Benign vascular anomalies of the orbit

Many vascular anomalies, such as varices, lymphangiomas and cavernous haemangiomas, are probably present from birth but may only become manifest in early adulthood.

Capillary haemangiomas

Capillary haemangiomas occur in 1-2% of infants and are more common in females and children of low birth weight; most appear soon after birth, can enlarge dramatically and then undergo a spontaneous involution - with 75% resolving within five years. Involvement is usually unilateral and the intradermal eyelid lesions are bright red and dimpled (so called, "strawberry naevus"; Figure 12.4), whereas the deeper orbital lesions have a blue colouration and spongy texture; both may increase slightly in size with crying or straining.

Figure 12.4 Orbital capillary haemangioma in an infant.

The rapid growth of a deep orbital capillary haemangioma may mimic the highly malignant rhabdomyosarcoma and it is important to be aware of this differential diagnosis; Doppler ultrasonography will, however, show high reflectivity and vessels with very high flow-rate (over 50cm/s) within the capillary haemangioma. CT scan is rarely necessary, but typically shows an irregular, poorly defined lesion with marked contrast enhancement.

Affected children should be monitored for impairment of visual development, being refracted when at an age suitable for spectacle correction of anisometropia or marked astigmatism. If the child is tending to develop an amblyopic eye, then appropriate corrective measures should be taken to maintain vision and consideration be given to treating the lesion.

Many capillary haemangiomas will regress rapidly, or their growth be slowed, by injecting them with corticosteroids under general anaesthesia; a useful regime being 40mg depomedrone in the lesion and 4mg soluble dexamethasone around the lesion, this being repeated at six-weekly intervals for two further sessions. Before injecting, the plunger must be drawn back and, if blood is present, the needle should be resited to avoid intravascular injection.

Systemic interferon has been used to treat steroid-resistant, life-threatening capillary haemangiomas, but the systemic side effects render it inapplicable to orbital lesions. Because of the risk of major haemorrhage, surgery is not recommended for most capillary haemangiomas.

When the haemangioma has regressed, it may be necessary to remove redundant atrophic eyelid skin or correct ptosis resulting from disinsertion of the levator muscle aponeurosis.

The complications of intralesional steroid injections are necrosis of the skin overlying the capillary haemangioma, and atrophy of subcutaneous fat or dermis. Rarely growth retardation and blindness have been reported with this therapy.

Cavernous haemangiomas

Cavernous haemangioma is the most common benign orbital tumour of adults and may be a developmental hamartoma that presents late in life, typically in the fourth or fifth decades, with gradually increasing painless proptosis. It is usually solitary and lies in the retrobulbar space, thereby causing axial proptosis, induced presbyopia, choroidal folds and optic disc congestion. There is often a global reduction in the extremes of eye movement.

CT scanning reveals a well defined, round intraconal lesion that commonly displaces the optic nerve medially and, due to a very slow blood flow, shows a very slow and patchy contrast enhancement (Figure 12.5). Some haemangiomas are wedged in the orbital apex

Figure 12.5 CT scan appearance of well-defined intraconal cavernous haemangioma; the differential diagnosis being the rarer orbital neurilemmoma.

and these tend to present early due to optic neuropathy. On MRI scanning, cavernous haemangiomas are hypointense to fat on T1-weighted images and isointense to vitreous and hyperintense to fat and vitreous on T2-weighted images.

Patients with asymptomatic tumours, discovered by chance on imaging for other reasons, can be monitored for orbital signs and many presumed haemangiomas show minimal change over many years. Indications for removal include optic neuropathy, proptosis and diplopia.

Lateral orbitotomy with intact excision of the tumour is usually required, as many haemangiomas are large and intraconal. The tumour typically is like a purple plum and contains large blood-filled cystic spaces.

Method for lateral orbitotomy

An upper eyelid skin-crease incision is extended laterally to about 1cm below the lateral canthus (Figure 12.6a) and the tissues opened to the supero-lateral orbital rim. The periosteum is incised 6mm outside the rim, from the lateral one-third of the upper rim to the level of the zygomatic arch, the origin of the temporalis muscle separated from the bone over its antero-superior 2cm, and the periosteal incision extended backwards over the zygomatic arch (Figure 12.6b).The periosteum is elevated over the rim of the orbit and separated from the inner aspect of the lateral wall, with particular care being taken to cauterise and divide any bridging vessels. Two parallel saw cuts are made, in the coronal plane, at the upper and lower ends of the lateral osteotomy, drill holes placed either side of the cuts and the inner aspect of the lateral wall fragment weakened 1cm behind the rim, using a burr; the fragment is then broken away and trimmed, to be swung outwards on the temporalis muscle (Figure 12.6c), and the periosteum opened to provide access for the intraorbital procedure.

