Persistent primitive olfactory artery.

I have read with great interest the paper recently published in your journal by Uchino et al. [5] describing the persistent primitive olfactory artery (POA). In the anatomical paper on cerebral arteries, two important points are required. One is description of the detailed arterial anatomy (static anatomy). In this sense, new information of the incidence of the POA being 0.14% and no laterality is provided. Another important point is embryological description to facilitate understanding of the anatomy and its variations (functional anatomy). In the latter sense, there is a serious misunderstanding of the POA in this paper, as well as the preceding papers [2, 4]. In these papers, it is described that the remnant of the POA is the recurrent artery of the Heubner (RAH), all of which quoted Padget’s paper inappropriately [3]. Embryologically, the early brain vesicles are supplied by the primitive internal carotid artery, which is further divided into the rostral and caudal divisions (Fig. 1). The rostral division supplies the prosencephalon (rhinencephalon in lower vertebrates, thus the artery is called the olfactory artery), and constitutes the POA [3]. The POA terminates in the nasal fossa and the secondary artery constitutes the medial olfactory artery, which supplies the olfactory bulb (Fig. 2). The medial olfactory artery becomes the anterior cerebral artery proper, while the terminal portion of the POA usually regresses. Lateral olfactory branches of the POA include the RAH, anterior choroidal artery, lateral striate artery, and later middle cerebral artery [1] (Fig. 3). When the terminal portion of the POA does not regress, it is called the persistent POA. There are two types of the persistent POA [2]: type 1 artery has a hairpin turn along the olfactory bulb coursing postero-superiorly to become the distal anterior cerebral artery, and type 2 artery enters the nasal cavity and connects with the ethmoidal artery (Fig. 4). Type 2 artery is homologous to the internal ethmoidal artery in dogs. The RAH is an old branch of the lateral olfactory branches of the POA, supplying the rostral corpus striatum and internal capsule, which are completely different from the olfactory lobe. Embryologically, the POA is the rostral division of the primitive internal carotid artery. The POA constitutes the anterior cerebral artery proper, and when the POA keeps its