Disorders of neural tube closure in which there may be orbital abnormalities include cephaloceles, dermal sinus and cyst, neuroglial heterotopia, holoprosencephaly, septooptic dysplasia, absence of the septum pellucidum, craniosynostosis, and cranial facial syndromes.⁴⁵ Cephaloceles that commonly involve the orbit or optic pathways include sphenoidal, nasoorbital, and frontoethmoidal cephaloceles.²⁵,⁴⁶,⁴⁷,⁴⁸,⁴⁹,⁵⁰,⁵¹ Dermal sinuses, dermoids, and epidermoids are discussed later. Widening of the nasal bridge and hypertelorism should prompt a search for craniofacial anomalies, cephaloceles, and midline intracranial defects such as callosal agenesis.

Midface hypoplasia and hypotelorism are commonly associated with the holoprosencephalies.⁴⁵,⁴⁷,⁵² Midface and orbital anomalies associated with alobar holoprosencephaly include cyclopia (single midline orbit with proboscis and absent nose), ethmocephaly (median proboscis between two hypoteloric orbits), cebocephaly (rudimentary nose with single aperture and orbital hypotelorism), the rare median cleft lip with hypertelorism, and simple hypotelorism. Septooptic dysplasia anomalies with deficiency of the septum pellucidum and optic hypoplasia are considered a mild form of holoprosencephaly.⁴⁵,⁵²,⁵³

Unilaterally or bilaterally deformed orbits are commonly associated with craniosynostoses, particularly those involving the metopic suture, coronal suture, or multiple sutures.⁴⁵,⁵⁰ Hypertelorism with or without exorbitism is characteristic of syndromic coronal synostosis. Reconstructive craniofacial surgery is often required to improve appearance and preserve vision. Metopic synostosis results in hypotelorism. Treacher Collins syndrome (TCS) (mandibulofacial dysostosis) is as associated with microphthalmia and coloboma.

Neuroophthalmologic involvement often occurs with the neurocutaneous syndromes of childhood such as neurofibromatosis type 1 (NF1) (sphenoorbital dysplasia [Fig. 3.15]), optic glioma (Fig. 3.11), tuberous sclerosis (retinal neuroglial hamartoma), Sturge-Weber syndrome (choroidal venocapillary malformation with buphthalmos), and von Hippel-Lindau disease (retinal hemangioblastoma with retinal detachment and hemorrhage).⁴⁵

Disorders of migration that are often associated with ocular, orbital, or optic pathway abnormalities include dysgenesis of the corpus callosum and the lissencephaly syndromes.⁴⁵,⁵⁴,⁵⁵,⁵⁶,⁵⁷

Malformative abnormalities are neoplastic and nonneoplastic masses that arise from an aberration of development.²⁶,²⁸,²⁹,⁴⁵,⁵⁸ These are usually of neuroectodermal origin (e.g., dermoid or epidermoid) or mesodermal origin (e.g., lipoma). Benign teratomas can also be included in this category,⁵⁹ as can vascular anomalies. Malformative lesions are often cystic but may be solid or of mixed consistency. In the orbital region in childhood, malformative lesions include colobomas, duplication cysts of the eye, nasolacrimal duct (NLD) cysts, lacrimal ectopia, dermoids, epidermoids, benign teratomas, and (rarely) arachnoid cysts and lipomas.

Orbital infection is common in children and usually results from acute complicated paranasal sinus infection. Orbital involvement occurs from direct extension via infected intervening bone or via emissary veins (Fig. 3.20), or because of complications of sinusitis such as a ruptured mucocele or mucopyocele (Fig. 3.21). Other sources include trauma, extension of facial or dental infection (Fig. 3.22), and, rarely, hematogenous spread from systemic infection.³⁰ Infection is most often bacterial in origin, with Staphylococcus, Streptococcus, and Pneumococcus being the primary causative agents.⁷¹,⁷² Invasive fungal sinusitis can also spread to the orbit, especially in immunocompromised pediatric patients, primarily because of Mucor and Aspergillus. When infection affects only structures anterior to the orbital septum (skin, eyelids), it is termed preseptal (periorbital) cellulitis. When infection affects structures posterior to the septum, it is termed postseptal (orbital) cellulitis.

Pediatric patients with preseptal cellulitis typically present with rapid-onset soft tissue swelling and erythema, with or without pain, epiphora, and blurred vision. On imaging, there is diffuse soft tissue thickening of the skin and eyelids with adjacent fat stranding. The orbital septum tends to prevent postseptal spread of infection unless there is initiating sinus infection. The clinician should be alerted to sinus opacification, foreign object, or dental infection as a potential source of infection.

Postseptal cellulitis usually results from initiating bacterial sinus infection. Affected pediatric patients typically present with lid edema, proptosis, chemosis, and, if severe, impaired ocular motility. Postseptal extraconal cellulitis or phlegmonous change with or without subperiosteal abscess typically occurs in proximity to the infected sinus and thus occurs medially with ethmoid sinusitis (Fig. 3.20), inferiorly with maxillary antral sinusitis, and superiorly with frontal sinusitis. Contrast-enhanced CT demonstrates hazy increased density of the extraconal fat, with enlargement of extraocular muscles adjacent to extraconal cellulitis/phlegmon. Subperiosteal abscess appears as a low-attenuation, peripherally enhancing elliptical collection. Bone destruction, consistent with osteomyelitis, is sometimes seen. Spread of infection to the intraconal compartment results in orbital cellulitis with stranding of the intraconal fat. Dacryocystitis and dacryoadenitis can complicate or cause orbital infection.

