Gabriella Musumeci

Effects of lorazepam on short latency afferent inhibition and short latency intracortical inhibition in humans

Experimental studies have demonstrated that the GABAergic system modulates acetylcholine release and, through GABAA receptors, tonically inhibits cholinergic activity. Little is known about the effects of GABA on the cholinergic activity in the human central nervous system. In vivo evaluation of some cholinergic circuits of the human brain has recently been introduced using a transcranial magnetic stimulation (TMS) protocol based on coupling peripheral nerve stimulation with TMS of the motor cortex. Peripheral nerve inputs have an inhibitory effect on motor cortex excitability at short intervals (short latency afferent inhibition, SAI). We investigated whether GABAA activity enhancement by lorazepam modifies SAI. We also evaluated the effects produced by lorazepam on a different TMS protocol of cortical inhibition, the short interval intracortical inhibition (SICI), which is believed to be directly related to GABAA activity. In 10 healthy volunteers, the effects of lorazepam were compared with those produced by quetiapine, a psychotropic drug with sedative effects with no appreciable affinity at cholinergic muscarinic and benzodiazepine receptors, and with those of a placebo using a randomized double‐blind study design. Administration of lorazepam produced a significant increase in SICI (F3,9= 3.19, P= 0.039). In contrast to SICI, SAI was significantly reduced by lorazepam (F3,9= 9.39, P= 0.0002). Our findings demonstrate that GABAA activity enhancement determines a suppression of SAI and an increase of SICI.

Modulation of motor cortex neuronal networks by rTMS: comparison of local and remote effects of six different protocols of stimulation

Repetitive transcranial magnetic stimulation (rTMS) of human motor cortex can produce long-lasting changes in the excitability of excitatory and inhibitory neuronal networks. The effects of rTMS depend critically on stimulus frequency. The aim of our present study was to compare the effects of different rTMS protocols. We compared the aftereffects of 6 different rTMS protocols [paired associative stimulation at interstimulus intervals of 25 (PAS(25)) and 10 ms (PAS(10)); theta burst stimulation delivered as continuous (cTBS) or intermittent delivery pattern (iTBS); 1- and 5-Hz rTMS] on the excitability of stimulated and contralateral motor cortex in 10 healthy subjects. A pronounced increase of cortical excitability, evaluated by measuring the amplitude of motor evoked potentials (MEPs), was produced by iTBS (+56%) and PAS(25) (+45%). Five-hertz rTMS did not produce a significant increase of MEPs. A pronounced decrease of cortical excitability was produced by PAS(10) (-31%), cTBS (-29%), and 1-Hz rTMS (-20%). Short-interval intracortical inhibition was suppressed by PAS(10). Cortical silent period duration was increased by 1-Hz stimulation. No significant effect was observed in the contralateral hemisphere. Head-to-head comparison of the different protocols enabled us to identify the most effective paradigms for modulating the excitatory and inhibitory circuits activated by TMS.

Theta Burst Stimulation in the Rehabilitation of the Upper Limb: A Semirandomized, Placebo-Controlled Trial in Chronic Stroke Patients

Background. Noninvasive cortical stimulation could represent an add-on treatment to enhance motor recovery after stroke. However, its clinical value, including anticipated size and duration of the treatment effects, remains largely unknown. Objective. The authors designed a small semi-randomized clinical trial to explore whether long-lasting clinically important gains can be achieved by adding theta burst stimulation (TBS), a form of repetitive transcranial magnetic stimulation (TMS), to a rehabilitation program for the hand. Methods. A total of 41 chronic stroke patients received excitatory TBS to the ipsilesional hemisphere or inhibitory TBS to the contralesional hemisphere in 2 centers; each active group was compared with a group receiving sham TBS. TBS was followed by physical therapy for 10 working days. Patients and therapists were blinded to the type of TBS. Primary outcome measures (9-hole Peg Test [9HPT], Jebsen Taylor Test [JTT], and grip and pinch-grip dynamometry) were assessed 4, 30, and 90 days post treatment. The clinically important difference was defined as 10% of the maximum score. Results. There were no differences between the active treatment and sham groups in any of the outcome measures. All patients achieved small sustainable improvements—9HPT, 5% of maximum (confidence interval [CI] = 3%-7%); JTT, 5.7% (CI = 3%-8%); and grip strength, 6% (CI = 2%-10%)—all below the defined clinically important level. Conclusions. Cortical stimulation did not augment the gains from a late rehabilitation program. The effect size anticipated by the authors was overestimated. These results can improve the design of future work on therapeutic uses of TMS.

