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Static Magnetic Fields and PEMF
Transcranial Magnetic Stimulation
Complementary therapies for neuropathic and neuralgic pain: systematic review.
Pittler MH, Ernst E.
Complementary Medicine, Peninsula Medical School, Universities of Exeter and Plymouth, Exeter, UK.
OBJECTIVE: To assess the evidence from rigorous clinical trials,
systematic reviews, and meta-analyses of complementary and alternative
therapies for treating neuropathic and neuralgic pain.
METHODS: Systematic searches were carried out in the databases
Medline, Embase, Amed, Scopus, the Cochrane Database of Systematic
Reviews, Natural Standard, and the Natural Medicines Comprehensive
Database. Each database was searched from its respective inception until
March 2006. To be included, trials were required to state that they
were randomized. Systematic reviews and meta-analyses were included if
based on the results of randomized trials. No language restrictions were
imposed.
RESULTS: Five relevant systematic reviews and meta-analyses and 15
additional trials met the inclusion criteria and were reviewed. Data on
the following complementary and alternative medicine treatments were
identified: acupuncture, electrostimulation, herbal medicine, magnets,
dietary supplements, imagery, and spiritual healing.
CONCLUSIONS: On the basis of our findings, the evidence is not fully
convincing for most complementary and alternative medicine modalities in
relieving neuropathic or neuralgic pain. However, for topically applied
capsaicin there is evidence of effectiveness beyond placebo. The
evidence can be classified as encouraging and warrants further study
for cannabis extract, magnets, carnitine, and electrostimulation.
The Clinical Journal of Pain. 2008 October. 24 (8):731-3. PMID: 18806539
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Peripheral neuropathy: pathogenic mechanisms and alternative therapies.
Head KA.
Thorne Research, Inc., PO Box 25, Dover, ID 83825, USA.
Peripheral neuropathy (PN), associated with diabetes, neurotoxic
chemotherapy, human immunodeficiency virus (HIV)/antiretroviral drugs,
alcoholism, nutrient deficiencies, heavy metal toxicity, and other
etiologies, results in significant morbidity.
Conventional pain medications primarily mask symptoms and have
significant side effects and addiction profiles. However, a widening
body of research indicates alternative medicine may offer significant
benefit to this patient population.
Alpha-lipoic acid, acetyl-L-carnitine, benfotiamine, methylcobalamin,
and topical capsaicin are among the most well-researched alternative
options for the treatment of PN. Other potential nutrient or botanical
therapies include vitamin E, glutathione, folate, pyridoxine, biotin,
myo-inositol, omega-3 and -6 fatty acids, L-arginine, L-glutamine,
taurine, N-acetylcysteine, zinc, magnesium, chromium, and St. John's
wort.
In the realm of physical medicine, acupuncture, magnetic therapy, and yoga have been found to provide benefit. New cutting-edge conventional therapies, including dual-action peptides, may also hold promise.
Head KA (December 2006). "Peripheral neuropathy: pathogenic mechanisms and alternative therapies." Alternative Medicine Review: A Journal of Clinical Therapeutic. 11(4):294-329. PMID: 17176168
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Static magnetic field influence on rat brain function detected by heart rate monitoring.
Veliks V, Ceihnere E, Svikis I, Aivars J.
Faculty of Biology, University of Latvia, Riga, Latvia.
The aim of the present study was to identify the effects of a static
magnetic field (SMF) on rat brain structures that control autonomic
functions, specifically heart rate and heart rhythmicity. The
experiments were carried out on 44 male Wistar rats under
ketamine-xylazine anesthesia. SMF was induced using samarium-cobalt
fused magnets (20 x 20 x 10 mm in size) placed bitemporally. Magnetic
induction intensity was 100 mT on the surface of the head. Duration of
magnetic field application was 15 min. An electrocardiogram was recorded
from limb lead II, and both heart rate (average duration of cardiac
cycles) and heart rhythmicity were analyzed before and after SMF
application. SMF evoked changes in both heart rate and rhythm in 80% of
the animals; the predominant effects were bradycardia and disappearance
of respiratory sinus arrhythmia. However, the effectiveness of SMF in
large measure depends on both functional peculiarities and functional
activities of brain autonomic centers. Bioelectromagnetics 25:211-215,
2004. Copyright 2004 Wiley-Liss, Inc.
Bioelectromagnetics. 2004 Apr;25(3):211-5.
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Pulsed magnetic field therapy in refractory neuropathic pain
secondary to peripheral neuropathy: electrodiagnostic parameters - pilot
study.
Weintraub MI, Cole SP.
New York Medical College, Briarcliff Manor, New York 10510, USA.
