Vessels supplying blood to the encephalon of the alpaca (Vicugna pacos)

Abstract Background Studies on the blood vessels of the brain in Cameliformes have largely focused on Old World camels, with limited data on New World species such as alpacas. The rostral epidural rete mirabile, a specialized arterial network at the base of the brain, plays a role in brain cooling, water conservation, and neurotransmitter transport in other ungulates. Alpacas are increasingly bred in Europe yet detailed anatomical descriptions of their cerebral arteries and the rostral epidural rete mirabile are lacking. This study aimed to analyze the blood supply to the encephalon in alpacas, with a focus on the rostral epidural rete mirabile, to provide insights relevant for anatomy, physiology, and veterinary care. Results The internal carotid artery enters the rostral epidural rete mirabile from the caudal side, accompanied by branches from the maxillary and external ophthalmic arteries. The paired rete is well-developed, located on the basal sphenoid bone, with 51–64 interconnecting vessels forming an elongated oval structure. Blood from the rete supplies the cerebral arterial circle, including the rostral cerebral artery and caudal communicating arteries. The rostral cerebral arteries are connected rostrally by the rostral communicating artery in most specimens. The caudal cerebral and cerebellar arteries, along with the basilar artery, supply the posterior cerebrum, brainstem, and cerebellum. Variations were observed in the presence and branching patterns of certain arteries, including unilateral or bilateral absence of caudal branches. The rete is embedded in the cavernous sinus, which has a spongy structure due to interspersed arterial vessels. Conclusions In alpacas, the brain is supplied by the internal carotid artery, the rostral and caudal branches to the rostral epidural rete mirabile, and the basilar artery. The vascular pattern remains constant during ontogenesis, with the internal carotid artery preserved in adults. The rostral epidural rete mirabile is well developed, especially in its rostral part, and embedded within the cavernous sinus. The cerebral arterial circle is formed by the rostral cerebral and caudal communicating arteries. The basilar artery plays a key role in maintaining adequate blood flow to the brain.