2.5\ Orbital Decompression

and Expansion

for Dysthyroid Orbitopathy

2.5.1\ Discussion

Orbital decompression for dysthyroid orbitopathy serves to reduce proptosis and intraocular pressure and improve compressive optic neuropathy­ . Bone from the medial, lateral, or inferior orbital walls may be removed via a variety of endonasal or external approaches (Fig. 2.18). The enlarged orbital fat and rectus muscles can then bulge through these defects, resulting in a decrease in intraorbital pressure. A transnasal endoscopic approach is commonly implemented for inferior and medial wall decompression. As a result, resection of a portion of the

a

paranasal sinuses may also be observed on follow-up imaging. Serious complications related to orbital decompression occur in 3–5% of cases depending on the particular technique and include chronic sinusitis, meningitis, optic neuropathy, orbital cellulitis, hemorrhage, nasolacrimal duct obstruction, and inadequate proptosis reduction. In addition, excess herniation of orbital contents through the surgical defects can result in obstructed paranasal sinus secretions (Fig. 2.19). Diplopia from displacement of orbital contents, including the extraocular muscles occurs in up to 25% of patients.

Another option for treating exophthalmos in patients with dysthyroid orbitopathy is to expand the orbital vault anteriorly, which can be accomplished using augmentation implants attached to the orbital rim (Fig. 2.20).

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Fig. 2.19  Paranasal sinus obstruction after orbital decompression. The patient presents with left sinus pressure after orbital decompression for dysthyroid orbitopathy. Coronal CT image shows obstructed left maxillary sinus secretions secondary to obstruction by inferior extension of the orbital fat (arrow) through the surgical defect

a

b

Fig.2.20  Orbital rim augmentation. Axial (a) and 3D (b) CT images in a patient with dysthyroid orbitopathy show that hardware below the bilateral inferior orbital rims was used to secure a porous polyethylene implant (not visible on these images)

2.6\ Dacryocystorhinostomy

and Nasolacrimal Duct

Stents

2.6.1\ Discussion

Dacryocystorhinostomy (DCR) can be performed to relieve distal lacrimal obstruction at the level of the lacrimal sac or duct. Both external and endonasal approaches can be used to remove bone in the region of the medial canthus in order to create a fistula between the nasolacrimal sac and the medial meatus of the nasal cavity. Silicone tubes are usually temporarily inserted through this fistula to ensure prolonged patency. Postoperative complications occur in about 6% of cases and most commonly include restenosis with recurrent epiphora or dacryocystitis. Patency of the dacryocystorhinostomy can be evaluated

a

via a dacryocystogram (Fig. 2.21). Surgical success rates are high with reports mostly ranging in the 90% and above.

In cases of proximal lacrimal stenosis involving the canaliculi, conjunctivodacryocystorhinostomy (CDCR) can be performed. This procedure involves the placement of a Jones tube, which is a direct bypass from the ocular surface to the middle meatus of the nose (Fig. 2.22). These Pyrex glass tubes are readily depicted on CT, which can be used effectively to assess for complications, such as malposition, migration, or inflammation of surrounding tissues. An uncommon complication of Jones tube placement is pneumo-orbit, which can occur after CPAP use, sneezing, or nose blowing, and can result in proptosis if a significant amount of air is forced through the tube (Fig. 2.23).

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Fig. 2.21  Dacryocystorhinostomy. Axial (a) and coronal (b) CT images show an osteotomy predominantly through the anterior lacrimal crest of the left maxilla (arrows) after external dacryocystorhinostomy. Radiograph (c) and axial

CT (d) images from a left dacryocystogram verify free spillage of contrast into the ethmoid air cells/nasal cavity (arrowheads)

Fig. 2.22  Conjunctivodacryocystorhinostomy (CDCR) with Jones tube. Coronal CT image shows a left CDCR with a Pyrex glass Jones tube in position (arrow). The tube connects the ocular surface with the middle meatus of the nose. In this case, it is somewhat medially displaced

Fig. 2.23  Pneumo-orbit with Jones tube. The patient had a history of CDCR with Jones tube placement and presented with proptosis after sneezing. Coronal CT image shows a Jones tube (arrow) and extensive air within the left orbit