Report of intradural aneurysm in the cavernous segment of the internal carotid artery presented with subarachnoid hemorrhage and oculomotor palsy

BACKGROUND: Aneurysms of the cavernous segment of the internal carotid artery (ICA) do not usually cause subarachnoid hemorrhage (SAH). We report a patient who presented with this condition due to a ruptured aneurysm located on the posterior genu of the cavernous segment, raising the question of what factors could have led to such evolution. CASE DESCRIPTION: A 55-year-old male patient presented with sudden, intense thunderstorm headache, associated with complete palsy of the left oculomotor nerve and neck stiffness. Cranial computed tomography (CT) showed no SAH, but showed an expansive process in the sella turcica, consistent with a pituitary macroadenoma. After that, SAH was confirmed by lumbar puncture (Fisher I). Cranial angio-CT revealed an intradural saccular aneurysm in the cavernous segment of the left ICA. The patient underwent cranial microsurgery for cerebral aneurysm clipping. Unlike the normal anatomic pattern, the cavernous segment of the carotid artery in this patient was located in the intradural compartment. CONCLUSION: Intradural rupture of proximal cavernous segment carotid aneurysms is rare. We review the literate for such cases and discuss the possible causes.