Uncommon 18F-FDG-PET/CT findings in patients affected by limbic encephalitis: hyper-hypometabolic pattern with double antibody positivity and migrating foci of hypermetabolism

Interesting Manifestation of Autoimmune Encephalitis on FDG PET Scan

ABSTRACT

We are presenting a 22-year-old man with intractable seizures. Autoimmune epilepsy, vasculitis, and paraneoplastic disorder were among initial differential diagnoses. His initial laboratory tests and toxicology screen were unremarkable. His initial brain MRI demonstrated generalized cortical atrophy. Features such as progressive encephalopathy, neuropsychiatric symptoms, personality change, and autonomic dysfunction were in favor of autoimmune encephalitis. Autoantibody evaluations including anti-NMDA receptor (NR1) IgG were negative in both serum and CSF samples. FDG PET scan demonstrated intense FDG uptake in the basal ganglia, more prominent in the caudate nuclei and putamina, which is one of the known autoimmune encephalitis imaging features.

Unconventional non-amino acidic PET radiotracers for molecular imaging in gliomas

PURPOSE

The objective of this review was to explore the potential clinical application of unconventional non-amino acid PET radiopharmaceuticals in patients with gliomas.

METHODS

A comprehensive search strategy was used based on SCOPUS and PubMed databases using the following string: ("perfusion" OR "angiogenesis" OR "hypoxia" OR "neuroinflammation" OR proliferation OR invasiveness) AND ("brain tumor" OR "glioma") AND ("Positron Emission Tomography" OR PET). From all studies published in English, the most relevant articles were selected for this review, evaluating the mostly used PET radiopharmaceuticals in research centers, beyond amino acid radiotracers and 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG), for the assessment of different biological features, such as perfusion, angiogenesis, hypoxia, neuroinflammation, cell proliferation, tumor invasiveness, and other biological characteristics in patients with glioma.

RESULTS

At present, the use of non-amino acid PET radiopharmaceuticals specifically designed to assess perfusion, angiogenesis, hypoxia, neuroinflammation, cell proliferation, tumor invasiveness, and other biological features in glioma is still limited.

CONCLUSION

The use of investigational PET radiopharmaceuticals should be further explored considering their promising potential and studies specifically designed to validate these preliminary findings are needed. In the clinical scenario, advancements in the development of new PET radiopharmaceuticals and new imaging technologies (e.g., PET/MR and the application of the artificial intelligence to medical images) might contribute to improve the clinical translation of these novel radiotracers in the assessment of gliomas.

Brain and Muscle Metabolic Changes by FDG-PET in Stiff Person Syndrome Spectrum Disorders

Objective: To report clinical characteristics and fluorodeoxyglucose positron emission tomography (FDG-PET) findings in the brain and muscles of individuals with stiff person syndrome (SPS) spectrum disorders (SPSSDs).

Methods: Retrospective cohort study from 1997 to 2018 at Johns Hopkins Hospital identified 170 individuals with SPS or cerebellar ataxia (CA) associated with anti-glutamic acid decarboxylase (anti-GAD)-65 antibodies. Fifty-one underwent FDG-PET, with 50 involving the body and 30 with dedicated brain acquisition. The clinical and immunological profiles were extracted via medical record review. The brain scans were analyzed quantitatively using the NeuroQ software, with comparison with an averaged normal database. The body scans were reviewed qualitatively by a blinded nuclear medicine radiologist.

Results: Mean age of symptom onset was 41.5 years (range 12–75 years). Majority were female (68%) and White (64%). Of the patients, 82% had SPS (majority being classic phenotype), and 18% had CA. Three had a paraneoplastic process. Forty-seven had serum anti-GAD, two with anti-amphiphysin, and one with anti-glycine receptor antibodies. Brain metabolic abnormalities were seen in both SPS and CA, with significant differences between the groups noted in the right superior frontal cortex, right sensorimotor cortex, left inferior parietal cortex, bilateral thalami, vermis, and left cerebellum. Of the patients, 62% demonstrated muscle hypermetabolism, most commonly bilateral, involving the upper extremities or axial muscles. Neither brain nor muscle metabolism was correlated with functional outcomes nor treatments.

