Neuro-Ophthalmic Aspects of Orbital Disease

Orbital diseases are distinct from primary ocular disorders in that they require consider- ation of a much larger group of differential diagnoses. Thus, ptosis may be attributable to a “simple” problem in the anterior segment, but may also be the clinical presentation of a more general disorder, such as Horner’s syndrome, oculomotor paralysis, or myas- thenia gravis. One must also consider orbital involvement in primary disorders of the periorbital structures, including the paranasal sinuses and the intracranial space.

Neuro-Ophthalmic Aspects of Orbital Disease

S. Pitz

Basic Orbital Anatomy

Structures surrounding the orbit and the proportional distribution of structures within the orbit are schematically diagrammed in ^■ Fig. 9.1. The close relationship of the orbital walls with the paranasal sinuses is particularly important ( ^■ Fig. 9.2).

In company with the optic nerve, the optic canal also conducts the ophthalmic artery and the postganglionic sympathetic fibers that arise from the carotid plexus. All three of these structures feed through the annulus of Zinn, a surrounding ring of connective tissue that anchors the origin of all four rectus muscles ( ^■ Fig. 9.3).

Fig. 9.1. Spatial relationships and comparative sizes of orbit, optic nerve, and chiasm (modified after Rootman; see Further Reading)

Fig. 9.2. Regional relationships between the paranasal sinuses and the orbits

• ^Pearl

Given the restricted space within the optic canal and the fibrous connections between the dura, the peri- osteum of the orbital walls, the dural sheath of the nerve, and the annulus of Zinn, inflammation in this region causes pain when the rectus muscles contract.

Pain on eye motion is a common feature of demyelinat- ing optic neuritis (see Chap. 8), and the afferent so- matosensory pathway is by way of the nasociliary nerve.

Another important structural feature of the orbit is the su- perior orbital fissure, which provides access to the orbit for nearly all other vascular and neural structures that support ocular function. It is formed as an opening between the greater and lesser wings of the sphenoid. The important structures passing through the fissure are illustrated in

tionally important venous exit from the orbit. It flows into the cavernous sinus. The nasolacrimal nerve, arising from the ophthalmic division of the fifth cranial nerve, supplies the lacrimal gland and the frontal nerve divides into two primary branches, the supratrochlear nerve and supraor- bital nerve. These two provide the afferent sensory pathway for the forehead and upper lid.

While the oculomotor and the abducens nerves both pass through the tendinous annulus at the orbital apex to innervate the extraocular muscles from within the intra- conal space, this is not the case for the trochlear nerve. Its relatively “unprotected” intraorbital course (external to the muscle cone and close to the orbital roof) contributes to its greater vulnerability in cranial injuries. The trochlear is also the thinnest and longest of the cranial nerves, arising from the dorsal midbrain and decussating through the an- terior medullary velum. The thin tissue through which the

Fig. 9.3. Coronal plane section of the right orbital apex as seen from within the orbit and the various structures that pass through the optic canal, the superior orbital fissure, and the inferior orbital fissure. The optic nerve is at the center, emerging from the canal to pass through the annulus of Zinn. Superolateral to the canal lies the superior orbital fissure.

Structures passing through the fissure

(ordered from cranial to caudal) include

the lacrimal nerve, the superior ophthal-

mic vein, a branch of the middle menin-

geal artery, the frontal nerve, and the tro-

chlear nerve. Farther below, the oculomo-

tor nerve, the nasociliary nerve, and sym-

pathetic nerve fibers pass through the

tendinous annulus of Zinn. The ophthal-

mic artery also passes through the canal

and the annulus, along a course located

inferior to the optic nerve (modified from

Stewart; see Further Reading)

juries due to torsional stresses that lead to tearing and bleeding. This is a common cause of bilateral fourth nerve palsies.

The inferior orbital fissure is connected to the superior orbital fissure. Through its cleft is a communication be- tween the orbital contents and those of the pterygoid fossa.

It contains the inferior ophthalmic vein, which drains blood from the inferior orbital structures, including the in- ferior portions of the globe (via the inferior vortex veins).

It then empties into the pterygoid plexus. This soft tissue passage between the orbit and the pterygopalatine fossa provides a pathway of least resistance for the spread of pathologic processes, including bacterial infections and malignant cancers. The volume of venous flow through the inferior fissure is smaller, more variable, and less important than the flow through the superior ophthalmic vein. This passage also contains the infraorbital nerve, which arises from the maxillary division of the trigeminal nerve and passes through the foramen rotundum in the skull base and then through the inferior orbital fissure. It courses along the orbital floor in a groove on the dorsal surface of the maxillary roof, partly covered by connective tissue, and then through the infraorbital canal to innervate the lower lid and portions of the upper cheek.

