Imaging of Pediatric Orbital Diseases




This article reviews a variety of congenital and developmental disorders of the pediatric orbit with particular emphasis on ocular lesions, followed by a description of developmental and neoplastic orbital and ocular masses. The relationship of these diseases to various syndromes and/or known genetic mutations is also highlighted.


Key points








  • Orbital diseases in children differ from those found in adults in terms of histopathologic and imaging characteristics.



  • Clinical signs are often nonspecific, and imaging is a critical step in evaluating the pediatric orbit, optic pathway, and cranial nerves that supply the orbital contents.



  • High-resolution 3-T MR imaging helps characterize orbital and ocular soft-tissue lesions, permitting superior delineation of orbital soft tissues, cranial nerves, blood vessels, and blood flow and detection of intracranial extension of orbital disease.



  • Computed tomography (CT) is reserved primarily for evaluation of orbital bony architecture.






Introduction


The wide spectrum of orbital disease seen in children differs substantially from that found in adults in terms of histopathologic and imaging features. Clinical symptoms and signs such as proptosis, strabismus, diplopia, and optic disc edema are nonspecific, and diagnostic imaging studies play an essential role in depicting the nature and extent of orbital abnormalities, often providing a definitive diagnosis or a relevant differential diagnosis. The information provided by imaging is also important in determining optimal medical or surgical treatment and assessing response to treatment. In this article, the salient clinical and imaging features of various pediatric orbital lesions are described, and the differential diagnoses are reviewed.




Introduction


The wide spectrum of orbital disease seen in children differs substantially from that found in adults in terms of histopathologic and imaging features. Clinical symptoms and signs such as proptosis, strabismus, diplopia, and optic disc edema are nonspecific, and diagnostic imaging studies play an essential role in depicting the nature and extent of orbital abnormalities, often providing a definitive diagnosis or a relevant differential diagnosis. The information provided by imaging is also important in determining optimal medical or surgical treatment and assessing response to treatment. In this article, the salient clinical and imaging features of various pediatric orbital lesions are described, and the differential diagnoses are reviewed.




Normal anatomy


The orbital contents are contained within a bony pyramid. The orbital roof is formed by the orbital plate of the frontal bone. The lateral wall is formed by the orbital surface of the zygomatic bone and greater wing of the sphenoid. The frontal process of the maxillary bone, the lacrimal bone, lamina papyracea of the ethmoid bone, and the lesser wing of the sphenoid make up the medial wall from anterior to posterior. The orbital floor is formed by the orbital surfaces of the zygomatic, maxillary, and palatine bones. The optic foramen forms the apex of the bony pyramid and is formed by the lesser wing of the sphenoid. The superior orbital fissure is limited by the lesser wing of the sphenoid superomedially and the greater wing of the sphenoid inferolaterally. The inferior orbital fissure lies between the orbital floor and the greater wing of the sphenoid. The optic canal and superior and inferior orbital fissures transmit nerves and vessels ( Table 1 ); spread of tumor along these conduits can occur from the orbit to extraorbital compartments including intracranial extension.



Table 1

Contents of orbital foramina
















Foramen Contents
Superior orbital fissure Cranial nerves III, IV, V 1, VI
Superior ophthalmic vein
Orbital branch of middle meningeal artery
Inferior orbital fissure Cranial nerve V 2
Infraorbital vein
Infraorbital artery
Optic canal Cranial nerve II
Ophthalmic artery


The orbital contents are divided into the intraocular compartment or globe, the muscle cone, and the intraconal and extraconal spaces ( Fig. 1 A). The extraocular muscles include the superior, inferior, medial, and lateral rectus muscles and the superior and inferior obliques; all but the inferior oblique muscles constitute the muscle cone (see Fig. 1 B). The levator palpebrae superioris lies superior to the superior oblique muscle. The extraocular muscles converge at the orbital apex to form a fibrous connective tissue ring known as the annulus of Zinn. The nonocular compartment of the eye is divided by the muscle cone into conal (muscle cone and annulus of Zinn), intraconal, and extraconal spaces. The intraconal space contains fat, the ciliary ganglion, the ophthalmic artery and vein, and branches of the ophthalmic nerve. The ophthalmic artery and vein and cranial nerves enter the intraconal space through the annulus of Zinn. The extraconal space contains fat, the lacrimal gland, and cranial nerves (branches of the ophthalmic and trochlear nerves). The superior oblique muscles receive motor supply from the trochlear nerves (cranial nerve IV). The lateral rectus muscles are innervated by the abducens nerves (cranial nerve VI), and the oculomotor nerves (cranial nerve III) supply motor function to the remaining extraocular muscles.




