Long-lasting depression of soleus motoneurons excitability following repetitive magnetic stimuli of the spinal cord in multiple sclerosis patients

Different Effect Sizes of Motor Skill Training Combined with Repetitive Transcranial versus Trans-Spinal Magnetic Stimulation in Healthy Subjects

Repetitive transcranial magnetic stimulation (rTMS) is used to enhance motor training (MT) performance. The use of rTMS is limited under certain conditions, such as after a stroke with severe damage to the corticospinal tract. This raises the question as to whether repetitive trans-spinal magnetic stimulation (rSMS) can also be used to improve MT. A direct comparison of the effect size between rTMS and rSMS on the same MT is still lacking. Before conducting the study in patients, we determined the effect sizes of different stimulation approaches combined with the same motor training in healthy subjects. Two experiments (E1 and E2) with 96 subjects investigated the effect size of combining magnetic stimulation with the same MT. In E1, high-frequency rTMS, rSMS, and spinal sham stimulation (sham-spinal) were applied once in combination with MT, while one group only received the same MT (without stimulation). In E2, rTMS, rSMS, and sham-spinal were applied in combination with MT over several days. In all subjects, motor tests and motor-evoked potentials were evaluated before and after the intervention period. rTMS had the greatest effect on MT, followed by rSMS and then sham-spinal. Daily stimulation resulted in additional training gains. This study suggests that rSMS increases excitability and also enhances MT performance. This current study provides a basis for further research to discover whether patients who cannot be treated effectively with rTMS would benefit from rSMS.

Sensory Stimulation of the Triceps Surae Muscle Complex Modulates Spinal Reflex Responses-A Comparison between Tapotement Massage and Repetitive Peripheral Magnetic Stimulation (rPMS)

BACKGROUND

The reduction of muscular hypertonia is important in the treatment of various diseases or rehabilitation. This study aims to test the efficacy of a 5 Hz mechanical muscle stimulation (tapotement massage) in comparison to a 5 Hz repetitive peripheral magnetic stimulation (rPMS) on the neuromuscular reflex response.

METHODS

In a randomized control trial, 15 healthy volunteers were administered with either 5 Hz rPMS, tapotement massage, or rPMS sham stimulation. The posterior tibial nerve was stimulated with rPMS and sham stimulation. The Achilles tendon was exposed to a mechanically applied high-amplitude 5 Hz repetitive tendon tapotement massage (rTTM). The tendon reflex (TR) was measured for the spinal response of the soleus muscle.

RESULTS

After rPMS, there was a reduction of the TR response (-9.8%, p ≤ 0.034) with no significant changes after sham stimulation. Likewise, TR decreased significantly (-17.4%, p ≤ 0.002) after Achilles tendon tapotement intervention.

CONCLUSIONS

These findings support the hypothesis that both afferent 5 Hz sensory stimulations contributed to a modulation within the spinal and/or supraspinal circuits, which resulted in a reduction of the spinal reflex excitability. The effects could be beneficial for patients with muscle hypertonia and could improve the functional results of rehabilitation programs.

Identifying spinal tracts transmitting distant effects of trans-spinal magnetic stimulation

Estimating the state of tract-specific inputs to spinal motoneurons is critical to understanding movement deficits induced by neurological injury and potential pathways to recovery but remains challenging in humans. In this study, we explored the capability of trans-spinal magnetic stimulation (TSMS) to modulate distal reflex circuits in young adults. TSMS was applied over the thoracic spine to condition soleus H-reflexes involving sacral-level motoneurons. Three TSMS intensities below the motor threshold were applied at interstimulus intervals (ISIs) between 2 and 20 ms relative to peripheral nerve stimulation (PNS). Although low-intensity TSMS yielded no changes in H-reflexes across ISIs, the two higher stimulus intensities yielded two phases of H-reflex inhibition: a relatively long-lasting period at 2- to 9-ms ISIs, and a short phase at 11- to 12-ms ISIs. H-reflex inhibition at 2-ms ISI was uniquely dependent on TSMS intensity. To identify the candidate neural pathways contributing to H-reflex suppression, we constructed a tract-specific conduction time estimation model. Based upon our model, H-reflex inhibition at 11- to 12-ms ISIs is likely a manifestation of orthodromic transmission along the lateral reticulospinal tract. In contrast, the inhibition at 2-ms ISI likely reflects orthodromic transmission along sensory fibers with activation reaching the brain, before descending along motor tracts. Multiple pathways may contribute to H-reflex modulation between 4- and 9-ms ISIs, orthodromic transmission along sensorimotor tracts, and antidromic transmission of multiple motor tracts. Our findings suggest that noninvasive TSMS can influence motoneuron excitability at distal segments and that the contribution of specific tracts to motoneuron excitability may be distinguishable based on conduction velocities.NEW & NOTEWORTHY This study explored the capability of trans-spinal magnetic stimulation (TSMS) over the thoracic spine to modulate distal reflex circuits, H-reflexes involving sacral-level motoneurons, in young adults. TSMS induced two inhibition phases of H-reflex across interstimulus intervals (ISIs): a relatively long-lasting period at 2- to 9-ms ISIs, and a short phase at 11- to 12-ms ISIs. An estimated probability model constructed from tract-specific conduction velocities allowed the identification of potential spinal tracts contributing to the changes in motoneuron excitability.

