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Biomedical subjects

M R Nuwer

Publications and source records attributed to M R Nuwer.

At least 91 records · Page 5Linked to original sources
PubMed1985

Evoked potential testing in relatives of multiple sclerosis patients.

Evoked potential (EP) tests were obtained in 110 neurologically normal first-degree relatives of patients with multiple sclerosis. Visual EP tests were performed in all relatives; brainstem auditory and median nerve somatosensory EP tests were performed in 67 relatives. The relatives had a mean visual EP P100 latency that was significantly longer than that for normal subjects controlled for age and gender. Asymmetries were seen in results from individual MS relatives, including interocular visual EP P100 differences of up to 14 ms, and interarm somatosensory Erb-N18 differences of up to 3.0 ms. We identified 19 pairs of patients and relatives who were HLA identical and 18 other pairs who were HLA double nonmatched. EP asymmetries were seen more often in the HLA identical siblings than in the HLA double patients, especially if they share HLA types with the patients. Since less than 2% of siblings of MS patients would be expected to eventually develop clinical MS, these small subclinical electrophysiological changes are not expected to be a sign of the future appearance of clinical MS. Clinicians should be aware not to overinterpret small EP changes in relatives of MS patients.

Adolescent↗
PubMed1985

A comparison of the analyses of EEG and evoked potentials using colored bars in place of colored heads.

Multichannel EEG and evoked potentials can be re-represented as collections of colored bars, with each bar corresponding to a line of data. These colored bars can be assembled into montages, just like conventional lines of data. Changes in potentials can be followed over space and time by visual inspection of patterns of color. Analogous montages of colored bars can be made with power spectra of EEG and evoked potentials. Colored bars can be visually analyzed more quickly than collections of colored heads, whether or not the heads are cartooned.

Color↗
PubMed1985

Monitoring at the University of California, Los Angeles.

Long-term EEG monitoring with radio or cable telemetry and video recording can be performed efficiently as an organized team effort involving physicians, nurses, technologists and other ancillary personnel. We use telemetry primarily for screening patients for possible surgical treatment of partial epilepsy. The technique is also used occasionally to define better the patient's type(s) of seizures or to differentiate seizures from pseudoseizures. Important technical points include precise correlation of EEG with clinical events, choice of recording montage, use of a 1 Hz low filter, and use of sphenoidal electrodes. Patients may need to be stressed, exercised or have medications reduced to bring about a sufficient number of seizures during monitoring. Care is needed to avoid or to identify atypical seizures due to medication withdrawal.

California↗
PubMed1984

Intraoperative evoked potential monitoring of the spinal cord: enhanced stability of cortical recordings.

Intraoperative EP monitoring of spinal cord function depends upon a quickly obtained, reproducible EP. The records must be obtained in a hostile environment where artifacts and other sources of electrical noise cannot easily be eliminated: records are obtained continuously without interrupting the surgery. We studied EP reproducibility by measuring cortical EP amplitude range and latency range within individual patients. Reproducibility was enhanced by several changes in the stimulus and recording parameters: (1) Bipolar recording near the vertex (Cz-Pz, E1-E2) eliminated a significant amount of the artifacts and random variations seen in referential recordings. Bipolar recordings sacrifice some amplitude but the improved reproducibility is worthwhile. (2) Restricted filters (especially 30-3000 Hz) improve reproducibility still further, compared to the traditional open filters (1-1000 Hz). (3) Fast stimulation rates improve monitoring up to rates of about 5 stimuli/sec. At even faster rates too much amplitude attenuation usually occurs. Using these techniques stable intraoperative EPs were recorded from all 115 patients except those in whom EPs were abnormal even before surgery. Advantages and disadvantages compared to epidural recording techniques were discussed. Several further observations were made, including (1) monitoring could be done equally as well with stimulation either at the peroneal or at the posterior tibial nerve; (2) balanced nitrous oxide and narcotic anesthesia did attenuate EPs by about 60%, although this is not so much as to interfere seriously with monitoring.

