Multichannel fenestration of the petrous and cavernous segments of the internal carotid artery associated with two small carotid canals

Abstract

A fenestration is defined as a division of the arterial lumen into distinctly separate channels, each with its own endothelial and muscularis layers, while the adventitia may be shared. Duplication, by contrast, is defined as two distinct arteries with separate origins and no distal arterial convergence. Fenestrations can range from a small focus of divided tissue to long segment duplications. They are the result of partial failure of fusion of paired primitive embryologic vessels or incomplete obliteration of different anastomosis in a primitive vascular network [1]. Fenestration, or duplication, of the internal carotid artery (ICA) is considered as an extremely rare anatomic variant. The prescens of greater than two channels in a long segment of the ICA has not been previously described. We report a case of multichannel fenestrations of the petrous and cavernous segments of the ICA associated with two small carotid canals. A 58-year-old man with no remarkable medical history was admitted to the Department of Neurology for transient ischemic attack involving the right upper extremity. At admission, his general and neurologic examinations were normal. Brain CT findings were unremarkable expect for narrow right carotid canal (Fig. 1). The inferior part of the carotid canal was divided by a bony septum into two smaller canals. CT angiography revealed hypoplastic cervical segment of the right ICA and multiple vessels in the petrous canal, and parasellar area converging to the intradural paraclinoid segment of the ICA (Fig. 2). Digital subtraction angiography (DSA) was performed. Right carotid angiogram (Fig. 3a, b) demonstrated small caliber of ICA, including the first (cervical) and second (ascending petrous) segment. Distally, four tortuous vessels with a diameter of 1–2 mm were found along the course of the third (horizontal intrapetrous), fourth (ascending intrapetrous and in foramen lacerum) and fifth (horizontal segment of the carotid siphon) segments. These vessels converged to the sixth (clinoid) segment. The seventh (supraclinoid) segment of ICA and medial cerebral artery were normal. There was hypoplasia of the A1 segment of the anterior cerebral artery. Selective right external carotid artery showed no abnormalities. Angiograms of the left carotid and both vertebral arteries were normal. Our case describes developmental abnormalities of the petrous and cavernous portion of the ICA, consisted of four channel fenestrations associated with two small carotid canals. Fenestration or segmental duplication of the petrous and the cavernous segment of the ICA is considered an extremely rare anatomic variant. To the best of our knowledge, this is the first report of long-segment multichannel fenestration involving petrous and cavernous segments of the ICA. There is only one case of multichannel fenestrations of the petrous segment of the ICA reported by Mangla and Teitelbaum [2]. They described the shortsegment division of the petrous segment into four channels on DSA. The fenestration was approximately 1-cm long. Uchino et al. [3] have published the only case of intracavernous fenestration diagnosed by MR angiography and DSA. They described duplicate arterial lumens just proximal to the supraclinoid segment. Fenestrations in the supraclinoid and cervical segments are more common. D. Stojanov P. Bosnjakovic D. Benedeto-Stojanov S. Petrovic Faculty of Medicine, University of Nis, Nis, Serbia