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Neuroradiology Case of the Week

Case 386

February 2009

Balasubramanya Kolar, MD and P-L Westesson, MD, PhD, DDS

Clinical Presentation: An 8-year-old male with abnormal optic nerve on examination.

Imaging Findings: Deformity of the globe with thinning of sclera noted posteriorly. Bulging of sclera also noted in a posteromedial direction. However, there was no break in the scleral lining. The optic nerves bilaterally were normal. There were no mass lesions within the orbits.

Diagnosis: Posterior staphyloma

Discussion: Posterior staphyloma is usually a degenerative change associated with progressive elongation of the globe, particularly in the posterior segment of highly myopic eyes. Posterior staphyloma occurs in the presence of pathological myopia [1]. Though a third of cases present at birth, the majority of changes occur through puberty and adulthood. The posterior staphyloma presents as an extreme posterior ectasia of the posterior retina involving the optic disc. Extreme retinal thinning with increased visibility of the underlying choroid is noted [2]. Increased scleral elasticity in highly myopic eyes is believed to lead to the abnormal elongation of the eye. The optic nerve may be normal in appearance or may be vertically oval.
     Axial myopias can be distinguished from staphylomas by a lack of a focal bulge. In addition, staphylomas are lined with choroidal tissue [3].
     An important feature is the tendency for these to expand and deepen with age. It is unusual to encounter sharp edged staphyloma in the youngest age group [1].
     The presence of posterior staphylomas early in life would indicate the essentially congenital nature of this lesion. One of the many types of staphylomas described by Curtin, the type V is thought to be related to a defective closure of the fetal fissure. It is probable that defective posterior scleral development and an abnormal collagen restructuring with growth are both factors in the evolution of these lesions [1].
      The age of the patient in our report was also very young and this could be a congenital variant with above features.

References:

1. Curtin BJ. The posterior staphyloma of pathologic myopia. Trans Am Ophthalmol Soc 1977; 75: 67-86. [PubMed]
2. Bowen TA, Perlman JI, Gieser R. A transparent peripapillary staphyloma in pathologic myopia. Retina 2001; 21(4):373-375. [PubMed]
3. Mafee MF, Atlas SW, Galetta SL. Eye, orbit and visual system. In: Atlas SW, ed. Magnetic Resonance Imaging of the Brain and Spine, 3rd edition. Philadelphia: Lippincott, Williams and Wilkins, 2002:1433-1524.