Susac's Syndrome in a 27-Year-Old Female.

A 27-year-old woman was referred by the neurologist for ophthalmic examination. She had a history of headache, visual loss in her right eye, four-limb paresthesia, and behavioral changes over the previous 10 months. The patient complained of tinnitus and hearing loss for two weeks. The patient was initially diagnosed with multiple sclerosis, but auditory and retinal involvement (small branch retinal artery occlusion in fluorescein angiography) raised the possibility of Susac's syndrome.

INTRODUCTION

Susac's syndrome is an extremely rare neurological disorder characterized by symptoms and signs involving a clinical triad of encephalopathy, retinopathy, and hearing loss. These problems arise because of damage to the microangiopathy of vessels that supply the brain, the retina, and cochlea or an autoimmune endotheliopathy.12 This disorder is usually seen in young women.3 The retinopathy is characterized by multiple peripheral retinal arteriolar branch occlusions that can be seen on ophthalmoscopic examination or retinal fluorescein angiography. The occlusions may be quite extensive or may be very subtle.45

In this case report, we present a patient with the classic triad signs of Susac's syndrome.

CASE REPORT

A 27-year-old woman was referred by a neurologist, for ophthalmic consultation. She had a history of headache, visual loss in her right eye and four-limb paresthesia over a period of 10 months prior to presentation. During this period, the patient had developed behavioral and mood changes such as depression, paranoia, and memory loss. The primary diagnosis was multiple sclerosis and she was treated with intravenous methylprednisolone (1 g / day) for three days followed by 1 mg / kg / day of prednisone administered orally for six weeks then tapered weekly over the next four months. The response to the steroid was remarkable for paresthesia, but the visual loss remained. The patient also complained of tinnitus and hearing loss for two weeks, prior to admission.

Magnetic resonance imaging (MRI) before steroid treatment demonstrated nonspecific periventricular high signal intensity foci in the white matter and a few high signal intensity foci in the corpus callosum [Figures 1 and 2].

Figure 1

Axial T2-weighted fluid attenuated inversion recovery image of the brain shows multiple nonspecific foci of T2 signal abnormality in the periventricular white matter (arrows)

Figure 2

A coronal T2 image shows small, hyperintense lesions in the periventricular white matter (arrows)

Cerebral arteriography was normal. Spinal fluid examination revealed a high protein concentration of 250 mg / dL with no cells and no oligoclonal immune globulin. Full laboratory evaluations including tests for brucella, syphilis, and collagen vascular disease were normal, except the erythrocyte sedimentation (ESR) rate, which was mildly elevated as 38 mm / hour. An audiogram showed mild right ear sensorineural deafness at lower frequencies. The patient complained of fluctuating tinnitus and could not be elicited sufficiently during the examination. Based on the above-mentioned findings, the diagnosis of multiple sclerosis (MS) was unlikely and the neurologist suspected Susac's syndrome and referred the patient for an ophthalmic evaluation.

On examination, she was awake, but had a blunted affect and was difficult to engage. Motor and sensory examinations were normal. The visual acuities in the right and left eyes were 20 / 30 and 20 / 20, respectively. Slit lamp examination was normal. The funduscopy and fluorescein angiographies were normal in the left eye. The right eye fundus was normal [Figure 3]. Fluorescein angiography of the right eye showed a small superior macular branch artery occlusion and perivascular sheathing near the optic disc [Figure 4]. Perimetry showed a central scotoma with a macular problem [Figure 5]. With the confirmation of cerebral, cochlear, and retinal involvement, a diagnosis of Susac's syndrome was made. After initial corticosteroid treatment, the disease remitted and did not recur on a two-year follow-up. Hence, further treatment was not administered.

Figure 3

Normal fundus photograph

Figure 4

Fluorescein angiography (late phase) depicts a hypofluorescent area (arrow) due to non-filling of the super temporal artery and leakage of inferior optic disc-retinal arteries (arrowheads)

Figure 5

Perimetry shows the central scotoma consisting of the macular problem

DISCUSSION

To our knowledge, we report the first Susac's syndrome patient in Iran. She presented with encephalopathy associated with headache, some behavioral changes, and paresthesia, and was diagnosed initially with multiple sclerosis. Subsequent to evolving hearing loss an ophthalmic examination was performed to confirm Susac's syndrome. The diagnosis was made by the recognition of the clinical triad and the MRI findings.13–6

Similar to the current case, some patients may present with an incomplete form of the syndrome. Analyzing the subclinical cases, Petty et al.7 found that 97% of the patients did not have the clinical triad at the time of onset. In some patients, the triad was completed after a delay of weeks, up to more than two years.

Headache has been reported to be the most common prodromal symptom that may appear several months prior to the development encephalopathy. Most patients have abnormalities in cognition, memory, and behavior, as our patient. In previously reported cases,147 patients had variable degrees of dysarthria, paresthesia hyperesthesia, dysmetria, cranial nerve palsies, and seizures.

Fluorescein angiography in our patient showed a small macular branch occlusion and vasculitis. Retinal ischemic whitening caused by BRAOs was the most common fundus finding in Susac's syndrome.1 Other findings during the acute phase include cotton-wool patches, periarterial whitening, box-car segmentation, and cherry-red spot. During the later stages, retinal arterial wall plaques, diffuse narrowing of the arterioles, and zones of peripheral capillary closure may occur.48

Similar to our case, the fundus is sometimes considered normal when the occlusions are confined to the small arterioles in the retinal periphery. Retinal fluorescein angiography is the best method for detecting retinal arteriolar occlusions. It may also show leakage of the dye as observed in our case.45

Magnetic resonance imaging is the neuroimaging technique of choice. Findings include multiple small foci of high T2 signal intensity and contrast enhancement throughout both the gray and white matter in the cerebrum and infratentorial structures. In this syndrome, the lesions in the corpus callosum and periventricular white matter might be due to microinfarctions.56 Our case showed similar MRI findings. The most important differential diagnosis of Susac's syndrome is MS because of results during MRI imaging, such as, hyperintensity of white matter and corpus callosum. However, in contrast to Susac's syndrome, the cortex is, for the most part, not affected in MS, and in addition, it is generally concentrated on the white matter.5–7

The published cases mostly demonstrate a loss of lower frequencies in pure tone audiometry, corresponding to a lesion on the apical coil of the cochlea.4 If a case of Susac's syndrome is assumed, audiometry is obligatory because the neurological symptoms may obscure acute hearing loss. In contrast to our patient, some patients suffer rapid hearing impairment, even up to deafness.

Thus far, there have been no clinical trials of treatment for Susac's syndrome. Some patients have improved without receiving any treatment whereas others have responded very well to corticosteroid alone. Our patient responded well to Prednisone who followed a monocyclic course. Other patients may require a combination of prednisone withintravenous immunoglobulin and / or cyclophosphamide or mycophenylate mofetil.9