Orbital Tumors


Background

The orbit is an anatomically complex structure containing the globe; extraocular muscles; fat; and vascular, nerve, glandular, and connective tissues.

The orbit in the broadest sense describes the cavity containing structures essential for ocular function and the bony architecture that encases them. This complex anatomical area was first described by Whitnall to resemble a pear, with its widest aperture anterior and narrowing posteriorly.

The bony orbit has its cellular ancestry from the mesenchymal cells surrounding the optic vesicle. Composed of 7 bones, a normal adult orbit holds a volume of 30 mL with a medial length of 45 mm, a width of 40 mm, and a height of 35 mm at its most anterior point.

Since the orbit is a relatively small anatomical area with little wasted space, space-occupying lesions that increase orbital volume may result in proptosis of the globe and may adversely affect visual and extraocular muscle function. However, Lin and colleagues reported that proptosis of less than 4 mm might go undetected, obscuring occult pathology. [1See the image below.

Patient with orbital tumor on the right. Note chemPatient with orbital tumor on the right. Note chemosis, ptosis, and proptosis. Patient is also lifting the right brow in an effort to elevate the ptotic lid.

History of the Procedure

In 1888, Krönlein first described the lateral orbitotomy approach. The Berke-Reese modification of this approach used an extended canthotomy. In place of the curved incision used by Krönlein, Stallard altered the approach taking it into the upper lateral brow area. Avoiding the lateral canthal region was at the core of the Wright modification of the Stallard approach. A hemicoronal (or bicoronal) approach, also referred to as the coronal approach, has been used by Kennerdal and others. [2Goldberg et al have popularized the transconjunctival approach and the transcaruncular approach. [3]

Endoscopic approaches have become more common, especially to treat medial orbital tumors. [4Image guidance has also become more frequently used in orbital surgeries performed via both nonendonasal and endonasal approaches. [567]

Problem

Orbital tumors have protean manifestations. Rootman et al reported that the major presenting symptom was proptosis, resulting from the mass effect. [8This occurred in 269 of the 601 patients evaluated or 44.8% of these patients.

Epidemiology

Frequency

The top 3 pediatric orbital tumors are dermoid cysts, capillary hemangiomas, and rhabdomyosarcoma. Retinoblastoma can spread from the globe to the orbit. Neuroblastoma can involve the orbit via metastases and is the most common metastatic tumor to the orbit in children. [910]

The top 3 adult orbital tumors are lymphoid tumors, cavernous hemangiomas, and meningiomas. Other tumors include those of the lacrimal gland, tumors form the surrounding sinuses, metastatic tumors such as breast cancer in women, and neural-based tumors. [11]

Etiology

Primary orbital tumefaction, although quite rare, encompasses a lexicon of benign and malignant neoplasia. All anatomical structures of the orbit can give rise to neoplasia. Direct extension from contiguous anatomical structures, lymphoproliferative disorders, and hematogenous metastasis results in secondary orbital invasion.

Capillary hemangiomas are the most common orbital tumors found in children. Lined by vascular endothelium and pericytes, these histologic benign lesions manifest at birth or within the first 3 months of life, enlarge rapidly, and begin to commence contracting around age 1 year. Other benign orbital lesions include dermoids, lymphangiomas, and histiocytic tumors.

Rhabdomyosarcoma, a mesenchymal tumor, is the most common primary malignant orbital tumefaction in children. These devastating lesions usually occur in children younger than 2 years or older than 6 years, and they have a predilection for the superior nasal orbit.

Neuroblastomas, Ewing sarcoma, Wilms tumor, and leukemias are the more common metastatic orbital lesions afflicting children.

Other malignant lesions include Burkitt lymphoma and granulocytic sarcoma.

In adults, cavernous hemangiomas are the most common de novo orbital tumefaction. CT scan reveals a round, encapsulated, well-defined orbital lesion. Histologically, large blood-filled, endothelial-lined spaces with fibrous interstitial tissue and smooth muscle are discerned. These lesions usually are well tolerated by the patient and managed by conservative therapy and reassurance, unless visual acuity or field loss is found.