CONTEXT: Neuropathic pain (NP) from peripheral neuropathy (PN) arises
from ectopic firing of unmyelinated C-fibers with accumulation of
sodium and calcium channels. Because pulsed electromagnetic fields
(PEMF) safely induce extremely low frequency (ELF) quasirectangular
currents that can depolarize, repolarize, and hyperpolarize neurons, it
was hypothesized that directing this energy into the sole of one foot
could potentially modulate neuropathic pain.
OBJECTIVE: To determine if 9 consecutive 1-h treatments in
physician's office (excluding weekends) of a pulsed signal therapy can
reduce NP scores in refractory feet with PN.
DESIGN/SETTING/PATIENTS: 24 consecutive patients with refractory and
symptomatic PN from diabetes, chronic inflammatory demyelinating
polyneuropathy (CIDP), pernicious anemia, mercury poisoning,
paraneoplastic syndrome, tarsal tunnel, and idiopathic sensory
neuropathy were enrolled in this nonplacebo pilot study. The most
symptomatic foot received therapy. Primary endpoints were comparison of
VAS scores at the end of 9 days and the end of 30 days follow-up
compared to baseline pain scores. Additionally, Patients' Global
Impression of Change (PGIC) questionnaire was tabulated describing
response to treatment. Subgroup analysis of nerve conduction scores,
quantified sensory testing (QST), and serial examination changes were
also tabulated. Subgroup classification of pain (Serlin) was utilized to
determine if there were disproportionate responses.
INTERVENTION: Noninvasive pulsed signal therapy generates a
unidirectional quasirectangular waveform with strength about 20 gauss
and a frequency about 30 Hz into the soles of the feet for 9 consecutive
1-h treatments (excluding weekends). The most symptomatic foot of each
patient was treated.
RESULTS: All 24 feet completed 9 days of treatment. 15/24 completed
follow-up (62%) with mean pain scores decreasing 21% from baseline to
end of treatment (P=0.19) but with 49% reduction of pain scores from
baseline to end of follow-up (P<0.01). Of this group, self-reported
PGIC was improved 67% (n=10) and no change was 33% (n=5). An
intent-to-treat analysis based on all 24 feet demonstrated a 19%
reduction in pain scores from baseline to end of treatment (P=0.10) and a
37% decrease from baseline to end of follow-up (P<0.01). Subgroup
analysis revealed 5 patients with mild pain with nonsignificant
reduction at end of follow-up. Of the 19 feet with moderate to severe
pain, there was a 28% reduction from baseline to end of treatment
(P<0.05) and a 39% decrease from baseline to end of follow-up
(P<0.01). Benefit was better in those patients with axonal changes
and advanced CPT baseline scores. The clinical examination did not
change. There were no adverse events or safety issues.
CONCLUSIONS: These pilot data demonstrate that directing PEMF to
refractory feet can provide unexpected shortterm analgesic effects in
more than 50% of individuals. The role of placebo is not known and was
not tested. The precise mechanism is unclear yet suggests that severe
and advanced cases are more magnetically sensitive. Future studies are
needed with randomized placebo-controlled design and longer treatment
periods.
Neurorehabil Neural Repair. 2004 Mar;18(1):42-6.
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Attention to features precedes attention to locations in visual search: evidence from electromagnetic brain responses in humans.
Hopf JM, Boelmans K, Schoenfeld MA, Luck SJ, Heinze HJ.
Department of Neurology II, Otto-von-Guericke-University, D-39120 Magdeburg, Germany. jens-max.hopf@medizin.uni-magdeburg.de
Single-unit recordings in macaque extrastriate cortex have shown that
attentional selection of nonspatial features can operate in a
location-independent manner. Here, we investigated analogous neural
correlates at the neural population level in human observers by using
simultaneous event-related potential (ERP) and event-related magnetic
field (ERMF) recordings. The goals were to determine (1) whether
task-relevant features are selected before attention is allocated to the
location of the target, and (2) whether this selection reflects the
locations of the relevant features. A visual search task was used in
which the spatial distribution of nontarget items with attended feature
values was varied independently of the location of the target. The
presence of task-relevant features in a given location led to a change
in ERP/ERMF activity beginning approximately 140 msec after stimulus
onset, with a neural origin in the ventral occipito-temporal cortex.
This effect was independent of the location of the actual target. This
effect was followed by lateralized activity reflecting the allocation of
attention to the location of the target (the well known N2pc
component), which began at approximately 170 msec poststimulus. Current
source localization indicated that the allocation of attention to the
location of the target originated in more anterior regions of
occipito-temporal cortex anterior than the feature-related effects.
These findings suggest that target detection in visual search begins
with the detection of task-relevant features, which then allows spatial
attention to be allocated to the location of a likely target, which in
turn allows the target to be positively identified.
