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Show Journal of Neuw- Ophthalmology 19( 4): 238- 239, 1999. © 1999 Lippincott Williams & Wilkins, Inc., Philadelphia Optic Nerve Enhancement on Orbital Magnetic Resonance Imaging in Leber's Hereditary Optic Neuropathy Michael S. Vaphiades, D. O., and Nancy J. Newman M. D. An 18- year- old man with Leber's hereditary optic neuropathy and bilateral visual loss had optic nerve enhancement on Tl-weighted orbital fat- suppressed magnetic resonance imaging. To our knowledge, this is the first reported case of optic nerve enhancement on orbital magnetic resonance imaging in Leber's hereditary optic neuropathy. Key Words: Enhancement- Leber's hereditary optic neuropathy- Optic nerve. CASE REPORT In the first week of November 1996, an 18- year- old man noted painless sequential visual loss in the right eye ( OD), followed by these same symptoms in the left eye ( OS) 2 weeks later. He had no contributory medical history. The neuro- ophthalmologic examination revealed a visual acuity of count fingers vision OD and 20/ 80 OS. Color vision was 0/ 14 OD and 7.5/ 14 OS using the Ishi-hara pseudo- isochromatic plates. Goldmann perimetry showed large central scotomas in both eyes ( OU). Pupils were 7 mm OU with normal reactivity, and there was a 0.9 log unit right relative afferent pupillary defect. Motility and slit- lamp examination results were normal. Ophthalmoscopy showed disc elevation with obscuration of the disc margins OU. A detailed neurologic examination yielded otherwise normal results. Magnetic resonance imaging ( MRI) of the brain and orbits with and without orbital fat suppression and gadolinium administration on December 16, 1996, demonstrated enhancement of the optic nerves bilaterally ( Fig. 1). Chest radiography findings, complete blood count, syphilis serology, angiotensin converting enzyme, Bartonella henselae titer, Lyme titer, HIV test results, and lumbar puncture results were normal. Mitochondrial DNA testing revealed a mutation at nucleotide position Manuscript received May 13, 1999; accepted June 30, 1999. From the Departments of Ophthalmology and Neurology ( M. S. V.), University of Arkansas for Medical Sciences, Little Rock, Arkansas, U. S. A.; and the Departments of Ophthalmology, Neurology, and Neurosurgery ( N. J. N.), Emory University School of Medicine, Atlanta, Georgia, U. S. A. Address correspondence and reprint requests to Michael S. Vaphiades, D. O., Harvey & Bernice Jones Eye Institute, Department of Ophthalmology, University of Arkansas for Medical Sciences, 4301 West Markham, Mail Slot 523, Little Rock, AR 72205- 7199. 3460 which is, compatible with the diagnosis of Leber's hereditary optic neuropathy ( LHON). DISCUSSION Leber's hereditary optic neuropathy is a maternally inherited neuropathy associated with point mutations in the mitochondrial DNA. The orbital MRI findings are typically normal, although an increased signal from the retrobulbar optic nerve has been reported on T2- weighted fast spin echo ( 1) and short time inversion recovery sequences ( 2). Mashima et al. reported four patients with LHON for whom orbital Tl- weighted MRI scans were performed with fat suppression and gadolinium within 4 weeks of visual loss. None of these patients had optic nerve enhancement after gadolinium administration, although increased signals from the retrobulbar optic nerves were noted on T2- weighted fat suppressed sequences ( 1). Previous MRI studies of the optic nerves in patients with LHON did not use orbital fat suppression with gadolinium, and therefore the presence or absence of optic nerve enhancement was not addressed ( 2- 4). It is perhaps not surprising, given the pathology of affected optic nerves that the site of MRI abnormality within the optic nerves in patients with LHON is not limited to the prelaminar portion of the nerve. Indeed, optic nerve cross- sections of