Biomedical subjects

Michele Tinazzi

Publications and source records attributed to Michele Tinazzi.

30 records · Page 2Linked to original sources

PubMed2003

Temporal discrimination of cross-modal and unimodal stimuli in generalized dystonia.

BACKGROUND: Motor and nonmotor timing functions and cross-modal processing of visual-tactile signals may be linked to basal ganglia. These neural structures are thought to be dysfunctional in dystonia. OBJECTIVE: To test whether cross-modal stimulation influences deficits of temporal discrimination in dystonia. METHODS: Eight patients with generalized dystonia and 10 control subjects were asked to discriminate whether pairs of unimodal (tactile or visual) and cross-modal (visual and tactile) stimuli were simultaneous or sequential and, in the latter case, which stimulus preceded the other. Visual stimuli consisted of red lights and tactile stimuli of non-noxious electrical shocks. Intervals between stimuli in each pair were increased from 0 to 400 msec (in steps of 10 msec). RESULTS: Patients with dystonia recognized the asynchrony between the experimental stimuli and judged correctly which stimulus in a pair came first, at significantly longer intervals than did controls. Moreover, differences in performance between patients and controls were maximal for cross-modal stimuli. The defective performance of patients with dystonia in the cross-modal combinations showed a high positive correlation with the severity of symptoms. CONCLUSION: Patients with generalized dystonia present with difficulties both in timing functions and in cross-modal processing of visual-tactile stimuli.

Adult↗

PubMed2003

Temporal processing of visuotactile and tactile stimuli in writer's cramp.

Neurophysiological studies in animals show that basal ganglia are involved not only in motor and nonmotor timing functions but also in integrating tactile and visual signals delivered in the peripersonal space. We tested temporal discrimination of cross-modal and unimodal stimuli in 13 controls and 14 patients with writer's cramp, a disorder supposedly linked to dysfunction of basal ganglia. Subjects were asked to discriminate whether pairs of visual, tactile, or visuotactile stimuli were simultaneous or sequential (temporal discrimination threshold) and which stimulus preceded the other (temporal order judgment). Patients were impaired in temporal processing of tactile and cross-modal stimuli. A significant positive correlation between temporal deficits and the severity of disability was detected for both affected and unaffected sides. Findings suggest that multimodal and not only modality-specific temporal processing is defective in focal hand dystonia. Deficits of temporal processing of stimuli delivered to the unaffected side may represent a behavioral index of the susceptibility to develop dystonia and thus have remarkable practical and theoretical implications.

Adult↗

PubMed2003

Role of the somatosensory system in primary dystonia.

The pathophysiology of dystonia is still not fully understood, but it is widely held that a dysfunction of the corticostriatal-thalamocortical motor circuits plays a major role in the pathophysiology of this syndrome. Although the most dramatic symptoms in dystonia seem to be motor in nature, marked somatosensory perceptual deficits are also present in this disease. In addition, several lines of evidence, including neurophysiological, neuroimaging and experimental findings, suggest that both motor and somatosensory functions may be defective in dystonia. Consequently, abnormal processing of the somatosensory input in the central nervous system may lead to inefficient sensorimotor integration, thus contributing substantially to the generation of dystonic movements. Whether somatosensory abnormalities are capable of triggering dystonia is an issue warranting further study. Although it seems unlikely that abnormal somatosensory input is the only drive to dystonia, it might be more correlated to the development of focal hand than generalized dystonia because local somesthetic factors are more selectively involved in the former than in the latter where, instead it seems to be a widespread deficit in processing sensory stimuli of different modality. Because basal ganglia and motor areas are heavily connected not only with somatosensory areas, but also with visual and acoustic areas, it is possible that abnormalities of other sensory modalities, such as visual and acoustic, may also be implicated in the pathophysiology of more severe forms of primary dystonia. Further studies have to be addressed to the assessment of the role of sensory modalities and their interaction on the pathophysiology of different forms of primary dystonia.

Afferent Pathways↗

PubMed2003

Impaired heteronymous somatosensory motor cortical inhibition in dystonia.

