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Year : 2017  |  Volume : 25  |  Issue : 2  |  Page : 146-148

Presumed arachnoid cyst and acquired isolated third nerve palsy in a child-causal or incidental?

1 Sankara Eye Hospital, Bengaluru, Karnataka, India
2 University of Alberta, Edmonton, Alberta, Canada

Date of Web Publication22-Feb-2018

Correspondence Address:
Dr. Sowmya Raveendra Murthy
Department of Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Varthur Main Road, Kundlahalli Gate, Bengaluru
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njo.njo_12_17

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Arachnoid cysts and oculomotor palsy are rare occurrences in children. This report describes a case of acquired third cranial nerve palsy in a child, caused by compression of the oculomotor nerve by an arachnoid cyst. Nineteen-month-old female child presented with a history of squinting in the right eye. Magnetic resonance imaging (MRI) of the brain showed a small cystic lesion immediately adjacent to the cisternal segment of the oculomotor nerve. Immediate surgical intervention was deferred. Follow-up after 6 months showed progression of third nerve palsy with no change in size of the cyst. This case highlights the importance of performing neuroimaging to rule out the presence of compressive lesions in children with abnormal ocular motility and pupillary findings. Small insignificant lesions on MRI need to be followed up in such cases to explain the findings as in our case.

Keywords: Arachnoid cyst, oculomotor palsy, oculomotor nerve

How to cite this article:
Murthy SR, Murali K, Shanmugham MP, Sankar T. Presumed arachnoid cyst and acquired isolated third nerve palsy in a child-causal or incidental? . Niger J Ophthalmol 2017;25:146-8

How to cite this URL:
Murthy SR, Murali K, Shanmugham MP, Sankar T. Presumed arachnoid cyst and acquired isolated third nerve palsy in a child-causal or incidental? . Niger J Ophthalmol [serial online] 2017 [cited 2021 Jun 16];25:146-8. Available from:

  Introduction Top

Arachnoid cysts are congenital intracranial lesions consisting of clear fluid enclosed in reduplicated layers of arachnoid. They occur throughout the cerebrospinal axis and comprise approximately 1% of all intracranial space occupying lesions. They are usually asymptomatic, though they can rarely present with mass effect on surrounding structures or acute neurological deterioration due to intracystic hemorrhage.[1] The most common location for arachnoid cysts is in the middle cranial fossa in the region of the Sylvian fissure, followed by the posterior fossa.[1] Palsies of third, fourth, and sixth cranial nerves have been reported in association with intracranial arachnoid cysts, though rarely. Here we present a case of acquired, isolated third nerve palsy in a child secondary to compression by an arachnoid cyst, highlighting the importance of obtaining appropriate neuroimaging in children with ocular motility dysfunction and abnormal pupillary findings.

  Case report Top

A 19-month-old female child presented to us with complaints of the right eye appearing smaller for a month and squinting of right eye for the last 3 weeks. Birth history was not significant. There was no history of trauma. Neurodevelopmental examination was normal. Fixation pattern results showed that the right eye was central steady unmaintained, whereas the left eye was central steady maintained. The child followed light and toys uniocularly. Examination revealed mild ptosis of the right eye. Cover tests for near revealed right exotropia (approximately 45 pd) with ocular motility showing minimal limitation of elevation (−2) and adduction (−2) in the right eye. The anterior segment was normal except for anisocoria; the right pupil was mid-dilated and not reactive to direct/consensual light. The left pupil was normal [Figure 1]. Testing for pupillary reaction for near could not be done owing to poor cooperation by the child. There were no signs of aberrant innervation. Examination of the fundus by indirect ophthalmoscope showed that it was normal. In view of limited ocular movements and pupillary findings, the child was diagnosed with a nonpupil sparing right third nerve palsy.
Figure 1: Photograph showing anisocoria with right pupil larger than left

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Magnetic resonance imaging (MRI) of the brain and orbits was obtained to rule out a intracranial cause of the third nerve palsy. The MRI scan showed a 4 × 5 mm well circumscribed lesion immediately adjacent to the prepontinecisternal segment of the right oculomotor nerve [Figure 2]. The lesion was hyperintense on T2-weighted images, hypointense on T1-weighted images, and showed complete inversion on fluid-attenuated inversion recovery (FLAIR) sequences. These findings were highly suggestive of an arachnoid cyst. A neurosurgical opinion was obtained; the neurosurgeon recommended periodic follow-up with serial MRI and no immediate surgical intervention. The child was treated by patching the left eye for 2 h a day to prevent amblyopia, and follow-up was obtained on a monthly basis.
Figure 2: Axial slice from a T2-weighted MRI scan of the brain demonstrating a well-circumscribed, 4 × 5 mm cystic mass (arrow) in close apposition to the right oculomotor nerve. Given its well defined border and T2 hyperintensity, the mass was felt to be most consistent with an arachnoid cyst

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At 6 months, the child showed increasing right exotropia with hypotropia. No further changes were noted in the pupil. An MRI done at this time point showed that the arachnoid cyst was more poorly defined than before and likely smaller or at worst unchanged from the initial MRI [Figure 3]. However, there was evidence of subtle atrophy of the right oculomotor nerve relative to the left, possibly the result of longstanding compression or transmitted pulsations from the adjacent posterior communicating artery. Nevertheless, no neurosurgical intervention was recommended given the unchanged size of the cyst and the potential for substantial morbidity with a craniotomy. Consequently, a plan was made to treat the child with squint surgery which was pending at the time of submission of this paper.
Figure 3: Axial slices from a T2-weighted MRI scan of the brain, obtained 6 months after the scan shown in Figure 1. The arachnoid cyst (arrow) persists in proximity to the midcisternal segment of the right oculomotor nerve, but is now smaller in size and more irregularly shaped, consistent with spontaneous interval cyst shrinkage

