The present work by Walther arose from urgent clinical needs: The neurosurgical clinic required clear guidelines from the psychiatric clinic regarding the diagnostic utility, prognosis, and treatment of the mental state of their tumor patients. It was evident that the existing psychiatric literature did not provide sufficient and clear answers to this question. Thus, the task emerged to systematically study the psychiatry of brain tumors once again. This clinical purpose of the work necessitated starting from the entirety of tumor cases presented to the neurosurgeon, rather than focusing on those cases that must seek psychiatric treatment due to mental disorders.