Fig. 1


Normal orbital anatomy. ( A ) High-resolution T1-weighted MR image shows the orbit divided into intraconal and extraconal spaces by the muscle cone and their relationships to the globe. ( B ) Coronal high-resolution T1-weighted MR image of the orbit shows the configuration of the extraocular muscles and the optic nerve. ( C ) High-resolution axial T1-weighted MR image and ( D ) axial T2 sampling perfection with application optimized contrasts using different flip angle evolution (SPACE) MR image showing ocular anatomy. The sclera is hypointense and continuous anteriorly with the cornea and posteriorly with dura. Normal choroid and retina are not distinguishable from each other and appear as an intermediate-intensity structure deep to the sclera on the T1-weighted image. The choroid is continuous anteriorly with the iris and ciliary body, and together, these structures make up the uvea. The lens appears hypointense on the T2-weighted image. Anterior to the lens is a faintly visible linear hypointensity, which is the iris. The iris separates the anterior segment into anterior and posterior chambers containing aqueous humor. The posterior segment lies posterior to the lens and contains the gelatinous vitreous. CN II, cranial nerve II (optic nerve); IRM, inferior rectus muscle; LRM, lateral rectus muscle; MRM, medial rectus muscle; SOM, superior oblique muscle; SRM, superior rectus muscle.


The globe consists of 3 distinct layers from the outside to inside: sclera, uvea, and retina (see Fig. 1 C, D). The choroid and retina are inseparable on routine cross-sectional imaging but can be differentiated in the presence of choroidal or retinal detachments. The uvea consists of the iris, ciliary body, and choroid (the most vascular structure of the globe). The retina continues posteriorly as the optic nerve. The collagenous sclera is continuous anteriorly with the cornea and posteriorly with the dura and appears hypointense on T1-weighted MR images at 3T (see Fig. 1 C).




Imaging technique


Imaging of the orbit is primarily accomplished by ultrasonography (US) (evaluation of the globe), CT (bony anatomy), and MR imaging (soft-tissue characterization). CT is indicated for the bony assessment in craniofacial anomalies, trauma, orbital complications of acute sinusitis (with contrast), and assessment of bony remodeling or destruction from orbital masses. Helical 2.5- to 3-mm axial images are obtained with multiplanar soft-tissue and submillimeter bone reformats. CT angiography (CTA) may be obtained for diagnosis or follow-up of suspected orbital arteriovenous malformation (AVM) or arteriovenous fistula (AVF). The parameters for CT should use the lowest dose possible while still providing diagnostic quality images.


Orbital MR imaging is optimally achieved at 3T using a 32-channel phased-array head coil or equivalent coil when possible. In some instances specialized orbital surface coils may be used. Imaging protocols depend on clinical indications. For example, suspected tumors are imaged with high-resolution, thin-section (<3 mm) axial and coronal fat-suppressed T2; axial non-echo planar diffusion-weighted imaging (DWI); axial T1 and multiplanar high-resolution, fat-suppressed, gadolinium-enhanced T1-weighted images. MR venography (MRV) and/or MR angiography (MRA) are sometimes indicated for vascular assessment. Heavily T2-weighted 3-dimensional sequences with submillimeter-thick images (eg, sampling perfection with application optimized contrasts using different flip angle evolution [SPACE], constructive interference in steady state [CISS], fast imaging employing steady state acquisition [FIESTA], sensitivity encoding [SENSE]) are of use for ocular assessment, especially for intraocular tumors such as retinoblastoma and for assessment of cranial nerves. Congenital strabismus and eye movement disorders generally require a combination of thin-section high-resolution axial and coronal T1-weighted images for assessment of the size, shape, and position of the extraocular muscles and imaging of the brain and relevant cranial nerves.


Conventional catheter angiography is reserved for the delineation of orbital AVM or AVF and sometimes for endovascular treatment.




