Cavernous internal carotid artery aneurysm treated with superficial temporal artery–middle cerebral artery bypass and cervical internal carotid artery ligation using intraoperative middle cerebral artery pressure monitoring: illustrative case

BACKGROUND: Symptomatic cavernous portion internal carotid artery (ICA) aneurysms require prompt treatment due to their neurological impact. The authors report a case successfully treated with ICA ligation and superficial temporal artery-middle cerebral artery (STA-MCA) bypass, guided by intraoperative cortical/systemic pressure and MCA pressure ratios before and after bypass release to prevent infarction, achieving complete aneurysm obliteration without deficits. OBSERVATIONS: An 84-year-old woman presented with sudden-onset headache and right external ophthalmoplegia. Imaging studies revealed a 24-mm aneurysm in the right ICA within the cavernous sinus and a 13-mm aneurysm in the left ICA cavernous segment. Severe common carotid artery atherosclerosis made endovascular treatment challenging. Preoperative cervical CT also revealed a 45-mm × 33-mm benign right thyroid mass, increasing the risk of cervical manipulation. ICA ligation with high-flow bypass was considered high-risk; therefore, ICA ligation with STA-MCA bypass was performed. Intraoperative cortical/systemic pressure and MCA pressure ratios after ligation and two STA-MCA anastomoses were 0.77 and 0.87, respectively, indicating low ischemic risk. Postoperatively, no new deficits occurred, and ophthalmoplegia improved. LESSONS: Intraoperative measurement of cortical/systemic and MCA pressure ratios, combined with thorough preoperative evaluation, can help assess ischemic risk and improve surgical safety. https://thejns.org/doi/10.3171/CASE25630.