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Biomedical subjects

M Hajek

Publications and source records attributed to M Hajek.

At least 37 records · Page 2Linked to original sources
PubMed1997

Abnormalities of auditory evoked magnetic fields and structural changes in the left hemisphere of male schizophrenics--a magnetoencephalographic-magnetic resonance imaging study.

Functional and structural changes in 10 DSM-III-R male schizophrenics and 10 healthy volunteers were investigated using magnetoencephalographically (MEG) detected long-latency (N100 m) auditory evoked fields (AEFs) and magnetic resonance imaging (MRI). The AEFs were characterized by single moving equivalent dipoles, which were superimposed on MRIs. There were significant differences in dipole orientations and in AEF latencies in the left hemisphere of schizophrenics, when compared to the controls. The MEG-detected alterations were found to be associated with a bilateral volume reduction of the posterior superior temporal gyrus (pSTG), which was more pronounced in the left hemisphere. Separate analysis of white and gray matter has shown that the pSTG volume reduction resulted from decreased gray matter volumes without white matter changes. Both the functional and the morphological data indicate a left-hemispheric disturbance in our patients.

Adult↗
PubMed1997

31P magnetic resonance spectroscopy in the dorsolateral prefrontal cortex of schizophrenics with a volume selective technique--preliminary findings.

Pettegrew et al (Arch Gen Psychiatry 48:563-568, 1991) were the first to determine abnormalities concerning phospholipids and high energy metabolites in the dorsolateral prefrontal cortex of drug-naive schizophrenics with 31P magnetic resonance spectroscopy (MRS). Other investigations could not replicate these findings. We included in our study 13 schizophrenic inpatients and 14 age-matched controls. Whereas Pettegrew et al found increased levels of phosphodiesters and decreased levels of phosphomonoesters we measured decreased levels of phosphodiesters in the schizophrenics as compared to controls. One possible explanation for the contradictory findings of the both trials might be the different localization techniques used.

Adult↗
PubMed1997

Thalamic glucose metabolism in temporal lobe epilepsy measured with 18F-FDG positron emission tomography (PET).

Thalamic glucose metabolism has been studied in 24 patients suffering from temporal lobe epilepsy (TLE) using interictal 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). A total of 17 patients had a unilateral TL seizure onset, 11 of these patients had a mesial temporal lobe epilepsy syndrome (MTLE), with mesial gliosis and a mesial TL seizure origin. Three patients had a lateral TL seizure origin, and 3 patients had mesial TL tumors. Bilateral TLE was assumed in 7 patients. Only in the patient group with MTLE (n = 11), the ipsilateral thalamic glucose uptake showed a statistically significant lower value when compared to the thalamus of the contralateral side (Wilcoxon paired sign test, P = 0.012). There was a more pronounced hypometabolism in right TLE compared to left TLE. A 'hypersynchronous seizure onset pattern' in ictal EEG was only seen in 6 (26%) patients (1 patient with bilateral, 5 with unilateral TLE). No correlation existed between the thalamic, temporal glucose metabolism and the 'hypersynchronous seizure onset pattern'.

Adult↗
PubMed1997

Increased excitatory amino acid levels in brain cysts of epileptic patients.

We studied two epileptic patients with arachnoid brain cysts by proton magnetic resonance spectroscopy (1H MRS). In addition, histochemical analyses of surgical specimens, cerebrospinal fluid, and cystic fluid were performed in one of the patients. In both patients, greatly increased levels of excitatory amino acids (EAAs) glutamate and aspartate were present in the cystic fluid, while there was only a moderate increase of glutamate in the epileptogenic brain tissue adjacent to the cyst in one of the patients. In non epileptic brain regions, no elevations of the EAAs were present. Since EAAs are involved in induction and maintenance of epileptogenesis, their extremely high concentrations in the cystic fluid may explain seizures in some patients with such brain cysts. Our findings may have therapeutical consequences for patients with drug resistant epilepsy, in whom elevated concentrations of EAAs in the cysts can be verified. Surgery with the aim to create a communication between the cyst and the subarachnoidal space may prevent an accumulation of the EAAs and thus result in a relief of seizures.

Adolescent↗
PubMed1997

Cerebral metabolic changes (18F-FDG PET) during selective anterior temporal lobe amobarbital test.

