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In a prospective study, 22 children with recently manifested infantile spasms (18 patients with symptomatic and 4 with idiopathic infantile spasms) were treated with sodium valproate (VPA). Before VPA was instituted, a loading test was performed to exclude abnormal patterns of VPA metabolites by gas chromatography and mass spectroscopy of serum and urine. This test was repeated during VPA therapy; an abnormal pattern of VPA metabolites was not observed. VPA was started in increasing dosage until infantile spasms were controlled or a maximum dose of 100 mg/kg/day was reached. If VPA did not control seizures or at least reduce frequency significantly after a trial of 4-6 weeks, dexamathasone was added to VPA. If focal seizures occurred in association with localized epileptogenic EEG discharges, carbamazepine (CBZ) was added to VPA. After 4 weeks of VPA monotherapy, infantile spasms were controlled in 11 children. After 3 months of therapy, 16 children were free of seizures (14 patients VPA monotherapy), and 4 children had reduction of seizure frequency to less than 25%. VPA doses varied between 40 and 100 mg/kg/day (mean 74). The mean plasma concentration was 113 micrograms/ml (range 46-177). After 6 months of therapy, total seizure control was achieved in 20 of 22 patients (16 children VPA monotherapy). The mean observation time was 16 1/2 months (range 6-36 months). There were seven relapses in six children during the first 7 months of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

A microscopic model for describing ferroelectric nanoparticles is proposed which allows us to calculate the polarization as a function of an external electric field, the temperature, the defect concentration and the particle size. The interaction of the constituents of the material, arranged in layers, depends on both the coupling strength at the surface and that of defect shells in addition to the bulk values. The analysis is based on an Ising model in a transverse field, modified in such a manner to study the influence of size and doping effects on the hysteresis loop of the nanoparticles.Using a Green's function technique in real space we find the coercive field, the remanent polarization and the critical temperature which differ significantly from the bulk behavior. Depending on the varying coupling strength due to the kind of doping ions and the surface configuration, the coercive field and the remanent polarization can either increase or decrease in comparison to the bulk behavior. The theoretical results are compared with a variety of different experimental data. 5, 6 ). In particular, we analyze the behavior of spherical FE particles, which are depicted in Fig. 1. In case of BTO the bulk interaction parameter is J b = 150 K and the transverse field is Ω b = 10 K. Due to the different numbers of next nearest neighbors on the surface the interaction strength J can take different values for the surface, denoted by J s , and for the bulk, labeled as J b , compare also [21]. Firstly, let us consider the hysteresis loop for different surface configurations represented by the interaction constant J s at a fixed temperature T = 300 K and fixed N. The results for a particle with N = 8 shells are shown in Fig. 2.One observes that the coercive field E c is sensitive to variations of the interaction parameter J. If the coupling at the surface is smaller J s = 50K as that in the bulk J b = 150 K (dashed line), the coercive field E c and the remanent polarization σ r are reduced in comparison to the case for J s = J b (solid line). With other words, the coercive field is lowered when the critical temperature of the system is decreased due to the smaller J s value. In the opposite case J s > J b (dotted line) both, the coercive field E c and the remanent polarization σ r increase compared to J s = J b . Because of the enlarged value of J s the phase transition temperature

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