Until recently, the influence of cranial defects upon the underlying intracranial structures has not been sufficiently appreciated. The cranial defect was looked upon as a more or less cosmetic problem. Some authors today still adher to the opinion that a cranial bone plastic is performed purely for cosmetic purposes [79, 142, 169]; if, however, other aspects are also relevant, requires a definite answer. Also, a matter of diseussion is, which material is the most compatible with the surrounding tissue and last but not least the most practicable. Some authors prefer acrylates [71, 100, 102, 114, 141, 149, 169]. Others [102, 169] still cover cranial defects with metal plates, while a third group uses mainly bony material .