Cerebral glucose utilisation using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) was measured in 4 patients with temporal lobe epilepsy during a selective anterior temporal lobe (TL) amobarbital test (ATLAT) and compared with their baseline values. 18F-FDG was injected intravenously immediately after administration of amobarbital into the anterior choroidal artery (acha) in the case of the superselective ATLAT and into the territories of acha, posterior communicating artery, and ophthalmic artery in the case of the ATLAT using the temporary balloon occlusion technique. A decrease in glucose uptake as a result of amobarbital application was observed in ipsilateral temporolateral (4 patients), ipsilateral temporomesial (2 patients) and bilateral frontolateral (1 patient) cortices. All patients showed decreased glucose uptake in contralateral temporolateral regions. Cerebellar diaschisis was observed in 2 patients. In conclusion, although aimed at selective inactivation of the mesiobasal TL structures, the ATLAT does not result in exclusive selective glucose hypometabolism of these structures. Relatively widespread ipsilateral and contralateral effects were observed suggesting local and remote metabolic deafferentation. No association was observed between the glucose uptake, clinical or memory performance.

Adolescent↗
PubMed1996

T1 and T2 alterations in the brains of patients with hepatic cirrhosis.

PURPOSE: To determine whether previously reported T1-weighted MR hyperintensities in the brains of patients with hepatic cirrhosis are accompanied by changes in T2. METHODS: We measured T1 and T2 in the brains of 10 patients with chronic liver disease and 7 age-matched healthy volunteers, using classic spin-echo sequences with multiple saturation recovery times and multiple echoes. RESULTS: Both T1 and T2 were shortened in the basal ganglia, cortex, and white matter of the patients, with the greatest shortening in the globus pallidus, where 1/T1 was increased by 0.76 s-1 or 74% and 1/T2 by 1.45 s-1 or 11%. CONCLUSIONS: The T1 changes were accompanied by T2 changes of greater magnitude that were not as visible because T2 is normally much shorter than T1, especially in the globus pallidus.

Adult↗
PubMed1995

Magnetic resonance imaging of brain iron in health and disease.

Brain iron is a major contributor to magnetic resonance imaging (MRI) contrast in normal gray matter, and its role in the pathogenesis of different neurological disorders has also become apparent. Non-heme brain iron is present in the brain mainly in the form of ferritin. The unique magnetic properties of ferritin determine different signal changes on both T1- and T2-weighted images, and the T2 relaxation rates have a linear dependence on applied field strength. This finding is typical for ferric oxyhydroxide cores. The resulting T2-shortening also depends on echo-spacing used in the imaging sequence as well as on the water diffusion coefficient and the size of the ferritin cluster. Quantitation of non-heme brain iron by MRI aids in the diagnosis and monitoring of different neurological diseases.

Brain↗
PubMed1994

Quantification of opiate receptors in two patients with mesiobasal temporal lobe epilepsy, before and after selective amygdalohippocampectomy, using positron emission tomography.

Using PET, reduced glucose metabolism (rCMRglu) and increased binding of the mu opiate receptor ligand 11C-carfentanil have been demonstrated in lateral temporal cortex overlying mesial temporal epileptic foci. Binding of the non-specific opiate receptor ligand 11C-diprenorphine (DPN) to lateral temporal cortex has not shown consistent asymmetries. We measured rCMRglu with 18F-FDG and binding of 11C-diprenorphine in two patients with temporal lobe epilepsy (TLE) before and 5 months after selective amygdalo-hippocampectomy (both patients were seizure-free post-operatively). Pre-operatively, in both patients rCMRglu was decreased in mesial temporal lobe (MTL) (asymmetry index AI = -9.1 and 9.0) ipsilateral to the EEG focus. A more marked reduction was seen in ipsilateral lateral temporal cortex (LTC) (AI = -32.0 and 18.9). DPN binding was reduced in MTL and LTC (AI MTL = -9.3 and 16.2; AI LTC = -8.0 and 5.5) ipsilateral to the focus, but was within 2 SD of the normal range. Post-operatively, the reduction of rCMRglu in LTC was accentuated in one patient and decreased in the other (AI = -23.1 and 45.7) while there was a further reduction of DPN binding in LTC in both patients (AI = -27.8 and 9.8). These preliminary results in only two patients are compatible with downregulation of opiate receptors in LTC after removal of the epileptic focus or post-operative neuronal dysfunction.

Adult↗
PubMed1994

Preoperative and postoperative glucose consumption in mesiobasal and lateral temporal lobe epilepsy.

