EEG instrumentation. The International Federation of Clinical Neurophysiology.
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Electrodes↗
Biomedical subjects
M Nuwer
Publications and source records attributed to M Nuwer.
Somatosensory evoked potentials. The International Federation of Clinical Neurophysiology.
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Aging↗
Standards of clinical practice of EEG and EPs in comatose and other unresponsive states. The International Federation of Clinical Neurophysiology.
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Brain Diseases↗
Positron-emission tomographic study of human amblyopia with use of defined visual stimuli.
PURPOSE: The purpose of this study was to use positron emission tomography (PET) to evaluate effects of amblyopia on cerebral blood flow and glucose metabolism in humans viewing defined visual stimuli and to correlate these effects with specific behavioral and electrophysiologic measures of visual function. METHODS: One subject with normal vision and five patients with amblyopia were prospectively studied. During monocular viewing of a checkerboard reversal stimulus by each subject, we performed PET imaging of relative cerebral glucose metabolism with use of [18F]fluorodeoxyglucose, PET imaging of relative cerebral blood flow with use of H2(15)O, and visual evoked potentials. Control studies were also performed with use of binocular occlusion and during presentation of stationary and horizontally drifting checkerboards. These data were correlated with letter acuities and contrast sensitivity functions for each eye. RESULTS: Although spatial resolution was superior for glucose metabolic imaging, PET readily demonstrated activation of calcarine cortex with use of both metabolic and blood flow tracers. Even in patients with mild amblyopia, functional activation of calcarine cortex was reduced in amblyopic eyes compared with sound eyes to a degree more closely correlated with visual acuity than were visual evoked potential amplitudes to the same stimulus. When responses to drifting versus stationary stimuli were compared, a putative motion processing center was identified in the right temporoparietal region. Activity in this motion center was relatively preserved during viewing of drifting stimuli by the affected eye of an anisometropic amblyopic subject, but was attenuated during viewing of the same stimulus by the affected eye of a strabismic amblyopic subject. CONCLUSIONS: PET imaging of blood flow and metabolism can quantitatively evaluate functional deficits resulting from amblyopia in striate as well as extrastriate visual areas. Calcarine cortical function correlates closely with severity of amblyopia, but function in a putative motion processing area may vary according to the type of amblyopia present.
Adult↗
Assessment of digital EEG, quantitative EEG, and EEG brain mapping: report of the American Academy of Neurology and the American Clinical Neurophysiology Society [RETIRED].
A. Digital EEG is an established substitute for recording, reviewing, and storing a paper EEG record. It is a clear technical advance over previous paper methods. It is highly recommended. (Class III evidence, Type C recommendation). B. EEG brain mapping and other advanced QEEG techniques should be used only by physicians highly skilled in clinical EEG, and only as an adjunct to and in conjunction with traditional EEG interpretation. These tests may be clinically useful only for patients who have been well selected on the basis of their clinical presentation. C. Certain quantitative EEG techniques are considered established as an addition to digital EEG in: C.1. Epilepsy: For screening for possible epileptic spikes or seizures in long-term EEG monitoring or ambulatory recording to facilitate subsequent expert visual EEG interpretation. (Class I and II evidence, Type A recommendation as a practice guideline). C.2. OR and ICU monitoring: For continuous EEG monitoring by frequency-trending to detect early, acute intracranial complications in the OR or ICU, and for screening for possible epileptic seizures in high-risk ICU patients. (Class II evidence, Type B recommendation as a practice option). D. Certain quantitative EEG techniques are considered possibly useful practice options as an addition to digital EEG in: D.1. Epilepsy: For topographic voltage and dipole analysis in presurgical evaluations. (Class II evidence, Type B recommendation). D.2. Cerebrovascular Disease: Based on Class II and III evidence, QEEG in expert hands may possibly be useful in evaluating certain patients with symptoms of cerebrovascular disease whose neuroimaging and routine EEG studies are not conclusive. (Type B recommendation). D.3. Dementia: Routine EEG has long been an established test used in evaluations of dementia and encephalopathy when the diagnosis remains unresolved after initial clinical evaluation. In occasional clinical evaluations, QEEG frequency analysis may be a useful adjunct to interpretation of the routine EEG when used in expert hands. (Class II and III evidence as a possibly useful test, Type B recommendation). E. On the basis of current clinical literature, opinions of most experts, and proposed rationales for their use, QEEG remains investigational for clinical use in postconcussion syndrome, mild or moderate head injury, learning disability, attention disorders, schizophrenia, depression, alcoholism, and drug abuse. (Class II and III evidence, Type D recommendation). F. On the basis of clinical and scientific evidence, opinions of most experts, and the technical and methodologic shortcomings, QEEG is not recommended for use in civil or criminal judicial proceedings. (Strong Class III evidence, Type E recommendation). G. Because of the very substantial risk of erroneous interpretations, it is unacceptable for any EEG brain mapping or other QEEG techniques to be used clinically by those who are not physicians highly skilled in clinical EEG interpretation. (Strong Class III evidence, Type E recommendation).