Invasive fungal sinusitis with spread to the orbits is seen predominantly in immunocompromised pediatric patients, with a high mortality of 50% to 80%.⁷³ The responsible pathogens include Zygomycetes (e.g., Rhizomucor and Mucor) and Aspergillus species. The fungal organisms spread aggressively, with angioinvasion, bone invasion leading to bony destruction visible on CT, and hematogenous dissemination. Tuberculous infection is an important diagnostic consideration for destructive inflammatory sinonasal and orbital disease in endemic areas.

The most frequent vascular complication of orbital infection is thrombosis of the superior ophthalmic vein,⁹ which fails to enhance normally on contrast-enhanced CT or MR producing the “tram track” sign. Occasionally, severe postseptal cellulitis with significant infiltration and inflammation of the orbital fat and proptosis causes stretching and, rarely, vascular compromise of the optic nerve.

Complications of postseptal infection include osteomyelitis, epidural abscess, subdural empyema (Fig. 3.23), meningitis, cerebritis, parenchymal abscess, and cavernous sinus thrombophlebitis/thrombosis (Fig. 3.24). MRI is used to detect intracranial complications and osteomyelitis with T2-weighted fat-suppressed MR images, contrast-enhanced T1-weighted fat-suppressed MR images, DWI, and MRV. Rarely, steno-occlusive intracranial arterial complications occur, particularly in the presence of suppurative change and/or thrombophlebitis in the cavernous sinus.

Early treatment consists of appropriate antibiotics and, if necessary, surgical drainage of any abscess or obstructed sinus.

Idiopathic orbital inflammatory syndrome (IOIS), commonly referred to as orbital pseudotumor, is a nongranulomatous noninfectious benign inflammatory disease of the orbit with no identifiable cause, responsive to steroid therapy. IOIS is rare in children.⁷⁴ Affected pediatric patients present with pain, swelling, erythema, proptosis, and/or diplopia. The classic finding is “painful ophthalmoplegia.” Vision may be impaired if there is optic nerve involvement. Iritis and papillitis are more commonly seen in children than in adults. IOIS is bilateral in up to one-third of pediatric cases without an identifiable underlying systemic condition.⁷⁵ This is a diagnosis of exclusion, based on clinical history, disease course, and response to steroids. Histologically, there is an inflammatory/lymphoid infiltrate of orbital tissues acutely; in the subacute or chronic phase, fibroblasts and fibrosis are seen. However, biopsy is rarely performed as the diagnosis can usually be made clinically.

IOIS may be classified according to the primary site of involvement: anterior or diffuse orbital inflammation, orbital myositis, perineuritis and periscleritis, lacrimal adenitis, and apical orbital inflammation (Fig. 3.25). The mass-like
manifestation of IOIS is also referred to as “inflammatory pseudotumor.” Painful external ophthalmoplegia, also known as Tolosa-Hunt syndrome, is considered a variant of IOIS that involves the orbital apex, superior orbital fissure, and cavernous sinus (Fig. 3.26). The radiographic differential diagnosis of Tolosa-Hunt syndrome includes fungal infection, sarcoidosis, lymphoma, and meningioma.

On CT, depending on the site of involvement, IOIS may be characterized by preseptal soft tissue thickening and edema, orbital fat stranding, an enhancing orbital mass, enlargement of the extraocular muscles including their tendinous insertions, thickening of and stranding around the posterior globe or optic nerve sheath complex, enlargement and enhancement of the lacrimal gland, or soft tissue fullness in the orbital apex and cavernous sinus. MRI is helpful for evaluation of the cavernous sinus region for abnormal enhancement or mass lesions.⁷⁶

Differential diagnosis is broad, because IOIS can affect any structure in the orbit and may be diffuse or mass-like. Orbital cellulitis, neoplasms including lymphoma and leukemia, sarcoidosis (Fig. 3.27), granulomatosis with polyangiitis (Wegener granulomatosis) (Fig. 3.28), and other granulomatous diseases may have similar imaging appearance. In a child, biopsy should be considered if there is an atypical clinical course, if the abnormality is refractory to steroid therapy, or if localized involvement raises the possibility of a malignancy such as lymphoma or rhabdomyosarcoma (RMS).⁷⁴

After infection and other local and systemic causes have been excluded, systemic steroid therapy with a slow taper may be initiated and is considered first-line treatment.⁷⁷ Recurrence of symptoms with steroid withdrawal is unusual in the pediatric population.⁷⁸

Chorioretinitis is inflammation of the posterior uvea of the globe. It is usually caused by congenital (TORCH) infections, with cytomegalovirus and congenital toxocara being the most common pathogens in the neonatal age group. On imaging, the vitreous may appear hyperdense on CT and hyperintense on MRI, without a discrete mass.

Ocular toxocariasis occurs as an intraocular inflammatory response to the death of the larva of the nematode Toxocara canis, sometimes leading to sclerosing endophthalmitis. It is usually unilateral and seen in older children.¹⁴ CT findings include homogeneous vitreal density corresponding to a detached retina, organized vitreous, and inflammatory subretinal exudate, similar in appearance to Coats disease and noncalcified retinoblastoma. On MRI, there is variable hyperintensity on T1- and T2-weighted images.

Optic neuritis is not uncommon in children. It is diagnosed using the same clinical criteria used in adults, including subacute vision loss, pain with eye movement, visual field deficits, and a relative afferent pupillary defect. In contrast to adults, children with optic neuritis more frequently have bilateral involvement, profound vision loss, and prominent disc swelling. Etiologies include viral, postviral, granulomatous, postradiation, posttraumatic, demyelinating (Fig. 3.29), neoplastic (e.g., leukemia), and unknown underlying processes.²⁹ On imaging, the optic nerve appears hyperintense relative to normal white matter on T2-weighted MR images, is variably swollen, and enhances. In one series, the authors found that the risk of multiple sclerosis after a first episode of optic neuritis in children is increased if one or more white matter lesion is seen on a brain MRI performed at the time of initial presentation. None of the patients in their series with a negative brain MRI at presentation were diagnosed with MS for the duration that they were followed (88.5 months).⁷⁹ The differential diagnosis includes neuromyelitis optica, in which optic neuritis, hypothalamic signal abnormality, and long-segment spinal cord involvement are MRI features.

