Ординатура / Офтальмология / Английские материалы / Tumors of the Eye and Ocular Adnexa_Char_2001

280 TUMORS OF THE EYE AND OCULAR ADNEXA

disc edema in 28 percent of cases.19 On long-term follow-up, approximately 5 percent had some deterioration of vision, 75 percent had an enlarged blind spot, 20 percent had arcuate scotomas, and 30 percent had an afferent pupil defect.18,19 Clinical examples of optic nerve melanocytomas are shown in Figures 14–2 and 14–3.

Tumor borders may be sharp or, more commonly, fibrillar due to infiltration of the nerve fiber layer. Joffe and colleagues reported on 40 optic disc melanocytomas. The mean age at diagnosis was 50 years. Fifteen of the 40 patients were African American; 29 had a vision of 6/9 or better. In 10 of 40 cases there was overlying orange pigmentation. In 88 percent, the tumor was < 3 mm in diameter. With serial follow-up data, 4 of 27 patients had tumor enlargement.20 Malignant transformation is extremely rare.21

Virtually all optic nerve melanocytomas can be observed without intervention. The author has seen two cases of malignant degeneration. In one case, a mainly amelanotic melanoma arose from a typical melanocytoma and involved a significant area of peripapillary choroid (Figure 14–4). Other authors have reported both melanocytomas with malignant degeneration and primary optic nerve melanomas with posterior extension along the nerve.22–25 Pigmented adenomas of the optic disc can also sometimes mimic either a melanoma or a melanocytoma.26,27

Figure 14–4. Case of malignant degeneration. The amelanotic melanoma appears to have arisen from a typical melanocytoma and there is a significant area of peripapillary choroid involved.

MELANOMA

Juxtapapillary melanomas can simulate an optic nerve inflammation or a primary optic nerve tumor. Figure 14–5 shows a circumferential peripapillary melanoma, initially misdiagnosed as an optic neuritis. While there is a slight statistical increase in tumor-related mortality associated with melanomas around the optic nerve, these tumors are not associated with significantly increased tumor-related mortality, unless the tumor actually compresses the nerve, with marked diminution of vision.28 The management of these tumors is discussed in Chapter 8 on posterior uveal tumors.27

METASTASES

Occasionally, metastases will initially involve just the optic nervehead. These are much less common than metastatic deposits in the uveal tract and occur with the same frequency as those involving the vitre- ous.29–31 An example of a bronchiogenic carcinoma metastatic to the optic nervehead is shown in Figure 14–6A; the accompanying fluorescein angiogram is shown in Figure 14–6B. Figure 14–7 shows a breast carcinoma metastatic to the optic nerve. As at other sites, optic nerve metastases are often responsive to external beam photon irradiation.

Optic nerve infiltration as a result of acute lymphocytic leukemia is discussed in the chapter on lymphoid lesions.32,33 Figure 14–8 shows an axial computed tomography (CT) scan of a lymphoma that involved both the optic nerves and clinically

A

B

Figure 14–7. Breast carcinoma metastatic to the optic nerve.

simulated the intraocular appearance of leukemic optic nerve infiltrate. As previously discussed, both optic nerve gliomas and optic nerve sheath meningiomas can invade the eye and produce intraocular involvement.34,35 Juvenile xanthogranuloma and malignant medulloepitheliomas have also rarely involved the optic disc; the latter tumor can produce mortality from contiguous spread to the central nervous system (CNS).5,36 Figure 14–9 shows a glial proliferation (confirmed on fine-needle aspiration biopsy) in a young boy who had sarcoid involving the eye. Figure 14–10 demonstrates an optic nerve proliferation in a patient with malignant histiocytosis.

Figure 14–6. A, Bronchiogenic carcinoma metastatic to the optic nervehead. B, Fluorescein angiogram of the same eye.

Figure 14–8. Axial CT demonstrates bilateral involvement of the optic nerves. This patient had the fundus pattern that simulated a leukemic optic nerve infiltrate.