Conclusions: Metabolic changes as seen by FDG-PET are present in the brain and muscle in many individuals with SPSSD. Future studies are needed to assess whether FDG-PET can help aid in the diagnosis and/or monitoring of individuals with SPSSD.

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.

Autoimmune Encephalitis in Late-Onset Seizures: When to Suspect and How to Treat

Objective: This study was conducted to elucidate prevalence, clinical features, outcomes, and best treatment in patients with late-onset seizures due to autoimmune encephalitis (AE). Methods: This is a single-institution prospective cohort study (2012-2019) conducted at the Epilepsy Center at the University of Greifswald, Germany. A total of 225 patients aged ≥50 years with epileptic seizures were enrolled and underwent an MRI/CT scan, profiling of neural antibodies (AB) in serum and cerebrospinal fluid (CSF), and neuropsychological testing. On the basis of their work-up, patients were categorized into the following three cohorts: definite, suspected, or no AE. Patients with definite and suspected AE were subsequently treated with immunosuppressive therapy (IT) and/or anti-seizure drug (ASD) therapy and were followed up (FU) regarding clinical and seizure outcome. Results: Of the 225 patients, 17 (8%) fulfilled the criteria for definite or suspected AE according to their AB profile and MRI results. Compared with patients with no evidence of AE, those with AE were younger (p = 0.028), had mesial temporal neuropsychological deficits (p = 0.001), frequently had an active or known malignancy (p = 0.006) and/or a pleocytosis (p = 0.0002), and/or had oligoclonal bands in CSF (p = 0.001). All patients with follow-up became seizure-free with at least one ASD. The Modified Rankin scale (mRS) at hospital admission was low for patients with AE (71% with mRS ≤2) and further decreased to 60% with mRS ≤2 at last FU. Significance: AE is an important etiology in late-onset seizures, and seizures may be the first symptom of AE. Outcome in non-paraneoplastic AE was favorable with ASD and IT. AB testing in CSF and sera, cerebral MRI, CSF analysis, and neuropsychological testing for mesial temporal deficits should be part of the diagnostic protocol for AE following late-onset seizures.

Initial results of the use of a novel semiquantitative parameter in three-phase bone scan to predict 99mTc-HMPAO-labeled leukocyte scintigraphy in patients with unilateral total knee replacement

OBJECTIVES

The aim of the study was to predict the results of 99mTc-hexamethylpropyleneamine oxime (HMPAO)-labeled autologous leukocytes scintigraphy assessing count ratios in the perfusion (Pr) and blood-pool (BPr) phase images in three-phase bone scan (3PBSr) between the prosthetic knee and the 'healthy' knee and a novel semiquantitative parameter (P/BP ratio) in patients with unilateral knee arthroplasty.

METHODS

Patients with unilateral knee arthroplasty and available 3PBS and 99mTc-HMPAO-labeled autologous leukocytes scintigraphic images were searched in two hospitals (A and B). In center A, the perfusion phase was not available. Regions of interest (ROI) were delineated in the perfusion (P) and blood-pool (BP) phase images, incorporating the prosthetic region and applying an isocontour (40% of the maximum pixel activity); corresponding mirror ROIs were placed on the healthy knee. The P/BP ratio was calculated as {[(Pr/BPr) × 100] - 100}. Receiver operator curves (ROCs) were generated for each semiquantitative parameter to identify the optimal cutoff for predicting the results of the autologous leukocytes scintigraphy.

RESULTS

In the whole group (79 patients), BPr demonstrated an area under the curve (AUC) of 0.722 (optimal cutoff = 1.43). In center A (52 patients), BPr demonstrated an AUC of 0.737 (cutoff = 1.43), whereas, in center B (27 patients), AUC for BPr was 0.718 (cutoff = 1.6). A better diagnostic performance was obtained selecting Pr (AUC = 0.918; cutoff = 2.34) and P/BP ratio (AUC = 0.947; cutoff = 26.5%) for the discrimination between septic and aseptic loosening.

