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Chiasmal optic neuritis: A report of three cases
Taiwan Journal of Ophthalmology 2 (2012) 68e72
Contents lists available at SciVerse ScienceDirect
Taiwan Journal of Ophthalmology journal homepage: www.e-tjo.com
Case report
Chiasmal optic neuritis: A report of three cases Shih-Yun Lee a, An-Guor Wang a, b, c, May-Yung Yen a, b, * a
Department of Ophthalmology, Taipei Veterans General Hospital, Taipei 11217, Taiwan School of Medicine, National Yang-Ming University, Taipei 11217, Taiwan c Institute of Neuroscience, National Yang-Ming University, Taipei 11217, Taiwan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 September 2011 Received in revised form 24 November 2011 Accepted 2 December 2011 Available online 9 January 2012
Chiasmal optic neuritis (ON), a rare condition that affects the optic chiasm, is mostly associated with inflammatory demyelinating disorders and may be the initial manifestation of multiple sclerosis (MS). Here, we reported three cases of MS with chiasmal optic neuritis. The clinical manifestations, neuroimaging results, and visual prognosis were evaluated in each patient. Routine eye examinations and auxiliary examinations, including Ishihara color plate, determination of the visual field (VF), and magnetic resonance imaging (MRI) of the optic nerve and chiasm, were performed. All patients presented with reduced VA and VF defects. The abnormal enhancement of the optic chiasm was clearly demonstrated on MRI. Two patients recovered after the systemic administration of steroids, but the other patient only partially recovered. In conclusion, although it is rare, chiasmal ON should be considered in patients who develop bitemporal hemianopia. MRI is the modality of choice for accurate diagnosis. Early diagnosis and proper treatment are mandatory for the restoration of restore visual function. Copyright Ó 2012, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved.
Keywords: bitemporal hemianopia multiple sclerosis optic chiasm optic neuritis
1. Introduction Optic neuritis (ON) is a demyelinating inflammation of the optic nerve. Depending on the study, 13e87% of patients with ON have or develop multiple sclerosis (MS).1e4 Twenty percent of MS patients present with ON as their initial demyelinating symptom, and up to 75% of MS patients experience an episode of ON during the course of their disease. However, clinical reports of chiasmal involvement in MS are rare.5e9 Here, we described three cases of chiasmal ON that presented in patients with MS. The corresponding lesions in the chiasm were clearly visible on MRI.
2. Clinical presentation Three patients with confirmed medical histories of MS were identified from the authors’ clinical practice at Taipei Veterans General Hospital (Taipei, Taiwan). The clinical manifestations, findings on imaging, medical treatments, and disease courses were * Corresponding author. Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Section 2, Shih-Pai Road, Taipei 11217, Taiwan. ROC. Tel.: þ886 2 28757325; fax: þ886 2 28761351. E-mail address: [email protected] (M.-Y. Yen).
retrospectively analyzed. The demographic data and clinical features of these three patients are summarized in Table 1. 2.1. Case 1 A 26-year-old female complained of the sudden onset of bitemporal visual field defects that had persisted for 3 days. She had experienced recurrent ON in the right eye since 2005. Later, MS was diagnosed. Best corrected visual acuity (BCVA) was 20/15 in both eyes. She missed only one Ishihara color plate in each eye on examination. Mild relative afferent pupillary defect (RAPD) was noted in the right eye. Fundoscopy showed a slight temporal pallor of the right optic disc. Examination of the visual field indicated a bitemporal defect (Fig. 1). Neurological examinations were unremarkable. Laboratory investigations, which included determinations of the complete blood count, erythrocyte sedimentation rate, serum chemistries, antinuclear antibody titers, rheumatoid factor, and immunoglobulin G (IgG), IgA, and IgM levels, were all normal. Magnetic resonance imaging (MRI) revealed a thickened optic chiasm with abnormal bilateral enhancement that was more severe on the left side (Fig. 2). She received methylprednisolone pulse therapy followed by oral prednisolone. Two weeks later, her visual acuity remained at 20/15 in both eyes. Her visual field demonstrated a faint hemianopic scotoma in the right eye and a subtle inferotemporal defect in the left eye (Fig. 3).
