The almost horizontal obliquus capitis inferior is inserted on the transverse process of the atlas and originates from the spinous process of the axis (C2).
Obliquus capitis inferior is the biggest suboccipital muscle acting as an important homolateral rotator of the head in cervical dystonia (Schramm et al. 2014).
This thick muscle rotates the atlanto-axial joint for a narrow angle (nearly 10°): it is a strong head rotator and contributes to head movement related to fast visual exploration Castagna





OCI and vertebral artery Lateral view of the termination of the vertebral artery




Video 1. Injection of OCI with ultrasound guidance


Inject between the mastoid process and the second vertebrae in the direction of the opposite eye.