An actuation mechanism for a surgical instrument comprising a handle, a sheath, a tool and a deformable gripper for actuating the tool, said actuation mechanism comprising: - a sleeve, equipped with a longitudinal axis, configured to receive the surgical instrument and comprising one or more guides (226, 264, 280) stationary mounted with respect to the sleeve and extending substantially in a plane perpendicular to said longitudinal axis, a plurality of studs (268, 270) extending along the longitudinal axis being provided on the or each guide, on some guides only, or distributed over the different guides, or a plurality of jaws (208, 210) mounted between the guides (226, 264, 280) stationary mounted with respect to the sleeve, so as to be translate relative to said guides and extending substantially in the plane perpendicular to said longitudinal axis, several studs (250, 252) extending along the longitudinal axis being provided on the or each jaw, on some jaws only, or distributed on the different jaws; - at least two wheels (204, 206), mounted on the sleeve on either side of said part or parts along said longitudinal axis, each wheel (204, 206) being equipped with at least one groove (242, 242a, 242b, 243) and a mechanical transmission element, said at least one groove (242, 242a, 242b, 243) of each wheel (204, 206) receiving, in a movable manner in said groove, one of said plurality of studs (250, 252, 268, 270); - at least two drive shafts (212, 214), a first drive shaft being equipped with a first mechanical transmission element cooperating with the mechanical transmission element of one of the two wheels (204, 206) and a second drive shaft being equipped with another first mechanical transmission element cooperating with the mechanical transmission element of the other of the two wheels (204, 206). - a sleeve, equipped with a longitudinal axis, configured to receive the surgical instrument and comprising one or more guides (226, 264, 280) stationary mounted with respect to the sleeve and extending substantially in a plane perpendicular to said longitudinal axis, a plurality of studs (268, 270) extending along the longitudinal axis being provided on the or each guide, on some guides only, or distributed over the different guides, or a plurality of jaws (208, 210) mounted between the guides (226, 264, 280) stationary mounted with respect to the sleeve, so as to be translate relative to said guides and extending substantially in the plane perpendicular to said longitudinal axis, several studs (250, 252) extending along the longitudinal axis being provided on the or each jaw, on some jaws only, or distributed on the different jaws; - at least two wheels (204, 206), mounted on the sleeve on either side of said part or parts along said longitudinal axis, each wheel (204, 206) being equipped with at least one groove (242, 242a, 242b, 243) and a mechanical transmission element, said at least one groove (242, 242a, 242b, 243) of each wheel (204, 206) receiving, in a movable manner in said groove, one of said plurality of studs (250, 252, 268, 270); - at least two drive shafts (212, 214), a first drive shaft being equipped with a first mechanical transmission element cooperating with the mechanical transmission element of one of the two wheels (204, 206) and a second drive shaft being equipped with another first mechanical transmission element cooperating with the mechanical transmission element of the other of the two wheels (204, 206).