1,720,986 research outputs found
Altered response to repetitive transcranial magnetic stimulation in patients with chronic primary insomnia
No full textBackground: We aimed at evaluating the amplitude changes of the motor evoked potentials (MEPs) induced by of low-frequency (LF) repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) in10 patients with primary insomnia (PI) and in 10 age-matched healthy controls. Methods: Median peak-to-peak MEP amplitudes were assessed in all subjects at three times: at baseline (T0), after the first train of a single rTMS session (T1), and after the whole rTMS procedure (T2). This consists of 20 trains of 1 Hz stimulation with 50 stimuli per train and an intertrain interval of 30 s. Results: Resting motor threshold (RMT) and MEPs amplitude did not differ between the two groups at T0. A reduction of MEP size was observed at both T1 and T2 in all subjects, but this was significantly less pronounced in patients than in control subjects. Conclusions: The lack of MEP inhibition reflects an altered response to LF rTMS in patients with PI. These rTMS findings are indicative of an altered cortical plasticity in inhibitory circuits within M1 in PI. Subjects with PI exhibited an impairment of the LTD-like mechanisms induced by inhibitory rTMS, thus providing further support to the involvement of GABA neurotransmission in the pathophysiology of PI
Transcranial magnetic stimulation and bladder function: a systematic review
No full textOBJECTIVE: We aimed at assessing the usefulness of motor evoked potentials (MEPs) for exploring the integrity of striated sphincters and pelvic floor motor innervation in normal subjects and of repetitive transcranial magnetic stimulation TMS (rTMS) in patients with neurogenic bladder dysfunction. METHODS: A systematic literature search was conducted using PubMed and Embase. RESULTS: We identified, reviewed and discussed 11 articles matching the inclusion criteria. CONCLUSIONS: The assessment of MEPs could represent a useful tool in the investigation of patients with urologic disorders. High frequency rTMS can improve detrusor contraction and/or urethral sphincter relaxation in patients with multiple sclerosis and bladder dysfunction. Low frequency (LF) rTMS seems to be an effective treatment of neurogenic lower urinary tract dysfunctions in subjects with Parkinson's disease and possibly other neurodegenerative disorders. Furthermore, rTMS might have the potential to restore bladder and bowel sphincter function after incomplete spinal cord injury. LF rTMS could also relieve some symptoms of bladder pain syndrome and chronic pelvic pain. SIGNIFICANCE: The clinical applicability of MEPs appears to be questionable, since a poor reproducibility was detected for all pelvic floor muscles. The use of rTMS in this field is emerging and the results of a few preliminary studies should be replicated in controlled, randomized studies with larger sample sizes
Repetitive transcranial magnetic stimulation in traumatic brain injury: evidence from animal and human studies
Full text linkWe provide here the first systematic review on the studies dealing with repetitive transcranial magnetic stimulation (rTMS) for traumatic brain injury (TBI) in animals and humans. Several experimental studies in animal models have explored with promising results the use of rTMS to enhance neuroprotection and recovery after TBI. However, there are surprisingly few studies that have obtained substantial evidence regarding effects of rTMS in humans with TBI, many of them are case reports investigating the heterogeneous conditions linked to TBI. The most studies have investigated the effects of rTMS in subjects with post-traumatic depression and variable effects have been observed. rTMS has been proposed as an experimental approach for the treatment of disorders of consciousness (DOC), but in subjects with TBI therapeutic effects on DOC have also been variously documented. Beneficial effects have been reported in subjects with cognitive/emotional disturbances and auditory dysfunction (tinnitus and hallucinations), although the results are somewhat conflicting. rTMS applied over the left prefrontal cortex may relieve, at least transiently, post-traumatic headache. Isolated rTMS studies have been performed in TBI patients with motor impairment, chronic dizziness or pain. Especially whether provided in combination, rTMS and neurorehabilitation may be synergistic in the potential to translate experimental findings in the clinical practice. In order to reach definitive conclusions, well-designed randomized controlled studies with larger patient samples, improved design and optimized rTMS setup, are warranted to verify and corroborate the initial promising findings
Transcranial magnetic stimulation and gait disturbances in Parkinson's disease: A systematic review
No full textTranscranial magnetic stimulation (TMS) may offer a reliable means of characterizing important pathophysiologic aspects of motor impairments in Parkinson's disease (PD). Moreover, high-frequency repetitive TMS (rTMS), especially if delivered bilaterally over motor cortical regions, can have beneficial effects on parkinsonian motor symptoms. However, only a few studies have investigated the effects of rTMS on freezing of gait (FOG) and other gait disturbances in PD. We aimed at investigating in this narrative review the usefulness of TMS for exploring the pathophysiology of gait impairment and at evaluating the therapeutic effects of rTMS in this context. The combination of rTMS and treadmill training was found to enhance the effect of physical therapy. Use of an H-coil enables stimulation of deep regions of the brain (for example medial prefrontal cortex) and may be used as a target for add-on therapy in the future. In contrast, theta burst stimulation has proven to be ineffective in treating gait disturbances in PD patients. Dual-mode NIBS, in particular preconditioning motor cortex rTMS by transcranial direct current stimulation, might also represent a novel therapeutic approach for patients with gait disturbances. Recent studies suggest that the supplementary motor area could be an appropriate target for brain stimulation when treating PD patients with FOG. Further large sample and well-designed clinical studies are required to evaluate how the possible positive effects of rTMS can be sustained over time and to determine the optimal stimulation protocols including target, stimulation intensity/duration and number of sessions
