Describe the course of the vertebral artery in the cervical spine

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The vertebral artery arises from the subclavian artery. It enters the transverse foramen at C6 in 95% of people and courses upward through the foramina above. At C1, the vertebral artery exits from the foramen, courses medially on the superior groove of the posterior ring of the atlas, and enters the foramen magnum to unite with the opposite vertebral artery to form the basilar artery.

Figure 25-2. Vertebral artery. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 23.)

Occipital

Occipital

Vertebral Artery

7. Where is the vertebral artery injured most frequently in upper cervical spine exposures?

The vertebral artery is injured most frequently just lateral to the C1-C2 facet articulation and at the superior lateral aspect of the arch of C1.

8. Why is the patient placed in a reverse Trendelenburg position?

The reverse Trendelenburg position allows venous drainage away from the surgical field and toward the heart, which decreases bleeding during the procedure.

9. Describe the posterior exposure of the lower cervical spine.

The midline posterior exposure is the most common approach used in the cervical spine. Care is taken to carry dissection through the ligamentum nuchae to minimize blood loss. Once the tips of the spinous processes are identified at the appropriate levels through radiographic confirmation, subperiosteal dissection of the posterior elements is then carried out. The posterior approach is extensile and is easily extended proximally to the occiput and distally to the thoracic spinal region.

10. What functional consequences may arise from lateral dissection of the paraspinal muscles?

Lateral dissection carries the potential risk of denervation of the paraspinal musculature. Inadequate approximation of the posterior cervical musculature may lead to a fish gill appearance of the posterior paraspinal muscles and possible loss of the normal cervical lordosis.

11. Why is it important to expose only the levels to be fused, especially in children?

A process termed creeping fusion extension may occur when unwanted spinal levels are exposed during the fusion procedure. This is especially common in children and may lead to unintended fusion at these spinal levels.

12. What complications are associated with the posterior approach to the cervical spine?

Complications include postlaminectomy kyphosis due to muscular denervation or following decompression, radiculopathy, epidural hematoma, and loss of neck range of motion. Postoperative paralysis and paresis, particularly of the C5 nerve root, are also associated with a posterior cervical laminectomy or laminoplasty.

ANTERIOR APPROACHES TO THE CERVICAL SPINE

13. What are the indications for a transoral approach to the upper cervical spine?

Pathology at the craniocervical junction (CCJ) with an anterior midline component (e.g. tumor), which is not amenable to decompression by a posterior approach. A transoral approach allows direct access to CCJ from mid-clivus to the superior aspect of C3.

14. During the transoral approach to the odontoid, what is the key palpable landmark in determining exposure location?

The anterior tubercle of the atlas. The vertebral artery lies a minimum of 2 cm from this anatomic landmark within the foramen transversarium.

15. Describe the transoral exposure to the upper cervical spine.

Transoral retractors are inserted to expose the posterior oropharynx (Fig. 25-3). A soft rubber catheter is placed through the nostril and looped about the uvula to facilitate its cephalad retraction. The area of the incision is infiltrated with 1:200,000 epinephrine. A midline 3-cm vertical incision centered on the anterior tubercle of the atlas is made through the pharyngeal mucosa and muscle. The anterior longitudinal ligament and tubercle of the atlas are exposed subperiosteal^, and the longus colli muscles are mobilized laterally. A high-speed burr may be used to remove the anterior arch of the atlas to expose the odontoid process (Fig. 25-4).

Surgical Approach Vertebral Artery
Figure 25-3. Transoral exposure. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 3.)
Course Vertebal Artery Arch
Figure 25-4. Removal of C1 arch. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 5.)

16. What preoperative patient care factors must be addressed before undergoing a transoral decompression?

All oropharyngeal or dental infections must be treated before elective surgery because wound infection rates are high with this approach. The oral cavity is cleansed with chlorhexidine before surgery, and after surgery perioperative antibiotics are given for 48 to 72 hours (often a cephalosporin and metronidazole).