• ^Pearl

Fractures of the orbital floor, in addition to causing mechanical and paralytic disturbances of ocular motil- ity, also cause hypesthesia or complete somatosensory loss in the ipsilateral incisors, gingiva, cheek, and the mucosal surface of the upper lip.

The orbital connective tissues are thin and delicate, and they are difficult to demonstrate during surgical proce- dures. Nonetheless, they provide significant barriers to the spread of diseases between the various compartments that they form: Tenon’s capsule is a barrier that extends from the limbus to the dural sheath of the optic nerve, separating the globe from the remainder of the orbital contents. Connec- tions between Tenon’s capsule and the sheaths of the extra- ocular muscles form a conical space in the retrobulbar orbit that is separated from the remaining structures that lie out- side of the cone.

• ^Pearl

In the setting of orbital floor fractures, the typical me- chanical restriction of elevation and depression is more often the result of entrapment of the connective tissues surrounding the inferior rectus, rather than a direct hold on the muscle itself.

Signs and Symptoms of Orbital Disease Exophthalmos

The confined space within the bony orbit limits the expan- sion of orbital contents, which then prolapse through its anterior opening. This is the signal feature of many orbital diseases. Pulsating exophthalmos is a common accompani- ment of structural defects in the sphenoid wings (Neurofi- bromatosis) or with vascular disorders like arteriovenous fistulas. The pulse synchronous movement of the globe is most easily seen during applanation tonometry, when the applanated circle surrounded by the tear film meniscus can be seen pulsing.

! ^Note

Pseudoexophthalmos is a term to describe an apparent forward protrusion of the globe caused by primary ocular disorders, such as high axial myopia, rather than by pressure on the globe from enlarged retrobulbar structures.

Diplopia

Binocular diplopia can arise by three different mechanisms:

by displacement of the globe, by damage to of the motor cranial nerves, or by damage to the extraocular muscles (e.g., Graves’ disease, chronic progressive external ophthal- moplegia, or myasthenia).

Changes of Lid Position Ptosis

■ Table 9.1 provides an overview of the potential causes of ptosis.

Table 9.1. The causes of ptosis Congenital ptosis

( ■ Fig. 9.4) Can be isolated, associated with an ipsilateral elevator palsy, or with the familial fibrosis syndrome, or with mandibulopalpebral synkinesis (The Marcus-Gunn jaw-winking phenomenon)

Acquired ptosis Involutional (age-related dehiscence of the levator tendon), innervational (third nerve palsy, Horner’s syndrome), myasthenic, or with chronic progressive external ophthalmoplegia, chronic use of contact lenses, or topical preparations of corticosteroids

Video 9.1

Lid Retraction

■ Table 9.2 lists the disorders that commonly cause lid retraction.

Pseudo–lid retraction must be ruled out (unilateral because of compensation for a contralateral ptosis, or bilat- eral lid retraction caused by hypersympathotonia, such as in thyroid storm, anxiety, or panic attacks).

• ^Pearl

Lifting the ptotic lid will allow normalization of the re- tracted upper lid position contralateral to a monocular ptosis.

Loss of Vision

Orbital diseases cause impairment of vision, whether mild or severe, by one of two primary mechanisms. On one hand, the globe may be distorted or displaced by direct contact with a space-occupying process, and on the other hand, the optic nerve may be damaged by direct compres- sion.

Chemosis

Chemosis is associated with a variety of usually benign dis- ease processes in the anterior segment, but can also be typical of a group of orbital disorders: orbital inflammatory diseases, such as idiopathic inflammatory pseudotumor, ocular myositis, dysthyroid ophthalmopathy, or any im- pairment of venous outflow from the orbit (e.g., carotid–

Diagnostic Methods

■ Table 9.3 summarizes the various diagnostic methods used for the study of orbital disease.

A rational plan for treatment also requires additional testing in the form of MRI and/or CT imaging. Ultrasonog- raphy is most suited to the study of midorbital structures.

