Upper back of neck, inferior to occipital region of head and above the level of the second cervical vertebra; overlies (or includes, deeply) the suboccipital triangle.

Awareness of the angioarchitecture of the suboccipital region and the existence of patent vertebrocarotid anastomotic connections is important to avoid complications during surgical or endovascular interventions. When present, a pre-existing occipital artery (OA) -PICA anastomosis can be exploited to facilitate treatment in certain vascular pathologies (eg, vertebral artery aneurysms). Awareness of the existence of both an extradural origin of the PICA and a direct connection of this vessel with the OA is of great relevance to the muscular stage of surgical approaches to the posterior craniovertebral junction ¹⁾.