Case ReportUnruptured medial paraclinoid internal carotid artery aneurysm embedded within symptomatic nonfunctioning pituitary giant adenoma: A high-risk comorbid pathology in transsphenoidal surgery and its countermeasures

•Coil embolization can manage a medial paraclinoid internal carotid artery (ICA) aneurysm as a preoperative procedure for TSS.•A medial paraclinoid ICA aneurysm can appear directly under the sellar floor as an apparent extradural aneurysm.•Surgeons should take great care in procedures near a coil-embolized aneurysm because the wall can be thin transparent.

BackgroundInjury of the internal carotid artery (ICA) in the cavernous portion is one of the most critical complications of transsphenoidal surgery (TSS), especially in cases of coexistence with a pituitary adenoma (PA) and ICA aneurysm.Case descriptionWe present a rare case of unruptured medial paraclinoid ICA aneurysm (ICA-An) associated with symptomatic nonfunctioning giant PA. After endovascular coil embolization of the unruptured 4-mm saccular medial paraclinoid ICA-An, the patient underwent adenomectomy through an endoscopic endonasal TSS. During the bone resection over the right sellar floor near the right cavernous sinus, a tangle of packed coils in the treated medial paraclinoid ICA-An was observed immediately after a bite of a Kerrison rongeur. The dural layer over the coiled aneurysm had become thin to the point of transparency or complete absence. Careful inspection revealed that the bone hillock was formed by the medial paraclinoid ICA-An. Gross total resection of the adenoma was achieved without vascular injuries related to the coiled aneurysm despite postoperative transient right oculomotor paresis.ConclusionsThis case conveys three important lessons about TSS: 1) coil embolization will manage a medial paraclinoid ICA-An as a sufficient preoperative procedure for TSS; 2) a medial paraclinoid ICA-An can appear directly under the sellar floor as an apparent extradural aneurysm; and; 3) surgeons should take great care in procedures near a coil-embolized medial paraclinoid ICA-An because the aneurysmal wall can be thin to the point of transparency.