|Year : 2006 | Volume
| Issue : 4 | Page : 227-236
Imaging spectrum of pediatric orbital pathology: A pictorial review
Harsh Kandpal, Sushma Vashisht, Raju Sharma, Ashu Seith
Department of Radiodiagnosis, All India Institute of Medical Sciences, New Delhi - 110 029, India
Department of Radiodiagnosis, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
A wide spectrum of pediatric orbital disorders can occur in the pediatric age group. Cross-sectional imaging plays an important role in the diagnosis and management of these patients. We reviewed our imaging record and collected representative cases of pediatric orbital pathology. The purpose of this pictorial essay is to illustrate the imaging features of various orbital lesions encountered in children.
Keywords: Imaging, pediatric orbit
|How to cite this article:|
Kandpal H, Vashisht S, Sharma R, Seith A. Imaging spectrum of pediatric orbital pathology: A pictorial review. Indian J Ophthalmol 2006;54:227-36
|How to cite this URL:|
Kandpal H, Vashisht S, Sharma R, Seith A. Imaging spectrum of pediatric orbital pathology: A pictorial review. Indian J Ophthalmol [serial online] 2006 [cited 2020 May 28];54:227-36. Available from: http://www.ijo.in/text.asp?2006/54/4/227/27946
A wide spectrum of orbital pathology is seen in the pediatric population. A multi-modality imaging approach plays a vital role in the diagnosis of these entities, many of which are unique to this age group. While some lesions have characteristic imaging findings, others have a nonspecific appearance and need pathological confirmation to arrive at a specific diagnosis.
We retrospectively reviewed our imaging archive and compiled representative cases of a wide gamut of pediatric orbital pathology. The purpose of this article is to highlight the salient imaging features of various pediatric orbital lesions and to discuss the role of imaging in these conditions.
| Inflammatory diseases|| |
Orbital infections can affect primarily the preseptal, postseptal or the subperiosteal compartments. About 60-80% of the inflammatory diseases of the orbit originate in the paranasal sinuses. Except in cases where the inflammation is clinically limited to the preseptal space, imaging should be performed to know the extent of inflammation and to look for any associated complications. Although computed tomography (CT) is the imaging modality of choice in most cases of orbital infection, magnetic resonance imaging (MRI) is best suited for intracranial complications like cavernous sinus thrombosis.
The CT features of orbital cellulitis include diffuse soft tissue stranding of the orbital fat with thickening of the orbital structures and proptosis [Figure - 1]. Associated sinusitis and bone erosion may be seen and advanced cases can be complicated by formation of orbital abscess which appear as fluid collections [Figure - 2] showing peripheral enhancing rim of varying thickness. Small air pockets may be seen within the inflammatory process.
Subperiosteal abscess is an ophthalmic emergency as it may cause rapid elevation of orbital pressure, leading to visual impairment. It usually results from contiguous spread of infection from the paranasal sinuses and is seen as a hypodense lesion with peripheral ring enhancement in the extraconal space often with marked proptosis [Figure - 3]. Air fluid level, if seen, is pathognomonic.
Inflammatory pseudotumor of the orbit is a nongranulomatous inflammatory process of unknown etiology which presents clinically as painful exophthalmos. It represents the second most common inflammatory condition of the orbit in childhood. Although most cases are unilateral, children are more likely to have bilateral disease. CT features are nonspecific and include variably enhancing infiltrative mass which can either involve the orbit diffusely [Figure - 4]a or can primarily involve orbital structures like retrobulbar fat; lacrimal gland [Figure - 4]b; extraocular muscles [Figure - 4]c; outer dural sheath of the optic nerve or the globe. MRI is more specific than CT because the fibrous nature of the mass is reflected by its low signal intensity on T1-weighted (T1W) and on T2-weighted (T2W) images [Figure - 5]. Nevertheless, the imaging features of orbital psuedotumor are nonspecific and can be mimicked by various other orbital masses like lymphoma, rhabdomyosarcoma, hemangioma, lymphangioma and metastatic tumors. Pseudotumor continues to remain a diagnosis of exclusion based on clinical features, response to steroid treatment, laboratory tests and may require biopsy for confirmation in a few cases.
| Congenital anomalies|| |
Dermoid and epidermoid cysts are the most common congenital lesions of the orbit. They possibly arise from the entrapped ectoderm within the orbital sutures. Most are located adjacent to the orbital rim, usually near the outer canthus [Figure - 6]. Infrequently, they may arise deeper in the orbit and cause unilateral proptosis [Figure - 7]. CT or MRI shows a well-circumscribed cystic lesion which may contain fat or foci of calcification and may have slight enhancement in its wall. Lipid components are evident in 40 to 50% lesions. Large lesions may remodel the adjacent bone resulting in bone expansion, thinning or scalloping [Figure - 6]. Imaging may reveal presence of a fat-fluid level in dermoid cysts [Figure - 7]. With rupture, there is marked adjacent inflammatory reaction and the lesions become somewhat ill-defined.
