The invention relates to a surgical apparatus, in particular a navigation probe for localizing and treating lesions in a brain, comprising:a body member (10) having an anterior end (20), a posterior end (30) and at least one groove (60, 62) extending for a particular length in a longitudinal direction of the body member (10) between said anterior end (20) and said posterior end (30);a saddle (70) adapted to securely hold a medical device, the saddle (70) being placed on said body member (10) and having at least one grip (74, 75, 76) that extends into said at least one groove (60, 62) so as to mount the saddle (70) on the body member (10) moveable in said longitudinal direction; anda means for maneuvering said body member (10).