CONCLUSIONS

The novel P/BP ratio seems to be a promising semiquantitative parameter to predict septic loosening. These findings warrant confirmation in larger patient samples.

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.

18F-FDG-PET brain imaging may highlight brain metabolic alterations in dysautonomic syndrome after human papilloma virus vaccination

AIM

The aim of this study was to evaluate brain glucose metabolism by means of [18F]-fluoro-deoxygluycose (F-FDG) PET in a group of patients presenting dysautonomic syndrome after human papilloma virus (HPV) immunization.

METHODS

Medical records of patients, referred to the 'Second Opinion Medical Consulting Network' Medical Centre (Modena, Italy) diagnosed with dysautonomic syndrome were searched. Inclusion criteria were presence in the medical history of adverse drug reactions following HPV vaccine; a Montreal Cognitive Assessment score <25 and good quality of a F-FDG-PET brain scan performed within 12 months from the diagnosis of dysautonomic syndrome. F-FDG-PET images of patients (HPV-group) were compared to a control group, matched for age and sex, using statistical parametric mapping (SPM).

RESULTS

The F-FDG-PET study was available for five female patients. The SPM-group analysis revealed significant hypometabolism (P < 0.05 false discovery rate corrected) in the right superior and medial temporal gyrus (Brodmann areas 22, 21) and insula (Brodmann area 13). At a threshold of P < 0.001 (uncorrected), further hypometabolic regions were revealed in the right superior temporal gyrus (Brodmann area 42) and caudate head and in the left superior temporal gyrus (Brodmann area 22), frontal subcallosal gyrus (Brodmann area 47) and insula (Brodmann area 13). Relative hypermetabolism (P = 0.001) was revealed in the right premotor cortex (Brodmann area 6).

CONCLUSION

This study revealed the possibility of altered brain glucose metabolism in subjects with dysautonomic syndrome post-immunization with HPV vaccine. These results could reinforce the hypothesis of a causal relationship between HPV vaccine, or some component included in the vaccine and the development of clinical manifestations.

18F-FDG PET Identifies Altered Brain Metabolism in Patients with Cri du Chat Syndrome

Cri du chat syndrome (CDCS) is a rare genetic disease that is caused by a deletion in the short arm of chromosome 5 (5p) and has a variable clinical spectrum. To our knowledge, no study in the literature has ever applied ¹⁸F-FDG PET/CT to investigate alterations in brain glucose metabolism in these subjects. The aims of this study were to detect differences in brain ¹⁸F-FDG metabolism in CDCS patients with different clinical presentations and identify possible brain metabolic phenotypes of this syndrome. Methods: Six patients (5 male and 1 female; age range, 10-27 y) with CDCS were assessed for the presence of cognitive and behavioral symptoms using a battery of neuropsychologic tests and then classified as having either a severe or a mild phenotype. The patients then underwent brain ¹⁸F-FDG PET/CT. The PET/CT findings were compared with an age- and sex-matched control group using statistical parametric mapping (SPM). Whether there was an association between different clinical phenotypes and ¹⁸F-FDG PET/CT findings was investigated. Results: Four patients had the severe phenotype, and 2 patients demonstrated the mild phenotype. SPM single-subject analysis, and a group analysis in comparison with the control cohort, revealed significant hypometabolism in the left temporal lobe (Brodmann areas [BAs] 20, 36, and 38), in the right frontal subcallosal gyrus (BA 34) and caudate body, and in the cerebellar tonsils (P < 0.001). Hypermetabolism (P = 0.001) was revealed in the right superior and precentral frontal gyrus (BA 6) in the patient group, compared with the control cohort. In SPM single-subject analysis, the hypermetabolic areas were detected only in patients with the severe phenotype. Conclusion: This study revealed different patterns of brain glucose metabolism in patients with the severe and mild phenotypes, compared with control subjects. In particular, abnormal hypermetabolism in the brain, as evaluated by¹⁸F-FDG PET/CT, seems to correlate with the severe CDCS phenotype.

