Summary:Purpose: Measurement of cerebral blood flow is routinely used to locate the areas involved in generation and spread of seizures in epilepsy patients. Because the nature of the hyperperfused regions varies with the timing of injection of tracer, in this study, we used a rat model of maximal electroshock seizures to follow up the time-dependent changes in the distribution of seizure-induced cerebral blood flow (CBF) changes.Methods: CBF was measured by the quantitative autoradiographic [ 14 C]iodoantipyrine technique over a 30-s duration. The tracer was injected either at 15 s before seizure induction, simultaneous with the application of the electroshock (tonic phase), at the onset of the clonic phase, or at 3 and 6 min after the seizure (postictal phase).Results: Rates of CBF underwent dynamic changes during the different phases of seizure activity and largely increased over control levels (Յ400%) in the 45 regions studied during all phases of the seizure (first 3 times). CBF remained higher than control levels in 35 and 15 areas at 3 and 6 min after the seizure, respectively.Conclusions: The distribution of maximal CBF increases showed a good correlation with their known involvement in the circuits underlying the clinical expression of the different types of seizure activity, tonic versus clonic. Key Words: Cerebral blood flow-[ 14 C]iodoantipyrine-Seizures-Electroshock.A number of patients with symptomatic or cryptogenic epilepsies are medically intractable and need the surgical resection of the epileptic focus (1-3). The success of surgery depends substantially on the validity of the data used for the location of the seizure focus (4,5). The methods available to localize the epileptic focus include seizure characterization; neurologic examination; neuropsychological testing; magnetic resonance imaging; functional brain imaging of blood flow with singlephoton emission computed tomography (SPECT) and of glucose utilization with positron emission tomography (PET); video/scalp electroencephalographic (EEG) recording; and video electrocorticography (ECoG) with depth, subdural, or epidural electrodes (6,7).Most epilepsy centers tend to perform less-invasive monitoring (8) and use quite routinely local cerebral blood flow (LCBF) measurement by SPECT with hexamethylpropylene amine oxime (HMPAO) or ethyl cysteinate dimer (ECD) labeled with 99m-technetium. Ictal SPECT shows increased LCBF in the epileptic focus in ∼95% of patients with temporal lobe epilepsy (4,5,9,10).However, there has been considerable discussion regarding the optimal timing of early postictal LCBF analysis (5,11,12) since the nature of the territories hyperperfused during the seizure varies with the timing of injection of the tracer. Thus the recognition of the dynamic process of ictal brain perfusion alteration is essential for the application of ictal/postictal SPECT LCBF measurement to localize the epileptic focus and the secondary spread of seizures.Therefore we used an animal model of seizures induced by maximal electroshock to observe...

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A structure preservation of biological and organic samples, close to native state, can only be reached by cryo immobilization techniques. Cryo immobilization allows not only to preserve the high structural integrity but also to arrest dynamic processes in the μs- ms range.After freezing the sample and preparing the surface of interest, it is important to prevent the sample from ice crystal damage, removal of structural water, condensation of water or other contaminants until imaging. Therefore, ideally the samples are kept below the recrystallisation temperature of water (< 147K) during the transfer from the preparation environment into the imaging chamber.For the transfer of frozen samples several concepts have been followed in the,past: a) the specimen after manipulation/preparation were submersed in liquid nitrogen and transferred to the cold stage of the microscope or b) a preparation chamber was permanently attached to the microscope column allowing the direct transfers between the preparation chamber and the cold stage in the microscope. These concepts allow either a high grade of flexibility combined with a high risk of contamination or to prevent contamination but combined with inflexibility. In addition the later also does not allow using the microscope during the specimen preparation procedure, nor transferring the specimen to an other imaging device.