An electrical brain treatment system includes a parenchymal electrode, configured to be implanted in direct physical contact with brain parenchyma or meninges of the brain of a subject identified as at risk of or suffering from a disease； and a cerebrospinal fluid (CSF) electrode, configured to be implanted in a CSF-filled space selected from a ventricular system and a subarachnoid space. Control circuitry is electrically coupled to the parenchymal electrode and the CSF electrode, and is configured to clear a substance from the brain parenchyma into the CSF-filled space of the brain by applying direct current between the parenchymal electrode and the CSF electrode as a series of pulses, with an average amplitude of between 0.25 and 0.5 mA, an average pulse width of between 0.5 and 2 ms, and an average frequency of between 1 and 5 Hz. Other embodiments are also described.
