Intrasellar trigeminal artery.

A case of pituitary macroadenoma is presented in which correct preoperative CT recognition of a persistent trigeminal artery piercing the dorsum sella prompted angiographic evaluation. MR was then used to further examine the intrasellar course of the anomalous vessel. A search of the English literature failed to disclose previous CT or MR demonstration of a persistent trigeminal artery. A 19-year-old man with clinical and biochemical evidence of Cush-ing syndrome was referred to the neurosurgery department at our institution. An infused CT scan with 1.5-mm axial and coronal images through the sella performed before surgery showed a low-attenuation intrasellar adenoma situated centrally and to the right. A high-density tubular structure branched from the basilar artery, continued parallel to the dorsum sella for a short distance, and then pierced the left side of the dorsum. The structure could not then be separated from the cavernous sinus on the left side. Coronal sections of the dorsum sella with bone windowing showed a rounded , well-marginated defect. The neurosurgeons were alerted to the probable presence of an anomalous vessel, and preoperative angiography showed a persistent trigeminal artery. (Fig. 1A). MR images were obtained in three orthogonal planes. The pituitary adenoma was inhomogeneous and isointense with brain on T1-weighted images and was hyperinterce on T2-weighted images. As was the case with CT, axial images showed the persistent trigeminal artery piercing the dorsum sella to the left of midline but medial to the posterior clinoid process and oculomotor nerve. The flow void of the artery had a short intrasellar course before joining the intracav-ernous carotid artery on its medial surface (Figs. 1 B-1 D). Although the medial dural wall of the left cavernous sinus was not clearly apparent on any of the MR images, the intrasellar portion of the persistent trigeminal artery was visualized directly and avoided during successful transphenoidal surgery. Discussion The persistent trigeminal artery is the most common of the persistent fetal carotid-basilar anastomoses; the prevalence is 0.1-0.2% A B Fig. 1.-lntrasellar trigeminal artery. [1]. It arises from the immediate precavernous or intracavernous internal carotid artery proximal to the meningohypophyseal trunk and usually joins the distal third of the basilar artery between the superior cerebellar artery and the anterior inferior cerebellar artery. Anatomic dissections have shown variation in the course of the persistent trigeminal artery [2-6]. The usual intracavernous course is from the posterolateral wall of the carotid artery to the posterior dural surface …