Imaging and Differential. of the Large Eye1

Transcription

1 -. Imaging and Differential Diagnosis of the Large Eye1 Michelle Smith, MD Mauricio Castillo, MD The initial step in the differential diagnosis of an enlarged eye is to determine whether an intraocular mass is present. The globe may be expanded by a mass, seen mainly in children with retinoblastoma. Buphthalmos with or without neurofibromatosis also enlarges the eye. Dii- - fuse enlargement may be associated with a connective tissue disorder or be related to axial myopia. Focal enlargement represents staphyloma, which can be unilateral or bilateral. In the presence of one small eye, the normal-sized eye may be incorrectly diagnosed as large.. INTRODUCTION Eye enlargement is clinically manifested as proptosis and is usually seen in children. In children, the sclera is flexible and compliant, and an intraocular mass or increased intraocular pressure may easily cause the eye to enlarge. Imaging studies are needed to establish the presence or absence of a mass within the enlarged eye (Fig 1). Retinoblastoma is the most common intraocular tumor to produce generalized eye enlargement. Intraocular tumors in adults, however, do not usually produce eye enlargement. Enlargement can also occur without intraocular masses. The most common cause of such enlargement is axial myopia. Buphthalmos is usually associated with neurofibromatosis type 1 or can be secondary to childhood glaucoma. Abnormally increased compliance of the sclera associated with a connective tissue disorder may also lead to enlarged eye. Focal enlargement of the cornea or sclera is termed staphyloma. Staphyloma is usually idiopathic and can be unilateral or bilateral. Apparent enlargement of one eye can occur when the contralateral eye is relatively small. The characteristics of other struc- tunes such as facial bones, which may also be hypoplastic, should help distinguish this entity from true eye enlargement. This article discusses the differential diagnosis, imaging features, and diagnostic approach to the enlarged eye. index terms: Eye, CT, Eye, diseases, Eye. neoplasms RadloGraphlcs 1994; 14: I From the Department of Radiology, CB 7510, University of North Carolina School of Medicine, Manning Or, Chapel lull, NC Presented as a scientific exhibit at the 1993 RSNA scientific assembly. Received December : revision requested February 10, 1994 and received February 21: accepted March 11. Address reprint requests to MC. RSNA,

2 Figure 1. Algorithm for the diagnosis of the enlarged eye.. GENERALIZED EYE ENLARGEMENT WITH INTRAOCULAR MASSES Retinoblastoma is a rare, malignant, congenital tumor that arises from primitive photoreceptors in the retina. It is now included in the primitive neuroectodermal tumor group. Four types of retinoblastoma are recognized: nonheritable retinoblastoma; retinoblastoma inherited as an autosomal dominant trait; retinoblastoma associated with chromosomal anomalies, in particular, with chromosomes 1 3 and 14; and trilateral retinoblastoma (bilateral eye tumors plus pineal tumor) (1 ). Average age at diagnosis is 13 months, and almost all cases are diagnosed during childhood. Retinoblastoma occurs with equal frequency in male and female patients (1). Bilateral tumors are seen in 25%-33% of patients (2). Leukokoria (white pupillary reflex) is the most common clinical sign and is seen in as many as 60% of patients. Other clinical signs that may be present initially include strabismus, iris neovascularization, hyphema, secondary angle-closure glaucoma, and phthisis bulbi. Prognosis tends to be better if the tumor is contamed entirely within the globe; tumor extension beyond the globe is associated with 100% mortality. Computed tomography (CT) is an ideal imaging modality for the initial evaluation of suspected retinoblastoma (Fig 2) and shows calcification in more than 90% of tumors (1). The presence of calcifications in a mass is virtually pathognomonic for retinoblastoma (as opposed to other common entities with leukokoria but no calcifications, such as retrolental fibroplasia, persistent hyperplastic primary vitreous, and retinopathy of prematurity) and necessitates enucleation of the eyeball. Calcifications of retinoblastoma may have any shape or form. The noncalcified portion of the tumor is generally seen as a hyperattenuating mass, and retinal detachments with subretinal effusions may be present. The eye may be enlarged but is almost always normal in size. The presence of a small eye generally rules out retinoblastoma. Retinoblastomas are seen as areas of mild hyperintensity to normal signal intensity on Tl-weighted magnetic resonance (MR) images and hypointensity on T2-weighted images (1). Effusions are hyperintense compared with the tumor on T2- weighted images. 722 U Scientific Exhibit Volume 14 Number 4