We have studied 25 patients with interictal 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) before and after selective surgery for temporal lobe epilepsy (TLE). Based on the findings of the presurgical evaluation, including ictal intracranial EEGs, histopathologic findings, and the postoperative outcome, we classified the patients in three subgroups: (1) patients with TLE of lateral temporal origin (n = 5), (2) patients with mesiobasal limbic TLE associated with mesial gliosis (n = 14), and (3) patients with mesiobasal limbic TLE and small mesial tumors (n = 6). Postoperatively, patients with mesiobasal limbic TLE and mesial gliosis and five of six patients with mesiobasal limbic TLE and mesial tumors were seizure-free; the remaining sixth patient had one generalized seizure. Patients with TLE of lateral temporal origin had more than 90% reduction of seizure frequency. The main postoperative metabolic findings were as follows: (1) marked increase of regional cerebral metabolic rate of glucose (rCMRglu), both in the ipsilateral and, significantly, in the contralateral hemisphere in patients with mesiobasal limbic TLE and mesial gliosis-the changes of brain metabolism were characteristic for patients with the syndrome of "mesial temporal lobe epilepsy" (MTLE); (2) decrease of rCMRglu values in the contralateral mesiobasal temporal lobe (TL) cortex in all patient groups--the reduction of rCMRglu in homologous brain structures contralateral to the operated side provides evidence for stronger interhemispheric connections between both mesial TL structures than were hitherto supposed; and (3) a trend toward a normalization of rCMRglu values in the ipsilateral temporal neocortex 12 months after surgery in patients with MTLE syndrome.

Adolescent↗
PubMed1993

Mesiobasal versus lateral temporal lobe epilepsy: metabolic differences in the temporal lobe shown by interictal 18F-FDG positron emission tomography.

Metabolic abnormalities in the temporal lobe (TL) of 25 patients suffering from temporal lobe epilepsy of mesiobasal or lateral TL origin have been investigated using interictal [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET). The epileptogenic area was determined by ictal EEG recordings using foramen ovale and scalp electrodes in 20 patients, and by the use of stereo-electroencephalography in one patient. Four patients with structural lesions on their MRIs had noninvasive ictal surface EEG recordings. Sixteen patients had a clear-cut mesiobasal seizure onset, and in five patients the seizures originated from the lateral temporal neocortex. Twenty-four patients underwent selective surgery. Patients with temporal limbic seizures associated with mesial gliosis (n = 15) had the lowest FDG uptake in the entire TL, followed by patients with lateral temporal seizure origin (n = 5). Patients with tumors located in the mesiobasal TL (n = 5) showed, in general, only a slight decrease of glucose metabolism in all TL structures. There was no clear-cut correlation between the degree of hypometabolism and the location of EEG-defined epileptogenic focus. The metabolic pattern, however, differed between the patient groups and allowed a discrimination between patients of mesial temporal and lateral temporal seizure onset.

Adolescent↗
PubMed1992

[Preoperative localization diagnosis in focal epilepsy using PET].

We present results of studies in which positron emission tomography was applied to the presurgical evaluation of epileptics. Emphasis is placed on results of PET studies with various tracers in partial epilepsies and on the use of PET in age-related epileptic syndromes in children.

Deoxyglucose↗
PubMed1989

Bright white light does not improve narcoleptic symptoms.

Bright white light (500lx) for 4 h/day was applied to seven narcoleptic patients (age 47-65 years, mean 55 years). The effects of the light on the disturbed sleep-wake cycle in narcoleptics were investigated by the measurement of the following parameters: (1) excessive daytime sleepiness and sustained attention (multiple sleep latency test); (2) rest-activity cycles; (3) self-ratings (mood, anxiety, tiredness); (4) urinary cycles of 6-OH melatonin sulphate and cortisol; (5) sleep EEG. Treatment with bright light showed neither objective nor subjective changes in the clinical symptoms of narcolepsy. While similar "dosage" light applications can phase shift human circadian rhythms and improve depression and hypersomnia in winter depression, it is not an appropriate treatment for narcolepsy.

Aged↗
PubMed1989

[Long-term EEG follow-up of 30 patients with large resections in severe extra-temporal epilepsy].

This study presents postoperative scalp EEG-findings of 30 patients operated on for drug resistant epilepsies of extratemporal origin. The primary epileptogenic area was preoperatively defined by means of stereo-electroencephalography (SEEG). The amount and the distribution of postoperatively recorded epileptiform abnormalities were compared to the seizure outcome, to the location and extent of the resection and to the preoperative SEEG results. Furthermore the relations between results of preoperative SEEG-evaluation, the location and size of the therapeutic resection, and the clinical outcome were studied. The clinical outcome does not correspond with the amount of the epileptiform abnormalities in the postoperative scalp-EEGs. In most cases the location of the persisting epileptiform discharges is related to the borders of the resection. The retrospective evaluation of the preoperative SEEG-findings with a view towards their relation to the size of the resection revealed the following result: the better the preoperative definition of the epileptogenic area in terms of location and size, and the more radical the surgical excision of the preoperatively defined primary epileptogenic area, the better the clinical seizure outcome.

Adult↗