Metabolic topography of autoimmune non-paraneoplastic encephalitis

Role of FDG PET/CT in definitive and presumed autoimmune encephalitis

OBJECTIVE

F-18 Fluorodeoxyglucose PET/CT (FDG-PET) is emerging as a useful imaging adjunct to MRI in the initial diagnostic evaluation of autoimmune encephalitis (AIE)-though presently it is not included in the diagnostic criteria.

MATERIALS AND METHODS

In this prospective study we enrolled a total of 52 patients with clinically diagnosed and treated AIE. MRI evaluation was done in each case along with CSF and EEG where feasible. FDG-PET was done for all and images were interpreted visually and using SPM.

RESULTS

The mean age group of patients included was 38.5 ± 22.6 years with 31 females and 21 males. 23 antibody-positive cases underwent PET, the most common antibody detected was anti-NMDAR type followed by anti-LGI 1. Most common metabolic pattern in NMDARE was hypermetabolism in basal ganglia and hypometabolism in parieto-occipital cortices and ovarian teratoma was detected in two of these patients on whole-body PET. A metabolic pattern consistent with AIE was demonstrated in 22/29 (75.8%) antibody-negative patients with hypermetabolism in basal ganglia and mesial temporal cortices. The overall sensitivity of FDG PET was 86% (45/52). MRI abnormalities were detected in 22/52 (42%) cases, 10/23 antibody positive and 12/29 antibody negative cases. PET was positive in 23/30 (76%) MRI negative cases.

CONCLUSION

Sensitivity of FDG PET for supporting a diagnosis of AIE was higher compared to MRI in both antibody-positive (definitive) and antibody-negative (presumed) AIE. Specific metabolic patterns can be demonstrated on FDG PET in AIE, prompting an early diagnosis so that timely treatment can be instituted.

Autoimmune encephalitis related to LGI1 antibodies with negative MRI study: Description of two cases

BACKGROUND

Leucine-rich glioma inactivated 1 (LGI1) antibody-related autoimmune encephalitis is easily misdiagnosed clinically because of its complex and diverse clinical manifestations. We present two cases of LGI1 antibody-related encephalitis with negative imaging findings and perform a literature review on this disease entity.

CASE DESCRIPTION

The first case was that of a 60-year-old man who presented with involuntary movement of the paroxysmal right limb. The second case was that of a 66-year-old man who presented with hearing hallucinations, involuntary shaking of the right limb, and progressive cognitive impairment. Both patients in this study showed negative magnetic resonance imaging (MRI) results. Routine cerebrospinal fluid (CSF) and biochemical examinations showed no significant abnormalities, and positive LGI1 antibodies were detected in both the CSF and serum.

CONCLUSION

Based on our experience and the literature review, we recommend that LGI1 antibody-related encephalitis should be considered when faciobrachial dystonic seizures, acute and subacute-onset seizures, low serum sodium (possibly with low CSF chloride), and cognitive-psychiatric disorders are encountered, even in the absence of specific radiographic and altered CSF findings.

Enhancing the clinical diagnosis of the acute and subacute phases of autoimmune encephalitis and predicting the risk factors: the potential advantages of 18F-FDG PET/CT

BACKGROUND

2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography (18F-FDG PET) could help evaluate metabolic abnormalities by semi-quantitative measurement to identify autoimmune encephalitis (AE). Few studies have been conducted to analyze the prognostic factors of AE. The study aimed to explore the values of diagnosis and treatment evaluation by 18F-FDG PET and preliminarily discussed the potential value in predicting the prognosis of AE patients.

METHODS

AE patients underwent 18F-FDG PET/CT and magnetic resonance imaging (MRI). There were two steps to analyse 18F-FDG PET imaging data. The first step was visual assessment. The second step was to analyse 18F-FDG PET parameters using Scenium software (Siemens Molecular Imaging Ltd). The mean standardized uptake value (SUVmean) and maximum standardized uptake value (SUVmax) of brain relative regional metabolism (BRRM) were quantified in the case and control groups according to the anatomical automatic labeling (AAL) partition. The main statistical method was the Kruskal-Wallis test. Finally, the simple linear regression method was used to analyse the relationships between 18F-FDG PET parameters and the modified Rankin Scale (mRS) scores before and after treatment.

RESULTS

The results on 18F-FDG PET showed that visual assessment abnormalities were in the mesial temporal lobe (MTL) (70.8%), (mainly infringing on the hippocampus and amygdala), basal ganglia (62.5%), frontal lobes (37.5%), occipital lobes (29.2%), and parietal lobes (12.5%). The positive rate of abnormalities on 18F-FDG PET was more sensitive than that on MRI (95.5% vs 32.2%, p = 0.001). The number of lesions on PET was positively correlated with the mRS scores before and after treatment, and the correlation before treatment was more significant. Before treatment, the SUVmean of the left occipital lobe was the most remarkable (SUVmean, R2 = 0.082, p > 0.05) factor associated with the mRS score, and the correlation was negative. With regard to prognosis, the SUVmax of the MTL was the most notable (R2 = 0.1471, p > 0.05) factor associated with the mRS score after treatment, and the correlation was positive.

CONCLUSIONS

18F-FDG PET could be more sensitive and informative than MRI in the early phases of AE. The common pattern of AE was high MTL metabolism on 18F-FDG PET, which was associated with hypometabolism of the occipital lobe, and the number of lesions on PET before treatment may be significant factors in assessing disease severity. The SUVmax of MTL hypermetabolism may serve as a prognostic biomarker in AE.

Typical metabolic pattern of 18F-FDG PET in Anti-NMDAR encephalitis in the acute and subacute phases and its correlation with T2 FLAIR-MRI features

BACKGROUND/AIMS

Early diagnosis of Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis with non-invasive imaging modalities benefiting is crucial to guarantee prompt treatments decision-making and good prognosis for patients. The present study aimed to explore the correlation of MRI features with brain metabolism characteristics of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) and to describe the metabolic patterns in Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis at acute and subacute phases. Twenty-four patients with anti-NMDAR encephalitis confirmed by serum and/or CSF tests at acute and subacute phases, 9 females and 15 males, with an age range of 6-80 years, were enrolled in this retrospective study as encephalitis group. 18F-FDG PET and MRI findings of all patients were investigated and interpreted with visual analysis. Chi-square test was performed to compare the diagnostic sensitivity between MRI and PET. Independent sample t-test was used to compare the standardized uptake value ratio (SUVR) of each ROI between the encephalitis group and control group, which consisted of 24 healthy volunteers of the same age and gender.

RESULTS

There was no statistical difference in the diagnostic sensitivity between FDG PET (23/24, 95.83%) and MRI (18/24, 75.00%) in anti-NMDAR encephalitis patients (P > 0.05). Three categories of abnormalities shown on T2 FLAIR, including shallow of sulci and swelling of brain tissue, increased signal in the sulci, increased signal on brain gray matter or adjacent white matter presented hypermetabolism on PET, excepting increased signal in brain linear structure with hypometabolism of the basal ganglia on PET. We identified 19 brain regions with hypermetabolism and 16 brain regions with hypometabolism that exhibited statistically significant changes in SUVRs between anti-NMDAR encephalitis group and control group (FDR P < 0.05).

