TMS-evoked N100 responses as a prognostic factor in acute stroke

Rehabilitation programs, to be efficiently tailored, need clear prognostic markers. In acute stroke, neurophysiological measures, such as motor evoked potentials (MEPs), have been proposed, although with discordant results. The aim of this study was to identify a reliable neurophysiological measure of recovery in acute post-stroke individuals by combining MEPs and the N100 component of transcranial magnetic stimulation-evoked potentials (TEPs). Nine acute post-stroke subjects were included. Clinical evaluation performed in the first week after the event included administration of the European Stroke Scale and Barthel Index and recording of MEPs and TEPs; administration of the clinical scales was repeated after one and three months. The presence/absence of MEPs and TEPs showed correlations with motor outcome. Individuals with a poorer outcome showed absence of both MEPs and TEPs; absence of MEPs alone was related to a partial recovery. Given the results of this exploratory study, further investigation is needed to define the accuracy of combined use of MEPs and TEPs as an approach for predicting motor recovery after acute stroke

Risk factors for post-polio syndrome among an Italian population: a case-control study.

Post-polio syndrome (PPS) is a clinical syndrome of new weakness, fatigue and musculoskeletal pain occurring in a variable proportion of polio survivors decades after acute disease. To date, several risk factors for PPS development have been reported, although the etiology of this disorder remains elusive. Using a case-control design, we aimed to assess risk indicators for PPS in a group of Italian polio survivors. Subjects with prior poliomyelitis attending the rehabilitation hospital of Malcesine, Italy, were the target population. Patients with PPS, diagnosed according to the European Federation of Neurological Societies criteria, served as cases, while patients not meeting diagnostic criteria for PPS were used as controls. All subjects were assessed through a structured questionnaire made of 82 questions and neurological examination. The association with investigated risk factors (sex, age at polio onset, age at onset of symptoms, extension and severity of polio, employment) was analyzed by the calculation of the odds ratio. A total of 161 out of 391 eligible patients met the adopted diagnostic criteria for PPS, giving a frequency of 41.2\%. Symptoms most frequently complained by PPS patients were loss of muscle strength, loss of resistance, loss of muscle volume and generalized fatigue. Female gender, the presence of respiratory disturbance during the acute phase of polio and the use of orthoses and aids during the recovery and stabilization represented independent risk factors for PPS in the studied population

EEG and fMRI coregistration to investigate the cortical oscillatory activities during finger movement

Electroencephalography combined with functional magnetic resonance imaging (EEG-fMRI) may be used to identify blood oxygenation level dependent (BOLD) signal changes associated with physiological and pathological EEG event. In this study we used EEG-fMRI to determine the possible correlation between topographical movement-related EEG changes in brain oscillatory activity recorded from EEG electrodes over the scalp and fMRI-BOLD cortical responses in motor areas during finger movement. Thirty-two channels of EEG were recorded in 9 subjects during eyes-open condition inside a 1.5 T magnetic resonance (MR) scanner using a MR-compatible EEG recording system. Off-line MRI artifact subtraction software was applied to obtain continuous EEG data during fMRI acquisition. For EEG data analysis we used the event-related-synchronization/desynchronization (ERS/ERD) approach to investigate where movement-related decreases in alpha and beta power are located. For image statistical analysis we used a general linear model (GLM) approach. There was a significant correlation between the positive-negative ratio of BOLD signal peaks and ERD values in the electrodes over the region of activation. We conclude that combined EEG-fMRI may be used to investigate movement-related oscillations of the human brain inside an MRI scanner and the movement-related changes in the EMG or EEG signals are useful to identify the brain activation sources responsible for BOLD-signal changes

Changes in cerebral activity after decreased upper-limb hypertonus: An EMG-fMRI study

OBJECTIVE: Whereas several studies have used functional magnetic resonance imaging (fMRI) to investigate motor recovery, whether therapy to decrease post-stroke hypertonus alters central motor patterns remains unclear. In this study, we used continuous electromyography (EMG)-fMRI to investigate possible changes in movement-related brain activation in patients receiving Botulinum toxin (BoNT-A) for hand-muscle hypertonus after chronic stroke. METHODS: We studied eight stroke patients all of whom had hemiparesis and associated upper-limb hypertonus. All patients underwent an fMRI-EMG recording and clinical-neurological assessment before BoNT-A and 5 weeks thereafter. The handgrip motor task during imaging was fixed across both patients and controls. The movements were metronome paced, movement amplitude and force were controlled with a plastic orthosis, dynamometer and EMG recording. An age-matched control group was recruited from among healthy volunteers underwent the same fMRI-EMG recording. RESULTS: Before BoNT-A, while patients moved the paretic hand, fMRI detected wide bilateral activation in the sensorymotor areas (SM1), in the supplementary motor area (SMA) and cerebellum. After BoNT-A blood oxygenation level-dependent (BOLD) activation decreased in ipsilateral and contralateral motor areas and became more lateralized. BOLD activation decreased also in ipsilateral cerebellar regions and in the SMA. CONCLUSION: Changes in peripheral upper-limb hypertonus after BoNT-A were associated to an improvement in active movements and more lateralized and focalized activation of motor areas. The clinical and EMG-fMRI coregistration technique we used to study hand-muscle hypertonus in patients receiving BoNT-A after chronic stroke should be useful in future studies seeking improved strategies for post-stroke neurorehabilitation

Steady-state activation in somatosensory cortex after changes in stimulus rate during median nerve stimulation

Passive electrical stimulation activates various human somatosensory cortical systems including the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII) and bilateral insula. The effect of stimulation frequency on blood oxygenation level-dependent (BOLD) activity remains unclear. We acquired 3-T functional magnetic resonance imaging (fMRI) in eight healthy volunteers during electrical median nerve stimulation at frequencies of 1, 3 and 10 Hz. During stimulation BOLD signal changes showed activation in the contralateral SI, bilateral SII and bilateral insula. Results of fMRI analysis showed that these areas were progressively active with the increase of rate of stimulation. As a major finding, the contralateral SI showed an increase of peak of BOLD activation from 1 to 3 Hz but reached a plateau during 10-Hz stimulation. Our finding is of interest for basic research and for clinical applications in subjects unable to perform cognitive tasks in the fMRI scanner

Effect of stimulus rate during median nerve stimulation on bold activity: a 3T fMRI Study

Purpose: Previous findings have shown that the human somatosensory cortical systems that are activated by passive nonpainful electrical stimu- lation include the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII), and bilateral insula. The present study tested the hypothesis that these areas have different sensitivities to stimulation frequency in the condition of passive stimulation. Methods: fMRI was recorded in 8 normal volunteers during nonpainful electrical median nerve stimulations at 1, 3, and 10 Hz repetition rates in separate recording blocks in pseudorandom order. Results: Results of the blood oxygen level-dependent (BOLD) effect showed that the contralateral SI, the bilateral SII, and the bilateral insula were active during these stimulations. As a major finding, only the contralateral SI increased its activation with the increase of the stimulus frequency at the mentioned range. Conclusion: The present method of this study may be useful for presurgical functional mapping of primary somatosensory cortex and for the study of its plastic reorganization following tumor resection or stroke lesions