(18)F-FDG PET/CT and MRI findings in a patient with anti-GABA(B) receptor encephalitis

A novel classification model based on cerebral 18F-FDG uptake pattern facilitates the diagnosis of acute/subacute seropositive autoimmune encephalitis

PURPOSE

To explore the intrinsic alteration of cerebral 18F-FDG metabolism in acute/subacute seropositive autoimmune encephalitis (AE) and to propose a universal classification model based on 18F-FDG metabolic patterns to predict AE.

METHODS

Cerebral 18F-FDG PET images of 42 acute/subacute seropositive AE patients and 45 healthy controls (HCs) were compared using voxelwise and region of interest (ROI)-based schemes. The mean standardized uptake value ratios (SUVRs) of 59 subregions according to a modified Automated Anatomical Labeling (AAL) atlas were compared using a t-test. Subjects were randomly divided into a training set (70%) and a testing set (30%). Logistic regression models were built based on the SUVRs and the models were evaluated by determining their predictive value in the training and testing sets.

RESULTS

The 18F-FDG uptake pattern in the AE group was characterized by increased SUVRs in the brainstem, cerebellum, basal ganglia, and temporal lobe, and decreased SUVRs in the occipital, and frontal regions with voxelwise analysis (false discovery rate [FDR] p<0.05). Utilizing ROI-based analysis, we identified 15 subareas that exhibited statistically significant changes in SUVRs among AE patients compared to HC (FDR p<0.05). Further, a logistic regression model incorporating SUVRs from the calcarine cortex, putamen, supramarginal gyrus, cerebelum_10, and hippocampus successfully enhanced the positive predictive value from 0.76 to 0.86 when compared to visual assessments. This model also demonstrated potent predictive ability, with AUC values of 0.94 and 0.91 observed for the training and testing sets, respectively.

CONCLUSIONS

During the acute/subacute stages of seropositive AE, alterations in SUVRs appear to be concentrated within physiologically significant regions, ultimately defining the general cerebral metabolic pattern. By incorporating these key regions into a new classification model, we have improved the overall diagnostic efficiency of AE.

Discrimination between leucine-rich glioma-inactivated 1 antibody encephalitis and gamma-aminobutyric acid B receptor antibody encephalitis based on ResNet18

This study aims to discriminate between leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis and gamma-aminobutyric acid B (GABAB) receptor antibody encephalitis using a convolutional neural network (CNN) model. A total of 81 patients were recruited for this study. ResNet18, VGG16, and ResNet50 were trained and tested separately using 3828 positron emission tomography image slices that contained the medial temporal lobe (MTL) or basal ganglia (BG). Leave-one-out cross-validation at the patient level was used to evaluate the CNN models. The receiver operating characteristic (ROC) curve and the area under the ROC curve (AUC) were generated to evaluate the CNN models. Based on the prediction results at slice level, a decision strategy was employed to evaluate the CNN models' performance at patient level. The ResNet18 model achieved the best performance at the slice (AUC = 0.86, accuracy = 80.28%) and patient levels (AUC = 0.98, accuracy = 96.30%). Specifically, at the slice level, 73.28% (1445/1972) of image slices with GABAB receptor antibody encephalitis and 87.72% (1628/1856) of image slices with LGI1 antibody encephalitis were accurately detected. At the patient level, 94.12% (16/17) of patients with GABAB receptor antibody encephalitis and 96.88% (62/64) of patients with LGI1 antibody encephalitis were accurately detected. Heatmaps of the image slices extracted using gradient-weighted class activation mapping indicated that the model focused on the MTL and BG for classification. In general, the ResNet18 model is a potential approach for discriminating between LGI1 and GABAB receptor antibody encephalitis. Metabolism in the MTL and BG is important for discriminating between these two encephalitis subtypes.

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.

18 F-fluorodeoxy-glucose positron emission tomography pattern and prognostic predictors in patients with anti-GABAB receptor encephalitis

Aims

To identify the metabolic pattern and prognostic predictors in anti‐gamma‐aminobutyric‐acid B (GABAB) receptor encephalitis using ¹⁸F‐fluorodeoxy‐glucose positron emission tomography (¹⁸F‐FDG‐PET).

Methods

Twenty‐one patients diagnosed anti‐GABAB receptor encephalitis who underwent ¹⁸F‐FDG‐PET at first hospitalization were retrospectively reviewed. ¹⁸F‐FDG‐PET images were analyzed in comparison with controls. Further group comparisons of ¹⁸F‐FDG‐PET data were carried out between prognostic subgroups.

