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Show / ounu> 1 of Clinical Nt'un'-" l'htha/ rlll, logy 9( 2): 122- 125. 1989. Gadolinium- DIPA Enhancement of an Optic Nerve and Chiasmal Meningioma Barrett G. Haik, M. D., Robert Zimmerman, M. D., and Leslie Saint Louis, M. D. © 1989 Raven Press, ltd., New York The advent of gadolinium- diethylenetriaminepentaacetic acid ( Gd- DTPA), a magnetic resonance imaging ( MRI) contrast agent, has significantly improved MRl's diagnostic accuracy by enabling the physician to separate magnetically similar but histologically different tissues. A patient with optic nerve meningioma, whose tumor was clearly demonstrated on Gd- DTPA- enhanced MRI but did not appear on noncontrast MRl, is described. The usefulness of contrast agents in MRl diagnosis of neuro- ophthalmologic disorders and ophthalmic tumors is emphasized through this case report. Key Words: Optic nerve-- Meningioma- Magnetic resonance imaging- Gadolinium- DTPA. From the Department of Ophthalmology, Tulane University School of Medicine, New Orleans, Louisiana ( B. G. H.), and Department of Radiology, Cornell University Medical College, New York, New York ( R. Z., L. S. L.). Address correspondence and reprint requests to Dr. B. G. Haik ,11 Departm.. nt (, f Ophthalmologv, Tulane University ; I.,~,( ,,,,,. Nt'\\' OrleJns, LA 122 Magnetic resonance imaging ( MRI) is a powerful diagnostic tool employed with increasing frequency by the ophthalmic community in the evaluation of neuro- ophthalmologic disorders. The technique is unaffected by bony artifact, permits visualization of any portion of the human body in multiplanar fashion, and involves no ionizing irradiation. The contrast resolution of MRI has proved superior to computed tomography ( CT) in the detection of very subtle pathologic changes of soft tissues; however, routine MRI does not readily detect intracranial tumors, which have isomagnetic properties in relation to brain. The use of the MRI contrast agent gadolinium- DTPA ( Gd- DTPA) greatly facilitates diagnosis in these instances. This case report demonstrates an intracraniallesion readily seen on both Gd- DTPA- enhanced MRI and contrast- enhanced CT, but not detected on routine noncontrast MRI. CASE REPORT A 69- year- old white woman was evaluated for a 4- day history of right orbital pain and proptosis. She reported having lost vision in her right eye 25 years previously. No etiology of the visual loss had been identified at that time, and the patient was otherwise asymptomatic during the intervening period. Visual acuity was 20/ 40 in the left eye and no light perception in the right eye. The pupils were equal in size, but there was no reaction to light in the right eye. While the left eye was unremarkable for further etiology, a relative afferent pupillary defect was present in the right eye, as was severe restriction of movement in all fields of gaze. The globe was displaced 4 mm inferiorly, and a proptosis of 5 mm was noted. Slit- lamp biomicroscopy was notable for corkscrew conjunctival vessels and Gd- DTPA- ENHANCED MRI 123 mild chemosis. The funduscopic examination revealed mild disc edema and opticociliary shunt vessels. Ultrasound revealed elevation of the optic nerve head with concomitant accentuation and widening. Contrast- enhanced CT ( Fig. 1) showed a large, well- defined, and infiltrating right orbital tumor with intracranial extension. Routine MRl identified the right orbital tumor ( Fig. 2); however, the intracranial extension was seen only after injection of Gd- DTPA ( Fig. 3). With use of the contrast agent, changes in imaging parameters, slice thicknesses, or orientations were unnecessary for identification. A lateral orbitotomy was performed, and biopsy of the mass revealed it to be an optic nerve meningioma. The patient received orbital irradiation FIG. 1. A: Contrast- enhanced CT scan demonstrates perioptic enhancing mass. Note the low- density optic nerve seen within the lesion. Anterior to the bulk of the mass, there is the irregular thickening of the optic nerve sheath. B: At a more superior level, the suprasellar intracranial component of the lesion is identified. The anterior component is an area of hyperostosis of the sphenoid bone. Posterior to this is a slightly less dense zone of enhancement. ( 5,000 rad over 4 weeks), and her condition has now been stable for 3 years. CONCLUSION As MRl is being employed with increasing frequency- replacing CT for diagnosis in certain situations- it is important that the physician recognize MRl's