After achieving intraorbital haemostasis, a vacuum drain is placed within the intraconal w ■ ä! M (f

(c)
Uterus Suspensory Ligaments

(b) (d) Figure 12.6 Lateral orbitotomy: (a) the largely hidden skin incision; (b) the periosteum being raised over the lateral rim; (c) the lateral wall hinged outwards on temporalis muscle; (d) the bone fixed in position with a 4/0 absorbable suture.

space and passed out through the skin overlying the temporalis fossa. The bone is swung medially into the correct position and fixed into place with a 4/0 absorbable suture passed through the drill holes (Figure 12.6d). The deep subcutaneous tissues over the outer canthus and further laterally are closed with a 4/0 or 5/0 absorbable suture and the skin incision closed with a running 6/0 nylon suture.

The patient should be nursed upright after surgery and it is important that any severe or increasing pain is reported. Where pain is severe or increasing, the vision in the affected eye and the state of the orbit should be checked; a very tense orbit with markedly decreased vision, a relative afferent pupillary defect and loss of eye movements, suggests accumulation of orbital haemorrhage and this may lead to irreversible visual loss. If this emergency appears to be developing, the drain should be moved slightly to see if drainage of fluid from the orbit occurs; if this does not succeed, the operative site should be reopened at the "bedside", without delay, and any accumulation of blood allowed to drain.

The vacuum drain is removed when active fluid drainage has ceased (usually 12-18 hours after surgery) and post operative systemic anti-inflammatory medications at high dosage are useful, particularly where there has been manipulation in the region of the superior orbital fissure or optic nerve. The patient should refrain from vigorous exercise for 10 days after surgery, normal ocular ductions encouraged and the skin suture removed at one week.

Complications

Excision of cavernous haemangiomas is curative, although the induced hyperopia and choroidal folds do not resolve in all cases.

Complications with removal of cavernous haemangiomas are more related to the lateral orbitotomy and the need to displace tissues to reach the tumour. It is common to get a transient weakness of ocular ductions, particularly abduction, and this typically improves over several weeks. Motor neuropraxias, which may recover over many months, are also fairly common with surgery near the orbital apex and superior orbital fissure; post operative mydriasis, probably due to denervation at the ciliary ganglion, is relatively common and may be permanent. Blindness due to optic nerve compression or ischaemia is a distinct risk with any surgery involving the posterior half of the orbit.

Orbital varices and lymphangiomas

Orbital varices and lymphangiomas are a spectrum of congenital low-pressure vascular malformations with venous-type channels that typically are unilateral and may involve ipsilateral parts of the face and brain, as well as the orbit.

In the absence of lymphatics from the human orbit, the term "lymphangioma" appears to be a misnomer. It serves, however, to emphasise an important clinical distinction between the two groups of low-pressure vascular anomalies that occur in various admixtures within different patients. Varices are largely blood-filled and generally in free communication with the normal low-pressure vascular system of the orbit, whereas "lymphangiomas" are largely isolated from the venous system and have a much greater component of inflammatory infiltration.

Whilst an ophthalmologist should supervise the day-to-day management of visual development of children with these malformations, the surgical management is an ophthalmic specialist field, being both difficult and liable to complication.

Lymphangiomas

These typically present between the ages of 6 and 10 years, as haemorrhage within cystic spaces deep in the orbit (so-called "chocolate cysts") or as superficial lesions with multi-loculated cysts of the conjunctiva or lid margin; proptosis and displacement of the globe occur as deep components enlarge. An increase in the size of lymphangiomas during respiratory infections, possibly due to lymphoid hypertrophy or vascular congestion, is frequently noted with these malformations. Orbital CT scan will demonstrate irregular, multi-loculated cystic opacities within the normal (but displaced) structures of an expanded orbit. Ultrasonography often shows acoustically empty cystic spaces.