Diagnosis and treatment of limbic encephalitis in the cancer patient

Limbic encephalitis is an inflammatory process involving the limbic structures of the brain, manifested with short-term memory deficits, confusion, depression and seizures. It is usually a paraneoplastic condition but it may also appear as a nonparaneoplastic syndrome. Patients with this condition may exhibit a variety of antibodies in their serum or/and cerebrospinal fluid targeting basement membrane components that bind to a variety of neurotransmitter receptors such as α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and GABA B and proteins associated to the ion channels such as LGI1, Caspr2 or intracellular components. Flurodeoxyglucose PET/computed tomography usually demonstrates increased uptake in the limbic structures, and it may reveal the site of the primary tumor. Treatment consists of tumor removal if possible. Symptomatic treatment includes steroids, gamma immune globulin, plasma exchange, immunosuppressive therapies and anti-epileptic drugs. Prognosis is better when it is associated with antibodies against basement membrane rather than intracellular antibodies.

18F-FDG-PET Imaging Patterns in Autoimmune Encephalitis: Impact of Image Analysis on the Results

Brain positron emission tomography imaging with 18Fluorine-fluorodeoxyglucose (FDG-PET) has demonstrated utility in suspected autoimmune encephalitis. Visual and/or assisted image reading is not well established to evaluate hypometabolism/hypermetabolism. We retrospectively evaluated patients with autoimmune encephalitis between 2003 and 2018. Patients underwent EEG, brain magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) sampling and autoantibodies testing. Individual FDG-PET images were evaluated by standard visual reading and assisted by voxel-based analyses, compared to a normal database. For the latter, three different methods were performed: two based on statistical surface projections (Siemens syngo.via Database Comparison, and 3D-SSP Neurostat) and one based on statistical parametric mapping (SPM12). Hypometabolic and hypermetabolic findings were grouped to identify specific patterns. We found six cases with definite diagnosis of autoimmune encephalitis. Two cases had anti-LGI1, one had anti-NMDA-R and two anti-CASPR2 antibodies, and one was seronegative. ¹⁸F-FDG-PET metabolic abnormalities were present in all cases, regardless of the method of analysis. Medial–temporal and extra-limbic hypermetabolism were more clearly depicted by voxel-based analyses. We found autoantibody-specific patterns in line with the literature. Statistical surface projection (SSP) methods (Neurostat and syngo.via Database Comparison) were more sensitive and localized larger hypermetabolic areas. As it may lead to comparable and accurate results, visual analysis of FDG-PET studies for the diagnosis of autoimmune encephalitis benefits from voxel-based analysis, beyond the approach based on MRI, CSF sample and EEG.

The Additional Value of 18F-FDG PET and MRI in Patients with Glioma: A Review of the Literature from 2015 to 2020

AIM

Beyond brain computed tomography (CT) scan, Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) hold paramount importance in neuro-oncology. The aim of this narrative review is to discuss the literature from 2015 to 2020, showing advantages or complementary information of fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET imaging to the anatomical and functional data offered by MRI in patients with glioma.

METHODS

A comprehensive Pubmed/MEDLINE literature search was performed to retrieve original studies, with a minimum of 10 glioma patients, published from 2015 until the end of April 2020, on the use of ¹⁸F-FDG PET in conjunction with MRI.

RESULTS

Twenty-two articles were selected. Combined use of the two modalities improves the accuracy in predicting prognosis, planning treatments, and evaluating recurrence.

CONCLUSION

According to the recent literature, ¹⁸F-FDG PET provides different and complementary information to MRI and may enhance performance in the whole management of gliomas. Therefore, integrated PET/MRI may be particularly useful in gliomas, since it could provide accurate morphological and metabolic information in one-shoot examination and improve the diagnostic value compared to each of procedures.

18F-FDG-PET/MRI in the diagnostic work-up of limbic encephalitis

Introduction

Limbic encephalitis (LE) is an immune-related, sometimes paraneoplastic process of the central nervous system. Initial diagnosis and treatment are based on the clinical presentation as well as antibody profiles and MRI. This study investigated the diagnostic value of integrated ¹⁸F-FDG-PET/MRI in the diagnostic work-up of patients with LE for a cerebral and whole-body imaging concept.