2211-5056/$ e see front matter Copyright Ó 2012, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved. doi:10.1016/j.tjo.2011.12.002
S.-Y. Lee et al. / Taiwan Journal of Ophthalmology 2 (2012) 68e72
69
Table 1 Demographic data and clinical features of patients with chiasmal optic neuritis. Patient No./ Age (y)/sex
Symptoms/ duration
1/26/F
Visual acuity, OD, OS
Color vision, OD, OS
Disc appearance
Visual field
MRI results
Treatment
Outcome
Optic chiasm enlargement and enhancement, especially in the left side Asymmetric enlargement of the optic chiasm with enhancement, prechiasmal portion involved in the left eye Atrophic change in the optic chiasm with faint enhancement in the right side
Steroid pulse therapy
VF improved
Steroid pulse therapy
Complete recovery
Steroid pulse therapy
Partial recovery
Initial
Final
Bitemporal VF loss/3 d
OU 20/15
OU 20/15
OU 14/15
Mild temporal pallor in the right eye
Bitemporal defect
2/41/F
Blurry vision in the left eye/1 d
HM, 20/50
HM, 20/20
0/15, 1/15
Pale disc in the right eye, hyperemic in the left eye
Total loss in the right eye, superior-temporal island in the left eye
3/33/F
Right eye pain, then gradual blurring/5 d
LP, 20/200
OU 20/200
OU 1/15
Bilateral pale discs
Total loss in the right eye, temporal defect in the left eye
HM, hand motion; LP, light perception; OD, oculus dexter; OS, oculus sinister; OU, oculus uterque; VF, visual field.
Fig. 1. Case 1. Humphrey automated visual field. Initially, bitemporal visual field defects presented.
2.2. Case 2 A 41-year-old woman complained of blurry vision in the left eye for 1 day. She had been diagnosed with MS and recurrent ON in the right eye for 10 years, which resulted in optic atrophy. BCVA was hand motion in the right eye and 20/50 in the left eye. She could only read one Ishihara color plate with her left eye. RAPD was detected in the right eye. Fundoscopy showed that the right disc was pale and the left disc was hyperemic. Her visual field was almost totally obscured in the right eye and a profound depression was evident in the left eye, but the superior-temporal quadrant was spared (Fig. 4). MRI of the brain revealed asymmetric enlargement of the optic chiasm and abnormal enhancement that was more marked on the left side. The prechiasmal portion of the left optic nerve was also involved (Fig. 5A,B); this might have resulted in the unusual visual field defects. Two weeks after steroid pulse therapy, BCVA, color sense, and visual field (Fig. 6) of the left eye had completely recovered. 2.3. Case 3 Fig. 2. Case 1. T1-weighted MRI image (coronal view) after gadolinium injection. A thickened optic chiasm with abnormal enhancement (arrow) is shown. The left side of the chiasm is more severely affected.
A 33-year-old woman complained of gradual visual loss in the right eye for 2 days. One week before symptoms presented, she
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Fig. 3. Case 1. Visual field after treatment. A faint hemianoptic scotoma in the right eye and a subtle inferotemporal defect in the left eye are evident.
noticed pain in her right eye. Five days later, vision in her right eye was blurry. She had been diagnosed with recurrent ON in both eyes since 1985, and MS was diagnosed in 2001. She had been receiving Inteferon b-1a (EMD Serono, Inc. and Pfizer Inc) therapy. BCVA was light perceptive in the right eye and 20/200 in the left eye. She could read only one Ishihara color plate with her left eye. RAPD was present in the right pupil. Fundoscopy revealed bilateral pale discs. Her visual field was nearly totally lost in the right eye and a temporal defect was evident in the left eye. MRI revealed atrophic changes to the optic chiasm with faint enhancement on the right side (Fig. 7). High-dose methylprednisolone was administered for 5 days, followed by oral steroid. One month later, her BCVA had improved to being able to count fingers in the right eye but remained at 20/ 200 in the left eye. Both optic discs remained pale. Eight months later, her BCVA improved to 20/200 in the right eye but remained at 20/200 in the left eye.