Top-down and bottom-up stimulation techniques combined with action observation treatment in stroke rehabilitation: a perspective

Stroke is a central nervous system disease that causes structural lesions and functional impairments of the brain, resulting in varying types, and degrees of dysfunction. The bimodal balance-recovery model (interhemispheric competition model and vicariation model) has been proposed as the mechanism of functional recovery after a stroke. We analyzed how combinations of motor observation treatment approaches, transcranial electrical (TES) or magnetic (TMS) stimulation and peripheral electrical (PES) or magnetic (PMS) stimulation techniques can be taken as accessorial physical therapy methods on symptom reduction of stroke patients. We suggest that top-down and bottom-up stimulation techniques combined with action observation treatment synergistically might develop into valuable physical therapy strategies in neurorehabilitation after stroke. We explored how TES or TMS intervention over the contralesional hemisphere or the lesioned hemisphere combined with PES or PMS of the paretic limbs during motor observation followed by action execution have super-additive effects to potentiate the effect of conventional treatment in stroke patients. The proposed paradigm could be an innovative and adjunctive approach to potentiate the effect of conventional rehabilitation treatment, especially for those patients with severe motor deficits.

Role of Cervical Spinal Magnetic Stimulation in Improving Posture and Functional Ambulation of Patients with Relapsing Remitting Multiple Sclerosis

Balance impairment is one of the hallmarks of early MS. Proprioceptive deficit was found to be one of the main causes of this imbalance. The cervical enlargement has a strong proprioceptive system, with its projections to the reticular formation and the central pattern generators, helping in rhythmic pattern generation and alternate leg movements. Repetitive trans-spinal magnetic stimulation (rTSMS) is a noninvasive technique, which can trigger massive proprioceptive afferents. Therefore, it has the potential of improving proprioceptive deficits and motor control. Objective. To determine the effectiveness of repetitive cervical magnetic stimulation in improving functional ambulation of patients with relapsing remitting multiple sclerosis (RRMS). Design. Prospective sequential clinical trial. Setting. University and academic hospital. Participants. A total of 32 participants ( $N=32$ ) with RRMS. Interventions. Outpatient rehabilitation. The 32 patients received 10 sessions over two weeks of 20 Hz cervical spinal magnetic stimulation (SMS). Both groups were assessed at baseline, after 2 weeks, then one month later. Patients were enrolled as a control group at first and received Sham SMS, and then a wash out period of one month was done for all the patients, followed by a baseline assessment. Second, the same 32 patients rejoined as the active group, which received real magnetic stimulation. Both groups performed an intensive physical therapy program with the spinal magnetic stimulation. Main Outcome Measures. Extended Disability status score (EDSS), Timed up and Go test (TUG), Mini-Best test, dynamic posturography sensory organization composite score, and motor composite score. Results. Thirty-two RRMS patients with EDSS range from 1.5 to 6. They showed statistically significant difference between active and control groups in Mini-Best test score. We divided our patients according to EDSS into 3 subgroups: (a) mild: ≤2.5, (b) moderate: 3-5.5, and (c) severe: ≥6. Mild cases showed significant differences in EDSS score, TUG test, Mini-Best test, and dynamic posturography sensory composite scale. The effect size between the different patient subgroups was also measured and showed highly significant improvements in all measured parameters among our mild patients, indicating that this subgroup could be the best responders to cervical repetitive high-frequency magnetic stimulation. Moderate cases showed highly significant improvement in TUG score and Mini-Best test and significant change in EDSS score and the dynamic posturography sensory composite score. Severe cases showed only significant improvements in TUG, Mini-Best test, and sensory composite score. Conclusion. Cervical repetitive magnetic stimulation can help improve balance and functional ambulation and decreases the risk of falls in RRMS patients, especially in the mild, low disability cases.

