Extralimbic autoimmune encephalitis associated with glutamic acid decarboxylase antibodies: an underdiagnosed entity?

Immunotherapy-responsive Non-paraneoplastic Encephalitis with Antibodies against GAD, LGI1, and GABAA Receptor

A 62-year-old man showed abnormal behavior. Brain magnetic resonance imaging revealed multifocal lesions on T2-weighted images. Initial screening revealed that he was seropositive for antibodies against glutamate decarboxylase, which usually indicates treatment resistance to autoimmune encephalitis (AE). Intensive immunosuppressive therapies, however, improved the neurological symptoms. In line with this, we also detected seropositivity for antibodies against leucine-rich glioma-inactivated 1 and gamma-aminobutyric acid A receptor (GABA_AR). Brain imaging and treatment responsiveness suggested that antibodies against GABA_AR were the main cause of symptoms. Furthermore, the patient showed the presence of triple anti-neural antibodies in the absence of malignancy and had a favorable clinical course.

Immune-mediated epilepsy with GAD65 antibodies

Anti-GAD65 antibodies have been identified in both acute/subacute seizures (limbic encephalitis and extralimbic encephalitis) and chronic isolated epilepsy. The evidence of high serum titers and intrathecal synthesis play a fundamental role in diagnosis but poorly correlate with disease severity or response to therapies. It remains controversial whether anti-GAD65 Abs are the pathogenic entity or only serve as a surrogate marker for autoimmune disorders mediated by cytotoxic T cells. Unlike other immune-mediated epilepsy, although multiple combinations of therapeutics are used, the efficacy and prognosis of patients with GAD65-epilepsy patients are poor. Besides, GAD65-epilepsy is more prone to relapse and potentially evolve into a more widespread CNS inflammatory disorder. This article reviews the recent advances of GAD65-epilepsy, focusing on the diagnosis, epidemiology, pathophysiology, clinical features, and treatment, to better promote the recognition and provide proper therapy for this condition.

Predictive value of high titer of GAD65 antibodies in a case of limbic encephalitis

We report the case of a 42-year-old woman who presented with vertigo and migraine and rapidly developed cognitive decline and seizures. Both serum and cerebro-spinal fluid samples showed high titer of anti-glutamic acid decarboxylase (anti-GAD65) antibodies (998,881 IU/ml and 54,687 IU/ml respectively). Limbic encephalitis was diagnosed and high dose steroids treatment started. During one-year follow-up, without further immunomodulatory therapy, the patient became seizure free, and cognitive functions returned to normal. Serum anti-GAD65 antibodies titer decreased significantly but remained elevated (192,680 IU/ml). We discuss the prognostic and pathogenic value of high titer anti-GAD65 antibodies and its variations in a case of autoimmune limbic encephalitis.

Hippocampus and Insula Are Targets in Epileptic Patients With Glutamic Acid Decarboxylase Antibodies

Background: Antibodies to glutamic acid decarboxylase (GAD ab) have been found in patients with limbic encephalitis (LE) and chronic pharmacoresistant focal epilepsy (FE). The objectives of the study were to: (1) analyze the clinical and neuroimaging course of patients with FE+GAD ab, (2) compare these characteristics with a control group, and (3) describe the most affected cerebral areas with structural and functional imaging. Methods: Patients with FE + high titers of GAD ab and a follow-up of at least 5 years were selected. Titers of serum GAD ab exceeding 2,000 UI/ml were considered high. Evolutive clinical and radiological characteristics were studied in comparison to two different control groups: patients with bilateral or with unilateral mesial temporal sclerosis (BMTS or UMTS) of a non-autoimmune origin. Results: A group of 13 patients and 17 controls were included (8 BMTS, 9 UMTS). The most frequent focal aware seizures (FAS) reported by patients were psychic (5/13: 33%). Somatosensorial, motor, and visual FAS (4/13:32%) (p: 0.045), musicogenic reflex seizures (MRS), and a previous history of cardiac syncope were reported only patients (2/13:16% each) (p: NS). Comparing EEG characteristics between patients and controls, a more widespread distribution of interictal epileptiform discharges (IED) was observed in FE+ GAD ab patients than in controls (p:0.01). Rhythmic delta activity was observed in all controls in anterior temporal lobes while in patients this was less frequent (p: 0.001). No IED, even in 24 h cVEEG, was seen in 6 patients (46%).First MRI was normal in 4/5 (75%) patients. During the follow-up mesial temporal lobe (MTsL) sclerosis was observed in 5/8 (62%) of patients. All patients had abnormal FDG-PET study. MTL hypometabolism was observed in 10/11 (91%) patients, being bilateral in 7/11 (63%). In controls, this was observed in 16/17 (94%), and it was bilateral in 8/17 (47%) (p: NS). Insular hypometabolism was observed in 5/11 (45%) patients (P:0.002). Conclusions: Clinical, EEG, and FDG-PET findings in FE+GAD ab suggest a widespread disease not restricted to the temporal lobe. Progressive MTL sclerosis may be observed during follow-up. In comparison to what is found in patients with non-autoimmune MTL epilepsy, insular hypometabolism is observed only in patients with GAD ab, so it may be an important diagnostic clue.

