Sessions Of Transcranial Magnetic Stimulation Research Articles

Effect of levetiracetam on cortical excitability: a transcranial magnetic stimulation study

We studied the effect of levetiracetam (LEV), an anticonvulsant with a novel mechanism of action, on cortical excitability, measured using transcranial magnetic stimulation (TMS). For this purpose, 38 healthy volunteers were assessed in two TMS sessions, before and after an oral dose of 3000 mg LEV. Resting motor threshold (RMT), intracortical facilitation (ICF) and intracortical inhibition (ICI), cortical silent period (CSP) threshold and duration and motor-evoked potential (MEP) amplitude were calculated. After treatment with LEV, RMT was increased (mean +/- SD: 63 +/- 14% of the maximum stimulator output) compared with baseline (58 +/- 11%). CSP threshold was decreased after LEV (54 +/- 10%; baseline, 57 +/- 11%). CSP duration was increased after LEV (116 +/- 37 ms; baseline: 102 +/- 33 ms). LEV did not affect ICF or ICI or mean MEP amplitude significantly. Our results indicate that LEV modulates some aspects of cortical excitability. Whereas the increase in the RMT most probably reflects the effect of LEV on ion channel activity, effects on the CSP might represent a modulation of GABA receptors at cortical and spinal level.

Significant analgesic effects of one session of postoperative left prefrontal cortex repetitive transcranial magnetic stimulation: A replication study

In a recent preliminary trial in 20 patients after gastric bypass surgery, 20 minutes of repetitive transcranial magnetic stimulation (TMS) over the left prefrontal cortex was associated with a 40% reduction in postoperative patient-controlled morphine use. As is the case with all novel scientific findings, and especially those that might have an impact on clinical practice, replicability is paramount. This study sought to test this finding for replication and to more accurately estimate the effect size of this brief intervention on postoperative morphine use and postoperative pain and mood ratings. Twenty participants who underwent gastric bypass surgery completed this replication and extension study. Beck Depression Inventory and Center for Epidemiological Studies Depression scale scores were collected before surgery and at the time of discharge from the hospital. Immediately after surgery, participants were randomly assigned to receive 20 minutes of real or sham repetitive TMS (rTMS) (10 Hz, 10 seconds-ON, 20 seconds-OFF for a total of 4000 pulses). Patient-controlled morphine pump usage was tracked throughout each participant's postoperative hospital stay. In addition, pain and mood ratings were collected via visual analogue scales twice per day. Findings from the original postoperative TMS trial were replicated, as cumulative morphine usage curves were significantly steeper among patients receiving sham TMS, and participants receiving real TMS had used 35% less morphine at the time of discharge than participants receiving sham TMS. At the time of discharge, subjects who had received real TMS had used 42.50 mg of morphine, whereas subjects receiving sham TMS had used an average of 64.88 mg. When the data from the original preliminary trial were combined with the data from this replication trial, a significant difference in cumulative morphine usage was observed between subjects receiving real and sham TMS. Overall, participants who received real TMS used 36% less morphine and had significantly lower ratings of postoperative pain-on-average, and pain-at-its-worst than participants receiving sham. In addition, participants who received real TMS rated their mood-at-its-worst as significantly better than participants receiving sham. The effect of a single 20-minute session of TMS on postoperative pain and morphine use appears to be large (Cohen's d = 0.70) and clinically meaningful. Lastly, cross-lag correlational analyses indicate that improvements in mood follow improvements in pain by approximately 12 hours, supporting the notion that postoperative analgesic TMS effects are not driven by antidepressant effects. Although more research is needed to verify these observed effects independently, findings from the original postoperative TMS trial were replicated. TMS may have the potential to significantly improve current standards of postoperative care among gastric bypass patients, and further studies may be warranted on other surgical populations. Future investigations should use methodology that permits more definitive conclusions about causal effects of TMS on postoperative pain (for example, double-blinding, sham stimulation that is matched with real TMS with respect to scalp discomfort).

