Endoscopic-Assisted Orbital Exenteration
Malignant diseases involving the orbit can result in an incalculable amount of human suffering, as their natural course can progress to include bleeding, pain, disfigurement, blindness, and premature death ( Fig. 29.1 ). Orbital exenteration to treat such a malady, whether performed by open surgery or endoscopically, is challenging and is best accomplished through a multidisciplinary approach. The recommendation to exenterate the orbital content is typically based on two critical considerations: (1) will it lengthen life? and/or (2) will it maintain or improve quality of life? The recommendation to exenterate is made more difficult by the lack of controlled studies or even consensus as to when it is absolutely indicated. Regardless of whether orbital exenteration is best performed through a traditional approach or is endoscopically assisted is based on the disease being treated and the experience of the surgeon. Open orbital exenteration is most commonly performed for malignancy arising from within the orbit and its adnexa. Endoscopic-assisted orbital exenteration (EAOE) is typically used for orbital disease arising within the nasal and sinus passages.
Traditionally orbital exenteration describes removal of all orbital contents, including the globe, eyelids, conjunctiva, and periorbital structures. However, based on the nature, extent, and location of the disease being treated, the exenteration may be subtotal (eyelids left intact) or extended (removal of adjacent bony structures). At the conclusion of the traditional exenteration, substantial frontal, sphenoid, and/or zygomatic bone is typically left exposed within the exenteration cavity. The average length of time for an exenteration cavity to heal by secondary intention is estimated to be 5 months. In the case of cancer, without immediate reconstruction with split-thickness skin graft, regional tissue transfer, or myocutaneous free flaps, there will be an unacceptable delay in the initiation of postoperative radiation. EAOE, however, represents an alternative approach that permits preservation of the superior and lateral periosteum/periorbita that can greatly facilitate wound healing.
EAOE, introduced by Batra and Lanza in 2005, evolved from experiences with endoscopic dacryocystorhinostomy and endoscopic decompressions of the orbit and the optic nerve. The endoscopic approach offers improvements in visualization and facilitates a more natural transition from the sinonasal portion of the procedure to the orbital exenteration. It allows for better assessment of tissues at the sino-orbital interface if the final decision to exenterate is made intraoperatively. This approach can facilitate postresection mapping to obtain clean margins. EAOE expedites the removal of orbital adnexa, such as the fat, extraocular muscles, lacrimal gland, sac, duct, vessels, and nerves, by using a soft-tissue shaver (microdebrider). Endoscopic resection readily permits eyelid and brow preservation. It is important to note that during EAOE, the globe and distal optic nerve are removed intact, anteriorly through the palpebral fissure. This precludes any risk of contralateral blindness secondary to sympathetic ophthalmia. Despite its advantages, the place of EAOE in our surgical armamentarium is yet to be clearly delineated.
Examining Indications for Endoscopic-Assisted Orbital Exenteration
The indications for EAOE resemble those for traditional exenteration and can include cancer, infections, trauma, inflammatory disorders, and even massive expanding benign tumors. Yet, in most circumstances, there are immediate alternatives to exenteration. However, once the extraocular muscles, intraconal fat ( Fig. 29.2 A ), and/or the globe are involved by destructive disease arising within the paranasal sinuses, aggressive therapy is warranted. However, involvement of the lamina papryacea, lacrimal bone, maxillary bone, or even the periorbita is no longer considered by many treating physicians as absolute indications for orbital exenteration. Accurately determining which of these tissues are directly involved by malignancy can be difficult to ascertain by preoperative imaging even with magnetic resonance imaging (MRI). Surrounding tissue edema secondary to the cancer may be mistaken on imaging for extraocular muscle invasion ( Fig. 29.2 B). Therefore the final determination on critical orbital involvement may be delayed based on intraoperative tissue sampling/pathology results.
In the case of acute invasive fungal sinusitis, orbital exenteration might be delayed until antifungal therapy, reversal of immune dysfunction, and endoscopic sinus surgery can be given a chance to be effective. Topical or injected intraorbital amphotericin B might also be used. Limited treatment without exenteration is more likely to be effective in those patients whose immune deficit can be reversed and/or when mucormycosis is not the infection invading tissue. However, in the case of severe immunosuppression with fulminant mucormycosis tissue invasion, EAOE performed with early signs of involvement is known to be lifesaving.
In the case of sinus malignancy, it is widely accepted that invasion of orbital contents through the periorbita heralds a poorer prognosis for overall and disease-free survival. The standard of care is a combination of surgery with adjuvant radiation therapy with or without chemotherapy. However, whether orbital exenteration improves disease-free survival or overall survival is unclear. This lack of clarity makes the choice to exenterate an orbit for sinus malignancy especially difficult. Moreover, the existing data for sinus malignancy examine traditional orbital exenteration, but similar data are not available for EAOE. Yet early results for endoscopic management of sinus malignancy yield comparable results to open surgery. Endoscopic resection of sinus malignancy alone or in combination with EAOE may be delayed or avoided depending on the malignancy type, extent of involvement, the patient’s choice for neoadjuvant chemotherapy and/or radiation, and patient motivation to preserve the eye.
In one study, induction chemotherapy was successful in down-staging sinus cancer, leading to orbital preservation in 82% of patients. However, nearly 20% did not respond adequately to therapy, potentially jeopardizing those lives to preserve an orbit. In another study, treatment of basal cell carcinoma invading the orbit with an oral hedgehog pathway inhibitor called vismodegib (Erivedge) has prevented blindness and preserved the orbit in select cases. Adding to the controversy is an international collaborative report of 334 patients with ethmoid malignancies who underwent craniofacial resection with and without radiation/chemotherapy. This report indicates that orbital involvement reduces 5 year disease-specific survival from 78.0% to 44.4%. Unfortunately, there is insufficient evidence from even this large study to determine whether orbital exenteration yields a better 5-year survival rate. The survival impact of orbital exenteration, from a series with the most promising results, is 93.4% at 1 year and 53.1% at 5 years. Lastly, orbital invasion by cancer is associated with inferior outcomes even from salvage surgery.
