The External Carotid (Occipital)-Vertebral Anastomosis

Abstract

Though it is widely known that anatomically there exists a communicating channel between the carotid and vertebral arterial systems, this occipito-vertebral anastomosis can be hardly visualized by the conventional angiography and little has been reported about the angiographical demonstration of the anastomosis.
Two cases were presented in which the anastomosis was visualized by carotid and vertebral angiographies. The first case is a 15-year-old female and clinical diagnosis was a teratoma of the temporalregion on the left side. In this case the carotid angiography of the right side incidentally resulted in visualizing the external carotid system selectively and the occipito-vertebral anastomosis was demonstrated in the angiogram. The second case was also a 15-year-old female and was suffering from noncommunicating hydrocephalus of unknown origin. The left vertebral angiography by percutaneous procedure, revealed that basilar artery was occluded just proximal to its bifurcation and at the same time the external carotid system on the left side was also visualized through the anastomosis.
Significance of the anastomosing channel was discussed and it was suggested that the anastomosis could be a potential collateral channel which would function when the cerebral circulation was disturbed by intracranial pathological processes.