Surgical rehabilitation of Graves’ orbitopathy

Published on 08/03/2015 by admin

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CHAPTER 54 Surgical rehabilitation of Graves’ orbitopathy

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Introduction

Graves’ orbitopathy (GO) is one of the phenotypic appearances of Graves’ disease, a multisystem disorder which usually leads to hyperthyroidism and goiter, less frequently to GO, and rarely to pretibial myxedema and acropachy. GO is the most frequent and important extrathyroidal expression of Graves’ disease. It may also be found, although less frequently, in patients with no present or past history of hyperthyroidism (so-called euthyroid or ophthalmic Graves’ disease), or in patients who are hypothyroid due to chronic autoimmune (Hashimoto’s) thyroiditis1,2. In most affected individuals GO is mild and self-limiting, and only in 3–5% of cases is it severe and potentially sight threatening1,3.

The exact pathogenesis of GO is unknown47. It is, however, worth highlighting the clear-cut link between the orbit and the thyroid, because this has important clinical and therapeutic implications8. In addition to endogenous (non-preventable) determinants, such as genetics, age- and gender-related factors9, GO occurrence and progression are influenced by environmental (preventable) factors, such as cigarette smoking, thyroid dysfunction, and different treatments for hyperthyroidism3,10. This implies that control or correction of these risk factors is an integral part of GO management.

Independently of the complex association with thyroid dysfunction and its treatment, management of GO is difficult: decisions need to be made regarding the need for specific treatment or whether spontaneous regression is likely.

The natural history of GO is of gradual increase in severity followed by a plateau phase then gradual improvement11. These are the active phases. The inactive phase follows with no change in severity. GO is thus self-limiting, although it often does not return to baseline. Treatment is aimed at accelerating recovery, preventing serious sequelae, and eventually functional and cosmetic rehabilitation.

Therapeutic options consist of medical therapy, radiotherapy, surgery, or frequently a combination of these. Consensus as to indications and timing of these options has been reached by the EUGOGO consortium (Fig. 54.1)12,13.

Timing of surgery

Surgery may be necessary to protect visual function in the active phase or to correct the stable typical disfigurement and symptoms in the static post-inflammatory phase of the disease.

The first rehabilitative step mainly consists of orbital bony decompression. It causes reduction in exophthalmos as well as reduction in upper and lower eyelid displacement14. It may positively influence extraocular muscle restrictions, but displacement and scarring of the soft orbital tissues caused by decompression surgery may also cause strabismus. Possible squint surgery should therefore follow orbital decompressions, but considering that vertical tropias may influence eyelid position, squint surgery should precede possible eyelid corrections. Finally, when necessary, the finishing touch can be given by eyebrow lift, forehead plasty, and blepharoplasty.

In short, surgical rehabilitation needs to respect the given order since the preceding step may influence the necessity and the extent of the step that follows. When all the steps are necessary, the entire rehabilitation may require between 1.5 and 2 years. In particular cases, exceptions are possible and the rehabilitation can be favorably speeded up by carrying out more than one procedure at the same time15. The traditional management algorithm has not been respected in only a few series1620, and it has met with vigorous criticism21.

Orbital decompression

The autoimmune process at the basis of GO induces swelling of the soft tissues contained within the boundary of the bony orbit; this causes impairment of the venous outflux towards the cavernous sinus and reverses the flux in the direction of facial circulation.

This positive feedback circle leads to an increase in the intraorbital pressure, which is first responsible for the progression of GO and later for its typical signs and symptoms5. Any surgical procedure aimed at decreasing the raised intraorbital pressure and its effects by means of enlargement of the bony orbit and/or removal of the orbital fat is defined as orbital decompression.

Orbital decompression is currently indicated for the treatment of optic neuropathy refractory to medical therapy, exposure keratopathy unresponsive to local measures and/or minor eyelid surgeries, disfiguring exophthalmos and symptoms. Eyeball subluxation (which may be a possible cause of acute optic neuropathy and exposure keratopathy) postural visual obscuration in patients with congestive inactive GO and recently onset choroidal folds due to eyeball indentation by enlarged extraocular muscles represent other functional indications for decompression surgery22.

Osteotomies can involve the medial, and lateral orbital walls and the orbital floor (Fig. 54.2); lipectomies can be performed at the level of all the orbital quadrants (Fig. 54.3). Decompression surgery can be performed through several different surgical incisions (Fig. 54.4) preferably under general anesthesia.

The inferior fornix incision is an extremely popular approach to orbital decompression. It can be extended medially into a transcaruncular incision and can be associated with an incision at the lateral canthus that permits the lower lid to swing outwards, thus easing the exposure of the lateral wall. This latter association, first described by McCord in 1981, is known as ‘swinging eyelid’23. This combination of periorbital incision permits an easy approach to the orbital floor, medial, and lateral walls and lipectomies from the inferior orbital quadrants.