ANGIOMAS

Angiomas are discussed in the chapter on retinal tumors. In any patient with either a retinal or optic nerve hemangioma, the diagnosis of von HippelLindau syndrome should be ruled out with CNS magnetic resonance imaging (MRI) scans and either MRI or CT of the abdomen and pelvis. Molecular genetic testing is also helpful, although the optimum strategy of such testing is still uncertain.37

Angiomas uncommonly involve the optic disc and in those rare circumstance, most patients have the von Hippel-Lindau syndrome. The diagnosis of an optic disc angioma is straightforward and these

lesions have the classic appearance clinically (see Figure 14–1 and Figure 14–11) and have early fluorescence with leakage on angiography. The management of such cases is difficult. Laser has generally not been very effective and is associated with significant morbidity. In patients with CNS hemangioblastomas, various forms of radiation have been effective.38 We have treated a few optic nerve head angiomas with low-dose, high-fraction radiation either with a Gamma Knife or protons.

A number of other nononcologic processes can produce optic nervehead enlargement, and these are discussed in neuro-ophthalmology textbooks. Other common lesions that could be confused for a neo-

plastic process include acute anterior optic neuropathy (AION), buried optic nerve drusen (Figure 14–12), and tuberous sclerosis involving the disc. An idiopathic inflammation of the disc is shown in Figure 14–13. This lesion spontaneously resolved. Figure 14–14 shows an intraocular foreign body referred to as an optic disc tumor. Rarely, a vascular tumor, such as a cavernous hemangioma, can be localized to the disc.42

REFERENCES

1.Wertz FD, Zimmerman LE, McKeown CA, et al. Juvenile xanthogranuloma of the optic nerve, disc, retina, and choroid. Ophthalmology 1982;89:1331–5.

2.Grimson BS, Perry DD. Enlargement of the optic disc in childhood optic nerve tumors. Am J Ophthalmol 1984;97:627–31.

3.Henderson JW, Campbell RJ. Primary intraorbital meningioma with intraocular extension. Mayo Clin Proc 1977;52:504–8.

4.Rosenthal AR. Ocular manifestations of leukemia. A review. Ophthalmology 1983;90:899–905.

5.Reese AB. Medulloepithelioma (of the optic nerve). Am J Ophthalmology 1957;44:4–6.

6.Green WR, Iliff WJ, Trotter RR. Malignant teratoid medulloepithelioma of the optic nerve. Arch Ophthalmol 1974;91:451–4.

7.Luiz, JE, Lee AG, Keltner JL, et al. Paraneoplastic neuropathy and autoantibody production in small-cell carcinoma of the lung. J Neuro-ophthalmol 1998; 18:178–81.

8.Reidy JJ, Apple DJ, Steinmetz RL, et al. Melanocy-

toma: nomenclature, pathogenesis, natural history and treatment. Surv Ophthalmol 1985;29:319–27.

9.Hirschberg J. Ueber die angeborne Pigmentirung der Sclera und ihre pathogenetische Bedeutung. Albrecht von Graefes Arch Klin Exp Ophthalmol 1883;29:1–12.

10.Coats G. Congenital pigmentation of the papilla. R London Ophthalmol Hosp Rep 1907;17:225–31.

11.Palich-Szanto O. Zwei seltene Befunde am Sehnervenkopfe. Klin Monatsbl Augenheilkd 1915;55: 149–57.

12.Lauber H. Ein Fall von Sarkom der Papille, seit 19 Jahren i Beobachtung. Klin Monatsbl Augenheilkd 1923;71:776.

13.Kreibig W. Das Epipapillaere Melanom. Klin Monatsbl Augenheilkd 1949;115:354–9.

14.Zimmerman LE. Pigmented tumors of the optic nervehead (22nd annual de Schweinitz lecture). Am J Ophthalmol 1960;50:338.

15.Zimmerman LE, Garron LK. Melanocytoma of the optic disc. Int Ophthalmol Clin 1962;2:431–40.

16.Walsh TJ, Packer S. Bilateral melanocytoma of the optic nerve associated with intracranial meningioma. Ann Ophthalmol 1971;3:885–8.

17.Takahashi T. Klinische und histopathologische Beobachtungen beim Melanozytom der Papille. Klin Monatasbl Augenheilkd 1979;175:47–55.

18.Osher RH, Shields JA, Layman PR. Pupillary visual field evaluation in patients with melanocytoma of the optic disc. Arch Ophthalmol 1979;97:1096–9.