Controversies and Clinical Applications of Non-Invasive Transspinal Magnetic Stimulation: A Critical Review and Exploratory Trial in Hereditary Spastic Paraplegia

Magnetic stimulation is a safe, non-invasive diagnostic tool and promising treatment strategy for neurological and psychiatric disorders. Although most studies address transcranial magnetic stimulation, transspinal magnetic stimulation (TsMS) has received recent attention since trials involving invasive spinal cord stimulation showed encouraging results for pain, spasticity, and Parkinson’s disease. While the effects of TsMS on spinal roots is well understood, its mechanism of action on the spinal cord is still controversial. Despite unclear mechanisms of action, clinical benefits of TsMS have been reported, including improvements in scales of spasticity, hyperreflexia, and bladder and bowel symptoms, and even supraspinal gait disorders such as freezing and camptocormia. In the present study, a critical review on the application of TsMS in neurology was conducted, along with an exploratory trial involving TsMS in three patients with hereditary spastic paraplegia. The goal was to understand the mechanism of action of TsMS through H-reflex measurement at the unstimulated lumbosacral level. Although limited by studies with a small sample size and a low to moderate effect size, TsMS is safe and tolerable and presents consistent clinical and neurophysiological benefits that support its use in clinical practice.

Assessment of safety of self-controlled repetitive trans-vertebral magnetic stimulation

OBJECTIVE

The aim of this study was to assess safety issues of self-controlled repetitive trans-vertebral magnetic stimulation (rTVMS) in humans.

METHODS

We investigated effects of self-controlled rTVMS (≤20 Hz, ≤90% intensity) on vital signs and subjective sensations in 1690 trials of 30 healthy volunteers and 12 patients with spinal cord disorders.

RESULTS

Healthy volunteers and the patients received 4595 ± 2345, and 4450 ± 2304 pulses in one day, respectively. No serious adverse events were observed in any participants, and only minor events were seen as follows. While blood pressure was unaffected in the patients, the diastolic blood pressure increased slightly after rTVMS in healthy volunteers. The peripheral capillary oxygen saturation increased after rTVMS in healthy volunteers. "Pain" or "Discomfort" was reported in approximately 10% of trials in both participants groups. Degree of the evoked sensation positively correlated with stimulus intensity and was affected by the site of stimulation.

CONCLUSION

Self-controlled rTVMS (≤20 Hz and ≤90% intensity) did not induce any serious adverse effects in healthy volunteers and patients with spinal cord disorders.

SIGNIFICANCE

Our results indicate that rTVMS can be used safely in physiological investigations in healthy volunteers and also as treatment for neurological disorders.

Impact of Repetitive Transcranial Magnetic Stimulation on Neurocognition and Oxidative Stress in Relapsing-Remitting Multiple Sclerosis: A Case Report

Multiple sclerosis (MS) is a neurodegenerative condition whose manifestation and clinical evolution can present themselves in very different ways. Analogously, its treatment has to be personalized and the patient's response may be idiosyncratic. At this moment there is no cure for it, in addition to its clinical course sometimes being torpid, with a poor response to any treatment. However, Transcranial Magnetic Stimulation (TMS) has demonstrated its usefulness as a non-invasive therapeutic tool for the treatment of some psychiatric and neurodegenerative diseases. Some studies show that the application of rTMS implies improvement in patients with MS at various levels, but the effects at the psychometric level and the redox profile in blood have never been studied before, despite the fact that both aspects have been related to the severity of MS and its evolution. Here we present the case of a woman diagnosed with relapsing-remitting multiple sclerosis (RRMS) at the age of 33, with a rapid progression of her illness and a poor response to different treatments previously prescribed for 9 years. In view of the patient's clinical course, a compassionate treatment with rTMS for 1 year was proposed. Starting from the fourth month of treatment, when reviewing the status of her disease, the patient denoted a clear improvement at different levels. There followed out psychometric evaluations and blood analyses, that showed both an improvement in her neuropsychological functions and a reduction in oxidative stress in plasma, in correspondence with therTMS treatment.

