Hi, Thanks for writing in. Glioblastoma is a glial tumor and might be found in different forms. It is malignant and a glioblastoma with oligodendroglial component is most likely a malignant tumor for which chemotherapy is being given. It is a kind of cancer cell proliferation in the brain. Please share complete details like tumor size, location and pathological type if biopsy or surgery has been done. In many patients having a well differentiated glioblastoma, chemotheraphy and surgery gives good results. In patients with slightly higher grade, the treatment might also include radiation therapy, chemotherapy and surgery. Patient with lower grade glioblastoma can make a near normal recovery. However those with a higher grade need to be kept under close observation and pain relief. Since the primary tumor is in the brain, starting chemotherapy can shut down certain areas of brain and that is what has happened to your mother. The first intention is to treat the cancer tumor and then the doctors can concentrate on the cognitive areas. She requires to be under close medical observation with repeat MRI scans as required. Please do not worry and pray for her complete recovery.