Clinical significance of glutamic acid decarboxylase antibodies in patients with epilepsy

Immunotherapy in a case of low titre GAD65 antibody-associated spectrum neurological disorders

We present a rare case of low titre GAD65 antibody-associated autoimmune encephalitis and status epilepticus in a young woman. She initially presented with left arm dystonic movements, contractures and status epilepticus. Due to the concern of autoimmune encephalitis and seizures, the patient received intravenous immunoglobulin empirically. After the detection of low serum GAD65 antibodies, the patient underwent immunomodulation therapy with significant improvement. This case demonstrated that in autoimmune encephalitis, it is important to monitor serum GAD65 antibodies levels and consider immunotherapy, despite mildly elevated serum levels. The patient's history of left arm dystonic movements without impaired awareness may have been due to limb dystonia, a presenting symptom of stiff person syndrome (SPS), despite SPS more commonly affecting axial muscles. This case further demonstrates that GAD65 antibody-related syndromes can manifest with different neurological phenotypes including co-occurrence of epilepsy with possible focal SPS despite low GAD65 antibodies titres.

Hippocampal sclerosis is associated with celiac disease type immunity in patients with drug-resistant temporal lobe epilepsy

BACKGROUND

A prior small-scale single center study suggested an association between celiac disease (CD)-type immunity and refractory temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS). The present study addresses this putative association in a large, well-characterized group of drug-resistant epilepsy (DRE) patients. These patients were grouped based on the spectrum of CD and gluten sensitivity-associated antibodies.

METHODS

In this cross-sectional study, 253 consecutive adult epilepsy patients (135 females, 118 males; age 16-76 years) were categorized into three groups: (i) CD-positive group with either prior diagnosis of CD or CD-specific TG2/EmA antibodies, (ii) AGA-positive group with antigliadin antibodies (AGA) but without CD, and (iii) CD/AGA-negative group without any gluten sensitivity-associated antibodies or CD. Clinical and immunological findings were then compared among the groups.

RESULTS

TLE with HS was more common in the CD-positive group compared to CD/AGA-negative group (31.8% versus 11.9%, P = 0.019). Autoimmune disorders were more common in the AGA-positive group than in the CD/AGA-negative group (P = 0.025). Considering HS lateralization; left lateralization was more common in CD-positive group compared to CD/AGA-negative group (71.4% versus 25%, P = 0.030). TG6 seropositivity did not differ among the groups (P > 0.05).

CONCLUSIONS

This study provides further evidence linking TLE with HS and CD-type autoimmunity suggesting that CD-type immune response to gluten can be one potential mechanism as a disease modifier leading to DRE and HS. Understanding these immunological factors is imperative for developing immunomodulatory or dietary treatments for DRE potentially preventing HS progression.

Stiff-Leg Syndrome Associated with Autoimmune Retinopathy and Its Treatment with IVIg-A Case Report and Review of the Literature

Antibodies to glutamic acid decarboxylase (GAD) have been predominantly associated with stiff-person syndrome (SPS), which is often accompanied by organ-specific autoimmune diseases, such as late-onset type 1 diabetes. Autoimmune retinal pathology in SPS has recently been suggested to coexist in patients suffering from this disease; however, evidence reporting potential treatment options for the neurological and visual symptoms these patients experience remains scarce. We provide a review of the relevant literature, presenting a rare case of a middle-aged woman with autoimmune retinopathy (AIR) followed by stiff-leg syndrome who responded to intravenous immune globulin treatment (IVIg). Our report adds to previously reported data supporting the efficacy of IVIg in SPS spectrum disorders while also proposing the potential effect of IVIg in treating SPS spectrum patients with coexisting AIR.

High frequency of cerebrospinal fluid autoantibodies in patients with seizures or epilepsies of unknown etiology

Introduction

The increasing identification of specific autoantibodies against brain structures allows further refinement of the group of autoimmune-associated epilepsies and affects diagnostic and therapeutic algorithms. The early etiological allocation of a first seizure is particularly challenging, and the contribution of cerebrospinal fluid (CSF) analysis is not fully understood.