Transcranial magnetic stimulation synchronized with maximal movement effort of the hemiplegic hand after stroke: A double-blinded controlled pilot study

The aim of this study was to evaluate the effects of transcranial magnetic stimulation synchronized with maximal effort to make a target movement in patients with chronic hemiplegia involving the hand. Non-randomized double-blinded controlled trial. Nine chronic patients with hemiplegia who were unable to fully extend the affected fingers following stroke. Patients were assigned to receive 100 pulses of active or sham transcranial magnetic stimulation of the affected hemisphere per session. Each active or sham pulse was delivered during maximal effort at thumb and finger extension as a target movement. A blinded rater assessed stroke impairments at baseline, immediately after, and one week after 4 weekly transcranial magnetic stimulation sessions. Motor evoked potential amplitudes were measured at each session. All sessions were completed without adverse effects. Immediately after the fourth transcranial magnetic stimulation session, 4 of 5 patients in the active transcranial magnetic stimulation group (80%) had either reduced wrist flexor spasticity or improved manual performance; no such change occurred in the sham group (Fisher's exact test, p < 0.05). Effects persisted one week later. In the active transcranial magnetic stimulation group, 3 patients who showed an increase in motor evoked potential amplitudes all had improvement in clinical assessments. Transcranial magnetic stimulation synchronized with maximum effort to make a target movement improved hand motor function in patients with chronic hemiplegia.

Within-Session Mood Changes From TMS in Depressed Patients

Within-Session Mood Changes From TMS in Depressed Patients

Disturbed surround inhibition in preclinical parkinsonism

Objective Surround inhibition in the motor system is an essential mechanism for selective execution of desired movements. To evaluate the functional operation of surround inhibition in Parkinson disease, we performed a transcranial magnetic stimulation (TMS) study in the asymptomatic hands of hemiparkinsonism patients. Methods TMS was set to be triggered by self-initiated flexion of the index finger at different intervals from 3 to 2000 ms. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of control TMS at rest. Normalized MEP amplitudes of the patients’ self-triggered TMS sessions at different intervals were compared to those of the controls. Results During index finger flexion, MEP amplitudes from the little finger muscle were unchanged in normal subjects. However, they were enhanced in Parkinson patients, despite the absence of any motor disturbance. Conclusions These results suggest that the functional operation of surround inhibition is impaired in Parkinson disease. This disturbance may precede motor disturbance in Parkinson disease. Significance Impaired surround inhibition can be useful to detect preclinical parkinsonism.

Changes to somatosensory detection and pain thresholds following high frequency repetitive TMS of the motor cortex in individuals suffering from chronic pain

Research has shown that transcranial magnetic stimulation (TMS) results in a transient reduction in the experience of chronic pain. The present research aimed to investigate whether a single session of high frequency TMS is able to change the sensory thresholds of individuals suffering from chronic pain. Detection and pain thresholds for cold and heat sensations were measured before and after 20 Hz repetitive TMS (rTMS) administered over the motor cortex. A significant decrease in temperature for cold detection and pain thresholds and a significant increase in temperature for heat pain thresholds were evident following a single session of rTMS. In contrast, no change in detection and pain thresholds was obtained following sham rTMS. The finding that rTMS can have a direct effect on sensory thresholds in individuals suffering from chronic pain has implications for the therapeutic use of rTMS in the relief of chronic pain.

A Controlled Study of Repetitive Transcranial Magnetic Stimulation in Medication-Resistant Major Depression

Repetitive transcranial magnetic stimulation (TMS) as a treatment for depression has shown statistically significant effects, but the clinical significance of these effects has been questioned. Patients with medication-resistant depression were randomized to receive 15 sessions of active or sham repetitive TMS delivered to the left dorsolateral prefrontal cortex at 110% the estimated prefrontal cortex threshold. Each session consisted of 32 trains of 10 Hz repetitive TMS delivered in 5-second trains. The primary end point was treatment response defined as a >or=50% decrease in Hamilton Depression Rating Scale (HDRS) score at both 1 and 2 weeks following the final repetitive TMS treatment. Remission was defined as a HDRS score < 8. The response rate for the TMS group was 30.6% (11/35), significantly (p = .008) greater than the 6.1% (2/33) rate in the sham group. The remission rate for the TMS group was 20% (7/35), significantly (p = .033) greater than the 3% (1/33) rate in the sham group. The HDRS scores showed a significantly (p < .002) greater decrease over time in the TMS group compared with the sham group. Transcranial magnetic stimulation can produce statistically and clinically significant antidepressant effects in patients with medication-resistant major depression.