Beyond rehabilitation in MS: Insights from non-invasive brain stimulation

Although the number of disease-modifying treatments for people with multiple sclerosis (pwMS) has meaningfully increased in the past years, targeting repair or compensation for central nervous system damage associated with the disease process remains an important clinical goal. With this aim, neurorehabilitation is a powerful approach targeting central nervous system plasticity. Another driver of brain plasticity is non-invasive brain stimulation (NIBS), receiving recent attention in neurology, particularly for its potential synergy with neurorehabilitation and as add-on treatment for several neurological conditions, from pain to fatigue to sensorimotor and cognitive deficits. In this review, we will resume the evidence exploring the neurobiological basis of NIBS and its applications to MS-related conditions.

Outcomes in spasticity after repetitive transcranial magnetic and transcranial direct current stimulations

Non-invasive brain stimulations mainly consist of repetitive transcranial magnetic stimulation and transcranial direct current stimulation. Repetitive transcranial magnetic stimulation exhibits satisfactory outcomes in improving multiple sclerosis, stroke, spinal cord injury and cerebral palsy-induced spasticity. By contrast, transcranial direct current stimulation has only been studied in post-stroke spasticity. To better validate the efficacy of non-invasive brain stimulations in improving the spasticity post-stroke, more prospective cohort studies involving large sample sizes are needed.

Noninvasive and painless magnetic stimulation of nerves improved brain motor function and mobility in a cerebral palsy case

Motor deficits in cerebral palsy disturb functional independence. This study tested whether noninvasive and painless repetitive peripheral magnetic stimulation could improve motor function in a 7-year-old boy with spastic hemiparetic cerebral palsy. Stimulation was applied over different nerves of the lower limbs for 5 sessions. We measured the concurrent aftereffects of this intervention on ankle motor control, gait (walking velocity, stride length, cadence, cycle duration), and function of brain motor pathways. We observed a decrease of ankle plantar flexors resistance to stretch, an increase of active dorsiflexion range of movement, and improvements of corticospinal control of ankle dorsiflexors. Joint mobility changes were still present 15 days after the end of stimulation, when all gait parameters were also improved. Resistance to stretch was still lower than prestimulation values 45 days after the end of stimulation. This case illustrates the sustained effects of repetitive peripheral magnetic stimulation on brain plasticity, motor function, and gait. It suggests a potential impact for physical rehabilitation in cerebral palsy.

Effect of combined treadmill training and magnetic stimulation on spasticity and gait impairments after cervical spinal cord injury

Spasticity and gait impairments are two common disabilities after cervical spinal cord injury (C-SCI). In this study, we tested the therapeutic effects of early treadmill locomotor training (Tm) initiated at postoperative (PO) day 8 and continued for 6 weeks with injury site transcranial magnetic stimulation (TMSsc) on spasticity and gait impairments after low C6/7 moderate contusion C-SCI in a rat model. The combined treatment group (Tm+TMSsc) showed the most robust decreases in velocity-dependent ankle torques and triceps surae electromyography burst amplitudes that were time locked to the initial phase of lengthening, as well as the most improvement in limb coordination quantitated using three-dimensional kinematics and CatWalk gait analyses, compared to the control or single-treatment groups. These significant treatment-associated decreases in measures of spasticity and gait impairment were also accompanied by marked treatment-associated up-regulation of dopamine beta-hydroxylase, glutamic acid decarboxylase 67, gamma-aminobutyric acid B receptor, and brain-derived neurotrophic factor in the lumbar spinal cord (SC) segments of the treatment groups, compared to tissues from the C-SCI nontreated animals. We propose that the treatment-induced up-regulation of these systems enhanced the adaptive plasticity in the SC, in part through enhanced expression of pre- and postsynaptic reflex regulatory processes. Further, we propose that locomotor exercise in the setting of C-SCI may decrease aspects of the spontaneous maladaptive segmental and descending plasticity. Accordingly, TMSsc treatment is characterized as an adjuvant stimulation that may further enhance this capacity. These data are the first to suggest that a combination of Tm and TMSsc across the injury site can be an effective treatment modality for C-SCI-induced spasticity and gait impairments and provided a pre-clinical demonstration for feasibility and efficacy of early TMSsc intervention after C-SCI.