Retinoblastoma (RB), a malignant tumor of the immature retina, is the most common primary intraocular tumor in children (80% of all primary ocular cancers), and the third most common intraocular tumor in all age groups. It occurs
in infancy, even in utero, with 95% of cases occurring before age 5 years.⁸² RB is rarely seen in older children.⁸³ Tumors may show an endophytic growth pattern, with tumor growing toward the vitreous; it may have an exophytic growth pattern with tumor in the subretinal space, causing an overlying retinal detachment; or it may have a mixed growth pattern. A diffuse infiltrating, plaque-like form occurs less commonly, where the tumor is flat on the surface or beneath the retina, with no obvious mass or calcifications.⁸³

RB develops as a result of a “two-hit” oncogenic mutation involving the Rb1 tumor suppressor gene, occurring between the 3rd month postconception and age 4 years, when retinoblasts are maturing. Both copies of the Rb1 gene have to be mutated for retinoblastoma to develop. In the familial form (40% of cases, autosomal dominant transmission), all germ cells have an existing mutation of one copy of the gene; tumor develops when the second copy mutates. In the sporadic form, the germ cells are normal, and the somatic retinal cell acquires mutations in both copies of the Rb1 gene.⁸⁴ Affected pediatric patients with the familial form are more likely to have bilateral disease and multiple tumors. The average age of presentation is 7 months for bilateral cases and 24 months for unilateral cases.⁸⁵ In pediatric patients with familial RB, second primaries include soft tissue sarcomas, osteosarcomas, carcinomas, CNS tumors, leukemias, uterine sarcomas, lung cancers, and skin cancers. In these patients, the second primary is a greater cause of death than the RB itself.⁸⁶,⁸⁷ Radiation exposure greatly increases the risk of development of a second primary, particularly if occurring before age 1 year.⁸⁸ For this reason, CT is no longer recommended for imaging RB.

RB is a major diagnostic consideration in a child presenting with leukocoria, the most common presenting sign (60%), but it is a late sign, with high survival rate but low rate of globe salvage. Strabismus at presentation (20%) is considered an early sign with high survival rate and higher chance of globe salvage.

MRI is used for diagnosis, staging, and treatment monitoring.²² A combination of ophthalmoscopy, US, and MRI with gradient echo sequences has been shown to effectively detect calcifications. When intraocular calcification within a normal-sized or enlarged globe is present in a young child, RB must be suspected, as very few other simulating lesions contain calcification.⁸⁹ The calcific foci are variable in size and number (Fig. 3.31A). The diffuse infiltrating plaque-like form, however, may have very little calcification. The tumor itself appears mildly to moderately hyperintense to vitreous on T1-weighted sequence and hypointense on T2-weighted sequence (Fig. 3.31B). Calcifications appear hypointense on MRI, especially on gradient echo T2-weighted and FSE T2-weighted sequences. There is generally moderate to significant tumoral enhancement.

Optic nerve invasion and orbital invasion increase the risk of metastatic disease.⁹⁰,⁹¹ Massive choroidal invasion is considered the only other risk factor.⁹²,⁹³ With orbital extension, tumor can disseminate or extend intracranially. It is therefore important to include imaging of the entire orbit and the brain to evaluate for tumor spread.

Trilateral retinoblastoma refers to a primary midline intracranial tumor, usually in the pituitary or pineal region, in the presence of bilateral retinoblastoma (Fig. 3.32). When there are two midline tumors, the term quadrilateral retinoblastoma is sometimes used.⁸²

Grossly, retinoblastoma is characterized in its early stages by a white-gray nodule on the retina. Later, growth can extend through the retina causing detachment, and involve the vitreous humor. Microscopically, the tumor shows poorly differentiated cells with high nucleus-to-cytoplasm ratios, frequent mitotic figures, and frequent apoptotic cells (Fig. 3.33).

Treatment is best determined by a multidisciplinary team. Options include enucleation, cryoablation, laser photocoagulation, and chemothermotherapy.

RMS is the most common primary nonocular orbital malignancy in children.²⁹ RMS accounts for ˜50% of all pediatric soft tissue sarcomas and 15% of all pediatric solid tumors. Just over one-third of all RMSs are seen in the head and neck region, with the most common locations being the orbit (Fig. 3.34), masticator space, and paranasal sinuses (Fig. 3.35).²⁶,²⁹,⁴⁵,⁵⁸,⁶⁸ For orbital RMS, the average age at diagnosis is 7 to 8 years, but it can be seen in older patients. In data collected by the Surveillance, Epidemiology, and End Results (SEER) program, the 5-year survival was found to be highest in children aged 1 to 4 years (77%) and worst in infants and adolescents (47% and 48%, respectively). Orbital site was the most favorable (86%).⁹⁴ In children, the embryonal and alveolar subtypes predominate. Affected pediatric patients usually present with rapid-onset unilateral proptosis and globe displacement.

