<span><b>Background:</b> Anti-NMDAR encephalitis is the most frequent cause of autoimmune encephalitis. Chikungunya (CHIK) is an arbovirus responsible for outbreaks of fever, cutaneous rash and arthritis in underdeveloped countries, and a trigger for autoimmunity.
Abstract Detection of a neural autoantibody can confirm diagnosis and guide patient management and treatment. Recent recommendations suggest concurrent serum and cerebrospinal fluid (CSF) testing. However, most studies on prevalence of these autoantibodies have focused on serum testing. Herein we performed a retrospective review of CSF specimens submitted to Mayo Clinic Laboratories for CSF panel (Encephalopathy, Dementia, Paraneoplastic or Epilepsy) testing. Autoimmune encephalitis-associated and other autoimmune neurologic disorder-associated autoantibody prevalence was evaluated in conjunction with ordering patterns for CSF testing only or paired with serum testing to evaluate the clinical relevance of autoantibody testing in CSF. An overall positivity rate of 4.63% (112/2420) was observed, with 95.54% (107/112) CSF specimens positive for a single autoantibody. The CSF positivity rates were highest for antibodies associated with autoimmune encephalitis (GAD65>NMDA>GABA-B>LGI1>AMPA>VGKC) except CASPR2 which was not detected, while antibodies associated with paraneoplastic syndrome were less prevalent (ANNA-1/Hu>PCA-1/Yo>CRMP-5/CV2>AGNA-1/SOX-1>PCA-2) or not detected (amphiphysin, ANNA-2/Ri, ANNA-3 and PCA-Tr). Most CSF specimens (62.56%; n=1514) did not have a paired serum submitted for testing. Of 906 CSF/serum pairs, only 49 were CSF autoantibody positive. Rarely were antibodies identified in CSF with negative serum results while antibodies were more frequently identified in serum with negative CSF results. These data indicate that test utilization for neural autoantibodies in CSF could be substantially improved by basing ordering practices on clinical manifestations and autoantibody prevalence.
Abstract Along with the rapidly expanding spectrum of autoimmune encephalitis (AE), probable AE with no detected autoantibody (AE-NoDab) has become a major category of AE. However, its clinical features, treatment, and prognosis were not demonstrated. In our institutional cohort of all consecutive patients with possible AE in 2012 – 2018, patients diagnosed with AE-NoDab were included in this study. AE-NoDab was subcategorized into limbic encephalitis (LE), acute disseminated encephalomyelitis (ADEM), and antibody negative probable AE (pAE). Patients’ clinical severity was assessed at every week for the first 12 weeks, at every month for the next 9 months, and then at every three months, using the modified Rankin scale (mRS) and the Clinical Assessment Scales in Autoimmune Encephalitis (CASE, score range 0–27) scores. Combination immunotherapy regimens used at each time point were categorized as steroid+immunoglobulin (SI), SI+Rituximab (anti CD-20 mAb, SIR), and SIR+ Tocilizumab (anti IL-6 mAb, SIRT). 136 patients (LE 52[38.2%], ADEM 14[10.3%], and pAE 70 [51.5%]) were followed-up for 39.0±19.6 (range 10–80) months. At last follow-up, 76 (55.9%) patients had favorable mRS outcomes (scores 0–2). Compared to 55 anti-NMDA receptor encephalitis patients, baseline severity was higher, use of immunotherapy was lower, and outcome was poorer in AE-NoDab. There was no difference in clinical characteristics, treatment, and outcomes among subcategories of AE-NoDab. In a linear mixed model analysis, using the SIRT regimen was more effective than conventional regimens such as SIR or SI in lowering CASE scores (both, P=0.001). Early diagnosis and use of combined immunotherapy consisting of SIRT is warranted to improve the poor outcomes of AE-NoDab.