Methods

In this retrospective study with a mean of 7.8 years follow-up involving 39 well-characterized patients with the initial diagnosis of new-onset seizure or epilepsy of unknown etiology and 24 controls, we determined the frequency of autoantibodies to brain proteins in CSF/serum pairs using cell-based assays and unbiased immunofluorescence staining of unfixed murine brain sections.

Results

Autoantibodies were detected in the CSF of 30.8% of patients. Underlying antigens involved glial fibrillary acidic protein (GFAP) and N-methyl-D-aspartate (NMDA) receptors, but also a range of yet undetermined epitopes on neurons, glial and vascular cells. While antibody-positive patients had higher frequencies of cancer, they did not differ from antibody-negative patients with respect to seizure type, electroencephalography (EEG) and cranial magnetic resonance imaging (cMRI) findings, neuropsychiatric comorbidities or pre-existing autoimmune diseases. In 5.1% of patients with seizures or epilepsy of initially presumed unknown etiology, mostly CSF findings resulted in etiological reallocation as autoimmune-associated epilepy.

Discussion

These findings strengthen the potential role for routine CSF analysis. Further studies are needed to understand the autoantibody contribution to etiologically unclear epilepsies, including determining the antigenic targets of underlying autoantibodies.

Temporal lobe epilepsy with GAD antibodies: neurons killed by T cells not by complement membrane attack complex

Temporal lobe epilepsy (TLE) is one of the syndromes linked to antibodies against glutamic acid decarboxylase (GAD). It has been questioned whether 'limbic encephalitis with GAD antibodies' is a meaningful diagnostic entity. The immunopathogenesis of GAD-TLE has remained enigmatic. Improvement of immunological treatability is an urgent clinical concern. We retrospectively assessed the clinical, MRI and CSF course as well as brain tissue of 15 adult patients with GAD-TLE who underwent temporal lobe surgery. Brain tissue was studied by means of immunohistochemistry, multiplex fluorescent microscopy and transcriptomic analysis for inflammatory mediators and neuronal degeneration. In 10 patients, there was a period of mediotemporal swelling and T2 signal increase; in nine cases this occurred within the first 6 years after symptom onset. This resulted in unilateral or bilateral hippocampal sclerosis; three cases developed hippocampal sclerosis within the first 2 years. All CSF studies done within the first year (n = 6) revealed intrathecal synthesis of immunoglobulin G. Temporal lobe surgeries were done after a median disease duration of 9 years (range 3 weeks to 60 years). Only two patients became seizure-free. Brain parenchyma collected during surgery in the first 6 years revealed high numbers of plasma cells but no signs of antibody-mediated tissue damage. Even more dense was the infiltration by CD8+ cytotoxic T lymphocytes (CTLs) that were seen to locally proliferate. Further, a portion of these cells revealed an antigen-specific resident memory T cell phenotype. Finally, CTLs with cytotoxic granzyme B+ granules were also seen in microglial nodules and attached to neurons, suggesting a CTL-mediated destruction of these cells. With longer disease duration, the density of all lymphocytes decreased. Whole transcriptome analysis in early/active cases (but not in late/inactive stages) revealed 'T cell immunity' and 'Regulation of immune processes' as the largest overrepresented clusters. To a lesser extent, pathways associated with B cells and neuronal degeneration also showed increased representation. Surgically treated patients with GAD-TLE go through an early active inflammatory, 'encephalitic' stage (≤6 years) with CTL-mediated, antigen-driven neuronal loss and antibody-producing plasma cells but without signs of complement-mediated cell death. Subsequently, patients enter an apparently immunologically inactive or low-active stage with ongoing seizures, probably caused by the structural damage to the temporal lobe. 'Limbic encephalitis' with GAD antibodies should be subsumed under GAD-TLE. The early tissue damage explains why immunotherapy does not usually lead to freedom from seizures.