19.Brown GC, Shields JA. Tumors of the optic nervehead. Surv Ophthalmol 1985;29:248–64.

20.Joffe L, Shields JA, Osher RH, Gass JD. Clinical and follow-up studies of melanocytomas of the optic disc. Ophthalmology 1979;86:1067–83.

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21.Apple DJ, Craythorn JM, Reidy JJ, et al. Malignant transformation of an optic nerve melanocytoma. Can J Ophthalmol 1984;19:320–5.

22.Erzurum SA, Jampol LM, Territo C, O’Grady R. Primary malignant melanoma of the optic nerve simulating a melanocytoma. Arch Ophthalmol 1992;110: 684–6.

23.Shields JA, Shields CL, Eagle RC Jr, et al. Malignant melanoma associated with melanocytoma of the optic disc. Ophthalmology 1990;97:225–30.

24.De Potter P, Shields CL, Eagle RC, et al. Malignant melanoma of the optic nerve. Arch Opthalmol 1996;114:608–12.

25.Meyer D, Ge J, Blinder KJ, et al. Malignant transformation of an optic disk melanomacytoma. Am J Opthalmol 1999;127:710–4.

26.Shields JA, Eagle RC Jr, Shields CL, De Potter P. Pigmented adenoma of the optic nerve head simulating a melanocytoma. Ophthalmology 1992;99:1705–8.

27.Loose IA, Jampol LM, O’Grady R. Pigmented adenoma mimicking a juxtapapillary melanoma. A 20-year follow-up. Arch Ophthalmol 1999;117: 120–2.

28.Weinhaus RS, Seddon JM, Albert DM, et al. Prognostic factor study of survival after enucleation for juxtapapillary melanomas. Arch Ophthalmol 1985; 103:1673–7.

29.Char DH, Schwartz A, Miller TR, Abele JS. Ocular metastases from systemic melanoma. Am J Ophthalmol 1980;90:702–7.

30.Fishman ML, Rosenthal S. Optic nerve metastasis from a mediastinal carcinoid tumor. Br J Ophthalmol 1976;60:583–8.

31.Sung JU, Lam BL, Curtin VT, Tse DT. Metastatic gastric carcinoma to the optic nerve. Arch Ophthalmol 1998;116:692–3.

32.Nikaido H, Mishima H, Ono H, et al. Leukemic involvement of the optic nerve. Am J Ophthalmol 1988;105:294–8.

33.Preti A, Kantarjian HM. Management of adult acute lymphocytic leukemia: present issues and key challenges. J Clin Oncol 1994;12:1312–22.

34.de Keizer RJ, de Wolff-Rouendall D, Bots GT, et al. Optic glioma with intraocular tumor and seeding in a child with neurofibromatosis. Am J Ophthalmol 1989;108:717–25.

35.Miller NR. Primary optic disc tumors. In: Walsh F, Hoyt WF, editors. Clinical Neuro-Ophthalmology. Baltimore, MD: Williams and Wilkins; 1982. p. 265–9.

36.O’Keefe M, Fulcher T, Kelly P, et al. Medulloepithelioma of the optic nerve head. Arch Ophthalmol 1997;115:1325–7.

37.Pack SD, Zbar, B, Pak, E, et al. Consitutional von Hip- pel-Lindau (VHL) gene deletions detected in VHL families by fluorescence in situ hybridization. Cancer Res 1999;59:5560–4.

38.Patrice SJ, Sneed PK, Flickinger JC, et al. Radiosurgery for hemangioblastoma: results of a multiinstitutional experience. Int J Radiat Oncol Biol Phys 1996;35:493–9.

39.Laties AM, Scheie HD. Sarcoid granuloma of the optic disc: evolution of multiple small tumors. Trans Am Ophthalmol Soc 1970;68:219–33.

40.Beardsley TL, Brown SV, Sydnor CF, et al. Eleven cases of sarcoidosis of the optic nerve. Am J Ophthalmol 1984;97:62–77.

41.Jampol LM, Woodfin W, McLean EB. Optic nerve sarcoidosis. Report of a case. Arch Ophthalmol 1972; 87:355–60.

42.Mansour AM, Jampol LM, Hrisomalos NF, Greenwald M. Case Report. Cavernous hemangioma of the optic disc. Arch Ophthalmol 1988;106:22.

