Electrical substance clearance from the brain

A method is provided that includes implanting (a) a parenchymal electrode in or in contact with an outer surface of brain parenchyma of a subject identified as at risk of or suffering from a disease, and (b) a cerebrospinal fluid (CSF) electrode in a CSF-filled space of a brain of the subject, the CSF-filled space selected from the group consisting of: a ventricular system and a subarachnoid space. A midplane treatment electrode is disposed in or over a superior sagittal sinus. Control circuitry is activated to drive the parenchymal electrode and the CSF electrode to drive a substance from the brain parenchyma into the CSF-filled space of the brain, and apply a treatment current between the CSF electrode and the midplane treatment electrode to drive the substance from the CSF-filled space of the brain to the superior sagittal sinus. Other embodiments are also described.