Study of anterior orbital structures requires the use of a standoff method, such as immersion of the probe in a water bath that covers the eye. The posterior third of the orbit cannot be imaged by ultrasonography, due to both limited tissue penetration by the sound and by reverberations of the sound off of the closely approximated surfaces of the bony orbital walls. Duplex echography is particularly help- ful when studying space-occupying lesions that arise from vascular disorders, such as hemangiomas, arteriovenous communications, and dural sinus fistulas. It can determine the direction and relative volume of blood flow in the or- bital vessels, which is a particularly helpful and noninva- sive method. The physician planning the study and treat- ment of orbital diseases must rely primarily on tissue biop- sies, and MRI and CT imaging of orbital hard and soft tis- sues. The choice between MRI and CT is governed by the nature of the disease (disorders of soft versus those of bone tissues, for example). Additional important considerations include the time needed for the studies. CT scanning is quicker and less affected by movement artifacts, and is thus advantageous for cases of children or elderly patients with a limited capacity to lie quietly still.

! ^Note

Patients with cardiac pacemakers cannot be safely scanned by MRI, since the strong magnetic field can cause the device to malfunction or its battery to over- heat or change its position, all of which are potentially fatal consequences.

Table 9.2. The causes of lid retraction

Disease Pathogenesis

Graves’ disease Initially driven by sympathetic hypertonus in Müller’s muscle, later by the inflammatory fibrosis of chronic myositis

Dorsal midbrain disease

(so-called Collier’s sign) Loss of inhibitory supranuclear input to the third nerve nuclear complex

Intracranial hypertension Mechanism thought to be similar to the effects of dorsal midbrain disease

Topical glaucoma drugs (epinephrine, Dipivefrin, clonidine/apraclonidine)

Sympathomimetic effect

Mechanical retraction

of the upper lid Surgical effect, mass effect

Fig. 9.4. A small boy with congenital ptosis. Most striking is the

asymmetry of the lid folds. On the ptotic side it is hard to identify

The CT scan is ideally suited to the study of bony struc- tures, while the MRI is best suited to the diagnostic exami- nation of soft tissues. To obtain optimal images in the coro- nal planes of the orbit the patient must lie in the prone position with the neck maximally extended. Coronal re- constructions of data obtained in transaxial views are sig- nificantly less detailed. For MRI scanning a recumbent position is used, which is better tolerated by the elderly and patients with poor joint flexibility. Lastly, the CT scan is the radiologic procedure that exposes the eyes’ lenses to the greatest dose of radiation, while the MRI requires no expo- sure to ionizing radiation (also see Chap. 20).

Exophthalmos as the Presenting Sign Graves’ Disease

Clinical Features of Graves’ Disease

Graves’ disease (also called thyroid ophthalmopathy, dys- thyroid ophthalmopathy, or endocrine orbitopathy) is an autoimmune disease that commonly, though not always, is associated with hyperthyroidism. It is accompanied by a broad spectrum of signs and symptoms of orbital inflam- mation. Chief among these is exophthalmos. Graves’ dis- ease is the most common cause of exophthalmos among

Table 9.3. Diagnostic testing for a suspected orbital mass

Signs and symptoms Methods Remarks

“My glasses no longer work” Manifest refraction Lenticular myopia of uncontrolled diabetes?

Axial hyperopia due to proptosis by orbital mass?

Axial proptosis Hertel exophthalmometry Mismatch between eyes of up to 2 mm is within normal limits – there is high statistical variance between examiners

and examinations.

Always compare to base line measures.

Axial proptosis View eye position of patient from above and behind, looking down over the patient’s brow

Interocular differences >2 mm can be easily seen.

Helpful when Hertel values show large interocular mismatch.

Horizontal or vertical

globe displacement Ruler

Kestenbaum glasses Compare with old photos of patient

Globe displacement Palpation Symmetrical resistance to retropulsion?

Is there a bruit?

Pulsatile exophthalmos? Crepitation?

Bruit Auscultation Murmur

Pupillary motility See Chap. 5

Ocular motility See Chaps. 10 and 11 Forced duction tests when indicated

Interpalpebral fissure 10–12 mm Measure at primary position when patient is fully relaxed;

For monocular ptosis or lid retraction, measure eyes individually Compare upper lid positions

in downgaze Watch out for pseudowidening of lid fissure when contralateral to a ptotic lid;

Vertical mismatch in downgaze (Graves’ congenital ptosis – postsurgical shortening of upper lid)

Levator function 12–18 mm Maximum lid excursion (from full downgaze to full upgaze positions) while restraining frontalis movements

(Fix the forehead position in place with your hand placed horizontally across the brow)

Intraocular pressure Applanation tonometry Interocular mismatch?