3. Discussion In 1975, Bell reported the first case of a true clinical-pathologic correlation between MS and chiasmal involvement by exploratory craniotomy.7 Spector reported six cases of MS with chiasmal visual field defects. Enlargement of the optic nerve and chiasm were observed by pneumoencephalography in two cases.8 Edward described three patients with evidence of chiasmal enlargement on computed topography (CT) imaging.9 Rosenblatt reported the first findings of chiasmal ON using MRI, which showed a large, bright T2 lesion at the optic tract-chiasm junction.10 Newman reported four cases with increased T2 intensity in the optic chiasm and contrast enhancement on T1-weighted imaging after gadolinium injection.6 After high-dose intravenous steroid therapy, all of these cases were resolved on the follow-up MRI. Our cases also have similar but much clearer findings on enhanced T1-weighted MRI. All of our cases demonstrated an enhanced chiasm after gadolinium injection. In case 2, abnormal enlargement of the
Fig. 4. Case 2. Humphrey automated visual field. Total defects are evident in the right eye. Only the superior-temporal field was spared in the left eye.
S.-Y. Lee et al. / Taiwan Journal of Ophthalmology 2 (2012) 68e72
71
Fig. 7. Case 3. MRI of the chiasm. Coronal T1-weighted image after gadolinium injection. Atrophic changes occurred in the bilateral optic chiasm. Faint enhancement of the right-side optic chiasm is noted (arrow).
Fig. 5. Case 2. T1-weighted MRI of the optic nerve. (A) Axial view showing that the prechiasmal optic nerve in the left eye is abnormally enhanced (arrow). (B) Coronal view demonstrating asymmetric enlargement of the optic chiasm with increased enhancement. These findings are more remarkable on the left side (arrow).
involved chiasm and prechiasmal optic nerve were also evident (Fig. 5A,B). In 2009, Kawasaki reported a large cohort study of idiopathic chiasmal neuritis. In their series of 20 patients, the chief symptom
Fig. 6. Case 2. Visual field of the left eye after treatment. The visual field defect is normalized.
was monocular visual loss, and 20% of the patients with chiasmal neuritis also had eye pain. In 80% of cases, the diagnosis was confirmed by MRI, which showed enlargement and/or enhancement of the chiasm.11 Asymmetric involvement of the chiasm may be present, and prechiasmatic optic involvement may also have presented at the same time, just like our cases. In their series, all of the affected eyes were able to substantially improve regardless of treatment, and 97% were able to reach a visual acuity of 20/40 or better. Visual field also improved in all patients.11 However, in our three cases, only two patients demonstrated a complete recovery. The third patient had a history of recurrent ON before chiasmal involvement presented. Repeated inflammation and optic nerve damage may result in the clinical course and partial recovery of VA. Atrophic changes in the optic nerve were clearly visible on MRI. Chiasmal ON is mostly associated with inflammatory demyelinating disorders,6,12 however it can be caused by other etiologies.13e19 We reviewed the case reports on chiasmal ON that are currently available in the literature and found a total of 56 reported cases. Among the 59 cases (including our 3 cases), 24 cases (40.7%) were patients with MS or presumed to have MS and 25 cases (42.4%) were idiopathic, which implies that they were possibly affected by demyelinating processes. Females (49 cases; 83.0%) are predominantly affected, with a mean age of 33.2 years at the time of presentation. The most common change in the visual field that results from chiasmal ON is bitemporal hemianopia (40 cases; 67.8%), followed by junctional scotoma (12 cases; 20.3%). Among the 59 cases of chiasmal ON, eight cases were clinically diagnosed; the others were confirmed by pneumoencephalography, CT, MRI, or a combination of methods. Fifteen cases received both CT and MRI examinations. Among these cases, 73.3% were detected on MRI but only 33.3% showed abnormal findings on CT. MRI is more sensitive for the detection of chiasmal ON. Patients with chiasmal ON often have a favorable prognosis. In our literature review, 54 cases (91.5%) with chiasmal ON improved or even experienced a complete recovery in terms of the BCVA and visual field, regardless of receiving treatment or not. However, some patients may suffer a prolonged course of visual loss or only
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partial recovery that results in optic atrophy due to repeated ON attacks and injury, similar to case 3. 4. Conclusion Chiasmal ON is a rare condition that is mostly associated with inflammatory demyelinating disorders. Patients may complain about progressive monocular, bilateral simultaneous, or rapidly sequential visual loss. In most cases, bitemporal visual field defects are present. Enlargement and/or enhancement of the optic chiasm are usually well demonstrated on MRI. Steroids are the mainstay of treatment. Visual prognosis is usually favorable before optic atrophy develops. For patients who present with bitemporal visual field defects, clinicians should take into consideration the diagnosis of demyelinating diseases. MRI is the modality of choice for accurate evaluation of the optic chiasm. Acknowledgments The authors have no conflicts of interests or sources of funding to declare. References 1. Lin YC, Yen MY, Hsu WM, Lee HC, Wang AG. Low conversion rate to multiple sclerosis in idiopathic optic neuritis patients in Taiwan. Jpn J Ophthalmol 2006;50:170e5. 2. Acheson J. Optic nerve and chiasmal disease. J Neurol 2000;247:587e95. 3. Foroozan R. Chiasmal syndromes. Curr Opin Ophthalmol 2003;14:325e31.