Effective management of orbital neoplasms requires the ophthalmologist to delineate the nature of the lesion, determine whether intervention is necessary, and decide on the optimal therapy. For example, proptosis in children is managed differently from that in adults, since rapid intervention is often necessary in children with exophthalmos. Children are more likely than adults to have either a rapidly growing malignant orbital tumor or contiguous spread of an infectious sinusitis; either can result in blindness or loss of an eye, if the process is not treated rapidly. Conversely, most causes of adult proptosis are relatively chronic and usually do not require rapid intervention.1,2 The most common orbital tumors are listed in Table 15–1.

In addition to patient age, subjective data (history of present illness, past medical history, and review of systems), physical findings, and tumor location (based on imaging data) are important in establishing a differential diagnosis. Computed tomography (CT) or magnetic resonance imaging (MRI) data can be used to categorize orbital tumefactions into those that involve only a single orbital structure (optic nerve, lacrimal gland, orbital bones, or extraocular muscles) in the intraconal area, the extraconal space, the entire orbit, or both the orbit and contiguous structures. In order to establish an optimal differential diagnosis, extraconal lesions should be divided into those that involve the lacrimal fossa, those that are anterior to the orbital septum, those that involve bone, those that involve multiple orbital compartments and/or adjacent sinuses, globe, and those that involve the central nervous system (CNS). Establishing a differential diagnosis on the basis of the history, clinical findings, and imaging data results in histologic confirmation in over 97 percent of cases.

In children, most orbital lesions occur either prior to age 2 years or after age 6 years and are more likely to have a more fulminant disease course than adult lesions. In the age group < 2 years, capillary hemangiomas, cysts, or malignancies, (orbital metastases, leukemia, or rhabdomyosarcoma) are the most common causes of proptosis. Langerhan’s histiocytosis syndromes (unior multifocal histiocytosis, including eosinophilic granuloma, Hand-Schuller-Christian, or Letterer-Siwe syndrome), congenital craniofacial abnormalities, and traumatic or developmental cysts occur. Rare tumors, such as contiguous retinoblastoma (rare in the United States), teratomas, orbital cysts or melanocytic proliferations, may also occur. Sinusitis with secondary involvement of the orbit is uncommon in those age < 3 years, since the sinuses are not completely developed or aerated; the author has seen only two children in this younger age group with infective orbital-sinus disease. In the older children, the most common orbital problems are infective sinusitis and rhabdomyosarcoma. Lymphoid lesions, lymphangioma, orbital metastases, and adult tumors can occur in older children.

In adults, the most common cause of unilateral or bilateral proptosis is thyroid eye disease.2 As discussed elsewhere, many of these patients will have normal serum levels of thyroxine (T4) and triiodothysonine (T3) when they present with proptosis.3 The appropriate first-line tests, if thyroid orbitopathy is suspected, are serum thyroid stimulating hormone (TSH) and thyroid antibodies. Most adult orbital tumors are benign, and orbital pseudotumors, benign cystic lesions (dermoids, mucoceles, inclusion cysts) and cavernous hemangiomas are relatively common.

Optic Nerve and Nerve Sheath

Optic nerve glioma

Optic nerve sheath meningioma

Extraocular extension of retinoblastoma

Extraocular extension of uveal melanoma

Leukemic infiltrate

Metastatic carcinoma

Inflammatory lesions (pseudotumor)

Extraocular Muscles Metastatic tumors Rhabdomyoma Rhabdomyosarcoma Lymphoma

Alveolar soft part sarcoma Thyroid-related myositis Idiopathic myositis

Inflammation as a component of orbital pseudotumor Amyloidosis

Carotid artery: cavernous sinus fistula

Lacrimal Fossa Epithelial tumors

Benign mixed tumor (“pleomorphic adenoma”) Adenoid cystic carcinoma

Mixed carcinoma Adenocarcinoma

Lymphoma

Metastases Dermoid cysts

Infectious inflammation (lues, tuberculosis, mumps, viral) Pseudotumor

Orbital Bones

Developmental bone abnormalities/alterations Axial myopia

Fibrous dysplasia Osteopetrosis

Craniofacial malformations Neurofibromatosis

Mass lesions

Epidermoid and dermoid cysts Hematic bone cyst Aneurysmal bone cyst Ossifying fibroma

