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Biomedical subjects

M R Nuwer

Publications and source records attributed to M R Nuwer.

At least 55 records · Page 3Linked to original sources
PubMed1993

Monitoring carotid test occlusions with continuous EEG and clinical examination.

We routinely monitor invasive neuroradiologic carotid balloon test occlusions with continuous polygraph and quantitative EEG along with repeated detailed clinical examinations. Four of 17 consecutive cases showed changes during carotid occlusion. In one instance, an immediate delta increase was accompanied by slurred speech and aphasia. Another showed alpha attenuation without clinical change. A third patient had significant clinical change without EEG change. Nine of the 17 cases underwent permanent therapeutic carotid occlusion as treatment of an intracerebral vascular abnormality. Seven of these nine had no EEG or clinical changes during monitoring and have had no functional abnormalities on follow-up. The patient with focal alpha attenuation had an accidental balloon detachment but has had no functional or structural neurologic abnormalities. The patient with minor regional increased delta received a permanent carotid occlusion and went on to develop clinical signs 24 h later. We believe that continuous EEG monitoring and repeated clinical examinations provide useful ways of evaluating cerebral circulation during carotid test occlusions.

Adult↗
PubMed1993

Intraoperative electroencephalography.

EEG is useful in several operating room procedures. It has come to be a standard part of monitoring patients during carotid endarterectomy. Monitoring for cerebral hypoperfusion or emboli can also be done in cardiac surgery or other similar settings. For carotid endarterectomy, studies in humans suggest that the risk of stroke can be reduced 10-fold by selective vascular shunting based on major EEG changes compared to no shunting. EEG can be recorded from exposed cerebral cortex, a technique referred to as electrocorticography. Such recordings can help identify damaged cortex, separating it from normal functioning cortex. This can influence the extent of neurosurgical cortical resections. Although much of the technology in the operating room is based on that common in routine EEG testing, some differences exist and are discussed here. The well-trained electroencephalographer should find recording and interpreting EEG in the surgical setting to be a natural extension of routine EEG.

Brain Ischemia↗
PubMed1993

Guidelines for the recording and quantitative analysis of electroencephalographic activity in research contexts.

Developments in technologic and analytical procedures applied to the study of brain electrical activity have intensified interest in this modality as a means of examining brain function. The impact of these new developments on traditional methods of acquiring and analyzing electroencephalographic activity requires evaluation. Ultimately, the integration of the old with the new must result in an accepted standardized methodology to be used in these investigations. In this paper, basic procedures and recent developments involved in the recording and analysis of brain electrical activity are discussed and recommendations are made, with emphasis on psychophysiological applications of these procedures.

Action Potentials↗
PubMed1993

Magnetoencephalographic localization of a language processing cortical area adjacent to a cerebral arteriovenous malformation. Case report.

In order to accurately estimate the risk of surgery for dominant perisylvian arteriovenous malformations, the topographical relationship of the lesion to language cortex must be determined. A case is presented in which a magnetoencephalographic (MEG) study was used to map preoperatively and noninvasively an intracortical source of speech-receptive cortex in a 25-year-old right-handed man with a dominant left temporal lobe arteriovenous malformation. The speech-evoked magnetic field was analyzed at 36 positions over the left hemisphere in response to presentations of the consonant-vowel syllables "da" and "ga." A topographical map of the magnetic component evoked at 110 msec after stimulus onset, which was negative going to the vertex in concurrent electrical recordings, was congruent with a superficial cortical neuronal current source. This source was displaced from that usually observed in normal individuals to tonal or click stimuli, being superior to the probable location of auditory cortex, and superior and anterior to the probable location of Wernicke's area as conventionally described. The MEG results were in accord with the determination of position of a language-processing cortical area as assessed by direct electrical stimulation of the cortex during surgery under local anesthesia, and by superselective Amytal (amobarbital) injection during angiography. The MEG recordings and exposed brain stimulation sites were coordinated by cranial measurements, skull x-ray landmarks, and angiographic anatomy. Investigations such as this, which compare MEG findings with those from established clinical procedures, are an essential step in determining the physiological and anatomical utility of magnetoencephalography for noninvasive clinical functional localization.