Glutamate-Related Antibodies and Peripheral Insulin-Like Growth Factor in Bipolar Disorder and Lithium Prophylaxis

AIMS

The aim of this study was to evaluate serum levels of the antineuronal antibodies anti-N-methyl-D-aspartate receptor (NMDAR) and anti-glutamic acid decarboxylase (GAD), and insulin-like growth factor 1 (IGF-1), in patients with bipolar disorder (BD), during manic and depressive episodes and in remission compared to euthymic patients receiving long-term lithium therapy.

METHODS

Serum levels of anti-NMDAR and anti-GAD 450/620 antibodies, as well as IGF-1, were measured using the ELISA method in 19 manic and 17 depressed patients both in an acute episode and in remission after the episode. All of the subjects were under pharmacological treatment. The control group included 18 euthymic BD patients receiving lithium for 9-44 years (mean 22 ± 11) in whom a single measurement was performed.

RESULTS

Serum levels of anti-NMDAR antibodies were higher in acute manic episodes than in lithium-treated patients. Serum levels of anti-GAD 450/620 antibodies were higher in acute manic and depressive episodes compared to remission after the respective episode. Their values in both acute manic and depressive episodes were higher than those in lithium-treated patients. Serum levels of IGF-1 were higher in acute manic episodes and in remission after mania than in lithium-treated patients.

CONCLUSION

Higher levels of anti-NMDAR and anti-GAD antibodies during episodes may point to an abnormality in the glutamatergic system in BD. Increased levels of IGF-1 during an acute manic episode and in remission after mania may constitute a compensatory mechanism against excitotoxicity. Lower levels of anti-NMDAR, anti-GAD antibodies, and IGF-1 during long-term lithium treatment may reflect normalization of this processes, contributing to mood stabilization.

Autoimmune encephalitis associated with glutamic acid decarboxylase antibodies: a case series

Antibodies against glutamic acid decarboxylase (GAD) are associated with various neurologic conditions described in patients including stiff person syndrome, cerebellar ataxia, refractory epilepsy, limbic and extralimbic encephalitis. GAD antibodies-related limbic encephalitis cases are well described; reports of extralimbic involvement are limited. We describe four cases of GAD antibody-related autoimmune encephalitis. Three of them had extralimbic involvement and only one had limbic encephalitis.

Clinical Management of Epilepsy With Glutamic Acid Decarboxylase Antibody Positivity: The Interplay Between Immunotherapy and Anti-epileptic Drugs

Background: There is scanty guidance in the literature on the management of patients with glutamic acid decarboxylase (GAD65) antibody associated autoimmune epilepsy (GAD-epilepsy). GAD-epilepsy is a rare distinct neurological syndrome with a wide clinical spectrum. We describe six GAD-epilepsy patients with special emphasis on the treatment timing and the relationship between immunologic and anti-epileptic therapy.

Methods: Six patients diagnosed with GAD-epilepsy in Tampere University Hospital who had received immunotherapy from 2013 to 2017 were retrospectively analyzed from patient records. Data about symptom onset, including antibody levels, magnetic resonance imaging (MRI), electroencephalograms, immunotherapy and anti-epileptic treatment timing and treatment responses were collected and analyzed. Kruskall-Wallis test was used in the statistical evaluation.

