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Ophthalmology and Visual Sciences

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Bilateral Cranial Nerve VI Palsies Secondary to Arachnoid Cyst

Photographer: N/A
Contributor: Brittni A. Scruggs, MD, PhD

September 18, 2017

A 4-year-old boy was admitted for failure to thrive, worsening anorexia, and vomiting. Ophthalmology was consulted for evaluation of abnormal eye alignment. Medical history was significant for a 10q26 deletion, which involves the ARMS2 gene, in addition to hypotonia and developmental delay. Examination was significant for bilateral 6th nerve palsies with bilateral grade I disc edema.

Magnetic resonance imaging (MRI) showed left-sided polymicrogyria and a large cystic lesion in the left temporal lobe (Figures 1-4) that appeared bright on T2-weighted imaging (Figure 1), was suppressed completely on FLAIR sequence (Figure 2), and had no post-contrast enhancement (Figure 3). These findings were consistent with an arachnoid cyst. Additionally, there was a 6 mm right midline shift with posterior globe flattening, protrusion of the optic nerve heads bilaterally, and mild prominence of the subarachnoid space of the bilateral optic nerves (Figure 4), consistent with increased intracranial pressure (ICP).

Arachnoid cysts, if large, can lead to displacement of neurovascular structures and increased ICP. Review of literature suggests that arachnoid cysts may be a rare cause of acquired sixth nerve palsy and strabismus in children (1). Neurosurgical shunting followed by strabismus surgery relieved the abduction deficit and esotropia in several case reports (2). This patient underwent a left cystoperitoneal shunt with improvement in his systemic symptoms. At his one month follow up appointment, he had normal ocular motility and alignment and his papilledema had resolved.

Figure 1. Coronal T2-weighted MRI with contrast showing a large, bright cystic lesion. There is effacement of the left ventricle with dilation of the right ventricle.

Figure 1. Coronal T2-weighted MRI with contrast showing a large, bright cystic lesion. There is effacement of the left ventricle with dilation of the right ventricle.

Figure 2. Axial FLAIR MRI showing suppression of the cyst.

Figure 2. Axial FLAIR MRI showing suppression of the cyst.

Figure 3. Axial T1-weighted post-contrast MRI showing no enhancement of the lesion.

Figure 3. Axial T1-weighted post-contrast MRI showing no enhancement of the lesion.

Figure 4. Axial 3D SPACE T2-weighted MRI showing bilateral optic nerve swelling, distension of the optic nerve sheath, and flattening of the globes.

Figure 4. Axial 3D SPACE T2-weighted MRI showing bilateral optic nerve swelling, distension of the optic nerve sheath, and flattening of the globes.

REFERENCE(S)

  1. J Pediatr Ophthalmol Strabismus. 2014; 51:e58–e61.
  2. J Pediatr Ophthalmol Strabismus. 2007 Jan-Feb; 44(1):53-4.

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last updated: 09/18/2017