Modulating cortical excitability in acute stroke: A repetitive TMS study

OBJECTIVE Changes in cerebral cortex excitability have been demonstrated after a stroke and are considered relevant for recovery. Repetitive transcranial magnetic stimulation (rTMS) of the brain can modulate cerebral cortex excitability and, when rTMS is given as theta burst stimulation (TBS), LTP- or LTD-like changes can be induced. The aim of present study was to evaluate the effects of TBS on cortical excitability in acute stroke. METHODS In 12 acute stroke patients, we explored the effects of facilitatory TBS of the affected hemisphere and of inhibitory TBS of the unaffected hemisphere on cortical excitability to single-pulse transcranial magnetic stimulation (TMS) on both sides. The effects produced by TBS in patients were compared with those observed in a control group of age-matched healthy individuals. RESULTS In patients, both the facilitatory TBS of the affected motor cortex and the inhibitory TBS of the unaffected motor cortex produced a significant increase of the amplitude of MEPs evoked by stimulation of the affected hemisphere. The effects observed in patients were comparable to those observed in controls. CONCLUSIONS Facilitatory TBS over the stroke hemisphere and inhibitory TBS over the intact hemisphere in acute phase enhance the excitability of the lesioned motor cortex. SIGNIFICANCE TBS might be useful to promote cortical plasticity in stroke patients.

Transcranial magnetic stimulation and BDNF plasma levels in amyotrophic lateral sclerosis

Low- and high-frequency repetitive transcranial magnetic stimulation (rTMS) of the motor cortex results in lasting changes of excitatory neurotransmission. We investigated the effects of suprathreshold 1 Hz rTMS on brain derived neurotrophic factor (BDNF) plasma levels in 10 healthy subjects and effects of either 1 Hz or 20 Hz rTMS in four amyotrophic lateral sclerosis (ALS) patients. BDNF levels were progressively decreased by 1 Hz rTMS in healthy subjects; there was no effect of 1 Hz rTMS on BDNF plasma levels in ALS patients, an effect probably due to the loss of motor cortex pyramidal cells. High frequency rTMS determined a transitory decrease in BDNF plasma levels. Cumulatively these findings suggest that rTMS might influence the BDNF production by interfering with neuronal activity.

Immediate and Late Modulation of Interhemipheric Imbalance With Bilateral Transcranial Direct Current Stimulation in Acute Stroke

BACKGROUND Significant changes in neurophysiological and clinical outcomes in chronic stroke had been reported after tDCS; but there is a paucity of data in acute stroke. OBJECTIVE We aimed to evaluate whether a tDCS-induced modulation of primary motor cortex excitability in patients with acute stroke enhances motor recovery associated with rehabilitation and induces differential neuroplasticity. METHODS We conducted two experiments in acute stroke patients. In experiment 1 (14 patients), we tested the immediate effects of bilateral tDCS alone as compared to sham tDCS on recovery. Experiment 2 (20 patients) was designed to assess effects of bilateral tDCS delivered together with constraint-induced movement therapy (CIMT). In this experiment, we included a longer follow-up (3 months) and measured, in addition to the same clinical outcomes of experiment 1, changes of motor cortex excitability and the amount of promoted LTP-like activity. RESULTS Despite the expected improvement at 1 week, none of the clinical measures showed any different modulation in dependence of CIMT and tDCS. On the neurophysiological assessments, on the other hand, the Real_tDCS group, compared to Sham_tDCS group, showed a reduction of inter-hemispheric imbalance when considering the differences of motor evoked potential between both 3-month and 1 week follow up (P = 0.007) and three month and baseline (P = 0.015). CONCLUSIONS Despite the lack of additional clinical changes, real bilateral tDCS, together with CIMT, significantly reduces inter-hemispheric imbalance between affected and unaffected hemispheres. These findings may shed light on plasticity changes in acute stroke and its potential impact in chronic phases.

