Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology
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Subcortical infarcts are most commonly the consequence of perforating artery occlusion and pure motor deficit is the most frequent syndrome resulting from an interruption of the corticospinal tract at the level of the corona radiate, the internal capsule or the brainstem. Motor evoked potential (MEP) monitoring is used as an adjunct to surgery as somatosensory evoked potentials (SEP) have been found to be insensitive to these lesions. Two different techniques have been used for monitoring MEPs during aneurysm surgery: transcranial electrical stimulation (TES) and direct cortical stimulation (DCS). ⋯ However, this technique also has disadvantages including subdural bleeding and injury to the brain. Using close-to-motor-threshold stimulation and focal stimulating electrode montages, TES and DCS MEPs do not vary significantly in their capacity to detect lesions of the motor cortex or its efferent pathways. Both techniques are prone to interference by anesthetic agents.
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The aim of this review is to present the status of electrodiagnostic standards and guidelines in neuromuscular disorders. Electrodiagnostic guidelines are developed on the background of medical technology assessment, wherefore a short presentation of medical technology assessment is given covering: (1) Evidence-based medicine, i.e. "to do the right thing", describing practice parameters and the STARD initiative which introduces evidence-based medicine in electrodiagnostic medicine, (2) Continuous quality improvement, i.e. "to do the thing right", describing variation among laboratories in methods and interpretation of tests, and the need for medical audit and implementation of electrodiagnostic guidelines, (3) Outcome studies, i.e. "is it worthwhile to do the right thing right?". In electrodiagnostic medicine there are very few outcome studies. ⋯ If no electrodiagnostic criteria for a given disorder exist, criteria for the electrodiagnostic examination are described if present. It is concluded that future research is needed in order to develop more electrodiagnostic guidelines in neuromuscular disorders by international expert consensus groups. Such research should use an evidence-based medicine approach and medical technology assessment and include continuous quality development and outcome studies.
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Propofol is an emulsion formulation of 2,6 diisopropylphenol developed in 1975. Widely recognized, it offers beneficial effects compared with other sedative drugs. ⋯ Since technological advances over recent years have allowed an ever-increasing number of patients undergoing propofol therapy to be monitored by using continuous digital EEG, it is important to have a complete understanding of the effects of propofol on EEG in diverse clinical scenarios. This paper presents a review of the effects of propofol in electroencephalograms and discusses proconvulsive, anticonvulsive proprieties and the EEG findings in different medical conditions.
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Repetitive transcranial magnetic stimulation (rTMS) of the human motor cortex can produce long-lasting changes in the excitability of the motor cortex to single pulse transcranial magnetic stimulation (TMS). rTMS may increase or decrease motor cortical excitability depending critically on the characteristics of the stimulation protocol. However, it is still poorly defined which mechanisms and central motor circuits contribute to these rTMS induced long-lasting excitability changes. We have had the opportunity to perform a series of direct recordings of the corticospinal volley evoked by single pulse TMS from the epidural space of conscious patients with chronically implanted spinal electrodes before and after several protocols of rTMS that increase or decrease brain excitability. These recordings provided insight into the physiological basis of the effects of rTMS and the specific motor cortical circuits involved.
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Among the alternatives to drugs in the treatment of neurological and psychiatric disorders, neuromodulation techniques, including brain stimulation, have been used increasingly this past decade. Cortical targets are especially appealing, because they are easily accessible by noninvasive or invasive methods. Applicable techniques include repetitive transcranial magnetic stimulation (rTMS), transcranial electrical stimulation using pulsed or direct current, and epidural cortical stimulation (ECS) with surgically implanted electrodes. ⋯ In addition, various parameters of stimulation (such as stimulation frequency, intensity, or electrode polarity) and the configuration of the induced electrical field greatly influence the nature of the recruited circuits, and therefore, the overall efficacy. Finally, clinical changes may be delayed and prolonged beyond the time of stimulation, complicating programming algorithms in the case of implanted stimulation device. All these features need to be taken into account when considering cortical stimulation as a method of treatment.