Open Management of Primary Orbital Neoplasms

Patient Selection and Indications

Adults with orbital masses will be found to harbor a malignant tumor in about one-third of cases 1,​ 2 In children, the incidence of malignancy is a bit lower, about one in four. 3 The most frequently encountered type of tumor is vasculogenic, with cavernous hemangioma and lymphangioma (lymphovenous malformation) representing the majority of these. Cavernomas are recognizable by their smooth exterior, (sometimes late) contrast enhancement, and slow growth. These should be resected when the risk–benefit ratio is favorable, as many can be observed. Lymphovenous malformations are very low flow lesions that often have multiple cysts and a bright appearance on T2-weighted magnetic resonance imaging (MRI) sequences. These are not generally amenable to resection and should be sent for sclerotherapy or embolization. In the event of an acute bleed into a lymphovenous malformation with severe pain or optic neuropathy, these may be decompressed from an anterior approach by aspiration. Even in adults, dermoid cysts are the most commonly encountered cystic mass. These should be excised intact, but computed tomography (CT) is necessary to evaluate the adjacent bone for defect, either with extension of the cyst or with encephalocele.

Other common primary orbital malignancies include lymphoma, sarcoma, and lacrimal gland malignancies. 4 In several series, lymphoid neoplasms comprise about 10% of orbital space occupying lesions and about half of lacrimal gland masses. Incisional biopsy is indicted in many cases, but care should be taken preoperatively to characterize lacrimal gland lesions, as some should be excised in toto (benign mixed tumor/pleomorphic adenoma). The tissue should be sent both in formalin and fresh for possible cell sorting, and the receiving lab should be notified of the surgeon’s clinical suspicion. Metastatic masses in adults represent about 3% of all orbital masses, and breast, prostate, and lung are the most common of these. Bilateral orbital masses suggest systemic disorders or metastasis.

13.3 Diagnostic Workup

The most common presenting complaints of a patient with an orbital mass will be proptosis (increased projection of the eye) and double vision. Others may include pain, dryness or irritation of the eye, or tearing. Decreased vision is often a late symptom or sign.

The patient’s medical and surgical history, particularly regarding autoimmune disorders and malignancies, must be first discussed. Medications, with attention to anticoagulants, must be assessed. A complete physical examination of the orbit, preferably by an ophthalmologist experienced in orbit surgery, must be performed, including documentation of visual function, proptosis, strabismus, and examination of the posterior segment of the eye. If indicated, an examination of the head and neck with particular attention to the nose, paranasal sinuses, and lymph nodes, should be performed. Nasal or sinus endoscopy may be indicated.

The first radiologic study in a patient’s workup is usually CT of the orbits. CT is helpful in delineating the size and location of the lesion and is also important for assessing whether and how the bone is involved in the pathologic process. There may be bony deformity or expansion, frank destruction, or no bony change, which may be of significance in elucidating the diagnosis. When working up a likely orbital mass, intravenous (IV) contrast can be very helpful in its characterization. If the patient is allergic to contrast, pretreatment with antihistamine or corticosteroid may allow for contrast use. MRI of the orbits with and without contrast is very helpful in delineating soft-tissue detail. Even without contrast, the orbital fat acts as natural contrast for the other orbital structures, so it is important to look at both fat-suppressed and non-fat-suppressed images. Additional radiologic considerations may be found in Chapter 3.

In patients with suspected malignancy (infiltrative or destructive mass, bilateral orbital tumors, lymphadenopathy) or history of cancer, a thorough evaluation for a primary tumor and metastases should be performed. Options include CT scans of the neck, chest, and abdomen, or positron emission tomography (PET). Serum markers associated with any known primary tumors may also be helpful.

13.4 Surgical Anatomy

For neoplasms in the anterior half of the orbit (anterior to the equator of the eye, where the extraocular muscles insert), an anterior approach is appropriate. For pathology farther posterior, some osteotomy will likely be required. Though it is attractive to approach posterior pathology without bone removal, orbital fat and other soft tissues obscure the view and must be retracted deep in the orbit, greatly narrowing the corridor. As depicted in ▶ Fig. 13.1, the medial and inferomedial posterior orbit are amenable to endoscopic approaches. The inferolateral, lateral, and superior portions of the orbit require either a lateral orbitotomy or a supraorbital craniotomy for good access.

Clock model of the orbit summarizing how the different approaches fit together and overlap. ON, optic nerve.

Fig. 13.1 Clock model of the orbit summarizing how the different approaches fit together and overlap. 5 ON, optic nerve.

The lateral orbitotomy as originally described by Kronlein 6 is the workhorse approach for pathology of the lacrimal gland, the lateral and inferior intraconal spaces, and some limited pathology in the superior orbit. This is performed through a crow’s foot incision, which is cosmetically pleasing and safe for the temporal branches of the facial nerve, which pass at least 2.4 cm posterior to the bony lateral canthus at the midpupil level. The inferior extent of the osteotomy in this approach will be at the zygomatic arch. The zygomaticofacial neurovascular bundle (sensory only) emerges on the lateral surface of the zygoma superior to the arch. When operating intraconally in this area, it is important to remember that the ciliary ganglion lies between the lateral rectus muscle and the optic nerve, about 1 cm posterior to the globe, and may be quite diaphanous in some patients ( ▶ Fig. 13.2).

