Transoral Surgery for Craniovertebral Junction Abnormalities

Anterior approach to the craniovertebral junction (CVJ) was initially explored in Germany in 1935, but pathology at this location has been known for centuries. ¹^, ² Numerous conditions warrant at least the consideration of an anterior approach, but the overall need remains small. ³ As such, extensive experience with this procedure remains uncommon. Congenital and acquired basilar invagination and impression, tumors, and autoimmune disease can be found at this location. ⁴^, ⁵^, ⁶ The most common reason to consider an anterior approach to the CVJ is irreducible ventral compression of the cervicomedullary junction. ⁵^, ⁷ The transoral–transpalatophyrengeal approach is a well-established approach to the anterior CVJ. ⁵^, ⁷^, ⁸ The limits of this approach are the bottom third of the clivus, the anterior C1 arch, and the dens and body of C2. ⁹^, ¹⁰ Traditionally, this approach has a relatively low infection rate and is relatively safe if done on the midline. ²^, ⁷ The procedure can be extended to include jaw and tongue-splitting techniques. ¹¹^, ¹² Over the last 20 years, interest in using endoscopy in both endonasal and transoral approaches has increased, but these techniques are beyond the scope of this chapter. ¹³^, ¹⁴^, ¹⁵^, ¹⁶

1.2 Patient Selection

1.2.1 Imaging

Magnetic resonance imaging (MRI) is the standard imaging modality used to evaluate the amount of stenosis, determine the extent of resection required to achieve surgical goals, and identify flow voids from blood vessels. ¹⁷ Dynamic MRI studies can assist in identifying mechanical vascular occlusions but typically are not performed at our facility. Frequently, congenital deformities have deranged anatomy that is not well appreciated on MRI scans. Computed tomography (CT) scans can identify skeletal deformities not well defined on MRI. In particular, 1-mm or fine-cut scans of the CVJ can be obtained. This type of scan can help the surgeon identify bony landmarks useful for orientation during the approach and decompression, as well for planning of the posterior instrumentation. Finally, dynamic X-rays should be obtained to reveal mobility, which the surgeon can use to determine which deformities need preoperative bracing and which conditions can be treated with traction and posterior stabilization alone, and they can help in setting expectations regarding postoperative neck and head posture.

1.3 Preoperative Preparation

The patient must be screened for bulbar dysfunction. Conditions that are not appreciated preoperatively may become profound problems in the operating room or during the postoperative period. If dysphagia is suspected, evaluation by a speech therapist and with a modified barium swallow is indicated. Dysphonia should be qualified, and a preoperative airway evaluation is required to minimize risk during intubation. The approach requires at least 2.5 cm between the upper and lower incisors.

Concerns about multidrug-resistant organisms have become relevant to the preoperative examination. Methicillin-resistant Staphylococcus aureus (MRSA) has become a frequent colonizer in some patient populations. During the preoperative visit, patients undergo nasal swabbing for culture. A 5-day course of twice-daily mupirocin nasal 2% has been shown to be effective for MRSA decolonization. ¹⁸^, ¹⁹ Several regimens for chlorohexidine, iodine, and other antimicrobial soaps can be used in bathing at home before admission for surgery ¹⁸^, ¹⁹; these techniques may be more relevant to the posterior stabilization.

Admission on the day of surgery is routine, and a postoperative intensive care unit (ICU) bed must be available. If the deformity is considered reducible, on the day before surgery, the patient can be admitted to the ICU, where cervical traction can be applied. Traction should be neutral, and the patient should be closely monitored to avoid overdistraction. Starting weight should be 5 pounds and may be increased at the surgeon’s discretion based on lateral X-rays. It may take 24 to 48 hours to determine whether adequate reduction is possible.

1.4 Operative Procedure

Some simple considerations before the procedure begins include the following: Intubation should be no more complicated than necessary and should maximize exposure or at least minimize obstruction. Positioning should not impede the view of the posterior oropharynx. Patient positioning needs to include enough room for a surgeon, an assistant, a microscope, and fluoroscope at a minimum. Perioperative antibiotics are increasingly standardized, but working within the oral and nasal cavities occasionally requires special consideration.