Gaze direction effect on interocular pressure (IOP):

Measure IOP in primary and upgaze positions.

When elevation is markedly limited, measure IOP in partial downgaze versus partial upgaze attempt.

Prominent episceral vessels Slit-lamp examination Vascular distention by obstruction to orbital venous outflow?

Fundus Ophthalmoscopy Retinal/choroidal obstruction to venous outflow

Optic disc edema, choroidal folds

adults, and it is usually a bilateral and often very asymmet- ric disorder. This can lead to misdiagnoses during the early stages of the disease.

Initial symptoms most commonly include foreign-body sensation, a feeling of retrobulbar pressure or pain, tearing, blurring, and photophobia. With later inflammatory in- volvement of the extraocular muscles, diplopia begins to appear. All of these symptoms have a diurnal cycle, with the most symptomatic period at the time of awakening in the morning. In addition, and virtually pathognomonic, is the appearance of lid signs, including lid swelling, lower lid re- traction, upper lid retraction with lid lag (not moving in close synchrony with the globe during downward pursuit movements), and infrequent blinking or a staring expres- sion ( ^■ Fig. 9.5). These facial features are for many patients the most intolerable aspect of the disease. In addition, it can be accompanied by an acute or chronic swelling of the lacrimal gland. Other signs include conjunctival hyper- emia, chemosis, plical hyperemia, injection over the rectus muscle insertions, and exposure keratopathy. Mechanical strabismus arises from inflammation in the medial and in- ferior rectus muscles, which are the two muscles most com- monly affected. Fibrotic foreshortening of the muscles tethers the globe, limiting the ability to elevate or abduct the eye. Finally, a secondary glaucoma can develop and retinal or choroidal signs of optic nerve compression can appear. These include relative or absolute central scotomas, relative afferent pupillary defect, profound loss of visual acuity and color perception, and optic disc edema with sur- face exudates may be present. This is an emergent disorder that requires immediate reversal, usually accomplished by administering high doses of corticosteroids, followed by surgical decompression of the optic canal and orbital apex

Pathogenesis of Graves’ Disease

Graves’ disease is an autoimmune disorder. In 85% of cases there is initially a simultaneous autoimmune hyperthyroid state; in 10% of cases, a hypothyroid state; most of the due to Hashimoto’s thyroiditis. In the remaining 5% of cases, the early stages of Graves’ disease develop in the absence of any detectable thyroid dysfunction.

Diagnosis of Graves’ Disease

The diagnosis of Graves’ disease, aside from a history of thyroid problems, uses measures of visual acuity, pupillary light responses, and ocular motility. The configuration and movement of the lid margins should be carefully studied.

The slit-lamp examination should include the measure of intraocular pressure by applanation tonometry both in downgaze and in the primary position. Because of the fore- shortened rectus muscle’s traction on the globe, attempts to force the eye into the primary position often result in a marked, though transient, elevation of the intraocular pres- sure. Visual field testing and a sonographic determination of rectus muscle thickness by A-scan complete the workup.

Echographic confirmation of rectus muscle thickening in the midportions of muscle belly, but with no thickening at the tendinous insertions, is characteristic of Graves’ disease and differentiates it from orbital myositis, in which the in- flammatory swelling extends all the way to the point of insertion. In cases that remain in doubt as to the correct diagnosis, a thin-section CT scan of the orbit helps to rule out a mass lesion other than one or more swollen muscles.

High-resolution MRI scanning with determination of the T2-relaxation time produces images that can be used to judge the water content in the rectus muscles, a correlate for inflammatory edema.

Treatment of Graves’ Disease

When managing the problems of active Graves’ disease, the following measures are known to be of benefit: mainte- nance of a euthyroid state, avoidance of cigarette smoking (very important), use of topical hydrating agents (with or without preservatives, as needed), and nonsteroidal anti- inflammatory drugs. These are largely supportive therapy, allowing time to pass and inflammatory activity to subside, while protecting vision in the meantime. This is adequate for a majority of cases. Infrequently, one encounters cases of fulminant inflammatory disease that threaten destruc- tion of the eye through extreme exposure of the ocular sur- face and formation of corneal ulcers, or by compression of the optic nerve, which can destroy vision to the point of no light perception. The use of orbital irradiation and or surgi- cal decompression should be saved for these very danger- ous, high-risk cases. High doses of oral corticosteroids,

