The invention relates to a method and an arrangement for detecting movement artifact from bioelectrical signals measured from the head of a patient (1) comprising providing a base element (2) of flexible material, the base element comprising at least three electrodes (3) and a connector (4) connecting the at least three electrodes to a patient monitor (5), placing the base element on the patients head so that the electrodes are in contact with the skin of the patients head, and carrying out measuring of the bioelectrical signals. The method and the arrangement also comprise detecting tension of the base element (2) during the measuring of the bioelectrical signals by means of a tension sensing element (6).
