6. Methods against bias The patients will be randomized to one of the treatment arms. To avoid unbalanced group sizes and unequal numbers of adolescents and adults, there are two randomization lists, one for patients < 11 years, one for older patients (stratification). Blinding is not possible because the administration of the two drugs is different and would have necessitated the additional use of placebo capsules in the IVIG group and placebo infusions in the tacrolimus group. Because the production and administration of an adequate "IVIG-placebo" is highly impracticable, no blinded treatment application was planned. The physicians assessing the "Motricity Index" and the "Hemispheric ratio" are unaware of the kind of treatment used.