Massimo Cincotta

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS)

A group of European experts was commissioned to establish guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS) from evidence published up until March 2014, regarding pain, movement disorders, stroke, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, consciousness disorders, tinnitus, depression, anxiety disorders, obsessive-compulsive disorder, schizophrenia, craving/addiction, and conversion. Despite unavoidable inhomogeneities, there is a sufficient body of evidence to accept with level A (definite efficacy) the analgesic effect of high-frequency (HF) rTMS of the primary motor cortex (M1) contralateral to the pain and the antidepressant effect of HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC). A Level B recommendation (probable efficacy) is proposed for the antidepressant effect of low-frequency (LF) rTMS of the right DLPFC, HF-rTMS of the left DLPFC for the negative symptoms of schizophrenia, and LF-rTMS of contralesional M1 in chronic motor stroke. The effects of rTMS in a number of indications reach level C (possible efficacy), including LF-rTMS of the left temporoparietal cortex in tinnitus and auditory hallucinations. It remains to determine how to optimize rTMS protocols and techniques to give them relevance in routine clinical practice. In addition, professionals carrying out rTMS protocols should undergo rigorous training to ensure the quality of the technical realization, guarantee the proper care of patients, and maximize the chances of success. Under these conditions, the therapeutic use of rTMS should be able to develop in the coming years.

Dissociation of the pathways mediating ipsilateral and contralateral motor‐evoked potentials in human hand and arm muscles

1 Growing evidence points toward involvement of the human motor cortex in the control of the ipsilateral hand. We used focal transcranial magnetic stimulation (TMS) to examine the pathways of these ipsilateral motor effects. 2 Ipsilateral motor‐evoked potentials (MEPs) were obtained in hand and arm muscles of all 10 healthy adult subjects tested. They occurred in the finger and wrist extensors and the biceps, but no response or inhibitory responses were observed in the opponens pollicis, finger and wrist flexors and the triceps. 3 The production of ipsilateral MEPs required contraction of the target muscle. The threshold TMS intensity for ipsilateral MEPs was on average 1.8 times higher, and the onset was 5.7 ms later (in the wrist extensor muscles) compared with size‐matched contralateral MEPs. 4 The corticofugal pathways of ipsilateral and contralateral MEPs could be dissociated through differences in cortical map location and preferred stimulating current direction. 5 Both ipsi‐ and contralateral MEPs in the wrist extensors increased with lateral head rotation toward, and decreased with head rotation away from, the side of the TMS, suggesting a privileged input of the asymmetrical tonic neck reflex to the pathway of the ipsilateral MEP. 6 Large ipsilateral MEPs were obtained in a patient with complete agenesis of the corpus callosum. 7 The dissociation of the pathways for ipsilateral and contralateral MEPs indicates that corticofugal motor fibres other than the fast‐conducting crossed corticomotoneuronal system can be activated by TMS. Our data suggest an ipsilateral oligosynaptic pathway, such as a corticoreticulospinal or a corticopropriospinal projection as the route for the ipsilateral MEP. Other pathways, such as branching of corticomotoneuronal axons, a transcallosal projection or a slow‐conducting monosynaptic ipsilateral pathway are very unlikely or can be excluded.

Transcranial magnetic stimulation and epilepsy

Epileptic conditions are characterized by an altered balance between excitatory and inhibitory influences at the cortical level. Transcranial magnetic stimulation (TMS) provides a noninvasive evaluation of separate excitatory and inhibitory functions of the cerebral cortex. In addition, repetitive TMS (rTMS) can modulate the excitability of cortical networks. We review the different ways that TMS has been used to investigate pathophysiological mechanisms and effects of antiepileptic drugs in patients with epilepsy and epileptic myoclonus. The safety of different TMS techniques is discussed too. Finally, we discuss the therapeutic prospects of rTMS in this field.

Slow Repetitive TMS for Drug-resistant Epilepsy: Clinical and EEG Findings of a Placebo-controlled Trial

Summary:  Purpose: To assess the effectiveness of slow repetitive transcranial magnetic stimulation (rTMS) as an adjunctive treatment for drug‐resistant epilepsy.