Modification of spasticity by transcutaneous spinal cord stimulation in individuals with incomplete spinal cord injury

CONTEXT/OBJECTIVE

To examine the effects of transcutaneous spinal cord stimulation (tSCS) on lower-limb spasticity.

DESIGN

Interventional pilot study to produce preliminary data.

SETTING

Department of Physical Medicine and Rehabilitation, Wilhelminenspital, Vienna, Austria.

PARTICIPANTS

Three subjects with chronic motor-incomplete spinal cord injury (SCI) who could walk ≥10 m.

INTERVENTIONS

Two interconnected stimulating skin electrodes (Ø 5 cm) were placed paraspinally at the T11/T12 vertebral levels, and two rectangular electrodes (8 × 13 cm) on the abdomen for the reference. Biphasic 2 ms-width pulses were delivered at 50 Hz for 30 minutes at intensities producing paraesthesias but no motor responses in the lower limbs.

OUTCOME MEASURES

The Wartenberg pendulum test and neurological recordings of surface-electromyography (EMG) were used to assess effects on exaggerated reflex excitability. Non-functional co-activation during volitional movement was evaluated. The timed 10-m walk test provided measures of clinical function.

RESULTS

The index of spasticity derived from the pendulum test changed from 0.8 ± 0.4 pre- to 0.9 ± 0.3 post-stimulation, with an improvement in the subject with the lowest pre-stimulation index. Exaggerated reflex responsiveness was decreased after tSCS across all subjects, with the most profound effect on passive lower-limb movement (pre- to post-tSCS EMG ratio: 0.2 ± 0.1), as was non-functional co-activation during voluntary movement. Gait speed values increased in two subjects by 39%.

CONCLUSION

These preliminary results suggest that tSCS, similar to epidurally delivered stimulation, may be used for spasticity control, without negatively impacting residual motor control in incomplete SCI. Further study in a larger population is warranted.

Motor and gait improvement in patients with incomplete spinal cord injury induced by high-frequency repetitive transcranial magnetic stimulation

OBJECTIVE

To assess the effect of high-frequency repetitive transcranial magnetic stimulation (rTMS) on lower extremities motor score (LEMS) and gait in patients with motor incomplete spinal cord injury (SCI).

METHOD

The prospective longitudinal randomized, double-blind study assessed 17 SCI patients ASIA D. We assessed LEMS, modified Ashworth Scale (MAS), 10-m walking test (10MWT), Walking Index for SCI (WISCI II) scale, step length, cadence, and Timed Up and Go (TUG) test at baseline, after the last of 15 daily sessions of rTMS and 2 weeks later. Patients were randomized to active rTMS or sham stimulation. Three patients from the initial group of 10 randomized to sham stimulation entered the active rTMS group after a 3-week washout period. Therefore a total of 10 patients completed each study condition. Both groups were homogeneous for age, gender, time since injury, etiology, and ASIA scale. Active rTMS consisted of 15 days of daily sessions of 20 trains of 40 pulses at 20 Hz and an intensity of 90% of resting motor threshold. rTMS was applied with a double cone coil to the leg motor area.

RESULTS

There was a significant improvement in LEMS in the active group (28.4 at baseline and 33.2 after stimulation; P = .004) but not in the sham group (29.6 at baseline, and 30.9 after stimulation; P = .6). The active group also showed significant improvements in the MAS, 10MWT, cadence, step length, and TUG, and these improvements were maintained 2 weeks later. Following sham stimulation, significant improvement was found only for step length and TUG. No significant changes were observed in the WISCI II scale in either group.

CONCLUSION

High-frequency rTMS over the leg motor area can improve LEMS, spasticity, and gait in patients with motor incomplete SCI.

