Saxby Pridmore

Motor threshold in transcranial magnetic stimulation: a comparison of a neurophysiological method and a visualization of movement method.

Motor threshold is a means of quantifying stimulus in transcranial magnetic stimulation. Two methods are used. One involves neurophysiology techniques and the other is visualization of movement. The aim was to compare the percentage of total machine output (PTMO) necessary to achieve motor threshold using these different methods. Neurophysiological and visualization of movement thresholds were determined in six subjects. In all subjects, the two thresholds were achieved with a < 10% difference in PTMO. Determination of motor threshold with a neurophysiological and a visualization of movement method produced similar results.

Comparison of unlimited numbers of rapid transcranial magnetic stimulation (rTMS) and ECT treatment sessions in major depressive episode

Repetitive transcranial magnetic stimulation (rTMS) is a new technology which holds promise as a treatment of psychiatric disorders. Most work to date has been on depression. Superiority to placebo has been indicated in three small blind studies. We compared the antidepressant effects of rTMS and ECT in 32 patients suffering major depressive episode (MDE) who had failed to respond to at least one course of medication. There was no limit to the number of treatment sessions which could be given and treatment was continued until remission occurred or response plateaued. A significant main effect for treatment type was found [Pillai trace = 0.248, F(3,28) = 3.076, p = 0.044; power = 0.656], reflecting an advantage for ECT patients on measures of depression overall, however, rTMS produced comparable results on a number of measures. Blind raters using the 17-item Hamilton Depression Rating Scale (HDRS) found the rate of remission (HDRS = ? 8) was the same (68.8%), and the percentage improvement over the course of treatment of 55.6% (rTMS) and 66.4% (ECT), while favouring ECT, was not significantly different. Significant differences were shown (p & 0.03) in percentage improvement on Beck Depression Inventory ratings (rTMS, 45.5%; ECT, 69.1%), but not for improvement in Visual Analogue ratings of mood (rTMS 42.3%; ECT, 57%). rTMS has antidepressant effects of useful proportions and further studies are indicated.

Changes to cold detection and pain thresholds following low and high frequency transcranial magnetic stimulation of the motor cortex.

There is some evidence that repetitive transcranial magnetic stimulation (rTMS) can alleviate the experience of chronic pain. The mechanisms by which rTMS may induce pain relief, however, are unknown. The present study examined whether a session of rTMS would produce sensory threshold changes in healthy individuals. Detection and pain thresholds for cold sensations were compared following low frequency (1 Hz) (Experiment 1) and high frequency (20 Hz) (Experiment 2) repetitive TMS. While cold detection threshold was significantly lowered by both rTMS rates, only high frequency rTMS produced a significant change in cold pain threshold. In contrast, sham rTMS did not alter thresholds for cold stimuli. These findings provide evidence that sensory thresholds can be influenced by repetitive transcranial magnetic stimulation.

Repetitive Transcranial Magnetic Stimulation Is Efficacious as an Add-On to Pharmacological Therapy in Complex Regional Pain Syndrome (CRPS) Type I

UNLABELLED Single-session repetitive transcranial magnetic stimulation (rTMS) of the motor cortex (M1) is effective in the treatment of chronic pain patients, but the analgesic effect of repeated sessions is still unknown. We evaluated the effects of rTMS in patients with refractory pain due to complex regional pain syndrome (CRPS) type I. Twenty-three patients presenting CRPS type I of 1 upper limb were treated with the best medical treatment (analgesics and adjuvant medications, physical therapy) plus 10 daily sessions of either real (r-) or sham (s-) 10 Hz rTMS to the motor cortex (M1). Patients were assessed daily and after 1 week and 3 months after the last session using the Visual Analogical Scale (VAS), the McGill Pain Questionnaire (MPQ), the Health Survey-36 (SF-36), and the Hamilton Depression (HDRS). During treatment there was a significant reduction in the VAS scores favoring the r-rTMS group, mean reduction of 4.65 cm (50.9%) against 2.18 cm (24.7%) in the s-rTMS group. The highest reduction occurred at the tenth session and correlated to improvement in the affective and emotional subscores of the MPQ and SF-36. Real rTMS to the M1 produced analgesic effects and positive changes in affective aspects of pain in CRPS patients during the period of stimulation. PERSPECTIVE This study shows an efficacy of repetitive sessions of high-frequency rTMS as an add-on therapy to refractory CRPS type I patients. It had a positive effect in different aspects of pain (sensory-discriminative and emotional-affective). It opens the perspective for the clinical use of this technique.

Rapid transcranial magnetic stimulation and normalization of the dexamethasone suppression test.