Pathophysiology

Orbital tumefactions increase intraocular volume and cause a mass affect. Although a mass may be histologically benign, it can encroach on intraorbital or adjacent orbital structures and be considered anatomically or positionally malignant. Visual acuity or field compromise, diplopia, extraocular motility disturbances, or pupillary abnormalities can result from invasion or compression of intraorbital contents secondary to solid tumor or hemorrhage. Lid dysfunction and lagophthalmos or lacrimal gland dysfunction can result in exposure keratopathy, keratitis, and thinning of the cornea.

Presentation

Evaluation of the patient with a presumed orbital mass begins with a thorough ophthalmic and medical history. When concomitant sinus disease or an intranasal source is suspected, a speculum or endoscopic intranasal examination is warranted. Special emphasis on the duration and rate of progression of the patient's signs and symptoms is essential. Pain, diplopia, pulsation, change in effect or size with position or Valsalva maneuver, and disturbance of visual acuity are symptoms that should be explored. Past trauma and family history also may aid in the diagnosis. [12]

A complete ophthalmic examination is warranted. Periorbital changes can be noted easily on gross examination in a well-illuminated examination room. Hypertelorism, exorbitism, eyeball protrusion (proptosis), eyelid lesions or edema, chemosis, and engorged conjunctival vessels are several periorbital signs. Blepharoptosis, lagophthalmos (incomplete lid closure), and interpalpebral fissure distance are additional signs to be considered during the examination.

Protrusion of the eye is an important clinical manifestation of orbital disease. This ocular prominence is referred to as proptosis or exophthalmos. Henderson has suggested reserving exophthalmos to describe orbital manifestations of endocrinopathies. As recommended by Henderson, proptosis will be used to describe the change in anteroposterior axis of the eye as a result of orbital masses. In addition to proptosis, one should note the displacement of the eye in planes other than the anteroposterior dimension (eg, downward and lateral). Hertel exophthalmometry is a well-accepted tool to quantitate proptosis. Its use requires intact lateral orbital rims. If the rim is not intact, a Luedde exophthalmometer can be used. Relative protrusion can be observed by simply standing behind a seated patient and gazing downward toward the chin from the forehead to assess the displacement of one globe compared to the contralateral side.

Palpation of the anterior orbit can assess the level of tenderness, texture, and mobility of the mass. Tenderness may denote an inflammatory process or neural invasion by a neoplasm, such as adenoid cystic carcinoma of the lacrimal gland. Attention also should be paid to regional lymph nodes. Tactile inspection of the globe may reveal pulsations secondary to arteriovenous communications or physiological intracranially pulsations transmitted through a bony defect of the orbit, such as an encephalocele.

Auscultation of the orbit may detect a high flow state in the orbit or intracranially. The bell is useful for this examination. If a high-flow lesion is suspected (eg, carotid cavernous fistula), arteriography should be sought to further qualify these lesions. It is important to have the contralateral eye remain fixated on a target while auscultating the orbit.

Decreased visual acuity, change of refraction, and pupillary abnormalities should be noted. Extraocular motility dysfunction and diplopia should be carefully assessed and documented. Forced duction testing may qualify the dysfunction as restrictive or neurogenic in nature. Intraocular pressure may be elevated, and slit lamp examination can discern chemosis, engorged, or sentinel vessels. Dilated funduscopic examination may reveal optic disc edema or pallor, retinal detachment, choroidal folds, vascular engorgement or shunt vessels, or indentation of the posterior pole.

Indications

Initiation of surgical intervention occurs when confirmatory biopsy is needed or when the lesion is directly or indirectly adversely affecting the globe or the vision. In a patient with a salmon-patch colored lesion, confirmatory biopsies are needed to aid in the diagnosis and subtyping of the presumed lymphomatous lesion. Other lesions exert their destructive effects through their bulk, and diminishing these lesions is essential in restoring orbital integrity. In other situations, compression of the optic nerve requires decompression of the orbital contents.

