Interventional Neuroradiology 3: 283-288, 1997 Predictibility of the Cervical Origin of the Anterior Spinal Artery P. MERCIER, G. BRASSIER ** , D. FOURNIER, N. HENTATI, A. PASCO-PAPON*, X. PAPON Laboratoire d'Anatomie, Faculte de Medecine; Angers * Service de Radiologie A, H6pital Larrey, CHU; Angers ** Servi ce de Neurochirurgie, CHU Pontchaillou; Rennes Summary The anatomic study (under a surgical micro- scope) of 25 brains that had previously been in- jected with colored latex confirmed the fact that in the majority of cases, the anterior spinal artery results from the merging of two arterioles which both derive from two vertebral arteries. This bilateral nature is determined by the sym- metric origin of the posterior inferior cerebellar arteries. When the conformation is asymmetrical, a single anterior spinal artery branches off from the vertebral artery that supplies the closest pos- terior inferior cerebellar artery. Introduction The anterior spinal artery is classically de- scribed as being the result of two arterioles merging on the ventral aspect of the spino- medullary junction. The arterioles themselves branch off from two vertebral arteries. The work that was carried out by Stopford (1916), Adachi (1928), Lazorthes (1973), Domisse (1975), Crock (1977) and Thron (1988) showed that although this was the most frequently en- countered disposition, the anterior spinal artery is derived from a single vertebral artery in a certain number of instances. Thus it seemed interesting for us to ascertain the unilateral origin of the anterior spinal artery, and to correlate the unilateral or bilat- eral nature of the origin to the variations of the vertebral basilar system. Material and Methods We used 25 cephalic extremities which had first been injected with Winkler liquid, and then with 671 red neopren latex after arterial catheterization. In a few cases, a retrograde jugular catheterization was performed with blue latex in order to obtain a retrograde ve- nous injection. The brains were extracted 48 hours after the injection, by means of cervical laminectomy and an opening in the foramen magnum. This made it possible to section the right and left vertebral arteries at the level at which they penetrated the dura mater. The specimen were then examined under optical magnification (Wild Leitz or Zeiss opmi 16) and photographed (Contax 167 MT). Results Throughout this study, we classified the var- ious vertebral basilar junctions into five cate- gories: Type A : Both vertebral arteries have similar diameters. They merge on the midline, forming the basilar artery. Both posterior inferior cere- bellar arteries (pica) derive from the two verte- bral arteries. The anterior spinal artery (asa) de- rives from the merging of two small arterioles that come from the right and left vertebral ar- teries (figures 1, 2). Type B : Both vertebral arteries have similar diameters. They merge on the midline, forming the basilar artery. Both posterior inferior cere- bellar arteries (pica) derive either from the 283