Normative data on changes in transcranial magnetic stimulation measures over a ten hour period

Objective To establish normative data on the single-subject variation of resting motor thresholds and silent periods over 10 h using transcranial magnetic stimulation (TMS). Methods Seventeen neurologically normal volunteers aged 18–36 underwent a series of seven TMS sessions conducted over the course of a single 10-h period. During each session, resting motor threshold and cortical silent period were recorded for the first dorsal interosseus muscle of each hand during focal TMS of the contralateral motor area. Results We provide data on the normal limits of variability in these measures for averaged group data and for single subjects. Specifically, we report intersession, intrasession, and interhemispheric variability of data for each subject individually. Conclusions: Although group averages are highly reliable, individual subjects showed substantial variability over time, especially for silent periods. Interhemispheric asymmetry was a less stable indicator than previously reported. Significance These norms may guide the interpretation of changes in TMS measures within groups or within an individual patient over brief periods of time or as an immediate response to intervention.

Clinical application of single‐pulse transcranial magnetic stimulation for the treatment of depression

Transcranial magnetic stimulation (TMS) has been recently suggested for the treatment of patients with major depression. Based on the results of the authors' pilot study showing a possible antidepressive effect of single-pulse TMS, a clinical trial was conducted involving patients with major depression. For the present study single-photon emission computed tomography (SPECT) was recorded for six of the target patients to study the effects of TMS on the local blood flow volume. Twenty-three inpatients meeting the Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) criteria for major depression were invited to participate in the study. Depressive symptoms were rated using the Hamilton Rating Scale for Depression (HAM-D). Patients were given 10 stimuli over the frontal area of both sides for a total of 20 stimuli in a session. The subjects had daily TMS session for 5 days as an add-on therapy. In addition, six patients had their quantitative (99m)Tc-ethyl cysteinate dimer SPECT images measured before and after TMS treatment. Compared with the value 2 days prior to the start of TMS therapy (24.2 +/- 4.9), the average HAM-D scale dropped significantly to 15.3 +/- 6.6 on the day after completion of such therapy. The results of SPECT showed that the regional cerebral blood flow (rCBF) of the bilateral frontal region had increased in four out of six patients when comparing before and after treatment. The present study shows that single-pulse TMS, which is widely used as a neurological test method, possesses a wide range of antidepressive effects without inducing adverse reactions. The results suggest that although repetitive TMS is steadily becoming the mainstay technique today, single-pulse TMS also possesses sufficient antidepressive effects.

Accuracy of Stereotaxic Positioning of Transcranial Magnetic Stimulation

In cognitive neuroscience, optically tracked frameless stereotaxic navigation has been successfully used to precisely guide transcranial magnetic stimulation (TMS) to desired cortical areas for brain-mapping purposes. Thereby, potential sources of imprecision are the fixation of a reference frame to the head of the subject and the referencing procedure according to certain landmarks (LM). The aim of our study was to evaluate the accuracy of frameless stereotaxic coil positioning in a standard experimental setting. A parameter for accuracy is the reproducibility of LM coordinates. In order to test the stability of the referencing for stereotaxic positioning within a single TMS session (within-session stability), the coordinates of six predefined facial LM in nine subjects were recorded first after the initial registration and second after a 20 minutes TMS session. The two sets of coordinates were then compared. The reliability of the positioning coordinates between different TMS sessions (inter-session repeatability) was addressed by registering the subjects LM coordinates in two independent TMS sessions. The variance of the recorded coordinates was analyzed. Altogether, LM were registered 1728 times (192 measures per subject). Within-session stability: The mean Euclidean distance (MED) between the LM position coordinates before and after a TMS session was 1.6 mm, when pooling over all LM. Inter-session repeatability: The MED between the LM positions recorded after the reference procedures of two different sessions showed an average deviation of 2.5 mm. In conclusion, optically tracked frameless stereotaxic coil positioning is from the technical viewpoint of high stability and repeatability. It is therefore a precise method for TMS brain mapping studies or for repeated TMS treatments, with the need of topographically exact stimulation.