Mucoceles Osteosarcoma Fibrosarcoma Metastases

Contiguous sinus malignancies

Benign and malignant histiocytosis syndromes

Intraconal Lesions Benign tumors

Cavernous hemangioma Hemangiopericytoma Neurofibroma

Neurilemmoma Malignant tumors

Malignant hemangiopericytoma Metastases

(See optic nerve tumors)

Extraconal Lesions Lymphoid lesions

Lymphoma Pseudotumor Leukemia

Metastases

Epidermoids

Capillary hemangioma Varices Lymphangiomas

Inflammation from contiguous sinusitis

The evaluation of any patient suspected of having an orbital neoplasm includes a thorough history of the present illness, past medical history, and a review of systems. Emphasis should be on thyroid disease, systemic malignancies, inflammatory sinus disease, and systemic inflammatory diseases (eg, Sjögren’s syndrome, sarcoid, tuberculosis, rheumatoid arthritis, Wegener’s granulomatosis). Some nontumefactions, including congenital facial asymmetry, traumatic enophthalmos, unilateral axial myopia, carotid artery-cavernous sinus fistulae, infection, or inflammation, can mimic an orbital tumor and should be ruled out.

In general, I limit my evaluation to a routine ophthalmic examination, unless there are 72 mm of proptosis, significant visual loss, diplopia, conjunctival or lid swelling, or ptosis in conjunction with a lesser degree of exophthalmos.

Most orbital tumefactions with the exception of rhabdomyosarcoma, some metastases, and, rarely, hemorrhagic primary tumefactions have an insidious onset.4,5 A few physical findings are diagnostically helpful. Bilateral proptosis, in conjunction with scleral show and lid lag, is virtually pathognomonic for thyroid ophthalmopathy. Opticociliary shunt vessels in middle-aged females with minimal proptosis and profound visual loss strongly suggest an optic nerve sheath meningioma. Scleritis, in association with proptosis, is most often observed in orbital pseudotumor, but primary and metastatic malignancies can also produce this finding. Arteriolarization of conjunctival vessels in association with acute unilateral proptosis in an adult is characteristic of a dural or carotid-cavernous sinus fistula.6,7 Most signs of orbital disease are not diagnostic for a specific type of orbital tumor. The location of a tumor,

the presence or absence of exophthalmos or enophthalmos, choroidal folds, anterior chamber angle neovascularization, optic nerve inflammation or atrophy, or most other physical findings do not establish a specific diagnosis.8,9

Choroidal folds were first described clinically in 1884, and initially most investigators felt they were a sign of orbital disease (Figure 15–1).10 Norton differentiated between retinal and choroidal folds; Cangemi and co-workers found that only 10 of 53 patients with choroidal folds had them on the basis of an orbital etiology.8,11 Other causes of choroidal folds include hypermetropia, macular degeneration, retinal detachment, hypotony, trauma, scleritis, uveitis, and ocular tumors of unknown etiology.8

Enophthalmos is associated with < 5 percent of orbital problems.12 The mechanisms of orbital retraction are fat atrophy, traction or structural abnormalities. Most frequently, enophthalmos is due to trauma followed by scirrhous carcinoma and less commonly microphthalmos, orbital varices, barotrauma, mucoceles, sinusitis, or prior orbital surgery.

Displacement of the globe (straight ahead, infe- rior-medial, lateral) may help to ascertain the location of an orbital tumor (intraconal, lacrimal fossa, and sinuses, respectively) and hence establish a differential diagnosis on the basis of location; either CT or MRI is much more accurate than physical examination to delineate the tumor’s relationship to normal structures. Alterations in proptosis as a function of bending over, vascular pulsations, or a positive Valsalva maneuver may help to ascertain the vascular nature of the lesion. The mass itself may be palpable, depending on its location in the orbit. Generally, palpation of the mass is not too helpful in ascertaining its histologic nature. Pseudotumors, fibrous tumors, and malignancies are generally firm, while vascular or cystic lesions are compressible.