CONCLUSION

Anteroposterior glucose metabolism gradient (frontal-temporal/parietal-occipital) is proved to be a typical pattern of anti-NMDAR encephalitis at the acute and subacute phases in both visual and statistical testing. Interestingly, the pattern is also commonly found in the anterior and posterior portions of the parietal lobe and cingular cortex, which may be a potential indicator for the diagnosis of this disorder. In addition, MRI is an important and reliable neuroimaging modality to assist in the correct evaluation of activity changes on individual 18F-FDG PET.

Spatial and Ecological Factors Modulate the Incidence of Anti-NMDAR Encephalitis-A Systematic Review

Anti-NMDAR encephalitis has been associated with multiple antigenic triggers (i.e., ovarian teratomas, prodromal viral infections) but whether geographic, climatic, and environmental factors might influence disease risk has not been explored yet. We performed a systematic review and a meta-analysis of all published papers reporting the incidence of anti-NMDAR encephalitis in a definite country or region. We performed several multivariate spatial autocorrelation analyses to analyze the spatial variations in the incidence of anti-NMDA encephalitis depending on its geographical localization and temperature. Finally, we performed seasonal analyses in two original datasets from France and Greece and assessed the impact of temperature using an exposure-lag-response model in the French dataset. The reported incidence of anti-NMDAR encephalitis varied considerably among studies and countries, being higher in Oceania and South America (0.2 and 0.16 per 100,000 persons-year, respectively) compared to Europe and North America (0.06 per 100,000 persons-year) (p < 0.01). Different regression models confirmed a strong negative correlation with latitude (Pearson's R = -0.88, p < 0.00001), with higher incidence in southern hemisphere countries far from the equator. Seasonal analyses showed a peak of cases during warm months. Exposure-lag-response models confirmed a positive correlation between extreme hot temperatures and the incidence of anti-NMDAR encephalitis in France (p = 0.03). Temperature analyses showed a significant association with higher mean temperatures and positive correlation with higher ultraviolet exposure worldwide. This study provides the first evidence that geographic and climatic factors including latitude, mean annual temperature, and ultraviolet exposure, might modify disease risk.

Cortical metabolic characteristics of anti-leucine-rich glioma-inactivated 1 antibody encephalitis based on 18F-FDG PET

Purpose

A general glucose metabolism pattern is observed in patients with anti-leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis; however, it is unclear whether further subregional metabolic differences exist. Therefore, the present study aimed to conduct an in-depth exploration of the features of glucose metabolism within specific brain areas using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET).

Materials and methods

This retrospective study enrolled thirteen patients confirmed with LGI1 antibody encephalitis who were admitted to Beijing Tiantan Hospital from June 2021 to September 2022. All patients underwent 18F-FDG PET before initiating clinical treatment. Changes in glucose metabolism in specific brain areas were analyzed using Cortex ID software. The laterality of 18F-FDG uptake was assessed, and differences in specific brain areas were compared using paired t-tests.

Results

Significant metabolic changes in at least one brain region in 11 out of 13 patients (84.6%) were revealed by semi-quantitative analysis (z-score &gt; 2). A bilateral decrease in the 18F-FDG metabolic pattern was revealed in almost all brain regions of interest; in contrast, a hypermetabolic pattern was observed in the medial temporal region, with mean z-scores of 1.75 ± 3.27 and 2.36 ± 5.90 on the left and right sides, respectively (p = 0.497). In the prefrontal and temporal lobes, 18F-FDG metabolism was significantly lower in the lateral region than in the medial region on both sides. For the cingulate cortex, significant hypometabolism was also observed in the posterior part compared to the anterior counterpart on both the left (z-score: −1.20 ± 1.93 vs. −0.42 ± 1.18, respectively; p = 0.047) and right (z-score: −1.56 ± 1.96 vs. −0.33 ± 1.63, respectively; p = 0.001) sides. However, a significant difference in regional metabolism was observed only on the left side (p = 0.041).

Conclusion

An asymmetric 18F-FDG metabolic pattern exists in patients with anti-LGI1 encephalitis. Meanwhile, varied regional metabolic differences were revealed bilaterally in specific cerebral areas, which could be associated with the clinical manifestations.

Hypometabolism of the left middle/medial frontal lobe on FDG-PET in anti-NMDA receptor encephalitis: Comparison with MRI and EEG findings

OBJECTIVES

To investigate changes in brain-glucose metabolism in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, and compare results with MRI and electroencephalography (EEG) findings at different disease stages.

METHODS

The clinical data of 18 patients (median age, 35 years; 11 men) were retrospectively collected. Patients were divided into groups based on the time of symptom onset to examination, (≤1 month, >1 but ≤3 months, >3 months). Two-sample t-test results were compared with age and sex-paired healthy controls using statistical parametric mapping and verified using a NeuroQ software normal database with a discriminating z-score of 2.

RESULTS

Abnormal patterns on FDG-PET differed over time (T = 3.21-8.74, Z = 2.68-4.23, p < 0.005). Regional analysis showed hypometabolic left middle or medial frontal cortex in 4/5, 5/7, and 5/6 patients, respectively. Time-subgroup analysis revealed hypermetabolic supertemporal cortex in 4/5, 5/7, and 2/6, patients, respectively. MRI and EEG abnormalities in any region and stage occurred in 10/18 and 10/16 patients, respectively. MRI and EEG time-subgroup analysis showed abnormalities in 5/9, 4/5, and 1/4, and 1/3, 6/7, and 3/6 patients, respectively. Abnormal temporal lobes were detected most frequently in MRI analyses and occurred in 3/10 patients.

CONCLUSIONS

Decreased left middle/medial frontal metabolism could be common to all stages. Metabolism in other regions, MRI, and EEG results were associated with the progression of anti-NMDAR encephalitis. The sensitivity rate of FDG-PET was superior to that of MRI and EEG.

Brain Metabolic Alterations in Seropositive Autoimmune Encephalitis: An 18F-FDG PET Study

INTRODUCTION

Autoimmune encephalitis (AE) diagnosis and follow-up remain challenging. Brain ¹⁸F-fluoro-deoxy-glucose positron emission tomography (FDG PET) has shown promising results in AE. Our aim was to investigate FDG PET alterations in AE, according to antibody subtype.

METHODS

We retrospectively included patients with available FDG PET and seropositive AE diagnosed in our center between 2015 and 2020. Brain PET Z-score maps (relative to age matched controls) were analyzed, considering metabolic changes significant if |Z-score| ≥ 2.

RESULTS

Forty-six patients were included (49.4 yrs [18; 81]): 13 with GAD autoantibodies, 11 with anti-LGI1, 9 with NMDAR, 5 with CASPR2, and 8 with other antibodies. Brain PET was abnormal in 98% of patients versus 53% for MRI. The most frequent abnormalities were medial temporal lobe (MTL) and/or striatum hypermetabolism (52% and 43% respectively), cortical hypometabolism (78%), and cerebellum abnormalities (70%). LGI1 AE tended to have more frequent MTL hypermetabolism. NMDAR AE was prone to widespread cortical hypometabolism. Fewer abnormalities were observed in GAD AE. Striatum hypermetabolism was more frequent in patients treated for less than 1 month (p = 0.014), suggesting a relation to disease activity.