Exploring the contributions of premotor and parietal cortex to spatial compatibility using image-guided TMS

Functional brain imaging studies have demonstrated increased activity in dorsal premotor and posterior parietal cortex when performing spatial stimulus–response compatibility tasks (SRC). We tested the specific role of these regions in stimulus–response mapping using single-pulse transcranial magnetic stimulation (TMS). Subjects were scanned using functional magnetic resonance imaging (fMRI) prior to the TMS session during performance of a task in which spatial compatibility was manipulated. For each subject, the area of increased signal within the regions of interest was registered onto their own high-resolution T1-weighted anatomic scan. TMS was applied to these areas for each subject using a frameless stereotaxic system. Task accuracy and reaction time (RT) were measured during blocks of compatible or incompatible trials and during blocks of real TMS or sham stimulation. On each trial, a single TMS pulse was delivered at 50, 100, 150, or 200 ms after the onset of the stimulus in the left or right visual field. TMS over the left premotor cortex produced various facilitatory effects, depending on the timing of the stimulation. At short intervals, TMS appeared to prime the left dorsal premotor cortex to select a right-hand response more quickly, regardless of stimulus–response compatibility. The strongest effect of stimulation, however, occurred at the 200-ms interval, when TMS facilitated left-hand responses during the incompatible condition. Facilitation of attention to the contralateral visual hemifield was observed during stimulation over the parietal locations. We conclude that the left premotor cortex is one of the cortical regions responsible for overriding automatic stimulus–response associations.

Reduction of transcallosal inhibition upon awakening from REM sleep in humans as assessed by transcranial magnetic stimulation.

The aim of the study is to assess, in humans, transcallosal inhibition upon awakening from rapid eye movement (REM) and non-REM sleep, by paired-pulse transcranial magnetic stimulation (TMS). During the daytime, a baseline session of motor evoked potentials (MEPs) was recorded. During the nighttime, the TMS sessions were administered just before sleep onset and upon awakenings from REM and stage 2 sleep, both in the early and final part of night. The sleep research laboratory at the University of Rome "La Sapienza." Ten right-handed subjects participated in the experiment for 4 consecutive sleep-recording nights. N/A. During the daytime, a robust transcallosal inhibition was found; the MEP amplitude reduction ranged from 35% to 40%. During the nighttime, a decrease of transcallosal inhibition from right-to-left motor cortex, as compared to that from left-to-right motor cortex, was observed. The direct assessment of MEP changes, as a function of sleep stage and of the time of night, pointed to a drop of transcallosal inhibition after awakening from REM sleep. Therefore, the inhibitory activity of transcallosal fibers observed after non-REM awakening almost disappeared after REM sleep awakenings. The drastic drop of transcallosal inhibition after awakenings from REM sleep represents the first evidence in humans of a change of interhemispheric connectivity mediated by the corpus callosum during this sleep stage and may open new avenues for a better understanding of some aspects of sleep mechanisms (ie, dreaming function and dream mentation).

Brain effects of TMS delivered over prefrontal cortex in depressed adults: role of stimulation frequency and coil-cortex distance.

Relative regional brain blood flow was measured in 23 clinically depressed adults by using ECD SPECT at baseline and again during actual prefrontal transcranial magnetic stimulation (TMS) following 5 daily sessions of TMS. TMS over prefrontal cortex caused increased activity in cortex directly under the stimulation (inversely correlated with distance from scalp to cortex) and decreased activity in remote regions (anterior cingulate and anterior temporal poles). High-frequency rTMS (20 Hz) caused more relative flow immediately below the TMS coil than did low-frequency rTMS (5 Hz). Confirming the hypotheses tested, repeated daily TMS over the prefrontal cortex in medication-free depressed adults appears to change both local and remote blood flow in a manner that may also depend on the frequency of stimulation and coil to outer cortex distance.

