Early Presentation of Susac Syndrome in a 7 Year Old

Clinical Correspondence Section Editors: Robert Avery, DO Karl C. Golnik, MD Caroline Froment, MD, PhD An-Guor Wang, MD Early Presentation of Susac Syndrome in a 7 Year Old Robert A. Egan, MD, Adam Brown, MD, Eugenio Grillo, MD S usac syndrome (SS) classically presents with a clinical triad of vision loss, hearing loss, and encephalopathy often heralded by headaches, psychosis, and livedo (1). Vision loss is related to branch retinal artery occlusion. Hearing loss can occur at any frequency but is sensorineural in origin. Neuroimaging results that are highly suggestive of the disorder include the central callosal lesion found on MRI (1). Fluorescein angiography is a very important tool for investigating these patients and is highly sensitive for picking up mild disease affecting the retina. Most cases of SS occur within the years of 20 and 40 but a number of teenagers have been reported in the literature. There is a female sex predilection of 3 to 4 to 1 (1,2). There are no known racial disparities. Not all patients develop the full clinical triad. When not complete, other studies such as the MRI and corpus callosum appearance and the fluorescein angiogram are used to confirm the diagnosis. Prepubertal SS is very rare and we report a 7 year old who developed headache, encephalopathy, and hearing loss whose MRI showed the pathognomonic findings in the corpus callosum. A 7-year-old girl presented with 6 episodes lasting about 5 minutes of limb posturing and dysarthria. This began 6 days before admission and was associated with new onset headache. Just before admission, the patient developed a subjective sense of gait difficulty, school performance decreased, and she became confused and paranoid. Left body shaking was treated with carbamazepine. MRI was performed and showed several callosal lesions, and followup MRI revealed that they had converted to callosal holes (Fig. 1A, B). These lesions were not in the splenium of the corpus callosum. Audiogram demonstrated high-frequency sensorineural hearing loss in the left ear alone. Fundus photographs and fluorescein angiography were normal. She met 2 of the criteria of the Susac triad and had positive central callosal lesions and was considered diagnosis definite, and she was treated with methylprednisolone and intravenous immunoglobulin and improved. After 1 year, the patient’s Department of Neurology (RAE), California Pacific Medical Center, San Francisco, California; Department of Rheumatology (AB), Cleveland Clinic, Cleveland, Ohio; Ambulatorio de Neuropediatria (EG), Hospital Universitário—UFSC, Florianópolis, Brasil; and Serviço de Neurologia (EG), Hospital Infantil Joana de Gusmão, Florianópolis, Brasil. The authors have no conflict of interest Address correspondence to Robert A. Egan, MD, Providence Neurology – Medford, Medford OR 97504; E-mail: [e-mail] e180 medication was stopped and she remained without relapse for 18 months at the time of this report. To date, we are aware of only 2 other reports in the literature of patients developing Susac syndrome in the prepubertal age group (3,4). We have reviewed these 2 case reports and agree that they meet the diagnosis definite criteria set forth recently (1). There are others in the pediatric literature documenting teenage patients. Although our patient is not the youngest on record (4), our report suggests that this disorder that does in fact affect young children and pediatric neurologists, ophthalmologists, otolaryngologists, and rheumatologists should not dismiss the diagnosis because of a very young age. To date, there are 2 reports of diagnostic criteria for SS in the medical literature and they differ slightly on interpretation of the MRI findings as well as fluorescein angiography as well as how much weight each of these modalities adds to the definite diagnosis of the SS patient (1,2). Regarding MRI, the European Susac Consortium states that callosal lesions are not pathognomonic for SS (2), whereas the other report states that they are (1). One hundred percent of subjects in both reports on diagnostic criteria had callosal lesions suggesting that they are the most important neuroimaging finding (1,2). Multiple sclerosis and acute disseminated encephalitis cause lesions in the basal callosum, whereas SS is associated with central lesions. Two other entities of note are when the corpus callosum is affected by mild encephalitis with reversible splenial lesion (MERS) and coronavirus-19 (COVID19), but these 2 entities only cause central callosal lesions in the splenium (5,6), whereas SS can cause central lesions anywhere in the corpus callosum. An argument can be made that the diagnosis is incorrect and that our patient is suffering from some other neurologic FIG. 1. A. T1-weighted MRI in the sagittal plane revealing a callosal hole in the posterior body of the corpus callosum. B. T1-weighted MRI 1 sequence off plane from (A) showing a hole more anterior in the body of the corpus callosum. Egan et al: J Neuro-Ophthalmol 2023; 43: e180-e181 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Correspondence disorder because of the fact that the full clinical triad was not present and the lack of staining on fluorescein angiography; she only had 2 findings of the triad. We believe that the MRI shows the likely pathognomonic finding in SS described previously with subsequent hole formation (1). The reason for this is that our patient had callosal lesions. They were not basal like those seen in multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM). They are not in the splenium like those of MERS and COVID-19. Although the first author here wrote in the past (1) that central callosal lesions (in any part of the callosum) are pathognomonic for SS, the discovery of MERS and COVID-19–related splenium involvement might refute this. However, these latter diseases do not affect the body and head of the callosum, and our patient had body involvement which is not seen in any of these other disorders listed here. A central callosal lesion in the body of the callosum would not suggest a different disorder other than SS. Age can alter the risk of developing certain autoimmune conditions as well as change how the conditions present. Well-known examples of this are IgA vasculitis with most cases presenting in children compared with adults. The presentation of IgA vasculitis is also different in children compared with adults where children more commonly have mild self-limiting disease, and adults commonly have more severe disease with frequent relapse and worse renal outcomes (7). Other autoimmune conditions only affect children, such as Kawasaki disease, or only affect older adults, such as polymyalgia rheumatica and giant cell arteritis. It is unclear why age changes the risk of developing certain autoimmune conditions or why it can change the presentation of the disease. This may help explain why our patient did not develop the full clinical triad. Finally, the authors would like to stress than when faced with a patient with an unusual neurological syndrome that Egan et al: J Neuro-Ophthalmol 2023; 43: e180-e181 does not fit the clinical triad of SS that attention to staining on fluorescein angiography and to MRI callosal findings may help determine that the diagnosis in their patient is SS. STATEMENT OF AUTHORSHIP Conception and design: R. A. Egan, A. Brown, E. Grillo; Acquisition of data: E. Grillo; Analysis and interpretation of data: R. A. Egan, A. Brown, E. Grillo. Drafting the manuscript: R. A. Egan, A. Brown, E. 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