Adolescent↗
PubMed1984

Intraoperative evoked potential monitoring of the spinal cord. A restricted filter, scalp method during Harrington instrumentation for scoliosis.

Intraoperative monitoring of somatosensory evoked potentials (EPs) can improve the margin of safety during surgery around the spine. Several methods are available. The authors report their experience in monitoring 65 patients who underwent Harrington instrumentation and spinal fusion for correction of scoliosis. They studied the effects of changes in stimulating and recording parameters, seeking ways to reduce noise and variability in the EP signal. The authors were able to improve the quality of the monitoring records significantly by closer spacing of the scalp electrodes, bipolar rather than referential recording, faster rates of stimulation, and greater low-frequency filtering. The technique seems to be safe, easily performed, reproducible, and relatively inexpensive. It has produced no false-negative results to date, and it significantly reduced the incidence of false-positive results (false alarms) as compared with previously described techniques.

Adolescent↗
PubMed1983

Evoked potential abnormalities in the various inherited ataxias.

Visual (VEP), brainstem auditory (BAEP), and somatosensory (SEP) evoked potential tests were performed in 45 patients representing ten types of inherited disorders in which ataxia was the most prominent symptom. Comparable VEP abnormalities were present among all types of patients. Normal BAEP tests were recorded in most patients except those with olivopontocerebellar atrophy. SEP results were often more severely abnormal in patients with Friedreich's ataxia. The observations emphasize the similarity in expression of different metabolic-degenerative disorders. When these tests are used clinically, certain features of evoked potentials (especially left-right symmetry) are typical of the inherited ataxias as a group. Few distinguishing features differentiate the individual disorders.

Ataxia↗
PubMed1982

Evoked potential instrumentation, methodology and theory.

Evoked potentials are the electrical potentials of the nervous system which can be evoked by brief stimulations with lights, noises, or other means. Testing for these has become routine in certain settings in neurology. A wide variety of types of such tests are available. The technique usually involves stimulation of the patient with a standardized light, earphones or nerve stimulator. Recordings are taken from the scalp or other sites, and averaged over many separate stimulations. A good working knowledge of the equipment is needed for proper recording and interpretation of these tests. This article reviews the instrumentation, methods and theory behind clinical evoked potentials.

Amplifiers, Electronic↗
PubMed1981

Somatosensory evoked potential testing in multiple sclerosis.

Evoked potentials can be elicited by electrical stimulation of the median nerve or other locations. Recordings can be made of the electrical signals at the peripheral nerve, plexus, spinal cord, brainstem, and hemispheric levels. When the stimulation and recording techniques are kept constant, the evoked potentials can be used to measure pathophysiological abnormalities in MS and other conditions. Evoked potentials are abnormal in most persons with MS, which helps to establish the diagnosis. These techniques also hold promise of value in clinical trials of possible MS therapies and as an aid in the epidemiological and genetic studies of MS.

Electric Stimulation↗
PubMed1979

Role of the inferotemporal cortex in visual selective attention.

Electrocortical recordings were made from monkeys performing in a multidimensional visual task. Wave forms dependent on the stimulus presented (irrespective of task required) were recorded immediately following the stimulus primarily from electrodes implanted in the striate and prestriate cortex. Wave forms dependent on the panel pressed (irrespective of the stimulus or of the task) were recorded especially from motor and post-central cortex, and to a lesser extent in anterior frontal cortex, always just prior to or following the time of the response. Wave forms dependent on the task as determined by the reinforcing contingencies (but independent of the particular stimulus presented or the particular panel pressed) were recorded primarily from the inferior temporal cortex, and rarely from prestriate and anterior frontal cortex. While task-related wave forms began to appear shortly after stimulus presentation, they became especially apparent around the time of the response. This response-linking increased in prominence as the subject achieved 90% proficiency in each task, only to drop off with overtraining. Further, the task-related wave form does not change as rapidly as does overt behavior when the reinforcement contingency is shifted from one stimulus dimension to another. The relevance of these results to an understanding of the process of selective attention is discussed.

Animals↗
PubMed1972

In vivo release of previously cleared interferon by cycloheximide.

