HEADREST MOUNTING SYSTEM FOR A MOTOR VEHICLE SEAT

System (1) comprising: two rods (2), at least one of said rods comprising at least one locking notch (4) in sliding; at least one sheath for receiving (6) a rod (2) notched in sliding, said sheath comprising a sliding sleeve (7) and, secured to said sleeve, a drawer (8) mounted mobile in radial translation, said drawer being constrained in translation towards said sleeve by an elastic return means (9), said drawer being provided with a notching edge (10), said edge being arranged to be able to engage, under the effect of said return means, in said notch; a means of reception (15) in interlocking of said sheath, said means being intended to be mounted at the top of the backrest of said seat, said notched rod and said sleeve being respectively arranged to couple in axial rotation; said sheath and said reception means being respectively arranged so that said sheath can pivot in axial rotation in said reception means on either side of its reference angular position, so that the notching of said edge in said notch persists in the event of axial rotation of said notched rod.