A Case of Anti-GAD 65 Autoimmune Encephalitis Associated with Focal Segmental Stiff-Person Syndrome

Glutamic acid decarboxylase (GAD) antibody-related encephalitis is an autoimmune disease associated with intracellular neuronal antigens. We report on a rare case of GAD antibody-associated encephalitis complicated with focal segmental stiffness-person syndrome (SPS) in a middle-aged woman. The disease course lasted for >10 years, initially presenting with drug-resistant epilepsy, followed by stiffness of the right lower limb, and right upper limb involvement. The patient experienced anxiety and depression symptoms due to long-term illness. During hospitalization, serum and cerebrospinal fluid GAD antibodies were positive and no tumor was found. The symptoms were significantly relieved after corticosteroid therapy and intravenous immunoglobulin immunomodulation therapy. To the best of our knowledge, this case is the first to discuss the early recognition and treatment of chronic epilepsy and focal segmental SPS caused by anti-GAD antibody-related encephalitis.

Glutamic acid decarboxylase antibody-associated neurological syndromes: Clinical and antibody characteristics and therapy response

BACKGROUND

Antibodies against glutamic acid decarboxylase (GAD-abs) at high serum levels are associated with diverse autoimmune neurological syndromes (AINS), including cerebellar ataxia, epilepsy, limbic encephalitis and stiff-person syndrome. The impact of low serum GAD-ab levels in patients with suspected AINS remains controversial. Specific intrathecal GAD-ab synthesis may serve as a marker for GAD-ab-associated nervous system autoimmunity. We present characteristics of a multicentric patient cohort with suspected AINS associated with GAD antibodies (SAINS-GAD+) and explore the relevance of serum GAD-ab levels and intrathecal GAD-ab synthesis.

METHODS

All patients with SAINS-GAD+ included in the registry of the German Network for Research on Autoimmune Encephalitis (GENERATE) from 2011 to 2019 were analyzed. High serum GAD-ab levels were defined as RIA>2000 U/mL, ELISA>1000 U/mL, or as a positive staining pattern on cell-based assays.

RESULTS

One-hundred-one patients were analyzed. In descending order they presented with epilepsy/limbic encephalitis (39%), cerebellar ataxia (28%), stiff person syndrome (22%), and overlap syndrome (12%). Immunotherapy was administered in 89% of cases with improvements in 46%. 35% of SAINS-GAD+ patients had low GAD-ab serum levels. Notably, unmatched oligoclonal bands in CSF but not in serum were more frequent in patients with low GAD-ab serum levels. GAD-ab-levels (high/low) and intrathecal GAD-ab synthesis (present or not) did not impact clinical characteristics and outcome.

CONCLUSIONS

Overall, immunotherapy in SAINS-GAD+ was moderately effective. Serum GAD-ab levels and the absence or presence of intrathecal GAD-ab synthesis did not predict clinical characteristics or outcomes in SAINS-GAD+. The detection of unmatched oligoclonal bands might outweigh low GAD-ab serum levels.

Elevated IL-6 plasma levels are associated with GAD antibodies-associated autoimmune epilepsy

Background

Antibodies against glutamic acid decarboxylase (GADA) are present in multiple neurological manifestations, such as stiff-person syndrome, cerebellar ataxia, limbic encephalitis, and epilepsy. Increasing data support the clinical significance of GADA as an autoimmune etiology of epilepsy, however, there is not yet definitive evidence to confirm the pathogenic link between GADA and epilepsy.

