Highlights
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Background and objective
Susac syndrome (SuS) is an inflammatory condition of the brain, eyes and ears. Diagnosis can be challenging, and misdiagnosis is common.
Methods
This is a retrospective review of the medical records of 32 adult patients from an Australasian cohort of SuS patients.
Results
An alternative diagnosis was made before SuS in 30 patients (94%), and seven patients received two or more diagnoses. The median time to diagnosis of SuS was 3 months (range 0.5-100 months).
The most common misdiagnoses were migraine in 10 patients (31%), cerebral vasculitis in six (19%), multiple sclerosis in five (16%), and stroke in five (16%). Twenty-two patients were treated for alternative diagnoses, 10 of whom had additional clinical manifestations before the diagnosis of SuS.
At the time of presentation, seven patients (22%) met criteria for definite SuS, 19 (59%) for probable SuS, and six (19%) for possible SuS. Six patients (19%) presented brain-eye-ear involvement, 14 brain-ear involvement (44%), six brain-eye involvement (19%) and six (19%) only brain involvement.
In patients with the complete triad of symptoms, the median delay to diagnosis was 3 months (range, 1 to 9 months) compared with 5.25 months (range, 0.5 to 100 months) for patients with encephalopathy and ocular symptoms. at the time of presentation.
Conclusions Patients with Susac syndrome are frequently misdiagnosed at initial presentation, although many have symptoms or radiological features that are red flags for the diagnosis. Delay in diagnosis can lead to patient morbidity. The various ways in which SuS can present, and the physician’s failure to consider or recognize SuS, appear to be the main factors leading to misdiagnosis. |
Factors leading to misdiagnosis
Factors leading to misdiagnosis included insufficient investigation of the patient’s symptoms or failure to screen BEE organs for asymptomatic involvement, which contributed to misdiagnosis in 23 patients, and the radiologist or treating physician was unaware of the known diagnostic features, such as classic MRI findings in 16 patients (50%).
All patients underwent brain MRI with corpus callosum lesions specific for Susac syndrome identified on initial scans in 25 patients (78%). Before making an alternative diagnosis of the 20 patients who presented with auditory symptoms, only six (30%) patients underwent evaluation with audiogram or vestibular function testing and only five (42%) of the 12 patients who presented with visual symptoms underwent evaluation. to evaluation with FFA before an alternative diagnosis was made, one of which was incorrectly interpreted, resulting in a 1-month delay in the diagnosis of Susac syndrome.
The differential diagnosis of Susac syndrome includes common and rare neuroinflammatory diseases, especially multiple sclerosis, genetic diseases such as adult leukoencephalopathy with axonal spheroids and pigmented glia, and miscellaneous diseases including microembolic stroke and Ménière’s disease.
Our study found that migraine, cerebrovascular diseases such as cerebral vasculitis, multiple sclerosis, and stroke were the most common misdiagnoses. Our study also adds other differential diagnoses to this list, including histoplasmosis, viral encephalitis, Hashimoto’s encephalitis, and CNS lymphoma.
Ophthalmology Susac syndrome is a multilocated arteritis of the head that can affect the eye, ear and brain, often first diagnosed by the ophthalmologist. The diagnosis is reached quickly in uveitis referral centers, but seems to go unnoticed otherwise. A useful angiographic sign to look for is abrupt or segmental arterial stoppage and increased staining of the arterial wall seen more clearly on indocyanine green angiography. Patients often go first to the ophthalmologist, who should act as an informant to avoid serious brain involvement.
Reference : Papasavvas, I., Teuchner, B. & Herbort, CP Susac syndrome (Retino-cochleo-cerebral vasculitis), the ophthalmologist in the role of the whistleblower. J Ophthal Inflamm Infect 10, 27 (2020). https://doi.org/10.1186/s12348-020-00217-z |
Comments
Susac syndrome (SuS) is a disorder believed to be mediated by an autoimmune response to endothelial cells. Patients present with a characteristic clinical triad of encephalopathy, visual disturbances due to arterial branch occlusions, and sensorineural hearing impairment occurring simultaneously or, more often, in succession.
In this article, the authors present a data-based retrospective review of the medical records of 32 adult patients with SuS and conclude that at initial presentation, a significant number of patients (94%) were misdiagnosed, despite many having manifested symptoms or radiological characteristics considered red flags for a diagnosis.
The most common misdiagnoses included migraine, primary cerebral vasculitis, multiple sclerosis, and stroke. Underestimation of specific clinical characteristics and imaging findings in SuS appear to be the main sources of errors and delays in treatment.
Although the incidence of SuS is low (0.024-0.13 per 100,000), 2-4 four reasons make research on SuS important.
- First, there is wide variability in the presentation and course of the disease, and the number of patients is low. At the first evaluation, only 13% to 30% had the complete clinical triad, making diagnosis difficult. Therefore, SuS is underdiagnosed.
- Second, SuS is frequently found in the list of differential diagnoses for many other neurological, psychiatric, ophthalmological, and auditory disorders, and this, as the authors clearly mention, can also be a source of misdiagnosis.
- Third, because the affected organs can suffer irreversible damage, causing blindness, dementia and/or deafness, with a very short window of opportunity for prevention, delay in diagnosis, as the authors also point out, exposes the patients to serious potential disabilities.
- Fourth, the rarity of cases and the varied course of the disease make it difficult to conduct prospective controlled clinical trials exploring new treatment options for SuS.
Current, often aggressive, treatments are based on empirical evidence, mainly from retrospective case series and expert opinion, and reliable objective immune biomarkers to monitor treatment decisions are lacking.
Increasing awareness of SuS and other immune-mediated diseases affecting the brain, eyes and hearing will stimulate research and development of new technologies, which will not only improve our understanding of the underlying pathological mechanisms involved in SuS, but They will also help identify cells and antigens. CNS-specific immune responses, thus paving the way for targeted therapeutic approaches.
In conclusion, the majority of patients with Susac syndrome are not correctly diagnosed at their initial presentation, with the most common misdiagnosis being migraine.
Patients are more quickly diagnosed with Susac syndrome if they present with clinical involvement of all three BEE organs or if they consult a neuroimmunologist. The various ways in which Susac syndrome can present and the doctor’s failure to consider or recognize the key features of Susac syndrome appear to be the main factors leading to misdiagnosis.
