A Case Report on Susac Syndrome
Susac syndrome (SS) is a rare and complex disorder characterized by a triad of symptoms: encephalopathy, branch retinal artery occlusion (BRAO), and sensorineural hearing loss. This syndrome, first described in 1979 and formally named in 1994, is caused by microangiopathy affecting the brain, retina, and cochlea. Despite its rarity, with only approximately 300 cases reported worldwide, SS presents significant diagnostic and therapeutic challenges. This case report details the clinical presentation, diagnostic process, and treatment of a 41-year-old female patient diagnosed with SS, providing valuable insights into this enigmatic condition.
The patient, a 41-year-old woman, was admitted to the Department of Neurology on October 27, 2017, with acute symptoms of vertigo, vomiting, and fatigue lasting for one day. Upon admission, her blood pressure was significantly elevated at 202/120 mmHg. An initial brain computed tomography (CT) scan revealed multiple lacunar cerebral infarctions, prompting further investigation. The patient also reported blurred vision and a foreign-body sensation in her eyes, which had begun approximately two weeks prior to admission.
A comprehensive ophthalmologic examination was conducted to assess the patient’s visual complaints. Her visual acuity was severely impaired, measuring 0.16/light perception in both eyes. Intraocular pressures were within normal limits at 17/19 mmHg. Slit-lamp examination showed no abnormalities in the eyelids, lashes, conjunctiva, sclera, corneas, anterior chambers, irises, lenses, or vitreous. However, the left pupil was slightly dilated with a blunted light reflex, suggesting potential neurologic involvement.
Fundus examination revealed significant retinal abnormalities. In the right eye, spot-like hard exudates were observed around the inferior temporal branch artery. In the left eye, blocked arterioles were evident in all branches of the retinal artery periphery, with complete occlusion of the superior temporal branch. Optical coherence tomography (OCT) of the right eye showed no abnormalities, while the left eye exhibited thinning of the inner retinal layers and high reflection in the ellipsoid zone of the macular area and the outer segment of the photoreceptor cells. Due to the patient’s poor physical condition, fluorescein angiography (FA) was not performed.
Magnetic resonance imaging (MRI) of the head provided further evidence of the disease’s neurologic impact. Multiple hypointense lesions on T1-weighted images and hyperintense lesions on T2-weighted images were observed in the brainstem, bilateral basal ganglia, internal capsule-radiation crown, outer capsule area, thalamus dorsalis, right insular lobe, corpus callosum, and central ovale. Some lesions had unclear boundaries, indicating ongoing pathologic processes. Diffusion-weighted imaging (DWI) highlighted hyperintense lesions in the corona radiata, thalamus dorsalis, corpus callosum, and central ovale. Fluid-attenuated inversion recovery (FLAIR) images demonstrated hyperintense foci in the deep white matter of the frontal, occipital, and parietal lobes, as well as near the bilateral ventricles. These lesions did not enhance with contrast material, ruling out certain differential diagnoses such as tumors or infections. Magnetic resonance angiography (MRA) showed naturally coursing cerebral arteries with nonsmooth vascular walls but no significant stenosis.
Audiologic evaluation confirmed sensorineural hearing loss, a hallmark of SS. Pure-tone audiometry revealed severe deafness in the left ear and deafness in the right ear. Left acoustic immittance testing showed a type A tympanogram, indicating normal middle ear function and further supporting the diagnosis of cochlear involvement.
Laboratory investigations were conducted to identify potential risk factors or underlying causes. Routine blood tests revealed elevated levels of platelets, white blood cells, and neutrophil granulocytes, along with decreased hemoglobin levels. Urine analysis showed increased epithelial cells and significantly elevated red and white blood cells. Serum triglycerides and very-low-density lipoproteins were also elevated. Additional tests for autoantibodies associated with vasculitis, antineutrophil cytoplasmic antibodies (ANCA), and erythrocyte sedimentation rate (ESR) were normal, while C-reactive protein (CRP) levels were slightly elevated.
Based on the clinical presentation, imaging findings, and laboratory results, a diagnosis of Susac syndrome was established. The patient was initiated on high-dose intravenous methylprednisolone (500 mg per day) for three days, followed by oral prednisone (60 mg once daily) with a gradual taper. After one week of treatment, her symptoms of vertigo and headache improved, and she was discharged from the hospital.
Susac syndrome is a rare condition with an unclear pathogenesis, though an autoimmune etiology is widely presumed. Studies have reported the presence of anti-endothelial antibodies in up to 30% of patients, and immunosuppressive therapy has shown favorable outcomes. The syndrome predominantly affects women, with a female-to-male ratio of 3:1. The classic triad of encephalopathy, BRAO, and sensorineural hearing loss is present in only 13% of cases at initial presentation, but most patients develop all three symptoms over weeks or months.
The differential diagnosis of SS includes disseminated sclerosis, primary central nervous system lymphoma, infectious cerebral arteritis, central nervous system sarcoidosis, and systemic lupus erythematosus. The absence of a standardized treatment protocol underscores the complexity of managing this condition. Current therapeutic approaches focus on immunosuppression and immunoregulation, with corticosteroids being the mainstay of treatment. Adjunctive therapies such as anticoagulants, antiplatelet agents, and calcium channel blockers may also be employed. Emerging treatments, including high-dose intravenous immunoglobulin and hyperbaric oxygen therapy, have shown promise in some cases.
The natural course of SS is typically self-limited, with a monophasic or wavy progression. Most patients stabilize or experience symptom relief within two years, emphasizing the importance of early diagnosis and intervention. Timely treatment can significantly improve prognosis and reduce the risk of long-term complications.
In conclusion, Susac syndrome is a rare but debilitating condition that requires a high index of suspicion for accurate diagnosis. This case report highlights the importance of a multidisciplinary approach, combining clinical evaluation, advanced imaging, and laboratory testing to identify and manage this complex disorder. Early recognition and aggressive immunosuppressive therapy are crucial for achieving favorable outcomes in patients with SS.
doi.org/10.1097/CM9.0000000000000909
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