3 Figure 2. (a) Axial contrast material-enhanced CT scan shows a calcified retinoblastoma (r) confined to the left globe. Despite slight tilting to the right, there is enlargement of the involved globe. The optic nerve is stretched but not involved by tumor. (b) Axial CT scan obatained 3 mm cephalad to that in a shows thickening of the sclera (arrowheads) suggestive of invasion by tumor. The vitreous is hyperattenuating compared with that of the normal eye. The lens (open arrow) is medially displaced by the mass. mors include melanoma and metastases. Although such lesions could conceivably cause enlargement of the eye, the mature and hard sclera in adults usually does not permit the eye to enlarge. U GENERAUZED ENLARGEMENT WITH NO INTRAOCULAR MASSES Figure 3. Axial CT scan of a patient with axial myopia who had bilateral proptosis. Note elongation of the globes in their anteroposterior diameter. The sclerae are thinned posteriorly. The second most important goal of any imaging method is to detect tumor spread. CT, but preferably contrast material-enhanced MR imaging, may be used to detect any tumor spread along the optic nerves and pathways. Ectopic tumors may be seen in the parasellar or pineal regions. In adults, the most common intraocular tu-. Axial Myopia Axial myopia is an idiopathic enlargement of the eyeball in the anteroposterior dimension that causes convergence of light anterior to the retina. Axial myopia is the most common cause of macrophthalmia (3). It commonly is associated with proptosis and may be unilateral or bilateral. The process is chronic with no associated pain. Amblyopia (impairment of vision without organic cause) is usually present. Axial myopia may also be seen with orbital infections, Grave disease, and staphyloma (3). At CT imaging, no intraocular masses are found and the globes are enlarged, generally in the anteroposterior axis (Fig 3). Therefore, in axial myopia the globe is oval. In addition to ocular elongation, CT or MR images may show thinning of the sclera. July 1994 Smith and Castillo U RadioGraphics U 723

4 Figure 4. (a) Axial plain CT scan obtained in a child with neurofibroniatosis type 1 shows an enlarged and proptotic right eye (r) compared with the left eye (1). (b) Axial CT scan of an adolescent with a long history of glaucoma shows an enlarged left eye (L). The underlying cause of the shrunken and calcified right eye (phthisis bulbi) is not certain. (Courtesy of P. Van Tassel, MD, Medical University of South Carolina, Charleston.) (C) Axial enhanced CT image of a patient with neurofibromatosis type 1 shows left-sided buphthalmos (1). There is hypoplasia of the left greater wing of the sphenoid (arrows) and abnormal soft tissues (arrowheads) in the superior orbital fissure su estive of the presnt.urofihrom L IT -I -- p. It 1 C.. Buphthalmos Diffuse enlargement of the eye in children seeondary to increased intraocular pressure is termed buphthalmos (from the Greek bous, ox, plus ophthalnus, eye); other terms for this entity include hydrophthalmos and megophthalmos. This diffuse enlargement of the globe is almost uniquely seen during childhood, when the sclera is soft and deformable. It generally occurs secondary to congenital or infantile glaucoma. Buphthalmos is also seen in patients with neurofibromatosis type 1 in whom the canal of Schlemm is obstructed by membranes or masses composed of aberrant mesodern ial tissue (4) (Fig 4a). Normally, the canal of Schlemm is responsible for resorption of the aqueous humor (anterior chamber fluid) and is located between the cornea and the iris. Other diseases that may cause buphthalmos are Sturge-Weber syndrome, Lowe (cerebrohepatorenal) syndrome, ocular mesodermal dysplasias such as Axenfeld or Rieger anomalies, homocystinuria, aniridia (4), and, rarely, ac- 724 U Scientific Exhibit Volume 14 Number 4

