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Neuroradiology Case of the Week

Case 227

Devang Butani, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: An 86-year-old patient with mental status changes and left ptosis of unknown duration.

Imaging Findings: A large, 1.5 cm out-pouching in the posterior aspect of the globe, with MR signal that is iso-intense to the vitreous humor on all sequences.  No orbital fractures are seen.  CT findings are similar, with attenuation similar to the vitreous humor.

Diagnosis: Coloboma

Discussion: Coloboma is a gap or a defect of ocular tissue due to failure of fusion of the superior aspect of embryonic fissure, that may involve any or all structures of embryonic cleft, and are often bilateral. The most suggestive radiological clue is a focal defect in the posterior globe with out pouching of relatively homogenous vitreous. Crater or funnel shaped excavation, oriented posteriorly may also be seen. However, if there is concurrent retinal detachment, varying amounts of hemorrhage may give heterogeneous GRE and T2 appearance. Associated findings include optic tract and chiasm atrophy and micropthalmia. CT findings include isointensity to vitreous humor in a retroglobal defect.

Complications include retinal detachment in 25-40% of patients.

Differential diagnoses:

• Trauma with globe rupture.
• Morning glory disc anomaly.
• Peripapillary staphyloma.
• Bupthalmos (ox eye).
• Micropthalmic cyst.

References:

1. Hansberger et al. Diagnostic Imaging:  Head and Neck.  Amirsys.  pp II-1-6-9
2. Bashour M. Eyelid coloboma. http://www.emedicine.com/oph/topic673.htm, May 13, 2005