Results: All patients were female aged 9–54 at symptom onset. Three had hypothyroidism, none had diabetes, two had migraine. Five patients had very high (>2,000 IU/ml) and one had high (52–251 IU/ml) GAD65 antibody titers. All patients presented with seizure disorders. Patients who received early initiation of immunotherapy (3–10 months) responded well to treatment; patients in whom the immunotherapy was started later (15–87 months) did not respond (p = 0.0495). The first patient was seizure-free after 1 year of regular intravenous immunoglobulin and one antiepileptic drug (AED). The second patient developed unilateral temporal lobe T2 signal changes in MRI; she responded well to immunotherapy, experiencing a significant reduction in seizure frequency and resolution of MRI abnormalities. However, seizures continued despite trials with several AEDs. The third patient responded well to immunoadsorption and rituximab with one AED, with lowering of GAD65 titers (from >2,000 to 300). There was a long delay in the diagnosis of GAD-epilepsy in the three patients who had developed refractory epilepsy, one with hippocampal sclerosis. They all received immunotherapy but none responded. However, AED modification or vagus nerve stimulation reduced the seizure frequency in two patients. Epilepsy surgery was ineffective.

Conclusions: These results highlight the importance of early detection of GAD65 antibodies in refractory epilepsy as immunotherapy can be effective if administered in the early stages of the disease when it can prevent permanent brain tissue damage.

Severe dysautonomia as a main feature of anti-GAD encephalitis: Report of a paediatric case and literature review

INTRODUCTION

Anti-glutamic acid decarboxylase (anti-GAD65) antibodies are a rare cause of autoimmune encephalitis. This entity is mainly recognized in adults and very few cases were reported in children. We report on a paediatric case of anti-GAD encephalitis with severe presentation and uncontrollable dysautonomia.

CASE STUDY

A 9-year-old girl was referred to our department for refractory seizures and behavioral disturbances. Brain magnetic resonance imaging (MRI) was normal. Repeat screening for antineuronal antibodies showed negative results for anti-NMDA receptor antibodies but positive results for anti-GAD65 with a low positivity of anti-Ma2 antibodies. Although a transient improvement was noticed after immunomodulatory treatment, the patient developed severe intractable autonomic imbalance including dysrythmia, alternating bradycardia/tachycardia, hypotension/hypertension, hypothermia/hyperthermia and hyperhidrosis. She deceased six months after onset.

CONCLUSION

Our report intends to raise awareness of autoimmune encephalitis with anti-GAD65 antibodies which may involve extralimbic brain regions and manifest with fatal dysautonomia. We highlight the need for prompt diagnosis and aggressive management for this underdiagnosed entity in children.

Evaluation of positive and negative predictors of seizure outcomes among patients with immune-mediated epilepsy: a meta-analysis

BACKGROUND

The objective of this study was to analyze published literature on autoimmune epilepsy and assess predictors of seizure outcome.

METHODS

From PubMed and EMBASE databases, two reviewers independently identified publications reporting clinical presentations, management and outcomes of patients with autoimmune epilepsy. A meta-analysis of 46 selected studies was performed. Demographic/clinical variables (sex, age, clinical presentation, epilepsy focus, magnetic resonance imaging [MRI] characteristics, time to diagnosis and initiation of immunomodulatory therapy, and type of immunomodulatory therapy) were compared between two outcome groups (responders and nonresponders). Clinical response was defined as >50% reduction in seizure frequency. Unstandardized effect sizes were collected for the studies for responder and nonresponder groups. Sample size was used as the weight in the meta-analysis. The random effects model was used to account for heterogeneity in the studies.

RESULTS

The 46 reports included 186 and 96 patients in responder and nonresponder groups respectively. Mean age of the responders and nonresponders was 43 and 31 years (p < 0.01). Responders were more likely to have cell-surface antibodies (68% versus 39%, p < 0.05), particularly voltage-gated potassium channel complex antibodies (p < 0.01). Mean duration from symptom onset to diagnosis, and symptom onset to initiation of immunomodulation was significantly lower among the responders (75 versus 431 days, p < 0.05, and 80 versus 554, p < 0.01, respectively). There was no outcome difference based on gender, MRI characteristics, seizure type, type of acute immunomodulatory therapy, or use of chronic immunomodulation.

CONCLUSIONS

Among published cases to date, older age, presence of cell-surface antibodies, early diagnosis and immunomodulatory treatment are associated with better seizure outcomes among patients with autoimmune epilepsy.

Antineuronal antibodies and infectious pathogens in severe acute pediatric encephalitis

The pathogenesis of acute encephalitis is divided into either direct infection or by immune-mediated inflammation, but the cause is still unknown. This retrospective study aimed to screen antineuronal antibodies in children with severe acute encephalitis. Thirty-four children (22 boys and 12 girls) underwent assessments such as antineuronal antibodies survey for autoimmune encephalitis and polymerase chain reaction/viral culture and antibody assays for all commonly recognized causes of infectious encephalitis. Sixteen (47.1%) were positive for autoantibodies, including antiglutamic acid decarboxylase antibodies in 16 and voltage-gated potassium channel complex antibodies in 1. Sixteen patients (47.1%) had presumed infectious etiologies, including 6 with influenza, 6 with Mycoplasma pneumoniae, 3 with enterovirus, and 1 with herpes simplex virus. In this study, influenza and Mycoplasma pneumoniae infection are the main presumed causes of severe acute encephalitis in children, although an immune-mediated mechanism may also play a role.

