We report a 42-year-old man suffering cavernous sinus syndrome with intracranial aneurysm suspected tobe infectious occurring after dental caries. He had a left side headache after draining pus from a carious tooth in the left maxilla. Two weeks later, he was admitted to our hospital and started on antibiotics. On the second hospital day, he showed left ptosis and paralysis of upward movement of the left eye. Head magnetic resonance imaging revealed soft tissue enhancement from the left cavernous sinus to the orbital apex, and we suspected Tolosa-Hunt syndrome. After intravenous methylprednisolone pulse therapy, his headache improved, but his left ptosis and ocular movement disorder worsened. 3D-computed tomography (CT) angiography and cerebral angiography revealed a left cavernous sinus thrombosis and internal carotid artery aneurysm (approximately 15 mm in diameter). Chest CT showed a small nodular shadow in the upper lobe of the left lung. Assuming an intracranial infectious aneurysm, internal carotid artery trapping and bypass surgery were performed on the 19th hospital day. Postoperatively, the aneurysm disappeared, and the external ophthalmoplegia reduced. We hypothesized that bacterial inflammation from the dental caries spread to the cavernous sinus via the intravenous route and formed an infectious internal carotid artery aneurysm.