5 Figure 5. (a) Axial CT scan obtained through the equator of the eyes of a patient with Marfan syndrome. The sclerae are thinned and have a wavy contour. (b) Axial CT scan obtained 3 mm cephalad to that in a shows superomedial dislocation of both lenses (*). The corneas (arrowheads) are thickened and enlarged, compatible with megalocorneas. quired glaucoma (Fig 4b). The goal of surgery is usually to lower intraocular pressure by increasing aqueous humor transport and consists of a goniotomy to increase the angle of the anterior chamber or trabeculotomy to lyse adhesions. In cases of buphthalmos associated with neurofibromatosis, CT and MR images may demonstrate other anomalies such as dysplasias of the greater sphenoidal wing, neurofibromas in the cavernous sinuses or the superior orbital fissures, optic pathway glioma, and proptosis (Fig 4c). In all cases of buphthalmos, regardless of associated anomalies, imaging studies show a uniformly enlarged globe with no intraocular masses. Although the enlarged globe is usually round, it may be oval or have a bizarre configuration. #{149} Connective Tissue Disorders Macrophthalmia may be seen in association with Marfan syndrome, Ehier-Danlos syndrome, Weill-Marchesani syndrome (congenital mesodermal dysmorphodystrophy), and homocystinunia (5). Enlargement of the globe is found in patients affected by these disorders early in childhood when the sclera is immature and compliant. At imaging, the contour of the globe can be described as floppy (Fig 5a). In patients with Marfan syndrome, the triad of arachnodactyly, cardiovascular disease, and ectopia lentis is present. The dislocation of the lenses tends to occur superiorly and outward in patients with Marfan syndrome (5) (Fig Sb). Patients with homocystinuria also have lens dislocation, but it is usually inferior and inward (5). Subluxation of the lens (in both disorders) is thought to be secondary to poor zonular attachments and is often associated with lenticular colobomas. In these collagen vascular disorders, macrophthalmia and ectopia lentis are usually bilateral. Patients with Marfan syndrome may also have hypoplasia of the iris and ciliary bodies, myopia, ptosis, megalocorneas, blue scleras, and glaucoma (5). July 1994 Smith and Castillo U RadioGraphics U 725

6 #{149} Proteus Syndrome This very rare anomaly (named after the Greek sea god Proteus [the polymorphous ], who could change his appearance at will) is characterized by hamartomatous changes involving mesodermal and ectodermal tissues throughout the body. Clinical fmdings include macrocrania, and the skull has multiple protuberances due to exostoses and hyperostoses (6). The limbs are asymmetric, and there may be skin changes (eg, nevi, pigmented lesions, hyperkeratoses, lipomas). Clinically, this disorder should be differentiated from the more common neurofibromatosis type 1. Orbital abnormalities include large eye, strabismus, myopia, anisocoria, microphthalmos, cataracts, retinal detachment, chorioretinitis, nystagmus, and heterochromia of the irises (6) (Fig 6). U FOCAL ENLARGEMENT #{149} Staphyloma Staphylomas may be isolated or related to axial myopia (7). When related to axial myopia, the prevalence of staphylomas increases with the size of the globe. Staphylomas associated with axial myopia generally occur on the temporal side of the optic disk but may also be seen anteriorly or along the equator of the eye (8) (Fig 7a). Staphylomas have a high (77%) risk for advanced chorioretinal degeneration that is generally due to atrophy of the choroid and retina, choroid retraction from the optic disk, and posterior vitreous detachments (7). These changes lead to increased prevalence of choroidal hemorrhage and retinal detachment, which are associated with a grave prognosis for vision. Cataracts and secondary glaucoma may also be seen. In one series (9), 139 (34.5%) of 403 eyes with posterior staphylomas were blind. In the majority of cases, there is no effective treatment. Other conditions in which staphyloma may be seen include glaucoma, trauma, scleritis, and necrotizing infections. Imaging studies usually show a focal bulge and thinning of the sclera. Staphylomas can be unilateral or bilateral (Fig 7b). #{149} APPARENT ENLARGEMENT In the presence of a contralateral small eye (microphthalmia), a normal-sized globe may be Figure 6. Axial fast spin-echo T2-weighted image (3,500/93 [repetition time msec/echo time msecj, one excitation) of a patient with Proteus syndrome. A right-sided staphyloma (arrowheads) is present. The right eye (r) is enlarged, whereas the left eye (1) is small. Note bilateral retro-ocular cysts (). Zones of bone dysplasia (*) are present. misinterpreted as enlarged. Isolated microphthalmia is generally housed in a small bony orbit and may be due to posterior colobomas, persistent hyperplastic primary vitreous, retrolental fibroplasia, retinal folds, Lowe syndrome, and radiation therapy, infections, or trauma during early childhood. Cryptophthalmia refers to severe microphthalmia. In complete absence of the globe (anophthalmia), the bony orbit is also absent. Hemifacial microsomia may also include an ipsilateral small eye (Fig 8). U SUMMARY In children, CT is the diagnostic method of choice for evaluation of the large eye. CT allows identification of intraocular calcifications, which are highly suggestive of retinoblastoma. If the eye is diffusely enlarged and there are no intraocular masses, clinical correlation is imperative because buphthalmos can be seen with phakomatosis and other systemic disorders. In the absence of systemic disorders, correlation with intraocular pressure is necessary because congenital and infantile glaucoma may also result in eye enlargement. 726 U Scientific Exhibit Volume 14 Number 4

