The high anterior retropharyngeal approach provides an alternative to the more widely used transoral approach. In straightforward cases involving midline extradural lesions oriented to the level of the arch of C1 or C2, the transoral approach is quite acceptable. If the lesion extends more caudally or laterally, however, or if there are patient-specific limiting factors, such as the opening angle of the jaw or the orientation of the hard palate, the high anterior cervical retropharyngeal approach may be preferred. Although technically more involved, with careful attention to anatomical landmarks and wide, sharp, cadaveric dissection of each subsequent structure, this approach is within the capability of most surgeons familiar with cervical spinal procedures. A C1–3 arthrodesis with anterior screw–plate fixation can be readily performed in a sterile surgical field during the same surgical session, preserving the occipital cervical motion segment.
2.2 Patient Selection
Patients with neoplastic, osseous, or inflammatory lesions caudal to the pharyngeal tubercle that are accessible via an anterior surgical approach are potential candidates.
2.3 Preoperative Preparation
Many patients undergoing anterior craniocervical junction surgery have significant systemic as well as neurologic compromise. Careful communication with the patient, caregivers, and family is essential so that they appreciate the significance and impact of the surgery. Patients need to understand that a long convalescence may be necessary, regardless of the surgical technique used. Efforts are made before surgery to optimize the patient’s nutritional status. At times, a feeding tube is inserted before surgery to provide additional nutritional supplementation. Adequate nutrition improves wound healing and immunologic protection. Patients are screened for concurrent chronic or indolent pulmonary and urinary infections. All patients are counseled that prolonged endotracheal intubation is required and will continue at least 3 to 7 days after surgery. Patients with severe respiratory compromise or advanced myelopathy, in whom early extubation is not realistic, undergo an elective tracheostomy.
2.4 Operative Procedure
2.4.1 Operating Room Setup
Equipment required for this approach includes an intraoperative fluoroscope (C-arm), a contact or scope-mounted laser, and the operating microscope fitted with at least a 350-mm focal length. In some cases, an endoscope can also assist with visualization. One possible room setup is shown in ▶ Fig. 2.1.
Fig. 2.1 Schematic representation of one possible operating room setup. The C-arm can be moved superiorly relative to the patient to provide room for the surgeon to work. When imaging is needed, it can be rolled into the correct position. The C-arm is kept sterile to avoid any delays. KTP, potassium-tianyl-phosphate.
2.4.2 Anesthesia and Patient Positioning
Before intubation, neurophysiologic stimulator/response recorders are placed on the patient to monitor both motor- and somatosensory evoked potentials. Both preintubation and postintubation baselines, as well as postpositioning baselines, are recorded. If the patient is receiving steroids, a stress dose of hydrocortisone is given before anesthesia and repeated every 8 hours. Prophylactic antibiotics are given to provide adequate gram-positive coverage, and redosing is every 4 hours during the surgical procedure. All patients without tracheostomies undergo an awake fiberoptically assisted intubation. After general endotracheal anesthesia is induced, an indwelling lumbar drain catheter is placed. The halo ring is attached to the patient’s head. For patients with a halo attached preoperatively, the halo jacket is removed. The ring is then either placed in traction with weights (10 to 12 pounds) hung over a support device or connected to the operating table by a compatible attachment. The head is extended 15 degrees and rotated 30 degrees contralateral to the side of the surgical approach. This orientation of the head moves the angle of the mandible superiorly out of the surgeon’s line of sight. The patient’s tolerance of this position has been determined while the patient is awake and cooperative during preoperative preparation. The side of the surgical approach is determined based on the lesion configuration or preoperative lower cranial nerve deficit. A unilateral lesion extension is approached contralateral to the side of this extension, whereas an ipsilateral approach is used if a preoperative cranial nerve deficit exists. The contralateral approach provides the surgeon a better line of sight to address the most lateral portions of such a lesion. The ipsilateral approach for cranial nerve deficit helps to avoid the severe disability of a postoperative bilateral lower cranial nerve deficit. If there is a relatively symmetrical or midline lesion, generally a right-sided approach is preferred. If autograft fascia or autograft iliac crest are to be used, the appropriate harvest sites can be prepared and draped ipsilateral to the side of the surgical approach.