4. Optic Neuritis Study Group. High- and low-risk profiles for the development of multiple sclerosis within 10 years after optic neuritis: experience of the optic neuritis treatment trial. Arch Ophthalmol 2003;121:944e9. 5. Kerty E, Eide N, Nakstad P, Nyberg-Hansen R. Chiasmal optic neuritis. Acta Ophthalmol (Copenh) 1991;69:135e9. 6. Newman NJ, Lessell S, Winterkorn JM. Optic chiasmal neuritis. Neurology 1991;41:1203e10. 7. Bell RA, Robertson DM, Rosen DA, Kerr AW. Optochiasmatic arachnoiditis in multiple sclerosis. Arch Ophthalmol 1975;93:191e3. 8. Spector RH, Glaser JS, Schatz NJ. Demyelinative chiasmal lesions. Arch Neurol 1980;37:757e62. 9. Edwards MK, Gilmor RL, Franco JM. Computed tomography of chiasmal optic neuritis. AJNR 1983;4:816e8. 10. Rosenblatt MA, Behrens MM, Zweifach PH, Forman S, Odel JG, Duncan CM, et al. Magnetic resonance imaging of optic tract involvement in multiple sclerosis. Am J Ophthalmol 1987;104:74e9. 11. Kawasaki A, Purvin VA. Idiopathic chiasmal neuritis: clinical features and prognosis. Arch Ophthalmol 2009;127:76e81. 12. Nonoyama S, Shibuya Y, Kodama T, Masuda H, Ohira A. Recovery of vision after chiasmal optic neuritis. Acta Ophthalmol Scand 2003;81:83e4. 13. Tang RA, Grotta JC, Lee KF, Lee YE. Chiasmal syndrome in sarcoidosis. Arch Ophthalmol 1983;101:1069e73. 14. Frohman LP, Frieman BJ, Wolansky L. Reversible blindness resulting from optic chiasmitis secondary to systemic lupus erythematosus. J Neuroophthalmol 2001;21:18e21. 15. Costa RM, Santos AC, Costa LS. An unusual chiasmal visual defect in a patient with neuromyelitis optica: case report. Arq Bras Oftalmol 2007;70:153e5. 16. Scott IU, Silva-Lepe A, Siatkowski RM. Chiasmal optic neuritis in Lyme disease. Am J Ophthalmol 1997;123:136e8. 17. Beiran I, Krasnitz I, Zimhoni-Eibsitz M, Gelfand YA, Miller B. Paediatric chiasmal neuritis: typical of post-Epstein-Barr virus infection? Acta Ophthalmol Scand 2000;78:226e7. 18. Greven CM, Singh T, Stanton CA, Martin TJ. Optic chiasm, optic nerve and retinal involvement secondary to varicella-zoster virus. Arch Ophthalmol 2001;119:608e10. 19. Irioka T, Akaza M, Nakao K, Kanouchi T, Yokota T, Mizusawa H. Chiasmal optic neuritis following mumps parotitis. J Neurol 2008;255:773e4.