CONCLUSION

FDG PET could serve as an imaging biomarker for early diagnosis and follow-up in AE.

Positron emission tomography in autoimmune encephalitis: Clinical implications and future directions

¹⁸ F-fluoro-deoxyglucose position emission tomography (¹⁸ F-FDG-PET) has been proven as a sensitive and reliable tool for diagnosis of autoimmune encephalitis (AE). More attention was paid to this kind of imaging because of the shortage of MRI, EEG, and CSF findings. FDG-PET has been assessed in a few small studies and case reports showing apparent abnormalities in cases where MRI does not. Here, we summarized the patterns (specific or not) in AE with different antibodies detected and the clinical outlook for the wide application of FDG-PET considering some limitations. Specific patterns based on antibody subtypes and clinical symptoms were critical for identifying suspicious AE, the most common of which was the anteroposterior gradient in anti- N -methyl- d -aspartate receptor (NMDAR) encephalitis and the medial temporal lobe hypermetabolism in limbic encephalitis. And the dynamic changes of metabolic presentations in different phases provided us the potential to inspect the evolution of AE and predict the functional outcomes. Except for the visual assessment, quantitative analysis was recently reported in some voxel-based studies of regions of interest, which suggested some clues of the future evaluation of metabolic abnormalities. Large prospective studies need to be conducted controlling the time from symptom onset to examination with the same standard of FDG-PET scanning.

The Detection of Invisible Abnormal Metabolism in the FDG-PET Images of Patients With Anti-LGI1 Encephalitis by Machine Learning

Objective

This study aims to detect the invisible metabolic abnormality in PET images of patients with anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis using a multivariate cross-classification method.

Methods

Participants were divided into two groups, namely, the training cohort and the testing cohort. The training cohort included 17 healthy participants and 17 patients with anti-LGI1 encephalitis whose metabolic abnormality was able to be visibly detected in both the medial temporal lobe and the basal ganglia in their PET images [completely detectable (CD) patients]. The testing cohort included another 16 healthy participants and 16 patients with anti-LGI1 encephalitis whose metabolic abnormality was not able to be visibly detected in the medial temporal lobe and the basal ganglia in their PET images [non-completely detectable (non-CD) patients]. Independent component analysis (ICA) was used to extract features and reduce dimensions. A logistic regression model was constructed to identify the non-CD patients.

Results

For the testing cohort, the accuracy of classification was 90.63% with 13 out of 16 non-CD patients identified and all healthy participants distinguished from non-CD patients. The patterns of PET signal changes resulting from metabolic abnormalities related to anti-LGI1 encephalitis were similar for CD patients and non-CD patients.

Conclusion

This study demonstrated that multivariate cross-classification combined with ICA could improve, to some degree, the detection of invisible abnormal metabolism in the PET images of patients with anti-LGI1 encephalitis. More importantly, the invisible metabolic abnormality in the PET images of non-CD patients showed patterns that were similar to those seen in CD patients.

[18F]FDG brain PET and clinical symptoms in different autoantibodies of autoimmune encephalitis: a systematic review

INTRODUCTION

Autoimmune encephalitis (AE) is caused by the antibodies that target receptors and intracellular or surface proteins. To achieve the appropriate therapeutic results, early and proper diagnosis is still the most important issue. In this review, we provide an overview of FDG-PET imaging findings in AE patients and possible relation to different subtypes and clinical features.

METHODS

PubMed, Web of Science, and Scopus were searched in August 2021 using a predefined search strategy.

RESULTS

After two-step reviewing, 22 studies with a total of 332 participants were entered into our qualitative synthesis. In anti-NMDAR encephalitis, decreased activity in the occipital lobe was present, in addition, to an increase in frontal, parietal, and specifically medial temporal activity. Anti-VGKC patients showed altered metabolism in cortical and subcortical regions such as striata and cerebellum. Abnormal metabolism in patients with anti-LGI1 has been reported in diverse areas of the brain including medial temporal, hippocampus, cerebellum, and basal ganglia all of which had hypermetabolism. Hypometabolism in parietal, frontal, occipital lobes, temporal, frontal, and hippocampus was observed in AE patients with anti-GAD antibodies.

CONCLUSION

Our results indicate huge diversity in metabolic patterns among different AE subtypes and it is hard to draw a firm conclusion. Moreover, the timing of imaging, seizures, and acute treatments can alter the PET patterns strongly. Further prospective investigations with specific inclusion and exclusion criteria should be carried out to identify the metabolic defect in different AE subtypes.

Pediatric GAD-65 Autoimmune Encephalitis: Assessing Clinical Characteristics and Response to Therapy With a Novel Assessment Scale

BACKGROUND

Glutamic acid decarboxylase (GAD) encephalitis is a neuroinflammatory disease characterized by a broad range of symptoms including cognitive deficits, behavioral changes, and seizures. Children with this disorder have heterogeneous presentations, and little is known about symptom progression over time and response to immunotherapy.

METHODS

This study reports 10 pediatric GAD encephalitis cases and symptoms found at presentation and follow-up. In addition, symptom severity was reported utilizing a novel scale evaluating functional outcomes across the domains affected by autoimmune encephalitis including cognition, language, seizures, psychiatric symptoms, sleep, and movement. Retrospective chart review was conducted for 10 patients aged <18 years, diagnosed with GAD encephalitis, and followed for one year or more. Chart review included clinical, imaging, and laboratory findings at time of diagnosis and at six- and 12-month follow-ups.

RESULTS

At presentation, cognitive deficits were found in all patients, seizures in six of 10, and language decline in seven of 10. Psychiatric symptoms were prominent for all but one patient with three of nine patients presenting with psychosis. Fatigue, sleep disruption, and movement disorders were less prominent symptoms, occurring in approximately half of the cohort. Cognition and fatigue improved significantly over time when compared with symptom severity, whereas seizures, psychiatric symptoms, and sleep did not. Language and sleep showed improvement only in early stages. Analysis of seizure frequency and type noted variability mirroring trends noted in adult studies of GAD encephalitis.

CONCLUSIONS

This study demonstrated the variability of symptom profiles of pediatric GAD encephalitis and benefits of symptom severity scales. Symptom profiles and progression vary in this population.

Cortical and Subcortical Dysmetabolism Are Dynamic Markers of Clinical Disability and Course in Anti-LGI1 Encephalitis

Background and Objectives

This [¹⁸F]fluorodeoxyglucose (FDG) PET study evaluates the accuracy of semiquantitative measurement of putaminal hypermetabolism in identifying anti–leucine-rich, glioma–inactivated-1 (LGI1) protein autoimmune encephalitis (AE). In addition, the extent of brain dysmetabolism, their association with clinical outcomes, and longitudinal metabolic changes after immunotherapy in LGI1-AE are examined.