A typical pathophysiological abnormality in dystonia is cocontraction of antagonist muscles, with impaired reciprocal inhibitory mechanisms in the spinal cord. Recent experimental data have shown that inhibitory interactions between antagonist muscles have also a parallel control at the level of the sensorimotor cortex. The aim of this work was to study heteronymous effects of a median nerve stimulus on the corticospinal projections to forearm muscles in dystonia. We used the technique of antagonist cortical inhibition, which assesses the conditioning effect of median nerve afferent input on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in ipsilateral forearm extensor muscles at rest. Nine healthy subjects and 10 patients with torsion dystonia participated in the study. MEPs and somatosensory evoked potentials were normal in patients. In healthy subjects, median nerve stimulation at 15- to 18-msec intervals inhibited the test MEPs in forearm extensors. In dystonic patients, median nerve stimulation delivered at the same conditioning-test intervals elicited significantly less inhibition of the test MEP. On the whole, these data suggest an impaired sensory-motor integration in dystonia and, more specifically, the decreased antagonistic cortical inhibition could suggest that functional interactions between antagonist muscles are primarily impaired at the cortical level.

Adult↗

PubMed2003

Functional plasticity in the human primary somatosensory cortex following acute lesion of the anterior lateral spinal cord: neurophysiological evidence of short-term cross-modal plasticity.

The primary somatosensory cortex (S1) in adult animals and humans is capable of rapid modification after deafferentation. These plastic changes may account for a loss of tonic control by nociceptive inputs over inhibitory mechanisms within structures of the dorsal column-medial lemniscal system. Most studies, however, have been performed under conditions where deafferentation of C and A delta fibres coexists with large-diameter fibres deafferentation. In this study the effect of the acute lesion of one ascending anterior lateral column on neuronal activity within the dorsal column-medial lemniscal system was assessed by recording somatosensory evoked potentials (SEPs) in seven patients who underwent unilateral percutaneous cervical cordotomy (PCC) as treatment for drug-resistant malignant pain.Spinal, brainstem and cortical SEPs were recorded 2h before and 3h after PCC by stimulating the posterior tibial nerve at both ankles. Amplitudes of cortical potentials obtained by stimulation of the leg contralateral to PCC were significantly increased after PCC. No significant changes in spinal or brainstem potentials were observed. PCC did not affect SEP components obtained by stimulation of the leg ipsilateral to PCC. Our results suggest that nociceptive deafferentation may induce a rapid modulation of cortical neuronal activity along the lemniscal pathway, thus providing the first evidence in humans of short-term cortical plasticity across the spinothalamic and lemniscal systems.

Aged↗

PubMed2003

Therapeutic effects of peripheral repetitive magnetic stimulation on myofascial pain syndrome.

OBJECTIVE: To evaluate short- and medium-term effects of peripheral repetitive magnetic stimulation (rMS) on myofascial pain. METHODS: Eighteen patients who presented with myofascial trigger points (TPs) at the level of the superior trapezius were separated into two groups according to a restricted randomization scheme. Group 1 (n=9) underwent treatment with rMS that consisted of a total of 10 sessions, each lasting 20min, in which 4000 magnetic stimuli were administered in 5s trains at 20Hz at the TP. Group 2 (n=9) received a placebo treatment that consisted of the application of a non-functioning ultrasound therapy device to the TP. Patients were evaluated before treatment, at the end of treatment, and again 1 week and 1 month after the conclusion of the treatment. Clinical evaluation included parameters for measuring pain levels (VAS, NPDVAS and algometry), the myofascial TP characteristics and the range of cervical movement (ROM). RESULTS: The rMS group showed a significant improvement in VAS, NPDVAS, algometry, as well as in the characteristics of the TP after conclusion of treatment. Improvements in the ROM were also present in rotation and controlateral bending. This improvement persisted after 1 month. On the other hand, the placebo group did not show any significant improvement in the tests considered. CONCLUSIONS: The results of this study show that peripheral rMS may have positive short- and medium-term therapeutic effects on myofascial pain.

