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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Arteriolar diameters and venular erythrocyte velocities in the small pial vessels on the surface of the cat brain were measured by TV methods during induced epileptic seizures through a cranial window. Grand mal seizures maximally dilated arterioles and increased venular erythrocyte velocity up to 400%. High positive correlation existed between changes in CSF hydrogen ion concentration and pial arteriolar diameter, suggesting metabolic regulation of CBF through CSF/interstitial fluid hydrogen ion alterations during the seizure.
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PMID:Brain microvascular hemodynamic responses to induced seizures. 0 70

The hemoglobin oxygenation state and the redox state of Cyt.ox. in the rat brain during and after seizure induced by PTZ were measured by using near-infrared spectrophotometry. PTZ administration caused transient reduction of Cyt.ox. in the brain, which might be a trigger for the increase of CBF during seizure. In postictal phase, although BP remained high, Cyt.ox. was in the certain reduced state, which might be due to A-V shunt. Hypoxic loading during seizure caused more reduction of Cyt.ox. than under non-epileptic conditions, which meant that seizure even under mild hypoxic conditions could cause severe hypoxic brain damage.
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PMID:Cerebral oxygenation state in chemically-induced seizures in the rat--study by near infrared spectrophotometry. 133 49

The topography of CO2 vasoreactivity during hyperventilation in 8 patients with complex partial seizure (CPS) was visualized using the regional cerebral blood flow (rCBF) as measured by H(2)15O-PET (positron emission tomography) and compared with that of 10 normal volunteers. In the normal volunteers, the vascular response to CO2 (VrCO2 = delta CBF%/delta PaCO2) in the temporal lobe was 2.46 +/- 0.56 (%/mmHg). In the patients with CPS, VrCO2 in the temporal lobe of the affected side was 2.08 +/- 0.40 (%/mmHg), while VrCO2 on the contralateral side was 2.30 +/- 0.46 (%/mmHg). There was a significant difference in VrCO2 between the affected side of the temporal lobes and the temporal lobes of the normal volunteers. Furthermore, there was a tendency for VrCO2 to be lower in the affected than in the contralateral side of the temporal lobe in patients with CPS. As CO2 is the main regulator of CBF, this impaired vasoreactivity may reflect the brain dysfunction in the seizure focus and adjacent areas.
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PMID:Temporal lobe CO2 vasoreactivity in patients with complex partial seizures. 143 64

The Xe-133 inhalation method was used to study rCBF in 12 patients with partial epilepsy during the interictal phase. SPECT images evidenced a focal CBF defect in 10 out of 12 patients, while quantitative analysis showed CBF abnormalities in all the patients. The focal CBF defect corresponded to the site of EEG abnormalities in nine patients. Additional low-flow areas beyond the EEG focus were found. Five patients presented a significant CBF decrease in the cerebellar hemisphere contralateral to the EEG focus. In five patients with unilateral EEG abnormalities, a CBF reduction was found in the contralateral cerebral hemisphere, mirror to the EEG focus. Finally, a widespread CBF decrease involving one or both cerebral hemispheres was observed in seven patients. Global and rCBF values were not correlated with age, duration of disease, frequency of seizures, secondary generalization, or specific therapy. SPECT may be useful in evaluating EEG epileptic foci, and quantitative SPECT allows the detection of functional effects of the epileptic focus on anatomically connected remote areas, probably due to the decrease of afferent inputs (diaschisis phenomenon).
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PMID:Quantitative assessment of cerebral blood flow in partial epilepsy using Xe-133 inhalation and SPECT. 176 68

Focal cortical CBF and oxygenation were measured in rats during repetitive seizures to determine whether CBF is maintained above a critical level for adequate delivery of O2. Cerebral oxygenation was determined by measuring relative changes in the oxidation/reduction level of cytochrome aa3 and CBF was measured by the washout of H2. During early seizures, cortical CBF increased to 350% of control and cortical oxygenation also rose markedly. During later seizures, both the increases in CBF and in cortical oxygenation were attenuated progressively. This was accompanied also by attenuation of the associated increases in MABP. Cortical oxygenation decreased during a seizure if the increase in CBF failed to exceed 150-200% of control, defining the critical CBF value. Ventilating the rats on 97% O2 resulted in restoration of the seizure-associated increases in cortical oxygenation in 50% of the cases. The elevation of inspired O2 was effective only if CBF increased once again above 150-200% of control, confirming that the critical CBF lies within this range of values. We conclude that CBF must rise greater than 200% of control levels to provide sufficient O2 to meet the enhanced metabolic requirements of repetitive seizures.
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PMID:Relative hypoperfusion in rat cerebral cortex during recurrent seizures. 184 66