Methods

FDG-PET scans from 49 age-matched and sex-matched subjects (13 in LGI1-AE group, 15 in non–LGI1-AE group, 11 with Alzheimer disease [AD], and 10 negative controls [NCs]) and follow-up scans from 8 patients with LGI1 AE on a median 6 months after immunotherapy were analyzed. Putaminal standardized uptake value ratios (SUVRs) normalized to global brain (P-SUVRg), thalamus (P/Th), and midbrain (P/Mi) were evaluated for diagnostic accuracy. SUVRg was applied for all other analyses.

Results

P-SUVRg, P/Th, and P/Mi were higher in LGI1-AE group than in non–LGI1-AE group, AD group, and NCs (all p < 0.05). P/Mi and P-SUVRg differentiated LGI1-AE group robustly from other groups (areas under the curve 0.84–0.99). Mediotemporal lobe (MTL) SUVRg was increased in both LGI1-AE and non–LGI1-AE groups when compared with NCs (both p < 0.05). SUVRg was decreased in several frontoparietal regions and increased in pallidum, caudate, pons, olfactory, and inferior occipital gyrus in LGI1-AE group when compared with that in NCs (all p < 0.05). In LGI1-AE group, both MTL and putaminal hypermetabolism were reduced after immunotherapy. Normalization of regional cortical dysmetabolism associated with clinical improvement at the 6- and 20-month follow-up.

Discussion

Semiquantitative measurement of putaminal hypermetabolism with FDG-PET may be used to distinguish LGI1-AE from other pathologies. Metabolic abnormalities in LGI1-AE extend beyond putamen and MTL into other subcortical and cortical regions. FDG-PET may be used in evaluating disease evolution in LGI1-AE.

Classification of Evidence

This study provides Class II evidence that semiquantitative measures of putaminal metabolism on PET can differentiate patients with LGI1-AE from patients without LGI1-AE, patients with AD, or NCs.

Usefulness of brain FDG PET/CT imaging in pediatric patients with suspected autoimmune encephalitis from a prospective study

Purpose

Early diagnosis and treatment are of paramount importance for pediatric patients with autoimmune encephalitis (AE). The aim is to evaluate the usefulness of FDG PET/CT in pediatric patients with suspected AE from a prospective study.

Methods

The prospective study was conducted over a period of 23.5 months from May 14, 2019, to April 30, 2021. All patients (< 18-year-old) were hospitalized at the department of pediatric neurology and met the criteria of clinical suspected AE. The children underwent the tests of blood samplings, CSF, EEG, MRI, and ¹⁸F-FDG PET/CT. The criteria for FDG PET/CT diagnosis of AE were large lobar hypometabolism with or without focal hypermetabolism found on PET/CT. The clinical final diagnosis of AE includes seropositive and seronegative AE based on the diagnostic criteria.

Results

One hundred four pediatric inpatients (57 boys, 47 girls) were included, of which 58 children were diagnosed with AE (seropositive, 16; seronegative, 42), 45 children were diagnosed with non-AE, and one boy remained indeterminate diagnosis. Large lobar hypometabolism was found in 61 children, of which 54 (88.5%) children were finally diagnosed with AE. The sensitivity, specificity, and accuracy of FDG PET/CT for diagnosis of AE were 93.1%, 84.4%, and 89.3%, respectively, with a positive predictive value of 88.5% and a negative predictive value of 90.5%. The most common involved with hypometabolism was the parietal lobe, followed by occipital and frontal lobes, finally the temporal lobe on PET/CT in children with AE.

Conclusion

Brain FDG PET/CT imaging has high specificity, sensitivity, and accuracy for diagnosis of AE in clinical suspected AE children.

Trial registration.

Clinical Trials.gov. NCT02969213. Registered 17 October 2016.

Brain 18F-FDG PET for the diagnosis of autoimmune encephalitis: a systematic review and a meta-analysis

OBJECTIVE

To consolidate current understanding of detection sensitivity of brain ¹⁸F-FDG PET scans in the diagnosis of autoimmune encephalitis and to define specific metabolic imaging patterns for the most frequently occurring autoantibodies.

METHODS

A systematic and exhaustive search of data available in the literature was performed by querying the PubMed/MEDLINE and Cochrane databases for the search terms: ((PET) OR (positron emission tomography)) AND ((FDG) OR (fluorodeoxyglucose)) AND ((encephalitis) OR (brain inflammation)). Studies had to satisfy the following criteria: (i) include at least ten pediatric or adult patients suspected or diagnosed with autoimmune encephalitis according to the current recommendations, (ii) specifically present ¹⁸F-FDG PET and/or morphologic imaging findings. The diagnostic ¹⁸F-FDG PET detection sensitivity in autoimmune encephalitis was determined for all cases reported in this systematic review, according to a meta-analysis following the PRISMA method, and selected publication quality was assessed with the QUADAS-2 tool.

RESULTS

The search strategy identified 626 articles including references from publications. The detection sensitivity of ¹⁸F-FDG PET was 87% (80-92%) based on 21 publications and 444 patients included in the meta-analysis. We also report specific brain ¹⁸F-FDG PET imaging patterns for the main encephalitis autoantibody subtypes.

CONCLUSION AND RELEVANCE

Brain ¹⁸F-FDG PET has a high detection sensitivity and should be included in future diagnostic autoimmune encephalitis recommendations. Specific metabolic ¹⁸F-FDG PET patterns corresponding to the main autoimmune encephalitis autoantibody subtypes further enhance the value of this diagnostic.

Subcortical Hypermetabolism Associated With Cortical Hypometabolism Is a Common Metabolic Pattern in Patients With Anti-Leucine-Rich Glioma-Inactivated 1 Antibody Encephalitis

Purpose

Brain 18F-fluorodeoxyglucose positron emission tomography (FDG PET) is a sensitive technique for assisting in the diagnosis of patients with anti-leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis. However, the common pattern of this disorder assessed by FDG PET remains unknown. The present study aimed to explore the glucose metabolic patterns of this disorder based on PET voxel analysis.

Methods

This retrospective study enrolled 25 patients with anti-LGI1 encephalitis, who were admitted in Beijing Tiantan Hospital between September 2014 and July 2019. The glucose metabolic pattern was compared between the included patients and 44 age- and gender-matched healthy controls using Statistical Parametric Mapping. Then, the correlation between the metabolic pattern and scaled activities of daily living (ADLs) of the patients was assessed.

Results

The median time from symptom onset to PET scans was 9 w (range:2-53w). The groupwise analysis revealed that patients with anti-LGI1 encephalitis had left hippocampal hypermetabolism and hypometabolism in almost all neocortical regions. The individual-level results showed most patients presented a decreased metabolism in neocortical regions, as well as an increase in metabolism in the hippocampus and basal ganglia. Furthermore, the metabolic gradient between hippocampus and neocortical regions was positively associated with the ADLs (frontal lobe, r=0.529, P=0.008; parietal lobe, r=0.474, P=0.019; occipital lobe, r=0.413, P=0.045; temporal lobe, r=0.490, P=0.015), respectively. In addition, the patients with facio-brachial dystonic seizures (FBDS) presented bilateral putamen hypermetabolism, when compared to patients without FBDS and healthy controls.

Conclusion

Subcortical hypermetabolism associated with cortical hypometabolism presented with a common metabolic pattern in patients with anti-LGI1 encephalitis in the present study. The resolution of the metabolic gradient of the hippocampal hypermetabolism and neocortical hypometabolism may bring about improved clinical neurologic disability.

