The Suboccipital Triangle. The left suboccipital triangle has been exposed by reflecting the sternocleidomastoid and splenius and longissimus capitis muscles. The triangle is bordered by three muscles: the inferior oblique below, the superior oblique above, and the greater posterior rectus muscle of the head (Rectus. Cap.) medially. The segment of the left VA within the triangle is covered by the cervical and vertebral venous plexus. The segment of the VA, ascending between C-1 and C-2, is exposed below the inferior oblique muscle and the greater occipital nerve. The VA is inclined laterally as it ascends between the C-2 and C-1 transverse processes. (Images courtesy of AL Rhoton, Jr.)