J Neurosci. 2004 Feb 25;24(8):1822-32.
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Identifiable neurons inhibited by Earth-strength magnetic stimuli in the mollusc Tritonia diomedea.
Wang JH, Cain SD, Lohmann KJ.
Department of Biology, University of North Carolina, Chapel Hill, NC
27599-3280, USA Friday Harbor Laboratories, University of Washington,
Friday Harbor, Washington 98250, USA.
Diverse animals use the Earth's magnetic field as an orientation cue,
but little is known about the sensory, processing and motor elements of
the neural circuitry underlying magnetic orientation behavior. The
marine mollusc Tritonia diomedea has both a magnetic compass sense and a
simple nervous system accessible to electrophysiological analysis.
Previous studies have revealed that four identifiable neurons, known as
LPd5, RPd5, LPd6 and RPd6, respond with enhanced electrical activity to
changes in Earth-strength magnetic fields. Here we report that two
additional neurons, LPd7 and RPd7, are inhibited by magnetic stimuli.
Cobalt fills of the Pd7 neurons indicated that two prominent neurites
emerge from the soma and project to the periphery through the
ipsilateral cerebral nerves CeN6 and CeN3; in some cases, a third
neurite was visible in CeN2. The nerves extend to the anterior region of
the animal where they innervate the lateral body walls, oral veil and
mouth region. Action potentials in the Pd7 neurons propagate from the
central ganglia toward the periphery. Thus, the Pd7 cells have
characteristics of efferent neurons. The precise function of these cells
during magnetic orientation behavior, however, remains to be
determined.
J Exp Biol. 2004 Feb 22;207(Pt 6):1043-9.
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Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity.
Krasteva VT, Papazov SP, Daskalov IK.
BACKGROUND: Peripheral nerves are situated in a highly
non-homogeneous environment, including muscles, bones, blood vessels,
etc. Time-varying magnetic field stimulation of the median and ulnar
nerves in the carpal region is studied, with special consideration of
the influence of non-homogeneities.
METHOD: A detailed three-dimensional finite element model (FEM) of
the anatomy of the wrist region was built to assess the induced currents
distribution by external magnetic stimulation. The electromagnetic
field distribution in the non-homogeneous domain was defined as an
internal Dirichlet problem using the finite element method. The boundary
conditions were obtained by analysis of the vector potential field
excited by external current-driven coils.
RESULTS: The results include evaluation and graphical representation
of the induced current field distribution at various stimulation coil
positions. Comparative study for the real non-homogeneous structure with
anisotropic conductivities of the tissues and a mock homogeneous media
is also presented. The possibility of achieving selective stimulation of
either of the two nerves is assessed.
CONCLUSION: The model developed could be useful in theoretical
prediction of the current distribution in the nerves during diagnostic
stimulation and therapeutic procedures involving electromagnetic
excitation. The errors in applying homogeneous domain modeling rather
than real non-homogeneous biological structures are demonstrated. The
practical implications of the applied approach are valid for any
arbitrary weakly conductive medium.
Biomed Eng Online. 2003 Dec 23; 2(1): 19.
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Control of orientation of rat Schwann cells using an 8-T static magnetic field.
Eguchi Y, Ogiue-Ikeda M, Ueno S.
Department of Biomedical Engineering, Graduate School of Medicine,
University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Schwann cells aid in neuronal regeneration in the
peripheral nervous system via guiding the regrowth of axons. In this
study, we investigated the magnetic orientation of Schwann cells, and of
a mixture of Schwann cells and collagen, after an 8-tesla magnetic
field exposure. We obtained cultured Schwann cells from dissected
sciatic nerves of neonatal rats. After 60 h of magnetic field exposure,
Schwann cells oriented parallel to the magnetic fields. In contrast, the
mixture of Schwann cells and collagen, Schwann cells oriented in the
direction perpendicular to the magnetic field after 2 h of magnetic
field exposure. In this case, Schwann cells aligned along the collagen
fiber oriented by magnetic fields. The magnetic control of Schwann cell alignment is useful in medical engineering applications such as nerve regeneration.
Neurosci Lett. 2003 Nov 13;351(2):130-2.
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Use of low-power electromagnetic therapy in diabetic polyneuropathy.
Chebotar'ova LL, Chebotar'ov HIe.
The clinical-electroneuromyography investigations were performed for
objective evaluation of low-power electromagnetic therapy effectiveness
in 12 patients with diabetic polyneuropaties. It is established that
combination of low-power electromagnetic therapy using "ANET-UHF",
"ANET-SHF" apparatus (Ukraine) and low-power variable magnetic field
using AMT apparatus (Ukraine) give the stable positive effects. The
positive changes were confirmed by following: the decrease of
neurological deficit and required insulin daily dose, nerve conduction
velocity increase, increase of the muscle compound action potentials (muscle power) and peripheral outflow in some patients.