CT, MRI, and PET-CT are used to evaluate and stage RMS. Imaging of the head, chest, and abdomen is obtained for tumor staging. When the tumor is small, the margins are usually well defined; when large, the mass may have irregular margins and appear infiltrative, with surrounding bone and soft tissue invasion. On CT, it is usually isodense to muscle (Fig. 3.34). On MR, RMS is iso- or hypointense on T1-weighted sequence when compared to the brain.⁹⁵ Tumors are of variable signal intensity compared to cerebral cortex and demonstrate decreased diffusivity. Internal hemorrhage is uncommon. The degree of enhancement is variable. CT is used to assess osseous involvement or destruction. MRI is superior for soft tissue delineation, for distinguishing tumor from sinus inflammation, for assessing bone marrow involvement, and for detecting intracranial extension or metastasis. Because there are no orbital lymphatics, nodal metastasis is rare except in very advanced cases.⁸⁴

Differential diagnosis includes pseudotumor, lymphoma, leukemic infiltration, and metastatic disease. Neuroblastoma is a relatively common cause of orbital metastatic disease, typically in the first decade of life. Unlike RMS, there are usually multiple extraconal tumor masses with lytic permeative destruction of bone and spiculated periosteal reaction. Ultimately, tissue diagnosis is necessary to distinguish RMS from other noninflammatory solitary orbital tumors, with the exception of infantile hemangioma.

Treatment includes surgery, radiation, and/or chemotherapy. Whereas smaller tumors may be completely excised with a 5-year survival of ≥90%, larger more infiltrative tumors usually require postoperative radiation therapy to control residual disease. When there is significant residual tumor, 5-year survival is ≤35%. Combination chemotherapy helps to improve survival.

NF1 is an autosomal dominant disorder resulting from mutation of the neurofibromin gene on chromosome 17q11.2 and characterized by café au lait spots, axillary or inguinal freckles, neurofibromas and plexiform neurofibromas (PNFs), optic nerve gliomas, Lisch nodules in the eye, sphenoid bone dysplasia, and thinning of long bones.⁹⁶ Orbital manifestations include orbital neoplasms (the most common of which is optic glioma [Fig. 3.11]), plexiform neurofibromas, orbital osseous dysplasia (Fig. 3.15), and congenital glaucoma.⁹⁷

PNFs are transpatial and infiltrative. They arise from nerve fascicles, tend to grow along nerves, and may involve multiple nerve branches and plexuses, causing significant morbidity. There may be resultant thickening of periorbital soft tissues (Fig. 3.15), enlargement of the bony orbit, and extensive infiltration of the orbital soft tissues.⁹⁸ Although they are more often extraconal,²⁶ intraconal involvement produces increased density of the intraconal fat; enhancing, irregular nodular thickening of the optic nerve sheath complex; and thickening and enhancement of the uveal/scleral layer, believed to represent PNFs of these structures.⁹⁸ PNFs have the potential to transform into malignant peripheral nerve sheath tumors (MPNSTs).

Optic pathway gliomas (OPGs) in NF1 are relatively benign and typically occur in children. Considered low-grade astrocytomas, they are distinct from the extremely rare malignant optic gliomas that are typically seen in adults.⁹⁹ On imaging, an optic nerve glioma may be fusiform (Figs. 3.11 and 3.36) or exophytic; the nerve itself is enlarged and may be elongated, with kinking or buckling. On MR, the tumor is iso- to hypointense on T1-weighted sequence and iso- to hyperintense on T2-weighted sequence when compared to normal white matter (Figs. 3.11 and 3.36), with variable enhancement.¹⁰⁰

Of the OPGs that are low-grade astrocytomas, different imaging features have been noted between those associated with NF1 (NF-OPG) and those not associated with NF1 (non-NF-OPG).¹⁰¹ In pediatric patients with NF-OPG, the most common site of involvement is the optic nerve, the original shape of the optic pathway is preserved, and cystic components are uncommon. In pediatric patients with
non-NF-OPG, the most common sites of involvement are the chiasm and hypothalamus, the tumor is larger and more masslike, and cystic components are more common. Pediatric patients with OPG may present with decreased vision or proptosis from mass effect. Additional symptomatology results from intracranial tumor. The differential diagnosis for mild enlargement of the optic nerve without enhancement includes the so-called “NF spot”, which is sometimes implicated if the lesion undergoes spontaneous regression.

The prognosis in children with NF-OPG is better than in those with non-NF-OPG, with the tumor often remaining quite stable in imaging appearance over a number of years. The current treatment includes surgery, chemotherapy, and radiation.

There is a wide spectrum of orbital lymphoid lesions or lymphoproliferative disorders, ranging from reactive lymphoid hyperplasia to pseudotumor (IOIS) to malignant lymphoma. Reactive lymphoid hyperplasia and orbital lymphoma are essentially indistinguishable from each other on imaging⁷⁵ and occur rarely in children. Malignant lymphoma may arise in the orbit, in the sinonasal region with extension into the orbit, or may be a systemic disease that includes an orbital focus. Any orbital structure may be involved, including the lacrimal gland, extraocular muscles, and orbital fat. On MR, lesions have intermediate to low signal on T1-weighted sequences and are isointense to cerebral cortex on T2-weighted sequences, with decreased diffusivity. The globe is rarely deformed by an adjacent lymphoma. Tumors occur in the anterior portion of the orbit, retrobulbar region, or superior orbital compartment (Fig. 3.37).

Leukemia is one of the most common pediatric malignancies and includes acute lymphoblastic leukemia, acute myelogenous leukemia (AML), and chronic myelogenous leukemia.¹⁰² Chronic lymphocytic leukemia is rare in children. Orbital involvement is mainly in the form of deposits of leukemic cells in the bone or soft tissue. These deposits are known as granulocytic sarcomas in the setting of AML, also called chloroma, because of the greenish color of myeloperoxidase on gross examination. Chloromas are usually seen in the subperiosteal region, in the lateral or medial orbital wall (Fig. 3.38). Dural or leptomeningeal disease may be present concurrently.¹⁰²

Differential diagnosis of orbital lymphoma and a focal leukemic deposit includes RMS, Langerhans cell histiocytosis (LCH), and benign lymphoid disorders. The differential diagnosis for diffuse orbital leukemic involvement is metastatic disease, primarily neuroblastoma.