Brain↗
Perioperative complications in children undergoing selective posterior rhizotomy: a review of 105 cases.
Medical histories for 105 consecutive children who underwent selective posterior rhizotomy (SPR) were reviewed to determine the incidence and clinical significance of adverse events related to anaesthesia and surgery. No intraoperative or postoperative events with potential for lasting morbidity, nor life threatening events, were identified. Intraoperatively, the most common adverse events were moderate elevation of body temperature (13/105) and transient dysrhythmias (8/105). The most frequent postoperative complications were fever, marginal oxygen saturation in the absence of supplemental oxygen, and postcatheterization cystitis. Early surgical complications, such as wound infection, cerebrospinal fluid leak, haemorrhage, and bowel or bladder disturbance were absent in this series. Surgical technique and anaesthetic management are described.
Adolescent↗
Computerized electroencephalography in the evaluation of early dementia.
In elderly patients presenting to an ambulatory practice with complaints of cognitive disturbance, early dementia must be differentiated from depression. The present paper describes the application of standard electroencephalography and evoked potential testing (EEG/EP) and computerized electroencephalography with evoked potential mapping (CEEG/EPM) in the analysis of 64 elderly patients complaining of cognitive disturbance. Although previous reports have claimed a sensitivity level of up to 80% for EEG in demented patients, it appears that a lower sensitivity (37% for EEG alone and 61% for EEG/EP) may be expected at the time of early presentation according to the present study. No EEG/EP abnormalities were detected in patients with depression. In demented patients, CEEG/EPM was abnormal in 85% (46 of 54) of cases compared to 10% (1 of 10) of cases with depression. Specific information was obtained from EEG/EP studies that helped differentiate the various causes of dementia in three cases. In CEEG/EPM studies, a pattern of relative suppression of alpha activity or suppressed auditory P300 amplitude in the posterior parietal regions was observed in 11 or 23 (48%) patients with Alzheimer's disease and 2 of 31 (6%) patients with other forms of dementia. None of the depressed patients demonstrated such changes. Based on the present study, it appears that computerized techniques may hold promise as an adjunct to standard EEG evaluation of patients with mild cognitive change in whom diagnosis of dementia or depression is in doubt. Although standard EEG rarely demonstrates characteristic changes that may help differentiate causes of dementia, CEEG/EPM appears to demonstrate, on occasion, abnormalities in the posterior temporal and parietal regions in patients with a diagnosis of probable Alzheimer's disease and rarely in other forms of dementia or depression.
Acoustic Stimulation↗
Somatosensory evoked potentials in the assessment of thoracic outlet compression syndrome.
