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Neuroradiology Case of the Week

Case 274

Ashwani K. Sharma, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a seven-month-old child with known bilateral coloboma of eye who was scanned to rule out brain parenchymal abnormalities.

Imaging Findings: Imaging findings of coloboma relate to the extent of the defect. The globe is misshapen, and there is widening of the optic nerve head, which is of water density and is continuous with the vitreous humor. Thinning and eversion of the sclera at the margin of the defect may be identified. Associated anomalies, including microphthalmos, may be present. Imaging of the brain may demonstrate further associations, including basilar encephalocele and agenesis of the corpus callosum.

Diagnosis: Bilateral colobomas

Discussion: Coloboma (from the Greek koloboun, to mutilate) is defined as an absence or defect of some ocular tissue, usually resulting from malclosure of the fetal intraocular fissure [1] and was first described by Walther in 1821. Coloboma may involve the optic nerve, retina, choroids, iris, or lens and may be complete, when all of these structures are involved, or incomplete, when a variable part of the eye is spared [2].
     Colobomas are fairly common, often bilateral, and are usually mild, as a result, imaging studies of most patients with colobomas are normal [3]. Of special importance is the association of disk malformations, especially the morning glory disk anomaly, and congenital forebrain anomalies like basal encephalocoeles, or herniations of brain tissue and corpus callosum abnormalities.
     Morning glory syndrome was first described in 1970 in ten unrelated children with an unusual congenital disk anomaly [3]. The morning glory anomaly appears as a large, excavated, funnel-shaped disk with a prominent elevated rim or ring of peripapillary tissue sometimes associated with peripapillary pigmentary mottling [4]. The emerging vessels characteristically form a radiating pattern as they fan out from the disk, giving the appearance of a flower—hence, the name morning glory [5].

References:

1. Taylor E J, ed. Dorland’s illustrated medical dictionary. 27th ed. Philadelphia, Pa: Saunders, 1988, 359.
2. Duke-Elder S. System of ophthalmology, Vol 3, pt 2. St Louis, Mo: Mosby, 1963; 456-487.
3. P. Kindler, Morning glory syndrome: unusual congenital optic disk anomaly. Am J Ophthalmol. 1970 Mar;69(3):376-84. [Medline]
4. Martyn LJ, DiGeorge A. Selected eye defects of special importance in pediatrics. Pediatr Clin North Am. 1987 Dec;34(6):1517-42. [Medline]
5. Okada K, Sakata H, Shirane M, Minamoto A, Choshi K. Computerized tomography of two patients with morning glory syndrome. Hiroshima J Med Sci. 1994 Sep;43(3):111-3. [Medline]