Objective

Interleukin-6 (IL-6), a pro-convulsive and neurotoxic cytokine, and interleukin-10 (IL-10), an anti-inflammatory and neuroprotective cytokine, are crucial inflammatory mediators in the brain. Increased production of IL-6 and its association with epileptic disease profiles are well established, suggesting the presence of chronic systemic inflammation in epilepsy. Therefore, in this study, we investigated the association of plasma cytokine concentrations of IL-6 and IL-10 and their ratio with GADA in patients with drug-resistant epilepsy.

Methods

Interleukin-6 and IL-10 concentrations were measured by ELISA in plasma, and the IL-6/IL-10 ratio was calculated in a cross-sectional cohort of 247 patients with epilepsy who had their GADA titers measured previously for their clinical significance in epilepsy. Based on GADA titers, patients were grouped as GADA negative (n = 238), GADA low positive (antibody titers < 1,000 RU/mL, n = 5), and GADA high positive (antibody titers ≥ 1,000 RU/mL, n = 4).

Results

Median IL-6 concentrations were significantly higher in patients with high GADA positivity [2.86 pg/mL, interquartile range (IQR) = 1.90-5.34 pg/mL] than in GADA-negative patients [1.18 pg/mL, interquartile range (IQR) = 0.54-2.32 pg/mL; p = 0.039]. Similarly, IL-10 concentrations were also higher in GADA high-positive patients [1.45 pg/mL, interquartile range (IQR) = 0.53-14.32 pg/mL] than in GADA-negative patients [0.50 pg/mL, interquartile range (IQR) = 0.24-1.00 pg/mL], however, the difference was not statistically significant (p = 0.110). Neither IL-6 nor IL-10 concentrations were different between GADA-negative and GADA low-positive patients (p > 0.05) or between GADA low-positive or GADA high-positive patients (p > 0.05). The IL-6/IL-10 ratio was also similar among all the study groups.

Conclusion

Increased circulatory concentrations of IL-6 are associated with high GADA titers in patients with epilepsy. These data provide additional pathophysiological significance of IL-6 and help to further describe the immune mechanisms involved in the pathogenesis of GADA-associated autoimmune epilepsy.

Seizure Semiology in Antibody-Associated Autoimmune Encephalitis

BACKGROUND AND OBJECTIVES

To assess seizure characteristics in antibody (ab)-associated autoimmune encephalitis (ab + AE) with the 3 most prevalent abs against N-methyl-d-aspartate receptor (NMDAR), leucine-rich glioma-inactivated protein 1 (LGI1), and glutamic acid decarboxylase (GAD).

METHODS

Multicenter nationwide prospective cohort study of the German Network for Research in Autoimmune Encephalitis.

RESULTS

Three hundred twenty patients with ab + AE were eligible for analysis: 190 NMDAR+, 89 LGI1+, and 41 GAD+. Seizures were present in 113 (60%) NMDAR+, 69 (78%) LGI1+, and 26 (65%) GAD+ patients and as leading symptoms for diagnosis in 53 (28%) NMDAR+, 47 (53%) LGI+, and 20 (49%) GAD+ patients. Bilateral tonic-clonic seizures occurred with almost equal frequency in NMDAR+ (38/51, 75%) and GAD+ (14/20, 70%) patients, while being less common in LGI1+ patients (27/59, 46%). Focal seizures occurred less frequently in NMDAR+ (67/113; 59%) than in LGI1+ (54/69, 78%) or in GAD+ patients (23/26; 88%). An aura with déjà-vu phenomenon was nearly specific in GAD+ patients (16/20, 80%). Faciobrachial dystonic seizures (FBDS) were uniquely observed in LGI1+ patients (17/59, 29%). Status epilepticus was reported in one-third of NMDAR+ patients, but only rarely in the 2 other groups. The occurrence of seizures was associated with higher disease severity only in NMDAR+ patients.

DISCUSSION

Seizures are a frequent and diagnostically relevant symptom of ab + AE. Whereas NMDAR+ patients had few localizing semiological features, semiology in LGI1+ and GAD+ patients pointed toward a predominant temporal seizure onset. FBDS are pathognomonic for LGI1 + AE. Status epilepticus seems to be more frequent in NMDAR + AE.