[18F]Flortaucipir PET Across Various MAPT Mutations in Presymptomatic and Symptomatic Carriers

OBJECTIVE

To assess the [18F]flortaucipir binding distribution across MAPT mutations in presymptomatic and symptomatic carriers.

METHODS

We compared regional [18F]flortaucipir binding potential (BPND) derived from a 130-minute dynamic [18F]flortaucipir PET scan in 9 (pre)symptomatic MAPT mutation carriers (4 with P301L [1 symptomatic], 2 with R406W [1 symptomatic], 1 presymptomatic L315R, 1 presymptomatic S320F, and 1 symptomatic G272V carrier) with 30 cognitively normal controls and 52 patients with Alzheimer disease.

RESULTS

[18F]Flortaucipir BPND images showed overall highest binding in the symptomatic carriers. This was most pronounced in the symptomatic R406W carrier in whom tau binding exceeded the normal control range in the anterior cingulate cortex, insula, amygdala, temporal, parietal, and frontal lobe. Elevated medial temporal lobe BPND was observed in a presymptomatic R406W carrier. The single symptomatic carrier and 1 of the 3 presymptomatic P301L carriers showed elevated [18F]flortaucipir BPND in the insula, parietal, and frontal lobe compared to controls. The symptomatic G272V carrier exhibited a widespread elevated cortical BPND, with at neuropathologic examination a combination of 3R pathology and encephalitis. The L315R presymptomatic mutation carrier showed higher frontal BPND compared to controls. The BPND values of the S320F presymptomatic mutation carrier fell within the range of controls.

CONCLUSION

Presymptomatic MAPT mutation carriers already showed subtle elevated tau binding, whereas symptomatic MAPT mutation carriers showed a more marked increase in [18F]flortaucipir BPND. Tau deposition was most pronounced in R406W MAPT (pre)symptomatic mutation carriers, which is associated with both 3R and 4R tau accumulation. Thus, [18F]flortaucipir may serve as an early biomarker for MAPT mutation carriers in mutations that cause 3R/4R tauopathies.

Hypermetabolism on Pediatric PET Scans of Brain Glucose Metabolism: What Does It Signify?

When one is interpreting clinical 18F-FDG PET scans of the brain (excluding tumors) in children, the typical abnormality seen is hypometabolism of various brain regions. Focal areas of hypermetabolism are noted occasionally, and the usual interpretation is that the hypermetabolic region represents a seizure focus. In this review, I discuss and illustrate the multiple causes of hypermetabolism on 18F-FDG PET studies that should not be interpreted as seizure activity, as such an interpretation could potentially be incorrect. Various conditions in which focal hypermetabolism can be encountered on 18F-FDG PET studies include interictal hypermetabolism, Sturge-Weber syndrome, changes associated with brain plasticity after injury, Rett syndrome, hypoxic-ischemic brain injury, various inborn errors of metabolism, and autoimmune encephalitis. The radiologist or nuclear medicine physician interpreting clinical 18F-FDG PET studies should be aware of these circumstances to accurately assess the findings.

Decrease in the cortex/striatum metabolic ratio on [18F]-FDG PET: a biomarker of autoimmune encephalitis

PURPOSE

The aim of this [¹⁸F]-FDG PET study was to determine the diagnostic value of the cortex/striatum metabolic ratio in a large cohort of patients suffering from autoimmune encephalitis (AE) and to search for correlations with the course of the disease.

METHODS

We retrospectively collected clinical and paraclinical data of patients with AE, including brain ¹⁸F-FDG PET/CT. Whole-brain statistical analysis was performed using SPM8 software after activity parametrization to the striatum in comparison to healthy subjects. The discriminative performance of this metabolic ratio was evaluated in patients with AE using receiver operating characteristic curves against 44 healthy subjects and a control group of 688 patients with MCI. Relationship between cortex/striatum metabolic ratios and clinical/paraclinical data was assessed using univariate and multivariate analysis in patients with AE.

RESULTS

Fifty-six patients with AE were included. In comparison to healthy subjects, voxel-based statistical analysis identified one large cluster (p-cluster < 0.05, FWE corrected) of widespread decreased cortex/striatum ratio in patients with AE. The mean metabolic ratio was significantly lower for AE patients (1.16 ± 0.13) than that for healthy subjects (1.39 ± 0.08; p < 0.001) and than that for MCI patients (1.32 ± 0.11; p < 0.001). A ratio threshold of 1.23 allowed to detect AE patients with a sensitivity of 71% and a specificity of 82% against MCI patients, and 98% against healthy subjects. A lower cortex/striatum metabolic ratio had a trend towards shorter delay before ¹⁸F-FDG PET/CT (p = 0.07) in multivariate analysis.

CONCLUSION

The decrease in the cortex/striatal metabolic ratio has a good early diagnostic performance for the differentiation of AE patients from controls.

Recognition of seizure semiology and semiquantitative FDG-PET analysis of anti-LGI1 encephalitis

Aims

Anti‐leucine‐rich glioma‐inactivated 1 (LGI1) autoimmune encephalitis (AE) is characterized by complex manifestations of seizures. Here, we report a new seizure semiology, attempt to classify the disease by semiology type, and explore the metabolic pattern of each group.

Methods

Anti‐LGI1 AE patients were retrospectively screened between May 2014 and September 2019 in our tertiary epilepsy center. All enrolled patients had seizures during long‐range video electroencephalogram (EEG) recordings, and all patients (except one) underwent [¹⁸F] fluoro‐2‐deoxyglucose (FDG) positron emission tomography (PET) scans. Voxel‐based metabolic analysis and z‐distribution analysis were carried out to determine the metabolic pattern.

Results

Thirty‐three patients were enrolled. According to the patients’ seizure semiology, we divided the patients into four groups: focal impaired awareness seizures (FIAS, n = 17), faciobrachial dystonic seizures (FBDS)‐only (n = 6), FBDS‐plus (n = 8), and focal aware motor seizures (FAMS) (n = 2). No significant differences were found in the clinical manifestations or accessory tests except for the onset age (FIAS < FBDS‐plus) and seizure semiology. This was the first study to extensively describe the clinical manifestations and EEG of FAMS in anti‐LGI1 AE patients. In addition, we found that the patients with different semiologies all showed a wide range of abnormal metabolism, which is not limited to the temporal regions and basal ganglia, and extends far beyond our previous interpretation of FDG‐PET data.

Conclusion

Our results showed that FAMS can serve as a rare indicative seizure semiology of anti‐LGI1 AE and that individuals with this disease exhibited widespread functional network alterations.

F-18 Fluorodeoxyglucose Positron Emission Tomography Metabolic Phenotype in Myelin Oligodendrocyte Glycoprotein Antibody-Positive Autoimmune Epilepsy

We describe the metabolic phenotype on F-18 fluorodeoxyglucose positron emission tomography (PET) in a 13-year-old female with myelin oligodendrocyte glycoprotein (MOG) antibody–positive encephalitis. Unilateral hemispheric hypometabolism on PET may be the metabolic phenotype of autoimmune epilepsy associated with MOG antibody.