LCH is a clonal lesion of unknown etiology that is best classified as a neoplasm. LCH is characterized by proliferation and infiltration of abnormal histiocyte-like cells within various tissues. LCH preferentially affects children between the ages of 1 and 4, with disseminated or localized forms of disease that
have been variously referred to as Hand-Schüller-Christian disease, Letterer-Siwe disease, and eosinophilic granuloma.⁹

Lesions in children are mostly seen in the bone or bone marrow. Localized orbital involvement is not uncommon. Clinical signs and symptoms include proptosis, edema, erythema, and periorbital pain. Lesions are usually seen in the superior or superolateral orbital wall. Ocular involvement is rare.

On CT, LCH produces sharply defined lytic bone lesions with “punched-out” or beveled margins. On MR imaging, the associated soft tissue mass is of intermediate to low signal intensity relative to cerebral cortex on T2-weighted images with moderate to marked homogeneous or heterogeneous enhancement. There is often intracranial extension, involving the epidural space. Multiple lesions may be seen.⁹

The differential diagnosis for LCH includes ossifying fibroma, giant cell lesion, aneurysmal bone cyst (ABC), lymphoma, and metastasis. Ossifying fibroma is expansile with osseous matrix. Giant cell lesion and ABC are expansile lytic lesions, often with preservation of a thin rim of bone at the margin of the lesion on CT and characteristic fluid-fluid levels on MR.

The imaging appearance of infantile hemangiomas depends on the clinical stage. During the proliferative phase, a lobulated, sharply defined, homogeneous, highly vascular soft tissue mass is seen, with intense enhancement. On MRI, proliferating hemangioma is iso- or hypointense to muscle on T1-weighted MR images, moderately hyperintense with vascular flow voids on T2-weighted MR images (Fig. 3.39), and intensely enhancing.¹⁰⁴ During the involuting phase, enhancement and vascularity diminish. After complete involution, a focal region of fibrofatty tissue remains.

A subgroup of patients with infantile hemangiomas has structural anomalies elsewhere in the body, with involvement of the brain, cerebral vasculature, aorta, eyes, and chest wall. In 1978, Pascual-Castroviejo et al., described the association of facial and scalp “hemangiomas” with brain abnormalities, malformations of the extra- and intracranial blood vessels, and congenital heart disease.¹⁰⁵ Subsequently, Frieden et al. coined the acronym “PHACES”¹⁰⁶ denoting the major features of this neurocutaneous association: posterior fossa malformations, hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, eye abnormalities, and sternal clefting and supraumbilical abdominal raphe. The most common posterior fossa malformation is unilateral cerebellar hypoplasia with a prominent ipsilateral CSF space. Intracranial arterial anomalies include persistent fetal anastomotic connections (e.g., persistent trigeminal artery), aplasia or hypoplasia of the carotid or vertebral arteries, and dilatation and tortuosity of the carotid or cerebral arteries. Steno-occlusive changes with moyamoya collaterals have also been observed.¹⁰⁷ Eye findings include microphthalmia, optic nerve hypoplasia, congenital cataracts, morning glory anomaly, and increased retinal vascularity. The unilateral or bilateral hemangiomas in patients with PHACES tend to be large, regional, and plaque-like, sometimes in a beard-like distribution or in the midline. Therefore,
pediatric patients with large infantile hemangiomas in the face or head and neck region should undergo brain MRI and MRA to evaluate for PHACES association.¹⁰⁸

High-flow vascular malformations include AVMs and arteriovenous fistulae (AVF). Low-flow vascular malformations include venous malformations (VMs), lymphatic malformations (LMs), and combined malformations.

VMs are well-defined, transpatial multiloculated cystic masses. The venous lakes typically appear hyperintense on T2-weighted MR images, similar in signal to CSF, with gradual enhancement of the contained venous blood with contrast. The presence of rounded signal voids on MR or calcific foci on CT due to phleboliths is a diagnostic feature of VMs.

Orbital LMs present with proptosis that is sometimes apparent at birth or that manifests subsequently because of rapid enlargement from intercurrent infection or hemorrhage. LMs are typically transpatial lesions. LMs with cysts larger than 1 cm in size are termed macrocystic and are sharply defined. Microcystic LMs consist of small or tiny cysts that are less well defined and sometimes appear more infiltrative. Components of the lesion insinuate within and between normal tissues and structures of the lid and orbit. Cyst contents are hyperintense on T2-weighted MR images unless complicated by hemorrhage, in which case hypointense blood products will be seen. Signal intensity on T1-weighted MR images varies depending on protein content and chronicity of hemorrhage. Macrocystic LMs appear as distinct large locules of fluid spaces separated by enhancing septations. Microcystic LMs may appear to be enhancing without appreciable fluid-filled cystic spaces. Fluid-fluid levels within the cystic spaces related to blood products of various ages are characteristic of LMs (Fig. 3.40).

Many of the orbital low-flow vascular anomalies demonstrate features of both LM and VM and are thus considered combined lesions. Interestingly, these lesions are associated with a significant incidence of intracranial venous anomalies (cavernous malformations and prominent developmental venous anomalies), (Fig. 3.41) and even occasionally AVF.¹⁰⁹

Orbital AVM and AVF are uncommon high-flow lesions that produce pulsatile proptosis and sometimes a bruit. On imaging, they are characterized by enlarged arterial feeders
and early draining veins. AVM is distinguished from AVF by the presence of a tangle of small vessels known as a nidus between the feeding and draining vessels.

