[Fenestration of the internal carotid artery in the neck].

Fenestration or duplication of the internal carotid artery is extremely rare. A review of the literature revealed only two such cases by angiography. We present two further cases of internal carotid artery fenestration, incidentally disclosed by angiography. The embryological basis and the clinical significance of this anomalous condition were discussed. Case 1. A 47-year-old woman was admitted to hospital on May 13, 1982, after the first attack of subarachnoid hemorrhage. Four-vessel angiography showed a saccular aneurysm arising at the trifurcation of the right middle cerebral artery. In addition, a fenestration of the right internal carotid artery was demonstrated at the level of the atlas: the cervical portion of the vessel distal to the level of C-2 was markedly elongated and dilated in caliber. Moreover, the right external carotid artery occupied a dorso-lateral position relative to the internal carotid artery. Case 2. A 51-year-old man was admitted to hospital on April 20, 1983, for evaluation of grand mal seizures. CT scans and four-vessel angiograms showed a malignant glioma of the right temporal lobe. Additionally, a fenestration of the right internal carotid artery was identified at the level of the atlantoaxial joint, and the vessel was dilated in caliber at the level of C-1 to C-2.