Variability of the arteries of the brain is present to a considerable extent. This includes transitory or primitive carotid-vertebrobasilar anastomoses (proatlantal intersegmental, hypoglossal, trigeminal, and otic arteries), which distribute blood from the primitive internal carotid artery to the vertebrobasilar system in the embryonic period and undergo involution in the embryo from 7 to 12 mm. Their persistence may be associated with altered blood flow between the anterior and posterior cranial circulation or with the suppression of the development of definite brain arteries. Persistent primitive arteries can be found during anatomical or surgical dissection of the neck, or on angiograms of patients with some cerebral aneurysm or other pathological process, or accidentally in people with unspecified symptomatology. The clinical significance of arterial fenestrations and infundibular dilatations is controversial. Their independent or simultaneous presence in the carotid and vertebrobasilar systems is possible, although these two systems have different embryonic origin. Comparison of brain arteries with aneurysms simultaneously with hypoplasia or aplasia poses a challenge to autopsy and radiological studies.

The above, in addition to other variations of cerebral vessels in adults, whether or not associated with aneurysms and other pathological processes, constitute the focus of this special issue. We encourage morphologists, neurosurgeons, and neuroradiologists, as well as neurologists, to submit original research or review articles which contribute to creating a clearer picture of the (non)connection of these variations to different pathological processes.

Potential topics include but are not limited to the following:

• Quantitative anatomy and morphometric studies of persistent embryonic and other variable brain arteries
• Histological analysis of persistent embryonic and other variable brain arteries
• Clinical observations about interesting cases of persistent embryonic and other variable brain arteries during surgical procedures
• Observation of persistent embryonic and other variable brain arteries in the use of modern radiological methods
• Comparison of the presence of persistent embryonic and other variable brain arteries in the sick and healthy population
• Neurological consideration of the significance of persistent embryonic and other variable brain arteries for the quality of life and survival