Early detection of adult onset Susac's syndrome in a South Indian female.

Sir,

Since the first description of Susac's Syndrome (SS) in 1979, about 304 cases of SS have been reported,[1] mainly in Western countries. To the best of our knowledge, it is a case of adult onset of SS diagnosed at early stage reported first time from south India and it is the second case reported from India.

A 26-year-old woman presented with headache of one year. It was insidious onset, gradually progressive in nature.. She had visual disturbances for 2 months and decreased left-sided hearing since 1 month. Blurring of vision was mainly involving the left eye in nasal fields. She felt continuous tinnitus in left ear with decreased hearing. She had no features of increased intracranial pressure (ICP). Her electroencephalogram (EEG) was within normal limit. Her blood investigation for vasculitis work up was negative. Magnetic resonance imaging (MRI) brain showed T1W hypointense lesions in body of corpus callosum [Figure 1a]. There was no contrast enhancement on post-contrast sagittal T1-weighted (T1W) image [Figure 1d]. Color fundus photography of her right eye [Figure 2a] shows multiple greyish white puffy patches, secondary to retinal artery branch occlusions. Late phase of fluorescein angiogram of right eye revealed blocked choroidal fluorescence in all the three corresponding areas [Figure 2b]. Right eye inferior temporal quadrant late phase angiography, shows [Figure 2c] retinal artery branch occlusion and the left eye posterior pole late phase [Figure 2d] showed blocked choroidal fluorescence due to retinal thickening. Pure tone audiogram (PTA) showed mild sensory neural deafness. Visually evoked potential (VEP) study result is suggestive of demyelinating type of visual pathway defect on the left side. The combination of patient's clinical picture of encephalopathy, branch retinal artery occlusions (BRAOs), and hearing loss in combination with the characteristic imaging features, the patient was diagnosed with SS. She was started on high dose of methylprednisolone (1,000 mg/day) for 5 days, and then tapering dose of oral steroids at the time of discharge. She was relieved from her headache and showed improvement in her vision after 1 month of discharge clinically. She did not return for subsequent follow-up visits.

Figure 1

MRI of brain. (a) Coronal T1W image shows hypointense lesions in body of corpus callosum (arrow), (b) Hypointense on axial FLAIR image (arrow), (c) Hyperintense on T2W image (arrow), and (d) No contrast enhancement on post-contrast coronal T1W image (arrow). MRI = Magnetic resonance imaging, T1W = T1-weighted, FLAIR = Fluid-attenuated inversion recovery, T2W = T2-weighted

Figure 2

(a) Color fundus photograph of right eye shows multiple grayish white patches (arrows). (b) Right eye fluorescein angiogram shows blocked choriodal fluorescence in corresponding areas. (c) Right eye fluorescein angiogram shows retinal artery branch occlusion (arrow). (d) Left eye fluorescein angiogram shows blocked choriodal fluorescence (arrow)

SS is a rare syndrome deFined by the clinical triad of encephalopathy, BRAOs, and hearing loss.[23] Women in their 3rd and 4th decades of life are predominantly affected with a Male: Female ratio of 1:3. The mean age is 28 years with a range of 9-58 years.[4] Headache is the first symptom and it may occur 6 months before the onset of the other symptoms.[5] Encephalopathy can manifest as headache, confusion, memory loss, behavioral changes, ataxia, and dysarthria.[23678] Involvement of the corpus callosum, inparticular, evidence of ‘snowball lesions’ is considered a characteristic sign of this syndrome.[9] Many lesions in the corpus callosum become cystic within a period of 4 weeks, which is highly suggestive of microinfarcts rather than demyelination, and it can be used to differentiate demyelinating disease.[4] Optic changes include scotoma and visual distortion; however, BRAOs may occur at the periphery and not result in clinical deficits. Hearing loss, usually in the low to mid frequencies, may be associated with roaring tinnitus and vertigo.[378] In general, encephalopathic symptoms and visual disturbances can often be treated and may remit; however, hearing loss is often irreversible.[3]

Autoimmune process is the alleged etiology for this disease,[35] but the exact etiology and pathogenesis are still unknown. An immune response triggered by prior infection has been suggested.[6] Although, SS is a self-limiting disease, if not diagnosed and treated early it might lead to permanent hearing and visual loss. Susac et al., recommended the treatment, which includes pulse of methylprednisolone, intravenous immunoglobulin, oral prednisone, and cyclophosphamide.[5] Similar strategy, using high dose methylprednisolone and then tapering dose of oral steroids at the time of discharge helped our case with considerable improvement. In conclusion, early detection of the syndrome is important because it may minimize permanent cognitive, audiologic, and visual sequelae.