patients with LHON have shown fibrocystic scarring in the retrobulbar portion ( 5). Gadolinium does not cross an intact blood- brain barrier, and enhancement with gadolinium administration denotes disruption of the blood- brain barrier within the optic nerve ( 6). The affected optic nerve enhances because gadolinium induces a local magnetic field, resulting in a bright signal on Tl- weighted fat- suppressed images ( 6). Orbital fat suppression is usually necessary to visualize the optic nerve enhancement because of the large amount of bright fat in the orbits ( 6- 8). Typical lesions that result in optic nerve enhancement include optic neuritis, radiation- induced optic neuropathy, and optic nerve tumors ( 6,9). It is unclear why the patients with LHON reported by Mashima et al. did not exhibit optic nerve enhancement after gadolinium administration, especially given that all four patients were within the acute phase of visual loss. 238 OPTIC NERVE ENHANCEMENT ON ORBITAL MRI IN LHON 239 FIG. 1. Coronal ( left) and axial ( right) fat- suppressed gadolinium- i ment bilaterally. Their patients all harbored the 11778 mitochondrial DNA mutation, whereas ours had the 3460 mutation, but that difference is unlikely to have influenced optic nerve pathology. Perhaps, as Mashima et al. suggested, the acute pathology in LHON is preliminar and intraocular, and it takes weeks to months for pathologic findings to involve the retrobulbar optic nerve ( 1). Our patient with LHON was imaged 6 weeks after first eye involvement and 4 weeks after second eye involvement. To our knowledge, ours is the first reported case of a patient with LHON who has demonstrated enhancement of the optic nerves on fat- suppressed gadolinium-enhanced Tl- weighted MRI of the orbits. The presence of optic nerve enhancement in a patient with optic neuropathy does not rule out the diagnosis of LHON. Acknowledgment: This work was supported in part by an unrestricted grant from the Research to Prevent Blindness, Inc., New York City NY. REFERENCES 1. Mashima Y, Oshitari K, Imamura Y, Momoshima S, Shiga H, Oguchi Y. Orbital high resolution magnetic resonance imaging with fast spin echo in the acute stage of Leber's hereditary optic neuropathy. J Neurol Neurosurg Psychiatry 1998; 64: 124- 7. T1 - weighted MRI of the orbits, showing optic nerve enhance- 2. Kermode AG, Moseley IF, Kendell BE, Miller DH, MacManus DG, McDonald WI. Magnetic resonance imaging in Leber's optic neuropathy. J Neurology Neurosurg Psychiatry 1989; 52: 671- 4. 3. Dotti MT, Caputo N, Signorini E, Federico A. Magnetic resonance imaging findings in Leber's hereditary optic neuropathy. Eur Neurol 1992; 32: 17- 9. 4. Riordan- Eva P, Sanders MD, Govan GG, Sweeney MG, Da Costa J, Harding AE. The clinical features of Leber's heredity optic neuropathy defined by the presence of a pathogenic mitochondrial DNA mutation. Brain 1995; 118: 319- 37. 5. Saadati HG, Hsu HY, Heller KB, Sadun AA. A histopathologic and morphometric differentiation of nerves in optic nerve hypoplasia and Leber hereditary optic neuropathy. Arch Ophthalmol 1998; 116: 911- 6. 6. Guy J, Mancuso A, Quisling RG, Beck R, Moster M. Gadolinium- DPTA- enhanced magnetic resonance imaging in optic neuropathies. Ophthalmology 1990; 97: 592- 600. 7. Guy J, Mao J, Bidgood WD, Mancuso A, Quisling RG. Enhancement and demyelination of the intraorbital optic nerve: fat suppression magnetic resonance imaging. Ophthalmology I992; 99: 713- 9. 8. Lee DH, Simon JH, Szumowski J, et al. Optic neuritis and orbital lesions: lipid- suppressed chemical shift MR imaging. Radiology 1991; 179: 543- 6. 9. Gass A, Barker GJ, MacManus D, et al. High resolution magnetic resonance imaging of the anterior visual pathway in patients with optic neuropathies using fast spin echo and phased array local coils. ./ Neurol Neurosurg Psychiatry 1995; 58: 562- 9. ./ Neuw- Ophthalmol, Vol. 19, No. 4, 1999 |