Congenital and developmental anomalies


Anophthalmos and Microphthalmos


Anophthalmos or anophthalmia refers to congenital absence of the eyes. Anophthalmos and microphthalmos are a significant cause of congenital blindness and can be isolated or syndromic. Several genetic mutations involving PAX6, SOX2 , and RAX genes are associated with these conditions.


Primary anophthalmos is bilateral in approximately 75% of cases and occurs because of failure of optic vesicle development at approximately 22 to 27 days of gestation. Secondary anophthalmos is lethal and occurs when the entire anterior neural tube fails to develop. Degenerative or consecutive anophthalmos occurs when the optic vesicles form but subsequently degenerate; consequently neuroectodermal elements may be present in degenerative anophthalmos but are absent in primary and secondary anophthalmos.


Microphthalmos refers to a small ocular globe with an ocular total axial length (TAL) 2 standard deviations less than that of the population age-adjusted mean. Microphthalmos is further classified as severe (TAL <10 mm at birth or <12 mm after 1 year of age), simple, or complex depending on the anatomic appearance of the globe and the degree of TAL reduction. Simple microphthalmos refers to an intact globe with mildly decreased TAL. Complex microphthalmos refers to a globe with anterior segment dysgenesis (developmental abnormalities of the globe anterior to the lens) and/or posterior segment dysgenesis (developmental abnormalities of the globe posterior to the lens) with mild, moderate, or severe decrease in TAL. Severe microphthalmos may be difficult to differentiate from anophthalmia. Both severe microphthalmos and degenerative anophthalmos contain neuroectodermal tissues and are considered as entities along a continuum. The diagnosis is usually based on clinical and imaging criteria.


US is used to determine the ocular TAL in microphthalmos. CT and MR imaging demonstrate an absent globe in anophthalmos ( Fig. 2 ). Amorphous tissue with intermediate density on CT, intermediate signal on T1-weighted images, and low signal on T2-weighted MR images may be noted particularly in degenerative anophthalmos. Orbital dimensions and volumes are reduced in anophthalmos and usually in microphthalmos, unless associated with an intraorbital cyst ( Figs. 3 and 4 ). Simple microphthalmos demonstrates a normal albeit small globe, with normal signal characteristics.




Fig. 2


Unilateral anophthalmos. A 5-day-old baby girl with unilateral right-sided anophthalmos. ( A ) Axial and ( B ) coronal T2-weighted images demonstrate complete absence of the right globe. Note the presence of amorphous tissue and structures resembling extraocular muscles within the anophthalmic right orbit. The right optic nerve is absent.



Fig. 3


Severe microphthalmos. Fetus with craniofacial anomalies. ( A ) Fetal MR image at 34 weeks reveals apparent right anophthalmos and left microphthalmos. The fetal nose is absent. ( B ) Postnatal 3-dimensional (3D) CT surface reconstruction image at 3 days of age demonstrates arrhinia and bilateral cryptophthalmos. ( C ) 3D CT image of the skull shows shallow malformed orbits and absence of the nares. ( D ) Axial T2-weighted MR image shows a rudimentary cystic structure within the right orbit ( arrow ), which in retrospect can be seen on the fetal MR image, and left microphthalmos. The infant was diagnosed with Bosma syndrome.



Fig. 4


Unilateral microphthalmos and cyst. A 2-month-old baby girl with persistent closure of the right eye. Clinical examination revealed right microcornea and microphthalmos with bluish discoloration of the lower eyelid thought to represent a cyst. ( A , B ) Axial fat-suppressed T2-weighted MR images confirm microphthalmos associated with a cyst. The globe is small, deformed, and displaced superiorly. The large cyst ( asterisk ) is located posterosuperior to the globe.


Mild to moderate microphthalmia is managed conservatively with conformers, whereas severe microphthalmia and anophthalmia are treated with endo-orbital volume replacements (implants, expanders, and dermis-fat grafts) and soft-tissue reconstruction.


Cryptophthalmos


Embryologically, the eyelid folds appear during the seventh week and grow toward each other and fuse, with separation of lids occurring between the fifth and seventh months of development. Cryptophthalmos is usually syndromic and results from failure of development of the eyelid folds with absence of eyebrows, eyelids, and the cornea and continuous skin extending from the forehead to the cheeks. Imaging is required to demonstrate the status of the underlying ocular globes and orbital structures before surgical intervention (see Fig. 3 ).