Contents lists available at SciVerse ScienceDirect
Taiwan Journal of Ophthalmology journal homepage: www.e-tjo.com
Case report
Chiasmal optic neuritis: A report of three cases Shih-Yun Lee a, An-Guor Wang a, b, c, May-Yung Yen a, b, * a
Department of Ophthalmology, Taipei Veterans General Hospital, Taipei 11217, Taiwan School of Medicine, National Yang-Ming University, Taipei 11217, Taiwan c Institute of Neuroscience, National Yang-Ming University, Taipei 11217, Taiwan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 September 2011 Received in revised form 24 November 2011 Accepted 2 December 2011 Available online 9 January 2012
Chiasmal optic neuritis (ON), a rare condition that affects the optic chiasm, is mostly associated with inflammatory demyelinating disorders and may be the initial manifestation of multiple sclerosis (MS). Here, we reported three cases of MS with chiasmal optic neuritis. The clinical manifestations, neuroimaging results, and visual prognosis were evaluated in each patient. Routine eye examinations and auxiliary examinations, including Ishihara color plate, determination of the visual field (VF), and magnetic resonance imaging (MRI) of the optic nerve and chiasm, were performed. All patients presented with reduced VA and VF defects. The abnormal enhancement of the optic chiasm was clearly demonstrated on MRI. Two patients recovered after the systemic administration of steroids, but the other patient only partially recovered. In conclusion, although it is rare, chiasmal ON should be considered in patients who develop bitemporal hemianopia. MRI is the modality of choice for accurate diagnosis. Early diagnosis and proper treatment are mandatory for the restoration of restore visual function. Copyright Ó 2012, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved.
Keywords: bitemporal hemianopia multiple sclerosis optic chiasm optic neuritis
1. Introduction Optic neuritis (ON) is a demyelinating inflammation of the optic nerve. Depending on the study, 13e87% of patients with ON have or develop multiple sclerosis (MS).1e4 Twenty percent of MS patients present with ON as their initial demyelinating symptom, and up to 75% of MS patients experience an episode of ON during the course of their disease. However, clinical reports of chiasmal involvement in MS are rare.5e9 Here, we described three cases of chiasmal ON that presented in patients with MS. The corresponding lesions in the chiasm were clearly visible on MRI.
2. Clinical presentation Three patients with confirmed medical histories of MS were identified from the authors’ clinical practice at Taipei Veterans General Hospital (Taipei, Taiwan). The clinical manifestations, findings on imaging, medical treatments, and disease courses were * Corresponding author. Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Section 2, Shih-Pai Road, Taipei 11217, Taiwan. ROC. Tel.: þ886 2 28757325; fax: þ886 2 28761351. E-mail address: [email protected] (M.-Y. Yen).
retrospectively analyzed. The demographic data and clinical features of these three patients are summarized in Table 1. 2.1. Case 1 A 26-year-old female complained of the sudden onset of bitemporal visual field defects that had persisted for 3 days. She had experienced recurrent ON in the right eye since 2005. Later, MS was diagnosed. Best corrected visual acuity (BCVA) was 20/15 in both eyes. She missed only one Ishihara color plate in each eye on examination. Mild relative afferent pupillary defect (RAPD) was noted in the right eye. Fundoscopy showed a slight temporal pallor of the right optic disc. Examination of the visual field indicated a bitemporal defect (Fig. 1). Neurological examinations were unremarkable. Laboratory investigations, which included determinations of the complete blood count, erythrocyte sedimentation rate, serum chemistries, antinuclear antibody titers, rheumatoid factor, and immunoglobulin G (IgG), IgA, and IgM levels, were all normal. Magnetic resonance imaging (MRI) revealed a thickened optic chiasm with abnormal bilateral enhancement that was more severe on the left side (Fig. 2). She received methylprednisolone pulse therapy followed by oral prednisolone. Two weeks later, her visual acuity remained at 20/15 in both eyes. Her visual field demonstrated a faint hemianopic scotoma in the right eye and a subtle inferotemporal defect in the left eye (Fig. 3).
2211-5056/$ e see front matter Copyright Ó 2012, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved. doi:10.1016/j.tjo.2011.12.002
S.-Y. Lee et al. / Taiwan Journal of Ophthalmology 2 (2012) 68e72
69
Table 1 Demographic data and clinical features of patients with chiasmal optic neuritis. Patient No./ Age (y)/sex
Symptoms/ duration
1/26/F
Visual acuity, OD, OS
Color vision, OD, OS
Disc appearance
Visual field
MRI results
Treatment
Outcome
Optic chiasm enlargement and enhancement, especially in the left side Asymmetric enlargement of the optic chiasm with enhancement, prechiasmal portion involved in the left eye Atrophic change in the optic chiasm with faint enhancement in the right side
Steroid pulse therapy
VF improved
Steroid pulse therapy
Complete recovery
Steroid pulse therapy
Partial recovery
Initial
Final
Bitemporal VF loss/3 d
OU 20/15
OU 20/15
OU 14/15
Mild temporal pallor in the right eye
Bitemporal defect
2/41/F
Blurry vision in the left eye/1 d
HM, 20/50
HM, 20/20
0/15, 1/15
Pale disc in the right eye, hyperemic in the left eye
Total loss in the right eye, superior-temporal island in the left eye
3/33/F
Right eye pain, then gradual blurring/5 d
LP, 20/200
OU 20/200
OU 1/15
Bilateral pale discs
Total loss in the right eye, temporal defect in the left eye
HM, hand motion; LP, light perception; OD, oculus dexter; OS, oculus sinister; OU, oculus uterque; VF, visual field.