Repetitive transcranial magnetic stimulation for ALS: A preliminary controlled study

Repetitive transcranial magnetic stimulation (rTMS) of brain can modulate cortical neurotransmission, a novel paradigm of repetitive stimulation termed continuous theta-burst stimulation (cTBS) produces a pronounced and prolonged suppression of motor cortex excitability. The aim of this preliminary study was to investigate whether cTBS of motor cortex could have any beneficial effect in patients with amyotrophic lateral sclerosis (ALS). We performed a double-blind, placebo-controlled trial. Twenty patients with definite ALS were randomly allocated to blinded active or placebo stimulation. Repetitive stimulation of the motor cortex was performed for five consecutive days every month for six consecutive months. The primary outcome was the rate of decline as evaluated with the ALS functional rating scale. The treatment was well tolerated by the patients. Fifteen patients (seven active and eight sham) completed the study and were included in the 6-months analysis. Both active and sham patients deteriorated during treatment, however, active patients showed a modest but significant slowing of the deterioration rate. Though we cannot be sure whether the effects observed can be attributed to cTBS, because of the restricted number of patients studied, further investigation on a larger group of ALS patients is warranted. The results of the pilot study might open up a new therapeutic perspective in ALS based on neuromodulation.

Inhibitory theta burst stimulation of affected hemisphere in chronic stroke: a proof of principle, sham-controlled study.

Non-invasive brain stimulation is presently being tested as a potential therapeutic intervention for stroke rehabilitation. Following a model of competitive interactions between the hemispheres, these interventions aim to increase the plasticity of stroke hemisphere by applying either excitatory protocols to the damaged hemisphere or inhibitory protocols to the non-stroke hemisphere. Here we test the safety and feasibility of using an inhibitory protocol on the stroke hemisphere to improve the response to conventional therapy via a homeostatic increase in learning capacity. Twelve chronic stroke patients received TBS to stroke hemisphere (6 patients inhibitory TBS and 6 sham TBS) followed by physical therapy daily for 10 working days. Patients and therapists were blinded to the type of TBS. Action Research Arm Test (ARAT), Nine-Hole Pegboard Test (NHPT) and Jebsen-Taylor Test (JTT) were the primary outcome measures, grip and pinch-grip dynamometry were the secondary outcome measures. All patients improved ARAT and JTT scores for up to 3 months post-treatment. ARAT scores improved significantly in both real and sham groups, but only patients receiving real TBS significantly improved on the JTT: 3 months post-treatment mean execution time was reduced compared to baseline by 141 s for real group and by 65s for the sham group. This small exploratory study suggests that ipsilesional inhibitory TBS is safe and that it has the potential to be used in a larger trial to enhance the gain from a late rehabilitation program in chronic stroke patients.

Long-term motor cortex stimulation for amyotrophic lateral sclerosis

BACKGROUND Motor cortex stimulation has been proposed for treatment of amyotrophic lateral sclerosis (ALS) and preliminary studies have reported a slight reduction of disease progression using both invasive and noninvasive repetitive stimulation of the motor cortex. OBJECTIVE The aim of this proof of principle study was to investigate the effects of motor cortex stimulation performed for a prolonged period (about 2 years) on ALS progression. METHODS Two patients were included in the study; the first patient was treated with monthly cycles of repetitive transcranial magnetic stimulation (rTMS) and the second one was treated with chronic epidural motor cortex stimulation. The rate of progression of the disease before and during treatment was compared. RESULTS The treatments were well tolerated by the patients. Both patients deteriorated during treatment; however, the patient treated with rTMS showed a slight reduction in deterioration rate. CONCLUSIONS Although we cannot be sure whether the effects observed in the patient treated with rTMS can be attributed to this form of stimulation, our study set the groundwork for possible future studies investigating the effects of rTMS, for a prolonged period, on a larger group of ALS patients.

Motor cortex stimulation for ALS: A double blind placebo-controlled study

Preliminary data suggest that repetitive transcranial magnetic stimulation (rTMS) of the brain may produce a modest slowing of disease progression in amyotrophic lateral sclerosis (ALS). The present study was designed to test the hypothesis that rTMS given as continuous theta burst stimulation (cTBS), repeated monthly for one year, would affect ALS progression. We performed a double blind, placebo-controlled trial. Twenty patients with ALS were randomly allocated to blinded real or placebo stimulation. cTBS of the motor cortex was performed for five consecutive days every month for one year. Primary outcome was the rate of decline as evaluated with the revised ALS functional rating scale (ALSFRS-R). Treatment was well tolerated. There was no significant difference in the ALSFRS-R score deterioration between patients treated with real or placebo stimulation. ALSFRS-R mean scores declined from 32.0 (SD 7.1) at study entry to 23.1 (SD 6.3) at 12 months in patients receiving real cTBS and from 31.3 (SD 6.9) to 21.2 (SD 6.0) in those receiving placebo stimulation. Although cTBS proved a safe procedure, on the basis of the present findings a larger randomized confirmatory trial seems unjustified in ALS patients, at least in advanced stage of the disease.