The Vertebral Artery Window in Endoscopic Ventral Craniovertebral Junction Surgery: Anatomy and Clinical Application.

OBJECTIVE: To define the "vertebral artery window" (VA window) and assess its anatomical basis, CTA depiction, laterality, and preliminary operative feasibility in endoscopic ventral CVJ surgery. METHODS: Fourteen fresh-frozen silicone-perfused cadaveric heads (28 sides) were examined through ventral and posterior approaches. Window dimensions, VA depth from the prevertebral fascia, and VA-to-landmark distances were measured. Cervical CTA datasets from 10 adults were assessed using the same convention. Paired left-right analyses were exploratory. Four endoscopic ventral CVJ procedures were retrospectively reviewed for feasibility. RESULTS: The VA window was consistently bounded by the jugular process, atlanto-occipital joint, C1 anterior arch, and rectus capitis lateralis muscle. Mean window height and width were 8.4 ± 1.3 mm and 6.5 ± 2.6 mm; the proximal horizontal V3 segment lay 5.3 ± 1.1 mm deep to the prevertebral fascia. Two cadaveric laterality comparisons remained statistically significant after Holm correction, but both paired mean differences were <2 mm; CTA showed no significant side differences. One C1 osteophyte narrowed the window. In all four procedures, the boundaries were identifiable and micro-Doppler confirmed the anticipated VA location. CONCLUSIONS: The VA window provides an osseomuscular framework for anticipating the proximal horizontal V3 segment during endoscopic ventral CVJ surgery. These findings support anatomical definition and preliminary operative feasibility, not clinical validation or improved surgical safety.