Adult↗

PubMed2003

Short-term plastic changes of the human nociceptive system following acute pain induced by capsaicin.

OBJECTIVE: To investigate possible neuroplastic changes induced by pain in cerebral areas devoted to nociceptive input processing. METHODS: CO(2) laser-evoked potentials (LEPs) were recorded from 10 healthy subjects after stimulation of the right and left hand dorsum. Acute pain was obtained by topical application of capsaicin on the skin of right hand dorsum. LEPs were recorded after right and left hand stimulation before capsaicin, at the peak pain and 10-20 min after capsaicin removal. Right hand LEPs were evoked by laser stimuli delivered over the zone of secondary hyperalgesia during capsaicin and on both the zones of primary and secondary hyperalgesia after capsaicin removal. RESULTS: After right hand stimulation, the vertex LEPs, which are generated in the cingulate cortex, were significantly decreased in amplitude during capsaicin application and after capsaicin removal. Moreover, the topography of these potentials was modified after capsaicin removal, shifting from the central toward the parietal region. Dipolar modelling showed that the dipolar source in the anterior cingulate cortex moved backward after capsaicin removal. All these changes were not observed after stimulation of the left hand, contralateral to the application of capsaicin, thus suggesting that functional changes are selective for the painful skin and the adjacent territories. CONCLUSIONS: Our results suggest that acute cutaneous pain may inhibit the neural activity in regions of central nervous system processing nociceptive inputs and cortical representation of these inputs can be rapidly modified in presence of acute pain.

Adult↗

PubMed2003

Rapid modulation of cortical proprioceptive activity induced by transient cutaneous deafferentation: neurophysiological evidence of short-term plasticity across different somatosensory modalities in humans.

Single cell recording in non-human primates shows plastic changes of cortical somatic representations across different types of somatic inputs originating from the same peripheral territory. In humans, muscle afferents from first dorsal interosseus are supplied by the ulnar nerve while the cutaneous territory overlying this muscle is supplied by the radial nerve. This peculiar anatomical nervous distribution allowed us to devise an experimental model which provided a unique opportunity to assess, in humans with a non-invasive technique, the functional relationships between cutaneous and muscle afferent inputs originating from the same peripheral territory. We recorded spinal, brainstem and cortical somatosensory potentials evoked by stimulation of muscle afferents of the right first dorsal interosseus before, during and after anaesthetic block of the sensitive branch of the ipsilateral radial nerve. Amplitude of parietal N20 and P27 and frontal N30 somatosensory evoked potential components showed an increase of amplitudes with more profound anaesthesia. Amplitudes returned to pre-anaesthetic values several minutes after anaesthesia. By contrast, spinal N13 and brainstem P14 potentials did not change throughout the experiment. Results show, for the first time in humans, that a transient cutaneous deafferentation may induce rapid modulation of cortical activity evoked by stimulation of muscle afferents originating in the anaesthetic territory.

Adult↗

PubMed2003

Pain-related modulation of the human motor cortex.

Pain is a complex multi-dimensional phenomenon that influences a wide variety of nervous system functions, including sensory--discriminative, affective--motivational and cognitive--evaluative components. So far, these components have been studied in both patients with chronic pain and in normal subjects in whom pain was induced experimentally. The interaction between pain and motor function is not fully understood, although from everyday life it is known that pain affects movements. The effects of pain on motor control are typically seen as a limited or impaired ability to perform movements. Most studies have dealt with the effects of pain on the spinal cord reflexes, but in recent years, several lines of evidence suggest that the interaction between motor and pain systems in conditions of pain induced experimentally, rather than a simple spinal reflex, is a more complex process that involves also supraspinal brain areas. Although pain-motor interaction shows different features and time course depending on different pain variables, such as duration (tonic versus phasic pain), submodalities (deep versus superficial pain) and location (distal versus proximal pain), a common finding is that pain is able to inhibit the motor cortex. This motor cortex inhibition may act as a sort of motor 'decerebration' so as to allow the spinal motor system to freely develop protective responses to noxious stimulation. Further studies are required to assess the effects of pain on the motor system in patients suffering from chronic pain, in order to develop innovative rational therapeutic strategies to reduce both pain and motor disability.

