Progressive Susac syndrome with bilateral visual loss and disability.

Susac syndrome (SS) is a rare retinal-cochlear-cerebral disease with an unclear etiology. A 35-year-old man presented with sudden painless vision loss in the right eye and 2 months later in the left eye with hemiparesis, behavioral changes, and hearing loss. Ophthalmic examinations revealed multiple branch retinal artery occlusions (BRAOs) in both eyes. Brain magnetic resonance imaging showed inflammatory changes with multiple "punched-out" lesions in the corpus callosum which confirmed the diagnosis of SS. Despite intravenous and oral corticosteroid therapy, the disease progressed with the development of new BRAOs, low vision in both eyes, and disability. Prompt diagnosis and early treatment may save the vision and even patient's life.

Susac syndrome (SS) is a rare retinal-cochlear-cerebral disease with an unclear etiology. It is characterized by the triad of encephalopathy, retinopathy, and sensory neural hearing loss, which was first described by Susac et al. in 1979.[1] The diagnosis of SS is challenging. The classic triad of SS may not be entirely present at the onset of the disease and the retinal involvement which is commonly asymptomatic may be missed.[2]

The objective of this study is to report a case of progressive SS with bilateral severe visual loss, deafness, and neurological findings.

Case Report

A 35-year-old man presented with sudden painless vision deterioration in the right eye (OD) for 3 days. He was otherwise healthy, and past medical history was unremarkable. On ophthalmic examination, in the OD, best-corrected visual acuity (BCVA) was counting fingers (CF) at 3 m and afferent pupillary defect was (1+) positive. Dilated fundus examination revealed branch retinal artery occlusion (BRAO) with retinal cloudy swelling at the upper part of the macula, which was found to be even more widespread on fluorescein angiography (FA) [Fig. 1a]. The rest of ophthalmic examination was otherwise unremarkable. The left eye (OS) was completely normal with vision of 10/10. Considering the young age of the patient, we performed systemic workup including complete blood count, erythrocyte sedimentation rate, C-reactive protein, carotid Doppler ultrasonography, cardiac evaluation, and blood tests for factor V Leiden mutation; protein C, protein S, antithrombin III, homocysteine levels, sickle-cell disease, and antiphospholipid antibodies. All the performed tests and serological screening for infectious agents were negative.

Figure 1

(a) Fluorescein angiography image shows supratemporal branch retinal artery occlusions. (b) Fluorescein angiography demonstrates complete improvement of branch retinal artery occlusions. (c) Fundus photograph illustrates Gass plaques. (d) Fluorescein angiography image shows supratemporal branch retinal artery occlusions. (e and f) Fluorescein angiography images demonstrate multiple neovascularizations

Two months later, with no treatment, visual acuity of the OD improved to 8/10 with improvement of perfusion on FA [Fig. 1b], but he complained of sudden painless vision deterioration in the OS, hearing loss, mild mental changes, and hemiparesis of the right side of the body. BCVA of the OS was CF at 1 m, and dilated fundus examination revealed yellow-white deposits at the mid segments of the arteriole (Gass plaques) in the OD [Fig. 1c] and multiple BRAOs in the OS, which was confirmed by FA [Fig. 1d]. Lumbar puncture revealed raised protein with no cells and no oligoclonal bands.

A T1-weighted brain magnetic resonance imaging (MRI) revealed inflammatory changes, with multiple “punched-out” lesions in the corpus callosum, thalamus, internal capsule, and basal ganglia, especially in the left side. On T2-weighted MRI, “snow ball” appearance of inflammation in the posterior corpus callosum, thalamus, internal capsule, and basal ganglia, especially in the left side, was found [Fig. 2].

Figure 2

(a) T2-weighted magnetic resonance imaging demonstrates “snow ball” appearance of inflammation in the posterior corpus callosum, thalamus, internal capsule, and basal ganglia (b) Axial view

A diagnosis of SS was confirmed. Treatment with intravenous methylprednisolone 500 mg twice a day for 5 days, followed with oral prednisolone 1 mg/kg for 10 days resulted in stabilization of disease with improvement of visual acuity, hemiparesis, hearing and mental status. Four months later, funduscopy and FA showed neovascularization and capillary nonperfused areas in the OS. Sectoral retinal photocoagulation was done. Three months later, at the last follow-up visit, general condition deteriorated with more behavioral changes. BCVA decreased to CF at 4 m (OD) and 3 m (OS). Funduscopy revealed neovascularization in both eyes with extensive capillary nonperfusion areas on FA [Fig. 1e and f]. Therefore, we decided to perform additional PRP and start immunosuppressive therapy.

Discussion

SS is a rare syndrome and it is frequently seen in females of 20–40 years of age with a mean age at symptomatic presentation of 35. Female-to-male ratio is 3:1.[3] Our patient had a typical age of 35 years, but he was male. SS usually presents with a severe headache, transient personality and mental changes, progressive cognitive decline, and later by hearing loss, tinnitus, and segmental visual loss.[4] The first presentation of SS in our patient was severe loss of vision. Unlike our case, in SS, urinary incontinence and generalized seizure may happen, and the low-to-medium frequency sensory neural hearing loss may be permanent.[4]

SS may occur due to a precapillary arteriolar angiopathy and immune-mediated endotheliopathy and occlusion of the microvessels in the brain, retina, and inner ear.[4] SS-associated retinal artery occlusions (multiple BRAOs) are important because similar to our patient they may cause severe visual loss. BRAO also can cause photopsia, black spots, and scintillating scotomas.[2]

A good clue for the rapid diagnosis of SS in our patient was Gass plaques. They are yellow-white atheromatous deposits occur usually at the mid segments of the arterioles and distally located from the arteriolar bifurcations, which are hyperfluorescent on FA. These are caused by slow extravasation of blood lipids into the arteriolar wall at the site of arteriolar wall damage.[5] Similar to our patient, Gass plaques may be a transient finding and disappear during the course of illness.

FA abnormalities serve as a valuable marker, and serial FA may be useful in monitoring the effect of the treatment and early detection of complications such as capillary nonperfusion and new vessel formation.[6]

Seven-Tesla MRI may also aid in differentiating SS from multiple sclerosis (MS). Most white matter lesions in MS are centered on a small vein and are often characterized by a hypointense rim, whereas white matter lesions in SS are less commonly surrounded by an identifiable vessel and rarely exhibit a hypointense rim.[7] SS patients also have more callosal atrophy and cerebrospinal fluid-isointense lesions within the central part of the corpus callosum.[6] Unlike previously reported SS cases,[7] our patient had widespread involvement of thalamus, internal capsule, and basal ganglia, which may point out more progressive course of disease in our patient.

The natural history and outcomes of SS are not fully understood. The disease may be active for several months and the time to remission can be long.[2] There is some limited impairment in most cases on follow-up.[8] In our case, despite corticosteroid therapy, the disease progressed and retinal capillary nonperfused areas extended. In these resistant cases which are refractory to steroids, more potent immunosuppressive therapies such as intravenous immunoglobulin, azathioprine, cyclosporine, cyclophosphamide, methotrexate, mycophenolate mofetil, infliximab, and rituximab can be used.[6]

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Conflicts of interest

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