Fiziol Zh. 2003;49(2):85-90.
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Neuronal ion channels and their sensitivity to extremely low frequency weak electric field effects.
Mathie A, Kennard LE, Veale EL.
Biophysics Section, Department of Biological Sciences, Imperial College London, London SW7 2AZ, UK. a.mathie@imperial.ac.uk
Neuronal ion channels are gated pores whose opening and closing is
usually regulated by factors such as voltage or ligands. They are often
selectively permeable to ions such as sodium, potassium or calcium.
Rapid signalling in neurons requires fast voltage sensitive mechanisms
for closing and opening the pore. Anything that interferes with the
membrane voltage can alter channel gating and comparatively small
changes in the gating properties of a channel can have profound effects.
Extremely low frequency electrical or magnetic fields are thought to
produce, at most, microvolt changes in neuronal membrane potential. At
first sight, such changes in membrane potential seem orders of magnitude
too small to significantly influence neuronal signalling. However, in
the central nervous system, a number of mechanisms exist which amplify
signals. This may allow such small changes in membrane potential to
induce significant physiological effects.
Radiat Prot Dosimetry. 2003; 106(4): 311-6.
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The study of effects of static magnetic field on SP-mRNA in trigeminal ganglion in rats.
Chang X, Qin K, Lu Y.
Faculty of Stomatology, China Medical University, Shenyang 110002, China.
OBJECTIVE: To evaluate the effect of static magnetic field on the expression of SP-mRNA in TG in rats.
METHODS: 44 Wistar rats aged 6-7 weeks were put into static magnetic
field and were sacrificed at 1 h, 2 h, 6 h, 12 h, 24 h, respectively. In
situ hybridization method was used to evaluate the changes of SP-mRNA
expression at different time point.
RESULTS: Many neurons in TG were marked with SP probes in each group,
the expression of SP-mRNA increased remarkably in static magnetic field
group. In this group, the percentage of SP-mRNA positive neurons in TG
increased greatly in 1 h, reached its peak in 2 h, from then on,
decrease of the percentage started slowly but a moderate percentage was
kept until 24 h, which was thought to be enough to maintain orthodontic
tooth movement. The tendency of control group was almost the same with
that of experimental group. The expression of SP-mRNA was higher in
experimental group within 2 h but became lower after 2 h as compared
with control group, this indicated that magnetic field reduced the SP-mRNA expression and exerted restoring effect on trauma. There were significant differences between experimental groups and control group at different time points (P < 0.01).
CONCLUSION: The expression of SP-mRNA in TG in rats increased significantly in static magnetic field.
Hua Xi Kou Qiang Yi Xue Za Zhi. 2003 Jun;21(3):235-7.
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On the applicability of two different stimulation techniques for intra-operative peroneal nerve conduction testing.
Nebelung W, Wissel H, Awiszus F.
Neuromuscular Research Group, Otto-von Guericke-University Magdeburg,
Clinic for Orthopedic Surgery, Germany.
wolfgang.nebelung@medizin.uni-magdeburg.de
Dysfunction of the peroneal nerve is an important complication of knee surgery.
We compared two monitoring procedures of peroneal nerve function during
a standardized operation, a closing wedge high tibial osteotomy. For
two types of stimulation the evoked compound motor unit action
potentials (CMAPs) were recorded on the tibialis anterior muscle. We
used direct perineural electrical stimulation of the common peroneal
nerve distal to the cuff (dCMAPs) after nerve identification in the
surgical field. Additionally, magnetic stimulation of the sacral
plexus proximal to the cuff (pCMAPs) was performed. It was found that
dCMAPs were recorded during almost one hour of tourniquet time whereas
the pCMAPs were blocked after 25-30 min in 9 out of 11 cases.
On the other hand, the CMAP obtained after proximal stimulation
exhibited a latency shift with tourniquet yielding an indicator of
ischaemic changes present beneath and distal to the tourniquet cuff. In
conclusion, different applicabilities of both stimulation techniques
under tourniquet conditions were demonstrated.
J Orthop Res. 2001 Jan;19(1):160-5.
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Threshold and limits of magnetic field action at the presynaptic membrane.
Rosen AD.
Department of Neurology, School of Medicine, State University of New York at Stony Brook 11794-8121.
