A headrest system for a motor vehicle seat, said system comprising: • a headrest provided with a framework, said framework comprising parallel first and second metallic rods, the upper portion of said framework being covered with a cushion, at least said first rod being provided with an anti-extraction notch in the form of a trench, said notch having a lower face for blocking said first rod in upward sliding, • first and second sleeves for slidably receiving said first and second rods respectively, said sleeves being intended to be fixedly mounted at the top of the backrest of said seat, at least said first sleeve being provided at its upper end with: ∘ a slider mounted so as to slide radially and having a ratchet track arranged so as to be able to be inserted into said notch when they are disposed opposite one another, ∘ a spring for slidably actuating said slider so as to enable the insertion of said track into said notch, said system being characterised in that: • said first rod is provided with a projection, said projection projecting radially from the general outline of said first rod, • said first sleeve is provided with a groove extending axially so as to fittedly receive said projection in sliding, • the distance between said notch and said projection is defined so that said projection is disposed in said groove when said track is inserted into said notch, so as to block said first rod in axial rotation in the event of an impact of the head of a passenger against said headrest. • a headrest provided with a framework, said framework comprising parallel first and second metallic rods, the upper portion of said framework being covered with a cushion, at least said first rod being provided with an anti-extraction notch in the form of a trench, said notch having a lower face for blocking said first rod in upward sliding, • first and second sleeves for slidably receiving said first and second rods respectively, said sleeves being intended to be fixedly mounted at the top of the backrest of said seat, at least said first sleeve being provided at its upper end with: ∘ a slider mounted so as to slide radially and having a ratchet track arranged so as to be able to be inserted into said notch when they are disposed opposite one another, ∘ a spring for slidably actuating said slider so as to enable the insertion of said track into said notch, said system being characterised in that: • said first rod is provided with a projection, said projection projecting radially from the general outline of said first rod, • said first sleeve is provided with a groove extending axially so as to fittedly receive said projection in sliding, • the distance between said notch and said projection is defined so that said projection is disposed in said groove when said track is inserted into said notch, so as to block said first rod in axial rotation in the event of an impact of the head of a passenger against said headrest. ∘ a slider mounted so as to slide radially and having a ratchet track arranged so as to be able to be inserted into said notch when they are disposed opposite one another, ∘ a spring for slidably actuating said slider so as to enable the insertion of said track into said notch, said system being characterised in that: • said first rod is provided with a projection, said projection projecting radially from the general outline of said first rod, • said first sleeve is provided with a groove extending axially so as to fittedly receive said projection in sliding, • the distance between said notch and said projection is defined so that said projection is disposed in said groove when said track is inserted into said notch, so as to block said first rod in axial rotation in the event of an impact of the head of a passenger against said headrest. • said first rod is provided with a projection, said projection projecting radially from the general outline of said first rod, • said first sleeve is provided with a groove extending axially so as to fittedly receive said projection in sliding, • the distance between said notch and said projection is defined so that said projection is disposed in said groove when said track is inserted into said notch, so as to block said first rod in axial rotation in the event of an impact of the head of a passenger against said headrest.