Brain Effects of TMS Delivered Over Prefrontal Cortex in Depressed Adults: Role of Stimulation Frequency and Coil-Cortex Distance

Relative regional brain blood flow was measured in 23 clinically depressed adults by using ECD SPECT at baseline and again during actual prefrontal transcranial magnetic stimulation (TMS) following 5 daily sessions of TMS. TMS over prefrontal cortex caused increased activity in cortex directly under the stimulation (inversely correlated with distance from scalp to cortex) and decreased activity in remote regions (anterior cingulate and anterior temporal poles). High-frequency rTMS (20 Hz) caused more relative flow immediately below the TMS coil than did low-frequency rTMS (5 Hz). Confirming the hypotheses tested, repeated daily TMS over the prefrontal cortex in medication-free depressed adults appears to change both local and remote blood flow in a manner that may also depend on the frequency of stimulation and coil to outer cortex distance.

Transcranial magnetic stimulation in an amphetamine hyperactivity model of mania.

Transcranial magnetic stimulation (TMS) of the brain has been reported to have therapeutic effects in mania, as well as depression. TMS has previously been reported to have effects similar to those of electroconvulsive shock in rat models of depression. We, therefore, studied TMS in amphetamine-induced hyperactivity as a rat model of mania. While two and seven daily TMS sessions significantly reduced activity after amphetamine, twice-daily TMS for 7 days enhanced activity after amphetamine. The results suggest that TMS treatment to rats interacts with the effects of amphetamine; the specific effects may be dependent on the schedule of treatment.

Magnetic Stimulation of the Brain in Animal Depression Models Responsive to ECS

Studies in humans show antidepressant potential for transcranial magnetic stimulation (TMS). We therefore studied TMS in animal models of depression and compared its effects with those of ECS. ECS in rats has several robust behavioral effects, including enhancement of apomorphine-induced stereotypy, reduction of immobility time in the Porsolt swim test, and increases in seizure threshold for subsequent stimulation. Seven or 10 days of daily TMS consistently enhanced apomorphine-induced stereotypy, whereas a single session of TMS did not. Two TMS treatments markedly reduced immobility in the Porsolt swim test, as does ECS. A single TMS treatment markedly reduces the percentage of rats seizing in response to a ECS-like electrical stimulus to the brain 10 s later, as does an ECS treatment itself but not a sub-convulsive electrical stimulus to the brain. Long-term administration of ECS as well as other antidepressant treatments downregulates beta-adrenergic receptors. We found that TMS significantly reduced the density of [3H]CGP-12177 (a radioligand with beta-adrenergic affinity) binding sites in cortical (p < 0.05) but not hippocampal membranes. The role of monoamines in the mechanism of action of antidepressant treatments was investigated in numerous studies. Region-specific changes in the brain steady-state levels, and turnover rates of monoamines were detected 10 s after administration of a single repetitive TMS (rTMS) session. In the striatum and hippocampus, dopamine levels were increased by 25 +/- 1.5% and 18 +/- 0.8%, respectively, but were reduced in frontal cortex and decreased in the striatum and hippocampus in the TMS-treated rats with no change to the midbrain. TMS caused an increase in serotonin and 5-HIAA levels in the hippocampus but not in other brain regions examined in this study. The ability of TMS to induce behavioral and biochemical alterations similar to those of ECS may further support the potential role of TMS as an antidepressant treatment and bring us closer to the understanding of the mechanism of action of TMS.

Effect of transcranial magnetic stimulation in posttraumatic stress disorder: a preliminary study

Background: Transcranial magnetic stimulation (TMS) has become, over the last few years, a promising avenue for new research in affective disorders. In this study we have evaluated the clinical effect of slow TMS on posttraumatic stress disorder (PTSD) symptoms. Methods: Ten PTSD patients were given one session of slow TMS with 30 pulses of 1 m/sec each, 15 to each side of the motor cortex. Results: Symptoms of PTSD were assessed by using three psychological assessment scales, at four different time points. In this first, pilot, open study, TMS was found to be effective in lowering the core symptoms of PTSD: avoidance (as measured by the Impact of Event Scale), anxiety, and somatization (as measured by the Symptom Check List–90). A general clinical improvement was found (as measured by the Clinical Global Impression scale); however, the effect was rather short and transient. Conclusions: The present study showed TMS to be a safe and tolerable intervention with possibly indications of therapeutic efficacy for PTSD patients.