Electric Stimulation↗

PubMed2002

Deficits of temporal discrimination in dystonia are independent from the spatial distance between the loci of tactile stimulation.

To assess whether spatial variables influence deficits of temporal somesthetic discrimination in dystonic patients, 10 patients with idiopathic dystonia and 12 healthy controls were tested with pairs of non-noxious electrical stimuli separated by different time intervals. Stimuli were delivered: (1) to the pad of the index finger (same-point condition), (2) to the pad and to the base of the index finger (same-finger condition), and (3) to the pad of the index and ring fingers (different-finger condition). Subjects were asked to report whether they perceived single or double stimuli in the first condition and synchronous or asynchronous stimuli in the second and third conditions. Somesthetic temporal discrimination thresholds (STDTs) were obtained by computing the shortest time interval at which stimuli, applied to the left or the right hand, were perceived as separate in the first condition or asynchronous in the second and third conditions. STDTs were significantly higher in dystonic patients than controls in all three conditions. In both dystonia patients and controls, STDTs resulted highest in conditions whereby stimuli were maximally separated in space. Results extend current knowledge of deficits of somesthetic temporal discrimination in dystonia by showing that temporal deficits are not influenced by spatial variables.

Adult↗

PubMed2002

Time-related changes of excitability of the human motor system contingent upon immobilisation of the ring and little fingers.

OBJECTIVES: To examine possible changes of excitability of the human motor system contingent upon immobilisation of two hand fingers. METHODS: Two series of 5 transcranial magnetic stimulation (TMS) sessions were carried out on different days (1, 2, 3, 4, and 7). In one series (fingers immobilised, FI), subjects wore for 4 days a device that kept immobilised the left fourth and fifth finger. In the other series (fingers free, FF), no constraining device was used. Focal TMS was applied over the right motor cortex and motor evoked potentials (MEPs) were recorded from left abductor digiti minimi (immobilised) and first dorsal interosseus (non-immobilised) muscles. Intensities of 10, 30, and 50% above the resting motor threshold (rMT), were used. RESULTS: In FI series, rMT for both muscles showed significant increase on days 3, 4, and 7 with respect to day 1. At high stimulation intensity a clear decrease of MEPs amplitude was observed on days 3 and 4 for both muscles. Since no time-related changes of peripheral (M-wave) and spinal (F-wave) excitability were noted, MEPs and rMT changes are likely to have a cortical origin. In FF series, no changes of excitability were detected. CONCLUSIONS: Sensorimotor restriction of two fingers induces an early decrease of excitability, possibly at cortical level, which involves not only the immobilised muscle but also muscles with purportedly overlapping neural representations.

Adult↗

PubMedDate not supplied

The effect of two different rehabilitation treatments in cervical dystonia: preliminary results in four patients.

The most widespread approach to rehabilitation of cervical dystonia is electromyographic (EMG) biofeedback. However, consensus is lacking regarding the true effectiveness of this technique. The aim of this study was to evaluate how cervical dystonia was influenced by two rehabilitative treatments, namely a standard biofeedback program and a novel physiotherapy program consisting of postural reeducation exercises and passive elongation of myofascial cervical structures. Both programs were consecutively administered to 4 patients with cervical dystonia. The study design was a behavioral analysis of single cases. The main outcome measures were a head realignment test, a disability questionnaire and a pain visual analogue scale (VAS). Each patient's performance was evaluated before the study and after the first and second program. Furthermore, the disability questionnaire and the pain VAS were administered 3, 6, and 9 months after the end of the treatments. The physiotherapy program showed therapeutic effects comparable to those of EMG biofeedback. Reductions of disability and of pain were still present 3-9 months after the end of the treatments. These preliminary results suggest that the physiotherapy program proposed in the present study may be a promising method for rehabilitation of cervical dystonia.

Adult↗