Anatomical study of occipital triangles: the 'inferior' suboccipital triangle, a useful vertebral artery landmark for safe postero-lateral skull base surgery.

IST is a significantly large anatomical space where the VA course is rather regular, and its length is sufficient for vascular proximal control purposes. Periarterial venous plexus is less evident at this level, easing the surgical exposure. VA exposition within the IST can be used as an alternative option when space-occupying lesions, scars and stabilisation devices make arterial dissection hazardous in more cranial V3 segments.