2.4.3 Surgical Technique
Superficial Dissection: Skin Incision, Platysma Muscle, and Submandibular Gland
The horizontal cutaneous incision is made 2 cm inferior and parallel to the mandible, beginning 1 cm beyond the midline contralateral to the side of the exposure and extending to the level of the posterior margin of the anterior belly of the sternocleidomastoid muscle, beyond the angle of the mandible. Care must be taken to avoid injuring the submental branch of the facial nerve, which can occur if the incision is too close to the mandible. Such nerve injury results in a drooping of the ipsilateral lower lip. Subcutaneous tissues are freed liberally from the underlying platysma muscle both superiorly and inferiorly, creating two free skin flaps ( ▶ Fig. 2.2). After the platysma muscle has been exposed widely, a vertical incision is created in the midline along the linea alba. This is a midline avascular fascial raphe, which, when opened, will define the medial border of the platysma muscle. This incision is extended superiorly to the level of the mandible and inferiorly to the level of the medial notch of the superior thyroid cartilage. Elevation of the medial border of the ipsilateral platysma muscle then yields access to the fascial covering of the deep surface of the muscle. Once the muscle has been completely dissected, it can be transected horizontally, beginning in the midposition of the vertical incision and extending ipsilaterally the full extent of the skin exposure ( ▶ Fig. 2.3) to create a superior and inferior platysma muscle flap that can be easily retracted away from the field. Elevation of the superior platysma muscle flap reveals the inferior surface of the submandibular gland. Wide, sharp dissection of the fascial investment of the submandibular gland along its inferior boarder will allow the gland to be retracted out of the surgical field ( ▶ Fig. 2.4). The gland is elevated and retained with a self-retaining retractor. Care must be taken to avoid violating the gland parenchyma during fascial dissection or retraction because this could result in wound sialorrhea.
Fig. 2.2 The skin incision and superficial dissection begin as illustrated. Wide dissection of the subcutaneous flaps is performed to free them from the underlying muscle, thus allowing wide exposure. Inset: Overview of patient positioning. It is clear that, when positioning has been properly done, the angle of the mandible moves superiorly and laterally out of the surgeon’s direct line of sight.
Fig. 2.3 Opening the linea alba in the vertical midline. Inset: Horizontal incision of the platysma muscle beginning in the midposition of the vertical opening and extending laterally.
Fig. 2.4 Dissection of the fascial investment of the submandibular gland with subsequent mobilization and rostral elevation of the inferior border of the gland.
Intermediate Dissection: Facial Artery and Vein, Digastric Muscle, Hypoglossal Nerve
Upon elevation of the submandibular gland, the facial artery and vein are seen running posterior and lateral to the deep surface of the gland. The fascia investing the facial artery and vein is then dissected widely throughout the exposure, which mobilizes both structures. When freed, the artery and vein can be retracted out of the surgical field laterally and superiorly. The facial vein can be transected using standard suture-ligature technique or bipolar cautery. The tendon of the digastric muscle is then identified as a horizontally oriented white band set between the red striated muscle of the two bellies of the digastric muscle. These are running medially and laterally with a slight superior orientation caudal to the level of the skin incision and inferior border of the submandibular gland. The fascial sling securing this tendon to the greater wing of the hyoid bone can be transected along the course of the hyoid wing, thereby freeing the tendon ( ▶ Fig. 2.5). Dissection medially and laterally on both the superficial and deep surfaces of both bellies of the digastric muscle is then continued throughout the width of the exposure. Care must be taken when working on the deep surfaces of the muscle because the hypoglossal nerve, which may not be well visualized at this point in the dissection, runs deep to the muscle and can be injured. Upon complete opening of the fascia, the muscle and tendon can be reflected superiorly out from the direct surgical approach. Upon elevation of the two bellies and tendon of the digastric muscle, the hypoglossal nerve is seen running in a horizontal orientation deep and parallel to the digastric tendon ( ▶ Fig. 2.6). Sharp dissection of the fascial investment of the hypoglossal nerve throughout the entire medial to lateral course of the nerve allows elevation of this structure superiorly out of the surgical field. Deep to the hypoglossal nerve are the hyoglossal muscles and superior pharyngeal constrictor muscle. The greater wing of the hyoid bone is seen or is easily palpable at this point.
Fig. 2.5 (a) Dissection of the fascia containing the digastric muscle belly. (b) The digastric muscle is freed, and the tendon is being released. The submandibular gland is seen under the retractor.
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