The release of previously cleared interferon by cycloheximide was studied in the mouse. When cycloheximide was administered after either endogenous interferon stimulation or administration of exogenous interferon, the clearance of interferon from the blood stream was interrupted and a sharp rise in interferon titer occurred approximately 6 hr after cycloheximide administration followed by a rapid decline to low levels. This effect was observed with either interferon stimulated endogenously (by polyriboinosinic.polyribocytidylic acid), or homologous (mouse) or heterologous (rabbit) interferon administered exogenously. Serum protein concentrations also exhibited this rise and fall phenomenon after cycloheximide administration although the magnitude of the change in protein concentrations was less pronounced than that observed with interferon. Hematocrits, although elevated in mice receiving cycloheximide, did not exhibit this rise and fall phenomenon. Hence, cycloheximide administration leads to the release into the circulation of previously cleared interferon as well as other proteins.

Animals↗
PubMed1970

Potentiating Effect of Freund's Adjuvant on Interferon Production by Endotoxin or Poly rI*Poly rC.

Intraperitoneal injection of mice with mineral oil, incomplete (IFA) or complete Freund's adjuvant (CFA) increased the interferon response to endotoxin or (poly rI)*(poly rC) administered intravenously 2 days later. After endotoxin administration, circulating interferon titers were increased at several different times of sampling and with a variety of endotoxin dosages. When injection of endotoxin was delayed until 6 to 8 days after the administration of IFA or CFA, interferon production was markedly decreased. Mice treated with CFA and injected with endotoxin 2 days later became more resistant to intranasal vesicular stomatitis virus challenge than mice injected with endotoxin alone. Hyporeactivity to the interferon-inducing capacity of a second injection of endotoxin 2 days after the first injection could not be overcome by administering CFA simultaneously with the first dose. CFA treatment not only raised the serum interferon titers produced by endotoxin, but also increased the number of interferon-forming cells in the spleen after administration of endotoxin in vivo. In addition, CFA enhanced the intravascular clearance of (poly rI)*(poly rC). The possibility that Freund's adjuvant increased the interferon response to endotoxin and (poly rI)*(poly rC) by stimulating the uptake and processing of the interferon inducer by lymphoreticular cells is discussed.

Journal Article↗
PubMed1970

The role of interferon in the protective effect of a synthetic double-stranded polyribonucleotide against intranasal vesicular stomatitis virus challenge in mice.

Intravenous injection of polyinosinic acid/polycytidylic acid [(poly rI).(poly rC)] offered significant protection against intranasal challenge of young mice with vesicular stomatitis virus (VSV). Optimal protection was obtained when a single dose was administered 2 hr before virus challenge, but repeated doses were effective when started as late as 3 days after virus challenge. The therapeutic ratio or ratio of maximum tolerated dose to minimum effective dose for a single intravenous injection of (poly rI).(poly rC) 2 hr before virus inoculation was >/=8 mg/kg:0.004 mg/kg or >/=200.Dose-response curves for interferon production and antiviral protection by (poly rI).(poly rC) were closely parallel. Equivalent doses of poly rI or poly rC alone did not exert any interferon-inducing capacity or protective effect on intranasal VSV challenge. Several factors, which are known to potentiate or antagonize interferon production, increased or decreased the interferon-inducing capacity and antiviral protection of either (poly rI).(poly rC) or maleic acid/divinyl ether copolymer (MA/DVE) in parallel. Interferon production and antiviral protection by MA/DVE were enhanced by arginine but abolished by prior treatment with MA/DVE; DEAE-dextran (intraperitoneally), kinetin riboside and isopentenyladenosine, and prior injection of endotoxin reduced both interferon production and antiviral protection by (poly rI).(poly rC). Treatment with exogenous interferon in amounts which closely mimicked the levels of circulating interferon produced endogenously by an effective dose of (poly rI).(poly rC) gave protection against intranasal VSV which was identical with that dose of (poly rI).(poly rC). This strongly suggests that interferon production accounts for the whole protective effect of (poly rI).(poly rC) in the intranasal VSV assay.

Animals↗