Modulation of thermal somatosensory thresholds within local and remote spinal dermatomes following cervical repetitive magnetic stimulation

BACKGROUND

Repetitive magnetic stimulation (rMS) modulates thermal somatosensory function at both low (0.2-1.0Hz) and high (5.0-20.0Hz) frequencies within the conditioned dermatome. However the effects of 1Hz and 20Hz cervical (C6-C7) rMS on thermosensory thresholds and contact heat evoked potentials (CHEPs) tested within local and remote spinal dermatomes are not known.

METHODS

Thirty healthy subjects participated in the study. Warm and cold detection threshold, heat and cold pain thresholds, and Cz/Fz CHEPs were evaluated within the C6, T10 and extrasegmental V3 control dermatome, before and after random assignment of subjects to sham, 1 or 20Hz C6-C7 rMS.

RESULTS

Following both 1 and 20Hz cervical rMS, warm detection threshold increased within the local C6 dermatome. Furthermore 1Hz cervical rMS increased warm detection threshold within the remote T10 dermatome, but not within the V3-trigeminal control area. Cervical rMS failed to modulate cold detection threshold, heat and cold pain threshold or Cz/Fz CHEP amplitude from the dermatomal test sites.

CONCLUSION

Both 1 and 20Hz cervical rMS modulated warm detection threshold within the locally conditioned C6 dermatome. The concomitant increase in warm detection threshold within the T10 dermatome following 1Hz rMS provides evidence for remote neuromodulation of thermosensory function via intraspinal control mechanisms.

The physiological basis of neurorehabilitation--locomotor training after spinal cord injury

Advances in our understanding of the physiological basis of locomotion enable us to optimize the neurorehabilitation of patients with lesions to the central nervous system, such as stroke or spinal cord injury (SCI). It is generally accepted, based on work in animal models, that spinal neuronal machinery can produce a stepping-like output. In both incomplete and complete SCI subjects spinal locomotor circuitries can be activated by functional training which provides appropriate afferent feedback. In motor complete SCI subjects, however, motor functions caudal to the spinal cord lesion are no longer used resulting in neuronal dysfunction. In contrast, in subjects with an incomplete SCI such training paradigms can lead to improved locomotor ability. Appropriate functional training involves the facilitation and assistance of stepping-like movements with the subjects’ legs and body weight support as far as is required. In severely affected subjects standardized assisted locomotor training is provided by body weight supported treadmill training with leg movements either manually assisted or moved by a driven gait orthosis. Load- and hip-joint related afferent input is of crucial importance during locomotor training as it leads to appropriate leg muscle activation and thus increases the efficacy of the rehabilitative training. Successful recovery of locomotion after SCI relies on the ability of spinal locomotor circuitries to utilize specific multisensory information to generate a locomotor pattern. It seems that a critical combination of sensory cues is required to generate and improve locomotor patterns after SCI. In addition to functional locomotor training there are numbers of other promising experimental approaches, such as tonic epidural electrical or magnetic stimulation of the spinal cord, which both promote locomotor permissive states that lead to a coordinated locomotor output. Therefore, a combination of functional training and activation of spinal locomotor circuitries, for example by epidural/flexor reflex electrical stimulation or drug application (e.g. noradrenergic agonists), might constitute an effective strategy to promote neuroplasticity after SCI in the future.

Peripheral magnetic stimulation to decrease spasticity in cerebral palsy

Muscle spasticity in pediatric cerebral palsy limits movement and disrupts motor performance, thus its reduction is important in rehabilitation to optimize functional motor development. Our pilot study used repetitive peripheral magnetic stimulation, because this emerging technology influences spinal and cerebral synaptic transmission, and its antispastic effects were reported in adult neurologic populations. We tested whether five sessions of tibial and common peroneal nerve stimulation exerted acute and long-term effects on spasticity of the ankle plantar flexor muscles in five spastic diparetic children (mean age, 8 years and 3 months; standard deviation, 1 year and 10 months). Muscle resistance to fast stretching was measured with a manual dynamometer as a spasticity indicator. A progressive decrease was observed for the more impaired leg, reaching significance at the third session. This sustained reduction of spasticity may reflect that the peripheral stimulation improved the controls over the spinal circuitry. It thus suggests that a massive stimulation-induced recruitment of sensory afferents may be able to influence central nervous system plasticity in pediatric cerebral palsy.

