[Anomalies of the basilar and vertebral arteries that are of practical importance].

Anomalies of vertebrobasilar vessels arise as early embryonal developmental deteriorations. The majority of them concerns the position, origin and shape of the vertebral and/or basilar arteries. In three patients, reported here, the aberrations were found occasionally and contributed in no way to the clinical symptomatology. In the first patient, a fenestration of A. basilaris was found with a fork-like division on its periphery. In the second patient we noted a doubled proximal origin of the vertebral artery. One artery arose from A. subclavia sinistra, the second one from the aortic arch. Both joined thereafter the common vertebral stem at the level of C4. In the third patient, A. vertebralis originated from the aortal arch, and, at the level of the thyroid, A. thyreoidea inferior originated from it. Attention is drawn to the practical importance of such variations as a possible source of diagnostic errors during cerebral arteriography.