As an alternative, an upper skin crease incision can be used separately or in combination with the pure inferior fornix or with the swinging eyelid approach in order to address the lateral orbital wall through a wider exposure, and to have access to the upper fat compartments of the medial and lateral quadrants.

The coronal approach is a more invasive procedure which, however, offers the widest access to the lateral orbital wall24, and it may have distinctive advantages in a number of situations including the presence of remarkable periorbital swelling or conjunctival chemosis, the necessity of minimizing the number of periorbital incisions, or the necessity of extensive manipulation of the lateral wall (including its rim)25,26. Through a coronal incision, brow lift, and correction of frontal/glabellar rhytids, which are often necessary in patients with GO, can be performed simultaneously with orbital decompression, thus favorably speeding up the timing of rehabilitative surgery25,27.

Orbital decompression by transinferior fornix/transcaruncular/swinging eyelid: surgical technique

Step 1. After the exposure of the inferior fornix by means of a Desmarres retractor and a malleable orbital retractor, the conjunctiva and lower lid retractor complex are transected en bloc with a Colorado needle and the periorbit of the inferior orbital rim is exposed (Fig. 54.5A). During this step, and in all those which imply the use of a Colorado needle, the part of the retractors in contact with tissues should be rubber coated or isolated by means of sterile plasters in order to avoid unwanted burn to the eye, eyelids, and extraocular muscles.
Step 2. The exposed periorbit is incised and the orbital floor and the medial and orbital wall exposed by developing a subperiorbital plane (Fig. 54.5B,C). In order to obtain the best possible exposure of the medial wall, the bony insertion of the inferior oblique muscle may be detached without consequences, and if required the conjunctival incision extended upwards, laterally to the caruncle. A separate incision lateral to the caruncle (transcaruncular approach)28 can possibly be used to address the medial orbital wall when the floor is not to be removed.
Step 3. After this a Frazier suction tip is used to fracture the delicate bone of the medial orbital wall and the floor and Blakesley forceps no. 1 and no. 2 are used to remove bony fragments and mucosa of the sinuses (Fig. 54.5D). The inferomedial osteotomy extends between the frontoethmoidal suture (orbital landmark of the inferior limit of the anterior cranial fossa) and the inferior orbital fissure. The bulla ethmoidalis is opened towards the orbit from the posterior lacrimal crest up to the orbital apex, and then the orbital floor medial to the infraorbital canal is removed from about 1 cm behind the inferior orbital rim up to the posterior wall of the maxillary sinus. The bony infraorbital canal, the floor lateral to it (Fig. 54.5E), and the posterior two-thirds of the maxillary ethmoidal strut can also be removed. The anterior one-third of the strut should be left intact in order to prevent globe displacement and the possibility of medial entropion.
Step 4. In order to implement the effect of decompression fat can be removed from the medial and lateral inferior quadrants (Fig. 54.6). An adequate exposure attained by the assistant, by means of electrically insulated Desmarres retractor and different sized malleable orbital spatulas, aids the surgeon to perform the lipectomy by exerting gentle traction on the fat with fine toothed forceps simultaneously dissecting it with a Colorado needle. Fat can be removed up to the limit of the intraconal space (see Fig. 54.3). Lipectomies can also precede step 2 in order to aid subsequent bone exposure, and can be alone sufficient to attain an adequate decompression effect.
Step 7. The pure transinferior fornix incision is not sutured; tissues are simply repositioned (Fig. 54.5F). Where the conjunctival incision is extended upwards, laterally to the caruncle, such an extension may require two to three interrupted 8.0 absorbable sutures to adequately reapproximate the conjunctiva. Where a lateral canthotomy and inferior cantholysis is performed, the lateral canthal tendon should be reapproximated to the periosteum of the lateral orbital rim with a 5.0 long acting absorbable suture. Orbicularis muscle and skin are closed in layers respectively with 6.0 long acting absorbable and 6.0 non-absorbable sutures, or at the same time by means of 6.0 vertical mattress non-absorbable sutures. Skin sutures can be removed 5–7 days after surgery; vertical mattress sutures are removed later, approximately at postoperative day 10.

Orbital decompression by upper skin crease approach: surgical technique

Step 4. Zygomatic temporal and facial neurovascular bundles are coagulated by means of diathermy forceps and the lateral orbital osteotomy initiated with a surgical high speed drill equipped with a cutting-burr or a diamond-burr tip. A first sulcus is carved from just inside the lateral orbital rim, to the head of the superior orbital fissure (see Fig. 54.7D). It should run parallel to the plane of the orbital roof. A second sulcus is then carved from the head of the superior to the head of the inferior orbital fissure. The bone interposed between the two sulci and the lateral orbital rim is then removed leaving a small frame of bone at the level of the orbital rim. Finally the osteotomy is carefully extended superiorly and deeply by removing the spongious bone of the greater wing of the sphenoid up to its inner table or small spots of dura mater encephali are exposed.