limitations as well as advantages. MRl has been of particular value in the examination of patients with neuro- ophthalmologic disorders and ophthalmic tumors that extend intracranially. Usually, these disorders cause changes in the hydration level and fat content, which yield a strong signal on routine scans, facilitating diagnosis. Unfortunately, some intracranial disorders and tumors are not associated with major changes in the amount of myelination or intracranial water and thus have isomagnetic properties in relation to brain. These disorders require more than the routine MR sequences for diagnosis. The recent introduction of MRl contrast agents addresses the difficulty of separating magnetically similar but histologically different tissues and improves the diagnostic efficacy of this technique ( 1). MRl contrast enhancement is most useful for Tj weighted images, especially for lesions that do not delineate well on nonenhanced Tz- weighted images. The paramagnetic enhancement properties of such agents result from the presence of unpaired electrons, which shorten the proton relaxation time. The Gd3 + ion has a strong magnetic movement and is kelated to DTPA to neutralize any associated toxicity ( 2). The injection of these compounds has been noted to increase the signal intensity from intracranial neoplasms ( 3- 6). This occurs because Gd- DTPA concentrates in the tumor after leaking through the defective bloodbrain barrier. It therefore can be used to detect either small or isomagnetic neoplasms that are not easily seen on routine MRI sequences. Additionally, Gd- DTPA permits a more accurate differentiation of neoplastic tissue from surrounding reactive edema, therefore permitting more accurate assessment of the tumor's anatomic borders and of the region requiring therapy. In summary, this case report demonstrates the importance of Gd- DTPA enhancement when MRl is to be the initial diagnostic method used in neuro- ophthalmologic disease. Acknowledgment: This work was supported in part by the St. Giles Foundation, Brooklyn, NY, U. s. A. / Oil! Nfuro- oplltllalmol, Vol. 9. No. 2, 1989 124 B. G. HAIK ET AL. FIG. 2. A: Short repetition time ( TR)/ echo time ( TE) ( 500/ 30) T 1 - weighted images through the orbit demonstrate the intraorbital component of the lesion wall. Note the large mass in the orbital apex and the thickening of the optic nerve anterior to this. The optic nerve cannot be seen within or separated from the tumor. B: At a slightly higher level, short TR/ short TE scans demonstrate no evidence of intracranial involvement. Note the absence of anatomic distortion or intensity abnormality. Neither the hyperostosis nor the enhancing component of the lesion is identified. C: On long TR/ intermediate TE ( 2,000/ 60) T2- weighted image, the intraorbital component of the lesion is identified, but more posteriorly no evidence of intracranial suprasellar abnormality is seen. Gd- DTPA- ENHANCED MRI 125 REFERENCES 1. Runge VM, Clanton JA, Price AC, et al. Evaluation of contrast- enhanced MR imaging in a brain- abscess model. Alii I Neural Radial 1985; 6: 139- 47. 2. Niendorf HP, Felix R, Laniado M, et ai. Cadolinium- DTPA: a new contrast agent for magnetic resonance imaging. Radiation Med 1985; 3: 7- 12. FIG. 3. A: Following administration of Gd- DPTA, scans at the level of the optic nerve demonstrate enhancement of the optic nerve sheath and the tumor. Note that the optic nerve itself does not enhance and can now be visualized as a relative area of low intensity within the tumor. ( On an unenhanced scan, the optic nerve could not be identified since it was isointense to the tumor). B: Short repetition time ( TR)/ short echo time scan at a slightly higher level clearly demonstrates the intracranial component of the lesion anterior to the suprasellar cistern. C: The lesion is also nicely demonstrated on coronal short TR scans where its broad dural base is easily identified as is its location on the planum sphenoidale above the anterior clinoid. 3. Carr DH, Cadian DC. Contrast agents in magnetic resonance imaging. Clin Radial 1985; 36: 561- 8. 4. Craif M, Bydder CM, Steiner RE, et al. Contrast- enhanced MR imaging of malignant brain tumors. Am I Neuro Radial 1985; 6: 855- 62. 5. Brant- Zawadzki M, Berry I, Osaki L, et ai. Cd- DTPA in clinical MR of the brain: 1. Intraxial lesions. Am I Neural Radial 1986; 7: 781- 8. 6. Felix R, Schomer W, Laniado M, et al. Brain tumors: MR imaging with gadolinium- DTPA. Radiology 1985; 156: 681- 8. I Gin Neuro- ophtlullmol, Vot. 9, No. 2, 1989 |