The relationship of field intensity and exposure duration to the
inhibitory effect of static magnetic fields on presynaptic membrane
function was examined in order to further define the mechanism of action
of these fields. Miniature endplate potentials (MEPPs) were recorded
from the isolated murine neuromuscular junction, maintained at a
temperature of 35.5 degrees C, during exposure to static magnetic fields
of varying duration and intensity. Inhibition of MEPP generation
correlated well with the product of the square of the flux density and
exposure time. At lower product values the relationship was linear with
an absolute flux density threshold of 37.9 mT. Higher product values
were associated with deviation from linearity indicative of a limit on
the extent of inhibition. These findings are consistent with the
hypothesis that static magnetic fields induce a reorientation of
diamagnetic molecular domains within the membrane but with a restriction
on the degree of reorientation imposed by the membrane's cytoskeleton.
Biochim Biophys Acta. 1994 Jul 13;1193(1):62-6.
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Effect of weak, pulsing electromagnetic fields on neural regeneration in the rat.
Ito H, Bassett CA.
The short- and long-term effects of pulsed electromagnetic fields
(PEMFs) on the rate and quality of peripheral nerve regeneration were
studied. High bilateral transections of rat sciatic nerves were
surgically approximated (a 1-mm gap was left) and shielded with a
Silastic sleeve. Animals were exposed to PEMFs for two to 14 weeks after
operation. Three groups of 20 rats each (control rats and rats
undergoing 12- and 24-hour/day PEMF exposure) were killed at two weeks.
Histologically, regenerating axons had penetrated the distal stump
nearly twice as far in the PEMF-exposed animals as in the control
animals. Return of motor function was judged two to 14 weeks after
operation by the load cell-measured, plantar-flexion force produced by
neural stimulation proximal to the transection site. Motor function
returned earlier in experimental rats and to significantly higher load
levels than in control rats. Nerves from animals functioning 12-14 weeks
after operation had less interaxonal collagen, more fiber-containing
axis cylinders, and larger fiber diameters in the PEMF-exposed group
than in the control rats. Histologic and functional data indicate that PEMFs improve the rate and quality of peripheral nerve regeneration in the severed rat sciatic nerve by a factor of approximately two.
Clin Orthop. 1983 Dec;(181):283-90.
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Effects of high-peak pulsed electromagnetic field on the degeneration and regeneration of the common peroneal nerve in rats.
Raji AR, Bowden RE.
Apart from preliminary notices of present work, previous reports of
experimental and clinical trials of the effects of a high-peak pulsed
electromagnetic field (PEMF) on degeneration and regeneration of
peripheral nerves lacked statistical analysis. Therefore, we designed
experiments with standardised operative, histological, cytological and
morphometric techniques to assess the effect of PEMF on lesions of the
common peroneal nerves in paired male rats matched for age,
environmental conditions and level and type of lesion. One of two types
of lesion was induced in the left common peroneal nerve: in 12 pairs of
rats the nerve was crushed just above the knee and in the remaining 12
pairs the nerve was cut and immediately sutured at the same level. The
right common peroneal nerve of each rat served as a control. Animals
received 15 minutes of PEMF produced by a Diapulse machine or sham
treatment daily for periods ranging from three and a half days to eight
weeks after injury. Healthy nerves were unaffected, but after damage
there were statistically significant differences between PEMF treated
and sham treated rats. PEMF accelerated the recovery of injured limbs and the degeneration, regeneration and maturation of myelinated axons;
epineural, perineural and intraneural fibrosis was reduced; and the
luminal cross-sectional area of intraneural vessels increased after both
types of lesion. Findings are discussed and the need for clinical
trials is stressed.
J Bone Joint Surg Br. 1983 Aug;65(4):478-92.
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The effect of stimulus intensity on brain responses evoked by transcranial magnetic stimulation.
Komssi S, Kahkonen S, Ilmoniemi RJ.
BioMag Laboratory, Engineering Centre, Helsinki University Central Hospital, Helsinki, Finland. soile.komssi@hus.fi
To better understand the neuronal effects of transcranial magnetic
stimulation (TMS), we studied how the TMS-evoked brain responses depend
on stimulation intensity. We measured electroencephalographic (EEG)
responses to motor-cortex TMS, estimated the intensity dependence of the
overall brain response, and compared it to a theoretical model for the
intensity dependence of the TMS-evoked neuronal activity. Left and right
motor cortices of seven volunteers were stimulated at intensities of
60, 80, 100, and 120% of the motor threshold (MT). A figure-of-eight
coil (diameter of each loop 4 cm) was used for focal stimulation. EEG
was recorded with 60 scalp electrodes. The intensity of 60% of MT was
sufficient to produce a distinct global mean field amplitude (GMFA)
waveform in all subjects. The GMFA, reflecting the overall brain
response, was composed of four peaks, appearing at 15 +/- 5 msec (Peak
I), 44 +/- 10 msec (II), 102 +/- 18 msec (III), and 185 +/- 13 msec
(IV). The peak amplitudes depended nonlinearly on intensity. This
nonlinearity was most pronounced for Peaks I and II, whose amplitudes
appeared to sample the initial part of the sigmoid-shaped curve modeling
the strength of TMS-evoked neuronal activity. Although the response
amplitude increased with stimulus intensity, scalp distributions of the
potential were relatively similar for the four intensities. The results
imply that TMS is able to evoke measurable brain activity at low
stimulus intensities, probably significantly below 60% of MT. The shape
of the response-stimulus intensity curve may be an indicator of the
activation state of the brain. Copyright 2004 Wiley-Liss, Inc.