Material and methods

Twenty patients with suspected LE were enrolled in this prospective study. All patients underwent a dedicated PET/MRI protocol of the brain as well as the whole-body. Two neuroradiologists, one body radiologist and one nuclear medicine physician performed blinded consensus readings of each corresponding MRI and PET/MRI dataset of the brain and whole-body. Diagnostic confidence was evaluated on a Likert scale.

Results

Based on integrated PET/MRI 19 / 20 patients were found to show morphologic and / or metabolic changes indicative of LE, whereas sole MRI enabled correct identification in 16 / 20 patients. Three patients with negative MRI showed metabolic changes of the limbic system or extra-limbic regions, shifting the diagnosis from (negative) MRI to positive for LE in PET/MRI. Whole-body staging revealed suspected lesions in 2/20 patients, identified by MRI and PET, one confirmed as malignant and one false positive. Diagnostic confidence for cerebral and whole-body imaging reached higher scores for PET/MRI (cerebral: 2.7 and whole body: 4.8) compared to MRI alone (cerebral: 2.4 and whole body: 4.5).

Conclusion

LE diagnosis remains challenging for imaging as it shows only subtle imaging findings in most patients. Nevertheless, based on the simultaneous and combined analysis of morphologic and metabolic data, integrated PET/MRI may enable a dual platform for improved diagnostic confidence and overall detection of LE as well as whole-body imaging for exclusion of paraneoplastic LE.

Anti-Ma2-associated limbic encephalitis with coexisting chronic inflammatory demyelinating polyneuropathy in a patient with non-Hodgkin lymphoma: A case report

RATIONALE

We report the rare case of a 74-year-old man with anti-Ma2-associated paraneoplastic neurologic syndrome (PNS), and review and analyze the clinical manifestations, diagnosis, and treatment of the disease.

PATIENT CONCERNS

The patient presented with a 5-month history of muscle weakness, progressive body aches, and weakness and numbness in both lower extremities. Before his hospitalization, he had experienced cognitive function decline; ptosis, inward gaze, and vertical gaze palsy in the right eye; and occasional visual hallucinations. Brain and spinal cord magnetic resonance imaging (MRI) yielded normal results. Anti-Ma2 antibodies were detected in both serum and cerebrospinal fluid. A 4-hour electroencephalogram showed irregular sharp slow waves and δ waves in the temporal region. Electromyography showed peripheral nerve demyelination. Positron-emission tomography/computed tomography (PET-CT) examination revealed hypermetabolism in the lymph nodes of the whole body. Biopsy of the lymph nodes showed non-Hodgkin lymphoma.

DIAGNOSIS

A clinical diagnosis of lymphoma and PNS was made.

INTERVENTIONS

The patient was treated with intravenous dexamethasone (15 mg/day) for 3 days.

LESSONS

We have presented a rare case of a PNS involving both the central and peripheral nervous systems. The clinical features of this case indicated anti-Ma2-associated encephalitis and chronic inflammatory demyelinating polyneuropathy. PET-CT played a critical role in enabling early diagnosis and prompt treatment in this case.

Post-Encephalitic Parkinsonism and Sleep Disorder Responsive to Immunological Treatment: A Case Report

We describe a 70-year-old man who, after a viral encephalitis associated with pneumonia, progressively developed a parkinsonism associated with lethargy. Encephalitis manifested with persistent hiccups, seizures and impairment of consciousness. After 2 weeks, the initial neurologic symptoms subsided and the patient progressively developed movement disorders (rigidity and bradykinesia, resistant to L-DOPA), lethargy and behavioral hypersomnia. Magnetic resonance imaging showed thalamic and hippocampal signal abnormalities, immunohistochemistry on a mouse brain substrate revealed serum autoantibodies binding to the brainstem neuropil. Polysomnographic monitoring was consistent with a very severe disruption of sleep: the sleep-wake cycle was fragmented, and the NREM-REM ultradian cycle was irregular. Intravenous immune globulin therapy resulted in the complete reversal of the movement and the sleep disorders. Our observation confirms that parkinsonism and sleep disorders may be consequences of encephalitis, that an immune-mediated pathogenesis is likely, and, consequently, that immunotherapy can be beneficial in these patients. The polysomnographic monitoring suggests that lethargia, rather than a mere hypersomnia, is the result of a combination between sleep disruption and altered motor control.

