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Autoimmune encephalitis associated with autoantibodies to the gamma-aminobutyric acid B receptor (GABA B R-AE) typically involves limbic symptoms with limbic abnormalities visible in brain magnetic resonance imaging (MRI). We herein report a case of a 48-year-old man with GABA B R-AE whose initial presentation was limited to syncope without limbic symptoms or MRI abnormalities. Interestingly, serial MRI also revealed no abnormalities even after the appearance of limbic symptoms. Our findings suggest that GABA B R-AE can initially mimic common syncope and that MRI findings may remain normal throughout the clinical course. Even if patients have normal MRI findings, GABA B R-AE should be considered if limbic symptoms worsen.

Purpose: Hashimoto encephalopathy (HE) is an autoimmune-mediated encephalopathy associated with anti-thyroid antibodies. We previously discovered serum autoantibodies against the NH 2 -terminal of α-enolase (NAE), which serve as a specific diagnostic biomarker for HE and may be involved in the autoimmune pathophysiology of HE, including vasculitis. Although the common findings of brain magnetic resonance imaging (MRI) in HE have been recognized as normal or non-specific white matter lesions, serial MRI changes have been less well studied. The aim of this study was to clarify detailed and longitudinal MRI changes in HE associated with anti-NAE antibodies., Methods: We investigated serial brain MR images in 12 Japanese patients with HE who had serum anti-NAE antibodies., Results: Brain MRI showed diffuse white matter abnormalities and/or multiple small subcortical lesions in 10 patients. These lesions were apparently non-specific; however, in 7 of these patients we observed expanding and diminishing white matter lesions, emerging subcortical high-intensity spots on diffusion-weighted images, or reversible limbic lesions, which worsened at relapse and improved after recovery following immunotherapies., Conclusion: MRI lesions that fluctuate according to the disease condition were frequently observed in HE patients with anti-NAE antibodies, which suggests that these fluctuation may be associated with the autoimmune pathophysiology of HE., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Several types of autoantibodies have been reported in autoimmune limbic encephalitis (LE), such as antibodies against the voltage-gated potassium channel (VGKC) complex including leucine-rich glioma inactivated 1 (LGI1). We recently reported a patient with autoimmune LE and serum anti-NH2-terminal of α-enolase (NAE) antibodies, a specific diagnostic marker for Hashimoto encephalopathy (HE), who was diagnosed with HE based on the presence of antithyroid antibodies and responsiveness to immunotherapy. This case suggests that LE patients with antibodies to both the thyroid and NAE could be diagnosed with HE and respond to immunotherapy. The aim of this study was to clarify the clinicoimmunological features and efficacy of immunotherapy in LE associated with anti-NAE antibodies to determine whether the LE is a clinical subtype of HE.We examined serum anti-NAE antibodies in 78 LE patients with limbic abnormality on magnetic resonance imaging and suspected HE based on positivity for antithyroid antibodies. Nineteen of the 78 patients had anti-NAE antibodies; however, 5 were excluded because they were double positive for antibodies to the VGKC complex including LGI1. No antibodies against the N-methyl-D-aspartate receptor (NMDAR), contactin-associated protein 2 (Caspr2), γ-aminobutyric acid-B receptor (GABABR), or α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) were detected in the 19 patients. Among the remaining 14 who were positive only for anti-NAE antibodies, the median age was 62.5 (20-83) years, 9 (64%) were women, and 8 (57%) showed acute onset, with less than 2 weeks between onset and admission. Consciousness disturbance (71%) and memory disturbance (64%) were frequently observed, followed by psychiatric symptoms (50%) and seizures (43%). The frequency of these symptoms significantly differed between the acute- and subacute-onset groups. Abnormalities in cerebrospinal fluid and electroencephalogram were commonly observed (92% for both). Tumors were not identified in any cases. All patients responded to immunotherapy or spontaneously remitted, thereby fulfilling the criteria of HE.This study demonstrated that LE associated with anti-NAE antibodies is a nonparaneoplastic LE and various limbic symptoms that depend on the onset type. Favorable therapeutic efficacy suggests that this LE can be considered a clinical subtype of HE and that anti-NAE antibodies may be a promising indicator of the need for immunotherapy.