A primary orbital varix presumably occurs as a result of congenital weakness of the venous wall, resulting in dilatation of one or more orbital veins. A tangled mass of venous channels overlaps with the spectrum of VM. With Valsalva maneuver, the varix enlarges and may lead to increased proptosis or globe displacement.⁸⁴ Orbital varices may be associated with intracranial vascular anomalies or malformations, including arteriovenous shunts. On CT, calcifications representing phleboliths may be seen. On MR, they are hyperintense on T2-weighted MR images and enhance. Unless thrombosed, they should fill in with contrast at the venous phase (Fig. 3.42).

CCF occurs when there is a tear in the cavernous portion of the internal carotid artery, allowing arterial blood to enter the cavernous sinus, leading to increased cavernous sinus pressure and reversal of blood flow in the veins that normally drain into the cavernous sinus. Affected pediatric patients with CCFs present with proptosis, chemosis, pulsating exophthalmos, an auscultable bruit, and/or objective pulsatile tinnitus. On imaging, there is engorgement of the superior ophthalmic vein (Fig. 3.43) and enlargement of the ipsilateral extraocular muscles. Venous thrombosis of the cavernous sinus or superior ophthalmic vein may occur. Mimics of CCF include AVMs and AVFs; isolated dilatation of the superior ophthalmic vein can also occur.¹¹⁰ Therefore, correlation with clinical history and examination is paramount. Diagnosis of CCF can be confirmed with CTA, MRA, or conventional catheter angiography.

Traumatic hyphema (posttraumatic bleeding into the anterior compartment) results from disruption of the iris or ciliary body vessels, leading to extravasation of blood into the anterior compartment. On CT, the anterior compartment appears hyperdense. Corneal laceration leads to decreased
anterior compartment volume, manifested as decreased anteroposterior dimension of the anterior compartment.

Globe rupture, also termed open globe injury, is an ophthalmologic emergency. It is a major cause of blindness, and prompt diagnosis and treatment are crucial to prevent further injury. Unrecognized globe rupture may rarely result in bilateral blindness due to sympathetic ophthalmia, a bilateral diffuse granulomatous intraocular inflammation that occurs following unilateral ocular surgery or penetrating trauma.

The injured eye is known as the exciting eye, and the contralateral eye is known as the sympathizing eye.¹¹² The time from ocular injury to onset of sympathetic ophthalmia ranges from a few days to decades, with 80% occurring within 3 months and 90% within 1 year.¹¹³,¹¹⁴ It is believed to occur as a result of autoimmune inflammatory response to ocular antigens that become exposed to the immune system following loss of globe integrity. Therefore, if the injured globe is nonviable, or if there is little chance of the injured globe regaining visual function following trauma, prompt enucleation may help prevent the occurrence of sympathetic ophthalmia.

On CT, a ruptured globe is suggested by abnormality in the globe contour (Fig. 3.44A), loss of normal globe volume, scleral discontinuity, intraocular gas (Fig. 3.44B), or intraocular foreign objects.¹¹⁰ Decreased anterior chamber depth suggests an anterior globe laceration. With increased anterior chamber depth, traumatic rupture of the posterior sclera should be suspected. A discontinuity in the posterior sclera allows vitreous to prolapse through the defect, leading to decompression of the vitreous and posterior sagging of the lens.¹¹⁵ With vitreous hemorrhage, hazy diffuse or mass-like hyperdensity may be seen in the posterior chamber.

When there is traumatic deformity of the globe, the zonule fibers of the lens can stretch and tear, resulting in dislocation of the lens. Posterior dislocation is more common than anterior dislocation, in part because the iris prevents the lens from migrating anteriorly. If only some of the fibers are torn, then the lens may remain in position on one side, while angling posteriorly on the opposite side where it projects into the vitreous humor (Fig. 3.45).¹¹⁰

With blunt trauma, there may be tearing or rupture of the lens capsule. When that occurs, fluid enters the crystalline lens, normally the least hydrated organ of the body. On CT, therefore, a ruptured lens may retain a relatively normal contour but appear less dense than usual (Fig. 3.46).

There are three main types of detachments in the globe: posterior hyaloid detachment (posterior vitreous detachment), retinal detachment, and choroidal detachment.

In posterior hyaloid detachment, the vitreous body becomes separated from the retina, and vitreous can dissect into the potential space between the posterior hyaloid membrane and the retina.⁸⁴ Traction on the retina at points that are still attached increases the risk of subsequent retinal tears and detachment. The detached posterior hyaloid membrane
may be thickened and become visible on imaging. This condition may be seen in children with PHPV.

Retinal detachment is separation of the sensory retina from the retinal pigment epithelium. Serous or exudative detachment usually occurs as a result of breakdown of the blood-retina barrier due to tumor, inflammation, vasculopathy (e.g., Coats disease), hematologic disorders, or in association with congenital anomalies such as optic nerve colobomas and morning glory syndrome.¹¹⁶ When there is scarring or another process in the vitreous causing traction of the sensory retina from the pigmented layer, it is referred to as a traction detachment. With trauma, there may be subretinal hemorrhage, with or without a tear in the sensory retina. The presence of retinal hemorrhage in a child should raise suspicion for nonaccidental trauma.¹¹⁰

The retina is a very thin structure and is not visible per se on imaging. Retinal detachment is diagnosed on imaging based on the difference in appearance of the normal vitreous and fluid accumulated in the subretinal space. The subretinal fluid typically appears homogeneously hyperdense, with a lentiform or V shape, extending from the ciliary body anteriorly to the optic disc posteriorly (Fig. 3.47). If the subretinal fluid happens to be isodense/isointense to vitreous, it may escape imaging detection. US is considered a better modality for imaging retinal detachment than CT or MR.¹¹⁷

Choroidal detachment is separation of the choroid from the sclera. Serous or hemorrhagic fluid can then accumulate in the suprachoroidal space. The latter is seen in the setting of trauma; the former occurs in the setting of ocular hypotony, which may result from inflammation, traumatic perforation, or surgery.¹¹⁰ Suprachoroidal fluid collections appear biconvex, extending from the level of the vortex veins to the ora serrata (Fig. 3.48). Their CT and MR appearance depends on their composition and may be variably dense/intense. Choroid is thick, and the separated choroid is often visible on CT and MR.