Modulation of interhemispheric inhibition by volitional motor activity: an ipsilateral silent period study

Brief interruption of voluntary EMG in a hand muscle by focal transcranial magnetic stimulation (TMS) of the ipsilateral primary motor cortex (M1), the so‐called ipsilateral silent period (ISP), is a measure of interhemispheric motor inhibition. However, little is known about how volitional motor activity would modulate the ISP. Here we tested in 30 healthy adults to what extent and under what conditions voluntary activation of the stimulated right M1 by moving the left hand strengthens interhemispheric inhibition as indexed by an enhancement of the ISP area in the maximally contracting right first dorsal interosseous (FDI). Left index finger abduction, already at low levels of contraction, significantly enhanced the ISP compared to left hand at rest. Even imagination of left index finger movement enhanced the ISP compared to rest or mental calculation. This enhancement occurred in the absence of motor‐evoked potential amplitude modulation in the left FDI, thus excluding a non‐specific contribution from an increase in right M1 corticospinal excitability. Contraction of the left extensor indicis, but not contraction of more proximal left upper limb or left or right lower limb muscles also enhanced the ISP. A reaction time experiment showed that the ISP enhancement developed at a late stage of movement preparation just before or at movement onset. Interhemispheric inhibition of the motor‐evoked potential as tested by a bifocal paired‐pulse TMS protocol and thought to be mediated via a neuronal circuit different to the ISP was not enhanced when tested under identical motor task conditions. Finally, ISP enhancement by contraction of the left FDI correlated inversely with EMG mirror activity in the right FDI during phasic abductions of the left index finger. Our findings strongly suggest that voluntary M1 activation by real or imagined movement of the contralateral hand increases interhemispheric motor inhibition of the opposite M1. This phenomenon shows substantial topographical, temporal and neuronal circuit specificity, and has functional significance as it probably plays a pivotal role in suppressing mirror activity.

Central nervous system adverse effects of new antiepileptic drugs: A meta-analysis of placebo-controlled studies

OBJECTIVE Systematic review and meta-analysis of the most frequent treatment-emergent central nervous system adverse events (CNS AEs) of new antiepileptic drugs (AEDs) from double-blind, add-on, placebo-controlled studies conducted in adult epileptic patients and identification of dose-adverse effect relationships. METHODS Trial reports found by searching Medline and journals. Outcome was the number of patients complaining of treatment-emergent CNS AEs. Sixteen predefined CNS AEs were considered. Risk differences (RDs) were calculated for individual studies and summary statistics estimated using the random effect model. Predefined CNS AEs in patients treated with active drug (broken down into dose levels) or placebo were extracted and the RDs (95% CI) for CNS AEs were calculated. RESULTS Thirty-six suitable studies identified. No meta-analysis was possible for oxcarbazepine and tiagabine (only one study each included). For these drugs RDs were calculated from single studies. Gabapentin was significantly associated with somnolence 0.13 (0.06-0.2) and dizziness 0.11 (0.07-0.15); lamotrigine with dizziness 0.11 (0.05-0.17), ataxia 0.12 (0.01-0.24) and diplopia 0.12 (0.00-0.24); levetiracetam with somnolence 0.06 (0.01-0.11); pregabalin with somnolence 0.11 (0.07-0.15), dizziness 0.22 (0.16-0.28), ataxia 0.10 (0.06-0.14) and fatigue 0.04 (0.01-0.08); topiramate with somnolence 0.09 (0.04-0.14), dizziness 0.06 (0.00-0.11), cognitive impairment 0.14 (0.06-0.22) and fatigue 0.06 (0.01-0.12); zonisamide with somnolence 0.06 (0.02-0.11) and dizziness 0.06 (0.00-0.12). The dose-response relationship was analysed only for those CNS AEs significantly associated with the AED. CONCLUSIONS No comparison between drugs was possible. One CNS AE was significantly more frequent for levetiracetam, two for zonisamide and gabapentin, three for lamotrigine and four for pregabalin and topiramate.

Suprathreshold 0.3 Hz repetitive TMS prolongs the cortical silent period: potential implications for therapeutic trials in epilepsy.