Distinct cerebral 18F-FDG PET metabolic patterns in anti-N-methyl-D-aspartate receptor encephalitis patients with different trigger factors

Aim:

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a subgroup of treatable autoimmune encephalitis, characterized by rapid development of psychosis, cognitive impairments and seizures. Etiologically, anti-NMDAR encephalitis could be divided into three subgroups, which are paraneoplastic (especially associated with ovarian teratoma), viral encephalitis-related and cryptogenic. Each type is different in clinical course, treatment strategies and prognosis. In this study, we aim to investigate whether anti-NMDAR encephalitis patients with different trigger factors exhibit distinct cerebral metabolic patterns detected by ¹⁸F-fluorodeoxyglucose positron emission tomography imaging.

Methods:

24 patients with anti-NMDAR encephalitis in acute phase from Huashan Hospital, Fudan University (Shanghai, China) were recruited in this study. Each patient was classified into one of etiological subgroups. Positron emission tomography images of individual patients were analyzed with both routine visual reading and computer-supported reading by comparison with those of the same 10 healthy controls using a voxel-wise statistical parametric mapping analysis.

Results:

Patients in both the cryptogenic (13 patients) and paraneoplastic (five patients) subgroups showed hypermetabolism in the frontal-temporal lobes and basal ganglia, covarying with hypometabolism in the occipital regions. Notably, the abnormal metabolism was usually asymmetric in the cryptogenic subgroup, but relatively symmetric in the paraneoplastic subgroup. Moreover, the other six patients secondary to viral encephalitis presented with significant hypometabolism in the bilateral occipital regions, as well as in the unilateral temporal lobes and part of basal ganglia (also is virus infection side), but hypermetabolism in the contralateral temporal areas.

Conclusion:

This study revealed that patients with anti-NMDAR encephalitis triggered by different factors presented distinct cerebral metabolic patterns. Awareness of these patterns may help to better understand the varying occurrence and development of anti-NMDAR encephalitis in each subgroup, and could offer valuable information to the early diagnosis, treatment and prognosis of this disorder.

Trial registration number

ChiCTR2000029115 (Chinese clinical trial registry site, http://www.chictr.org)

Clinical features of anti-leucine-rich glioma-inactivated 1 encephalitis in northeast China

AIM

To examine the clinical characteristics, laboratory tests, imaging and electroencephalography presentation, treatment, and prognosis of anti-leucine-rich glioma-inactivated 1 (anti-LGI1) encephalitis and improve the awareness of this disease.

METHOD

We performed a retrospective analysis of the clinical data of 41 patients who were diagnosed with anti-LGI1 encephalitis. Their clinical characteristics, laboratory tests, and imaging and electroencephalography data were collected, and the treatment results and prognosis were evaluated. The modified Rankin Scale (mRS) was used to evaluate neurological function.

RESULTS

A total of 41 patients were included in the study, the average follow-up time is 33.0 months.The initial symptoms included cognitive impairment (n = 16, 39.0%),faciobrachial dystonic seizures (FBDS) (n = 12, 29.3%), grand mal seizures (n = 5, 12.2%) hallucinations (n = 4, 9.8%), loss of consciousness (n = 2, 4.9%), nausea and vomiting (n = 1, 2.4%),and head discharge-like sensation and radiate one limb (n = 1, 2.4%). There were 20 and 21 patients in the good (mRS ≤ 2) and poor (mRS > 2) prognosis groups, respectively. In the good prognosis group, the initial symptoms included faciobrachial dystonic seizures (FBDS) (n = 6, 30.0%), cognitive impairment (n = 6, 30.0%), hallucinations (n = 4, 20.0%), grand mal seizures (n = 3, 15.0%), loss of consciousness (n = 2, 10.0%), and nausea and vomiting (n = 1, 5.0%). There were 10 patients with hyponatremia. Magnetic resonance imaging (MRI) showed limbic system involvement in 12 patients (60.0%).17 patients (85.0%) recovered, 2 (10.0%) showed significant improvement, and 1 (5.0%) died after a mean follow-up period of 36.9 months. In the poor prognosis group, the initial symptoms included FBDS (n = 6, 28.5%), cognitive impairment (n = 10, 47.6%), grand mal seizures (n = 2, 9.5%), and electric shock-like sensation in the left limbs (n = 1, 4.7%). There were 20 patients with hyponatremia. MRI showed limbic system involvement in 11 patients (52.4%). 11 patients (52.4%) recovered, 8 (38.1%) showed significant improvement, and 2 (9.5%) died after a mean follow-up period of 29.0 months.

CONCLUSIONS

The clinical characteristics of anti-LGI1 encephalitis include hyponatremia, FBDS, epileptic seizures, hallucinations, cognitive impairment, and loss of consciousness, while the rarely seen characteristics are nausea, vomiting, and other autonomic dysfunctions and electric shock-like sensation. The appearance of hallucinations often indicates a good prognosis.Hyponatremia and elevated cerebrospinal fluid protein levels can be used as indicators that affect the prognosis of patients.Limbic system involvement has nothing to do with prognosis.Attention should be paid to early diagnosis and timely first-line immunotherapy.

Autoimmune limbic encephalitis related to SARS-CoV-2 infection: Case-report and review of the literature

Background

SARS-CoV-2 infection is associated with a wide spectrum of neurological complications, including encephalitis. Most cases showed features consistent with a central nervous system (CNS) cytokine-mediated damage. However, few cases arguing for an autoimmune mechanism have been described, mainly as single reports or sparse in large case series involving other CNS manifestations. In this paper, we described a case of definite autoimmune limbic encephalitis (LE) COVID-19 related and reviewed the existing literature on other reported cases.

Case report

Two weeks after the onset of COVID-19 infection, a 74-year-old woman presented with subacute confusion and focal motor seizures with impaired awareness, starting from left temporal region. Cerebrospinal fluid analysis revealed hyperproteinorrachia. Brain MRI showed bilateral T2/FLAIR hyperintensities in both hippocampi and total body PET/TC scan revealed hypermetabolism in basal ganglia bilaterally. A diagnosis of autoimmune LE was made. Thus, high dose corticosteroids and antiseizure medications were started, with a marked improvement of neurological conditions.

Literature review

We systematically reviewed the literature to identify all well-documented cases of definite autoimmune LE (according to Graus criteria) in patients with COVID-19 infection, identifying other five cases exhibiting a good response to immunomodulating therapy.

Conclusion

A very limited number of autoimmune LE have been described until now. It is important to monitor neurological symptoms in COVID-19 patients and to consider the possibility of an autoimmune LE, in particular when altered mental status and seizures appear late in the disease course. This allows to promptly start the appropriate treatments and avoid unnecessary delays.

•

A limited number of autoimmune LE covid-19 related have been described until now.

•

A specific focus on autoimmune limbic encephalitis covid-19-related is lacking.

•

It ​is important to consider the possibility of covid-19 related limbic encephalitis to promptly start appropriate treatments.

Metabolic scoring in autoimmune epilepsy-Should APE scores be modified?