17. Describe the incision and superficial dissection for the retropharyngeal approach to the upper cervical spine.

A skin incision is made along the anterior aspect of the sternocleidomastoid muscle and is curved toward the mastoid process. The platysma and the superficial layer of the deep cervical fascia are divided in the line of the incision to expose the anterior border of the sternocleidomastoid. The submandibular gland and digastric muscle are identified (Figs. 25-5 and 25-6).

Marginal mandibular nerve

Ansa cervicalis

Retromandibular vein

Exterior jugular vein

Sternocleidomastoid muscle

Longus capitis muscle

Marginal mandibular nerve

Ansa cervicalis

Retromandibular vein

Exterior jugular vein

Sternocleidomastoid muscle

Mylohyoid muscle

Superior laryngeal nerve

Superior laryngeal artery

Mylohyoid muscle

Superior laryngeal nerve

Superior laryngeal artery

Figure 25-5. Anterior retropharyngeal approach. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 10.)

Figure 25-6. Anterior retropharyngeal approach-deep dissection. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 11.)

Hypoglossal nerve

Figure 25-5. Anterior retropharyngeal approach. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 10.)

Hypoglossal nerve

18. What two vessels are ligated once the sternocleidomastoid is retracted?

The superior thyroid artery and the lingual vessels.

19. What nerve may be potentially injured in this approach, resulting in a painful neuroma?

The marginal branch of the facial nerve.

20. What is the importance of the facial artery as an anatomic landmark?

The facial artery helps to identify the location of the hypoglossal nerve, which lies adjacent to the digastric muscle.

21. Stripping of what muscle helps to identify the anterior aspect of the upper cervical spine and basiocciput?

The longus colli.

22. Describe the functional consequence of excessive retraction on the superior laryngeal nerve.

Excessive retraction may lead to hoarseness, inability to sing high notes, and aspiration.

23. Name the palpable anatomic landmarks used to identify the level of exposure of the lower cervical spine.

The angle of the mandible (C2-C3), the hyoid bone (C3), upper aspect of thyroid cartilage (C4-C5), cricoid membrane (C5-C6), carotid tubercle (C6), and the cricoid cartilage (C6).

24. Describe the anterior lateral or Smith-Robinson approach to the lower or subaxial cervical spine.

A transverse incision is made over the interspace of interest in Langer's lines to improve the cosmetic appearance of the surgical scar. The incision is carried slightly laterally beyond the anterior border of the sternocleidomastoid muscle and almost to the midline of the neck. The subcutaneous tissue is divided in line with the skin incision. The platysma may be divided along the line of the incision, or its fibers may be bluntly dissected and its medial-lateral divisions retracted (Fig. 25-7). The anterior border of the sternocleidomastoid is identified, and the fascia anterior to this muscle is incised. The sternocleidomastoid is retracted laterally and the strap muscles are retracted medially to permit incision of the pretracheal fascia medial to the carotid sheath. The sternocleidomastoid and carotid sheath are retracted laterally, and the strap muscles and visceral structures (trachea, larynx, esophagus, thyroid) are retracted medially. The anterior aspect of the spine, including the paired longus colli muscles, are now visualized.

Lonstein Spine
Figure 25-7. Exposure of the lower anterior cervical spine. (From Winter R, Lonstein J, Denis F, et al. Posterior upper cervical procedures: Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 53.)

25. What is the function of the platysma muscle and its corresponding innervation?

The platysma is an embryologic remnant serving no functional importance. It receives its innervation from the seventh cranial nerve.

26. Once the platysma and the superficial cervical fascia are divided, what neurovascular structure is at risk for injury?

The carotid sheath. It contains three neurovascular structures: internal jugular vein, carotid artery, and vagus nerve.

27. What structures are at risk when dissecting through the pretracheal fascia of the neck?

The superior and inferior thyroid arteries may be injured during dissection through the pretracheal fascial layer. Dissection is normally done in a longitudinal manner, using digital dissection.