Adult↗
PubMed1992

Ocular motility anomalies in developmental misdirection of the optic chiasm.

A 35-year-old normally pigmented man underwent monocular hemifield visual-evoked potential examinations that indicated a lack of normal decussation of nasal paramacular retinogeniculate fibers in the optic chiasm. We studied effects of this anomaly on ocular motility using electro-oculography and the magnetic search-coil technique. The patient exhibited horizontal congenital nystagmus with a predominantly positive exponential waveform. Horizontal smooth pursuit and optokinetic nystagmus were consistently reversed, independent of eye position in the orbit. Vertical tracking was uniformly normal. Horizontal vestibulo-ocular reflexes recorded in the dark during passive rotation exhibited normal gain and phase, whereas rotation recorded in the light reduced gain. Although active head movements reversed horizontal vestibulo-ocular reflexes, vertical vestibulo-ocular reflexes in light and darkness were normal. Our study suggested an association between a lack of normal decussation of retinal fibers in the optic chiasm, and reversed visual tracking and congenital nystagmus.

Adult↗
PubMed1992

Topographic mapping of somatosensory evoked potentials helps identify motor cortex more quickly in the operating room.

Median nerve somatosensory evoked potentials were recorded from exposed cerebral cortex during craniotomies. This technique is valuable when knowledge of the motor cortex location can influence surgical decisions about resection limits or biopsy sites. Two different recording techniques were compared: strips of electrodes and arrays of electrodes. The arrays recorded electrical potentials suitable for topographic mapping. We found that motor cortex could be identified more quickly when using the topographic mapping of SEPs from arrays. We conclude that topographic mapping of SEP from sensorimotor regions during craniotomies works well in general and can be done more quickly than the traditional electrode strip technique.

Adolescent↗
PubMed1992

On the process for evaluating proposed new diagnostic EEG tests.

Assessment of new technology is an important part of the evolving art of medicine. For a variety of reasons, it is appropriate to restrict clinical applications of new technology to those tests which have been shown to be safe and effective. Efficacy of new EEG technology can be assessed through a variety of standard procedures, generally based on controlled, well organized clinical studies. Scientific reports using new EEG technology all too often fail to meet the standards traditionally expected for such clinical trials. Many such studies were never designed to be clinical trials. Misunderstandings occur when reports of scientific studies and informal clinical series become confused with formal clinical trials of efficacy. Based upon examples given during the 1991 ISBET meeting symposium on discriminant analysis, examples are discussed regarding how well individual kinds of presentations can be used to help clarify the generic clinical efficacy of the presented diagnostic tests.

Brain↗
PubMed1992

Asymptomatic HIV infection does not cause EEG abnormalities: results from the Multicenter AIDS Cohort Study (MACS)

We conducted EEG testing in 200 asymptomatic homosexual men, half of whom were HIV seropositive. We chose to include half of the subjects because they were rated as impaired on a neuropsychological screening test. We used both traditional visual EEG interpretation and quantitative EEG analysis. Abnormal EEGs and borderline degrees of EEG slowing occurred in 32% of these men. These EEG changes were not related to HIV serostatus. EEG changes did correlate with the impaired neuropsychological test performance. Clinicians faced with abnormal EEG results or borderline EEG slowing in an asymptomatic HIV-seropositive patient should not attribute the EEG change to effects of the serostatus itself but should look for other causes.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Spinal cord monitoring. Results of the Scoliosis Research Society and the European Spinal Deformity Society survey.

