Sir,

We present a case of Susac syndrome, which is rare, but more common than thought. It is characterised by the triad of retinal arterial occlusion, sensorineural deafness and encephalopathy.1,2 This condition is often under diagnosed or misdiagnosed as multiple sclerosis3 or systemic lupus erythematosus. We also discuss the differential diagnosis especially in the absence of early diagnosis of the disease.

Case report

A 24-year-old Caucasian female was referred by the neurologist, for ophthalmic examination. She gave a history of migraine type of left-sided headache and fixed small scotoma in her left eye. She also complained of decreased hearing. She was previously fit and healthy and denies any past history of eye problems. She was on the oral contraceptive pill. The visual acuity in either eye was 6/6. Fundi showed two cotton wool spots in the left eye with signs of branch retinal arteriolar occlusion (Figure 1). The fundus fluorescein angiography showed leakage from the vessel walls of the small arteries. The 24–2 automated perimetry showed an area of scotoma corresponding to the cotton wool spot.

Figure 1
figure 1

Left fundus photograph showing areas of retinal ischemia due to small arteriolar occlusion.

Full size image

The patient developed encephalopathy the following week and was investigated with an urgent MRI scan. The scan showed T2 weighted high signal discrete areas around the periventricular region (Figure 2), in the white and grey matter and corpus callosum.

Figure 2
figure 2

Coronal T2 weighted image with FLAIR, showing high signal lesions around the periventricular region.

Full size image

The lumbar puncture showed a marginally raised cerebrospinal fluid, a pressure of 26 cm, with no increase in cell count. No oligoclonal antibodies were found in the cerebrospinal fluid. The cerebral angiogram was normal. All the immunological tests were normal. Erythrocyte sedimentation rate was 12 mmHg. Antinuclear antibodies (ANA) titre was negative; Florescent treponemal antibodies (FTA-ABS) and C-reactive protein were normal. An audiogram showed sensorineural deafness.

She was treated with intravenous prednisolone 1 g/kg for 3 days. The response to steroid was remarkable with the patient’s mental status much improved, though her visual complaints were unchanged. The symptoms of encephalopathy subsided within 48 h. She was started on oral steroid of 60 mg/day after that, which was tapered gradually. The MRI was repeated after 2 weeks and the hyper intense areas had almost disappeared (Figure 3). There has been recurrence twice since with symptoms of milder degree during which period the symptoms were treated with an increase in dosage of oral steroid. She is now asymptomatic with 10 mg of oral steroid. At 10 month follow-up after initial presentation, her visual acuity is 6/6 in either eye with small scotoma in the left eye. Left fundus shows old branch retinal arterial occlusion.

Figure 3
figure 3

Almost complete disappearance of the lesions after treatment with steroids.

Full size image

Comment

Susac syndrome was first described independently by Susac in 1976 and since then called by different names like RED-M (retinopathy, encephalopathy, deafness associated with microangiopathy), SICRET (small infarction of cochlear, retinal and encephalitic tissue) or retinocochlear vasculopathy.1,5 This syndrome almost commonly affects women in the 20–40 years age group and is characterised by the clinical triad of encephalopathy, branch retinal artery occlusion and sensorineural hearing loss due to microangiopathy of retina, brain and cochlea. Headache is the usual prodromal symptom. The condition has a chronic relapsing course punctuated by frequent remissions and exacerbations. It is a self-limiting disorder, extending over 1–2 years with remission. The underlying process is believed to be an immunological reaction, leading to small vessel vasculitis4 causing micro infarcts in the retina, brain and the apical turn of the cochlea. The important differentials would be multiple sclerosis, aseptic meningitis, systemic lupus erythematosus, Bechet’s and complicated migraines. The other vasculitides like sarcoidosis, tuberculosis, syphilis and lymphomas have to be ruled out.

A high index of suspicion, leading to early recognition of this syndrome is important because treatment with immunosuppression may minimise permanent cognitive, audiologic and visual sequelae. This syndrome has a good prognosis when treated early. In patients whom early diagnosis has led to early administration of immunosuppressive therapy, recovery can be almost complete.