[Cerebral reorganization in chronic low back pain and neurostimulation to improve motor control]

Chronic recurrent pain results in brain reorganization for cortical sensory and motor representation of muscles. This review supports the hypothesis that maladaptive plasticity in chronic low back pain patients could be associated with disorders of volitional activation of trunk/pelvis muscles and alterations of their anticipatory motor patterns for postural control. This is actually observed for the transversus abdominis muscle, an abdominal muscle that stabilizes the lumbosacral spine against external and internal postural perturbations. Indeed, voluntary activation of this muscle is more difficult in low back pain and a posterolateral translation of its cortical motor representation is observed in association with a delay of its anticipatory activation (usually observed in any focal limb movement). During physiotherapy, low back pain patients are trained to hollowing for contracting the transversus abdominis muscle, which normalizes both activation delays and cortical motor representation. This motor rehabilitation could be potentiated by peripheral repetitive magnetic stimulation directly over the nerves/muscles. This review introduces the magnetic stimulation technique and proposes to combine peripheral theta-burst stimulation to conventional therapy for increasing the functional gain. This may facilitate the activation of sensory afferents and modulate cortical plasticity to improve (or even re-activate) the sensorimotor control and possibly influence pain. Peripheral magnetic stimulation as an ancillary treatment adjuvant for promoting motor control in low back pain might also be relevant in any other neurological or musculoskeletal disorder with underlying maladaptive brain reorganization.

Reduction of spasticity with repetitive transcranial magnetic stimulation in patients with spinal cord injury

OBJECTIVE

Spasticity with increased tone and spasms is frequent in patients after spinal cord injury (SCI). Damage to descending corticospinal pathways that normally exert spinal segmental control is thought to play an important causal role in spasticity. The authors examined whether the modulation of excitability of the primary motor cortex with high-frequency repetitive transcranial magnetic stimulation (rTMS) could modify lower limb spasticity in patients with incomplete SCI.

METHODS

Patients were assessed by the Modified Ashworth Scale, Visual Analogue Scale, and the Spinal Cord Injury Spasticity Evaluation Tool (SCI-SET) and neurophysiologically with measures of corticospinal and segmental excitability by the H(max)/M(max), T reflex, and withdrawal reflex. Fifteen patients received 5 days of daily sessions of active (n = 14) or sham (n = 7) rTMS to the leg motor area (20 trains of 40 pulses at 20 Hz and an intensity of 90% of resting motor threshold for the biceps brachii muscle).

RESULT

A significant clinical improvement in lower limb spasticity was observed in patients following active rTMS but not after sham stimulation.This improvement lasted for at least 1 week following the intervention. Neurophysiological studies did not change.

CONCLUSIONS

High-frequency rTMS over the leg motor area can improve aspects of spasticity in patients with incomplete SCI.

Peripheral repetitive magnetic stimulation induces intracortical inhibition in healthy subjects

OBJECTIVE

Repetitive magnetic stimulation (rMS) is mainly used in transcranial applications. Only a few works have described its potential peripheral use. The aim of this investigation was to determine if conditioning peripheral (paravertebral) rMS of the cervical nerve roots in a group of healthy subjects induces changes in motor cortical excitability.

METHODS

This was measured by means of motor evoked potentials (MEP), motor recruitment curves (RC), intracortical inhibition (ICI) and facilitation, as well as the cortical silent period (CSP) before and after repetitive stimulation. rMS was carried out by applying ten series of stimulation at 120% of resting motor threshold, each lasting 10 seconds with a frequency of 20 Hz. The nerve roots (C7/C8) of the right hand innervating the target muscles (the first dorsal interosseous) were systematically stimulated.

RESULTS

This conditioning rMS caused a significantly longer CSP (p=0.001), increased MEP amplitudes (with a tendency to significance of p=0.06) and raised ICI (p<0.05). These changes were absent on the contralateral side, as well as in the course of RC. In conclusion, previously published results that described a prolonged CSP and increased MEP amplitudes led us to speculate that conditioning peripheral rMS is, like electrical stimulation, capable of influencing motor cortical excitability.

SIGNIFICANCE

rMS might therefore be used in rehabilitative strategies for spasticity, pain or central paresis.

Repetitive transcranial magnetic stimulation of the motor cortex ameliorates spasticity in multiple sclerosis

OBJECTIVE

To investigate whether repetitive transcranial magnetic stimulation (rTMS) can modify spasticity.

