Hippocampus DBS in Treatment-resistant Schizophrenia

Inclusion Criteria: * Male or female aged between 18 and 55 years. * Having a diagnosis of schizophrenia according to DSM-IV criteria * Having a chronic, recurrent course of disease with a five-year minimum duration * Determined to be treatment-resistant as demonstrated by: 1. Persistence of positive symptoms which have not responded to appropriate treatments for at least 2 years. 2. Inadequate response from adequate trials of two different classes of antipsychotic drugs (not including clozapine), at least 8 weeks. 3. Inadequate response from adequate trial of clozapine, at least 3 months, or unable to tolerate clozapine because of intolerable side effects. 4. Presence of persistent positive symptom defined as i) requiring a score of 4 (moderate) or more on at least 2 of the next PANSS items: delusions, conceptual disorganization, hallucinatory behavior, suspiciousness and unusual thought content; or as ii) requiring a score of 6 (severe) or more on at least 1 of the above PANSS items. * Maintaining stable pharmacological treatment for two months preceding screening visit. * Informed consent Exclusion Criteria: * Neurological disease * Severe physical illness * Contraindications to neurosurgery, MRI or PET-CT; * Substance abuse or dependence * Mental retardation * Female patients who are pregnant or breastfeeding * Severe suicide risk and tendencies