J Korean Med Sci 2007; 22: 173-6 ISSN 1011-8934 Copyright The Korean Academy of Medical Sciences Ruptured Anterior Communicating Artery Aneurysm Causing Bilateral Oculomotor Nerve Palsy : A Case Report A rare case of bilateral third cranial nerve palsy due to a ruptured anterior commu- nicating artery aneurysm is presented. A 68-yr-old woman was semicomatose with bilaterally fixed dilated pupil, abducted eyes, and ptosis. A computed tomography demonstrated extensive hemorrhage spreading around the both Sylvian and inter- hemisheric fissure without focal mass effect. Intracranial pressure via extraventricu- lar drainage before surgery was 15-50 mmHg. Three months later, brain MRI showed infarction of left posterior cerebral artery territory and lacuna infarction of the pons. Eleven months after aneurysm repair, nerve palsy improved slowly and recovered partially. The patient communicated well with simple words. The author reviewed and discussed the possible mechanism of this rare neuro-ophthalmological manifesta- tion in view of a false localizing sign. Key Words : Oculomotor Nerve; Paralysis; Palsy; Anterior Communicating Artery; Intracranial Aneurysm Sung Don Kang Department of Neurosurgery, School of Medicine, Institute of Wonkwang Medical Science, Wonkwang University, Iksan, Korea Received : 29 August 2005 Accepted : 21 November 2005 Address for correspondence Sung Don Kang, M.D. Department of Neurosurgery, Wonkwang University Hospital, 344-2 Sinnyong-dong, Iksan 570-711, Korea Tel : +82.63-850-1268, Fax : +82.63-852-2606 E-mail : kangsd@wonkwang.ac.kr *This paper was supported by Wonkwang University in 2006. INTRODUCTION The oculomotor nerve dysfunction is a well recognized manifestation of the internal carotid-posterior communicat- ing artery (ICA-PComA) junction aneurysm and is consid- ered to be a valuable localizing sign caused by direct pressure on the nerve. Remote intracranial aneurysms from the ocu- lar motor system may also occasionally cause ocular motor disturbance, most commonly abducens nerve palsy, which has been known to be simply a false localizing sign due to general intracranial hypertension (1, 2). The author reviewed and discussed the possible mecha- nism of this rare bilateral third cranial nerve palsy due to a ruptured anterior communicating artery (AComA) aneurysm in view of a false localizing sign. CASE REPORT A 68-yr-old female was found unconscious. She was intu- bated and ventilated. Pulse rate and blood pressure were 68 beats per minute and 130/80 mm Hg, respectively. There was no history of diabetes mellitus, hypertension, heart dis- ease, stroke, or cancer. On neurological examination, she was semicomatose with flexion to painful stimulation. Both pupils appeared centrally fixed, dilated (6 mm), and nonreactive to 173 direct or indirect light stimuli. Computed tomographic (CT) scanning demonstrated extensive subarachnoid hemorrhage spreading around the both Sylvian, basal, and interhemisphe- ric cistern (Fig. 1). Emergency extraventricular drainage (EVD) was performed. Initial intracranial pressure (ICP) was 45 mm Hg, and subsequently, the pressure remained between 15 and 25 mm Hg after intermittent cerebrospinal fluid (CSF) drai- nage. Seven hours after EVD, the right pupil became reac- tive to light, but left pupil was nonreactive to light with 4 mm in size. A digital subtraction angiogram revealed a sac- cular aneurysm on the AComA (Fig. 2). The patient under- went an operation on the next day via left pterional approach. After opening the Sylvian fissure, it was observed that the basal cistern was obstructed with clot. The aneurysm could be safely dissected and was successfully clipped. No additional neurological deficits were observed postoperatively. She was maintained with continuous EVD. On the 5th postopera- tive day, both pupils were dilated (6 mm) with sudden ele- vation of ICP to 50 mm Hg during temporary closure of ventricular catheter. Follow-up CT scan showed no signifi- cant change. Thereafter, the right pupil gradually decreased (2 mm) and reacted to light but the left one was still dilated without direct or indirect light reflex, in which pupil size changed a little in accordance with intermittent ventricular drainage. The ventricular catheter was removed on the 14th postoperative day when it was still measured at 25 mm Hg.