The artery of von Haller: A constant anterior radiculomedullary artery at the upper thoracic level

BACKGROUND: Although recognized since the 18th century, radiculomedullary arteries (RMAs) originating from upper thoracic intersegmental arteries are generally considered to be inconstant branches of little clinical importance. Yet, such vessels are commonly observed during spinal angiography. OBJECTIVE: To evaluate the angiographic prevalence of upper thoracic RMAs, in particular, branches supplying the anterior spinal artery (ASA). METHODS: Fifty spinal angiograms were reviewed. Anterior and posterior RMAs originating in the upper thoracic region (T3 to T7) were recorded. The level of origin of the artery of Adamkiewicz (T8 to L3) was also noted. RESULTS: Forty-three patients (86%) had at least 1 ASA contributor between T3 and T7. Of the other 7 patients, 4 had one at an immediately adjacent level (T2 or T8). The most frequent origin of upper thoracic anterior RMAs was left T5 (n = 10). Only left T9 (n = 12) and left T8 (n = 11) were more common. When combining the left and right sides, an ASA contributor was more frequent at T5 (n = 16) than at any other level (n = 15 for T9, n = 14 for T8). The sum of ASA contributors at T4 and T5 (n = 27) represented 54% of all upper thoracic anterior RMAs, and 23% of all anterior RMAs between T3 and L3. CONCLUSION: A significant upper thoracic anterior RMA distinct from the artery of Adamkiewicz appears to be a constant anatomic feature, which undermines the classic concept of an arterial watershed zone in the thoracic region. We propose to name this artery after Albrecht von Haller, who documented its existence in 1754.