A Case of the Internal Carotid Artery–Posterior Communicating Artery Aneurysm Mimicking Tolosa–Hunt Syndrome

Abstract

aneurysm, and not of a giant intracavernous aneurysm, is extremely rare. 5–7) In this case report, we describe a patient with a non-giant internal carotid artery–posterior communicating artery (ICA-PCoA) aneurysm presenting with ophthalmoplegia in all directions with concomitant severe ocular pain, thus mimicking Tolosa–Hunt syndrome. The patient's aneurysm had a spindling and irregular shape that presumably enlarged rapidly to cause oculomotor and abducens nerve palsies simultaneously. Case Report A 53-year-old woman with no past medical history sud-denly started to see some colorful and glaring waves in the upper visual field of the right eye lasting for seconds. A few hours later, she began to feel moderate pain in the back of the right eye. Because she began to have diplopia and photo-phobia on the fourth day after the onset, she visited our hos-pital. Although the size of pupils and light reflex were normal and ptosis was not observed, right ocular movement was obviously impaired in all directions. The position of the right eye was slightly deviated laterally, but she could not move it to the right. She had no history of diabetes mellitus. A plain computed tomography (CT) scan of the head reveal no abnormality such as a giant intracavernous aneurysm, subarachnoid hemorrhage, or a parasellar tumor (Fig. 1A). Because her symptoms consisted of painful ophthalmoplegia in all directions, her condition was tentatively diagnosed as Tolosa–Hunt syndrome. We scheduled elective magnetic res-onance (MR) imaging for her and sent her to a neurologist at our hospital. On the next day, however, she developed right eye ptosis and returned to our hospital. At this time, the right pupil was dilated and light reflex was absent on the right side, indi-cating right complete oculomotor nerve palsy. Her emergency MR images (enhanced T1 3D FLASH, slice thickness 0.8 mm, TR 16 msec TE 4.91 msec) confirmed an irregularly shaped ICA-PCoA aneurysm. A cerebral angiogram showed a vertically long aneurysm measuring approximately 10 mm in its longest dimension with complicated bulges projecting postero-infero-laterally (Fig. 1B, C). No other intracranial abnormalities, including cavernous sinus lesions, were found. On the basis of diagnosis of the ICA-PCoA aneurysm causing oculomotor and abducens nerve palsies, we per-formed emergency open craniotomy and clipping of the aneurysm. Two-thirds of the aneurysm dome was buried behind the dura and projected toward the lateral cavernous sinus (Fig. 2A). The first bulge of the aneurysm compressed A 53-year-old woman experienced a right retrobulbar pain followed by ipsilateral extraocular palsies in all directions without dilated pupils or ptosis. Because a plain head computed tomography (CT) scan obtained on her initial visit showed no abnormal findings, such as subarachnoid hemorrhage or a giant cavernous aneu-rysm, her condition was provisionally diagnosed as Tolosa–Hunt syndrome and elective magnetic reso-nance (MR) imaging was scheduled. The day after her initial visit, however, she suddenly developed complete ptosis and a dilated pupil on the right side. Emergency MR imaging and angiography revealed a clover leaf-shaped aneurysm projecting to the cavernous sinus at the junction of the internal carotid artery and the poste-rior communicating artery. Her condition was diag-nosed as impending rupture of the aneurysm, and she underwent emergency open surgery. Her symptoms completely resolved within the following 2 weeks. Our case demonstrated that a medium-sized internal carotid artery–posterior communicating artery aneurysm can cause simultaneous oculomotor and abducens nerve palsies with retrobulbar pain if the shape of the aneu-rysm is complicated. Although these symptoms are very similar to those of Tolosa–Hunt syndrome, we believe that prompt radiological examinations such as MR or 3D CT angiography should be performed to prevent subse-quent rupture of the aneurysm.