C1 anterior arch preservation in transnasal odontoidectomy using three-dimensional endoscope: A case report

Abstract

Background: The transoral ventral corridor is the most common approach used to reach the craniovertebral junction (CVJ). Over the last decade, many case reports have demonstrated the transnasal corridor to the odontoid peg represents a practicable route to remove the tip of the odontoid process. The biomechanical consequences of the traditional odontoidectomy led to the necessity of a cervical spine stabilization. Preserving the inferior portion of the C1 anterior arch should prevent instability.

Case description: This is the first report in which the technique to remove the tip of the odontoid while preserving the C1 anterior arch is described by means of a three-dimensional (3D) endoscope. A 53-year-old man underwent a transnasal 3D endoscopic approach because of a complex CVJ malformation. The upper-medial portion of the C1 anterior arch was removed preserving its continuity, and the odontoidectomy was performed. After surgery, a dynamic X-ray scan showed no difference in CVJ motility in comparison with the preoperative one.

Conclusions: The stereoscopic perception augmented the precision of the surgical gesture in the deep field. The importance of a 3D view relates to the depth of field, which a two-dimensional endoscopy cannot provide. This affects the preservation of the C1 anterior arch because of the presence of critical structures that are exposed to potential damage if not displayed.

Keywords: C1 anterior arch preservation; craniovertebral junction stability; three-dimensional endoscope; transnasal odontoidectomy.

Figure 1

Preoperative magnetic resonance imaging and computed tomography showing a complex craniovertebral junction malformation with basilar impression and radiological signs of myelopathy at C2 level

Figure 2

Preoperative dynamic cervical spine X-ray showing no instability of the craniovertebral junction ((a) static, (b) hyperextension, (c) hyperflexion)

Figure 3

Intraoperative endoscopic views: (a) C1 anterior arch upper portion drilling; the arrow points out the residual lateral part of the arch (b) final endoscopic view after the odontoidectomy is completed showing the spinal cord dura just behind the drilled portion of the dens (c) the white arrow indicates the dura

Figure 4

Dynamic X-ray with anterior atlas-dens interval and posterior atlas-dens interval performed before discharge showed no instability of the craniovertebral junction

Figure 5

Postoperative dynamic computed tomography (b,c) and magnetic resonance (a) imaging demonstrated the achievement of a good spinal cord decompression

Figure 6

Static (a) and dynamic (b,c) X-ray 18 months after discharge confirming that there was no instability of the craniovertebral junction