METHODS

We used high-frequency (5 Hz) and low-frequency (1 Hz) rTMS protocols in 19 remitting patients with relapsing-remitting multiple sclerosis and lower limb spasticity.

RESULTS

A single session of 1 Hz rTMS over the leg primary motor cortex increased H/M amplitude ratio of the soleus H reflex, a reliable neurophysiologic measure of stretch reflex. Five hertz rTMS decreased H/M amplitude ratio of the soleus H reflex and increased corticospinal excitability. Single sessions did not induce any effect on spasticity. A significant improvement of lower limb spasticity was observed when rTMS applications were repeated during a 2-week period. Clinical improvement was long-lasting (at least 7 days after the end of treatment) when the patients underwent 5 Hz rTMS treatment during a 2-week protocol. No effect was obtained after a 2-week sham stimulation.

CONCLUSIONS

Repetitive transcranial magnetic stimulation may improve spasticity in multiple sclerosis.

Differential activation and block of peripheral nerve fibers by magnetic fields

The ability to noninvasively and reversibly block conduction in peripheral nerves would have several clinical applications. As an initial step in this direction, we investigated the possibility of magnetically generating and differentially blocking activity in mammalian peripheral nerve fibers in vitro. Compound action potentials at each end of individual explanted phrenic nerves were recorded in response to currents induced at the midpoint of the nerve with an externally placed magnetic coil. Current in the coil was then reversed and the recordings repeated. In all cases, the area under the compound action potential on the virtual anode side of the magnetic stimulus was reduced (mean of 18.2 +/- 8.8%) in comparison to the area on the virtual cathode side. This indicates that peripheral nerve activity can be differentially induced by magnetic stimulation. Extension of this effect to the point of generating unidirectional action potentials in vivo may prove clinically useful in a number of contexts, such as reducing contractures secondary to spasticity and generating magnetically induced anesthesia in limbs. Further investigations of this effect seem warranted.

Lumbar repetitive magnetic stimulation reduces spastic tone increase of the lower limbs

STUDY DESIGN

Comparison of spinal lesion subjects and normal subjects.

OBJECTIVE

To investigate the effects of a paravertebral repetitive magnetic stimulation on spastic tone increase of the lower limbs.

SETTING

Munich, Germany.

METHODS

We compared the effects in 15 patients with different spinal lesions and in 16 healthy subjects. The spastic tone increase was evaluated clinically with the Ashworth scale and apparatively with the pendulum test, both at fixed times before and after stimulation. Unilateral stimulation was applied to the lumbar nerve roots L3 and L4 of the clinically more spastic leg.

RESULTS

The spastic tone decreased significantly in the interval between 4 and 24 h after stimulation. This effect was slightly more pronounced in the contralateral extremity. Furthermore, the stimulation motor threshold of the patients was significantly raised.

CONCLUSION

Repetitive magnetic unilateral stimulation has a positive effect on spastic tone increase due to spinal lesions, causing a decrease that lasts for about 1 day not only on the ipsilateral but also on the contralateral side.

Transcranial magnetic stimulation in the treatment of mood disorder: a review and comparison with electroconvulsive therapy

OBJECTIVE

To review repetitive transcranial magnetic stimulation (rTMS) as a mode of therapy for depression.

METHOD

The following aspects of rTMS were reviewed and compared with electroconvulsive therapy (ECT): history, basic principles, technical considerations, possible mode of action, safety, adverse effects, and effects on mood in both healthy individuals and those suffering from bipolar disorder (BD) or depression.

RESULTS

rTMS may selectively increase or decrease neuronal activity over discrete brain regions. As a result of this focused intervention with TMS, the potential for unwanted side effects is substantially reduced, compared with ECT. In open trials, rTMS and ECT are reported to be equally efficacious for patients having depression without psychosis, but the therapeutic benefits reported in double-blind sham-rTMS controlled trials are more modest.

CONCLUSION

The antidepressant and antimanic effects of rTMS depend on technical considerations such as stimulus frequency, intensity, and magnetic coil placement, which may not yet be optimized. Biological heterogeneity among the patients treated with rTMS may also contribute to differing efficacy across clinical trials. rTMS may possess tremendous potential as a treatment for mood disorder, but this has not yet been realized. rTMS must still be regarded as an experimental intervention requiring further refinement.