Fig. 1. Case 1. Humphrey automated visual field. Initially, bitemporal visual field defects presented.
2.2. Case 2 A 41-year-old woman complained of blurry vision in the left eye for 1 day. She had been diagnosed with MS and recurrent ON in the right eye for 10 years, which resulted in optic atrophy. BCVA was hand motion in the right eye and 20/50 in the left eye. She could only read one Ishihara color plate with her left eye. RAPD was detected in the right eye. Fundoscopy showed that the right disc was pale and the left disc was hyperemic. Her visual field was almost totally obscured in the right eye and a profound depression was evident in the left eye, but the superior-temporal quadrant was spared (Fig. 4). MRI of the brain revealed asymmetric enlargement of the optic chiasm and abnormal enhancement that was more marked on the left side. The prechiasmal portion of the left optic nerve was also involved (Fig. 5A,B); this might have resulted in the unusual visual field defects. Two weeks after steroid pulse therapy, BCVA, color sense, and visual field (Fig. 6) of the left eye had completely recovered. 2.3. Case 3 Fig. 2. Case 1. T1-weighted MRI image (coronal view) after gadolinium injection. A thickened optic chiasm with abnormal enhancement (arrow) is shown. The left side of the chiasm is more severely affected.
A 33-year-old woman complained of gradual visual loss in the right eye for 2 days. One week before symptoms presented, she
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Fig. 3. Case 1. Visual field after treatment. A faint hemianoptic scotoma in the right eye and a subtle inferotemporal defect in the left eye are evident.
noticed pain in her right eye. Five days later, vision in her right eye was blurry. She had been diagnosed with recurrent ON in both eyes since 1985, and MS was diagnosed in 2001. She had been receiving Inteferon b-1a (EMD Serono, Inc. and Pfizer Inc) therapy. BCVA was light perceptive in the right eye and 20/200 in the left eye. She could read only one Ishihara color plate with her left eye. RAPD was present in the right pupil. Fundoscopy revealed bilateral pale discs. Her visual field was nearly totally lost in the right eye and a temporal defect was evident in the left eye. MRI revealed atrophic changes to the optic chiasm with faint enhancement on the right side (Fig. 7). High-dose methylprednisolone was administered for 5 days, followed by oral steroid. One month later, her BCVA had improved to being able to count fingers in the right eye but remained at 20/ 200 in the left eye. Both optic discs remained pale. Eight months later, her BCVA improved to 20/200 in the right eye but remained at 20/200 in the left eye.
3. Discussion In 1975, Bell reported the first case of a true clinical-pathologic correlation between MS and chiasmal involvement by exploratory craniotomy.7 Spector reported six cases of MS with chiasmal visual field defects. Enlargement of the optic nerve and chiasm were observed by pneumoencephalography in two cases.8 Edward described three patients with evidence of chiasmal enlargement on computed topography (CT) imaging.9 Rosenblatt reported the first findings of chiasmal ON using MRI, which showed a large, bright T2 lesion at the optic tract-chiasm junction.10 Newman reported four cases with increased T2 intensity in the optic chiasm and contrast enhancement on T1-weighted imaging after gadolinium injection.6 After high-dose intravenous steroid therapy, all of these cases were resolved on the follow-up MRI. Our cases also have similar but much clearer findings on enhanced T1-weighted MRI. All of our cases demonstrated an enhanced chiasm after gadolinium injection. In case 2, abnormal enlargement of the
Fig. 4. Case 2. Humphrey automated visual field. Total defects are evident in the right eye. Only the superior-temporal field was spared in the left eye.