An attempt should be made to optimise visual development in the eye affected by the orbital malformation, with treatment of anisometropia or astigmatism, and occlusion of the unaffected eye where necessary. Complete surgical excision of orbital lymphangiomas is, effectively, impossible and would be liable to damage the interspersed normal orbital structures. Surgery is, therefore, reserved for debulking the lesion anterior to the equator of the globe to improve cosmesis - for example, where there is prolapse of abnormal tissues through the palpebral aperture. Otherwise deep components may be drained or resected where there is gross displacement of the globe or compressive optic neuropathy.

Despite all efforts to maintain visual development, large lymphangiomas almost inevitably result in some degree of amblyopia. Compressive optic neuropathy may result from large intraorbital haemorrhages and there is a risk to all orbital structures during surgery to drain or excise these lesions.

Orbital varices

Although very rarely secondary to orbital arterio-venous communication, almost all varices are primary, congenital, low-pressure malformations that typically present in the second or third decade. Many patients will first notice intermittent proptosis, occasionally painful, on bending or straining and this may be simulated, during examination, by the Valsalva manoeuvre; in some cases the varices are non-distensible and may present with a sudden onset of painful proptosis due to haemorrhage within the varix.

Orbital enlargement on CT scan is common with varices and the serpiginous opacities of the malformation (Figure 12.7) may show phleboliths, small flecks of calcification within intravascular thrombi. Management of orbital varices is similar to that for the allied lymphangiomas, with maintenance of visual development and limited surgical intervention for anterior lesions, or large malformations causing visual problems or a major interruption of life-style; surgical resection carries, however, a significant risk of major haemorrhage and blindness.

Orbital Varix Calcification
Figure 12.7 CT scan of orbital varices in an enlarged orbit.

Orbital arterio-venous communica tions

High-pressure arterio-venous communications within the orbit are characterised by pulsatile proptosis and chemosis, a global reduction in eye movements and dilation of episcleral veins with raised intraocular pressure. The high pressure and flow within the orbital veins may result from an arterio-venous shunt within the orbit or in the anterior part of the intracranial circulation.

Intraorbital arterio-venous malformations

Branches of both the internal and external carotid arteries commonly supply orbital arterio-venous malformations, either spontaneous or post-traumatic. CT scan typically shows unilateral proptosis with mild enlargement of all extraocular muscles, a diffuse increase in opacity of the orbital fat and widespread engorgement of tortuous orbital vessels. Orbital Doppler ultrasonography will show widespread engorgement of vessels and arterial waveforms within veins - particularly the superior ophthalmic vein where there may be reversal of the (normally posteriorly-directed) flow.

Super-selective angiography of branches of the internal and external carotid arteries is required, with embolisation of the vessels supplying the abnormal communication. Resection of remaining abnormal vessels may be undertaken, although surgery for these lesions tends to be difficult and the results somewhat unsatisfactory.

Dural shunts

Dural shunts commonly present with a chronic "red eye" (Figure 12.8) and are due to a spontaneous fistula between a minor dural vessel and the cavernous venous sinus. CT scan shows orbital changes similar to those of an intraorbital arterio-venous communication

Episcleral Branches
Figure 12.8 Dilated episcleral veins due to a low-flow dural arterio-venous shunt.

but, in addition, there may be engorgement of the ipsilateral cavernous sinus and possibly also some subtle changes in the contralateral cavernous sinus and orbit. Doppler ultrasonography is, again, valuable in the diagnosis of these lesions.

Most low-flow dural arterio-venous shunts will resolve spontaneously over many months and treatment (with arteriography and possible embolisation) is required only where a high-flow fistula is causing visual failure, unacceptable proptosis, or persistent severe proptosis.

Carotico-cavernous fistula

These high-pressure, high-flow communications generally present with acute proptosis, eyelid swelling, chemosis with engorged episcleral vessels, raised intraocular pressure, retinal haemorrhages and ocular ischaemia; in some cases palsies of the third and sixth cranial nerves may be present. They arise spontaneously in atheromatous individuals, with rupture of the intracavernous internal carotid artery into the venous sinus, or occur after severe head injury (Figure 12.9).

Radiological imaging shows a more extreme version of the changes seen with low-flow dural shunts and arteriography is required in most cases. Balloon occlusion of the fistula is

Figure 12.9 Gross chemosis, proptosis and vascular dilation due to high-flow post-traumatic carotico-cavernous fistula.

effective in 90% of cases and has a low morbidity.

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