An overview of orbital diagnosis and management is presented here and in detail in the following chapters. This chapter reviews the use of imaging techniques and fine-needle aspiration biopsy (FNAB) in the diagnosis, evaluation, and management of patients with orbital tumefactions. The following chapter discusses the diagnosis and management of the most common pediatric orbital diseases. Chapters after that summarize data available regarding the presentation

and management of the most common adult orbital neoplasms. In those chapters, adult orbital tumefactions have been arbitrarily organized into lesions involving the optic nerve alone, intraconal space, and extraconal space. Those in the extraconal space have been divided into lesions which involve predominantly the sinuses, lacrimal fossa, and lacrimal sac. Orbital metastases and orbital lymphoid lesions that most commonly involve the extraconal space but can involve any area of the orbit are discussed separately. Orbital radiation and surgical approaches are covered at the end of the book.

ORBITAL IMAGING

General Principles

There are several areas where orbital imaging techniques have improved the management of orbital diseases. First, CT, MRI, and ultrasonography (US) scans have markedly improved diagnostic accuracy in the evaluation of orbital masses. Second, these cross-sectional imaging techniques (CT and MRI) are useful to determine whether any therapeutic intervention is necessary and, if so, the rapidity of treatment. Third, multiplanar CT or MRI data are helpful in determining the optimal surgical or radiation therapy by delineating the relationship of the lesion to contiguous orbital and adjacent eye, sinus,

Figure 15–1. Choroidal folds.

288 TUMORS OF THE EYE AND OCULAR ADNEXA

or CNS structures. Fourth, these techniques can be amalgamated with FNAB to improve diagnostic accuracy. Finally, noninvasive imaging techniques are invaluable for the serial evaluation of a patient prior to or after treatment.

CT and MRI are cross-section imaging techniques. One-to two-millimeter thick axial and/or coronal CT sections provide superb anatomic detail (spatial resolution). Data from sections obtained in one plane, usually axial, can be reformatted in any other plane through computer manipulation of the data to further increase diagnostic accuracy and more accurately predict the lesion location and histology.2,4 Prior to the availability of CT, the ability to detect an orbital mass with plain radiography was between 21 and 39 percent.6,7,13 The accuracy of CT diagnosis has progressively increased with newer equipment and better techniques from 60 to over 95 percent.2,6,8 The CT image is often sufficiently characteristic to obviate the need for orbital biopsy.

In contrast to projection radiographs (plain films) that image bone, CT can directly image orbital soft tissue abnormalities. On CT, structures of varying tissue density can be distinguished on the basis of differential X-ray absorptions. These densities are imaged relative to the density of water. Retro-orbital fat absorbs X-rays to a lesser degree than water; it is displayed on the CT as a black (low-density) area that contrasts with the whiter (higher-density) extraocular muscles and the optic nerve. The ability of CT to differentiate these tissues is due to their relative contrast differences, which range as high as 14 percent. Modern scanners can distinguish tissues with < 1 percent contrast difference.

The presence of retrobulbar fat allows high spatial and density resolution of orbital structures on CT, often without the need for intravenous contrast material. Orbital fat has required the use of fat saturation techniques combined with contrast (gadolinium) to allow similar enhancement and contrast of orbital tumors with fat in MRI scans. In lesions of the optic nerve, its sheath, or processes that involve the contiguous CNS, MRI, often with fat saturation and gadolinium enhancement, has improved detection rates over CT.

Orbital CT scans are routinely performed using 1- to 1.5-mm thick sections at 1-mm intervals in the

axial plane. This provides high spatial detail in the X, Y, and Z axes. The individual picture or volume elements (voxels) in these axial slices can then be reformatted (re-arranged) in any plane to provide coronal, sagittal, and para-axial or parasagittal oblique images. These reformatted images are generated after the patient has left the scanner. They do not require additional patient exposure to ionizing radiation. In most centers, the lens dose from orbital CT is approximately 18.5 mGy.14 Coronal re-formations decrease the high spatial frequency artifacts (eg, from dental appliances) that are often encountered with direct coronal scans. The use of multiplanar re-formations enables the radiologist and ophthalmologist to view a lesion of interest in an optimal anatomic plane and to assess its location relative to contiguous orbital, bone, sinus, and CNS structures. A basic principle of both geometric and computed tomography is that an object should be imaged perpendicular to the plane in which it lies; this can be readily accomplished with multiplanar re-formation techniques. There are occasions when direct coronal scans are useful, such as orbital blow-out fractures and craniofacial neoplasms. In orbital series, the false-negative and falsepositive rates with CT scans were < 3 percent and < 5 percent, respectively.2,5–9 CT scanning of the orbits is usually performed without the use of intravenous contrast agents. However, contrast enhancement may be useful in delineating intracranial spread of malignancies. As discussed below, this appears to be the optimal accuracy available with this technology.

