Spinal Cord and Nerve Injuries in the Cervical Spine

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Chapter Synopsis	Nerve injuries and spinal cord injuries following cervical spine surgery can be devastating to the patient, family, and surgeon, but with adequate counseling preoperatively and appropriate management postoperatively, the impact can be lessened. Surgical technique can help to minimize these complications, but even the best surgical techniques do not entirely prevent serious complications. Promptly recognizing a neurologic complication and managing it accordingly are vital to ensuring the best possible outcome. The purpose of this chapter is to provide an overview of the possible spinal cord and individual nerve injuries, methods to avoid them, and management should they occur.
Important Points	Spinal cord injury occurs in less than 1% of anterior and posterior cervical spine surgical procedures. Spinal cord and nerve injuries can occur during any phase of the perioperative period. Spinal cord monitoring, careful intubation, monitoring of perioperative blood pressure, and a high clinical index of suspicion are vital. Specific nerve injuries are associated with anterior or posterior approaches and procedures. A high index of suspicion remains important for diagnosis, management, and outcome of these injuries.
Clinical and Surgical Pearls	If possible, mean arterial pressures should be maintained at more than 85 mm Hg in patients with “at risk” spinal cords. If signaling changes occur during intraoperative monitoring, then the last procedure performed should be reversed if possible. Identification and protection of the superior thyroid artery may help reduce the risk of superior laryngeal nerve injury during anterior cervical approaches. Although anatomically the course of the recurrent laryngeal nerve is more predictable on the left, clinically the incidence of injury to the recurrent laryngeal nerve has not been lower with left-sided approaches. Protection of the C2 nerve root during posterior C1 and C2 procedures may help reduce the risk of occipital neuralgia.
Clinical and Surgical Pitfalls	Excessive cervical extension during intubation, even in the patient without spinal fractures and mechanical instability, can result in neurologic injury in patients with severe stenosis. Peripheral nerve injuries can result from intraoperative positioning and taping of the shoulders. Patients with C5 nerve root palsies should be enrolled in physical therapy programs to maintain range of motion. Because of the location of most cervical osteotomies at C7 to T1, the C8 nerve root is vulnerable to injury.

Neurologic complications during cervical spine surgery remain a source of concern for patients when they are making a decision about a surgical procedure. Patients depend on surgeons to be both honest and informative about all the potential risks involved in surgery. One of the most common questions from patients when they are considering a surgical procedure is “Can I be paralyzed?” This question is often very difficult to answer because the actual incidence varies depending on the procedure and underlying disease; however, the simple answer is always yes. A risk of permanent neurologic injury always exists during surgical procedures, and patients absolutely need to be aware of this risk preoperatively. The purpose of this chapter is to provide an overview of the possible spinal cord injuries (SCIs) and individual nerve injuries, methods to avoid them, and management should they occur.

Spinal Cord Injuries

Iatrogenic SCIs are fortunately relatively rare occurrences in anterior and posterior cervical spine surgery, with a reported incidence less than 1%. An injury may occur during any phase of the perioperative period including intubation, head positioning, decompression, instrumentation, fracture reduction, and deformity correction, or it can be associated with hypotensive episodes resulting in decreased spinal cord perfusion. Additionally, postoperative SCIs can be directly associated with the surgical procedure (e.g., hematoma or seroma).

Besides the routine surgical precautions used to avoid direct trauma and damage to the spinal cord during decompression and instrumentation, several additional strategies can be employed to decrease the incidence of iatrogenic SCI. These include spinal cord monitoring, careful intubation, close monitoring of perioperative blood pressures, and maintaining a high clinical index of suspicion. Although the use of high-dose steroids remains controversial, it is briefly discussed here as well because it is an option, but it is no longer the standard of treatment for SCIs.

Although controversial, spinal cord monitoring during the surgical management of cervical radiculopathy is not routinely necessary. However, it is used more commonly during anterior or posterior procedures for myelopathy. The techniques employed for monitoring vary widely, and because this is the topic of a separate chapter (see Chapter 11 ), it is discussed only briefly here. Based on the anatomy of the spinal cord, direct trauma to the anterior spinal cord may be best monitored using motor-evoked potentials (MEPs) in procedures performed anteriorly or with evidence of ossification of the posterior longitudinal ligament. Conversely, direct trauma posteriorly may lead to a change in the dorsal sensory tracts and somatosensory-evoked potentials (SSEPs). The authors’ facility routinely uses MEPs and SSEPs for all cervical decompressions.

Because of reports of SCI occurring during intubation and neck extension, debate has centered on when to begin intraoperative spinal cord monitoring. The authors’ institution routinely obtains preintubation baseline monitoring. This monitoring should be individualized to the patient’s disorder and the experience of the surgical and anesthetic teams. In these cases, the surgical monitoring team must work closely with the anesthetic team to plan preintubation monitoring. Once preintubation baseline monitoring is obtained, subsequent monitoring after intubation, before positioning, and after positioning can be compared with these baseline values.

In addition to close coordination with the neuromonitoring team, the role of the anesthesia department is particularly crucial during intubation and for perioperative blood pressure control. In patients with any possibility of mechanical instability, with severe stenosis, or with an inability to tolerate neck extension, fiberoptic intubation, rather than direct laryngoscopy, should be considered. Ultimately, this decision should be made in conjunction with the anesthesiologist, but anesthesiologists rely on surgeons to inform them of patients who are at increased risk for neurologic compromise with neck extension. A review of all cases reported to the American Society of Anesthesiologists Closed Claims database found that SCIs caused by intubation were more likely to be associated with stenosis and spondylosis than they were with instability. Furthermore, this study also showed that 16% of the SCIs were associated with hypotensive episodes. In patients with an “at risk” spinal cord, the authors prefer to keep patients’ mean arterial pressure (MAP) higher than 85 mm Hg throughout the procedure and especially during the decompression.

Although every effort should be made to avoid injury to the spinal cord, management after SCI is recognized should be prompt and aggressive ( Fig. 51-1 ). Intraoperatively, SCIs are usually detected by monitoring, and when these injuries occur every member of the surgical team should determine the best course of action. As a rule, the last step in the procedure should be reversed if possible. For example, if the alert occurs during anterior graft placement, then the graft should be removed. Continued communication with the anesthesia team is also paramount to ensure that MAP is being maintained.

Although the data are controversial, the use of steroids could be considered an option. The authors’ institution generally administers steroids in accordance with the National Acute Spinal Cord Injury Study (NASCIS) II protocol. Additionally, every patient is managed postoperatively in a monitored setting, and MAP requirements are continued for 3 to 5 days. If evidence of spinal cord compression evolves postoperatively, epidural hematoma should be assumed, emergency magnetic resonance imaging (MRI) should be obtained, and emergency surgical intervention should be pursued if indicated ( Fig. 51-2 ).