Congenital cystic eye is a rare condition which results from the failure of the optic vesicle to invaginate and form the globe. On imaging, a cystic orbital mass is seen in place of the normal globe [Figure - 8] which may have septations and can cause orbital enlargement. There may be a rudimentary connection to the thinned out optic nerve and the primitive dysplastic lens may appear as a nodular focus adjacent to the cyst wall.
Coloboma is a congenital anomaly which results from incomplete closure of the embryonic fissure. It is characterized by a cleft-like defect, most commonly in the infero-nasal quadrant of the globe. Colobomas of the eyelid, lens or the optic nerve may also be seen. Some cases of coloboma may have microphthalmia with an associated cyst and dysplastic intraocular contents [Figure - 9].
Cephalocele represents herniation of the meninges with or without the brain parenchyma via defects in the bone. CT or MRI shows the bony defect and an associated cystic mass in the orbit [Figure - 10]. MRI is more useful in showing contiguity with intracranial contents and other associated brain anomalies.
| Vascular diseases|| |
Vascular lesions of the orbit comprise an important group of orbital pathology, especially in infants and children. MRI is the modality of choice for the imaging and characterization of vascular lesions because of its higher soft tissue contrast and intrinsic sensitivity in detecting vessels and blood products. The most common vascular lesions in the pediatric age group are capillary hemangioma orbital lymphangioma and orbital varix. Other orbital vascular lesions like cavernous hemangioma, arteriovenous malformation and carotid cavernous fistula are less common in children.
Capillary hemangioma is the most common orbital vascular tumor in infants which usually presents at birth or shortly thereafter. These are characterized by a phase of rapid growth in the first few months followed by a period of stabilization and eventual involution by seven to eight years of age. It is important to recognize this lesion as conservative management with steroids is effective. Most capillary hemangiomas are extraconal in location and tend to occur in the anterior part of the orbit. On CT, they appear as well circumscribed or infiltrative lesions with characteristic intense homogenous enhancement [Figure - 11]. Intracranial extension through the superior orbital fissure or optic canal can be seen occasionally. MRI typically reveals a heterogeneous signal intensity lesion moderately hypointense on T1W images, with hyperintense signal on T2W images and prominent contrast enhancement. About 50% of capillary hemangiomas may show enlargement with valsalva or crying. The lobulated outline and the characteristic internal architecture of the lesion (septations, intra and peri-lesional vessels) are better seen on MRI than on CT. Unlike capillary hemangioma which is a vascular tumor, the so-called "cavernous hemangioma" is a slow flow venous vascular malformation, typically well circumscribed and intraconal in location [Figure - 12].
Lymphangioma (venous lymphatic malformation) is an unencapsulated mass of thin-walled vascular and lymphatic channels which does not increase in size with valsalva or crying. They are the commonest vascular malformations in children and typically have a propensity to bleed. Since the intervening stroma between vascular channels contains foci of lymphoid cells, they tend to enlarge during episodes of upper respiratory tract infection because of the hyperplasia of the lymphoid component. Unlike capillary hemangiomas which are self-limiting, lymphangiomas show slow but progressive enlargement in the first two decades of life. Imaging reveals a multi-compartmental cystic-solid mass which tends to insinuate around normal structures and unlike hemangiomas, shows only slight to moderate enhancement. On ultrasonography (USG), they appear as a predominantly cystic mass with multiple septations [Figure - 13]. MRI is better than CT in showing the internal architecture, cystic areas and especially blood products [Figure - 14]. The lesion is isointense to slightly hyperintense to brain on T1W images and hyperintense on T2W images and may reveal evidence of hemorrhage as blood fluid levels (representing blood products in different stages of degradation) on MRI [Figure - 15].
Primary orbital varix is a distensible low-flow venous malformation characterized by abnormal dilatation of the orbital veins. Since these veins are in continuity with the systemic circulation, they result in intermittent proptosis whenever the systemic venous pressure increases. Orbital varices can also form secondary to arteriovenous shunting (carotid cavernous fistula) or venous occlusive disease (dural venous sinus thrombosis). Intralesional thrombosis, calcification or hemorrhage can occur. On USG varices are seen as tortuous dilated anechoic tubular channels with slow venous flow. A thrombosed varix may appear hyperechoic. CT and MRI show well-defined, tortuous enhancing channels which often have a club-like configuration with the tapering end towards the orbital apex [Figure - 16]. The demonstration of an increase in size during prone coronal scans, during valsalva maneuver or during jugular compression is pathognomonic of orbital varices [Figure - 17]. An association of orbital varices with intracranial venous malformations is reported in 10% cases and therefore investigation should include imaging for the intracranial veins.