Results

¹⁸F‐FDG‐PET was abnormal in 81% patients with anti‐GABAB receptor encephalitis and was more sensitive than MRI (81% vs. 42.9%, p = 0.025). Alter limbic lobe glucose metabolism (mostly hypermetabolism) was observed in 14 patients (66.7%), of whom 10 (10/14, 71.4%) demonstrated hypermetabolism in the medial temporal lobe (MTL). Group analysis also confirmed MTL hypermetabolism in association with relative frontal and parietal hypometabolism was a general metabolic pattern. After a median follow‐up of 33 months, the group comparisons revealed that patients with poor outcome demonstrated increased metabolism in the MTL compared to those with good outcome.

Conclusion

¹⁸F‐FDG‐PET may be more sensitive than MRI in the early diagnosis of anti‐GABAB receptor encephalitis. MTL hypermetabolism was associated with relative frontal or parietal hypometabolism and may serve as a prognostic biomarker in anti‐GABAB receptor encephalitis.

GABAB Receptors and Cognitive Processing in Health and Disease

GABA_B receptors are implicated in numerous central nervous system-based behaviours and mechanisms, including cognitive processing in preclinical animal models. Homeostatic changes in the expression and function of these receptors across brain structures have been found to affect cognitive processing. Numerous preclinical studies have focused on the role of GABA_B receptors in learning, memory and cognition per se with some interesting, although sometimes contradictory, findings. The majority of the existing clinical literature focuses on alterations in GABA_B receptor function in conditions and disorders whose main symptomatology includes deficits in cognitive processing. The aim of this chapter is to delineate the role of GABA_B receptors in cognitive processes in health and disease of animal models and human clinical populations. More specifically, this review aims to present literature on the role of GABA_B receptors in animal models with cognitive deficits, especially those of learning and memory. Further, it aims to capture the progress and advances of research studies on the effects of GABA_B receptor compounds in neurodevelopmental and neurodegenerative conditions with cognitive dysfunctions. The neurodevelopmental conditions covered include autism spectrum disorders, fragile X syndrome and Down's syndrome and the neurodegenerative conditions discussed are Alzheimer's disease, epilepsy and autoimmune anti-GABA_B encephalitis. Although some findings are contradictory, results indicate a possible therapeutic role of GABA_B receptor compounds for the treatment of cognitive dysfunction and learning/memory impairments for some of these conditions, especially in neurodegeneration. Moreover, future research efforts should aim to develop selective GABA_B receptor compounds with minimal, if any, side effects.

18F-FDG PET/CT in Initial Diagnosis and Treatment Response Evaluation of Anti-NMDAr and Anti-GAD Dual Antibody Autoimmune Encephalitis

We report a case of 34-year-old woman presenting with complaints of abnormal posturing of hand and tonic-clonic seizures of few days' duration, which soon progressed to psychotic episodes and injuries secondary to fall/abnormal movements. She underwent F-FDG PET for a suspicion of encephalitis, which revealed increased FDG uptake in the bilateral parietotemporal lobes (right more than left), anterior cingulate cortex, bilateral basal ganglia, thalami, and cerebellum. This atypical pattern did not conform to any known pattern of encephalitis, which was later attributed to the presence of both anti-NMDAr and anti-GAD antibodies in blood and cerebrospinal fluid.

Diagnostic Value of Structural and Functional Neuroimaging in Autoimmune Epilepsy

Epilepsy is a common nervous system disease, which affects about 70 million people all over the world. In 2017, the International League Against Epilepsy (ILAE) considered immune factors as its independent cause, and the concept of autoimmune epilepsy (AE) was widely accepted. Early diagnosis and timely treatment can effectively improve the prognosis of the disease. However, due to the diversity of clinical manifestations, the expensive cost of autoantibody detection, and the increased prevalence in Western China, the difficulty for clinicians in early diagnosis and treatment has increased. Fortunately, convenient and fast imaging examinations are expected to help even more. The imaging manifestations of AE patients were characteristic, especially the combined application of structural and functional neuroimaging, which improved the diagnostic value of imaging. In this paper, several common autoantibodies associated with AE and their structure and function changes in neuroimaging were reviewed to provide help for neurologists to achieve the goal of precision medicine.

Etoposide and immunotherapy can improve the outcome of severe anti-GABAB R encephalitis presenting with delta brush: A case report

RATIONALE

Anti-gamma-aminobutyric-acid B receptor (anti-GABAB R) encephalitis is clinically characterized by seizures, cognitive disorders, and behavioral changes. Most patients are diagnosed with small-cell lung carcinoma.

PATIENT CONCERNS

The patient suffered from a repeated grand mal seizure lasting for 10 minutes, intermittent speech vagueness, manic at night, and mental disorder.

DIAGNOSIS

The patient was diagnosed with autoimmune encephalitis. The gamma-aminobutyric-acid B(GABAB) receptor antibody test result was positive. After a bronchoscopic biopsy, the patient was diagnosed with small-cell lung carcinoma.