Relevant Anatomy

The anatomical localization of orbital neoplasia is referenced with regard to the bony walls comprising it and vital structures, which travel within or in close proximity to these walls.

From an osteological standpoint, the orbit is composed of 4 bony walls that are the sum total of contributions from 7 bones.

The adult orbital floor has contributions from the maxillary, zygomatic, and palatine bones. It is the shortest of all the walls, not reaching the orbital apex, measuring 35-40 mm, and terminating at the posterior edge of the maxillary sinus. The infraorbital groove, canal, and foramen are contiguous, tunneling through the maxilla, and entombing the maxillary branch of the trigeminal nerve. The maxillary branch of cranial nerve V (V2) exits as the infraorbital nerve provides sensory innervations to the floor, mid face, and posterior upper gingiva in an ipsilateral fashion.

The lamina papyracea of the ethmoid bone, lacrimal bone, maxillary bone, and greater wing of sphenoid bone conjoin to form the adult medial orbital wall. The medial wall ending at the optic foramen serves as a barrier between the ethmoid air cell complex and the orbit. The most anterior bone, the lacrimal bone, forms the posterior one half of the lacrimal sac fossa. The anterior and posterior ethmoid foramina found in the superomedial orbit along the frontoethmoid suture line envelop branches of the nasociliary nerve and ophthalmic artery en route to the nose and ethmoid air cells. The former usually is identified 20-25 mm posterior to anterior lacrimal crest, while the latter is 30-35 mm behind the anterior lacrimal crest. If one identifies the posterior foramen, keep in mind that the optic canal is not much farther posterior and that the cribriform plate is looming about superiorly and must not be insulted.

Projecting in a posterior and inferior fashion, the orbital roof comes to an end at the superior orbital fissure and optic canal. Comprised of the frontal bone and lesser wing of the sphenoid bone, the orbital roof isolates the orbit from the frontal sinus and the anterior cranial fossa. The supraorbital notch, occasionally found to be a foramen, serves as a conduit for the supratrochlear nerve, which is an end branch of the frontal nerve. The ophthalmic division of the trigeminal nerve (V1) gives rise to frontal, nasociliary, and lacrimal nerves when dividing in the cavernous sinus. Orbital lesions or surgical intervention in the superomedial region of the orbit can cause lesions of this neural network. In addition, the lacrimal gland and trochlear fossae are found within the roof.

Within the confines of the superior and inferior orbital fissure is the lateral orbital wall. This prominent orbital structure receives bony contributions from the greater wing of the sphenoid bone and the zygoma. The lateral orbital tubercle of Whitnall is a bony protuberance serving as an anchoring site for the lateral canthal tendon. The zygomatic artery and nerve, an offshoot of the lacrimal artery and nerve, respectively, exit the zygomatic foramen.

The lacrimal gland is situated in the superolateral, anterior orbit. It is comprised of the palpebral and orbital lobes consisting of lacrimal, lymphoid, and epithelial tissues. One half of neoplasia that afflict this gland are malignant. Of these malignant lesions, 50% are of epithelial ancestry and 50% are lymphomatoid in origin.

Contraindications

Patients with complex medical histories should undergo thorough preoperative assessment by a medical specialist. Anticoagulative medications must be discontinued at an appropriate time prior to the surgical procedure to prevent excessive or uncontrolled intraoperative hemorrhage. If these medications cannot be stopped, a risk-benefit analysis must be contemplated.



Laboratory Studies

Laboratory testing should be directed by the clinician's suspicion level of the presumed etiology of the lesion. For example, lymphatic tumors require blood cell counts, imaging studies, and bone marrow evaluation. Often, the diagnosis is made following orbital biopsy or after removal of the lesion. In these scenarios, laboratory studies are predicated by the histopathologic findings.

Imaging Studies

The structural complexities of the orbit and its content present an imaging challenge. Strides in radiologic modalities have allowed the clinician to obtain detailed and logistic information about orbital tumors. [13]

Before the advent of computerized tomography (CT) scans, roentgenography was the imaging modality most commonly used to evaluate suspected orbital masses. Since roentgenography allows for only a 1-dimensional view and poorly defines soft tissue structures, CT scan has become the mainstay of orbital imaging.