(a) Anterior view: opening in the right orbit for neurovascular structures. (b) Posterior wall of the orbit: common tendinous ring and sites of passage of neurovascular structures through the optic ca

Fig. 13.2 (a) Anterior view: opening in the right orbit for neurovascular structures. (b) Posterior wall of the orbit: common tendinous ring and sites of passage of neurovascular structures through the optic canal and superior orbital fissure—right orbit, anterior view with most of the orbital contents removed. (Used with permission from Schuenke et. al. Theime Atlas of Anatomy 1st ed. New York, NY: Thieme 2007.)

To reach the posterosuperior orbit, a traditional supraorbital craniotomy using a hemicoronal or pterional incision is generally done. It is important to dissect the temporalis muscle planes carefully, and perform an interfascial dissection to spare the motor branch to the frontalis muscle. The supraorbital notch (or foramen) often marks the lateral-most extent of the frontal sinus and generally provides more than adequate access to the orbital roof. The extent of the sinus should be considered when planning the craniotomy, and image guidance is often used for this purpose in addition to lesion localization; avoidance makes the reconstruction simpler and less likely to become infected. The supraorbital neurovascular bundle should be identified and preserved as much as possible during this approach. In addition to a standard supraorbital craniotomy, an “eyebrow approach” or supraorbital keyhole craniotomy can provide very similar access, though with limited frontal lobe retraction.

When approaching pathology in the medial orbit, such as with a transcaruncular approach, care must be taken to understand the relationship of the lacrimal drainage system to the incision. When opening conjunctiva and dissecting to the posterior lacrimal crest, the lacrimal drainage system stays safely anterior. The inferior oblique muscle arises from the periosteum of the maxilla just lateral to the entrance of the nasolacrimal duct. This should not be transected, but may be elevated by dissecting in a subperiosteal plane at its origin. Likewise, the trochlea, which should be mobilized by elevating it along with underlying periosteum from the bone, will be found just inside the orbital rim at the superomedial corner of the orbit. Neither muscle need be sutured back or fixated in any way when reconstructing. The anterior ethmoidal artery will be found at the level of the frontoethmoidal suture about 2.5 cm posterior to the anterior lacrimal crest in the adult orbit, and may be cauterized with bipolar electrocautery and divided if necessary. The posterior ethmoidal artery will be found about 1 cm posterior to this and may be treated in the same manner. The optic canal may then be less than 0.5 cm away and great care must be exercised.

13.5 Surgical Technique

13.5.1 Lateral Orbitotomy

The patient is positioned supine and the area from above the brow, back to the hairline, and down to the nasal ala is prepped and draped. The lateral canthus is injected with local anesthetic with epinephrine, if desired. A corneal protective lens lubricated with ointment may be sutured to the eyelids. A tenotomy scissors is used to carefully perform a lateral canthotomy. This is extended posteriorly for about 2 cm. An inferior cantholysis (and limited superior cantholysis) is performed by distracting the lid with forceps, strumming across the deep tissue between conjunctiva and skin (actually the orbital septum), and cutting along the rim until the lid is very loose.

Blunt retractors are used to hold skin edges and a malleable retractor is placed just inside the orbital rim to protect the orbital contents. Needle-tip electrocautery on low power is used to score periosteum in a superoinferior direction on the anterior surface of the orbital rim, as far superiorly as the zygomaticofrontal (ZF) suture, and as far inferiorly as the zygomatic arch. Dissection of the periosteum from the exterior surface of the rim is performed with an elevator such as a Penfield 1 or Cottle. The zygomaticofacial and zygomaticotemporal vessels should be cauterized and divided. Temporalis muscle should be peeled away from the external surface of the wall with cautery, as there is not a good subperiosteal plane. A relaxing incision in the periosteum parallel to the skin incision will make the dissection and the reconstruction easier. Dissection of the periorbita from the interior surface of the lateral wall now proceeds, keeping the periorbita as intact as possible.

A wide malleable is now placed between periorbita and bone, and the skin edge is retracted carefully so that a reciprocating saw can make two anteroposterior cuts in the lateral rim, one just superior to the zygomatic arch and one just superior to the ZF suture. The inferior cut ends in the inferior orbital fissure. A rongeur placed at the lateral canthus now outfractures the wall and this bone is removed after clearing remaining temporalis muscle from its exterior surface with electrocautery. If the wall is too thick to fracture easily, a vertical groove may be drilled with a small drill bit such as an M8. This bone is kept safely in saline for later replacement. A rongeur or drill may be used to drill the sphenoid bone posteriorly until adequate exposure is obtained.

When opening periorbita, the incision should be made in an anteroposterior direction if possible, to avoid injury to the lateral rectus muscle. Resection of tumor and hemostasis are undertaken ( ▶ Fig. 13.3 and ▶ Fig. 13.4).

(a) Axial T1-weighted magnetic resonance imaging (MRI) with contrast showing typical patchy contrast enhancement and smooth external contour of orbital cavernous hemangioma. (b) Coronal T1-weighted MR

Fig. 13.3 (a) Axial T1-weighted magnetic resonance imaging (MRI) with contrast showing typical patchy contrast enhancement and smooth external contour of orbital cavernous hemangioma. (b) Coronal T1-weighted MRI with contrast of lesion in (a) showing intraconal location and later more intense uptake of contrast.

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Feb 25, 2020 | Posted by in OTOLARYNGOLOGY | Comments Off on Open Management of Primary Orbital Neoplasms

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