INTERVENTIONS

The patient was administered with intravenous immunoglobulin and Methylprednisolone. Etoposide was used after the small-cell lung carcinoma was diagnosed.

OUTCOMES

After immunotherapy, following the 4 months of Etoposide and antiseizure treatment, the neurology examination revealed a remarkable improvement. MRS score reduced from 5 to 1. Electroencephalogram (EEG) recovered to normal from an extreme delta brush (EDB) electroencephalographic-pattern.

CONCLUSION

Immunotherapy and Etoposide can improve the outcome of severe anti-γ-aminobutyric acid B receptor encephalitis with small-cell lung carcinoma. After immunotherapy and antineoplastic therapy, Electroencephalogram (EEG) can be recovered to normal from an extreme delta brush.

Neuroimmunological antibody-mediated encephalitis and implications for diagnosis and therapy in neuropsychiatry

The past decade has seen a surge of reports and investigations into cases of autoimmune-mediated encephalitis. The increasing recognition of these disorders is especially of relevance to the fields of neurology and psychiatry. Autoimmune encephalitis involves antibodies against synaptic receptors, neuronal cell surface proteins and intracellular targets. These disorders feature prominent symptoms of cognitive impairment and behavioural changes, often associated with the presence of seizures. Early in the clinical course, autoimmune encephalitis may manifest as psychiatric symptoms of psychosis and involve psychiatry as an initial point of contact. Although commonly associated with malignancy, these disorders can present in the absence of an inciting neoplasm. The identification of autoimmune encephalitis is of clinical importance as a large proportion of individuals experience a response to immunotherapy. This review focuses on the current state of knowledge on n-methyl-d-aspartate (NMDA) receptor-associated encephalitis and limbic encephalitis, the latter predominantly involving antibodies against the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, the γ-aminobutyric acid (GABA)B receptor and leucine-rich glioma-inactivated 1 (LGI1) protein. In addition, we briefly describe anti-dopamine D2 receptor encephalitis. A summary of the literature will focus on common clinical presentations and course, diagnostic approaches and response to treatment. Since a substantial proportion of patients with autoimmune encephalitis exhibit symptoms of psychosis, the relevance of this disorder to theories of psychosis and schizophrenia will also be discussed.

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.

The Clinical Value of 18 F-FDG-PET in Autoimmune Encephalitis Associated With LGI1 Antibody

Purpose: The metabolic patterns of ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG-PET) in autoimmune encephalitis associated with leucine-rich glioma-inactivated 1 antibody (LGI1 AE) are still unclear. We performed a cohort study to investigate the clinical metabolic characteristics and diagnostic value based on ¹⁸F-FDG-PET in patients with LGI1 AE.

Materials and Methods: A total of 34 patients including 18 patients (53%) in the acute phase and 16 patients (47%) in the chronic phase who were diagnosed with LGI1 AE were retrospectively analyzed from October 2014 to June 2018 at the Department of Neurology in Beijing Tiantan Hospital, the Capital Medical University. The clinical data were collected by searching through electronic medical records.

Results: The initial ¹⁸F-FDG-PET scan indicated a significant abnormal metabolic pattern in 31 LGI1 AE patients (91%), whereas only 20 patients (59%) showed an abnormal MRI signal (P < 0.05). The ¹⁸F-FDG-PET metabolic pattern was reversible after treatment; most of the patients showed an almost normal uptake of ¹⁸F-FDG-PET after discharge. Regarding the spatial distribution, the abnormal metabolic pattern in LGI1 AE subjects exhibiting hypermetabolism was specifically located in the basal ganglia (BG) and medial temporal lobe (MTL). BG hypermetabolism was observed in 28 subjects (82%), and 68% of patients showed MTL hypermetabolism. A total of 17 patients (50%) exhibited faciobrachial dystonic seizures (FBDS), and the remaining subjects showed non-FBDS symptoms (50 and 50%). BG-only hypermetabolism was detected in seven subjects in the FBDS subgroup (7/16) but in only one subject in the non-FBDS subgroup (1/15) (44 vs. 7%, P < 0.05).

Conclusion:¹⁸F-FDG-PET imaging was more sensitive than MRI in the diagnosis of LGI1 AE. Isolated BG hypermetabolism was more frequently observed in subjects with FBDS, suggesting the potential involvement of the BG.

Autoimmune Encephalitis Associated with Anti-gamma-aminobutyric Acid B Receptor Antibodies Mimicking Syncope

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

Typical clinical and imaging manifestations of encephalitis with anti-γ-aminobutyric acid B receptor antibodies: clinical experience and a literature review

OBJECTIVE

To explore the clinical, imaging, and electroencephalogram (EEG) findings, as well as the treatment and prognosis of five patients with anti-γ-aminobutyric acid B receptor (GABA_BR) encephalitis and review the current literature to gain a deeper understanding and improve the clinical diagnostic ability of the disease.

