Motor organization of the spinal accessory nerve in the monkey.

The segmental and topographical organization of motoneurons of the spinal accessory nerve was studied in monkeys with horseradish peroxidase (HRP). The sternomastoid muscle is innervated primarily from the C1-C2 level of the cord and the motor column is medial in the ventral horn. The trapezius muscle, however, is innervated primarily from the C2-C3-C4 levels of the cord and the motor column lies in the ventrolateral region of the ventral horn. The data are discussed with regard to treatment of torticollis.