Inclusion Criteria:

1. Diseases: Diagnosis of a neuroectodermal tumor of the central or peripheral nervous system or a brain metastasis.
2. Disease confirmation: Patients must have a diagnosis of a malignant tumor proven by the diagnostic method considered standard of care for the specific tumor.
3. Disease progression and treatment failure: Patient must have failed standard front-line treatment and must not be eligible for any higher-priority therapy.
4. Negative pregnancy test for female patients between menarche and menopause is required.
5. Patients must sign an informed consent indicating that they are aware of the investigational nature of this study in keeping with the policies of the hospital.
6. Approval for the use of this treatment regimen by the individual's Human Rights Committee or Institutional Review Board (IRB) must be obtained in accordance with the individual institutional policies and the local, state, and national rules, regulations and laws, is mandatory for an enrolling institution. The documentation of this approval must be on file at the MDAnderson Cancer Center Pediatric Oncology Trials Office prior to enrollment of any patient on study.

Exclusion Criteria:

1. Neurofibromatosis type I
2. Known or suspected inborn errors of metabolism.
3. Patients who require any of the following medications are excluded from enrollment: Carbamazepine, Oxcarbazepine, Primidone, Phenobarbital, Topiramate, Carbapenem antibiotics (ertapenem, imipenem, meropenem), Felbamate, Isoniazid, Lamotrigine, Macrolide antibiotics (clarithromycin, erythromycin, troleandomycin, azithromycin), Zidovudine, Risperidone, Salicylates.
4. Patients who take antiviral medications usually targeted to treat HIV infections or have clinical signs for acquired immunodeficiency syndrome (AIDS) are excluded. HIV testing is not mandatory.
5. Patients who had previous chemotherapy less than three weeks (21 days) ago cannot be enrolled: Patients must have been off all previous chemotherapy or radiotherapy for the 3 weeks prior to initiation of study treatment and recovered from toxic effects of that therapy.
6. Patients which are on a stable dose for valproic acid prior to enrolment are not eligible
7. Patients which have been treated with valproic acid or other histone deacetylase inhibitors such as SAHAa or MS275 and the treatment has failed to control the tumor are not eligible
8. Patient which have been treated with oral continuous etoposide previously and the treatment has failed to control the tumor are not eligible
9. White blood cell count below 2,000/µL excludes patient from enrollment
10. Absolute neutrophil count below 700/uL excludes patient from enrolment
11. Platelet count below 80,000 excludes patient from enrolment
12. Pancreatitis with amylase above two times the upper normal limit excludes patient from enrolment, (even in the absence of clinical signs of pancreatitis)
13. Somnolence at daytime for more than 6 hours excludes patient from enrollment
14. Bilirubin total > 1.5 mg/dL excludes patient from enrollment
15. ALT > 2.5 times upper normal value excludes patient from enrolment
16. AST >2.5 x upper normal value excludes patients from enrolment
17. Frequent vomiting or medical condition that could interfere with oral medication intake (e.g., partial bowel obstruction) excludes patient from enrollment
18. Pregnant or nursing women cannot be enrolled.
19. Women of childbearing potential who are not using an effective method of contraception cannot be enrolled.