OBJECTIVE

We evaluate the potential utility of F-18 FDG-PET in addition to MRI in the diagnostic work-up of patients with autoimmune epilepsy (AE) and propose the inclusion of functional imaging in the antibody prevalence in epilepsy (APE) scoring system.

METHODS

This was a retrospective analysis in 60 patients, diagnosed and treated for AE, of whom 40 were antibody negative (presumed AE) and 20 were antibody positive (definitive AE). All patients had undergone a dedicated brain and whole body FDG-PET in the department of Nuclear Medicine.

RESULTS

In the antibody negative group, MRI supported a diagnosis of AE in 23 patients. Both MRI and PET were indicative in 12 cases, and standalone PET was positive in 8. While MRI alone was diagnostic in 57% (23/40), the combined yield of both modalities was 77% (31/40). When PET scores were added to assign the APE score in MRI negative cases, average APE score was 5.4. In the antibody positive group, MRI supported the diagnosis of AE in 7 patients. Both MRI and PET were positive in 4 patients and standalone PET was positive in 5 patients. While MRI alone was diagnostic in 35% (7/20), the combined yield of both modalities was 60% (12/20). When PET scores were added to assign the APE score in MRI negative cases, average APE score was 6.1.

CONCLUSION

The inclusion of metabolic information from PET distinctly improved (the sensitivity of) APE scores to predict autoimmune origin even in antibody negative cases. A larger prospective study of similar type could justify adoption of FDG-PET into the standard diagnostic procedure.

Structural network topology in limbic encephalitis is associated with amygdala enlargement, memory performance and serostatus

Limbic encephalitis (LE) forms a spectrum of autoimmune diseases involving temporal lobe epilepsy and memory impairment. Imaging features of LE are known to depend on the associated antibody and to occur on the brain network level. However, first studies investigating brain networks in LE have either focused on one distinct antibody subgroup or on distinct anatomical regions. In this study, brain graphs of 17 LE patients with autoantibodies against glutamic acid decarboxylase 65 (GAD-LE), four LE patients with autoantibodies against leucine-rich glioma-inactivated 1, five LE patients with autoantibodies against contactin-associated protein-like 2, 26 age- and gender-matched healthy control subjects, and 20 epilepsy control patients with hippocampal sclerosis were constructed based on T1-weighted structural magnetic resonance imaging scans and diffusion tensor imaging. GAD-LE showed significantly altered global network topology in terms of integration and segregation as compared to healthy controls and patients with hippocampal sclerosis (P < .01, analysis of variance with Tukey-Kramer post hoc tests). Linear regression linked global network measures with amygdala volume and verbal memory performance (P < .05). Alterations of local network topology show serotype dependence in hippocampus, amygdala, insula, and various cortical regions. Our findings reveal serotype-dependent patterns of structural connectivity and prove the relevance of in silico network measures on clinical grounds.

Psychiatric Manifestation of Anti-LGI1 Encephalitis

Background: Anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis is typically characterized by limbic encephalitis, faciobrachial dystonic seizures and hyponatremia. The frequency with which milder forms of anti-LGI1 encephalitis mimic isolated psychiatric syndromes, such as psychoses, or may lead to dementia if untreated, is largely unknown. Case presentation: Here, the authors present a 50-year-old patient who had suffered from neurocognitive deficits and predominant delusions for over one and a half years. He reported a pronounced feeling of thirst, although he was drinking 10–20 liters of water each day, and he was absolutely convinced that he would die of thirst. Due to insomnia in the last five years, the patient took Z-drugs; later, he also abused alcohol. Two years prior to admission, he developed a status epilepticus which had been interpreted as a withdrawal seizure. In his serum, anti-LGI1 antibodies were repeatedly detected by different independent laboratories. Cerebrospinal fluid analyses revealed slightly increased white blood cell counts and evidence for blood–brain-barrier dysfunction. Magnetic resonance imaging showed hyperintensities mesio-temporally and in the right amygdala. In addition, there was a slight grey–white matter blurring. A cerebral [¹⁸F] fluorodeoxyglucose positron emission tomography (FDG-PET) examination of his brain showed moderate hypometabolism of the bilateral rostral mesial to medial frontal cortices. Treatment attempts with various psychotropic drugs remained unsuccessful in terms of symptom relief. After the diagnosis of probable chronified anti-LGI1 encephalitis was made, two glucocorticoid pulse treatments were performed, which led to a slight improvement of mood and neurocognitive deficits. Further therapy was not desired by the patient and his legally authorized parents. Conclusion: This case study describes a patient with anti-LGI1 encephalitis in the chronified stage and a predominant long-lasting psychiatric course with atypical symptoms of psychosis and typical neurocognitive deficits. The patient’s poor response to anti-inflammatory drugs was probably due to the delayed start of treatment. This delay in diagnosis and treatment may also have led to the FDG-PET findings, which were compatible with frontotemporal dementia (“state of damage”). In similar future cases, newly occurring epileptic seizures associated with psychiatric symptoms should trigger investigations for possible autoimmune encephalitis, even in patients with addiction or other pre-existing psychiatric conditions. This should in turn result in rapid organic clarification and—in positive cases—to anti-inflammatory treatment. Early treatment of anti-LGI1 encephalitis during the “inflammatory activity state” is crucial for overall prognosis and may avoid the development of dementia in some cases. Based on this case, the authors advocate the concept—long established in many chronic inflammatory diseases in rheumatology—of distinguishing between an “acute inflammatory state” and a “state of organ damage” in autoimmune psychosis resembling neurodegenerative mechanisms.

Clinical features and immunotherapy outcomes of anti-glutamic acid decarboxylase 65 antibody-associated neurological disorders

We described the clinical and neuroimaging characteristics of seven Chinese patients with anti-GAD65 antibody-associated neurological disorders of whom epileptic seizures were the initial and main symptoms. All patients were given immunotherapy and followed up monthly. The outcome demonstrates that immunotherapy is helpful for non-seizure manifestations of anti-GAD65-associated neurological autoimmunity and is less effective in the treatment of seizures, yet partial responses can still occur in the early stage. Taken together we suggest a trial with immunotherapy in all patients in the early stage of the disease, and in patients with non-epilepsy symptoms in the later stage.

Neurological Syndromes Associated with Anti-GAD Antibodies

Glutamic acid decarboxylase (GAD) is an intracellular enzyme whose physiologic function is the decarboxylation of glutamate to gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter within the central nervous system. GAD antibodies (Ab) have been associated with multiple neurological syndromes, including stiff-person syndrome, cerebellar ataxia, and limbic encephalitis, which are all considered to result from reduced GABAergic transmission. The pathogenic role of GAD Ab is still debated, and some evidence suggests that GAD autoimmunity might primarily be cell-mediated. Diagnosis relies on the detection of high titers of GAD Ab in serum and/or in the detection of GAD Ab in the cerebrospinal fluid. Due to the relative rarity of these syndromes, treatment schemes and predictors of response are poorly defined, highlighting the unmet need for multicentric prospective trials in this population. Here, we reviewed the main clinical characteristics of neurological syndromes associated with GAD Ab, focusing on pathophysiologic mechanisms.