CT scan, first used in the 1970s, is the product of tissue density calculations. X-rays with different vectors are emitted, penetrating through target tissues with resulting radioabsorbencies. These differences in radioabsorbencies are assigned value-specific gray shades to create the 2-dimensional image. CT scan can produce detailed axial and coronal views of soft tissue and bony structures. Image windows from 1-3 mm in thickness allow for detailed evaluation of orbital masses. Contrast-enhanced images may be obtained and can help identify inflammatory processes, vascular tumors, and engorged vessels. Calcified lesions are discernible without the addition of contrast. See the image below.

Axial CT scan revealing lateral orbital neoplasm. Axial CT scan revealing lateral orbital neoplasm.

Magnetic resonance imaging (MRI) excites protons by applying a radio frequency with a strong magnetic field. Hydrogen nuclei emit signal intensities that are assigned specific gray tones to create an anatomical reproduction. Three-dimensional views can be gained, directly, in any anatomical plane offering excellent spatial resolution of orbital masses and soft-tissue enhancement. MRI may provide excellent soft-tissue resolution, but CT scan is superior for gleaning details about orbital bony structures.

Coronal MRI showing left orbital cavernous hemangiCoronal MRI showing left orbital cavernous hemangioma.

Ocular ultrasonography can be used to visualize anterior and middle orbital lesions. Sound waves of 5-15 MHz breech orbital tissues that reflect echogenic energy captured by an oscilloscope. A-scan ultrasonography allows for a 1-dimensional description of echoes, while B-scan ultrasonography provides a 2-dimensional image. C-scan ultrasonography affords coronal views, and D-scan ultrasonography creates 3-dimensional orbital views. With the advent of CT scan, C and D ultrasonography remain unpopular. Doppler ultrasonography may be used to evaluate orbital vasculature and blood flow.

Diagnostic Procedures

Fine needle aspiration biopsy (FNAB) is a technique used for diagnosing orbital lesions. This outpatient procedure allows for retrieval of a cytological specimen through a well-controlled and minimally invasive surgical technique. In experienced surgical hands, FNAB can differentiate benign from malignant lesions with an accuracy of 95%. FNAB coupled with clinical and radiological finding can lead to a proper diagnosis in 80% of cases. Disadvantages include poor cellular yield, cytopathologic and not a histological diagnosis, difficulty in interpreting the specimen, and inadequate cellular yields requiring another biopsy procedure. Potential complications include retrobulbar hemorrhage, globe perforation, ptosis, extraocular motility dysfunction, and inadvertent entry intracranially. Patients with cystic lesions should not undergo FNAB.

Open biopsy of an orbital tumor is the common method of obtaining tissue from the orbital lesion. It also may be necessary if FNAB is not able to obtain adequate tissue for pathological assessment. An advantage of the open biopsy is the establishment of a histological diagnosis because enough of a specimen usually is obtained. Disadvantages include the associated morbidity and costs associated with this procedure.

Other Tests

Genetic analysis of tumors has aided in tumor identification. [14]

Staging

The TNM guideline advocated by the American Joint Committee on Cancer (AJCC) [15is used to stage cancers of the orbit. The "T" relates to tumor characteristics and size, "N" denotes status of the lymph nodes in the regional area, and "M" stands for metastases. These components result in an overall "stage" that ranges from 0 to IV. [1617]

The two most employed stages are a clinic stage and a pathologic stage, the latter being based on the tissue itself.


Medical Therapy

Medical therapy is tailored to the diagnosis obtained by biopsy or excision. Certain situations do not require a biopsy or excision to initiate treatment. Conditions such as orbital cellulitis often are treated medically with various antimicrobial agents. Surgical intervention is warranted if there is no response to treatment or clinical worsening is evident on examination. Orbital inflammatory disease (pseudotumor) usually is treated medically with systemic steroids. Capillary hemangiomas also can be treated with nonsurgical modalities, such as steroid injections.