Hum Brain Mapp. 2004 Mar;21(3):154-64.
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Repetitive transcranial magnetic stimulation improves open field
locomotor recovery after low but not high thoracic spinal cord
compression-injury in adult rats.
Poirrier AL, Nyssen Y, Scholtes F, Multon S, Rinkin C, Weber G, Bouhy D, Brook G, Franzen R, Schoenen J.
Research Centre for Cellular and Molecular Neurobiology, Neuroanatomy Laboratory, University of Liege, Belgium.
Electromagnetic fields are able to promote axonal regeneration in
vitro and in vivo. Repetitive transcranial magnetic stimulation (rTMS)
is used routinely in neuropsychiatric conditions and as an atraumatic
method to activate descending motor pathways. After spinal cord injury,
these pathways are disconnected from the spinal locomotor generator,
resulting in most of the functional deficit. We have applied daily 10 Hz
rTMS for 8 weeks immediately after an incomplete high (T4-5; n = 5) or
low (T10-11; n = 6) thoracic closed spinal cord compression-injury in
adult rats, using 6 high- and 6 low-lesioned non-stimulated animals as
controls. Functional recovery of hindlimbs was assessed using the BBB
locomotor rating scale. In the control group, the BBB score was
significantly better from the 7th week post-injury in animals lesioned
at T4-5 compared to those lesioned at T10-11. rTMS significantly
improved locomotor recovery in T10-11-injured rats, but not in rats with
a high thoracic injury. In rTMS-treated rats, there was significant
positive correlation between final BBB score and grey matter density of
serotonergic fibres in the spinal segment just caudal to the lesion. We
propose that low thoracic lesions produce a greater functional deficit
because they interfere with the locomotor centre and that rTMS is
beneficial in such lesions because it activates this central pattern
generator, presumably via descending serotonin pathways. The benefits of
rTMS shown here suggest strongly that this non-invasive intervention
strategy merits consideration for clinical trials in human paraplegics
with low spinal cord lesions. Copyright 2003 Wiley-Liss, Inc.
J Neurosci Res. 2004 Jan 15; 75(2): 253-61.
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Acute remapping within the motor system induced by low-frequency repetitive transcranial magnetic stimulation.
Lee L, Siebner HR, Rowe JB, Rizzo V, Rothwell JC, Frackowiak RS, Friston KJ.
Wellcome Department of Imaging Neuroscience, Institute of Neurology,
University College London, London, WC1N 3BG United Kingdom.
llee@fil.ion.ucl.ac.uk
Repetitive transcranial magnetic stimulation (rTMS) of human primary
motor cortex (M1) changes cortical excitability at the site of
stimulation and at distant sites without affecting simple motor
performance. The aim of this study was to explore how rTMS changes
regional excitability and how the motor system compensates for these
changes. Using functional brain imaging, activation was mapped at rest
and during freely selected finger movements after 30 min of 1 Hz rTMS.
rTMS increased synaptic activity in the stimulated left M1 and induced
widespread changes in activity throughout areas engaged by the task. In
particular, movement-related activity in the premotor cortex of the
nonstimulated hemisphere increased after 1 Hz rTMS. Analyses of
effective connectivity confirmed that the stimulated part of M1 became
less responsive to input from premotor and mesial motor areas.
Conversely, after rTMS our results were consistent with increased
coupling between an inferomedial portion of left M1 and anterior motor
areas. These results are important for three reasons. First, they show
changes in motor excitability to central inputs from other cortical
areas (as opposed to peripheral or exogenous inputs used in previous
studies). Second, they suggest that maintenance of task performance may
involve activation of premotor areas contralateral to the site of rTMS,
similar to that seen in stroke patients. Third, changes in motor
activations at the site of rTMS suggest an rTMS-induced remodeling of
motor representations during movement. This remapping may provide a
neural substrate for acute compensatory plasticity of the motor system
in response to focal lesions such as stroke.
J Neurosci. 2003 Jun 15;23(12):5308-18.
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Transcranial magnetic stimulation in neurology.
Kobayashi M, Pascual-Leone A.