Disinhibition of sensory cortex in patients with amyotrophic lateral sclerosis
No full textIn patients with amyotrophic lateral sclerosis (ALS) a motor cortical hyperexcitability has been reported in transcranial magnetic stimulation studies, but little is known about the neuronal excitability in other cortical areas. The aim of the present study was the functional evaluation of the sensory cortex in subjects with ALS by assessing the high-frequency somatosensory evoked potentials (HF-SEP). No significant HF-SEP abnormalities were observed in ALS patients with disease duration of < 2 years, while the patients with a disease duration of > 2 years we found a large amplitude reduction of post-synaptic HF-SEP burst. Since post-synaptic burst of HF-SEP is thought to reflect the activity of cortical inhibitory interneurons, our findings provide further evidence that disinhibition is a primary characteristic of ALS that also involves the somatosensory cortex
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Usefulness of EEG Techniques in Distinguishing Frontotemporal Dementia from Alzheimer's Disease and Other Dementias
Full text linkThe clinical distinction of frontotemporal dementia (FTD) and Alzheimer's disease (AD) may be difficult. In this narrative review we summarize and discuss the most relevant electroencephalography (EEG) studies which have been applied to demented patients with the aim of distinguishing the various types of cognitive impairment. EEG studies revealed that patients at an early stage of FTD or AD displayed different patterns in the cortical localization of oscillatory activity across different frequency bands and in functional connectivity. Both classical EEG spectral analysis and EEG topography analysis are able to differentiate the different dementias at group level. The combination of standardized low-resolution brain electromagnetic tomography (sLORETA) and power parameters seems to improve the sensitivity, but spectral and connectivity biomarkers able to differentiate single patients have not yet been identified. The promising EEG findings should be replicated in larger studies, but could represent an additional useful, noninvasive, and reproducible diagnostic tool for clinical practice
Role of human prefrontal cortex in the modulation of conditioned eyeblink responses
No full textClassical conditioning of the eyeblink reflex (EBC) is a simple form of associative motor learning. EBC is heavily dependent on cerebellar function, but experimental studies also suggest that the prefrontal cortex (PFC) orchestrates a neuronal network which interacts with the cerebellum to mediate the conditioned eyeblink responses (CR). To further investigate the role of PFC for EBC in humans, we aimed in this study at assessing whether acquisition of CR can be modulated by focal repetitive transcranial magnetic stimulation (rTMS) given as theta burst stimulation (TBS) over the dorsolateral PFC (DLPFC). A standard delay conditioning paradigm with a 540 ms tone as conditioned stimulus (CS) coterminating with a 100 ms air puff as unconditioned stimulus (US) was used in a total of 60 healthy subjects (35 female, 25 male, mean age 28.4 ± 2.4 years). One hundred paired CS-US trials and 30 extinction CS alone trials were given. TBS was applied over the DLPFC ipsilaterally to the US during the acquisition phase. Subjects were randomly assigned to three groups (n = 20) using excitatory intermittent TBS (iTBS), inhibitory continuous TBS (cTBS) or sham stimulation. CR acquisition was significantly enhanced by iTBS (mean total CR incidence 63.1 ± 6.5%) and significantly reduced by cTBS (13 ± 2%) compared to sham stimulation (25.1 ± 6.7%). We provide thus physiological evidence that the acquisition of this type of associative learning is critically modulated by PFC activity in humans
Effects of intrathecal baclofen therapy in subjects with disorders of consciousness: a reappraisal
No full textBaclofen is a structural analogue of gamma-amino-butyric acid (GABA), which reduces spastic hypertonia of striated muscle due to a mechanism of GABAB-ergic inhibition of mono- and polysynaptic reflexes at the spinal level. There are reports of patients with severe disorders of consciousness that presented a substantial improvement following intrathecal baclofen (ITB) administration for severe spasticity. The neural mechanisms underlying the clinical recovery after ITB have not yet been clarified. Baclofen could modulate sleep-wake cycles that may be dysregulated and thus interfere with alertness and awareness. The diminished proprioceptive and nociceptive sensory inputs may relieve thalamo-cortical neural networks involved in maintaining the consciousness of the self and the world. ITB treatment might also promote the recovery of an impaired GABAergic cortical tone, restoring the balance between excitatory and inhibitory cortical activity. Furthermore, glutamatergic synapses are directly or indirectly modulated by GABAB-ergic receptors. Neurophysiological techniques (such as transcranial magnetic stimulation, electroencephalography, or the combination of both) can be helpful to explore the effects of intrathecal or oral baclofen on the modulation of neural cortical circuits in humans with disorders of consciousness
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