Orbital Surgical Guidelines: Pediatric Considerations

Abstract

Pediatric orbital and skull base surgery comprises a wide array of tumors. An understanding of the location of the lesion, nature of the disease, and surrounding anatomy is paramount to surgical planning in these small spaces. The goals of pediatric skull base surgery are to avoid injury to the surrounding structures, minimize cosmetic deformities, and remove some or all of the tumors based on anticipated pathology and biologic cost of removal. Safe surgery on many of these tumors requires an understanding of the location of the lesion relative to the optic nerve or orbit. This is particularly challenging because the dimensions of the orbital confines change continuously as one navigates from rostral to caudal. Management of these tumors may require a multidisciplinary approach including orbital surgery, neurosurgery, otolaryngology, oral maxillofacial surgery, plastic surgery, and interventional neuroradiology.

Introduction

Pediatric orbital and skull base tumor surgery is challenging, given the small surgical space and rarity of the majority of these pathologies. Careful surgical planning is required to avoid injury to the globe, cranial nerves, brain, and sinuses. Understanding the location of the orbital tumor in relationship to the optic nerve is essential to avoid injury resulting in permanent vision loss. Additionally, consideration of the tumor characteristics and anticipated pathology can inform the choice of the appropriate surgical approach. Optimal outcome requires knowledge of the limitations of each orbital approach and which members of a multidisciplinary team to involve. The purpose of this article is to provide the principles of pediatric orbital and skull base tumor surgery. Critical in the consideration of all of this is that the younger the child, the higher the risk of amblyopia due to any aberration of clear, binocular vision.

Typical Pathologies

Pediatric orbital tumors can be considered in two broad classifications: based on the tissue of origin (osseous and cartilaginous tumors, neural, mesenchymal, intraocular, vascular, inflammatory, or cystic lesions) and based on the clinical and histologic aggressiveness of the lesion. ¹ Common benign lesions include dermoid or epidermoid cysts, teratoma, tumors of bony origin (fibrous dysplasia and juvenile ossifying fibroma), optic nerve pilocytic astrocytoma (glioma), and congenital vascular lesions (lymphangioma, capillary hemangioma, varix, venous malformation, and orbital arteriovenous malformations). Common malignant orbital tumors include rhabdomyosarcoma, osteosarcoma, chondrosarcoma, fibrosarcoma, Ewing's sarcoma, neuroblastoma, Langerhans cell histiocytosis, and Burkitt's lymphoma. Lesions may be encapsulated or infiltrate the surrounding tissue, be highly vascularized, or occur in relative vascular isolation.

The reported incidence of pediatric orbital tumors varies based on the nature of the reporting center (primary or tertiary), geographic area, proximity to pediatric hospitals, and referral patterns. In childhood and adolescence, the majority of orbital lesions are benign. ² A high percentage of benign orbital lesions are inflammatory, including granulomatous inflammation, idiopathic orbital inflammation, and IgG4-related orbital inflammation. These lesions may mimic other benign or malignant orbital lesions and require diagnostic biopsy to guide treatment. ²

The clinical manifestations of these pathologies can vary. Proptosis is a common early feature as the eye is displaced forward by the mass, producing measurable proptosis. Other clinical evidence of an orbital lesion includes optic neuropathy, decreased eye movements, and pain. Given that the clinical signs can be nonspecific, imaging is routinely required. The use of dedicated high-resolution orbital magnetic resonance imaging and computed tomography provides details regarding the location and infiltration of the surrounding tissue, and often strongly suggests histopathology. ³

Anatomic Location

Understanding the bony anatomy and dimensions of the pediatric orbit is a critical part of surgical planning. During childhood, there is a period of generalized growth that slows over time. Neurocranial growth is continuous, with greatest expansion by the age of 2 years, followed by slower subsequent growth. By age 10 years, neurocranial growth is 95% complete. ⁴ Facial skeletal growth is discontinuous, hormonally driven during puberty and growth spurts. In general, facial dimensions are 40% of the adult size at 3 months of age and 80% of the adult size by 5 years of age. ⁴ At birth, the maxillary and ethmoid sinuses are present; however, the maxillary sinus is underdeveloped. The maxillary sinus shows biphasic growth, expanding around age 3 years and between ages 7 and 18 years. Between ages 3 and 7 years, the ethmoid and sphenoid sinuses grow significantly in size. The last paranasal sinus to develop is the frontal sinus, visible by 6 years of age. Pneumatization of the frontal sinus at the level of the orbital roof occurs by 7 years of age with complete pneumatization by age 15 years, whereas pneumatization of the sphenoid sinus is complete by 12 years of age.

