A lead for deep brain electrical stimulation, to be inserted into liquid cavities, such as ventricles, or cysternae or subarachnoidal spaces, the lead comprising: a tubular body of biocompatible material having a side wall defining a lumen, said tubular body being suitable for being inserted over at least a fraction of its length into the inside of a patient's body in order to reach a region for stimulation; electrodes disposed close to a distal end of the tubular body; and a rigid stylet for inserting removably into the lumen of said tubular body; the lead being wherein said tubular body has an equilibrium shape that is not rectilinear, being different from the shape of the stylet and presenting one and only one bend, and that is sufficiently flexible and elastic to follow the shape of said stylet by deforming reversibly when the stylet is inserted into the lumen. A deep electrical neurostimulation system comprising an electrical pulse generator and at least one such lead having its electrodes electrically connected to said generator.