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Biomedical subjects

G Pfurtscheller

Publications and source records attributed to G Pfurtscheller.

At least 181 records · Page 10Linked to original sources
PubMed1985

Quantitative EEG study in patients with cerebral ischemia during nimodipine treatment.

In a group of 15 patients with chronic unilateral cerebral ischemia, a quantitative EEG study was performed before, during and after nimodipine (Bay e 9736) infusion (1 microgram/kg/min). The EEG was recorded bipolarly from the rolandic region. After computerized EEG analysis, a multiparametric asymmetry score (MAS) was calculated; this MAS provides a sensitive indicator for discrimination between neurologically normal subjects and patients with unilateral ischemia. A positive MAS is characteristic for healthy subjects, a negative one for ischemia patients. During nimodipine treatment, the MAS became more negative (increased EEG asymmetry) in 7 and less negative (decreased EEG asymmetry) in 8 patients. A correlation was found between the direction of the EEG asymmetry changes and the localization of the infarcted area as seen in the CT scan.

Adult↗
PubMed1984

Multiparametric asymmetry score (MAS)--distinction between normal and ischaemic brains.

A multiparametric asymmetry score (MAS) is presented. It is based on the EEG data of 50 normal subjects and 32 patients with cerebral ischaemia. For the asymmetry measurements, the following parameters appeared to be the most powerful in the given order: the ratio theta/beta power, the peak frequency, absolute delta and theta powers and the ERD in the alpha band. The EEG data were recorded during rest and during voluntary hand movements from the centro-temporal regions. As the MAS can be calculated with or without the peak frequency parameter, it is applicable to all types of EEG data. Using the MAS, 94% of the normal and 92% of the patient data were correctly classified. From the patient group, 6 were without neurological deficits and 9 had 'normal' clinical EEGs.

Discrimination, Psychological↗
PubMed1983

Quantification of spindles in comatose patients.

Quantification of spindles in comatose patients is easily possible by measurement of ERD (event-related desynchronization). ERD can either be positive (e.g., alpha blocking or alpha attenuation) or negative (spindle activity within the alpha band) or can be missing. Follow-up measurements in a comatose patient demonstrate the different time courses of VEP (visual evoked potential) and ERD during clinical recovery. That means that VEP and ERD are generated by different neuronal systems as reactions to the same external stimulus.

Brain↗
PubMed1983

Frequency changes of sensorimotor EEG rhythm after revascularization surgery.

In a group of 26 patients undergoing extra-intracranial arterial bypass surgery (EIAB), the frequency of sensorimotor rhythms was measured shortly before and 7 days after EIAB surgery. Bipolar EEG recording from both central regions was used for calculation of power spectra and measurement of peak frequency to determine the dominant frequency of the sensorimotor rhythm. Preoperative hemispheric comparisons displayed a statistically significant frequency decrease (-0.47 Hz) on the ischaemic side, only in the group (15 patients) with cortical infarction. The hand pressure, measured electronically, showed a tendency to decrease in the early postoperative stage. Measurement of the frequency, however, showed a significant decrease of -0.35 Hz on the operated side, only in the group with cortical infarction, whereas no frequency decrease was found in the other group. This unilateral postoperative frequency decrease in patients with cortical infarction is interpreted as a temporary deterioration of brain function.

Brain↗
PubMed1983

Simultaneous measurement of auditory brain stem potentials and EEG spectra.

Compressed EEG spectra and compressed brain stem auditory potentials (BAEP) can be measured at the same time, from the same derivation, if a wide band amplifier (1 Hz-2 kHz) is used and the complete brain stem signal is sampled between two EEG sampling points. For this approach sample rates of 64 Hz for the EEG and 12,800 Hz for the BAEP were used. The auditory stimulation was repeated every 6th EEG sampling point, corresponding to a repetition rate of 10.6 Hz. Processing and presentation of the results were performed on-line, permitting continuous monitoring of the patient.

Brain Stem↗
PubMed1983

[Computer assisted analysis of EEG, evoked potentials, EEG reactivity and heart rate variability in comatose patients].

