Muscle & nerve. Supplement最新文献

The aim of this study was to describe the outcome of patients with critical illness polyneuropathy (CIP). Twenty-six patients with CIP were studied to determine the clinical and electrophysiological profile 13-24 months after the onset of CIP. Seven patients refused to participate in the study; 6 patients died within the 1st year. Eleven of the 13 survivors showed clinical evidence of polyneuropathy. Five of these patients also had mononeuropathies, including peroneal and ulnar nerves. The quality of life was markedly impaired in all patients. Nerve conduction studies, including limb motor and sensory nerve conductions, bilateral phrenic nerve onset latencies, and bilateral diaphragmatic compound muscle action potentials, were abnormal in all patients. Incomplete recovery within 1-2 years after the onset of disease occurs frequently in patients with CIP.

Transcranial magnetic stimulation (TMS) is a safe, noninvasive, and painless way to stimulate the human motor cortex in behaving human subjects. When it is applied as a single-pulse, measurements such as central conduction time, motor threshold, silent-period duration, recruitment curve, and mapping of muscle representation can be determined. Paired-pulse TMS is a useful way to examine cortical excitability. Single and paired-pulse TMS have been applied to study plasticity following amputation and cortical excitability in patients with dystonia. Another form of TMS is repetitive TMS (rTMS), with stimuli delivered repeatedly to a single scalp site. High-frequency rTMS can be used to transiently inactivate different cortical areas to study their functions. rTMS can also modulate cortical excitability. At stimulus frequencies higher than 5 Hz, rTMS increases cortical excitability, and stimulation around 1 Hz reduces cortical excitability. Modulation of cortical excitability by rTMS has therapeutic potential in psychiatric and neurological disorders.

Recent studies support the long-standing hypothesis that continuous arm movements consist of overlapping, discrete submovements. However, the cortical activation associated with these submovements is unclear. We tested the hypothesis that electroencephalography (EEG) activity would more strongly correspond to the particular combinations of muscle electrical activity, the independent components (ICs) of surface electromyography (EMG), than the surface EMG from individual muscles alone. We examined data recorded from two normal subjects performing sustained submaximal contractions or continual, unpaced repetitive movements of the arm. Independent component analysis (ICA) was used to determine the ICs of the multichannel EMG recordings (EMGICs). ICA was also used to calculate the coupling between the simultaneously recorded EEG and the EMG from a single muscle (Subject 1) or the EMGICs (Subject 2). The EMGICs were either tonic or phasic. The significant couplings between the EEG and the EMGICs were different for each EMGIC. The distribution on the scalp of the coupling between the EEG and tonic EMGICs and those of the single-muscle EMG were similar and followed topographic patterns in sensorimotor regions. Couplings between the EEG and phasic EMGICs were bifrontal, lateral, and bioccipital and were significantly stronger than the coupling between a single muscle's EMG and the EEG (p < 2 x 10(-5)) or another EMG combination derived from principal component analysis. These preliminary results support the notion that electrophysiological cortical activations are more significantly related to the ICs of muscle activations than to the activations of individual muscles alone.

The recognition of uncommon pediatric motor unit disorders or unusual clinical presentations of common illnesses, such as Guillain-Barré syndrome (GBS), have increased the need for electromyography (EMG) in childhood critical care units. There are two different clinical sets, one appropriate to newborns and infants and the other to older children. Some illnesses that present as an acute floppy infant are not found in the differential diagnosis of motor unit disorders in the older child or adult. These include spinal muscular atrophy, postvaccine poliomyelitis, intrauterine GBS, infantile botulism, and severe myopathies, such as myotonia dystrophy, and some glycogen storage diseases. An appreciation of the neurophysiological maturational norms is essential to an effective pediatric EMG consultation for children ages 0-3 years. Additionally, the neuromuscular complications of extended intubation and sepsis in children are gaining broader recognition. An increased dialogue between clinical neurophysiologists and pediatric neurologists and intensivists in both neonatal and pediatric intensive care units is essential.

We recorded the late electromyographic (EMG) responses to predictable and unpredictable stretches of the wrist flexor and extensor muscles during ballistic movement or isometric contractions. We simultaneously recorded the accompanying cerebral responses. Our findings suggest that the late EMG responses are influenced by suprasegmental (cerebral) phasic mechanisms that seem to have a dual functional role, being involved in the control of limb stiffness and in a servomechanism to return the displaced limb to its intended position.

Recent advances in clinical neurophysiology have made it possible to non-invasively stimulate single motor axons and determine the physiological characteristics of the associated motor units. Some motor units lend themselves to longitudinal studies of their electrical and contractile characteristics. The former include the conduction velocities of their motor axons and the sizes and shapes of their motor unit action potentials and the latter such contractile characteristics of the motor unit as their contractile speeds, twitch and tetanic tensions, and resistance to fatigue. The feasibility of serially examining the same motor unit has made it possible to study the responses of single motor units to conditioning as well as changes in the responses of single motor units to diseases such as amyotrophic lateral sclerosis. The non-invasive character of these approaches offers an attractive means of studying the responses of single human cells, in these cases motor neurons, in health and disease.

Local events in the milieu of injured peripheral nerve trunks may have an important influence on the likelihood of regenerative success or the development of neuropathic pain. Injury-related changes in the microcirculation of this milieu have provided some evidence that axonal endbulbs, structures that form at the proximal end of transected axons, dump peptides and other molecules into the injury milieu where they may exert local actions, including those on microvessels. During a later phase of nerve repair, macrophage influx and pancellular proliferative events appear to develop in a coordinated fashion. Nitric oxide is probably an important and prominent player in the injured nerve trunk, both at early and later stages of the repair process. A better understanding of the injured peripheral nerve microenvironment may allow therapeutic approaches that can enhance regeneration and diminish pain.