Anterior Segment Dysgenesis


Anterior segment dysgenesis results from faulty development of the anterior ocular structures, including the cornea, iris, ciliary body, lens, and anterior and posterior chambers, resulting in an increased risk of glaucoma and blindness. Anterior segment anomalies are associated with PITX2, FOXC1 PAX6 and related mutations and produce findings such as aniridia, iris hypoplasia, primary congenital glaucoma, Axenfeld-Rieger syndrome (congenital angle anomalies with iris strands), and Peter anomaly (corneal clouding with adhesions between iris, lens, and cornea). Although many of these anomalies produce ophthalmologic abnormalities that do not require further imaging, thin-section high-resolution T2-weighted 3T MR images may demonstrate abnormal size and shape of the anterior and posterior chambers and/or buphthalmos ( Fig. 5 ).




Fig. 5


Anterior segment dysgenesis. ( A ) A 1-day-old baby girl with right proptosis, elevated intraocular pressure, and scleralization with calcification on the anterior surface of the right eye. ( B ) Axial fat-suppressed T2-weighted MR image shows mild right microphthalmos with a large, irregular anterior segment consistent with the clinical finding of anterior segment dysgenesis. There is aniridia and aphakia. Progressive enlargement and exposure of the right eye occurred despite medical therapy. Subsequently, with no potential for visual rehabilitation and risk for perforation, the right eye was enucleated.

([ A ] Courtesy of Carolyn Wu, MD, Department of Ophthalmology, Boston Children’s Hospital, Boston, MA.)


Macrophthalmos


Elongation of the anteroposterior (AP) diameter of the posterior chamber of the globe is most frequently caused by severe myopia. Buphthalmos refers to diffuse enlargement of the AP diameter of the globe (anterior and posterior chambers) usually due to primary congenital or infantile glaucoma or due to syndromic glaucoma as seen in neurofibromatosis type I (NF-1) and Sturge-Weber syndrome.


Imaging is required to differentiate macrophthalmos from other conditions resulting in enlargement of the globe such as an intraocular mass. In buphthalmos, the globe is generally uniformly enlarged but may occasionally have oval or bizarre configurations. Patients with NF-1 demonstrate proptosis, sphenoid wing dysplasia, and orbital plexiform neurofibromas in addition to buphthalmos ( Fig. 6 ).




Fig. 6


Macrophthalmia. A 5-month-old girl with NF-1 and proptosis. Axial fat-suppressed T2-weighted MR image reveals enlargement of the right globe, consistent with buphthalmos. There is right sphenoid bone dysplasia with associated enlargement of the right middle cranial fossa. A plexiform neurofibroma is present within the lateral aspect of the orbit ( long arrow ). There is also a nerve sheath tumor within the right cavernous sinus ( short arrow ) and Meckel cave.


Congenital Cystic Eye


Congenital cystic eye is a rare condition resulting from failure of the optic vesicle to invaginate to form the globe. On imaging, a cystic, sometimes septated, orbital mass is seen in place of the normal globe ( Fig. 7 ). The differential diagnosis includes microphthalmia with cyst, microphthalmia with cystic teratoma, ectopic brain tissue, and meningoencephalocele.




Fig. 7


Congenital cystic eye. Infant boy on day of birth noted to have a cystic orbital mass at birth. Axial contrast-enhanced CT reveals a large, heterogeneous cystic mass enlarging the orbit. In contrast to other ocular anomalies, no definite ocular structures are seen. At surgical exploration, congenital cystic eye was confirmed with only a small area of pigment consistent with uveal tissue.


Coloboma


Coloboma is a developmental anomaly that results from incomplete closure of the embryonic choroidal fissure, resulting in ectasia and herniation of vitreous into the retro-ocular space. The developmental insult occurs during gestational days 35 to 41. Colobomas may affect the iris, lens, ciliary body, retina, choroid, sclera, or optic nerve. Colobomas may be unilateral or bilateral and can be isolated or syndromic, as seen in CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth and development, genital malformations, and ear anomalies). Numerous other genetic disorders are associated with coloboma, including focal dermal hypoplasia, branchio-oculofacial syndrome, trisomies 13 and 18, and Aicardi syndrome.


