susac syndrome
TRANSCRIPT
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Ophthalmology Grand Rounds
Unilateral Superior Field Loss
September 8, 2009
Michele Todman, MD
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HistoryHPI: 16 y/o female
● Painless superior visual field loss OS● Encephalitis● viral illness 3 weeks prior
PMH:negative
ROS: (-)weakness, numbness,fatigue, incontinence, L’Hermitte’s sign
Meds: NoneFH: Noncontributory
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Initial Examination
Va: 20/20 OU
Pupils: 4mm, RRL OU, No RAPD
Motility: Full OU
Confrontation VF: Superior defect OS; Full OD
Color Plates: 12/12 OU
SLE: WNL OU
DFE: WNL OU
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Initial HVF 24-2
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Initial MRI
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MRI
Small foci of restricted diffusion in body/splenium of corpus callosum and right external and internal capsule
No enhancement associated with lesions
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Labs and CSF
• CBC wnl
• CSF- High protein, 194mg/dl
• CSF- High IgG index, 15.4mg/dl
• CSF- High IgG synthesis rate 13.9mg/24h
• Negative CSF and serology for infectious etiology
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DDx
• ADEM- Acute Disseminated Encephalomyelitis– Abnormal immunologic reaction to virus including
production of Ab’s that cross-react with myelin. Occurs in children and young adults. White and gray matter lesions.
• Optic Neuritis/ MS– Immune mediated demyelination of optic nerve and
white matter lesions (latter indicate likelihood to develop MS)
Treatment at initial presentation:IV methylprednisolone 30mg/kg/day for 5 days
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Interim Visit 2 weeks after:- MRI-Decreased size of white matter lesions in
corpus callosum. Resolving ADEM.
3 Months after Initial Presentation:
- New onset hearing loss
- Stable left eye superior visual field loss & memory trouble/encephalitis
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What is your DDx now?
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Color Fundus Photos
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FA
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Susac’s Syndrome
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Presentation
• Triad of microangiopathy (97%-not full triad at onset. Many patients weeks to years)– Brain: Encephalopathy – Retina: Branch retinal artery occlusion
(microangiopathy-only precapillary arterioles <100 microns) associated with Gass plaques.
– Cochlea: Hearing Loss (cochlear and semicircular canal involvement)
• Female predominance 3:1• Age range 9-70 y/o but usually affects 20-40 y/o• 100 cases reported worldwide but often
misdiagnosed
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Pathogenesis
• Autoimmune endotheliopathy• Damaged endothelial cells cause platelet
aggregation and can block blood flow. Hyaline thrombi are seen at autopsy in terminal arterioles and capillaries.
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Pathogenesis
– FA staining/leakage localizes site of immune attack to endothelium of precapillary arteriole (< 100 microns), a site that consists primarily of endothelium and basement membrane.
– All clotting factors except factor VIII are produced in the liver.
– Factor VIII and Von Willebrand factor are produced by endothelial cells.
– Elevation of factor VIII and Von Willebrand factor Antigen reflect endothelium perturbation.
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Labs and CSF
• Factor VIII- High, 184%
• Von Willebrand’s Antigen, High, >200%
• SLE testing all negative
• CSF- High spinal fluid protein, 194mg/dl
• CSF- High IgG index, 15.4mg/dl
• CSF- High IGg synthesis rate 13.9mg/24h
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Retinal Artery Wall Plaques in Susac Syndrome (4 patients)
Egan, Gass et al., Am J Ophthal 2003
• Reflect endothelium damage, atheromatous plaque develops at site of acute retinal arterial damage
• Yellow or yellow-white and nonrefractile, partly or completely surround blood column
• DDx of Gass plaques- Arterial macroaneurysms, Toxoplasmic retinitis, acute retinal necrosis; can be found at sites where previous emboli have lodged
• Pay attention to color and location– Hollenhorst - orange and refractile– platelet-fibrin - gray-white– calcium plaques - chalk white Emboli - located at retinal bifurcations
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Imaging & FA
• MRI/MRA findings– Central corpus callosal involvement, vs. peripheral involvement
with MS and ADEM– Leptomeningeal enhancement in 33%- not with MS or ADEM– Deep gray matter involvement (basal ganglia and thalamus)
70%– Gray matter lesions rare in MS, common in pediatric ADEM
• FA– BRAO acutely– Multifocal fluorescence of branch arterioles (pre-occlusive
lesions)– Peripheral retinal arterial wall occlusion
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Callosum “holes”- develop as acute callosal changes resolve
(MS/ADEM - different distribution)
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Clinical Course
• Lasts from 6 months- 4 years• Some have full recovery, others profound
impairment with cognitive deficits, gait disturbance, and hearing loss
• Usually vision not seriously impaired• When diagnosis and treatment are delayed-
permanent morbidity is higher in terms of neurologic deficit, visual loss, and hearing loss
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Treatment
• IV methylprednisolone, followed by oral steroids in conjunction with cyclophosphamide or immunoglobulin seem helpful
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Back to Our Patient
• IV Solumedrol x 3 days with IVIG x 3 days
• 60mg Prednisone x 28 days and taper
• Cyclophosphamide every 2 weeks for 6 months
• ASA 325mg daily
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Conclusion
• Susac syndrome: triad of encephalopathy, BRAO, and deafness
• MRI of brain: central corpus callosal involvement, both white and gray matter lesions
• Fundus exam: Look for Gass plaques• Labs: Check VWF Ag and factor VIII• Obtain audiogram even if no obvious hearing
loss