Laboratory for Magnetic Brain Stimulation, Department of Neurology,
Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
02215, USA.
Transcranial magnetic stimulation (TMS) is a non-invasive tool for
the electrical stimulation of neural tissue, including cerebral cortex,
spinal roots, and cranial and peripheral nerves. TMS can be applied as
single pulses of stimulation, pairs of stimuli separated by variable
intervals to the same or different brain areas, or as trains of
repetitive stimuli at various frequencies. Single stimuli can depolarise
neurons and evoke measurable effects. Trains of stimuli (repetitive
TMS) can modify excitability of the cerebral cortex at the stimulated
site and also at remote areas along functional anatomical connections.
TMS might provide novel insights into the pathophysiology of the neural
circuitry underlying neurological and psychiatric disorders, be
developed into clinically useful diagnostic and prognostic tests, and
have therapeutic uses in various diseases. This potential is supported
by the available studies, but more work is needed to establish the role
of TMS in clinical neurology.
Lancet Neurol. 2003 Mar;2(3):145-56.
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Low-rate repetitive TMS allays central pain.
Canavero S, Bonicalzi V, Dotta M, Vighetti S, Asteggiano G.
Pain Relief Unit, Department of Neurosciences, Molinette Hospital, Turin, Italy. solara@infinito.it
Only about 50% of central pain patients respond to motor cortex
stimulation in the long run. There is a need for prognostic factors.
Here we show that propofol test and TMS both predict short-term effect
in nine patients with central pain. This may help reduce the number of
failures.
Neurol Res. 2003 Mar;25(2):151-2.
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A clinical study on the magnetic stimulation of the facial nerve.
Yamakawa T, Yoshikawa H, Arai A, Miyazaki T, Ichikawa G.
Department of Otorhinolaryngology, Juntendo University, School of Medicine, Tokyo, Japan.
OBJECTIVES: A clinical study on the usefulness of magnetic
stimulation of the facial nerve, with special attention paid to the
selection of the coil shape and stimulation procedures.
STUDY DESIGN: The subjects consisted of 55 patients with Bell's
palsy, 1 patient with a cerebellopontine angle (CPA) tumor, 1 patient
with multiple sclerosis (MS), and 30 normal subjects. Three types of
coils were used in this study; a 90-mm large single coil, a 40-mm small
single coil, and a 20-mm small double coil.
METHODS: The compound muscle action potentials (CMAPs) and long
latency response were evoked by transcranial magnetic stimulation (TMS)
with a 90-mm large single coil. The 40-mm small single coil was used to
test blink reflex by aiming it at the supraorbital nerve as the target
site. The subcutaneous activation of the infra-auricular facial nerve
was performed with the 20-mm double coil.
RESULTS: The reproducible CMAP and long latency responses were
obtained from normal subjects with TMS. However, responses were observed
only in patients with relatively mild Bell's palsy. The magnetic
stimulation-evoked responses reflected the brainstem function in the
patients with a CPA tumor and MS.
CONCLUSION: Although magnetic stimulation remains inferior to
conventional electric stimulation in some sense and requires further
study, this method is potentially useful because it can stimulate the
facial nerve continuously from the cortex to the periphery and can
effectively evoke responses reflecting the brainstem function.
Laryngoscope. 1999 Mar;109(3):492-7.
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Conditioning effect on the long latency potentials in the lower limb to transcranial magnetic stimulation.
Chen JT, Chen CC, Kao KP, Wu ZA, Liao KK.
Neurology, The Neurological Institute, Veterans General Hospital-Taipei, Taiwan.
OBJECTIVES: We used an electrical conditioning stimulation followed
by transcranial magnetic stimulation (TMS) to facilitate the occurrence
of long latency potentials (LLPs) in order to study the relationship
between primary motor evoked potentials (MEPs) and LLPs in the lower
limbs.
MATERIALS AND METHODS: The study group included 6 healthy subjects, 1
patient with right thalamic infarction, and 3 patients with spinal cord
injuries. The subjects were subjected to electrical conditioning (C)
stimulation delivered to the left big toe at 250 Hz in a train of pulses
of 20 ms duration prior to TMS (T) from 0 to 150 ms at an increment of
10 ms. The surface electromyographic signals were recorded at the
tibialis anterior and gastrocnemius medialis for 400 ms.
RESULTS: The C-T test facilitated both primary MEPs and LLPs with a
pattern similar to the primary MEPs of its antagonist. There was no
facilitation of the primary MEPs or LLPs in the affected limb of
patients with thalamic or spinal cord lesions.
CONCLUSION: At appropriate C-T interval, LLPs could be consistently
provoked by TMS. The LLPs were absent in the patients with thalamic
infarction and spinal cord injuries. It suggests that LLPs might be
provoked through a supraspinal control.