S.-Y. Lee et al. / Taiwan Journal of Ophthalmology 2 (2012) 68e72
71
Fig. 7. Case 3. MRI of the chiasm. Coronal T1-weighted image after gadolinium injection. Atrophic changes occurred in the bilateral optic chiasm. Faint enhancement of the right-side optic chiasm is noted (arrow).
Fig. 5. Case 2. T1-weighted MRI of the optic nerve. (A) Axial view showing that the prechiasmal optic nerve in the left eye is abnormally enhanced (arrow). (B) Coronal view demonstrating asymmetric enlargement of the optic chiasm with increased enhancement. These findings are more remarkable on the left side (arrow).
involved chiasm and prechiasmal optic nerve were also evident (Fig. 5A,B). In 2009, Kawasaki reported a large cohort study of idiopathic chiasmal neuritis. In their series of 20 patients, the chief symptom
Fig. 6. Case 2. Visual field of the left eye after treatment. The visual field defect is normalized.
was monocular visual loss, and 20% of the patients with chiasmal neuritis also had eye pain. In 80% of cases, the diagnosis was confirmed by MRI, which showed enlargement and/or enhancement of the chiasm.11 Asymmetric involvement of the chiasm may be present, and prechiasmatic optic involvement may also have presented at the same time, just like our cases. In their series, all of the affected eyes were able to substantially improve regardless of treatment, and 97% were able to reach a visual acuity of 20/40 or better. Visual field also improved in all patients.11 However, in our three cases, only two patients demonstrated a complete recovery. The third patient had a history of recurrent ON before chiasmal involvement presented. Repeated inflammation and optic nerve damage may result in the clinical course and partial recovery of VA. Atrophic changes in the optic nerve were clearly visible on MRI. Chiasmal ON is mostly associated with inflammatory demyelinating disorders,6,12 however it can be caused by other etiologies.13e19 We reviewed the case reports on chiasmal ON that are currently available in the literature and found a total of 56 reported cases. Among the 59 cases (including our 3 cases), 24 cases (40.7%) were patients with MS or presumed to have MS and 25 cases (42.4%) were idiopathic, which implies that they were possibly affected by demyelinating processes. Females (49 cases; 83.0%) are predominantly affected, with a mean age of 33.2 years at the time of presentation. The most common change in the visual field that results from chiasmal ON is bitemporal hemianopia (40 cases; 67.8%), followed by junctional scotoma (12 cases; 20.3%). Among the 59 cases of chiasmal ON, eight cases were clinically diagnosed; the others were confirmed by pneumoencephalography, CT, MRI, or a combination of methods. Fifteen cases received both CT and MRI examinations. Among these cases, 73.3% were detected on MRI but only 33.3% showed abnormal findings on CT. MRI is more sensitive for the detection of chiasmal ON. Patients with chiasmal ON often have a favorable prognosis. In our literature review, 54 cases (91.5%) with chiasmal ON improved or even experienced a complete recovery in terms of the BCVA and visual field, regardless of receiving treatment or not. However, some patients may suffer a prolonged course of visual loss or only
72
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partial recovery that results in optic atrophy due to repeated ON attacks and injury, similar to case 3. 4. Conclusion Chiasmal ON is a rare condition that is mostly associated with inflammatory demyelinating disorders. Patients may complain about progressive monocular, bilateral simultaneous, or rapidly sequential visual loss. In most cases, bitemporal visual field defects are present. Enlargement and/or enhancement of the optic chiasm are usually well demonstrated on MRI. Steroids are the mainstay of treatment. Visual prognosis is usually favorable before optic atrophy develops. For patients who present with bitemporal visual field defects, clinicians should take into consideration the diagnosis of demyelinating diseases. MRI is the modality of choice for accurate evaluation of the optic chiasm. Acknowledgments The authors have no conflicts of interests or sources of funding to declare. References 1. Lin YC, Yen MY, Hsu WM, Lee HC, Wang AG. Low conversion rate to multiple sclerosis in idiopathic optic neuritis patients in Taiwan. Jpn J Ophthalmol 2006;50:170e5. 2. Acheson J. Optic nerve and chiasmal disease. J Neurol 2000;247:587e95. 3. Foroozan R. Chiasmal syndromes. Curr Opin Ophthalmol 2003;14:325e31.
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