42 Endoscopic Transoral Approach The endoscopic transoral approach is a midline approach to the craniocervical junction. It is suitable for surgical exposure of the clivus, as well as the anterior aspect of the magnum foramen, the atlas, and the axis (C1 and C2). Surgical exposure can be further widened laterally through the retrostyloid approach gaining access to the jugular foramen region. The midline approach is indicated for extradural lesions involving the anterior aspect of the craniovertebral junction. The lateral variants are instead indicated to treat lesions involving the jugular foramen, lower cranial nerves. • Extradural neoplasms (chordoma, chondrosarcoma) situated in the anterior midline craniovertebral junction region. • Cord-compressive masses (such as reactive pannus secondary to trauma or rheumatoid diseases) situated anteriorly to the lower cranial nerves, at the craniovertebral junction in the setting of a contraindication to an endonasal approach. • Paragangliomas situated mostly or entirely caudal to the jugular foramen. • Benign peripheral nerve tumors (schwannomas and neurofibromas) of the lower cranial nerves. • Carotid body tumors below the foramen lacerum. • General position: The body is positioned supine with the head on a horseshoe or cranial fixation pins. • Head position: For maximum surgeon comfort, the neck should be neutral or slightly flexed. Assuming a two-surgeon team (typically an otolaryngologist and a neurosurgeon), a three-step process further maximizes ergonomics for the surgeons: Fig. 42.1 Head positioning. (A) The head is translated vertically to prevent the instruments from hitting the chest, especially when the head must be placed in a flexed position. (B) The head is rotated approximately 30° to the right along the coronal plane of the body if both surgeons are right-handed. This may be left neutral if one member of the team is left-handed. (C) The head is tilted approximately 30° along the sagittal axis of the body if both surgeons are right-handed to prevent them from having to reach across the torso to operate. This may be left neutral if one member of the team is left-handed. ◦ 1. The head is elevated slightly from the body (Fig. 42.1A). ◦ 2. It is tilted slightly toward the left relative to the axis of the body for right-handed teams (Fig. 42.1B). ◦ 3. It is further turned slightly toward the right or left for surgical teams that are completely right- or left-handed, respectively or left neutral for teams of mixed handedness (Fig. 42.1C). • Anti-decubitus device: Standard pressure point padding for dependent pressure points in the supine position, including the elbow joints, ulnar nerves if wrapping the patient and foregoing the use of arm boards, the sacral prominence, and the heels might be used. • Unique preparation consideration: The periumbilical and/or anterolateral thigh should be prepared using the surgeon’s choice of antimicrobial agent and draped so that they are available for fat and/or muscle graft if needed for dural defect repair or carotid artery injury. • No skin incision is required to access the posterior oropharyngeal mucosa. • An oral retractor (such as a Dingman or Spetzler Sonntag retractor) is used to keep the mouth open and tongue retracted caudally throughout the case, carefully avoiding injury to the teeth and protecting the endotracheal tube behind the retractor. • The two anatomic regions relevant to the skull base neurosurgeon via this approach are the craniovertebral junction (may require a midline transpalatal approach) and the region of the parapharyngeal internal carotid artery (ICA), foramen lacerum, and jugular foramen (requiring a parapharyngeal retrostyloid approach). • Tongue. • Teeth. • Soft palate. • Uvula. • Palatoglossal arch (anterior pillar). • Once patient is under general anesthesia and the endotracheal tube is secured very laterally in the mouth, a rubber band is passed from the nostrils and it is encountered in the oropharynx. The rubber band is retracted anteriorly bringing the soft palate away from the oropharynx allowing for palate sparing transoral approach. • In cases of high position of C2, the authors prefer a transnasal approach. However, if there is a need for transoral approach, the soft palate can be transected entirely to permit lateral retraction for oropharyngeal exposure. To accomplish this, an incision is made just lateral to the uvula on either side and curved toward midline above the uvular base. This is extended cranially to the junction with the hard palate (Fig. 42.2). Hooks or sutures are then used to maintain lateral retraction of the split soft palate. • The oropharyngeal mucosa is incised at the midline (Fig. 42.3) and reflected laterally, exposing the horizontally-oriented fibers of the superior constrictor muscle, which terminates at approximately the level of the superior aspect of the C1 anterior arch and the C2 body (Fig. 42.4). Greater tongue retraction facilitates exposure of the C3 body caudally.
42.1 Introduction
42.2 Indications
42.2.1 Midline Approach to the Craniovertebral Junction
42.2.2 Parapharyngeal Retrostyloid Approach
42.3 Patient Positioning (Fig. 42.1)
42.4 Oropharyngeal Access and Retraction
42.4.1 Critical Structures
42.5 Midline Approach to the Craniovertebral Junction