Surgical Therapy

With little wasted space and a lexicon of anatomical structures occupying the orbit, surgical intervention remains a challenge. Maximal operative exposure of the lesion with ginger and minimal manipulation of the orbital contents must be well-orchestrated for successful surgical outcomes. Advances in computer-assisted imaging devices are facilitating the operative experience, but widespread utilization is limited. [18]

Many cutaneous and bony approaches to the orbit have been described. The surgical approach used is reliant upon the location and size of the tumor with the surgeon's skill and experience lending itself to the choice of surgical entry into the orbit. This discussion is not meant to be a comprehensive tome on orbital surgery but merely an overview of commonly described orbitotomies.

Positions that minimize an increase in intraorbital (venous) pressure are preferred during the surgical procedure. This can be accomplished with the reverse Trendelenburg position and hypotensive anesthesia to the degree that it can be tolerated medically. Orbitotomies often are described by their anatomical location or in relation to the anatomy they transgress. Approaches can be from the periocular skin or more remote locations elsewhere on the face and scalp. Additional approaches can emanate from the conjunctival plane. Intracranial approaches also can be used.

The location of the lesion directs the surgeon toward selecting the most appropriate type and location of the orbitotomy. Concerns over the facility of using a given approach and ultimately the postoperative cosmetic appearance are considerations that assume variably weighted significance in any given situation. Indubitably, if equivalent approaches are feasible, that which produces the more appealing cosmetic result most often is preferred.

Anterior orbitotomy most commonly is performed transcutaneously or transconjunctivally. Often, the transconjunctival approach denotes an incision in the vicinity of the inferior forniceal area of the lower lid with or without a canthotomy and/or cantholysis. However, in the broadest sense, it encompasses transcaruncular and transbulbar conjunctival approaches with or without the release of the recti muscles. An example of such an approach is the medial orbitotomy via the medial bulbar conjunctiva with release and then reattachment of the medial rectus. For medially located lesions, such as those encroaching on the nasal orbital apex, this approach is possible. The optic nerve also can be reached from this approach.

Those lesions located superiorly are delimited further by their medial to lateral and anterior to posterior localization. Most often, a supertemporal lesion is from the lacrimal gland and a lateral orbitotomy or one of its modifications is an acceptable approach. Those lesions more centrally located and those in a superonasal orientation can be approached from a Lynch-type incision.

Alternatively, a coronal dissection can be used. In more posteriorly situated superior lesions, an intracranial approach may be warranted. In certain cases, medial and lateral approaches can be combined to access this area.

Inferiorly, the orbital lesion is approachable from a transconjunctival or a transcutaneous approach. In either situation, it may be required to perform a canthotomy and cantholysis to achieve adequate exposure. If the contiguous maxillary sinus is involved a Caldwell-Luc approach also can be used.

Laterally located lesions are approached from a lateral orbitotomy, such as the Berke, Reese, Stallard, or Wright approach.

Transnasal, transantral, and transethmoidal endoscopic approaches are being used more frequently to gain access to orbital lesions. [19]

Left lateral lid crease incision to access the supLeft lateral lid crease incision to access the superolateral orbit.

Transcranial approaches can be used for tumors involving the orbital-cranial regions. [20. Skull-based tumors can also be approached via a transorbital approach. [21]

An interesting approach referred to as "round-the-clock" overlays a clock face on the orbit centered on the optic nerve. From this perspective, different approaches are used for certain clock hours. As an example, for the right medial orbit involving clock hours from 1 to 6, a medial transconjunctival approach is useful. Alternatively, an endonasal endoscopic approach can give access to the orbit at the apex, as well as to the mid and posterior orbit for clock hours 1 to 7. [22]

Core needle biopsy (CNB) of orbital tumors has been used with and without ultrasound guidance, as well as CT guidance. [2324]

Three-dimensional (3D) imaging can also be used in determining the approach to the tumor. [25]

Preoperative Details

A systematic review and documentation of the patient's medical status is essential.

