Careful assessment of clinical signs and symptoms and their chronology and various associations helps to differentiate the various disease processes that present as space-occupying masses. The cardinal sign suggestive of orbital tumor is eye exophthalmos, or proptosis. Displacement of the globe horizontally or vertically is often referred to as dystopia and may suggest a particular location within the orbit.
In the evaluation of globe protrusion, distinguishing between pseudexophthalmos and exophthalmos is essential. In the ipsilateral eye, lid retraction such as in Graves disease may give the appearance of exophthalmos, as can congenital glaucoma and unilateral high myopia. Features of the contralateral eye such as microphthalmos due to a congenital abnormality may give the examiner a false impression of exophthalmos; the same is true for enophthalmos caused by various processes, including blow-out orbital fractures, inflammatory processes, and orbital involvement of metastatic scirrhous adenocarcinomas, usually originating in the breast. Congenital disease-related craniofacial asymmetries may also give the false impression of exophthalmos. True exophthalmos may be associated with those craniofacial abnormalities (for example, those found in Crouzon disease and Apert syndrome) associated with midface hypoplasia. An accurate diagnosis will be assisted by a strong degree of suspicion of pseudexophthalmos, careful assessment of patient history, and thorough physical examination in which emphasis is placed on visual inspection; if available, an exophthalmometer will also aid in diagnosis.
Several features of the history, such as unilateral compared with bilateral eye involvement, direction of displacement, patient age, and the rate of symptom onset may help establish the nature of the disease. Bilateral globe protrusion is more likely in cases of systemic disease such as dysthyroid orbitopathy, and this is usually easily distinguished from unilateral orbital tumors. In the less common cases in which a thyroid origin results in unilateral exophthalmos, retraction of the eyelid can help identify this origin, as can a detailed clinical history, physical examination, and laboratory thyroid function tests. A discussion of dysthyroid orbitopathy will not be covered in this article, as it is not a true tumor and its relevance to the surgeon is limited to differential diagnosis and to the rare cases in which myxedema is severe enough to warrant surgery for corneal exposure or compressive optic neuropathy. Bilateral exophthalmos may occasionally be a feature of certain orbital tumors such as lymphoma, histiocytoma, or metastatic lesions.
Etiopathological information may be inferred from the tumor mass-induced direction of global deviation. With rare exceptions, tumor growth displaces the globe away from the lesion. Tumors of the lacrimal gland, for example, classically induce medial and inferior displacement of the globe. Tumors of the optic nerve generally cause displacement of the globe along the axis of the orbit, whereas tumors arising from the extraocular muscles tend toward axial and slightly inferior displacement of the eye.
The patient's age of onset of the exophthalmos is also important because the incidence of certain lesions is different in the pediatric and adult populations. Infants and neonates with congenital, often subtle exophthalmos, are more likely to harbor teratomas, dermoid cysts, and capillary hemangiomas than the slightly older early childhood group in which the children are most likely to harbor lyphangiomas, optic gliomas such as pilocytic astrocytomas, or rhabdomyosarcomas. Lacrimal gland tumors, metastases to the orbit, cavernous hemangiomas, and neurilemmomas are more likely to occur in adults.
In general, a lesion that grows insidiously is more likely benign, whereas a more rapid process indicates a more aggressive histological type. Hyperacute onset of exophthalmos is more likely to be caused by inflammatory processes than tumor growth, and this should help guide investigations.
The rate and extent of visual acuity deterioration is of great importance in distinguishing primary from secondary involvement of the optic nerve. An optic nerve glioma or nerve sheath meningioma tends to cause profound visual deterioration, whereas a tumor that is external to the nerve affects visual acuity by compression and causes a mild visual deficit unless it is very advanced and is exerting considerable mass effect.
Pain is commonly a feature of inflammatory diseases or infections such as myositis or dacryoadenitis, although metastases and rapidly expanding neoplastic processes may also cause symptomatic pain. Orbital lesion-induced pain tends to be localized, constant, and may be more prominent at night. The sudden onset of orbital pain in a child may be caused by a hemorrhage into a cystic lymphangioma. Processes causing pain that can be localized deep in the orbit suggest orbital apex involvement, especially when there is ophthalmoplegia and/or facial dysesthesias in the distribution of V2. Benign tumors of the orbit usually tend not to cause any pain, although a feeling of pressure in the orbit is typically reported in cases of slowgrowing lesions.
There are two mechanisms by which a tumor can cause diplopia: first, by infiltrating the nerves supplying the extraocular muscles, which is seen with malignant tumors and metastases; and second, by restricting the normal extraocular motility function and/or deviating the axis of the eye. A sudden onset of normal extraocular motility loss is usually associated with an aggressive malignant lesion.
Changes in the size of the pupils can be observed in cases in which the tumors invade or compress the parasympathetic (third nerve through the ciliary ganglion) or the sympathetic fibers innervating the pupillary dilators. This is found in cases of chemodectomas (paragangliomas), but many tumor types can also cause anisocoria through involvement of the sympathetic or parasympathetic fibers supplying the iris dilator and pupillary sphincter.
Bruits may occur with AVMs and may be a source of distress to patients, who may describe constant or intermittent sounds that are pulsatile or swishing in nature. They may also have a positional component, being exacerbated with recumbency. This symptom is associated with arteriovenous fistulas, and more often of traumatic origin.
A variety of fundus changes can be observed in association with orbital tumors. Optic atrophy, which may be preceded by edema, is characteristic of long-standing optic nerve damage. Compressive lesions that impede drainage though the central retinal vein can cause optociliary shunts, which consist of enlarged preexisting peripapillary vessels that divert blood from the central retinal venous circulation to the peripapillary choroidal circulation when obstruction of the normal drainage channels occurs. These can be demonstrated in patients with optic nerve sheath meningiomas, although they are seen most commonly with central retinal vein occlusion. Choroidal folds are a series of parallel, alternating light and dark striae, which are a common manifestation of a variety of lesions including orbital tumors. They tend to be more common when the globe is directly compressed, especially by anteriorly placed tumors, but at times they can precede the occurrence of clinically evident exophthalmos. Venous dilation can be associated with disc edema in patients with orbital masses when the optic nerve is compressed.
Anteriorly located tumors can present with eyelid swelling (Figure 12 upper) and can be visible on ispection (Figure 12 lower).
Neurosurg Focus. 2001;10(5) © 2001 American Association of Neurological Surgeons
Cite this: An Introductory Overview of Orbital Tumors - Medscape - May 01, 2001.