Acta Neurol Scand. 1998 Dec;98(6):412-21.
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Applications of cortical magnetic stimulation.
Maertens de Noordhout A.
Laboratoire de neurophysiologie clinique, hopital de la Citadelle, Liege, Belgique.
In the last decade, a new electrophysiological tool has become
available since the development of painless magnetic stimulators able to
activate the primary motor cortex and the motor roots in conscious man.
Therefore, it became possible to measure the conduction time within
fast-conducting central motor pathways by substracting from the total
latency of muscle responses elicited by cortical stimuli the conduction
time in peripheral nerves. This technique proved sensitive enough to
illustrate early abnormalities of central motor conduction in various
neurological diseases such as multiple sclerosis, amyotrophic lateral
sclerosis, cervical spondylotic myelopathy, degenerative ataxias or
hereditary spastic paraplegias. When recorded early after stroke, motor
evoked potentials are also a valuable tool to predict functional
outcome. They can also illustrate subtle pathophysiological disturbances
in diseases where there is no direct involvement of central motor
pathways such as Parkinson's disease, dystonia or epilepsy. Magnetic
cortical stimulation also offers unique opportunities to explore
intracerebral inhibitory and excitatory circuits and mechanisms of brain
plasticity. The recent development of rapid rate stimulators also
enables functional studies of non-motor cerebral regions such as visual
or frontal cortices. Moreover, rapid rate stimulation seems useful in
the treatment of drug-resistant depression but the safety of this
procedure, particularly with regard to the production of seizures or
kindling, remains to be fully documented.
Neurophysiol Clin. 1998 Feb;28(1):9-30.
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Transcranial magnetic stimulation in diagnosis of trigeminal neuralgia.
Kotterba S, Tegenthoff M, Malin JP.
Neurologische Klinik und Poliklinik der Ruhr-Universitat Bochum.
Patients with trigeminal neuralgia are usually investigated by
elicitation of the orbicularis oculi reflex and trigeminal evoked
potentials. These neurophysiological methods do not allow direct
judgement of the trigeminal nerve. By transcranial magnetic stimulation,
however, non-invasive investigation of the efferent part of the
trigeminal nerve is possible. 10 patients (4 men, 6 women, aged from 43
to 73 years) with trigeminal neuralgia affecting the second or third
division were examined. In all patients bilateral long-latency responses
after stimulation of the tractus corticonuclearis and short-latency
responses after stimulation of the proximal part of the trigeminal nerve
were registered. 8 patients showed normal short- and long-latency
responses, while in one other patient the long-latency responses were
delayed on both sides. The remaining patient revealed a significant
difference of amplitude compared to the contralateral long-latency
response. This patient had a pontine lesion as shown by blink reflex and
a pathological trigeminal evoked potential. In both these latter
patients multiple sclerosis was diagnosed. Use of transcranial magnetic
stimulation may thus prove helpful in the differential diagnosis of
neurological disorders presenting with trigeminal neuralgia.
Nervenarzt. 1994 Apr;65(4):267-70.
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Magnetic brain stimulation: a tool to explore the action of the motor cortex on single human spinal motoneurones.
Mills KR.
University Dept of Clinical Neurology, Radcliffe Infirmary, Oxford, UK.
The human brain can be stimulated by a single intense magnetic pulse
over the scalp. Currents induced within the cranium excite the motor
cortex and cause limb muscles to contract. The discharge of single motor
units, the firing of which is maintained by voluntary effort, can be
modulated by magnetic stimuli. Peri-stimulus time histograms suggest
that after a cortical stimulus spinal motoneurones are induced to fire
by a sequence of EPSPs arising from a train of impulses transmitted
monosynaptically over fast-conducting corticospinal fibres. In multiple
sclerosis both dispersion of this descending volley and partial
transmission failure can impair motoneurone excitation and may explain
motor symptoms in these patients.
Trends Neurosci. 1991 Sep;14(9):401-5.
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Magnetic stimulation of the human brain and peripheral nervous
system: an introduction and the results of an initial clinical
evaluation.
Barker AT, Freeston IL, Jalinous R, Jarratt JA.
This report describes a novel method of stimulating the motor cortex
and deep peripheral nerves in humans. The technique, developed in the
Department of Medical Physics of Sheffield University, uses a large
pulse of magnetic field to induce currents within the body and is
painless. The basic principles of magnetic stimulation are described,
and the technique is compared with conventional electrical stimulation.
Safety aspects are discussed with reference to established clinical
electrical and magnetic procedures. The results of the first clinical
study using magnetic stimulation are described and show clear central
motor pathway slowing in multiple sclerosis patients.
Neurosurgery. 1987 Jan;20(1):100-9.
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