frequency, low-intensity electrical stimulation delivered directly to abductor hallucis in healthy feet induces muscle fatigue via adaptations at the peripheral level of the neuromuscular system. Our findings would appear to represent the first step in muscle adaptation to training; therefore, there is potential for using WPHF for intrinsic foot muscle strengthening.

Cutaneous mechanisms of isometric ankle force control

The sense of force is critical in the control of movement and posture. Multiple factors influence our perception of exerted force, including inputs from cutaneous afferents, muscle afferents and central commands. Here, we studied the influence of cutaneous feedback on the control of ankle force output. We used repetitive electrical stimulation of the superficial peroneal (foot dorsum) and medial plantar nerves (foot sole) to disrupt cutaneous afferent input in 8 healthy subjects. We measured the effects of repetitive nerve stimulation on (1) tactile thresholds, (2) performance in an ankle force-matching and (3) an ankle position-matching task. Additional force-matching experiments were done to compare the effects of transient versus continuous stimulation in 6 subjects and to determine the effects of foot anesthesia using lidocaine in another 6 subjects. The results showed that stimulation decreased cutaneous sensory function as evidenced by increased touch threshold. Absolute dorsiflexion force error increased without visual feedback during peroneal nerve stimulation. This was not a general effect of stimulation because force error did not increase during plantar nerve stimulation. The effects of transient stimulation on force error were greater when compared to continuous stimulation and lidocaine injection. Position-matching performance was unaffected by peroneal nerve or plantar nerve stimulation. Our results show that cutaneous feedback plays a role in the control of force output at the ankle joint. Understanding how the nervous system normally uses cutaneous feedback in motor control will help us identify which functional aspects are impaired in aging and neurological diseases.

Short-Latency Crossed Inhibitory Responses in the Human Soleus Muscle

Even though interlimb coordination is critical in bipedal locomotion, the role of muscle afferent mediated feedback is unknown. The aim of this study was to establish if ipsilateral muscle generated afferent feedback can influence contralateral muscle activation patterns in the human lower limb and to elucidate the mechanisms involved. The effect of ipsilateral tibial nerve stimulation on contralateral soleus (cSOL) responses were quantified. Three interventions were investigated, 1) electrical stimulation applied to the tibial nerve at stimulation intensities from 0 to 100% of maximal M-wave (M-max) with the cSOL contracted from 5 to 15% of maximal voluntary contraction (MVC) and 15 to 30% MVC, 2) ispsilateral tibial nerve stimulation at 75% M-max prior to, during, and following the application of ischemia to the ipsilateral thigh. 3) Electrical stimulation applied to the ipsilateral sural (SuN) and medial plantar nerves at stimulation intensities from 1 to 3 times perceptual threshold. A short-latency depression in the cSOL electromyogram (EMG; onset: 37-41 ms) was observed following ipsilateral tibial nerve stimulation. The magnitude of this depression increased (P = 0.0005 and P = 0.000001) with increasing stimulus intensities. Ischemia delayed the time of the minimum of the cSOL depression (P = 0.04). SuN and medial plantar nerve stimulation evoked a longer latency depression [average; 91.2 ms (SuN); 142 ms (medial plantar nerve)] and therefore do not contribute to the response. This is the first study to demonstrate a short-latency depression in the cSOL following ipsilateral tibial nerve stimulation. Due to its short latency, the response is spinally mediated. The involvement of crossed spinal interneurons receiving input from low-threshold muscle afferents is discussed.

Inhibition from the plantar nerve to soleus muscle during the stance phase of walking

The purpose of this study is to investigate the effect and the circuit from the branch of tibial (plantar) nerve to soleus muscle and its modulation during walking in humans. Stimulation of the plantar nerve produced short latency inhibition of soleus EMG activity and the H-reflex in humans. The threshold of afferent fibers was lower than that of motor fibers. This inhibition did not converge to disynaptic reciprocal Ia inhibition nor did inhibition from the cutaneous nerve of the big toe, but to Ib inhibition from the medial gastrocnemius nerve. The inhibitory pathway from the plantar nerve therefore is considered to include Ib inhibitory interneurones. Modulation of the inhibition was investigated during walking. Less EMG depression after plantar nerve stimulation occurred in the stance phase of walking than for tonic or dynamic plantar flexion at similar background EMG activity level. The inhibition of the soleus H-reflex after plantar nerve stimulation was also decreased during the stance phase. For investigating the influence of load on the inhibition from the plantar nerve, more EMG depression occurred in the stance phase with body unloading. Similar findings were observed in Ib inhibition from the medial gastrocnemius nerve, but not in disynaptic reciprocal Ia inhibition to soleus muscle. It is concluded that transmission of inhibition from the plantar nerve to soleus muscle is modulated during walking. It would minimize this inhibition during the stance phase of walking and might enhance soleus muscle activity via this reflex pathway for the support of weight.