On MR imaging, coloboma appears as a focal defect of the posterior wall of the globe, sometimes associated with microphthalmia ( Fig. 8 ). A minimal defect results in a small excavation along the posterior globe. A larger defect produces a retrobulbar cystic cavity outpouching from the posterior wall of the globe.




Fig. 8


Coloboma. Girl with CHARGE syndrome, right microphthalmos, and colobomata. ( A ) Axial contrast-enhanced CT obtained at 2 years of age reveals right micropthalmos and bilateral colobomata ( arrows ). ( B ) Axial fat-suppressed T2-weighted MR image at 16 years of age shows an interval right retinal detachment with a small residual cystic structure posterior to the right globe and a large choroidal coloboma involving the left eye ( arrow ).


Morning Glory Disc Anomaly


Morning glory disc anomaly (MGDA) is a congenital optic nerve anomaly characterized by a funnel-shaped excavation of the optic disc with a central glial tuft overlying the optic disc and an annulus of chorioretinal pigmentary changes surrounding the optic disc excavation.


Although MGDA is usually diagnosed clinically, imaging also distinguishes MGDA from optic nerve coloboma. MGDA has 3 distinctive MR imaging findings: (1) funnel-shaped appearance of the optic disc with elevation of the adjacent retinal surface; (2) abnormal tissue associated with the ipsilateral distal intraorbital optic nerve, effacing the adjacent perioptic nerve subarachnoid space; and (3) lack of the usual enhancement at the lamina cribrosa associated with the funnel-shaped defect at the optic papilla ( Fig. 9 ). Identification of MGDA at imaging should prompt a search for associated intracranial abnormalities, including midline craniofacial and skull base defects, vascular abnormalities, and cerebral malformations. In particular, brain MR imaging and internal carotid artery MRA should be performed because of an association with transphenoidal basal encephalocele and congenital steno-occlusive change of the internal carotid arteries (moyamoya disease) in these patients. MGDA can also be seen in association with PHACES ( p osterior fossa anomalies, h emangioma, a rterial and aortic arch anomalies, c ardiac anomalies, e ye anomalies, and s ternal anomalies and/or supraumbilical raphe).




Fig. 9


Morning glory disc anomaly (MGDA). A 21-month-old boy presenting with poor vision and sensory exotropia of the left eye. Ophthalmologic examination revealed a megalopapilla with a central glial tuft and changes consistent with MGDA. ( A ) Axial 3-dimensional T2 SPACE MR image reveals a funnel-shaped appearance of the posterior optic disc ( black arrow ) with elevation of the adjacent retinal surface ( arrowhead ). There is abnormal tissue associated with the distal intraorbital segment of the ipsilateral optic nerve, with effacement of the regional subarachnoid space ( white arrow ). ( B ) Axial fat-suppressed T1-weighted MR image shows discontinuity of enhancement at the lamina cribrosa ( arrrow ), with enhancement extending along the most distal aspect of the optic nerve.


Staphyloma


Staphyloma results from thinning and stretching of the uvea and sclera and involves all layers of the globe. Risk factors include severe axial myopia, glaucoma, and severe ocular inflammation. Imaging reveals a posterior outpouching of the globe producing deformity in globe contour ( Fig. 10 ).




Fig. 10


Staphyloma. A 3-year-old girl with nystagmus, pale optic discs, and esotropia. Axial T2-weighted MR image shows bilateral staphylomas right greater than left. There is smooth outpouching of all layers of the globes along the temporal aspects of the optic nerves bilaterally ( arrows ). The optic nerves appear diminutive in keeping with either optic nerve hypoplasia (congenital) or atrophy (acquired).


Hypertelorism, Hypotelorism, and Cyclopia


Hypertelorism denotes increased distance between the medial orbital walls. Hypertelorism is associated with several craniofacial disorders, including cephaloceles, syndromic agenesis of the corpus callosum, and syndromic coronal craniosynostosis ( Fig. 11 A). Hypertelorism must be distinguished from dystopia canthorum in which the medial orbital walls are normally spaced but the medial intercanthal distance is increased, as seen in various types of Waardenburg syndrome.