Mapping autoantigen epitopes: molecular insights into autoantibody-associated disorders of the nervous system

BACKGROUND

Our knowledge of autoantibody-associated diseases of the central (CNS) and peripheral (PNS) nervous systems has expanded greatly over the recent years. A number of extracellular and intracellular autoantigens have been identified, and there is no doubt that this field will continue to expand as more autoantigens are discovered as a result of improved clinical awareness and methodological practice. In recent years, interest has shifted to uncover the target epitopes of these autoantibodies.

MAIN BODY

The purpose of this review is to discuss the mapping of the epitope targets of autoantibodies in CNS and PNS antibody-mediated disorders, such as N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), leucine-rich glioma-inactivated protein 1 (Lgi1), contactin-associated protein-like 2 (Caspr2), myelin oligodendrocyte glycoprotein (MOG), aquaporin-4 (AQP4), 65 kDa glutamic acid decarboxylase (GAD65), acetylcholine receptor (AChR), muscle-specific kinase (MuSK), voltage-gated calcium channel (VGCC), neurofascin (NF), and contactin. We also address the methods used to analyze these epitopes, the relevance of their determination, and how this knowledge can inform studies on autoantibody pathogenicity. Furthermore, we discuss triggers of autoimmunity, such as molecular mimicry, ectopic antigen expression, epitope spreading, and potential mechanisms for the rising number of double autoantibody-positive patients.

CONCLUSIONS

Molecular insights into specificity and role of autoantibodies will likely improve diagnosis and treatment of CNS and PNS neuroimmune diseases.

Cerebral (18)FluoroDeoxy-Glucose Positron Emission Tomography in paediatric anti N-methyl-D-aspartate receptor encephalitis: A case series

BACKGROUND

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a frequent and severe cause of encephalitis in children with potential efficient treatment (immunotherapy). Suggestive clinical features are behavioural troubles, seizures and movement disorders. Prompt diagnosis and treatment initiation are needed to guarantee favourable outcome. Nevertheless, diagnosis may be challenging because of the classical ancillary test (magnetic resonance imaging (MRI), electroencephalogram, standard cerebro-spinal fluid analysis) have limited sensitivity. Currently, immunological analyses are needed for the diagnostic confirmation. In adult patients, some studies suggested a potential role of cerebral (18)FluoroDeoxy-Glucose Positron Emission Tomography (FDG-PET) in the evaluation of anti-NMDAR encephalitis. Nevertheless, almost no data exist in paediatric population.

METHOD

We report retrospectively clinical, ancillary tests and cerebral FDG-PET data in 6 young patients (median age=10.5 years, 4 girls) with immunologically confirmed anti-NMDAR encephalitis.

RESULTS

Our patients presented classical clinical features of anti-NMDAR encephalitis with severe course (notably four patients had normal MRI). Our series shows the feasibility and the good sensitivity of cerebral FDG-PET (6/6 patients with brain metabolism alteration) in paediatric population. We report some particular features in this population: extensive, symmetric cortical hypometabolism especially in posterior areas; asymmetric anterior focus of hypermetabolism; and basal ganglia hypermetabolism. We found also a good correlation between the clinical severity and the cerebral metabolism changes. Moreover, serial cerebral FDG-PET showed parallel brain metabolism and clinical improvement.

CONCLUSION

Our study reveals the existence of specific patterns of brain metabolism alteration in anti-NMDAR encephalitis in paediatric population.

The role of PET/CT in the evaluation of patients affected by limbic encephalitis: A systematic review of the literature

Autoimmune limbic encephalitis (LE) is a rare disorder affecting the medial temporal lobe of the brain. Although brain Magnetic Resonance (MR) has been widely evaluated and is currently considered essential in the suspicion of LE, Positron Emission Tomography/Computed Tomography (PET/CT) has been demonstrated to be useful also in the evaluation of brain inflammatory diseases such as encephalitis. We therefore aim to review the current literature about the role of PET/CT in the evaluation of patients affected by LE.