7 Figure 7. (a) Axial T2-weighted image (2,500/80; two signals averaged) shows an incidentally f ound staphyloma (arrowheads) in the posterior temporal aspect of the right globe. (b) Axial Ti-weighted image (5(X)/iS, four signals averaged) of a patient with glaucoma who was examined because of headaches. A right posterotemporal staphyloma (arrowheads) is present. Figure 8. (a) Axial CT scan of a patient with Goldenhar syndrome (oculo-auriculo-vertebral dysplasia) and left facial nhicrosomia. Although the right eye appears enlarged. it is actually of normal size. Note left-sided microphthalmia. (b) Frontal view from the three-dimensional reformation shows left hemifacia that includes the orbit. (C) Lateral view from the three-diniensional reformation also shows a small left orbit, absent external auditory canal, and left hypoplastic mandible. a. July 1994 Smith and Castillo U RadioGraphics U 727

8 In the adult, diffuse eye enlargement is generally a manifestation of a systemic disorder. Because intraocular masses do not generally cause eye enlargement in adults, either CT or MR imaging may be performed. Focal eye enlargements (staphyloma) initially imaged with CT or MR imaging are local abnormalities and do not require any additional imaging. Diffuse eye enlargement, however, may be associated with systemic illnesses such as connective tissue disorders, and clinical correlation is important. Finally, in selected cases, imaging should include not only the eyes but the entire face to detect hemifacial microsomia, which could lead to the erroneous impression of a contralateral enlarged eye. U REFERENCES 1. Mafee MF, Goldberg MF, Greenwald MJ, et al. Retinoblastoma and simulating lesions: role of CT and MR imaging. Radiol Clin North Am 1987; 25: Hopper KD, Sherman JL, Boal DK, Eggli K!). CT and MR imaging of the pediatric orbit. RadioGraphics 1992; 12: Brodey PA, Randel S, Lane B, Fisch AE. Cornputed tomography of axial myopia. J Comput Assist Tomogr 1983; 7: Castillo M, Quencer RM, GlaserJ, Altman N. Congenital glaucoma and buphthalmos in a child with neurofibromatosis. j Clin Neuroophthalmol 1988; 8: , Char DH, Unsold R, Sobel DF, Salvolini U, Newton TH. Ocular and orbital pathology. In: Newton TH, Hasso AN, Dillon WP, eds. Computed tomography of the head and neck. New York, NY: Raven, 1988; Taybi H, Lachman RS. Proteus syndrome. In: Radiolog of syndromes, metabolic disorders, and skeletal dysplasias. 3rd ed. St Louis, Mo: Mosby, 1990; Swayne LC, Garfinkle WB, Bennett RH. CT of posterior ocular staphyloma in axial myopia. Neuroradiology 1984; 26: Anderson RL, Epstein GA, Dauer EA. Computed tomographic diagnosis of posterior ocular staphyloma. AJNR 1983; 4: Curtin BJ. The posterior staphyloma of pathologic myopia. Trans Am Ophthalmol Soc 1977; 75: U Scientific Exhibit Volume 14 Number 4