Fig. 9.5. A patient with Graves’ disease. Striking proptosis, left

more than right, with bilateral retraction of both upper and lower

eyelids, and severe conjunctival hyperemia

for periods of about a month. Longer than a month’s use, however, increases the risk of steroid use unacceptably. The drug is particularly valuable as a temporizing strategy for suppressing the inflammatory activity during the time leading to surgical decompression or radiation therapy of the orbital tissues. (For emergent intervention, 1,000 mg/

day of intravenously administered prednisone given in doses of 250 mg every 6 h will occasionally allow rapid re- covery of central vision). Radiation is given in ten equal, fractionated doses (usually on the weekdays of two con- secutive weeks) to a total exposure of 12 to 20 Gy. A few reports conclude that there is benefit in combined therapy, in which the corticosteroid treatment is maintained all the way through the period of radiation treatment. There is no consensus of agreement on this issue, however. The radia- tion is meant to destroy the entire monoclonal population of lymphocytes that have targeted the orbital tissues. Ben- efits of reduced inflammatory activity can be expected within 6 weeks of completing the radiotherapy.

If optic nerve compression threatens permanent dam- age to vision, surgical decompression of the bony orbital walls can allow the excess volume of orbital tissues to her- niate into the paranasal sinuses (medial and or inferior walls) or temporal fossa (lateral wall). Decompression in- creases the risk of strabismus, making management of the diplopia more difficult. Decompression is not very helpful for improving facial appearance, which is benefited far more by plastic surgical repositioning of the retracted eye- lids, but this step has to wait for the last. Diplopia usually cannot be managed by prisms due to the nonconcomitant nature of the mechanical strabismus. Surgical recession of shortened rectus muscles should be deferred until there has been at least 6 months of stability in the angle of strabis- mus, but has a good prognosis for correction of the diplo- pia. Prism glasses are occasionally helpful at this last stage of recovery, and repair of the lid positions should be de- ferred until the strabismus surgery has been competed.

• ^Pearl

Commonly, Graves’ disease is accompanied by other autoimmune disorders, such as primary, chronic poly- arthritis or ocular myasthenia, which can complicate the diagnosis and management considerably.

Tumors

Tumors of the orbit are usually heralded by symptoms aris- ing from displacement of the globe’s position in the orbit.

Tumors within the muscle cone push the eye anteriorly, producing an axial proptosis and a shortening of the axial length (secondary hyperopia). Frequently, the patient’s

presenting complaint is contact of the eyelashes with the posterior surface of the spectacle lens. Extraconal masses usually displace the globe toward the orbital wall that lies opposite to the position of the tumor. The differential diag- nosis can be refined based on the direction of displacement of the eye.

■ Intraconal–axial proptosis

■ Hemangioma

■ Varix

■ Optic nerve sheath meningioma

■ Optic nerve glioma

■ Metastasis

■ Extraconal superior orbital mass – inferodisplacement of the globe

■ Dermoid cyst

■ Lacrimal gland tumor

■ Mucocele

■ Lymphoma

■ Extraconal inferior orbital mass – supradisplacement of the globe

■ Lymphoma

■ Extraconal medial orbital mass – temporal displace- ment of the globe

■ Ethmoid or sphenoid sinus lesions (mucocele, car- cinoma)

■ Extraconal lateral orbital mass – medial displacement of the globe

■ Metastasis

■ Dermoid cyst

Idiopathic Orbital Inflammation

Clinical Presentation

: ^Definition

Orbital inflammation presents as an acute onset, pain- ful, monocular, space-occupying, orbital disease with clear signs of inflammatory activity. The ages of affected patients seem randomly scattered, including both small children and mature adults of all ages, including the very elderly. Classification of this heterogeneous group of disorders is based on the anatomical structures affected, and includes five subtypes (locations deter- mined by MR imaging): a scleritic form, a dacryoade- nitic form, a diffuse form, a myositic form (see below), and an apical form that also often involves the cavern- ous sinus (Tolosa-Hunt syndrome).

Ocular myositis affects primarily younger patients and is

recognizable by its abrupt onset with a painful restriction

of eye movement caused by a swollen rectus muscle. Curi-

ously, this is usually confined to just one muscle. Ocular myositis is often marked by visible hyperemia in the ante- rior segment of the eye, directly over and around the tendi- nous insertion of the affected muscle. Inflammatory orbital diseases are often accompanied by associated signs, such as lid swelling, ptosis, and/or exophthalmos. In a few cases, there may be an association with myasthenia gravis or a collagen vascular disease.

