Magnetic coil stimulation of the spinal cord in the dog. Effect of removal of bony structure on eddy current

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.

High-intensity laser therapy versus pulsed electromagnetic field in the treatment of primary dysmenorrhea

[Purpose] To determine the efficacy of high intensity laser therapy (HILT) versus pulsed electromagnetic field (PEMF) in the treatment of primary dysmenorrhea. [Subjects and Methods] This was a randomized clinical trial that included 52 girls diagnosed with primary dysmenorrhea and who were assigned randomly into two groups of equal numbers. The treatment was three sessions every cycle for three consecutive cycles where group (A) included those participants treated with HILT 15 min/session and group (B) those who were treated with PEMF 30 min/session. All patients were evaluated before starting the treatment as well as after the end of treatment by present pain intensity scale and the prostaglandin level in blood and pain relief scale at the end of treatment for both groups. [Results] The results showed a significant decrease in the severity of pain, statistically significant decrease in prostaglandin level in blood, and a statistically significant pain alleviation in both groups. With comparison between both groups there was a statistically significant decrease in the severity of pain, significant decrease in the blood levels of PGF2α, in group (A) than group (B). [Conclusion] Both HILT and PEMF are effective in the treatment of primary dysmenorrhea with HILT being superior to PEMF.

Repetitive spinal electromagnetic stimulation opens a window of synaptic plasticity in damaged spinal cord: role of NMDA receptors

As we reported previously, propagation of action potentials through surviving axons is impaired dramatically, resulting in reduced transmission to lumbar motoneurons after midthoracic lateral hemisection (HX) in rats. The aim of the present study was to evoke action potentials through the spared fibers using noninvasive electromagnetic stimulation (EMS) over intact T2 vertebrae in an attempt to activate synaptic inputs to lumbar motoneurons and thus to enhance plasticity of spinal neural circuits after HX. We found that EMS was able to activate synaptic inputs to lumbar motoneurons and motor-evoked potentials (MEP) in hindlimb muscles in adult anesthetized rats. Amplitude of MEP was attenuated in parallel with the decline of responses recorded from the motoneuron pool after HX. Repetitive EMS (50 min, 0.2 Hz) facilitated the amplitudes of responses elicited by electric stimulation of lateral white matter or dorsal corticospinal tracts in HX rats. Facilitation sustained for at least 1.5 h after termination of EMS. The N-methyl-d-aspartate (NMDA) receptor blocker MK-801, injected intraspinally close to the recording electrode prior to EMS, did not alter these responses but blocked the EMS-induced facilitation, suggesting that activation of NMDA receptors is required to initiate an EMS-evoked increase. When MK-801 was administered after EMS-induced facilitation was established, it induced depression of these elevated responses. Results suggest that repetitive EMS over intact vertebrae could be used as a therapeutic approach to open a window of synaptic plasticity after incomplete midthoracic injuries, i.e., to activate NMDA receptors in the lumbar motoneuron pool at synaptic inputs and to strengthen transmission in damaged spinal cord.

Transcranial magnetic stimulation: review of the technique, basic principles and applications

Transcranial magnetic stimulation is rapidly developing as a powerful, non-invasive tool for studying the descending motor tracts in humans. The applications of the test in animals are for the moment restricted to small animals. However, this non-invasive, sensitive and painless technique appears promising as a test of motor tract function in horses where the neurological examination is mainly restricted to clinical evaluation and some ancillary tests, such as radiography, cerebrospinal fluid analysis and electromyography. In this review, we want to discuss the history, basic principles, technique and applications of transcranial magnetic stimulation in humans and small animals and indicate the possibilities for its use in horses. Since the great portion of this review is based on human studies, it is worthwhile to mention that the reports being described are from humans unless otherwise specified.

Functional magnetic stimulation of expiratory muscles: a noninvasive and new method for restoring cough

The purpose of this study was to assess the effectiveness of functional magnetic stimulation (FMS) for producing expiratory function in normal human subjects. Twelve able-bodied normal subjects were recruited for this study. FMS of the expiratory muscles was performed by using a magnetic stimulator and placing the magnetic coil along the lower thoracic spine. Results showed that peak expired pressure, volume, and flow rate generated by FMS at the end of normal inspiration (102.5 +/- 13.62 cmH2O, 1.6 +/- 0.16 liters, and 4.8 +/- 0.35 l/s, respectively) were comparable to their voluntary maximal levels (P > 0.1). The optimal coil placement was between T7 and T11, and the optimal stimulation parameters were a frequency of 25 Hz and 70-80% of maximal intensity. We conclude that 1) FMS of the lower thoracic nerves in normal subjects resulted in a significant expiratory function comparable to their voluntary maximum; 2) FMS was noninvasive and was well tolerated by all subjects; and 3) FMS may be useful to produce cough in patients in critical care or perioperative settings, or in patients with neurological disorders.

Magnetic stimulation of the lumbosacral vertebral column in children: normal values and possible sites of stimulation

We describe a technique of lumbosacral magnetic stimulation (MS) using an 8-shaped coil in 44 normal children and 7 normal adults on the lower limb muscles. In most child subjects and some adult subjects, we observed two peaks in amplitude of the motor evoked potential (MEP) following MS when the coil was moved caudally from Th8 to S2. The rostral peaks of MEP were elicited at L1/2, and the caudal peaks were elicited below L3. Rostral peak amplitudes were considerably higher in younger children than in adolescents and adults. MEP latencies tended to decrease as the coil was moved from Th11 to L4/5, and were almost constant at caudal to L4/5 in most child subjects, especially in younger children. Comparison of MEP latencies with the peripheral motor conduction times by the F technique suggests that the proximal sites of excitation of the nerve root are 0.0-0.6 ms conduction times distal to the motoneuron, while the distal sites of excitation are 2.1-2.9 ms conduction times distal to the motoneuron. We conclude that performing MS using the 8-shaped coil enables us to excite the nerve roots near the motoneuron as well as those near the intervertebral foramen, and that MEPs are elicited more easily in younger children than in adolescents and adults.