Vulnerability of the sympathetic trunk during the anterior approach to thelower cervical spine

Study Design. Anatomic dissection and measurements of the cervical sympathe tic trunk relative to the medial border of the longus colli muscle and late ral angulation of the sympathetic trunk relative to the midline on both sid es were performed. Objective. To determine the course and location of the sympathetic trunk qu antitatively and relate this to the vulnerability of the sympathetic trunk during the anterior approach to the lower cervical spine. Summary of Background Data. The sympathetic trunk is sometimes damaged duri ng the anterior approach to lower cervical spine, resulting in Horner's syn drome with its associated ptosis, meiosis, and anhydrosis. No quantitative regional anatomy describing the course and location of the sympathetic trun k and its relation to the longus colli muscle is available in the literatur e, Methods. In this study, 28 adult cadavers were used for dissection and meas urements of the sympathetic trunk. The distance between the sympathetic tru nk and the medial borders of the longus colli muscle at C6 and the angle of the sympathetic trunk with respect to the midline were determined bilatera lly. The distance between the medial borders of the longus colli muscle fro m C3 to C6 and the angle between the medial borders of the longus colli mus cle also were measured. Results. The sympathetic trunk runs in a superior and lateral direction, wi th an average angle of 10.4 +/- 3.8 degrees relative to the midline. The av erage distance between the sympathetic trunk and the medial border of the l ongus colli muscle is 10.6 +/- 2.6 mm. The average diameter of the sympathe tic trunk at C6 is 2.7 +/- 0.6 mm. The length and width of the middle cervi cal ganglion were 9.7 +/- 2.1 mm and 5.2 +/- 1.3 mm, respectively. The dist ance between the medial borders of the longus colli muscle was 7.9 +/- 2.2 mm at C3, 10.1 +/- 3.1 mm at C4, 12.3 +/- 3.1 mm at C5, and 13.8 +/- 2.2 mm at C6, and the angle between the medial borders of the longus colli muscle was 12.5 +/- 4.7 degrees Conclusions. The sympathetic trunk may be more vulnerable to damage during anterior lower cervical spine procedures because it is situated closer to t he medial border of the the longus colli muscle at C6 than at C3. The longu s colli muscles diverge laterally, whereas the sympathetic trunks converge medially at C6. As the transverse foramen or uncovertebral joint is exposed with dissection or transverse severance of the longus colli muscle at the lower cervical levels, the sympathetic trunk should be identified and prote cted.