Pathogenesis of Idiopathic Orbital Inflammation

The genesis of this disorder is unknown. It is important to note that a number of systemic diseases can produce similar clinical findings. Thus, cases that have an unusual course or that show bilaterality (very uncommon for “or- bital pseudotumor”) should trigger the diagnostician’s con- sideration of other disease categories.

Diagnosis

Frequently, the typically quick clinical response to systemic corticosteroid therapy helps to support the diagnosis.

When the clinical presentation is ambiguous, a CT scan is essential. For cases with discrete findings limited to one area of the orbit, an MRI scan is preferred. When Tolosa- Hunt syndrome is suspected, an MRI is obligatory. The echographic signs in orbital myositis are pathognomonic.

There is distention of the muscle belly, but also of the tissues at the tendinous insertion. This pattern of inflammation in an orbital muscle is never caused by Graves’ disease.

The differential diagnosis includes lymphoma, sarcoid- osis, tuberculosis, luetic disease, Wegener’s granulomato- sis, or several types of vasculitis. Wegener’s granulomatosis is a generalized necrotizing vasculitis with ocular involve- ment in 40% of cases – most often in the form of axial pro- ptosis (with associated scleritis or retinal vasculitis), but also as a form of myositis. Laboratory testing can help to establish the diagnosis of this autoimmune disease, if the c-ANCA (antineutrophile cytoplasmic antibody) shows cytoplasmic staining. The test is often negative in the early stages of the disease and should be repeated periodically, if the diagnosis is strongly suspected.

In uncertain cases or those in which a relapse occurs, a biopsy of the affected orbital tissues can be helpful. The his- tologic features are not pathognomonic and by themselves cannot establish the diagnosis. They can be highly varied in their appearance and are of value primarily when they can specifically identify such disorders as vasculitis or granulo- matous diseases. Otherwise, the biopsy can help to relieve the uncertainty the process might be a secondary inflam- mation in the border region surrounding a neoplasm.

Treatment

Corticosteroids are the drugs of choice. Other immuno- suppressants are not as effective. As a rule, when the diag- nosis is first established, steroid therapy should start im- mediately (1 mg/kg of prednisone per day, slowly tapering the dose over an 8- to 12-week period).

! ^Note

A lymphoma would also respond initially to this treat- ment, for which reason a very careful monitoring of the patient’s course is essential.

A repeatedly relapsing course of the disease, or a case in which corticosteroids are contraindicated, can be very dif- ficult to manage. Most helpful in such cases is the use of orbital irradiation, or in some instances the use of surgical debulking can be considered. For Wegener’s granulomato- sis, treatment that combines the use of cyclophosphamide and corticosteroids will produce a remission in 90% of cases.

Orbital Cellulitis

Orbital cellulitis is characterized by the typical triad of exophthalmos, eyelid swelling, and limited ocular motility.

The latter feature distinguishes orbital cellulitis from the more limited case of cellulitis of the lid, in which the eye’s movements are unrestricted, and the prominence of the eye is confined to the tissues external to the orbital septum.

This can be difficult to judge when the lid swelling is so pronounced that the eye cannot be seen. There is usually an associated fever, a leukocytosis, and history of repeated bouts of bacterial sinusitis. Such cases must be managed quickly and aggressively with hospitalization, intravenous antibiotics, and surgical incision and decompression of the swollen orbital tissues.

! ^Note

Orbital cellulitis carries a high risk of progression to a septic cavernous sinus thrombosis, since the veins and venous sinuses of the brain have no valves to limit the spread of sepsis.

In almost all cases, a CT scan of the paranasal sinuses will

be needed. When there is no favorable response to antibi-

otic treatment, the possibility of trauma with an occult

intraorbital foreign should be considered. In immunocom-

promised patients or those with diabetes mellitus, one

should think of a possible mucormycosis, a condition with

an extremely poor prognosis.

Orbital Varix

A varix is most often associated with a variable exophthal- mos that changes with body position or with variations in intrathoracic pressure and has no audible bruit. This distin- guishes a varix from a carotid–cavernous fistula. The prob- lem most often manifests itself during the first or second year of life. The varix can be variably positioned deep with- in the orbit or in the subcutaneous tissues anterior to the orbital septum.

