The endoscopic transoral approach to the craniovertebral junction: an anatomical study with a clinical example.

OBJECTIVE The microscopic transoral, endoscopic transnasal, and endoscopic transoral approaches are used alone and in combination for a variety of craniovertebral junction (CVJ) pathologies. The endoscopic transoral approach provides a more direct exposure that is not restricted by the nasal cavity, pterygoid plates, and palate while sparing the potential morbidities associated with extensive soft-tissue dissection, palatal splitting, or mandibulotomy. Concerns regarding the extent of visualization afforded by the endoscopic transoral approach may be limiting its widespread adoption. METHODS A dissection of 10 cadaver heads was undertaken. CT-based imaging guidance was used to measure the working corridor of the endoscopic transoral approach. Measurements were made relative to the palatal line. The built-in linear measurement tool was used to measure the superior and inferior extents of view. The superolateral extent was measured relative to the midline, as defined by the nasal process of the maxilla. The height of the clivus, odontoid tip, and superior aspect of the C-1 arch were also measured relative to the palatal line. A correlated clinical case is presented with video. RESULTS The CVJ was accessible in all cases. The superior extent of the approach was a mean 19.08 mm above the palatal line (range 11.1-27.7 mm). The superolateral extent relative to the midline was 15.45 mm on the right side (range 9.6-23.7 mm) and 16.70 mm on the left side (range 8.1-26.7 mm). The inferior extent was a mean 34.58 mm below the palatal line (range 22.2-41.6 mm). The mean distances were as follows: palatal line relative to the odontoid tip, 0.97 mm (range -4.9 to 3.7 mm); palatal line relative to the height of the clivus, 4.88 mm (range -1.5 to 7.3 mm); and palatal line relative to the C-1 arch, -2.75 mm (range -5.8 to 0 mm). CONCLUSIONS The endoscopic transoral approach can reliably access the CVJ. This approach avoids the dissections and morbidities associated with a palate-splitting technique (velopharyngeal insufficiency) and the expanded endonasal approach (mucus crusting, sinusitis, and potential lacerum or cavernous-paraclival internal carotid artery injury). For appropriately selected lesions near the palatal line, the endoscopic transoral approach appears to be the preferred approach.