Fig. 11


Hypertelorism and hypotelorism associated with craniosynostosis. ( A ) Three-dimensional (3D) CT image in a 9-month-old girl with brachycephaly and exophthalmos reveals hypertelorism and bilateral cleft lip and palate ( long arrows ). There is bicoronal synostosis ( short arrow ) and wide patency of the metopic suture ( arrowhead ) consistent with the known diagnosis of Apert syndrome. ( B ) 3D CT image in a 7-month-old girl with trigonocephaly shows premature fusion of the metopic suture resulting in frontal ridging ( arrowhead ) associated with hypotelorism.


Hypotelorism denotes decreased distance between the medial orbital walls. Hypotelorism is also associated with a variety of disorders, including the holoprosencephalies (HPE) and premature fusion of the metopic and sagittal sutures (see Fig. 11 B). Cyclopia or cyclophthalmia denotes complete fusion of the optic vesicles resulting in a single median eye. Synophthalmia represents partial fusion of the optic vesicles resulting in duplication of some anterior structures. Both cyclophthalmia and synophthalmia can be associated with HPE. Other manifestations of HPE include ethmocephaly (hypotelorism with median proboscis) and cebocephaly (hypotelorism with rudimentary nose and single nostril).


Large/Small Orbit


A large orbit can be congenital or acquired and results from causes such as cephalocele, bony deformity as seen in NF-1, and bony or orbital masses (see Figs. 6 and 7 ). A small orbit accompanies anopthalmia and microphthalmia (see Figs. 2 and 3 ). Exorbitism denotes shallow orbits as seen in syndromic craniosynostosis (see Fig. 11 ). Exorbitism should not be confused with proptosis in which there is mass effect within the orbit causing ventral protrusion of the globe.


Optic Nerve Hypoplasia


Optic nerve hypoplasia (ONH) is a developmental anomaly characterized by optic nerve underdevelopment. Bilateral ONH is associated with syndromic disorders such as septo-optic dysplasia. On imaging, the affected optic nerves and part or all of the optic chiasm and tracts appear small (see Fig. 10 ). The differential diagnosis for optic hypoplasia is optic atrophy resulting from a variety of causes such as prior infection/inflammation, trauma, irradiation, retinopathy of prematurity (ROP), and vascular insult.


Persistent Hyperplastic Primary Vitreous


Persistent hyperplastic primary vitreous (PHPV) results from failure of the embryonic hyaloid vasculature to involute, resulting in persistence of hyperplastic primary vitreous and the capillary vascular network covering parts of the lens. PHPV is typically unilateral and results in congenital microphthalmos, leukocoria, and cataract. Bilateral PHPV is associated with congenital conditions such as Norrie disease and Warburg disease.


The appearance of PHPV has been likened to that of a martini glass with the glass represented by triangular retrolental fibrovascular tissue and the martini glass stem represented by the stalk of hyaloid remnant extending to the optic disc in Cloquet canal ( Fig. 12 ). On CT, PHPV appears as increased density of the vitreous with a V-shaped or linear structure presumed to represent a remnant of the Cloquet canal. On MR imaging, the retrolental fibrovascular tissue and stalklike hyaloid remnant are hypointense on T1- and T2-weighted images with contrast enhancement. Hemorrhage and layering vitreous debris may be seen on imaging. Absence of calcification on CT is an important distinction from retinoblastoma ( Box 1 ).




Fig. 12


PHPV. A 1-year-old girl with esotropia, nystagmus, and bilateral chorioretinal colobomas. Axial 3-dimensional T2 SPACE MR image shows a triangular deformity at the posterior aspect of the left lens ( black arrow ) that is contiguous with a linear hypointensity extending toward the optic disc representing the stalk of hyaloid remnant of the Cloquet canal ( arrowhead ). There are also bilateral chorioretinal colobomas ( white arrows ).


Box 1





  • Normal-sized eye



  • Calcified mass




    • Retinoblastoma (single or multiple enhancing lesions, grows into vitreous or choroid)




  • Noncalcified mass




    • Coats disease (no enhancing mass, lipoproteinaceous hyperintense subretinal exudate)





  • Microphthalmia



  • Unilateral




    • PHPV (subhyaloid or subretinal blood-fluid levels, retrolental tubular mass along the hyaloid canal that enhances)




  • Bilateral




    • ROP (no or minimal enhancement, dystrophic calcification late in disease)



    • Bilateral PHPV (see earlier)



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Mar 13, 2017 | Posted by in NEUROLOGICAL IMAGING | Comments Off on Imaging of Pediatric Orbital Diseases
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