Case of the Month

Edited by Robert N. Johnson, MD

Case #108, June, 2018

Presented by:

Joseph Alsberge, MD

A 44-year-old Caucasian man with loss of vision in his left eye for several months.

Figures 1-3: Color photographs of the right and left disc and macula. These appear unremarkable. The color photograph of the superotemporal retina in the left eye shows an a branch artery occlusion and sheathing (white arrow).

Case History

A 44-year-old Caucasian man presented with the complaint of an inferonasal visual field defect in the left eye of several months duration.

On examination, visual acuity was 20/20 in both eyes. The anterior segment examination was normal. Dilated examination of the right eye was unremarkable, while the left eye showed arteriolar sheathing along the superotemporal arcade, and arteriolar occlusion distal to the sheathing (Figures 1-3). Fluorescein angiography performed one-month prior by the referring provider was reviewed and was notable for a segmental area of arteriolar staining, arteriolar occlusions, and peripheral non-perfusion in both eyes (Figures 4-8). Fluorescein angiography was repeated and revealed new areas of segmental arteriolar staining in both eyes (Figures 9-10).

Figure 4: Mid-phase fluorescein angiogram of the right eye shows a normal study

Figure 5: Fluorescein angiogram of the superotemporal area of the right eye. Note the area of mid-arterial staining

Figure 6: Fluorescein angiogram of the right eye. inferotemporal. Note the area of arteriolar occlusion and staining.

Figure 7: Fluorescein angiogram of the left eye. Note the area of arteriolar occlusion and nonperfusion along superotemporal arcade.

Figure 8: Fluorescein angiogram of the left eye, temporal periphery. Note the nonperfusion.

Figure 9: Fluorescein angiogram montage of the right eye. Note the areas of arteriolar staining, occlusion and areas of nonperfusion.

Figure 10: Fluorescein angiogram montage of the right eye. Note the areas of arteriolar staining, occlusion and areas of nonperfusion.

What is your Diagnosis?

Differential Diagnosis

Systemic coagulopathy, embolism, sarcoidosis, systemic lupus erythematosus, polyarteritis nodosa, Churg-Strauss syndrome, syphilis, bartonella henslae, toxoplasmosis, Susac syndrome.

Additional History and Diagnosis

An extensive work up including serologic testing for systemic coagulopathies, collagen vascular diseases, and infections was unrevealing. Audiometry revealed unilateral high-frequency hearing loss, and magnetic resonance imaging (MRI) of the brain showed a round lesion in the splenium of the corpus callosum (Figure 11), leading to the diagnosis of Susac syndrome. After an extensive discussion with the patient, the decision was made to monitor carefully and defer systemic anti-inflammatory therapy. He was placed on daily aspirin. At 2.5 years follow-up, the patient has remained stable without evidence of ongoing occlusive events.

Figure 11: Magnetic resonance imaging of the brain revealed a round lesion in the splenium of the corpus callosum consistent with Susac syndrome.

Discussion

Susac syndrome is a multi-system vasculopathy characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss.1 It was first described by John Susac and colleagues in 1979.2

Susac syndrome is rare, and tends to occur in the age range of 20-40 years, with women more commonly affected than men in a 3 to 1 ratio.3 The exact pathophysiologic mechanism is unknown, but is likely an immune-mediated endotheliopathy affecting the arterioles of the retina, brain, and cochlea.1

The branch retinal artery occlusions in Susac syndrome are multiple, may be unilateral or bilateral, and may be recurrent over time. Patients may present with scotoma and/or photopsia in the corresponding ischemic area, or they may be asymptomatic if the ischemia is peripheral.3 Fluorescein angiography reveals multiple areas of segmental arterial staining, often near the site of arterial non-perfusion, suggesting that the occlusions are secondary to retinal arteritis.1 “Gass plaques” are yellow-white arterial wall plaques that can develop along the obstructed arterial segment.1 Gass plaques tend to occur at the mid-portion of the arteriole, in contrast to Hollenhorst plaques of embolic etiology, which tend to become lodged at arteriolar bifurcations.3 Previously occluded arterioles may appear as ghost vessels.1

The encephalopathy of Susac syndrome presents variably.3 Headache is a common feature. Other neurologic features can include confusion, mood and personality changes, and seizures.4 MRI imaging of the brain often shows multifocal small, round lesions consistent with infarcts in the periventricular region and corpus callosum.1 The sensorineural hearing loss may be unilateral or bilateral, and is felt to result from microinfarctions of the cochlea. Patients may also develop tinnitus and vertigo. Audiometry typically reveals low and medium frequency hearing loss.3 The diagnosis of Susac syndrome may be delayed by the fact that it can take years for all three aspects of the triad to manifest.1

The clinical course of Susac syndrome is unpredictable. Some patients will have mild, self-limiting disease, such as the case presented here, whereas others will have a more severe and recurrent course.3

Since the disease is uncommon, there are no well-established treatment guidelines. Various regimens involving combinations of systemic steroids, immunomodulatory agents, and intravenous immunoglobulin have been tried.1,3 The regimen should be tailored to the patient and severity of disease. Aspirin has been recommended for all patients.3 Patients with encephalopathy may require more aggressive and prolonged immunomodulatory therapy.5 Retinal, optic disc, and iris neovascularization can occur in up to 25% of eyes, requiring panretinal photocoagulation.1

Take Home Points

  • Susac syndrome is characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss
  • Salient ocular findings are multiple branch retinal artery occlusions, Gass plaques (yellow-white arterial wall plaques), and segmental arteriolar wall hyperfluorescence on fluorescein angiography
  • Work up should include formal audiometry and MRI of the brain

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References

  1. Agarwal A. Idiopathic Recurrent Branch Retinal Arterial Occlusion (Susac Syndrome). In: Agarwal, A. Gass’ Atlas of Macular Diseases. Fifth ed. Elsevier:474-479.
  2. Susac JO, Hardman JM, Selhorst JB. Microangiopathy of brain and retina. Neurology 1979;29:313-316.
  3. Bitra RK, Eggenberger E. Review of Susac Syndrome. Curr Opin Ophthalmol 2011;22:472-476
  4. Pawate S, Agarwal A, Moses H, Sriram S. The spectrum of Susac’s syndrome. Neurol Sci 2009;30:59-64.
  5. Rennebohm R, Susac JO, Egan RA, Daroff RB. Susac’s syndrome: update. J Neurol Sci 2010;299:86-91.

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