In our experience, patients can be intubated with standard procedures, but there are some exceptions. Where there is a tenuous neurologic examination, concern for instability, or airway concerns, glide scope fiberoptic intubation or endoscopic awake intubation techniques are available. Oropharyngeal intubation is preferred over nasopharyngeal intubation because it preserves soft palette mobility and avoids obstruction of the operative field. We prefer the use of head pins because it facilitates turning the patient for posterior stabilization. If the surgeon is right-handed, the endotracheal tube is pulled to the left side of the mouth, and the bed is turned away from anesthesia 90 degrees counterclockwise. In this position, there should be room for the microscope and for fluoroscope placed for lateral projections. The patient is papoosed and placed in a slight bit of neck extension. With the patient in head pins, a gentle amount of cervical traction can be imposed, but the shoulders need to be restrained.

Preoperative antibiotics should be chosen based on oral flora. Although cefazolin should cover susceptible species, special considerations should be made for patients with cardiac anomalies, implanted medical devices, and advanced periodontal disease, as well as for individual institutional needs.

In our facility, we use a betadine antiseptic solution to swab the oral cavity and oropharynx. Before draping the patient, a medium-sized red rubber catheter is placed into the oropharynx through the left nares.

The Crockard retractor has been used in our institution and provides adequate exposure for the procedure, but as with all retractors of this type, it places stress on the soft tissues of the mouth. To help minimize the chances of postoperative lingual and pharyngeal edema, the oral and pharyngeal surfaces are covered with 1% hydrocortisone cream before and after the procedure. After the Crockard retractor is retracted, it is used to retract the mandible and tongue. This should be done slowly with consideration for the dentition and to avoid injuring the tongue. The red rubber catheter should be visible and is sutured to the inferior central portion of the uvula with a silk suture. An assistant retrieves the free portion of the catheter from under the drape and gently pulls the uvula into the nasopharynx, retracting the central portion of the soft palate. A small hemostat is adequate weight to maintain slight tension. The two soft palate retractors are placed in the lateral recesses of the soft palate to complete the retraction. Time spent during this portion of the procedure, with the aid of lateral fluoroscopy, can reward the surgeon with a superior exposure ( ▶ Fig. 1.1).

Fig. 1.1 Retractor position for exposure of the oropharynx. (a) View through the mouth with the Crockard retractor in position and a catheter sutured to the uvula. (b) Sagittal view of the oral and nasal cavities showing this position of the red rubber catheter. (c) Sagittal view showing the uvula and soft palate retracted into the nasal cavity. (d) View through the mouth after retraction of the soft palate.

The median raphe of the pharynx is infiltrated with 1% lidocaine with epinephrine, and a midline incision is made into the posterior pharyngeal median raphe. The posterior pharyngeal wall is incised sharply. C2 should be palpable, as well as, depending on anatomy, possibly the anterior arch of C1. The prevertebral fascia and longus colli muscles are separated from the bones with a monopolar cautery. The ventral inferior clivus, the body of the axis, and, if present, the anterior arch of the atlas should be visible. After removing the anterior longitudinal ligament and occipital ligaments, the bony surfaces should be visible and the exposure should be approximately 3 cm wide. Lateral to this lay the vertebral and carotid arteries, the eustachian tubes, and the hypoglossal nerves. Full exposure of the anterior arch of C1, base of the odontoid and medial C1–2 facet joints helps with accurate orientation ( ▶ Fig. 1.2).

Fig. 1.2 Pharyngeal dissection for exposure of the underlying bony structures. (a) Midline incision through the mucosa exposing the underlying musculature. (b) After patient soft tissue dissection, the anterior arch of C1, base of the odontoid, and the medial portion of the C1–2 facet joints are exposed with the self-retaining pharyngeal retractor in place.

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