28. What fascial layer is encountered after dissection through the pretracheal fascia?

After dissection through the pretracheal fascia, the prevertebral fascia or retropharyngeal space is encountered. The prevertebral fascia is split longitudinally, exposing the anterior longitudinal ligament. The longus colli muscle is elevated bilaterally and retracted laterally until the anterior surface of the vertebral body is exposed.

29. What structures are at risk when the dissection is carried too far laterally on the vertebral body in the subaxial spine?

Dissection carried too far laterally may risk injury to the vertebral artery traversing through the foramen transversarium or damage the sympathetic plexus.

30. What are the advantages and disadvantages of approaching the cervical spine anteriorly from the right or left side?

Smith and Robinson advocated using the left-sided approach to decrease the risk of damaging the recurrent laryngeal nerve. On the right side, this nerve loops beneath the right subclavian artery and then travels in a relatively horizontal course in the neck, increasing its chances of damage with exposure in this region. However, most right-handed surgeons find the right-sided approach more facile because the mandible is not an obstruction. A right-sided exposure avoids damage to the thoracic duct. Also, the cervical esophagus is retracted less due to its normal anterior position on the left side of the neck. Overall, either side can be used for the anterior approach because evidence does not suggest one side to be safer than the other.

31. Name the potential causes of dysphagia after anterior cervical surgery.

Dysphagia may be secondary to postoperative edema, hemorrhage, denervation (recurrent laryngeal nerve), or infection. If persistent dysphagia is present, a barium swallow or endoscopy should be considered.

32. Damage to the sympathetic chain may result in what clinical condition?

Horner's syndrome, which is manifested by a lack of sympathetic response resulting in anhydrosis, ptosis, miosis, and enophthalmos. The cervical sympathetic chain lies on the anterior surface of the longus colli muscles posterior to the carotid sheath. Subperiosteal dissection is important to prevent damage to these nerves. Horner's syndrome is usually temporary; permanent sequelae occur in less than 1% of cases.

33. Describe the rare but serious complication of esophageal perforation.

Patients usually manifest symptoms in the postoperative period related to development of an abscess, tracheoesophageal fistula, or mediastinitis. The usual treatment consists of intravenous antibiotics, nasogastric feeding, drainage, debridement, and repair.

Key Points

1. The transoral approach to the craniocervical junction is indicated for fixed deformity causing anterior midline neural compression.

2. The posterior midline approach is extensile and provides access from the occiput to the thoracic region.

3. A key to the anterior approach to the cervical spine is understanding the anatomy of the fascial layers of the neck.

Websites

Approaches to the spinal column: http://medind.nic.in/jae/t02/i1/jaet02i1p76.pdf

Anterior transoral resection: http://www.beverlyhillsspinesurgery.com/webdocuments/siddique-a2.pdf

BiBLiOGRAPHY

1. An H. Surgical exposures and fusion techniques of the spine. In: An H, editor. Principles and Techniques of Spine Surgery. Baltimore: Williams & Wilkins; 1998. p. 31-62.

2. Liu J, Apfelbaum R, Schmidt M. Anterior surgical anatomy and approaches to the cervical spine. In: Kim D, Vaccaro A, Fessler R, editors. Spinal Instrumentation: Surgical Techniques. New York: Thieme; 2005. p. 59-69.

3. McAfee PC, Bohlman HH, Riley LH Jr, et al. The anterior retropharyngeal approach to the upper part of the cervical spine. J Bone Joint Surg 1987;69A:1371 -83.

4. Misra S. Posterior cervical anatomy and surgical approaches. In: Kim D, Vaccaro A, Fessler R, editors. Spinal Instrumentation: Surgical Techniques. New York: Thieme; 2005. p. 267-74.

5. Winter R, Lonstein J, Denis F, et al. Atlas of Spinal Surgery. Philadelphia: Saunders; 1995. p. 1-104.

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