MR is absolutely contraindicated if there is any suspicion of a potential intraorbital metallic object, as blindness may result if the patient is subjected to MR scanning because of migration of the object within the magnetic field.

CT is very sensitive for detecting metallic fragments even smaller than 1 mm in size (Fig. 3.49). Glass appears dense on CT but is less reliably detected than metal.¹¹⁸ Wood appears hypodense and may be mistaken for gas but should have a geometric or linear configuration.

The optic nerve can be directly injured in penetrating trauma, by bone fragments causing nerve laceration, or from a nerve sheath hematoma. It can also be indirectly injured from transmission of
forces to the optic nerve following blunt trauma or from vascular compromise. For evaluation of the optic nerve, MRI is necessary, after confirming the absence of any potential intraorbital metallic objects. Normally, the optic nerve should follow white matter signal. If there is disruption of the normal nerve contour, or if there is abnormally hyperintense signal in the optic nerve on T2-weighted sequence, optic nerve injury should be suspected.

Neonates are obligate nose breathers, and obstruction of the nasal passages leads to airway compromise.¹²⁰ Congenital causes include pyriform aperture stenosis, nasal cavity stenosis, and choanal stenosis or atresia. Large NLD cysts, craniofacial anomalies, and cephaloceles also cause obstruction. Stenosis of the entire nasal airway is usually bony and may be seen with maxillary hypoplasia.

Choanal atresia is congenital obstruction of the posterior choanae. Incidence has been reported to be between 1 in 5,000 and 1 in 9,000 live births. It is seen more often in females and is more commonly unilateral. Obstruction is invariably bony, with or without a membranous component. Recent literature suggests that mixed bony/membranous choanal atresia occurs in 70% of cases and pure bony obstruction in 30% of cases.¹²¹
There is also medialization of the pterygoid plates and lateral nasal walls (Fig. 3.50).

There are sometimes associated skull base abnormalities or defects.¹²² Approximately half of the affected pediatric patients have associated craniofacial anomalies such as CHARGE syndrome. CHARGE is an acronym for coloboma, heart defect, atresia choanae, retarded growth and development, genital hypoplasia, and ear anomalies/deafness. Major criteria (ocular coloboma; choanal atresia; characteristic ear abnormalities— particularly absent or severely hypoplastic semicircular canals (SCCs), hypoplasia of the vestibule, ossicular and other middle ear abnormalities (Fig. 3.51)¹²³; cranial nerve hypoplasia/aplasia) and minor criteria (cardiovascular malformations; genital hypoplasia; cleft lip/palate; tracheoesophageal fistula; hypothalamo-hypophyseal dysfunction; distinctive CHARGE facies; developmental delay) have been described. Individuals with all four major characteristics or three out of four major and three out of seven minor characteristics are reported to be highly likely to have CHARGE syndrome.¹²⁴

CT should be performed with the axial plane parallel to the hard palate at the level of the pterygoid plates. CT demonstrates obstruction of the posterior nasal cavity, characterized by medial bowing and thickening of the lateral nasal walls, enlargement of the posterior vomer, and a bony or membranous structure obstructing the choana representing the atretic plate. Bilateral choanal atresia should prompt inspection of the temporal bones for the typical diagnostic inner ear findings of CHARGE syndrome.

Syndromic craniosynostosis, TCS, and other craniofacial syndromes are associated with midnasal cavity stenosis due to midfacial hypoplasia.

Pyriform aperture stenosis is narrowing at the level of the anterior nasal cavity. On CT, there is marked stenosis of the pyriform apertures associated with a triangular morphology of the anterior hard palate. Images should include the maxillary dentition. If there is a single central megaincisor, then there is an association with holoprosencephaly and MR of the brain should be obtained (Fig. 3.52).

Lacrimal sac and NLD mucocele is described earlier in the Orbit section. NLD mucocele is common, especially in premature infants, and is an important cause of neonatal nasal obstruction. Most cases resolve spontaneously. Less commonly, pressure buildup may cause the imperforate distal membrane to balloon out into the nasal cavity, leading to an intranasal cystic mass and nasal obstruction. The entire enlarged cystic structure extending from the lacrimal sac to the inferior meatus is referred to as a nasolacrimal mucocele. This is well delineated on CT and MR, which demonstrate a dilated cystic structure at the medial canthal region contiguous with an expanded NLD, terminating in an intranasal submucosal cystic mass that projects beneath the inferior turbinate (Fig. 3.16).

During fetal development, the frontal bone is separated from the nasal bones by a fontanelle called the fonticulus frontonasalis. The nasal bones are in turn separated from the underlying cartilaginous nasal capsule by the prenasal space. The prenasal space extends up to the base of the brain and down to the nasal tip. Normally, projections of dura around the brain extend through these spaces in the midline and contact the ectoderm, then regress back toward the brain before these spaces are obliterated. By birth, the frontonasal suture is in the location of the obliterated fonticulus frontonasalis, the nasal cartilages and ethmoid bone are in the region of the obliterated prenasal space, and the frontal and ethmoid bones come together around a small ostium at the skull base called the foramen cecum, just anterior to the crista galli. If the embryonic dural projections do not regress properly, anomalies result.

