Clinically relevant increases in serum neurofilament light chain and glial fibrillary acidic protein in patients with Susac syndrome.

BACKGROUND AND PURPOSE: Serum levels of neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP) are promising neuro-axonal damage and astrocytic activation biomarkers. Susac syndrome (SS) is an increasingly recognized neurological condition and biomarkers that can help assess and monitor disease evolution are highly needed for the adequate management of these patients. sNfL and sGFAP levels were evaluated in patients with SS and their clinical relevance in the relapse and remission phase of the disease was assessed. METHODS: As part of a multicentre study that enrolled patients diagnosed with SS from six international centres, sNfL and sGFAP levels were assessed in 22 SS patients (nine during a relapse and 13 in remission) and 59 age- and sex-matched healthy controls using SimoaTM assay Neurology 2-Plex B Kit. RESULTS: Serum NfL levels were higher than those of healthy controls (p < 0.001) in SS patients and in both subgroups of patients in relapse and in remission (p < 0.001 for both), with significantly higher levels in relapse than in remission (p = 0.008). sNfL levels showed a negative correlation with time from the last relapse (r = -0.663; p = 0.001). sGFAP levels were slightly higher in the whole group of patients than in healthy controls (p = 0.046) and were more pronounced in relapse than in remission (p = 0.013). CONCLUSION: In SS patients, both sNFL and sGFAP levels increased compared with healthy controls. Both biomarkers had higher levels during clinical relapse and much lower levels in remission. sNFL was shown to be time sensitive to clinical changes and can be useful to monitor neuro-axonal damage in SS.

Fundamental mechanistic insights from rare but paradigmatic neuroimmunological diseases.

The pathophysiology of complex neuroimmunological diseases, such as multiple sclerosis and autoimmune encephalitis, remains puzzling - various mechanisms that are difficult to dissect seem to contribute, hampering the understanding of the processes involved. Some rare neuroimmunological diseases are easier to study because their presentation and pathogenesis are more homogeneous. The investigation of these diseases can provide fundamental insights into neuroimmunological pathomechanisms that can in turn be applied to more complex diseases. In this Review, we summarize key mechanistic insights into three such rare but paradigmatic neuroimmunological diseases - Susac syndrome, Rasmussen encephalitis and narcolepsy type 1 - and consider the implications of these insights for the study of other neuroimmunological diseases. In these diseases, the combination of findings in humans, different modalities of investigation and animal models has enabled the triangulation of evidence to validate and consolidate the pathomechanistic features and to develop diagnostic and therapeutic strategies; this approach has provided insights that are directly relevant to other neuroimmunological diseases and applicable in other contexts. We also outline how next-generation technologies and refined animal models can further improve our understanding of pathomechanisms, including cell-specific and antigen-specific CNS immune responses, thereby paving the way for the development of targeted therapeutic approaches.

EVALUATION OF TUMOR NECROSIS FACTOR INHIBITOR THERAPY IN SUSAC SYNDROME.

PURPOSE: To evaluate the effect of tumor necrosis factor (TNF) inhibitor therapy on ocular relapses in patients with Susac syndrome. METHODS: Multicenter retrospective cohort study of patients diagnosed with Susac syndrome according to classical clinical criteria. We evaluated the disease activity before and after introduction of anti-TNF therapy and its value as a steroid-sparing agent. RESULTS: Five patients were included. All were initially treated with a combination of corticosteroids and classical immunosuppressive drugs. Infliximab was started in three patients, and adalimumab was started in two patients. Patients had on average 5 ocular relapses during a mean follow-up time of 2.59 years before introducing a TNF inhibitor, corresponding with on average 1.93 relapses per year. After the introduction of an anti-TNF agent, this number was reduced by factor 5.51 to an average of 0.35 relapses per year for a mean follow-up of 2.86 years (P = 0.10). Before anti-TNF introduction ocular relapses occurred at a mean daily dose of 34 mg of prednisone, whereas with anti-TNF treatment, corticosteroid administration could be completely stopped in four patients with one patient still needing 5 mg daily (P = 0.10). Infliximab and adalimumab generally were well tolerated, and no serious adverse events were reported. CONCLUSION: Although not statistically significant, our results suggest that anti-TNF therapy can be a valuable option for the treatment of ocular Susac syndrome and may especially be considered in those patients unresponsive to more conventional immunosuppressive treatment.