Orbital depth reaches 75% of adult length by 6 years of age and 90% by 11 years of age, paralleling cranial growth. ⁵ Congenital developmental or neoplastic entities may produce a large orbit (encephalocele, neurofibromatosis), or a small orbit (anophthalmia, microphthalmia), that in turn alters facial bony growth. Syndromes associated with craniosynostosis may produce hypertelorism, hypotelorism, or shallow orbits. The pediatric population may have different orbital sizes and spectra of orbital diseases. However, the principles of safe and effective orbital surgery apply to all patients, irrespective of age. ⁶

The orbital confines can be divided into five surgical spaces (subperiosteal, extraconal, intraconal, subtenons, and subarachnoid), each of which can harbor pathology. Direct communication exists between the orbital and intracranial spaces via the superior orbital fissure and the optic canal, as well as the emissary foramina.

Surgical Approaches and Limitations

The choice of the appropriate surgical approach requires an understanding of the advantages and limitations of each option. Consideration must be given to the operative exposure and the potential risk to the globe, optic nerve, and cranial nerves. An important surgical principle is to avoid mobilizing a tumor across the plane of the optic nerve. Observance of this principle guides the choice of the surgical approach.

The orbit can be entered directly along each of its four walls by lateral orbitotomy, transconjunctival lower eyelid orbitotomy, medial transcaruncular orbitotomy, and upper lid crease superior orbitotomy. A combination of these approaches may be required in the cases where the lesion bridges the orbital quadrants.

Lateral orbitotomy can be performed through either lid crease or lateral canthal incision, both of which are well camouflaged. Maximum lateral and posterior access and operative space can be achieved by adding an osteotomy of the lateral wall. This approach provides up to 270 degrees of access to superior, inferior, and laterally located tumors in any of the orbital spaces.

A transconjunctival lower eyelid orbitotomy with or without canthotomy and cantholysis is utilized for more inferior and medial intraconal and extraconal lesions. This approach is limited at the inferior orbital apex where there is little room between the orbital floor and the optic nerve. These cases may benefit from the removal of the adjacent bone either directly or endoscopically to provide operating space.

A medial orbitotomy can be performed through a medial upper eyelid crease or transcaruncular incision. The transconjunctival approach is particularly versatile as it provides direct access to the medial wall of the orbit posterior to the lacrimal bone and can be easily combined with an inferior transconjunctival incision. This approach allows for access to medial intraconal and extraconal tumors and those in close proximity to the optic nerve. Again, removal of the medial orbital wall (ethmoid lamina) is useful in the cases in which the tumor is large and apically based.

Lesions within the superior orbit superior to the levator muscle are directly approached through an upper lid crease incision. Dissection is performed up to the orbital periosteum, which, when incised and reflected, provides a wide view. Visualization can be improved by burring the overhang of the orbital rim, taking care to avoid injury to the supraorbital neurovascular bundle. Removal of this segment of the rim does not change appearance or brow projection.

Although the superior orbital fissure and optic canal may be visualized through the superior, medial, and lateral orbital approaches, lesions that extend through to the intracranial space are most often best approached via a combined craniotomy and orbital approach.

Cranio-orbital approaches include frontotemporal orbitozygomatic, pterional (frontotemporal), and supraorbital (keyhole) approaches. ⁷ The frontotemporal orbitozygomatic approach can be performed with or without an orbital osteotomy, which provides good exposure in cases of superior apical orbital lesions, including those within the optic canal, superior orbital fissure, and apical intraconal space. Pterional approaches allow for minimal brain retraction and are appropriate for lesions that include a significant intracranial component. The supraorbital keyhole approach is made through an eyelid crease or eyebrow incision, followed by a burr hole made lateral to the supraorbital notch into the skull base. While of more limited exposure than the pterional approach, for those appropriately selected cases, it provides a minimally invasive alternative. The use of neurosurgical microinstruments and an endoscope with careful retraction on the globe provides the appropriate amount of exposure for the necessary tumor resection.