Non‐suppression of post‐dexamethasone cortisol is a feature of endogenous/melancholic depression. Normalization of the dexamethasone suppresion test (DST) response is a feature of remission and antidepressant treatment. Twelve consecutive depressed non‐suppressers were treated with rapid transcranial magnetic stimulation (rTMS). Six demonstrated normalization and good clinical improvement which was sustained for at least 1 month. Thus, rTMS has some biological effects in common with other antidepressant treatments.

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

Abstract 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.

Substitution of rapid transcranial magnetic stimulation treatments for electroconvulsive therapy treatments in a course of electroconvulsive therapy

Our aim was to determine whether rTMS treatments could be substituted for ECT treatments in a course of ECT, 1) without loss of antidepressant effect, and 2) without increase in subjective side‐effects. We used a randomized, single‐blind, controlled study. Two streams were conducted. Stream 1 received non‐dominant unilateral (UL) ECT only, treatments being given 3 times per week for 2 weeks. Stream 2 received a combination of treatments: one UL ECT on Day 1 and rTMS on the following 4 days, all repeated once, after a 2‐day respite. Twenty‐two patients were recruited and 11 were allocated to each stream. There was no evidence that the antidepressant effect of the ECT only stream was superior to that of the ECT plus rTMS stream. There was no increase in subjective side‐effects in the ECT plus rTMS stream. On the contrary, this stream was accompanied by less side effects than the ECT only stream in this study. In conclusion, we have determined that it is possible to substitute rTMS treatments for ECT treatments in a course of ECT without loss of antidepressant effect or an increase in subjective side‐effects, using the described parameters. It is possible that the combination of ECT plus rTMS will provide a means of avoiding some of the subjective side‐effects encountered with the conventional course of ECT. Further studies are indicated. Depression and Anxiety 12:118–123, 2000.

Neuroimaging in psychopathy

Objective: The biological basis of psychopathy remains to be fully elucidated. Evidence suggests a genetic contribution and dysfunction of the serotonin system. The objective of this article is to review the contribution of the neuroimaging of the last decade to our understanding of psychopathy. Method: A literature search was conducted using PubMed and the words psychopath, antisocial personality disorder, dissocial personality disorder, violence, image and imaging. In addition, the reference lists of the identified papers, and recent textbooks, were perused for additional sources. Results: Five structural and 15 functional neuroimaging studies were selected and examined. Structural studies have reported decreased prefrontal grey matter, decreased posterior hippocampal volume and increased callosal white matter, but to this point, these have not been replicated. Functional studies suggest reduced perfusion and metabolism in the frontal and temporal lobes. Abnormalities of function have been reported, predominantly in frontal and temporal lobe structures during classical conditioning and response inhibition tasks, and in the processing of emotional words and pictures. Conclusion: Functional neuroimaging strongly suggests dysfunction of particular frontal and temporal lobe structures in psychopathy. However, there are difficulties in selecting homogeneous index cases and appropriate control groups. Further studies are necessary. Responses depend on genetic endowment, early life experience, the sociocultural context and the significance of any stimulus to the individual.

Transcranial magnetic stimulation in the treatment of psychiatric disorders.

Transcranial magnetic stimulation (TMS) is a new technology that applies the principles of electromagnetism to deliver an electrical field to the cerebral cortices. Well established in diagnostic electrophysiology, TMS is now being studied as a treatment for psychiatric disorders. Evidence suggests this technique is safe and acceptable to patients. The future may see the application of TMS in obsessive–compulsive disorder, post‐traumantic stress disorder and mania. There is strong evidence that it will become an accepted treatment of depression.

Transcranial magnetic stimulation as therapy for depression and other disorders

Objective: To provide an overview of the progress and prospects of transcranial magnetic stimulation as a psychiatric therapy for depression. Method: Published and unpublished studies of the usefulness of transcranial magnetic stimulation as a therapy for depression were assessed, and characterised in terms of a consistent measure of dosage. Additional information was obtained through correspondence, personal meetings and visits to facilities. Results: Transcranial magnetic stimulation, a means for inducing small regional currents in the brain, has been used in clinical neurology for some time, and can be used on conscious subjects with minimal side-effects. Early researchers noticed transient mood effects on people receiving this treatment, which prompted several inconclusive investigations of its effects on depressed patients. More recently, knowledge of functional abnormalities associated with depression has led to trials using repetitive transcranial magnetic stimulation to stimulate underactive left prefrontal regions, an approach which has produced short-term benefits for some subjects. The higher dosage delivered by high-frequency repetitive transcranial magnetic stimulation appears to produce greater benefits; scope exists for more conclusive studies based on extended treatment periods. Conclusions: Repetitive transcranial magnetic stimulation is a promising technology. The reviewed evidence indicates that it may be useful in the treatment of depression, and perhaps other disorders which are associated with regional hypometabolism. Should repetitive transcranial magnetic stimulation prove an effective, non-invasive, drug-free treatment for depression, a range of disorders could be similarly treatable.