A multifunctional system for combined evaluation of EEG, visual (VEP), somatosensory (SEP) and auditory brainstem evoked potentials (BAEP) is introduced. For the light stimulation an array of light emitting diodes are used for tactile stimulation a vibration stimulus is applied to he distal digit of one finger. Stimulus-synchronous EEG segments are used for EP averaging and also for quantification of either the blocking or the activation of rhythmic EEG activity. Using this technique, alpha spindles characteristic of certain comatose states can be quantified for the first time. An important parameter is the alpha frequency, which is slowed down when there is evidence of cortical lesions, but remains unchanged in primary brain stem lesions. Comparing SEP and VEP also allows for differentiation of brain stem lesions from lesions in other areas. VEP were found to be maintained in predominant brain stem disorders. The auditory brain stem potentials and the heart rate variability are of further diagnostic significance. The importance of the individual parameters such as alpha-frequency, VEP, SEP, BAEP and alpha-spindles is demonstrated by follow-up studies in comatose patients.

Alpha Rhythm↗
PubMed1982

The influence of skull defects and reperfusion after extra-intracranial arterial bypass surgery on the sensorimotor EEG rhythm.

Twelve patients with small burr hole skull defects after extra-intracranial arterial bypass surgery were studied. The amplitude and frequency of the sensorimotor rhythm were measured 7 days and 1, 2, 4, and 6 months after surgery in follow-up EEGs from the central region. Seven patients showed a frequency decrease (compared with preoperative measurement) on the operated side 7 days and/or 1 month after surgery. There was no case of frequency decrease 6 months after surgery; four patients displayed a late frequency increase. Ipsilateral amplitude enhancement was never found 7 days postoperatively, but after 6 months in nine patients. Such physical factors as burr holes and bone replacement can only partially explain the amplitude enhancement, and cannot explain the frequency decrease. It may be assumed that temporary clamping of the middle cerebral artery and/or reperfusion of an ischaemic area result in a brief deterioration of brain function, as indicated by frequency slowing and delayed amplitude enhancement; related observations were made in patients with cerebrovascular disorders and mild to moderate neurological deficit about 20 days after the onset and correlated with clinical recovery.

Adult↗
PubMed1981

Correlations between CT scan and sensorimotor EEG rhythms in patients with cerebrovascular disorders.

Fifty subjects with cerebrovascular disorders and motor deficits, all able to perform a voluntary hand movement and aged between 33 and 78 years, were involved in this study. CT scan and computerized analysis of sensorimotor rhythms (mu rhythm and central beta rhythm) were performed for all patients. From the mu rhythm, the hemispheric asymmetry in amplitude and ERD during movement (ERD = event-related desynchronization) was measured and referred to a group of 38 neurologically normal subjects. Comparisons of CT scan data and EEG findings indicate a high correlation between morphological and functional findings. This correlation can be used to predict the localization of a lesion in the territory of the middle cerebral artery (MCA) based only on the amplitude and reactivity pattern of the mu rhythm. Thus, for example, an ipsilaterally enhanced mu rhythm in connection with a symmetric ERD indicates with a probability of 95% a deep, and with only 5%, a superficial lesion. Hemispheric mu amplitude symmetry and asymmetric ERD indicate a superficial cortical ischemia with a probability of 81%. An ipsilaterally attenuated mu rhythm accompanied by an asymmetric or abolished ERD indicates with 62% and 55%, respectively, a large extension of the infarct over the whole territory of the MCA.

Adult↗
PubMed1981

Central beta rhythm during sensorimotor activities in man.

Blocking or desynchronization of the central beta rhythm prior to and parallel to voluntary movement was found in 31 of 33 normal subjects investigated. The beta blocking was short lasting (1-3 sec), very often accompanied by blocking of the mu rhythm and localized in the central region. Phasic beta desynchronization was also observed after somatosensory stimulation. The beta rhythm showed a bilateral symmetrical blocking pattern with unilateral movement or stimulation. Patients with unilateral cerebral ischaemia showed an asymmetric blocking response and therefore demonstrated a high degree of hemispheric independence of the rhythmic generating systems. Central beta desynchronization is, therefore, a normal physiological phenomenon caused by activation processes of the sensorimotor cortex and detectable on the scalp very easily with closely spaced electrodes.

Beta Rhythm↗
PubMed1981

[An automatic method for analysis of the electroencephalogram of epileptics (author's transl)].

A new method for spike-detection in the EEG was developed. For the learning, and test-phase of the program the judgement of 7 experienced electroencephalographers was used. The EEGs of 10 epileptic patients and 9 clinically normal subjects were analyzed. 250 out of 341 "true" spikes were recognized and only 3 doubtless nonspikes were classified as spikes. A direct comparison between computer program and single EEG experts shows an equivalent in 3 of 7 cases. The average detected spike rate of non=epileptic subjects is a quarter of the average spike rate of the epileptic patient with the lowest epileptic activity. The program is now being tested in realtime in a centre for epilepsy in the Netherlands.

Computers↗