Advances in endoscopic approaches have provided new accessibility through the sinuses. ⁸ Endoscopic orbital decompression surgery provides bony removal of the medial and inferior wall of the orbit. ⁹ With these walls removed, tumors in the medial and inferior apical orbit can be more safely accessed than via an orbital approach, wherein one's view becomes narrower as one approaches the most important structures. Additionally, visualization through a transcranial supraorbital keyhole is substantively improved endoscopically when approaching the orbital roof and the superior portion of the optic nerve. Lesions in the far lateral orbit should never be approached via an endonasal endoscopic approach, as this substantively increases the risk of damage to the optic nerve and the extraocular muscles. ¹⁰ In addition, in very young children, careful examination of imaging and patient must be performed to understand the size of the nasal cavity and the degree of sinus development.

Intraoperative Navigation

The use of intraoperative navigation devices in orbital surgery has been reported to improve localization of lesions and safety of orbital decompression, and to simplify reconstructive surgery. ¹¹ Navigation systems include Brain Laboratory (BrainLAB AG, Munich, Germany), Stealth Station (Medtronic, Dublin, Ireland), iNtellect (Stryker Corporation, Kalamazoo, Michigan, United States), and Navigation System II (Stryker Corporation). Although the companies claim accuracy in the 1- to 2-mm range, in practice, errors of ≥5 mm are not uncommon, undermining the routine practical value of the device. The inaccuracy of the devices can in some cases be tied to the mobility of tumors that reside within the compressible orbital fat. In others, the accuracy is reduced by the mobility of scalp fiduciaries upon which some systems are registered. The most accurate registration is usually to bony landmarks and requires immobilization of the head for the duration of the case. For very young children, with thin skulls, Mayfield fixation may not be safe. In general, given the challenge of working within the orbit where the important neurovascular structures are obscured by orbital fat, a detailed knowledge of the three-dimensional anatomy of the operative space should take precedence and intraoperative navigation should be used to confirm a suspected position, rather than to guide the approach.

Multidisciplinary Cases

Multidisciplinary coordination is required for optimal medical and surgical management of the more complex cases. ¹² Neuroimaging is reviewed with radiology to anticipate lesional histology, location, and infiltration. Direct communication with outpatient or inpatient pediatric teams facilitates the requisite medical support. For orbital malignancies, the input of medical and radiation oncology provides adjunctive treatment strategies. In cases of orbital vascular malformations, interventional neuroradiology may be able to sclerose the lesion prior to a debulking procedure, making the surgery safer, or obviate the need for surgery altogether. Based on the nature of the lesion, the surgical teams will variably include orbital surgery, neurosurgery, otolaryngology, plastic surgery, oral maxillofacial surgery, and craniofacial surgery. In the cases where eye-sparing surgery is not possible, patients will require the talents of an ocularist or prosthodontist to produce an ocular or orbital prosthesis.

Reconstruction Options

Reconstruction options are highly case dependent. If the result of tumor resection is a small defect in the lateral wall of the orbit, reconstruction is not required. However, larger defects and those of the orbital roof, medial wall, and floor of the orbit may require reconstruction to avoid enophthalmos or pulsatile proptosis (in the case of the orbital roof). These defects may be repaired with a porous polyethylene barrier sheet with integrated titanium for additional rigidity. Replacement of bony structures has increasingly used absorbable fixation devices so as to have lower likelihood of inhibition of growth. In more complex reconstructions, a 3D orbital custom implant can be fashioned preoperatively. Free vascularized skin-muscle or skin-muscle-bone flaps are utilized when large defects involve multiple layers of the facial skeleton, or when radiation treatment is anticipated. ¹³ Dural defects are repaired with a combination of collagen matrix grafts or fascia lata along with vascularized reconstruction when possible to avoid cerebrospinal fluid (CSF) leakage.