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  Discussion Top

Isolated acquired third nerve palsy in a child, secondary to an arachnoid cyst is infrequently reported and the case we present here appears to be one of the few of its kind. Typically, isolated oculomotor palsy in children is congenital in etiology. When they occur, acquired palsy is most commonly due to trauma, followed by infection, inflammation, tumors, ophthalmoplegic migraine, and rarely aneurysms. Neoplasms account for approximately 14 to 18% of acquired palsies.[2]

Arachnoid cysts comprise approximately 1% of all intracranial masses and are thought to originate from maldevelopment of the leptomeninges in prenatal or early postnatal period. Their MRI signal characteristics are identical to those of cerebrospinal fluid. Although most are small and asymptomatic, symptoms arise because of local mass effect on adjacent structures, obstructive hydrocephalus, or as a consequence of space being occupied by the lesion.[3],[4]

Isolated third nerve palsy has been described in association with arachnoid cyst in the interpeduncular cistern,[5],[6] hemorrhage into suprasellar arachnoid cyst,[7] and the cavernous sinus.[8] There are only three reported cases of arachnoid cyst causing third nerve palsy in children. Ashker et al. described a case of arachnoid cyst in the right interpeduncular cistern which is presented as an internal ophthalmoplegia in a 8-month-old child. The progression occurred slowly over 19 months to compressive third nerve palsy, highlighting the slow progression in the arachnoid cyst. The case was initially thought to be viral ciliaryganglionopathy which is eventually presented with limited ocular movements suggestive of III nerve palsy.[6]

Werner et al. described a similar presentation as seen by Ashker et al. in a 10-month-old child which progressed in 6 weeks to compressive third nerve palsy. An MRI showed a cystic mass in the cisternal portion of the third nerve which proved to be a neurenteric cyst on excision.[9]

Hustler et al. reported unilateral mydriasis in a 16-month-old child. Acute oculomotor palsy developed 14 months later. An initial computerized tomography scan with contrast did not show any abnormality, but a subsequent MRI revealed an enlarging arachnoid cyst at the exit of the oculomotor nerve from the midbrain.[10]

In our patient, neurosurgical intervention was not advocated given the stable size of the cyst over time, the absence of any additional neurological signs and the potential morbidity of a craniotomy in a young child. Also unlike the reports mentioned above, our patient presented with pupillary and ocular motility findings at the outset, which might suggest greater intrinsic damage to the oculomotor nerve unlikely to improve in spite of surgery.

In summary, we present a rare case of arachnoid cyst presenting as acquired isolated third nerve palsy in a child. The case highlights the diagnostic value of neuroimaging when a patient presents with anisocoria, acquired squint, and the need to have a low threshold for performing neuroimaging in children with ocular motility and pupillary findings as in our patient.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Rengachary SS, Watanabe I. Ultrastructure and pathogenesis of intracranial arachnoid cysts. J Neuropathol Exp Neurol 1981;40:61-83.  Back to cited text no. 1
Kodsi SR, Younge BR. Acquired oculomotor, trochlear and abducent cranial nerve palsies in pediatric patients. Am J Ophthalmol 1992;114:568-74.  Back to cited text no. 2
Ide C, De Coene B, Gilliard C, Pollo C, Hoebeke M, Godfraind C et al. Hemorrhagic arachnoid cyst with third nerve paresis: CT and MR findings. AJNR Am J Neuroradiol 1997;18:1407-10.  Back to cited text no. 3
Callaway MP, Renowden SA, Lewis TT, Bradshaw J, Malcolm G, Coakham H. Middle cranial fossa arachnoid cysts: Not always a benign entity. Br J Radiol 1998;71:441-3.  Back to cited text no. 4
Lesser RL, Geehr RB, Higgins DD, Greenberg AD. Ocular motor paralysis and arachnoid cyst. Arch Ophthalmol 1980;98:1993-5.  Back to cited text no. 5
Ashker L, Weinstein JM, Dias M, Kanev P, Nguyen D, Bonsall DJ. Arachnoid cyst causing third cranial nerve palsy manifesting as isolated internal ophthalmoplegia and iris cholinergic supersensitivity. J Neuroophthalmol 2008;28:192-7.  Back to cited text no. 6
Miyamoto T, Ebisudani D, Kitamura K, Ohshima T, Horiguchi H, Nagahiro S. Surgical management of symptomatic intrasellar arachnoid cysts − Two case reports. Neurol Med Chir (Tokyo) 1999;39:941-5.  Back to cited text no. 7
Barr D, Kupersmith MJ, Pinto R, Turbin R. Arachnoid cyst of the cavernous sinus resulting in third nerve palsy. J Neuroophthalmol 1999;19:249-51.  Back to cited text no. 8
Werner M, Bhatti MT, Vaishnav H, Pincus DW, Eskin T, Yachnis AT. Isolated anisocoria from an endodermal cyst of the third cranial nerve mimicking an Adie’s tonic pupil. J Pediatr Ophthalmol Strabismus 2005;42:176-9.  Back to cited text no. 9
Hustler A, Joy H, Hodgkins P. Isolated unilateral mydriasis with delayed oculomotor nerve palsy secondary to intracranial arachnoid cyst. J AAPOS 2009;13:308-9.  Back to cited text no. 10


  [Figure 1], [Figure 2], [Figure 3]


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