<prompt> Spinal pa of accessory nerve suppliesPlatysmaSternocleidomastoidStylohyoidDiagastric  <response>: Sternocleidomastoid and trapezius are supplied by spinal accessory nerve. Both of them develop from brachial arch mesoderm.It is tested by turning the neck against resistance.B D Chaurasia 7th edition Page no: 65 refer head and neck volume 