METHODS

Clinical data such as blood examination, imaging, computed tomography (CT), EEG, and magnetic resonance imaging (MRI) findings from five patients with anti-GABA_BR encephalitis were retrospectively analyzed.

RESULTS

Based on the imaging data, autoimmune encephalitis with anti-GABA_BR antibodies displayed subacute onset of episodic memory loss, seizures, and confusion, in addition to signal changes in the medial temporal lobe and/or hippocampus. Anti-GABA_BR antibodies were found in blood and cerebrospinal fluid (CSF) in all five patients, although the CSF leukocyte count and the levels of protein, sugar, and chloride showed no obvious abnormalities. On MRI, only two patients presented with abnormal signals in the medial temporal lobe and/or hippocampus. The EEG showed a slow wave rhythm in all five patients. After treatment with methylprednisolone pulse therapy combined with antiepileptic treatment, all five patients recovered well, without any complications.

CONCLUSIONS

Autoimmune encephalitis with anti-GABA_BR antibodies may be a severe and refractory disease. Anti-GABA_BR antibodies tested in CSF and serum play a crucial role in the definitive diagnosis and treatment of autoimmune encephalitis. Early treatment is of vital importance to avoid serious complications and neurological sequelae.

Autoimmune epilepsy: findings on MRI and FDG-PET

Autoimmune epilepsy (AE) is becoming increasingly recognized as a potentially reversible cause of frequent or medically intractable seizures and cognitive deterioration. We describe various presentations of autoimmune encephalopathy which have specifically presented with seizure and describe reported imaging findings. This is organized as a review of the more common autoantibodies which can specifically precipitate seizure according to the intracellular or extracellular location of the targeted antigen. For each antibody, we illustrate their pathophysiology, characteristic clinical presentations with typical effective treatments and prognoses and imaging findings on MRI and PET/CT exams. Parenchymal involvement is variable with the limbic structures typically affected; however, non-limbic cortex, cerebellum, brainstem and basal ganglia can also be involved. In the acute setting, affected regions typically demonstrate T₂ hyperintensity with mild mass effect from edema and increased ¹⁸F-fludeoxyglucose uptake. Chronically involved parenchyma will often undergo atrophy and demonstrate decreased metabolism; mesial temporal sclerosis is often the end result when the limbic system is involved. Without treatment, long-term effects from AE range from ongoing cognitive dysfunction and refractory seizures to death. Familiarity with AE may prompt appropriate antibody screening, particularly in cases of refractory seizure disorders. Early investigation and proper management of AE cases may help to prevent parenchymal and neurologic deterioration in these patients.

Coexistence of Lambert-Eaton myasthenic syndrome and autoimmune encephalitis with anti-CRMP5/CV2 and anti-GABAB receptor antibodies in small cell lung cancer: A case report

RATIONALE

Autoimmune encephalitis and Lambert-Eaton myasthenic syndrome are classic paraneoplastic neurological conditions common in patients with small cell lung cancer.

PATIENT CONCERNS

The patient complained of tiredness, fluctuating recent memory loss, and inability to find his home. His family members reported a change in character, irritability, and paranoia. One month later, the patient had 1 grand mal seizure lasting 5 minutes.

DIAGNOSIS

The patient was diagnosed with limbic encephalitis combined with Lambert-Eaton myasthenic syndrome. The gamma-aminobutyric acid B (GABAB) receptor and collapsin response mediator protein 5 (CRMP5, also called CV2) antibody test results were positive. Nine months after the onset of symptoms, the patient was diagnosed with small cell lung cancer.

INTERVENTIONS

The patient was administered intravenous immunoglobulin for 5 days. He was then treated with 60 mg prednisone once per day. The prednisone dose was gradually reduced by 1 tablet every 2 weeks. After the diagnosis, the patient underwent 6 courses of chemotherapy with cisplatin combined with sequential chemoradiation therapy.

OUTCOMES

The patient was able to take care of himself. Neurological examination revealed a lower limb proximal muscle strength level of 4 and a reduced limb tendon reflex. The patient had deficits in short-term memory, a Mini-Mental State Examination score of 26, Montreal Cognitive Assessment score of 24, Self-rating Depression Scale score of 54 (mild depression), and Self-Rating Anxiety Scale score of 42 (normal).

LESSONS

Autoimmune diseases of the peripheral and central nervous systems can be observed at the same time in patients with small cell lung cancer, even when magnetic resonance imaging findings are negative and immune therapy is effective.