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Table of Contents    
Year : 2018  |  Volume : 66  |  Issue : 3  |  Page : 830-832

False localizing oculomotor nerve palsy after endovascular coiling of a posterior communicating artery aneurysm

1 Department of Neurology, Aster Medcity, Kochi, Kerala, India
2 Department of Neurointervention, Aster Medcity, Kochi, Kerala, India
3 Department of Neurosurgery, Aster Medcity, Kochi, Kerala, India

Date of Web Publication15-May-2018

Correspondence Address:
Dr. Boby V Maramattom
Department of Neurology, Aster Medcity, Kochi, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.232345

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How to cite this article:
Maramattom BV, Jayakrishnan V, Panikar D, Sundar S S. False localizing oculomotor nerve palsy after endovascular coiling of a posterior communicating artery aneurysm. Neurol India 2018;66:830-2

How to cite this URL:
Maramattom BV, Jayakrishnan V, Panikar D, Sundar S S. False localizing oculomotor nerve palsy after endovascular coiling of a posterior communicating artery aneurysm. Neurol India [serial online] 2018 [cited 2022 Oct 1];66:830-2. Available from: https://www.neurologyindia.com/text.asp?2018/66/3/830/232345


False localizing signs (FLS) are potentially misleading clinical signs that occur at a distance from the predicted site of anatomic localization in the brain. FLS have been described as occurring in association with raised intracranial pressure (ICP), spinal cord lesions, or diaschisis. Abducens nerve palsies are the commonest FLS.[1] Oculomotor FLS are rare.

A 38-year old lady presented to us with a thunderclap headache and a computed tomography (CT) angiogram showing a partially thrombosed left posterior communicating (PCom) aneurysm. On examination, she had a Glasgow Coma Scale (GCS) of 15. Both pupils were equal in size and reacting well to light. A four-vessel digital subtraction angiography (DSA) showed a fusiform irregular, dissecting PCom aneurysm (1.68 × 1.48 cm) extending from the PCom origin at the internal carotid atery (ICA). Magnetic resonance imaging (MRI) of the brain showed the aneurysm to be indenting the left uncus [Figure 1].
Figure 1: T2-weighted a.axial and b.sagittal MR images showing the large left PCom aneurysm lying in the space of Bichat and indenting the left uncus

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She underwent endovascular coiling of the left PCom aneurysm under general anesthesia. The filling portion of the partly thrombosed fusiform aneurysm was accessed using SL 10/18, synchro14 wires. Guglielmi detachable coils (GDC) 0 18 and soft target coils were used to pack the aneurysm. Good angiographic occlusion was noted on final angiograms. Anesthesia was reversed and she was extubated in the intensive care unit (ICU) with a Glasgow Coma Scale (GCS) score of 15. Three hours later, she suddenly vomited, her blood pressure (BP) increased to 210/130 mm Hg, and she became comatose. A dilated unreactive pupil was noted on the right side. An urgent computed tomographic (CT) scan of the brain showed a fresh subarachnoid hemorrhage in the subarachnoid cisterns [Figure 2]. A repeat DSA showed a coiled and completely occluded left PCom aneurysm without contrast extravasation. A generalized reduction in the intracranial flow was noted, suggestive of massively raised intracranial pressure (ICP). The aneurysm size had increased to 1.81 × 2.15 cm. A repeat CT scan of the brain after 2 h showed features of right uncal herniation (UH) [Figure 2]. Over the next 3 h, her left pupil also became dilated and unreactive and she gradually lost her brainstem reflexes. She expired the next morning.
Figure 2: The upper panel show the right-sided pupil dilatation. The lower panels show the axial CT scan images at the level of the tentorial opening. The first CT scan image shows a relatively normal paramesencephalic cistern. The second image shows bowing of the paramesencephalic cistern by the herniating uncus

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Ipsilateral oculomotor nerve (ON) palsies in intracranial lesions often occur in the context of uncal herniation (UH). The nerve has been shown to be susceptible to direct compression by the uncus during transtentorial herniation, or indirectly when the posterior cerebral artery (PCA) is displaced downward by the uncus, constricting the ON in between itself and the superior cerebellar artery (SCA).[2] However, contralateral ON palsy occurring as an FLS is very rare.[3],[4]

Contralateral ON palsy occurs if the contralateral tentorial opening [the space of Bichat (SOB)] is wider than the ipsilateral opening. Therefore, contralateral UH occurs before ipsilateral UH. Alternatively, an inferiorly located intracerebral lesion may rotate the midbrain in the coronal plane (roll plane) and cause contralateral midbrain descent and ON traction.

Our patient had a giant PCom aneurysm that enlarged in size after endovascular coil delivery. Aneurysm management utilizing an endovascular technique is now being increasingly used in India.[5] In our patient, the aneurysm–coil complex was wedged between the diaphragma sella and tentorium cerebelli in the ipsilateral SOB, just anterior to the cerebral peduncles, buttressing the uncus. Early UH can be picked up on the CT scan by radiological signs such as encroachment of the uncus on the suprasellar cistern, displacement of the brain stem, enlargement of the ipsilateral subarachnoid space between the free edge of the tentorium, and the lateral edge of the midbrain (SOB), and compression of the contralateral cerebral peduncle.[6] Conventionally, a mass lesion or raised ICP would have resulted in ipsilateral UH. However, in our patient, the alteration of SOB anatomy by the aneurysm–coil complex predisposed the contralateral uncus to herniate by buttressing the ipsilateral space. Moreover, the coil mass would have influenced the midbrain to tilt to the right in the roll plane with contralateral UH and ON compression [Figure 3]. The sequential pupillary dilatation in the context of raised ICP made a nuclear or fascicular third nerve lesion unlikely.
Figure 3: Panel A shows uncal herniation ipsilateral to a hemispheric lesion. Panel B shows the contralateral uncal herniation as the ipsilateral space of Bichat is buttressed by the aneurysm–coil complex

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In our patient, post-endovascular coiling metal artifacts obscured the brainstem rotation on CT scans. However, contralateral UH was well-demonstrated as the cause of a false localizing oculomotor palsy.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Larner AJ. False localising signs. J Neurol Neurosurg Psychiatry 2003;74:415-8.  Back to cited text no. 1
Maramattom BV, Wijdicks EF. Uncal herniation. Arch Neurol 2005;62:1932-5.  Back to cited text no. 2
Marshman LAG, Polkey CE, Penney CC. Unilateral fixed dilation of the pupil as a false-localizing sign with intracranial hemorrhage: Case report and literature review. Neurosurgery 2001;49:1251-5.  Back to cited text no. 3
Chen R, Sahjpaul R, Del Maestro RF, Assis L, Young GB. Initial enlargement of the opposite pupil as a false localising sign in intraparenchymal frontal haemorrhage. J Neurol Neurosurg Psychiatry 1994;57:1126-8.  Back to cited text no. 4
Gupta V, Parthasarathy R, Jha AN. Endovascular reconstruction of aneurysms with a complex geometry. Neurol India 2016;64(Suppl):S24-31.  Back to cited text no. 5
Osborn AG. Diagnosis of descending transtentorial herniation by cranial computed tomography. Radiology 1977;12:393-6.  Back to cited text no. 6


  [Figure 1], [Figure 2], [Figure 3]


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