Realistically the vaccines selected for retards so it is a biased sample. But it makes sense that in those cases in which the spike protiens made it through the blood brain barrier that it would cause harm. The linked paper is not a study at all but a review of other papers that have been published. So no new data. And it does not claim that the jab gives everyone brain damage. All it does is review documents about cases in which it did cause brain damage. These could be outliers.