Susac's Syndrome (Retinocochleocerebral Vasculopathy): Follow-up of a Pediatric Patient.

Susac's syndrome (SS) is a triad of encephalopathy, branch retinal artery occlusion (BRAO), and sensorineural hearing loss as a result of microvascular occlusions of the brain, retina, and inner ear. It is also a disorder of autoimmune endotheliopathy. SS usually affects young women between the age of 20 and 40 years. SS can be misdiagnosed as multiple sclerosis (MS) or acute disseminated encephalomyelitis (ADEM) because of similar findings. A 15-year-old girl presented in June 2015 with vomiting and severe headache. Cerebral magnetic resonance imaging revealed multiple lesions in the corpus callosum. Cerebrospinal fluid findings gave normal results. The initial diagnosis was MS and steroid (1000 mg/day) was given. She started to describe hallucinations and became paraplegic. She then underwent plasmapheresis five times without response. Her electroencephalogram was diffusely slow with 2-3 Hz delta rhythm at the frontal regions. Audiological examination showed that she had sensorineural hearing loss in her left ear. Ophthalmologic evaluation revealed BRAO in both eyes. On the basis of these findings, she was diagnosed with SS and treated with intravenous immunoglobulin (IVIG) and aspirin. After monthly treatment with IVIG for 6 months, the patient has almost fully recovered. SS should be kept in mind in the differential diagnosis of MS and ADEM.

INTRODUCTION

Susac’s syndrome (SS), first reported in 1979, is a triad of encephalopathy, branch retinal artery occlusion (BRAO), and sensorineural hearing loss as a result of microvascular occlusions of the brain, retina, and inner ear.[1] It is a disorder of autoimmune endotheliopathy. SS usually affects young women between the age of 20 and 40 years. It is probably underdiagnosed because of the rarity of the disease and its irregular findings. Childhood SS can be misdiagnosed as multiple sclerosis (MS) or acute disseminated encephalomyelitis (ADEM) because of similar findings.[2]

CASE REPORT

A 15-year-old girl presented in June 2015 with vomiting and severe headache. Cerebral magnetic resonance imaging (MRI) revealed multiple lesions on the corpus callosum [Figure 1A, B]. Cerebrospinal fluid (CSF) protein level was normal. Also oligoclonal band and aquaporin 4 (AQP4) were negatif in CSF. The initial diagnosis was MS and steroids (1000 mg/day) was given for 5 days. The patient started to describe hallucinations and her symptoms did not improve; she became paraplegic due to increased deep tendon reflexes, Babinsky sign was present, and there was loss of bladder function. She then underwent plasmapheresis five times without response. Her spinal MRI and electromyography revealed normal results. Her electroencephalogram (EEG) was diffusely slow with 2–3 Hz delta rhythm especially in the frontal regions [Figure 2A]. Audiological examination showed that she had sensorineural hearing loss in her left ear at low-to-moderate frequencies. The first ophthalmologic examination showed normal results except for cotton wool spots around the optic nerve of her right eye; further evaluation was done and fundus fluorescein angiography (FFA) revealed BRAOs in both eyes. FFA showed BRAOs, nonperfusional (ischemic) areas, cotton wool spots, Gass plaques, retinal hemorrhage, and escape of fluorescein leakage as hyperfluorescence, which indicates active disease [Figure 3A, B, D, E]. On the basis of these findings, she was diagnosed as SS and treated with intravenous immunoglobulin (IVIG) and aspirin. She underwent physiotherapy for the paraplegia. After 3 months, her EEG findings improved and the baseline theta rhythm become alpha and normalized [Figure 2B]; her FFA findings improved. Cotton wool spots and ischemic areas in her left eye improved and the nonperfusional peripheral retinal artery in her right eye become perfusional. The active period of the disease shown by hyperfluorescence (fluorescein leakage) had recovered [Figure 3C, F]. IVIG treatment was given monthly for 6 months. Steroid dosage was slowly tapered and stopped on the third month of treatment. After 11 months control, the retinal nerve fiber layer (RNFL) thickness of her right eye revealed noticeable thinning but the left was normal. Additionally, the macular thicknesses of her both eyes were normal. The peripheral concentric contraction in her right visual field was compatible with the defect in RNFL. Audiological examination at 11 months was normal, and MRI showed findings consistent with a subacute phase (callosal holes; Figure 1E). The patient is taking aspirin only, and her muscle examination of the right lower extremity is 4/5; this is related to involvement of the left internal capsule seen on admission [Figure 1C, D]. She rarely has headaches and her school performance is normal.

