Anatomic research on the phrenic nerve reconstruction by the spinal accessory nerve

English Keywords:Spinal cord injury  Phrenic nerve  Accessory nerve  Anatomy  Reconstruction

English Abstract:

  【Abstract】 Objectives: To provide anatomic evidence on the reconstruction of respiratory function by transpositioning of accessory nerve into phrenic nerve in the patients with cervical spinal cord injury. Methods: 30 cadavers(60 accessory and 60 phrenic nerves) were dissected in the study. The width and thickness of the end of accessory nerve(AN) and the beginning of phrenic nerve(PN) were measured. The distance from the point of the AN leaving the sternocleidomastoid to the origin and the end of the PN, the length of AN between the lateral border of sternocleidomastoid and the medial edge of trapezius were also measured. The point of the AN leaving from the lateral border of sternocleidomastoid, the positional relationship between the origin of the AN and the thyroid cartilage, the positional relationship between the clavicular line and the point of AN entering the medial edge of trapezius were evaluated. Then the end of the AN and the origin of the PN from 5 cadavers(10 sides) were made as specimens and the number of motor nerve fibers was calculated by using the technique of immunohistochemistry. Results: After AN gave out branches into the sternocleidomastoid, 5 sides descended through sternocleidomastoid, 55 sides continued to descend along the deep surface of sternocleidomastoid, then emerged from the posterior border of sternocleidomastoid, where were 85.2±5.9mm away from the clavicular terminal of sternocleidomastoid. AN crossed posterior triangle to the anterior border of trapezius and entered into trapezius at about 13.2±1.9mm medial to midclavicular line. The width and the thickness of the end of AN was 1.61±0.39mm and 0.61±0.23mm respectively. The length of the accessory nerve between the lateral border of sternocleidomastoid and the medial edge of trapezius was 59.2±12.2mm. The level of the origin of the PN could be at the level of the thyroid cartilage(16 sides), above the thyroid cartilage(32 sides) or below the thyroid cartilage(6 sides). The width and thickness of the origin of the PN was 1.43±0.27mm and 0.60±0.26mm respectively. The length between the point of the AN leaving from the lateral border of sternocleidomastoid and the origin and the end of PN was 26.9±6.0mm and 76.7±8.2mm respectively. The distance of the AN between the lateral border of sternocleidomastoid and the medial edge of trapezius was longer than the length between the point of the AN leaving from the lateral border of sternocleidomastoid and the origin of PN(P=0.000). The number of the motor nerve fibers at the origin of PN, the end of the trunk AN was 836±311 and 1290±371. The difference was statistically significant(P=0.019). Conclusions: The length of AN between the lateral border of sternocleidomastoid and the medial edge of trapezius is significantly longer than the length between the point of the AN leaving from the lateral border of sternocleidomastoid and the origin of PN. Anatomically， it is proved that the AN and the origin of PN can be sutured directly and freely without the injury to the sternocleidomastoid.