Figure 15–2 demonstrates, on a modern scanner, the anatomic detail which is obtained routinely with 1-mm thick sections. In this axial scan through the superior portion of the orbit, one can discern the globe, lacrimal gland, superior ophthalmic vein, and supratrochlear vein.

Older equipment yields suboptimal images with inferior spatial and density resolution. A normal CT study performed on inferior equipment provides only a false sense of security. Optimum CT data are also dependent on proper examination technique; the entire orbit, or at least the area of interest, must be scanned using thin sections at the correct angulation to obtain useful data. Neuroradiologists and ophthalmic surgeons can use these scanners to increase diagnostic accuracy.

Figure 15–2. Anatomic detail on a 1.5 mm axial section. Superior ophthalmic vein (SOV). (From Char DH, Norman D. The use of computed tomography and ultrasonography in the evaluation of orbital masses. Surv Ophthalmol 1982;2:49–63.)

Improvement in both resolution and the ability to perform multiplanar re-formations has increased the importance of CT and has diminished our use of ultrasonography (US).3 The addition of MRI has further limited the role of US in these diseases. CT has also had a major impact on treatment planning. As discussed in the final chapter of the book, especially for external beam radiation simulation, CT has probably resulted in as high as a 30 percent improvement in the accuracy of field placement.

The development of spiral (helical) CT techniques have been very helpful, especially in pediatric cases where the rapid data collection results in being able to obtain scans without anesthesia.15,16 This technique is also quite important in some orbital lesions in which the effect of a Valsalva maneuver is to be assessed or in those patients who are quite ill and require a rapid scan.

Optimal visualization of the relationship of tumor with contiguous normal structures is vital in determining both the surgical approach and the need for ancillary therapy. In orbital lesions that require surgical intervention, CT re-formations or multiplanar MRI sequences permit a more accurate preoperative determination of the extent of tumor involvement. They also facilitate planning for the most appropriate surgical approach as well as the extent of surgery required.

Ultrasonography

We have almost eliminated the use of orbital US due to improvements in CT and MRI. A combination of quantitative echography with a Kretz A-scan and immersion B-scan ultrasound can be used to detect the presence of some orbital lesions and predict their histologic pattern on the basis of US characteristics of a tumor’s surface and shape. The characteristics shown could be regular, irregular, with smooth or ragged edges, encapsulated or nonencapsulated, infiltrative, or focal, and the internal tumor pattern could be cystic, vascular, or solid with various patterns of internal reflectivity.

If a superb ultrasonographer is present, then US is a cost-effective screening test for some anterior and midorbit disease.11 While some authors have felt that US might be as good as or better than CT or MRI in the diagnosis of midorbital changes, a study by Demer and Kerman outlined some of the limitations of US, compared with MRI.11 In anterior orbital and intraconal lesions, US appears to be as accurate as CT or MRI in detecting and predicting the histology of an orbital mass.17–22 Unfortunately, in a proptotic patient, a major reason to obtain a scan is to plan therapy, and for that purpose, US is distinctly inferior to both MR and CT.

There are a number of other disadvantages of US, compared with either CT or MRI. The quality of US examination is directly related to the orbital experience of the ultrasonographer. First, most CT and some MRI protocols are now sufficiently automated so that if good equipment is available, an excellent scan will be uniformly produced. Second, we previously obtained both US and CT in all orbital tumor cases, and US was not found to add significant information to high-resolution, thin-sec- tion CT. Third, the anatomic detail available with either CT or MRI, especially the graphic demonstration of the relationships between the tumor and adjacent structures is far superior and easier for the clinician to use than US. Fourth, for many orbital lesions, especially those that involve contiguous bone, brain, sinus, or lesions in the orbital apex, US is far less sensitive and accurate than CT or MRI. While the predictive accuracy of tissue characterization with echography has been highly touted, it is