The Scoliosis Research Society (SRS) and the European Spinal Deformity Society (ESDS) membership was surveyed regarding the use of intraoperative monitoring of somatosensory evoked potentials in spinal surgery. A total of 242 people responded, with 188 using intraoperative monitoring. A second survey was distributed detailing the technical aspects of monitoring, of which 71 were returned. A total of 342 neurologic deficits were reported to have occurred with monitoring in place. Two hundred forty-six (72%) were accurately detected, and 96 (28%) were not detected by sensory cord evoked potentials (SCEP). There were 1,003 false-positive cases reported. The incidence of false-negative cases was related to those not monitoring both latency and amplitude, to using fewer recording electrodes, and with those surgeons doing more kyphosis corrections.

Europe↗
PubMed1990

On the controversies about clinical use of EEG brain mapping.

Quantitative EEG analysis, often called EEG Brain Mapping, consists of a large variety of separate techniques. Most of these techniques have demonstrated research uses, but few have been shown to have clinical applications that actually impact patient care. Substantial problems exist that can interfere with routine clinical applications. These include a variety of artifacts, confounding clinical problems, diversity of techniques and statistical issues. Existing medical literature suggests several areas where there are clinical uses at this time. EEG Brain Mapping can be used as a testing technique to determine abnormality and perhaps as a monitoring tool, too. It should be viewed as complementary to neuroimaging techniques, rather than a competitor. Those who introduce costly new technology bear the burden of proof for demonstrating its usefulness and cost-effectiveness. Evaluation of new tests should be based on several principles outlined here. EEG Brain Mapping, when used for clinical purposes, should be read together with the accompanying traditional polygraph EEG record. Reproducibility of results should be demonstrated, and artifacts, normal variants and other problems must be identified or avoided. The reader must recognize that features noted on statistical tests do not necessarily imply that pathology exists. Reporting results and clinical implications should be done carefully, thoroughly and with appropriate caution. Results are often quite nonspecific. The user must have skills, knowledge and abilities for reading polygraph EEG as well as additional experience and knowledge about quantitative EEG techniques and problems. Experts must remain careful and responsible about introducing EEG Brain Mapping into routine clinical practice.

Brain↗
PubMed1990

Paperless electroencephalography.

"Paperless EEG" incorporates a variety of techniques for recording, storing, reformatting, transmitting, and analyzing EEG records. The general advance in microelectronics has provided the EEG community with this collection of options. Many of these will come to be commonplace in the EEG laboratory of the future, and indeed some of these are making inroads into EEG practice. Storage of EEG may be the simplest area in which these tools can be used at present, and they may be cost-effective for many laboratories even now. Other features offer ways to improve the EEG product, including the ability to change the filters, paper speed, and montage after the recording has been made. In these ways, even reading of the traditional polygraph EEG can be enhanced by paperless tools. Some other tools are still under development or are best used at specialty centers. Methods of artifact removal, event detectors, and spike detectors still are not quite ready for routine use everywhere, but can now enhance EEG techniques in specific settings. As the field of EEG moves toward the 21st century, the impact of modern electronics should continue to encourage advances toward more widespread use of all of these tools. These advances should help to create an EEG that is cost-competitive with existing services while providing a qualitatively better product.

Brain Mapping↗
PubMed1990

The development of EEG brain mapping.

The field of EEG brain mapping is a collection of many separate techniques for quantified EEG analysis. The most popular technique is the color-coded topographic mapping of frequency content, usually taken in the alert eyes-closed state. This field has developed progressively over 60 years and now is gradually entering use in clinical situations. Accepted clinical uses are still rather limited. A variety of substantial problems exists regarding artifacts, confounding clinical issues, the diversity of available techniques, and statistical interpretation. Clinically, the tests may demonstrate an abnormality but are generally nonspecific regarding the type of responsible pathology. They localize impairment far less well than neuroimaging tests. These digital EEG techniques should not be used separately from the polygraph EEG at this time and should be only used by persons who have sufficient skills, knowledge, and abilities in traditional polygraph EEG interpretation along with additional knowledge and experience in statistical and EEG computer-processing techniques.

Brain↗