Hemimegalencephaly (HME) is a severe unilateral brain malformation the prognosis of which may be improved by hemispherectomy. HME also provides a unique opportunity to compare normal and pathological hemispheric function in the same patient. We performed a serial functional cerebral imaging study in a child suffering from a neuropathologically confirmed left HME. He was hemispherectomized at 11 months because of intractable epilepsy; this led to cessation of seizures and dramatic psychomotor improvement. Regional cerebral blood flow (rCBF) was studied at 1, 7, 10, 12 and 25 months with single photon computed tomography (SPECT) using 133-Xenon and with simultaneous EEG recording. At one month of age SPECT was performed ictally. During left EEG discharges, rCBF was 40% higher on the left hemisphere than on the right, even in occipital and frontal regions, usually immature at this age. A crossed cerebellar hyperperfusion was also found. At 7 and 10 months, SPECT was performed interictally; rCBF was 45% lower in the left hemisphere than in the right. During follow-up, global and regional CBF values showed normal levels and normal maturation in the right hemisphere except for a mild and transient decrease observed one month after hemispherectomy. SPECT provides an additional procedure for studying hemispheric function in vivo. Serial SPECT imaging may be useful for the preoperative and postoperative evaluation in unilateral cerebral malformation.
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PMID:A serial study of regional cerebral blood flow before and after hemispherectomy in a child. 190 10

The effects of single and repeated electroconvulsive shock (ECS) treatment on regional cerebral blood flow (rCBF) and on rates of glucose flow from blood to local brain areas (rCGF), were investigated in pentobarbital-anesthetized rats, using quantitative autoradiographic techniques. Effects of single ECS on rCBF were assessed at two average time points of 15 and 55 sec after the application of the electric current, whereas the effects on rCGF were assessed at 70 and 110 sec. Effects of repeated ECS were assessed 24 hr after the last ECS in a series of eight daily treatments. Single ECS caused marked increases in rCGF in different brain structures, but no significant effects were observed after repeated ECS. Similarly, substantial increases in rCBF were seen during and immediately after the ECS-induced seizure, but not 24 hr after the last treatment of repeated ECS. Single ECS appeared to have differential effects on rCBF in hind-brain structures as compared to more anterior regions. A linear relationship between rCBF and rCGF values was established in control animals, indicating coupling of these two variables with a constant rCBF/rCGF ratio. ECS caused an apparent increase in the CBF/CGF ratio, which might be attributed to the different temporal resolution of the two methods used here to estimate rCGF and rCBF. Analysis of the increments of rCGF and rCBF extrapolated to the same point in time after a single ECS (10 sec), revealed that in many of the examined structures the CBF/CGF ratio was similar to that observed in control animals, indicating that the coupling of CBF and CGF is maintained during the seizure. But in some brain stem structures such as the dorsal raphe, inferior colliculi, superior olivary nucleus, and the vestibular nucleus there were large increases in CGF associated with a marked drop in the CBF/CGF ratio. This observation suggests that high metabolic demands can be met by increased local blood flow up to a given "ceiling" keeping the glucose clearance from blood to brain tissue constant. However, when the metabolic demands exceed this upper limit, the additional demands could be met by an increased clearance of glucose without a change in CBF.
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PMID:Alterations of local cerebral blood flow and glucose uptake by electroconvulsive shock in rats. 191 18