OBJECTIVE To investigate the after-effects of 0.3 Hz repetitive transcranial magnetic stimulation (rTMS) on excitatory and inhibitory mechanisms at the primary motor cortex level, as tested by single-pulse TMS variables. METHODS In 9 healthy subjects, we studied a wide set of neurophysiological and behavioral variables from the first dorsal interosseous before (Baseline), immediately after (Post 1), and 90 min after (Post 2) the end of a 30 min long train of 0.3 Hz rTMS delivered at an intensity of 115% resting motor threshold (RMT). Variables under investigation were: maximal M wave, F wave, and peripheral silent period after ulnar nerve stimulation; RMT, amplitude and stimulus-response curve of the motor evoked potential (MEP), and cortical silent period (CSP) following TMS; finger-tapping speed. RESULTS The CSP was consistently lengthened at both Post 1 and Post 2 compared with Baseline. The other variables did not change significantly. CONCLUSIONS These findings suggest that suprathreshold 0.3 Hz rTMS produces a relatively long-lasting enhancement of the inhibitory mechanisms responsible for the CSP. These effects differ from those, previously reported, of 0.9-1 Hz rTMS, which reduces the excitability of the circuits underlying the MEP and does not affect the CSP. This provides rationale for sham-controlled trials aiming to assess the therapeutic potential of 0.3 Hz rTMS in epilepsy.

Vegetative versus Minimally Conscious States: A Study Using TMS-EEG, Sensory and Event-Related Potentials

Differential diagnoses between vegetative and minimally conscious states (VS and MCS, respectively) are frequently incorrect. Hence, further research is necessary to improve the diagnostic accuracy at the bedside. The main neuropathological feature of VS is the diffuse damage of cortical and subcortical connections. Starting with this premise, we used electroencephalography (EEG) recordings to evaluate the cortical reactivity and effective connectivity during transcranial magnetic stimulation (TMS) in chronic VS or MCS patients. Moreover, the TMS-EEG data were compared with the results from standard somatosensory-evoked potentials (SEPs) and event-related potentials (ERPs). Thirteen patients with chronic consciousness disorders were examined at their bedsides. A group of healthy volunteers served as the control group. The amplitudes (reactivity) and scalp distributions (connectivity) of the cortical potentials evoked by TMS (TEPs) of the primary motor cortex were measured. Short-latency median nerve SEPs and auditory ERPs were also recorded. Reproducible TEPs were present in all control subjects in both the ipsilateral and the contralateral hemispheres relative to the site of the TMS. The amplitudes of the ipsilateral and contralateral TEPs were reduced in four of the five MCS patients, and the TEPs were bilaterally absent in one MCS patient. Among the VS patients, five did not manifest ipsilateral or contralateral TEPs, and three of the patients exhibited only ipsilateral TEPs with reduced amplitudes. The SEPs were altered in five VS and two MCS patients but did not correlate with the clinical diagnosis. The ERPs were impaired in all patients and did not correlate with the clinical diagnosis. These TEP results suggest that cortical reactivity and connectivity are severely impaired in all VS patients, whereas in most MCS patients, the TEPs are preserved but with abnormal features. Therefore, TEPs may add valuable information to the current clinical and neurophysiological assessment of chronic consciousness disorders.

Reorganization of the motor cortex in a patient with congenital hemiparesis and mirror movements

Article abstract Abnormal branching of corticospinal fibers from the unaffected motor cortex is responsible for mirror movements in patients with congenital hemiparesis, but it is unknown which mechanisms enable these patients to lateralize motor activity. Using multiunit electromyographic analysis and transcranial magnetic stimulation, the authors provide evidence for nonbranched crossed and uncrossed corticospinal projections and intracortical inhibition of the mirror hand. They propose that this remarkable reorganization of the unaffected motor cortex helps these patients to reduce mirror movements.

Adjunctive lamotrigine therapy in patients with refractory seizures: a lifetime cost–utility analysis

AbstractObjective: Lamotrigine as add-on treatment (500 mg per day) is effective in patients with refractory epilepsy, but its high cost requires a pharmacoeconomic analysis. We conducted a retrospective lifetime cost–utility study in which clinical data were derived from a recent placebo-controlled clinical trial, cost-of-illness data were drawn from a previous ad-hoc study, and quality-of-life values were obtained by prospectively interviewing a separate group of 81 patients referred to our institution with epilepsy. Results: Our analysis showed that chronic lamotrigine treatment implies an incremental lifetime cost of about