To evaluate the assessment of thoracic outlet compression syndrome (TOS) by objective methods, we prospectively studied a group of 80 consecutive patients with disabling TOS who had been selected for surgical therapy. Comprehensive pre- and postoperative neurophysiologic tests were used and included electromyography, nerve conduction times, F wave determination, and somatosensory evoked potentials (SEPs) of median and ulnar nerves in neutral and stressed positions. Measurements were made of Erb's point peak (N9), cervical peak (P/N13), and cortical complex (N18-P22). Amplitude ratios were calculated for each side, and interpeak latencies were measured for N9-P/N13, P/N13-N18, and N9-N18. SEP results were abnormal on the affected side in 59 of 80 patients (74%); ulnar peak amplitudes were either less than 33% of median, reduced by more than 50% in the stressed position, or reduced by more than 50% when compared with the contralateral side. Of 64 patients studied pre- and postoperatively with SEP, 40 of 47 abnormal tests showed improvement, with 30 of these returning to normal values in the early postoperative period. Excellent clinical correlation was evident in 43 of these 47 patients (92%) who had pre- and postoperative tests; with relief of symptoms reflected in improved SEP, or continued symptoms explained by evidence of persistent or residual nerve dysfunction. The present methodology and criteria for test interpretation demonstrate that SEP can document the neurocompressive component of TOS and provide an objective assessment of pre- and postoperative clinical observations.
Action Potentials↗
Bone-marrow transplantation for metachromatic leucodystrophy.
An 11-month-old boy with late infantile metachromatic leucodystrophy was given a bone-marrow transplant (BMT) from an HLA-identical sister; 6 months later his cerebrospinal fluid leucocytes were exclusively of donor origin. Coupled with the patient's continued developmental progress, as assessed 33 months after the procedure, the findings suggest that BMT may be an effective treatment for some congenital metabolic disorders which affect the central nervous system.
Adolescent↗
Facial nerve evoked potentials.
Evoked potentials representing both intracranial and extracranial activity have been recorded from the canine scalp after retrograde stimulation of peripheral facial nerve branches. A negative electrode at the vertex and a positive electrode at the ipsilateral mastoid (grounded at the contralateral mastoid) show a monophasic negative stylomastoid evoked potential that appears to be generated from the facial nerve trunk at the stylomastoid foramen. When the positive electrode is moved from the mastoid to the posterior scalp (overlying the foramen magnum), a similar potential with a latency 1.5 msec greater is obtained. This brain stem evoked potential is generated from fibers in the vicinity of the root entry zone and the initial trajectory into the brain stem. A potential of similar latency but greater magnitude is recorded with the positive electrode in the cerebrospinal fluid of the posterior fossa.
Animals↗
Local cerebral metabolism during partial seizures.
Interictal and ictal fluorodeoxyglucose scans were obtained with positron CT from four patients with spontaneous recurrent partial seizures, one with epilepsia partialis continua, and one with a single partial seizure induced by electrical stimulation of the hippocampus. Ictal metabolic patterns were different for each patient studied. Focal and generalized increased and decreased metabolism were observed. Ictal hypermetabolism may exceed six times the interictal rate and could represent activation of excitatory or inhibitory synapses in the epileptogenic region and its projection fields. Hypometabolism seen on ictal scans most likely reflects postictal depression and may indicate projection fields of inhibited neurons. No quantitative relationship between alterations in metabolism and EEG or behavioral measurements of ictal events could be demonstrated.
Adolescent↗
Tomographic mapping of human cerebral metabolism visual stimulation and deprivation.
Positron computed tomography was used to investigate changes in the local cerebral metabolic rate for glucose (LCMRGlc) of the visual cortex. Progressive increases in LCMRGlc were found from eyes-closed control to stimulation with white light, alternating black/white checkerboard pattern, and a complex visual scene of a park, with the associative visual cortex increasing at a faster rate than the primary visual cortex as the visual scene complexity increased. A graded decrease in LCMRGlc of the visual cortex was found with a stepwise deletion of spontaneous cell firing at the retinal, geniculate and cortical level due to lesions. Left/right metabolic symmetry of the visual cortex during monocular stimulation confirms 50% crossing of the human visual system. Neonatal blindness showed no apparent degeneration of the visual cortex and was equivalent to eyes-closed controls. The interictal state of a patient with visual seizures demonstrated a hypometabolic visual cortex with a 2.5-fold increase in metabolism during an ictal visual hallucination.
Adult↗