A thorough explanation of the procedure and the risks, benefits, and alternatives should be clearly explained and documented. The patient should be cognizant of the exact procedure and if a biopsy will be performed on the mass or if an attempt for total excision will be made. It is imperative that the patient be informed of the possibility of enucleation or exenteration if indicated.

Preoperative documentation of visual acuity, degree of ptosis, lagophthalmos, proptosis, pupillary and extraocular muscle function, and the amount of diplopia in all fields of gaze is necessary. External photos are strongly suggested for documentation and later review.

A meticulous review of imaging with a neuroradiologist, if necessary, is essential for planning the surgical approach and identifying the mass and impingement of surrounding orbital structures.

Intraoperative Details

During surgical intervention, periodic assessment of pupillary function is prudent. Assessing the pupil size prior to general anesthesia, after general anesthesia is induced, and after any periorbital injections containing epinephrine (prior to manipulating the globe) is worthwhile. Narcotics can cause pupillary constriction (miosis), and epinephrine can cause pupillary dilation (mydriasis). If not assessed before the orbital manipulation is undertaken, assessment as to the cause of a dilated pupil can be obscured when the pupil is checked during surgery.

Intraoperative manipulation of the globe must be adequate to allow for sufficient exposure of the operative site, yet manipulation must be gentle enough not to put undue pressure on the globe compromising vascular flow.

Extraocular muscle manipulation can trigger the oculocardiac reflex, with resultant bradycardia. The anesthesia staff should be aware of any extraocular muscle manipulation, so that the patient's heart rate can be assessed.

Bipolar cautery is preferred to avoid channeling of the current and injury to the optic nerve.

Postoperative Details

Postoperatively, the patient must be assessed with regard to vision, bleeding, and pain.

Visual insult could occur in the intraoperative period and must be assessed postoperatively at 15-minute intervals for the first hour following surgery and every 30 minutes in the second hour. Additionally, pupillary and extraocular muscle function should be evaluated in the postoperative period.

Hemorrhage can occur in the orbit and may be potentially blinding and must be scrutinized for.

Pain may be variable, but if nausea and vomiting occurs as a result of pain medications or surgery, treatment must be given to avoid this and decrease venous pressure. Increased venous pressure can cause orbital congestion and lead to compression of the optic nerve.

Follow-up

The patient is examined the day after surgery. Vision, extraocular motility, and pupillary function are evaluated and any dressing changes are performed. In sighted patients, the authors do not patch the eye for fear that a hemorrhage would remain unrecognized and result in increased orbital pressure, with resultant compromise of an essential intraorbital structure.

Complications

The most feared complication in orbital tumor surgery is loss of vision. This can be due to excess pressure with retraction the globe. Compression of the central retinal artery can lead to irrevocable blindness.

Hemorrhage can occur operatively and postoperatively with resultant compression of the optic nerve and occlusion of the central retinal artery. Hemorrhage also can occur from laceration of the anterior or posterior ethmoidal arteries.

Monopolar cauterization should be used sparingly in the orbit because the current can channel through the optic nerve and lead to visual loss.

Because of the close proximity to the anterior cranial fossa, inadvertent intracranial injury can result.

Direct perforation of the globe is possible, especially if adequate protection, such as a corneoscleral shield, is not used.

Diplopia or other extraocular muscle disturbances can be the result of neurologic or direct muscular injury.

Paresthesia is a potential complication if there is injury to the infraorbital, supraorbital, or supratrochlear nerves.

Outcome and Prognosis

The outcome and prognosis ultimately depend on the pathological diagnosis.

Future and Controversies

Improved diagnostic modalities will enhance the ability of diagnosing orbital tumors. Stereotactic computer-guided imaging can help localize posterior lesions. Positron emission tomography (PET) is being investigated to identify the metabolic activity of orbital tumors. [26. Gene therapy is showing promise in a multitude of cancers, and this "precision medicine" is being researched for treatment in orbital cancers such as lymphoma. 


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