Figure 1

(A, B) Sagittal fluid-attenuated inversion recovery and T2 shows multiple small hyperintense foci (snowball images), spokes, and icicles. (C, D) Axial T2 and diffusion-weighted images showing the lesion at the left internal capsule. (E) Follow-up at 11 months after treatment for 6 months: subacute phase images. Sagittal T1 images showing callosal holes

Figure 2

(A)First month: EEG was diffusely slow with 2–3 Hz delta rhythm especially in the frontal regions. (B) Follow-up at 3 months; EEG baseline rhythm is alpha

Figure 3

(A) Left eye color fundus photography; (B) before treatment, black arrow shows active serous fluid escaping from peripheral retinal artery and white arrow shows BRAOs. (C) After treatment, white arrow shows BRAOs have resolved and black arrow shows (hyperfluorescence) active illness has improved. (D) Right eye color fundus photography; arrows show cotton wool spots. (E) White arrow shows BRAOs and black arrow shows ischemic areas. (F) After treatment, ischemic areas are resolved, and black arrow indicates Gass plaque with hyperfluorescence

DISCUSSION

SS affects women aged 20–40 years and has been reported in patients aged 7–70 years.[3] The triad of criteria for SS develops over time, starting with headache in most cases. Psychiatric problems and the other symptoms of the triad take months to develop. Urinary incontinence and seizures have also been reported.[4] Characteristic MRI findings include white matter disturbances, lesions of the corpus callosum (snowball, icicle, spoke), and intracranial leptomeningeal enhancement.[5]

Ocular involvement via BRAOs is always present, and BRAO can lead to bilateral vision loss or remain asymptomatic; this depends on the location of retinal involvement. Peripheral involvement may not cause symptoms so the first ophthalmologic examination can be normal.[46] If SS is suspected, FFA should be done. BRAOs may be the first symptom and recurrent BRAOs may be seen on follow-up (which means occlusion of some branches of the retinal artery due to endothelial injury) for a diagnosis of SS. Ophthalmologic examination shows an area of retinal infarction. Other findings include Gass plaques, cotton wool spots, retinal artery occlusions, areas of arterio-arterial, retinal collaterals and intra-retinal blot hemorrhages, and venous–venous collaterals.[3] Dilated fundus examination will reveal BRAOs, which are best evaluated with FFA; this may show typical multifocal fluorescein leakage and arteriolar wall hyper fluorescence (Gass plaques), which are yellow-white deposits often proximal to sites of occlusion that suggest endothelial dysfunction rather than an embolic disorder.[78] After 6 months of IVIG treatment, ophthalmological findings improved except the distinct thinning in her right RNFL and peripheral concentric contraction in her right visual field were still present. Sensory neuronal hearing loss occurs as a complication of cochlear apex arteriolar microinfarctions at the low and medium frequency range and this may be permanent; if severe, cochlear implantation is necessary.[6] Our patient’s triad of symptoms improved after IVIG treatment. At the end of treatment, she was nearly fully recovered.

CONCLUSION

SS is an important differential diagnosis in numerous disorders such as MS and ADEM. FFA must be done if there is suspicion of SS despite a normal ophthalmologic examination. SS should be suspected in cases of isolated encephalopathy, hearing loss, and visual field defects, because early treatment seems to improve outcomes.

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