The objective of the present study was to explore metabolic correlates to the appearance of postischemic seizures and the enhancement of brain damage observed in subjects that are made hyperglycemic prior to the induction of ischemia. To that end, transient forebrain ischemia of 10-min duration was induced in normo- and hyperglycemic rats, with subsequent measurements of local CMRglc (LCMRglc) after 3, 6, 12, and 18 h of recirculation. We posed the questions of whether postischemic depression of LCMRglc is exaggerated by preischemic hyperglycemia and whether there are signs of localized increases in LCMRglc in hyperglycemic rats, reflecting subclinical seizure activity. The results confirmed the presence of a long-lasting postischemic depression of LCMRglc in normoglycemic rats. This depression was partially but not tightly related to the degree of reduction of local CBF during ischemia. The depression was most pronounced in neocortical areas and in the hippocampus, but notably it was less pronounced in the densely ischemic caudoputamen. Little or no reduction of LCMRglc was observed in moderately or mildly ischemic structures such as the hypothalamus, red nucleus, and cerebellum. Preischemic hyperglycemia markedly accentuated the postischemic depression of LCMRglc. For example, although the subjects quickly regained wakefulness and motility, they had LCMRglc values in neocortical areas that remained below 50% of control. Corresponding but quantitatively less pronounced reductions in LCMRglc were observed in other areas. Notably, preischemic hyperglycemia reduced postischemic LCMRglc also in areas that showed only moderate to mild reductions in CBF during the ischemia. The results thus demonstrate that preischemic hyperglycemia has pronounced metabolic effects in the postischemic recovery period. The data provide no indication that postischemic seizures, which develop after a recovery period of approximately 24 h, are preceded by the appearance of hypermetabolic "seizure" foci.
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PMID:Preischemic hyperglycemia enhances postischemic depression of cerebral metabolic rate. 273 14

A spectacular spongiotic lesion, symmetrical in distribution and restricted to the pars reticulata of the substantia nigra (SNPR) has recently been described in hyperglycemic rats surviving 1-18 h after a brief period of transient ischemia. The purpose of this study was to clarify the pathogenesis of the lesion. In order to study whether the lesion was due to changes occurring during ischemia, local cerebral blood flow (l-CBF) and energy metabolites were measured in the substantia nigra (SN) and in other brain areas. Furthermore, brains were examined by light and electron microscopy immediately after ischemia and in the early recirculation period. Autoradiographic CBF measurements showed ischemia flow levels in the SN of 30-40% of control, similar in normo- and hyperglycemic rats. Thus, although ischemic, this structure had a considerable amount of residual flow. There was also a corresponding partial preservation of the adenylate energy charge. However, lactate levels were high, and in hyperglycemic subjects they rose to values previously described during status epilepticus (about 25 mumol/g). In hyperglycemic animals, neuronal alterations were consistently present in SNPR by the end of the 10-min period of ischemia. They included clumping of nuclear chromatin and subplasmalemmal clearing of the perikaryon. Some mitochondrial swelling was present in neuronal perikarya and in dendrites. The normal alignment of microtubules in the dendrites was disturbed, but there was no or only slight swelling of the dendrites. Aggregation of synaptic vesicles was a conspicuous finding in axonal terminals, which were also slightly swollen. Otherwise, the axons appeared largely spared. Microvessels looked quite intact. Similar cellular changes were observed in the early recovery period. Dendrites, however, started to swell, and their expansion finally caused the spongiotic appearance of the pars reticulata. The appearance of the dendritic lesions is strongly suggestive of transmitter-mediated ("excitotoxic") damage. However, it seems likely that the marked acidosis is injurious as well. We tentatively conclude that both mechanisms interact to give the final lesion. The results, and those previously obtained in epileptic seizures, suggest that mitochondria of SN neurons and neuronal processes are particularly prone to damage.
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PMID:Pathogenesis of substantia nigra lesions following hyperglycemic ischemia: changes in energy metabolites, cerebral blood flow, and morphology of pars reticulata in a rat model of ischemia. 336 99

Intracarotid injection of 133-Xenon and recording of wash out of radioactivity by 254 external stationary detectors was used to measure rCBF. Initial slope values were calculated by a computer, translated into color code and displayed on a TV-screen. rCBF in patients with epilepsy has been the object of former studies. Those who had a cortical focus showed corresponding high blood flow values during attack and during EEG paroxysms without clinical attacks. On the contrary, all other patients with a cortical focus were normal. Patients with complex partial seizures displayed no abnormalities interictally. During generalized epileptic seizures rCBF and metabolism doubled. Distinction must be made between patients with aura (classic migraine) and patients without aura (common migraine). In the latter CBF was normal or slightly elevated. In the former the aura symptoms are associated with reduced CBF. The reduction usually starts posteriorly and spreads gradually anteriorly. rCBF remains depressed for up to several hours into the headache phase. After 8-12 hours a reactive hyperemia may ensue. In common migraine rCBF remains normal throughout the attack. During classic migraine attacks rCBF is depressed whereas it is increased during epileptic attacks. Thus rCBF studies further strengthen the differences between epilepsy and migraine.
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PMID:Regional cerebral blood flow (rCBF) studies in migraine and epilepsy. 360 67


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