| Neoplasms|| |
A wide spectrum of benign and malignant neoplasms can arise in the pediatric orbit. These can be categorized based on their tissue of origin, into tumors of mesenchymal origin (rhabdomyosarcoma, histiocytosis, leukemia and lymphoma), neural origin tumors (Retinoblastoma, optic nerve glioma, meningioma, schwannoma, neurofibroma and neuroblastoma) and vascular malformations or tumors (already discussed). Imaging plays a vital role in their diagnosis and management by depicting the mass and its extent.
Rhabdomyosarcoma (RMS) is the most common mesenchymal orbital tumor in children (median age eight to nine years) which usually presents with rapidly progressive proptosis. CT reveals a relatively well-defined soft tissue density mass (isodense to the extraocular muscles) which may invade the surrounding structures. The tumor may involve both the extraconal and intraconal compartments, may cause permeative bone destruction [Figure - 18] and bony expansion and may extend intracranially. On MRI they appear isointense to muscle on T1W and hyperintense on T2W images, showing moderate and uniform contrast enhancement. Imaging findings alone are nonspecific and can be mimicked by other orbital masses like lymphoma, leukemia, pseudotumor, neuroblastoma, metastases, hemangioma, lymphangioma, Langerhans cell histiocytosis and aggressive fibromatosis.
Langerhans cell histiocytosis is a disorder of unknown etiology seen primarily in children. The isolated form (eosinophilic granuloma) often involves the orbital bones. Plain radiograph or CT appearance of a well-defined punched out lytic lesion with bevelled edges is characteristic [Figure - 19]. The associated soft tissue mass can encroach on the orbit or the brain, can be well-defined or diffusely infiltrative and has a nonspecific appearance on CT or MRI [Figure - 19].
Fibrous dysplasia occurs mainly in children and young adults and frequently involves the orbit. Plain radiograph and CT reveal characteristic ground glass appearance and expansion of the involved bone.
Secondary tumors or orbital metastasis in children is most commonly seen with neuroblastoma, in as many as 20% cases. CT or MRI reveals an aggressive infiltrative soft tissue mass associated with bone destruction [Figure - 20]. Orbital metastasis may occasionally be seen in patients with Ewings sarcoma and RMS. Granulocytic sarcoma or chloroma results from leukemic infiltration of the soft tissue which commonly involves the orbit. These are especially seen in patients with acute myelogenous leukemia as focal intra or extraconal masses. Imaging reveals an irregular mass of nonspecific appearance with frequent bone erosion. The optic nerve is one of the "sanctuary sites" for leukemic cells due to suboptimal penetration of the chemotherapeutic drugs. Leukemic infiltration is seen as optic nerve enlargement and enhancement on imaging. Like leukemia, pediatric patients with lymphoma can have orbital, optic nerve or intraocular involvement.
Optic nerve glioma usually occurs in childhood (median age two to six years). In this age group, optic nerve glioma is typically a slow-growing tumor which presents with proptosis and visual loss. Thirty per cent cases are associated with neurofibromatosis Type 1 (NF1). The tumor causes diffuse thickening, kinking or fusiform enlargement of the nerve [Figure - 21], with moderate to marked enhancement which is generally less than that seen with meningioma. Necrosis, hemorrhage or calcification are distinctly rare though cystic changes can be seen., Subtle erosion or expansion of optic canal is better appreciated on CT while MRI is better in showing intracanalicular, chiasmatic or retrochiasmatic tumor extension. Bilateral lesions indicate NF1 [Figure - 22]. The differential diagnosis of optic nerve glioma on imaging includes optic nerve sheath meningioma and orbital pseudotumor.
Plexiform neurofibroma is the most common orbital manifestation of NF1 which typically presents during the first decade of life. On imaging it appears as an ill-defined, infiltrative, soft tissue mass which may involve the retrobulbar fat, the extraconal space including eyelid and adjacent subcutaneous tissue [Figure - 23]. The other orbital associations of NF1 include presence of optic pathway gliomas (in 15 to 40% cases) and sphenoid wing hypoplasia, which results in the characteristic appearance of "bare orbit" on plain radiograph [Figure - 23].
