Susac Syndrome

Ophthalmology Grand Rounds

Unilateral Superior Field Loss

September 8, 2009

Michele Todman, MD

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

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

Initial HVF 24-2

Initial MRI

MRI

Small foci of restricted diffusion in body/splenium of corpus callosum and right external and internal capsule

No enhancement associated with lesions

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

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

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

What is your DDx now?

Color Fundus Photos

FA

Susac’s Syndrome

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

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.

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.

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

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

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

Callosum “holes”- develop as acute callosal changes resolve

(MS/ADEM - different distribution)

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

Treatment

• IV methylprednisolone, followed by oral steroids in conjunction with cyclophosphamide or immunoglobulin seem helpful

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

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