orbital cavernous venous malformation

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Cavernous venous malformations of the orbit, also known as cavernous hemangiomas, are the most common vascular lesion of the orbit in adults.

It is important to note that according to newer nomenclature (ISSVA classification of vascular anomalies) these lesions are merely known as slow flow venous malformations. Having said that, it is probably helpful in reports to include the word 'cavernous' as this term is ubiquitous in the literature and most familiar to many clinicians.

Cavernous malformations are found throughout the body. This article focuses on orbital cavernous hemangiomas. For a general discussion please refer to the general article on cavernous venous malformation.

Epidemiology

Cavernous hemangiomas are the most common vascular lesions of the orbit in adults and account for 5-7% of all orbital tumors. However, debate exists about whether these lesions should actually be considered tumors . They usually present in middle age (30-50 years of age) and there appears to be a female predilection .

Clinical presentation

Clinical presentation is usually with a slowly growing orbital mass resulting in proptosis. Diplopia and visual field defects (from optic nerve compression) may also occur .

Pathology

Cavernous hemangiomas are well-circumscribed masses bounded by a fibrous pseudocapsule, without prominent arterial supply (accounting for the relatively slow enhancement). They are composed of dilated large vascular spaces (thus cavernous) lined by flattened and attenuated endothelial cells .

As flow is slow, and vascular spaces large, areas of thrombosis are common .

Unlike the name 'hemangioma' suggests, these lesions may not be tumors as there is no cellular proliferation , but rather gradually enlarging vascular malformations and as such some authors prefer the term cavernous malformation.

In some cases prominent fibrosis is present, and these lesions are referred to by some authors as sclerosing hemangiomas .

Radiographic features

Although cavernous hemangiomas can be located anywhere within the orbit (and for that matter pretty much anywhere in the body: see cavernous venous malformation article) over 80% are located within the intraconal compartment, most commonly in the lateral aspect .

They are usually round or oval in cross-section and although frequently abut the globe, they do not deform it, but rather are deformed by the globe, on account of their soft consistency .

Large lesions may be associated with the expansion of the bony confines of the orbit .

Ultrasound

Ultrasound demonstrates a smoothly circumscribed retrobulbar lesion with regular moderate to high internal echogenicity . No flow can be demonstrated on Doppler scanning .

CT

Cavernous hemangioma appears as a well-circumscribed, rounded or oval soft tissue density mass when they are small and becomes deformed due to their soft nature when getting larger; they are somewhat hypoattenuating compared to the muscle which gradually and incompletely fills in following the administration of contrast .

The orbital apex is usually spared .

Sclerosing hemangiomas sometimes demonstrate calcification .

MRI

Appearance on MRI is the same morphologically as on CT, with the following signal intensities:

T1
- isointense compared to muscle
- if areas of thrombosis are present, then hyperintense regions may be visible
T2
- hyperintense compared to muscle
- may have low-intensity septation
- pseudocapsule is of low intensity
T1 C+ (Gd): slow gradual irregular enhancement with delayed washout

DSA

Angiographically hemangiomas are occult as enhancement occurs only in a delayed fashion .

Treatment and prognosis

If the lesion is found incidentally and no exophthalmos or visual complications are present then conservative management is recommended, with periodic MRI imaging.

In cases where symptoms are present, or growth of the lesion is demonstrated on follow-up imaging, surgical removal is curative.