| Intraocular lesions|| |
Retinoblastoma is the most common intraocular tumor of childhood. Imaging is essential in determining the extent of the lesion and presence of intracranial metastases. The presence of calcification is the most characteristic feature of retinoblastoma and is best depicted by CT, which typically reveals solitary or multiple foci of calcification (in 90%) within a soft tissue density intraocular mass [Figure - 24] and [Figure - 25]. It is noteworthy that the rare diffuse infiltrating variety of retinoblastoma and the extaocular component of the tumor are devoid of calcification., Since MRI is not sensitive for the detection of calcification, it cannot confidently recognize lesions smaller than 2 to 3 mm. Notwithstanding this, MRI is better than CT for retrobulbar, optic nerve and intracranial involvement. MRI is also more specific than CT in the differentiation of retinoblastoma from other causes of leucocoria in childhood (like Coat's disease and persistent primary hyperplastic vitreous), in which the presence of opaque media may obviate ophthalmoscopic recognition. On MRI, retinoblastoma is characterized by marked hypointensity on the T2W sequence and shows moderate to marked enhancement [Figure - 26]. Since retinoblastoma is bilateral in one-third cases and may occasionally be associated with additional intracranial tumors in the pineal (trilateral retinoblastoma) [Figure - 27] and suprasellar location (tetralateral retinoblastoma), one must specifically look for subtle lesions in the contralateral eye and should always exclude additional intracranial tumors.
Persistent primary hyperplastic vitreous (PHPV) is characterized by unilateral leucocoria and microphthalmia in a full-term child. The clinical diagnosis of PHPV is often hampered by the presence of opaque ocular media. USG, CT or MRI typically show a vascular (enhancing), triangular or tubular retrolental tissue which represents the persistent fetal tissue in the Cloquet's canal [Figure - 28]. Presence of fluid level and increased density in the vitreous chamber, microphthalmia, small irregular lens and a shallow anterior chamber are other imaging findings seen in PHPV. There may be associated retinal or posterior hyaloid detachment which is better evaluated by MRI than CT. In contrast to PHPV, retinopathy of prematurity is usually bilateral, seen in premature low birth weight infants and may be associated with oxygen administration.
Coat's disease is a primary vascular anomaly of the retina, characterized by telangiectatic, leaky retinal vessels that lead to progressive deposition of exudates (in the subretinal or intraretinal location) which eventually cause massive retinal detachment. Most (90%) cases are unilateral and usually occur in young boys. In the early stages, CT or MRI are normal and the diagnosis is best established on fluorescein angiography. CT and USG are useful in the diagnosis of Coat's disease [Figure - 29]. MRI findings are more specific. The lipoproteinaceous subretinal exudates in Coat's disease appear hyperintense on both T1W and T2W MRI and the detached retina may show enhancement, reflecting the presence of abnormal retinal vessels. These signal characteristics and the absence of enhancement of the "subretinal mass" in Coat's disease helps to differentiate it from retinoblastoma.
| Optic nerve head drusen|| |
They are benign, usually bilateral and calcified acellular concretions which possibly result from the degenerating retinal nerve fibers. On CT, they characteristically appear as discrete, round, calcified specks at the optic nerve head [Figure - 30]. Drusen are generally not seen in early childhood as they are not sufficiently calcified.
| Parasitic cysts|| |
These are limited to endemic regions with poor sanitation. Orbital cysticercosis is usually seen within or near an extraocular muscle. They can also occur in the subconjunctival, subretinal location, in the optic nerve or in the eyelid. Imaging typically reveals a cystic lesion with a scolex (seen in 50% cases) [Figure - 31]. Cystic lesion alone without a scolex or only diffuse myositis in presence of positive ELISA test, is also diagnostic of cysticercosis. Orbital hydatid cyst is very rare and is seen as a well-defined cystic lesion on imaging with or without daughter cysts [Figure - 32].
| Trauma and foreign bodies|| |
Imaging plays an important role in the evaluation of orbital trauma. Plain radiograph is useful to look for intraocular foreign bodies and fractures. USG examination is generally not feasible in the acute setting but it can detect intraocular foreign bodies, lens dislocation, retinal detachment and vitreous hemorrhage. CT is the imaging modality of choice in the evaluation of orbital trauma as it is accurate in the detection of foreign bodies, bone and soft tissue injury. The classic "blow out fracture" is a fracture of the orbital floor which usually spares the orbital rim. CT scan allows visualization of the fracture site and may reveal herniation (and entrapment) of orbital fat, inferior rectus or inferior oblique muscle via the fracture line [Figure - 33]. MRI is contraindicated in the presence of intraorbital metallic foreign bodies.
| Conclusion|| |
Imaging plays a crucial role in the diagnosis and management of a wide range of pediatric orbital disorders. In conjunction with the pertinent clinical features, imaging findings provide accurate diagnosis in most cases. Recent advances in imaging technology like digital radiography, better and higher frequency USG equipments, isotropic-thin-section multidetector CT scanning and high field (3 Tesla) MRI scanners, promise a bright future in orbital diagnostic evaluation.
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