Two consecutive intersegmental arteries (ISA) sharing a common origin from a single intersegmental trunk is a frequent anatomic variation. Ipsilateral intersegmental trunks are divided into complete and incomplete forms. In the classic form of incomplete trunk, the dorsospinal artery (DA), missing at one of the levels supplied by the trunk, arises separately from the aorta. This configuration is known as an isolated DA or a direct emergence of the DA from the aorta. Three angiographic observations of a different form of incomplete ipsilateral trunk are reported here, in which only the spinal component of the DA is arising separately from the aorta. This variant corresponds to the adult persistence of the ISA in its most primitive form. If overlooked, an isolated spinal branch may represent a diagnostic pitfall during angiography, in particular when the variant provides blood supply to the spinal cord or to a spinal vascular malformation.

Two consecutive intersegmental arteries (ISA) sharing a common aortic origin from a single intersegmental trunk is a frequent anatomic variation.1 These ipsilateral intersegmental trunks are divided into complete and incomplete forms.2 To be complete, an ISA trunk must have a complete set of branches for each of the vertebral levels it supplies; these include (i) an anterior component (or aortic stem) providing the anterior-lateral group of osseous arteries for the vertebral body, (ii) a lateral component (named lumbar, subcostal or intercostal artery depending on the level considered) and (iii) a dorsospinal artery (DA), itself consisting of a dorsal component vascularizing the paraspinal musculature, and a spinal component providing the radicular artery.

In the classic form of incomplete unilateral trunk, the DA is missing at one of the levels supplied by the trunk, arising instead separately from the aorta. This configuration, reported by Chiras and Merland3 in 1979, is known …