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Biomedical subjects

M Kollar

Publications and source records attributed to M Kollar.

10 recordsLinked to original sources
PubMed2002

EEG analysis with simulated neuronal cell models helps to detect pre-seizure changes.

OBJECTIVES: To test if a method for real-time detection of epileptic seizures based on electroencephalographic (EEG) analysis with simulated neuronal cell models can be modified to identify pre-seizure changes. METHODS: Our EEG analysis method consists of two simulated leaky integrate and fire units (LIFU) connected to a signal preprocessing stage that marks parts of the EEG signals with slopes larger than a preset threshold Hth with unit pulses. The LIFUs change their spiking frequency depending on the rate and the synchrony of the impinging pulse trains. Here, we use our method in a high-sensitivity mode by setting Hth to low values, which causes the LIFUs to continuously spike during the interictal state. We test if the LIFUs spiking rates change before seizure onset. RESULTS: We used 9 long-term EEGs (16+/-7 h) of 7 patients with drug resistant epilepsy. Fifteen seizures were analyzed and all were preceded by an increase of the time-averaged spiking rates SR(av) of the LIFUs. We defined a function F(Sz), which quantifies the changes of SR(av). F(Sz) increased and stayed above an individually set and fixed threshold 83+/-91 min (range: 4-330 min) before EEG seizure onset. Only two false alarms occurred. CONCLUSIONS: We conclude that EEG analysis with simulated neuronal cell models may be used to detect pre-seizure changes with high sensitivity and specificity.

Adolescent↗
PubMed2001

Hyperperfusion of anterior cingulate gyrus in a case of paroxysmal nocturnal dystonia.

The authors report the clinical, EEG, and SPECT findings of a patient with nocturnal paroxysmal dystonia. Ictal and interictal scalp EEG showed epileptiform activity over both frontal lobes. Subtraction ictal SPECT co-registered to MRI indicated a bilateral significant hyperperfusion in the anterior part of the cingulate gyrus. These results support earlier electrophysiologic investigations by others suggesting that anterior cingulate epilepsy may manifest as nocturnal paroxysmal dystonia, and illustrate the usefulness of computer-assisted SPECT analysis.

Adult↗
PubMed2001

Using simulated neuronal cell models for detection of epileptic seizures in foramen ovale and scalp EEG.

OBJECTIVE: To demonstrate a novel approach for real-time and automatic detection of epileptic seizures in EEG recorded with foramen ovale (Fov) or scalp electrodes. METHODS: Our seizure detection method is based on simulated leaky integrate and fire units (LIFU), which are classical simple neuronal cell models. The LIFUs are connected to a signal preprocessing stage and increase their spiking rates in response to rhythmic and synchronous EEG signals as typically occur at the onset and during seizures. RESULTS: We analyzed 22 short-term (10+/-3 min) and 4 long-term (18+/-7 h) Fov or scalp EEGs of 10 patients with drug resistant partial epilepsy. Seizures (n=36) were marked by increases of the LIFUs spiking rates above a preset threshold. The durations of increased spiking rates due to seizures were always longer than 10 s (36+/-21 s) and allowed separation from artifacts, which caused only short durations (1.2+/-0.6 s) of high spiking rates. The LIFUs correctly detected all the seizures and produced no false alarms. In the long term Fov EEGs seizure detection occurred before the onset of clinical signs (41+/-22 s). CONCLUSIONS: By using simulated neuronal cell models it is possible to automatically detect epileptic seizures in scalp and Fov EEG with high sensitivity and specificity.

Action Potentials↗
PubMed1999

Rotatory seizures in a patient with tuberous sclerosis.

We present an 11-year-old girl with tuberous sclerosis who developed seizures characterized by circling behavior. Rotatory seizures are uncommon and occur mainly secondary to a focal pathology. Our patient had a right temporal epileptic focus, confirmed by magnetic resonance imaging (MRI) to be a subcortical lesion in the right temporal region. This case is probably the first reported case of tuberous sclerosis associated with rotatory seizures with an ictal EEG.

Brain Mapping↗
PubMed1978

Perfusate oncotic pressure during cardiopulmonary bypass. Optimum level as determined by metabolic acidosis, tissue edema, and renal function.

Current practice with respect to the use of a dilutional prime for cardiopulmonary bypass (CPB) varies widely, and the safe lower limit of perfusate protein content has not been defined. We studied this question in 75 rabbits subjected to a 1-hour CPB with a perfusate colloid osmotic pressure (COP) ranging from 26 to 4 mm Hg. Metabolic acidosis was inversely related to COP; acid-base equilibrium is thus best maintained with a high perfusate protein content. Tissue edema rapidly increased at COP levels below 16 mm Hg, i.e. with a protein level less than 4.2 g%. Urinary excretion during CPB was antagonized by the COP, the reason being that glomerular filtration rate was proportional to the difference between perfusion pressure and COP. The safety margin for renal function during CPB thus widens with a decreasing perfusate protein content. We conclude that the optimum levels of perfuste oncotic pressure and protein content during experimental cardiopulmonary bypass are 16 mm Hg and 4.2 g%.

Acid-Base Equilibrium↗
PubMed1977

Acute hypoproteinemic fluid overload: its determinants, distribution, and treatment with concentrated albumin and diuretics.

We simulated the use of massive volumes of crystalloid fluids as a treatment of acute plasma loss in a standardized experimental model and studied the factors determining the retention or excretion of the resulting acute hypoproteinemic fluid overload, its distribution within the body, and its treatment with concentrated albumin and diuretics. In accordance with the classic Starling concept, the serum protein level, i.e. the serum colloid osmotic pressure, determined the excretion/retention ratio of a given water and sodium load. Of the total fluid retention, fat and muscle each accommodated 25%, whereas the skin, which contributes only 7% to the total body weight, accounted for 37% and increased its volume by roughly one third. Concentrated albumin promoted fluid excretion in direct proportion to the achieved increment of the serum protein level and abolished the edema of fat, muscle and skin. Furosemide was virtually ineffective. The implications of these results for the 'adult respiratory distress syndrome' and disturbed wound healing are discussed and related to the concept of a critical threshold of the serum protein level.

Animals↗
PubMedDate not supplied

Adolescent anger: a developmental study.

This research examined adolescent anger in a cohort of adolescents measured twice, once during the freshman year and again in the senior year of high school. Anger was measured by the Anger Index, a questionnaire developed by Siegel (1984). The purpose of the research was to determine if adolescent anger changed over time and if there were gender differences. Results of the study indicated that anger scores appeared to be stable over time for both boys and girls. There were gender and time differences on individual responses for several items, indicating that certain dimensions of anger may differ over time and by gender. It also appeared possible that the interpretation of certain questions on the anger index was different for the adolescents at the two time intervals.

Adolescent↗
PubMedDate not supplied

Epigastric sensations as an unusual manifestation of adult absence epilepsy.

We report the case of a 39-year-old woman with onset of daily epigastric sensations associated with brief episodes of unresponsive blank stare, which have been interpreted as complex partial seizures with occasional secondary generalisation. Phenytoin as monotherapy and in combination with valproate had not been effective. During video-EEG we recorded typical absences with brief 3 second spike, and slow-wave discharges of up to 5 seconds, which were recognized by the patient herself. All absences were preceded by epigastric sensations. There was no indication of focal epilepsy. Monotherapy with valproate substantially decreased the frequency of the absences. In conclusion, this case is peculiar for several reasons: 1) late onset of absence epilepsy, 2) epigastric sensation at onset of absence seizures, 3) recognition of brief "phantom" absences and 4) presumable adverse effects of phenytoin.

Adult↗