Neuropsychological course of voltage-gated potassium channel and glutamic acid decarboxylase antibody related limbic encephalitis

BACKGROUND AND PURPOSE

Autoantibodies (abs) to glutamic acid decarboxylase (GAD) and to voltage-gated potassium channels (VGKC) induce distinct courses of limbic encephalitis, related to MRI findings, seizure outcome and cognition.

METHODS

A detailed analysis of the cognitive course of the two forms is presented, spanning a median time interval of 28 months, including parameters of attention, learning and memory in 15 VGKC-ab-positive and 16 GAD-ab-positive patients.

RESULTS

In both groups, the initially significantly impaired attention performance recovered to a putatively premorbid level. In VGKC patients the partially severely impaired learning and memory performance improved under treatment but remained subnormal at last follow-up. By contrast, GAD-ab-positive patients had initially less impaired learning and memory scores but did not show an improvement under treatment.

CONCLUSIONS

The results provide evidence of distinct relations between inductive processes and cognitive outcome in VGKC-ab-positive and GAD-ab-positive subforms of limbic encephalitis, which possibly depend on differences in pathogenic molecular mechanisms and affected cerebral loci.

What should you know about limbic encephalitis?

Autoimmune encephalitis is an inflammatory disorder characterized by a subacute impairment of short-term memory, psychiatric features and seizures. It is often associated with a variety of other neurological symptoms, and its differential diagnosis is wide, leading to challenges in its recognition. It used to be regarded as a rare disease, usually paraneoplastic and with poor prognosis. However, with the recent recognition of membrane-surface directed antibodies, it is now known that in a substantial proportion of cases there is no association with any malignancy and there is a good prognosis if treated. Hence, early recognition and prompt initiation of immunotherapies are of great importance.

Neuroinflammation and psychiatric illness

Multiple lines of evidence support the pathogenic role of neuroinflammation in psychiatric illness. While systemic autoimmune diseases are well-documented causes of neuropsychiatric disorders, synaptic autoimmune encephalitides with psychotic symptoms often go under-recognized. Parallel to the link between psychiatric symptoms and autoimmunity in autoimmune diseases, neuroimmunological abnormalities occur in classical psychiatric disorders (for example, major depressive, bipolar, schizophrenia, and obsessive-compulsive disorders). Investigations into the pathophysiology of these conditions traditionally stressed dysregulation of the glutamatergic and monoaminergic systems, but the mechanisms causing these neurotransmitter abnormalities remained elusive. We review the link between autoimmunity and neuropsychiatric disorders, and the human and experimental evidence supporting the pathogenic role of neuroinflammation in selected classical psychiatric disorders. Understanding how psychosocial, genetic, immunological and neurotransmitter systems interact can reveal pathogenic clues and help target new preventive and symptomatic therapies.

Antiglutamic acid decarboxylase antibodies in children with encephalitis and status epilepticus

Encephalitis may present with seizures or status epilepticus, and the etiology is usually presumed. Specific antibodies to ion channels, receptors, and other synaptic proteins were identified during the past decade. However, only a few studies investigated antiglutamic acid decarboxylase antibodies and antibodies to cell membrane ion channels or surface antigens in pediatric encephalitis and status epilepticus. We examined antibodies to glutamic acid decarboxylase and cell membrane ion channels or surface antigens in acute-phase serum from 17 children with encephalitis and status epilepticus. Antiglutamic acid decarboxylase antibody titers were compared with those of control children manifesting therapy-resistant epilepsy. Antiglutamic acid decarboxylase antibody titers were significantly higher in those with encephalitis and status epilepticus than in those with therapy-resistant epilepsy. No patient demonstrated antibodies to cell membrane ion channels or surface antigens. Six children exhibited positive antiglutamic acid decarboxylase antibodies. One child died, three manifested postencephalitic epilepsy with neurologic deficits, and two recovered well. Higher antiglutamic acid decarboxylase antibody titers were evident in the children with encephalitis and status epilepticus. Clinicians should be aware of the potential role of antiglutamic acid decarboxylase antibodies in children with encephalitis and status epilepticus.