[A case of smoldering anti-leucine-rich glioma-inactivated 1 (LGI1) antibody-associated limbic encephalitis with faciobrachial dystonic seizure]

[Clinical characteristics of seizure-predominant autoimmune encephalitis and utility of anti-neuronal antibody scores for early treatment]

We analyzed 20 patients diagnosed with autoimmune neurological diseases with seizure predominance. In these patients, we examined the usefulness of Antibody Prevalence in Epilepsy and Encephalopathy (APE2) score and Antibodies Contributing to Focal Epilepsy Signs and Symptoms (ACES) score in autoimmune encephalitis (AE) for facilitating early treatment. APE2 score was positive in 19 of 20 patients. ACES score was positive in 15 of 20 patients, and 4 of 5 of the patients with negative ACES score did not have AE. Comprehensive assessment including the use of the above scores is desirable in the early stage of AE.

[Anti-voltage-gated potassium channel (VGKC) complex/leucine-rich glioma-inactivated protein 1 (LGI1) antibody-associated limbic encephalitis mimicking dementia with Lewy bodies in a patient with subacute REM sleep behavior disorder]

A 73-year-old woman was admitted to our hospital owing to abnormal diurnal behavior, sudden brief episodes of impaired awareness, and loud nocturnal sleep talking. Her symptoms had developed gradually over several months and had been treated as dementia with Lewy bodies (DLB) at another clinic. Video-polysomnography revealed brief sleep talking and gross movements associated with REM sleep without atonia. ¹⁸F-FDG PET revealed increased glucose metabolism in both medial temporal lobes. These findings led to a diagnosis of limbic encephalitis (LE) comorbid with REM sleep behavior disorder (RBD). After two courses of intravenous methylprednisolone pulse therapy, her symptoms gradually improved. Her illness was later confirmed as anti-voltage-gated potassium channel (VGKC) complex/leucine-rich glioma-inactivated protein 1 (LGI1) antibody-associated LE using serum analyses. Clinical features of anti-VGKC complex/LGI1 antibody-associated LE can mimic those of DLB, particularly when comorbid with RBD.

Hashimoto's Encephalopathy Presenting with Smoldering Limbic Encephalitis

Hashimoto's encephalopathy (HE) is a steroid-responsive autoimmune encephalopathy associated with Hashimoto thyroiditis. We herein report a case of HE manifesting "smoldering" limbic encephalitis with persisting symptoms and abnormalities on examinations. Although our patient experienced partial clinical remission after treatment, hippocampal hypermetabolism on [18F] fluorodeoxyglucose positron emission tomography (FDG-PET) and subclinical seizures on video electroencephalography persisted. Hypermetabolism on FDG-PET was improved by additional prednisolone therapy. Thus, as with other autoimmune limbic encephalitis cases, HE can take a course of "smoldering" encephalitis. FDG-PET and electroencephalogram findings can reflect the disease activity degree in such patients, although with certain neurophysiological and biochemical distinctions.

Semi-quantitative analysis of cerebral FDG-PET reveals striatal hypermetabolism and normal cortical metabolism in a case of VGKCC limbic encephalitis

In the context of delayed autoimmune encephalitis antibody results, functional imaging can support the diagnosis of limbic encephalitis associated with anti-voltage-gated potassium channel complex (VGKCC) antibodies. Here we present a typical case of VGKCC encephalitis in a 69-year-old woman whose symptoms responded to plasmapheresis. A cerebral 18F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) scan performed prior to commencing treatment revealed striatal hypermetabolism assessed qualitatively and semi-quantitatively, with normal uptake in the cortex and cerebellum when analysed semi-quantitatively. Repeat FDG-PET imaging performed three months later revealed normalisation of striatal hypermetabolism. Previous case reports have described striatal hypermetabolism and/or cortical hypometabolism in patients with VGKCC encephalitis. However, most of these descriptions were based on qualitative analyses only and may represent the relative change in cortical metabolism compared with striatal metabolism. We recommend semi-quantitative analysis of cerebral FDG-PET, in addition to reporting the qualitative FDG-PET images.

Anti-leucine rich glioma inactivated 1 protein and anti-N-methyl-D-aspartate receptor encephalitis show distinct patterns of brain glucose metabolism in 18F-fluoro-2-deoxy-d-glucose positron emission tomography

Background

Pathogenic autoantibodies targeting the recently identified leucine rich glioma inactivated 1 protein and the subunit 1 of the N-methyl-D-aspartate receptor induce autoimmune encephalitis. A comparison of brain metabolic patterns in ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography of anti-leucine rich glioma inactivated 1 protein and anti-N-methyl-D-aspartate receptor encephalitis patients has not been performed yet and shall be helpful in differentiating these two most common forms of autoimmune encephalitis.

Methods

The brain ¹⁸F-fluoro-2-deoxy-d-glucose uptake from whole-body positron emission tomography of six anti-N-methyl-D-aspartate receptor encephalitis patients and four patients with anti-leucine rich glioma inactivated 1 protein encephalitis admitted to Hannover Medical School between 2008 and 2012 was retrospectively analyzed and compared to matched controls.

Results

Group analysis of anti-N-methyl-D-aspartate encephalitis patients demonstrated regionally limited hypermetabolism in frontotemporal areas contrasting an extensive hypometabolism in parietal lobes, whereas the anti-leucine rich glioma inactivated 1 protein syndrome was characterized by hypermetabolism in cerebellar, basal ganglia, occipital and precentral areas and minor frontomesial hypometabolism.

Conclusions

This retrospective ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography study provides novel evidence for distinct brain metabolic patterns in patients with anti-leucine rich glioma inactivated 1 protein and anti-N-methyl-D-aspartate receptor encephalitis.