Enucleations can be reconstructed with either an integrated porous implant or a dermal fat graft to replace the lost ocular volume. A dermal fat graft provides the additional benefit of postoperative growth tied to the growth of the child, which in turn stimulates normal eye socket and facial bony expansion. ¹⁴ Ocularists craft progressively enlarging ocular conformers to promote socket and facial growth. Orbital exenterations may result in loss of both the orbital contents and the lids, in which case the ocularist will fashion a press-on orbital prosthesis or the patient will wear an eye patch. If the pathology and location of the tumor permit sparing the eyelid and conjunctiva, a 3D reconstruction can be accomplished with a temporalis transfer and dermis fat graft, followed by a frontalis upper eyelid suspension. ¹⁵

Case Examples

Optic Glioma

A 4-year-old presented with rapidly progressive left proptosis found to have an optic nerve mass ( Fig. 1 ). The vision was no light perception. The lesion extended to the prechiasmatic intracranial segment of the optic nerve. The child demonstrated no clinical or genetic evidence of neurofibromatosis type 1 (NF1). As further growth of the lesion would threaten the contralateral vision, a complete resection of the optic nerve from globe to the chiasm was performed through a combined craniotomy-orbitotomy. This provided a durable tumor-free interval of now greater than 14 years.

Fig. 1.

Optic nerve glioma. ( a ) External photograph of left proptosis. ( b,c ) Sagittal and axial T1 magnetic resonance imaging (MRI) reveals an encased optic nerve glioma (*).

Cavernous Hemangioma

An 18-year-old woman presented with a superomedial intraconal cavernous hemangioma producing optic nerve edema ( Fig. 2 ). The lesion was approached through a superomedial conjunctival peritomy. The medial and superior rectus muscles were rotated inferiorly and laterally, which rotated the tumor anteriorly. The tumor was engaged with cryotherapy to aid in traction and the tumor was incised, decompressed, and collapsed, further aiding its complete resection. The optic nerve returned to its normal contour postoperatively.

Fig. 2.

Cavernous hemangioma. ( a ) Coronal T1 magnetic resonance imaging (MRI) of a left superomedial cavernous hemangioma (*). ( b ) A cryotherapy probe was used to engage the tumor.

Orbital Venous Lymphatic Malformation

A 4-year-old boy presented with left ptosis and proptosis. Neuroimaging revealed a congenital left cranio-orbital venous malformation. Given the severity of presentation, lesion type, lack of spontaneous improvement, and risk of amblyopia, the decision was made to proceed with surgical intervention. Through a cranio-orbital approach, both the intracranial and intraorbital compartments of the lesion were resected ( Fig. 3 ).

Fig. 3.

Cranio-orbital venous malformation. ( a ) External photograph of left orbital proptosis, complete ptosis, and ecchymosis. ( b,c ) Axial T1 and coronal T1 magnetic resonance imaging (MRI) of a congenital cranio-orbital venous malformation ( arrowheads ).

Intraosseous Hemangioma

A 12-year-old boy presented with painless left hyperglobus and proptosis. Magnetic resonance imaging revealed a large highly vascular honeycomb intraosseous lesion within the maxilla eroding to the inferior orbit strongly suggestive of a cavernous hemangioma of bone ( Fig. 4 ). He underwent preoperative embolization performed by interventional neuroradiology to reduce intraoperative blood loss. The following day, a combined surgical approach was performed with oral maxillofacial surgery to resect the lesion through a transconjunctival swinging eyelid orbitotomy. The defect was repaired with a 3D custom implant that had been constructed preoperatively based on the predicted surgical defect.

Fig. 4.

Intraosseous hemangioma. ( a ) External photograph of left hyperglobus and proptosis. ( b,c ) Coronal computed tomography (CT) and magnetic resonance (MR) images of a highly vascular honeycomb intraosseous lesion within the maxilla eroding to the inferior orbit diagnostic of a cavernous hemangioma of the bone (*).( d ) Postoperative month 1 photograph following resection with repair using a custom 3D implant.

Sickle Cell Infarction

A 22-year-old man with sickle cell disease hemoglobin SS presented with sudden profound orbital cellulitis and compressive optic neuropathy due to infarction of the marrow space of the greater wing of the sphenoid bone which produced a large subperiosteal exudative effusion ( Fig. 5 ). ¹⁶ Through medical management to control the sickle cell crisis and intravenous corticosteroids to reduce the orbital edema, optic nerve function was restored and surgical intervention avoided.

Fig. 5.

Sickle cell infarction. ( a ) External photograph of a sickle cell disease hemoglobin SS patient with profound left orbital cellulitis and compressive optic neuropathy. ( b ) Coronal T1 magnetic resonance imaging (MRI) reveals an infarction of the marrow space of the greater wing of the sphenoid bone creating a large subperiosteal exudative effusion ( arrowhead s).

