Cerebellar arteries originating from the internal carotid artery.

PURPOSE To study the incidence of cerebellar arteries originating directly from the internal carotid artery, and to discuss the probable embryological origin and clinical implications of this anatomical anomaly. METHODS We reviewed 5500 angiographic studies done at our institution in the last 4 years, searching for these anomalous vessels as well as for other anatomical variants. RESULTS Eleven cerebellar arteries originating directly from the internal carotid artery and nine embryonic cerebral arteries were found. CONCLUSION These arteries are considered persistent trigeminal artery variants and seem to occur as the result of the persistence of a primitive trigeminal artery associated with an incomplete fusion of the longitudinal neural arteries. These anomalous vessels are clinically significant particularly because of their role in endovascular therapeutic and surgical complications and the paradoxical lesions in the cerebellum that occur as a result of carotid disease.