The neuropsychological spectrum of anti-LGI1 antibody mediated autoimmune encephalitis

Anti-Leucine Glioma Inactivated 1 (LGI-1) autoimmune encephalitis (AE) is a rare neuroinflammatory brain condition. Individuals afflicted with this condition can present with cognitive and psychological manifestations that can impact the individual's quality of life, day to day functioning, independence, return to work and interpersonal relationships. Our knowledge of the cognitive profiles and disease associated psychopathology is severely lacking. This review provides a comprehensive summary of the currently available literature, conceptualising our current understanding of the neuropsychological manifestations of anti LGI-1 AE and summarises methodological limitations of the current research to inform and improve future investigations. Key Terms: Autoimmune Diseases; Neuroimmunology; Autoimmune Encephalitis, Limbic Encephalitis; Anti-LGI1 Encephalitis, LGI1; Neuropsychology, Cognitive Assessment.

Conventional brain MRI features distinguishing limbic encephalitis from mesial temporal glioma

PURPOSE

Radiological hallmark of autoimmune limbic encephalitis (LE) is a hyperintense signal in MRI T2-weighted images of mesial temporal structures. We aimed to identify conventional magnetic resonance imaging (MRI) features that can help distinguish LE from temporal glioma.

METHODS

Brain MRIs of 25 patients affected by antibody-positive autoimmune LE, 24 patients affected by temporal glioma (tumor group), and 5 negative controls were retrospectively blindly evaluated in random order.

RESULTS

Ten brain MRIs from the LE group were correctly recognized; one additional patient with mesial temporal hyperintensity with anti-AK5 abs LE was wrongly diagnosed as having a tumor. The brain MRIs of the remaining 14 of the 25 patients with LE were judged negative or, in three cases, showed features not typical for LE. In the tumor group, all MRIs showed pathological alterations diagnosed as tumors in 22/24 cases and as LE in two (2/22, 9%). Unilateral lesions were more common in tumors than in neuroradiologically abnormal LE (96% vs. 18%, p < 0.001). T2/FLAIR hyperintensity of the parahippocampal gyrus was associated more with tumor than with LE (71% vs. 18%) (p = 0,009), as T2/FLAIR hyperintensity of extralimbic structures (p = 0.015), edema (p = 0.041), and mass effect (p = 0.015). Maintenance of gray/white matter distinction was strongly associated with LE (91% vs. 17%, p < 0.001).

CONCLUSION

Conventional brain MRI is a fundamental tool in the differential diagnosis between LE and glioma. Bilateral involvement and maintenance of gray/white matter distinction at the cortical/subcortical interface are highly suggestive of LE.

Antibody-LGI 1 autoimmune encephalitis manifesting as rapidly progressive dementia and hyponatremia: a case report and literature review

BACKGROUND

Anti leucine-rich glioma inactivated 1 (LGI1) encephalitis is a rare autoimmune encephalitis (AE), characterized by acute or subacute cognitive impairment, faciobrachial dystonic seizures, psychiatric disturbances and hyponatremia. Antibody-LGI 1 autoimmune encephalitis (anti-LGI1 AE) has increasingly been recognized as a primary autoimmune disorder with favorable prognosis and response to treatment.

CASE PRESENTATION

Herein, we reported a male patient presenting as rapidly progressive dementia and hyponatremia. He had antibodies targeting LGI1 both in the cerebrospinal fluid and serum, which demonstrated the diagnosis of typical anti-LGI1 AE. The scores of Mini-Mental State Examination and Montreal Cognitive Assessment were 19/30 and 15/30, respectively. Cranial magnetic resonance images indicated hyperintensities in bilateral hippocampus. The findings of brain arterial spin labeling and Fluorine-18-fluorodeoxyglucose positron emission tomography showed no abnormal perfusion/metabolism. After the combined treatment of intravenous immunoglobulin and glucocorticoid, the patient's clinical symptoms improved obviously.

CONCLUSIONS

This case raises the awareness that a rapid progressive dementia with predominant memory deficits could be induced by immunoreactions against LGI1. The better recognition will be great importance for the early diagnosis, essential treatment, even a better prognosis.

Management of Autoimmune Encephalitis: An Observational Monocentric Study of 38 Patients

Over the last years the clinical picture of autoimmune encephalitis has gained importance in neurology. The broad field of symptoms and syndromes poses a great challenge in diagnosis for clinicians. Early diagnosis and the initiation of the appropriate treatment is the most relevant step in the management of the patients. Over the last years advances in neuroimmunology have elucidated pathophysiological basis and improved treatment concepts. In this monocentric study we compare demographics, diagnostics, treatment options and outcomes with knowledge from literature. We present 38 patients suffering from autoimmune encephalitis. Antibodies were detected against NMDAR and LGI1 in seven patients, against GAD in 6 patients) one patient had coexisting antibodies against GABA_A and GABA_B), against CASPR2, IGLON5, YO, Glycine in 3 patients, against Ma-2 in 2 patients, against CV2 and AMPAR in 1 patient; two patients were diagnosed with hashimoto encephalitis with antibodies against TPO/TG. First, we compare baseline data of patients who were consecutively diagnosed with autoimmune encephalitis from a retrospective view. Further, we discuss when to stop immunosuppressive therapy since how long treatment should be performed after clinical stabilization or an acute relapse is still a matter of debate. Our experiences are comparable with data from literature. However, in contrary to other experts in the field we stop treatment and monitor patients very closely after tumor removal and after rehabilitation from first attack.

Management and prognostic markers in patients with autoimmune encephalitis requiring ICU treatment

Objective

To assess intensive care unit (ICU) complications, their management, and prognostic factors associated with outcomes in a cohort of patients with autoimmune encephalitis (AE).

Methods

This study was an observational multicenter registry of consecutively included patients diagnosed with AE requiring Neuro-ICU treatment between 2004 and 2016 from 18 tertiary hospitals. Logistic regression models explored the influence of complications, their management, and diagnostic findings on the dichotomized (0–3 vs 4–6) modified Rankin Scale score at hospital discharge.

Results

Of 120 patients with AE (median age 43 years [interquartile range 24–62]; 70 females), 101 developed disorders of consciousness, 54 autonomic disturbances, 42 status epilepticus, and 39 severe sepsis. Sixty-eight patients were mechanically ventilated, 85 patients had detectable neuronal autoantibodies, and 35 patients were seronegative. Worse neurologic outcome at hospital discharge was associated with necessity of mechanical ventilation (sex- and age-adjusted OR 6.28; 95% CI, 2.71–15.61) tracheostomy (adjusted OR 6.26; 95% CI, 2.68–15.73), tumor (adjusted OR 3.73; 95% CI, 1.35–11.57), sepsis (adjusted OR 4.54; 95% CI, 1.99–10.43), or autonomic dysfunction (adjusted OR 2.91; 95% CI, 1.24–7.3). No significant association was observed with autoantibody type, inflammatory changes in CSF, or pathologic MRI.

Conclusion

In patients with AE, mechanical ventilation, sepsis, and autonomic dysregulation appear to indicate longer or incomplete convalescence. Classic ICU complications better serve as prognostic markers than the individual subtype of AE. Increased awareness and effective management of these AE-related complications are warranted, and further prospective studies are needed to confirm our findings and to develop specific strategies for outcome improvement.