Preoperative surgical planning requires careful review of computed tomography and MRI to assess the extent of sinonasal and orbital pathology. All patients undergo nasal endoscopy, typically with tissue sampling and preoperative ophthalmologic evaluation. Consultation with oncology, radiation oncology, the reconstructive team, neurosurgery, and/or maxillofacial prosthetic specialists is obtained when appropriate. Informed consent for orbital exenteration is obtained after frank discussion about limitations, risks, benefits, and alternatives. The patient’s psychological status is taken into consideration, as orbital exenteration surgery may have significant emotional repercussions.
Endoscopic-Assisted Orbital Exenteration: Surgical Technique
The operative suite is set up for computer-aided endoscopic sinus surgery, and the patient is prepared for general anesthesia with appropriate intravenous access, should blood transfusion be necessary. The face is prepped and draped with special protections afforded to the contralateral eye with corneal shield, lubricant, and/or temporary tarsorrhaphy suture. The ipsilateral eye may be similarly protected until the intraoperative decision to exenterate is finalized based on pathology findings. The intraoperative navigation system is properly positioned, registered, and its accuracy verified. Nasal decongestion is obtained with 0.05% oxymetazoline hydrochloride on cotton pledgets. Transnasal sphenopalatine and lateral nasal wall injections are performed with 1% lidocaine with 1:200,000 of epinephrine. Large sinonasal neoplasms may preclude sufficient intranasal injections; transoral greater palatine foramen block may be used in these circumstances. Bleeding is controlled with topical vasoconstrictors applied on <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='12′>1212
× 3-inch pledgets and unipolar suction cautery. Topical adrenaline, 1:1000 colored with fluorescein to prevent drug confusion (with injected medications), can be helpful when safely administered. Three 1 × 36-inch petroleum jelly–impregnated gauze packs are opened on the field should they be needed for brisk bleeding. The transnasal segment of the procedure is initiated first.
After endoscopic complete sphenoethmoidectomy, maxillary anstrostomy. and frontal sinusotomy are performed, disease extending beyond the sinuses, into the clivus, pterygoid plates, pterygomaxillary space, or infratemporal fossa is resected endoscopically. A wide sphenoidotomy and maxillary antrosomy facilitates the exposure of the orbital apex. The region of the medial orbit, inferior orbit, lacrimal sac, and optic nerve are exposed. Residual lamina papryacea is removed with a curette, Cottle elevator (Karl Storz, Germany), and/or drilled away with a concurrently irrigating diamond burr. Bone at the orbital apex is removed with the diamond burr to expose the annulus of Zinn. The involved portions of the lacrimal sac are removed endoscopically. Tissue sampling for pathology are sent for mapping of the disease. The periorbita is incised with 6700 and/or bent 7200 Beaver blade (BVI [Beaver-Visitec] International, Waltham, MA) to expose the orbital fat and muscles.
Angled instruments typically used in frontal sinus surgery as well as 30-degree and 70-degree telescopes are needed for this approach. Soft-tissue shavers (microdebriders) facilitate expeditious removal of the periorbital contents while the suction constantly clears blood from the surgical field. Extraocular muscles, orbital fat, lacrimal gland and pathology are very amenable to soft-tissue debridement with straight, 40-degree, 60-degree, 90-degree, and even 120-degree shaver tips (Medtronic Xomed, Jacksonville, FL). The orbit is skeletonized as the debulking proceeds from medial to lateral and inferior to superior. Removal of the lacrimal gland and inferior oblique muscle at its lateral attachment is typically performed with 70-degree endoscope and either a 90-degree or 120-degree soft-tissue shaver tip. Properly grounded unipolar suction cautery is used for bleeding control during soft tissue resection. Unipolar cautery is avoided at the orbital apex and on tissues adjacent to the dura. Again, with careful resection, the lateral and superior orbital periosteum can typically be preserved. Once the orbital adnexa are removed, the globe and optic nerve remain intact. The tough collagen of the episclera renders the globe somewhat impervious to inadvertent damage by the soft-tissue shaver. The cauterized extraocular muscle stumps with the origins at the annulus of Zinn remain visible. The optic nerve and ophthalmic artery are cross-clamped at the orbital apex using a long thin right-angle hemostat placed transnasally.
Exteriorly, using overhead lighting and magnified direct visualization, the globe is released by making relaxing incisions in the conjunctiva at the surgical limbus. The conjunctiva is elevated and preserved back toward the conjunctival fornix. The globe is mobilized medially and laterally by sharp release of the medial and lateral canthal tendons. A Wells enucleation spoon (Novo Surgical, Oak Brook, IL) ( Fig. 29.3 ) is placed behind the globe to provide traction during the endonasal transection of the optic nerve. Incision is made endoscopically proximal to the right angle hemostat at the orbital apex with a 7200 Beaver blade. The globe and optic nerve trunk are withdrawn with the Wells enucleation spoon through the palpebral fissure. While protecting the eyelids, the optic nerve /ophthalmic artery stump is tied with two 2-0 silk suture ligatures through the palpebral fissure into the exenteration cavity. Frozen sections can be obtained from the orbital apex and optic nerve to ensure adequate removal of disease. Bipolar cautery is used to control residual bleeding.