The distal hindlimb musculature of the cat: interanimal variability of locomotor activity and cutaneous reflexes.

During stereotyped behaviors such as locomotion, patterns of muscle recruitment are usually quite consistent from animal to animal, even in the face of many surgical and pharmacological reductions. However, as studies of musculoskeletal structure, neuromuscular architecture, and sensorimotor circuitry become more detailed, it is important to ask whether there is some level of organization at which individual differences begin to dominate. This study concentrated on the small muscles of the foot and ankle, using standardized methods that consistently record stereotypical electromyographic activity from prime mover muscles and that permit well-calibrated stimulation of cutaneous nerves to elicit reflexes during treadmill locomotion. Some muscles (particularly the main ankle extensors, triceps surae, and plantaris) had stereotyped activity during both unperturbed locomotion and reflex responses. Others had stereotyped activity during locomotion but variable reflex patterns among animals (tibialis anterior, extensor digitorum longus, flexor hallucis longus, and peroneus brevis). Still others had variable locomotor activity but reflexes that were consistent (flexor digitorum longus) or variable for only peroneal nerve stimulation (peroneus longus), only plantar nerve stimulation (peroneus tertius), or the two (flexor digitorum brevis). Among muscles with interanimal variability, there seemed to be no particular correlation between locomotor and reflexive recruitment in a given animal. This functional heterogeneity is discussed in terms of the development of locomotor and reflex programs and in the context of structural heterogeneity of some of these muscles that is described in the companion paper.

The effect of digital nerve stimulation on recruitment order of motor units in the first deep lumbrical muscle of the cat

The normal recruitment order of EMG spikes of the first deep lumbrical muscle of the cat's hindpaw, usually seen during cortical stimulation, pad pinch and weak plantar nerve stimulation, was temporarily reversed after stimulation of the medial digital nerve of the foot at 50 Hz for 2 min, and normal order was recovered in 2 to 10 min. The longer the period of stimulation of the medial digital nerve was, the longer the time for recovery. min. After prolonged medial digital nerve stimulation, EMG responses to pad pinch and plantar nerve stimulation were facilitated. Combination of some stimuli (e.g. cortical stimulation and plantar nerve stimulation, pad pinch and plantar nerve stimulation, plantar nerve and medial digital nerve stimulation) also produced reversal of recruitment order during the period of stimulation. A functionally single motor nerve fiber to the first deep lumbrical muscle was isolated from the motor nerve axons in L7 and S1 of the spinal cord of cats, and physiological properties of pairs of motor units whose recruitment order was temporarily altered by plantar nerve stimulation after prolonged stimulation of the medial digital nerve of a foot were examined. Motor units with large action potentials were more facilitated than motor units with small action potentials after prolonged stimulation of the medial digital nerve. The former motor units showed fast contraction time, large twitch tension, low resistance to fatigue and presence of sag-behavior. The latter motor units showed slow contraction time, small twitch tension and high resistance to fatigue. High threshold motor units with middle-sized surface EMG records were recruited after motor units with large potentials had been recruited; motor units with middle-size action potentials were beta motor axons branching to both intrafusal and extrafusal muscle fibers. The beta motor axons also showed fast conduction velocity and the presence of sag-behavior.

Response of the cat's pad eccrine sweat glands to intravascular injections of catecholamines.

1. Using a sensitive method for detecting and monitoring sweat secretion, a study has been made of the effects of adrenaline and noradrenaline on the cat's pad sweat gland activity in the anaesthetized cat.2. Intravenous or intra-arterial injections of adrenaline or noradrenaline only very occasionally caused these glands to secrete.3. The predominant effect of these drugs on glands which are already secreting in response to plantar nerve stimulation is inhibitory.4. The catecholamine inhibition could be reduced or blocked by phentolamine, but not by propranolol, dibenamine or phenoxybenzamine.5. It is concluded that these glands can be directly activated by intravascular injections of adrenaline or noradrenaline, but that the inhibitory effect of concomitant vasoconstriction usually prevents a response being detected at the skin surface.