Orbital Osteoma

An 18-year-old woman presented with 6 months of worsening proptosis ( Fig. 6 ). On neuroimaging, she was found to have a large osteoma extending from the right ethmoid sinus to the lateral orbit inferior to and displacing the optic nerve and extraocular muscles superiorly. A combined lateral orbitotomy with bone flap and endoscopic endonasal approach was performed to bisect and remove the osteoma in toto.

Fig. 6.

Orbital osteoma. ( a ) External photograph of a right proptosis and medial fullness. ( b,c ) Axial and coronal computed tomography (CT) reveals a large osteoma extending from the right ethmoid sinus to the lateral orbit inferior to and displacing the optic nerve and extraocular muscles superiorly.

Fibrous Dysplasia

An adolescent girl found to have Albright's syndrome consequent to evaluation for a pathologic fracture was further shown to have bilateral fibrous dysplasia involving both orbits and narrowing the optic canals ( Fig. 7 ). Although optic nerve function was unaffected at the time, anticipated growth of the lesion in this location is typically associated with vision loss. The patient underwent a series of bisphosphonate infusions and did not show signs of disease progression over the next few years.

Fig. 7.

Fibrous dysplasia. ( a ) External photograph of a teenage girl found to have Albright's syndrome. ( b ) Axial magnetic resonance imaging (MRI) reveals bilateral fibrous dysplasia (*) involving both orbits and narrowing the optic canals that underwent a series of bisphosphonate infusions.

Chondrosarcoma

A 7-year-old boy presented with a large calcified intraorbital mass producing vision loss. It was removed through a lateral canthotomy orbitotomy and proved to be a chondrosarcoma ( Fig. 8 ). Cure required exenteration, which, given the deep orbital location of the lesion, could be achieved through an eyelid- and conjunctival-sparing approach with immediate reconstruction using temporalis muscle transfer for volume and vascular supply capped with a dermal fat graft to form the socket and fornices. This permitted him to wear a more cosmetically appealing ocular prosthesis rather than a typical orbital prosthesis that is required when the lids are sacrificed. There has been no tumor recurrence 15 years later.

Fig. 8.

Chondrosarcoma. ( a ) External photograph of a patient with a right superolateral mass. ( b ) Axial computed tomography (CT) reveals a superior orbital lesion with areas of calcification (*) found to be a chondrosarcoma. ( c ) Postoperative photograph following an eyelid conjunctival sparing orbital exenteration with dermis fat graft to allow for an ocular prosthesis.

Teratoma

A large craniofacial tumor was identified on prenatal ultrasound prompting an ex utero intrapartum treatment (EXIT) procedure and emergent tracheostomy ( Fig. 9 ). Neuroimaging demonstrated a lesion extending from the anterior cranial vault through the superior orbital fissure into the lateral orbit and down into the pterygopalatine space and out through the mouth. The lesion was embolized preoperatively and through a 23-hour surgical procedure that included neurosurgery, orbital surgery, ear, nose, and throat (ENT), plastic surgery, and the remarkable efforts of the pediatric anesthesia team that provided more that 20 total blood volume replacements, the teratoma was completely resected with preservation of vision.

Fig. 9.

Teratoma. ( a ) External photograph of a newborn with a large teratoma. ( b ) Axial computed tomography (CT) reveals a lesion extending from the anterior cranial vault through the superior orbital fissure into the lateral orbit and down into the pterygopalatine space and out of the mouth.

Pearls and Tips.

• It is critical to understand the precise location of a lesion in the orbital spaces (subperiosteal, extraconal, intraconal, subtenons, and subarachnoid), in relation to the optic nerve, oculomotor nerves, bony anatomy, and sinuses.

• An important surgical principle is to avoid mobilizing a tumor across the plane of the optic nerve. Observance of this principle guides the choice of the surgical approach.

• Tumor type is key in treatment planning and must be carefully considered: encapsulated versus infiltrative, malignant versus benign, and vascularized versus isolated.

• Intraoperative navigation can be extremely helpful.

• Multidisciplinary surgical teams may be required to remove complex pediatric tumors in an efficient and safe manner.