Occasionally acute and rapid increases in size (by thrombosis in or hemorrhage around the varix) mark the first presentation of the disorder. Despite this dramatic ap- pearance, damage to vision by compression of the optic nerve is extremely uncommon.

The underlying genesis is thought to lie in a congenital venous malformation. A varix can be identified by using Valsalva maneuvers, ultrasonography, CT scanning, or MRI. Usually no treatment is necessary. Only in cases of ocu- lar or neural compression by acute hemorrhaging is it nec- essary to use surgical decompression. Identification and excision of the varix can be extremely difficult, and is not usually indicated.

Paranasal Sinus Disorders with Orbital Involvement

The clinical changes are determined in part by the site of the affected sinus and the disease process it contains (whether the disease is inflammatory or neoplastic infil- trating or space occupying). A benign form of space-oc- cupying disease is the mucocele. A mucosal cyst is formed, initiated by obstruction of the affected sinus, that grows steadily larger, wearing through a bony defect in the sinus wall (pressure atrophy of bone by the steadily expanding mucoid cyst) until it begins to expand within the orbit, causing slowly increasing pressure on all of the orbital con- tents. There usually is a history of past sinus surgery, some- times years ago. The most common malignancy to invade the orbit in this manner is squamous cell carcinoma.

The workup should include a consultation with an ear, nose, and throat surgeon, a CT scan and/or an MRI (thin sections with the highest available levels of image resolu- tion). Treatment is determined by the nature of the under- lying problem.

Cavernous Sinus Disease Affecting the Orbit As a rule, lesions within the cavernous sinus produce com- plex disorders of ocular motility, simultaneously affecting more than one cranial nerve. The abducens nerve and the postganglionic fibers of the sympathetic pathway are more severely affected. In contradistinction to the cranial nerves that are protected within the lateral wall of the cavernous sinus (third, fourth, and fifth) the sixth nerve is suspended within the sinus, where it can be damaged most easily. An abducens palsy that is accompanied by an ipsilateral Horn- er’s syndrome most commonly reflects the presence of an intracavernous disease process. A cavernous sinus menin- gioma arising in the lateral wall of the cavernous sinus usu- ally presents as a chronic, slowly progressive loss of third nerve function with signs of aberrant regeneration. Addi- tional signal symptoms of disease in this region include loss of somatic sensation in V

and V

(see Chap. 10). A carotid–cavernous fistula can be clinically dramatic, caus- ing a pulsating proptosis with a strikingly red eye (high orbital venous pressure with “arterialization” of the epi- scleral veins).

Presentation with Enophthalmos

Orbital disorders that cause an enophthalmos are relatively uncommon, when compared with the frequency of exoph- thalmic disorders. They are collectively summarized here.

Clinically, they present as a monocular process in which the eye has receded into the orbit, as compared with the position of the contralateral eye. Depending on the extent of the posterior displacement of the globe, a deeper sulcus above the upper eyelid will be evident.

Measurements taken with the exophthalmometer per- mit an objective assessment of the findings. In cases where there is no ready explanation (i.e., no microphthalmos, phthisis, or history of an orbital floor fracture) an orbital imaging study is mandatory. Enophthalmos can be a sign of orbital scarring by a metastatic, sclerosing carcinoma.

The latter is most commonly a carcinoma of the breast.

Management is again dictated by the nature of the prob- lem.

! ^Note

A pseudoenophthalmos (sometimes referred to as ap- parent enophthalmos) is a characteristic sign of Horn- er’s syndrome (see Chap. 5).

see also Post er 10.1

Conclusion

Orbital diseases require a particularly complex differential diagnosis: aside from the customary routine tests, a de- tailed evaluation by a neuro-ophthalmologist is essential (with emphasis on pupillary motility, visual field examina- tion, and tests of ocular motility). The purpose is to differ- entiate local ocular or orbital disorders from progressive diseases that may damage vision or be fatal.

Further Reading

Dutton JJ (1994) Clinical and surgical orbital anatomy. Saunders, Phila- delphia

Rootman J (ed) (2003) Diseases of the orbit. Lippincott, Philadelphia Stewart WB (1993) Surgery of the eyelid, orbit, and lacrimal system. In:

Ophthalmology monographs no. 8, vol. 1. American Academy of Ophthalmology, San Francisco

Zide BM, Jelks GW (1985) Surgical anatomy of the orbit. Raven, New

York