Fissural cysts are cysts that arise along lines of fusion of embryologic facial processes. They include nasolabial cysts, nasopalatine duct cysts, and median palatal cysts.

Nasolabial cyst, also known as nasoalveolar cyst or Klestadt cyst, occurs at the base of the nasal ala and anterior nasal fold and may be bilateral.¹²⁸ Its density on CT and signal on MR vary depending on the cyst contents,¹²⁹ which may range from serous to mucous to complex if there is superimposed infection. Enhancement is variable.¹³⁰,¹³¹ When the lesion is large, scalloping of the adjacent bone may be seen (Fig. 3.55).

Nasopalatine duct cysts or median anterior maxillary cysts may be further classified as incisive canal cysts or palatine papilla cysts. The latter are uncommon. The former are thought to arise from nasopalatine duct epithelial remnants.¹³² Small incisive canal cysts are not uncommon in children. On CT, the cyst appears as a symmetrical pear-shaped, heart-shaped, or rounded lucent area with a sclerotic rim in the midline of the anterior primary palate (Fig. 3.55B). They develop around vital teeth and can cause splaying of the upper central incisor roots.

A median palatal cyst arises at the junction of the palatal processes in the midline. On CT, it appears as a midline lucent lesion in the hard palate.

Clefting results from abnormal development or fusion of facial processes.¹³³

Clefts that do not observe lines of embryonic fusion likely result from amniotic band disruption complex.¹³⁴ Here, rupture of the amnion leads to generation of fibrous bands that can adhere to and tether parts of the developing fetus. Fetal parts may become disrupted, damaged, or amputated by these bands. Craniofacial deformations are seen in approximately one-third of cases of amniotic band sequence.¹³⁵

Micrognathia is an abnormally small mandible whereas retrognathia refers to a receding chin, but these two findings often coexist. Micrognathia can be sporadic or inherited, isolated or syndromic. Micrognathia is a feature of trisomies 13, 18, and 9.¹³⁶ Symmetric micrognathia with hypoplastic and deficient zygomatic arches, malar flattening, and severe anomalies of the external and middle ears is a feature of TCS (Fig. 3.56A) and Nager syndrome. Mildly asymmetric
micrognathia with external, middle, and inner ear anomalies and branchial apparatus anomalies is the hallmark of branchiootorenal (BOR) syndrome. HFM is characterized by unilateral micrognathia, ipsilateral zygomatic arch deficiency, hypoplastic muscles of mastication, and external and middle ear anomalies (Fig. 3.56B).

Moderate to severe micrognathia is associated with airway obstruction. Mandibular hypoplasia tends to displace the tongue posteriorly and superiorly, which, in turn, prevents normal development of the palate resulting in a palatal cleft, as discussed above. The clinical triad of micrognathia, glossoptosis, and feeding difficulty is known as the Robin sequence, which is a feature of various syndromes, for example, velocardiofacial syndrome and Stickler syndrome.

Imaging of micrognathia is required primarily to assist surgical planning prior to mandibular reconstruction. Axial helical CT images using a low-dose algorithm are used to create multiplanar reconstructed images and a 3D model of the mandible and face.

The two most common predisposing factors for acute bacterial sinusitis are viral upper respiratory tract infection (URI) and allergy.¹³⁷ If symptoms are persistent (longer than 10 days), severe (high fever and purulent nasal discharge), or worsening after initial improvement, acute bacterial sinusitis is suggested. Symptoms beyond 30 days suggest subacute or chronic sinusitis.¹³⁷ The most common pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.¹³⁸,¹³⁹ Staphylococcus aureus and anaerobic organisms are seen more frequently in children with severe sinus symptoms or with chronic sinusitis (present for over a year).

The ethmoid air cells are separated by thin bony septations; each air cell drains through an independent ostium into the middle meatus.¹⁴⁰ These narrow ostia are readily obstructed by inflamed mucosa. When developed, the frontal sinuses are frequently the conduit for spread of infection to the orbit or brain, the latter related to a rich emissary venous plexus between the posterior frontal sinus mucosa and the meninges. Like the frontal sinus, an infected sphenoid sinus is more prone to the development of intracranial complications.

Pediatric sinusitis occasionally arises as a result of odontogenic infection.¹⁴¹ A key CT finding is a periapical lucency due to a periapical abscess or granuloma that is dehiscent into the floor of the maxillary antrum (Fig. 3.22B). Perforation after dental trauma or a dental procedure may lead to a tract that then epithelializes to form an oroantral fistula (Fig. 3.57). Congenital bone defects and dental cysts may also act as conduits for spread of infection to the maxillary sinus.

Sinus inflammation and congestion causes increased secretions and accumulation of submucosal fluid with venous congestion.¹⁴² On CT, inflamed sinus mucosa appears as peripheral soft tissue thickening. On MRI, mucosal secretions and submucosal fluid appear hyperintense on T2-weighted sequences and hypointense on T1-weighted sequences. There is a characteristic pattern of a thin rim of enhancement of the inflamed mucosa and nonenhancement of the underlying submucosal fluid (Fig. 3.58). These are findings of sinus inflammation or congestion and not necessarily sinus infection. Sinus CT and MRI often show mucosal thickening in children who do not have signs or symptoms of sinusitis or an URI.¹⁴³ Therefore, mucosal thickening and edema seen on imaging should not be reported as “sinusitis” without supportive clinical history. Layering fluid in a sinus (air-fluid level) is more suggestive of an acute infectious sinus process (Fig. 3.58).