Autoimmune-Associated Seizures

PURPOSE OF REVIEW

This article focuses on the seizure manifestations and presentations of autoimmune-associated epilepsy and acute symptomatic seizures in autoimmune encephalitis. It discusses the specificity of the various central nervous system autoantibodies and clarifies when their presence can be considered indicative of an immune etiology. Finally, current recommendations regarding patient selection for autoimmune antibody evaluation are reviewed, and an approach to immunotherapy is provided.

RECENT FINDINGS

Although autoimmune seizures are caused by a heterogeneous group of autoantibodies, key features reported in the literature should alert clinicians to the possible diagnosis. In particular, seizure characteristics including frequency, timing, duration, and symptomatology can provide vital clues to help differentiate autoimmune-associated seizures from other causes of epilepsy. Diagnostic certainty also requires an understanding and integration of the spectrum of clinical and paraclinical presentations, and several scoring systems have been developed that may be useful to aid the identification of autoimmune seizures.

SUMMARY

Seizures due to autoimmune etiology are increasingly encountered in clinical practice. It is critical that clinicians recognize immune seizure etiologies early in their course given they are often responsive to immunotherapy but are usually resistant to antiseizure medications. Currently, however, it is unfortunately not uncommon for autoimmune-associated seizure disorders to remain undiagnosed, resulting in missed opportunities to administer effective therapies. Efforts to better understand autoimmune seizure manifestations and treatment strategies are ongoing.

Discerning the Role of Autoimmunity and Autoantibodies in Epilepsy: A Review

Importance

The literature on neural autoantibody positivity in epilepsy has expanded over the last decade, with an increased interest among clinicians in identifying potentially treatable causes of otherwise refractory seizures.

Observations

Prior studies have reported a wide range of neural autoantibody positivity rates among various epilepsy populations, with the highest frequency reported in individuals with focal epilepsy of unknown cause and new-onset seizures. The antibodies in some cases are of uncertain significance, and their presence can cause conundrums regarding therapy.

Conclusions and Relevance

There is likely some role for neural autoantibody assessment in patients with unexplained epilepsy who lack clear evidence of autoimmune encephalitis, but the clinical implications of such testing remain unclear owing to limitations in previous published studies. A framework for study design to bridge the current gaps in knowledge on autoimmune-associated epilepsy is proposed.

Prevalence of Neural Autoantibodies in Epilepsy of Unknown Etiology: Systematic Review and Meta-Analysis

BACKGROUND

The prevalence of neural autoantibodies in epilepsy of unknown etiology varies among studies. We aimed to conduct a systematic review and meta-analysis to determine the pooled global prevalence and the prevalence for each antibody.

METHODS

A systematic search was conducted for studies that included prospectively patients ≥16 years old with epilepsy of unknown etiology and systematically determined neural autoantibodies. A meta-analysis was undertaken to estimate pooled prevalence in total patients with a positive result for at least one neural autoantibody in serum and/or cerebrospinal fluid (CSF) and for each autoantibody.

RESULTS

Ten of the eleven studies that met the inclusion criteria and a total of 1302 patients with epilepsy of unknown etiology were included in themeta-analysis. The global pooled prevalence (IC95%) was 7.6% (4.6-11.2) in a total of 82 patients with a positive result for any neural autoantibody. None of the controls available in the studies had a positive result. Individual pooled prevalence for each autoantibody was: glycine receptor (GlyR) (3.2%), glutamic acid decarboxylase (GAD) (1.9%), N-methyl-d-aspartate receptor (NMDAR) (1.8%), leucine-rich glioma inactivated-1 protein (LGI1) (1.1%), contactin-2-associated protein (CASPR2) (0.6%) and onconeuronal (0.2%).

CONCLUSIONS

The pooled prevalence of neural autoantibodies in patients with epilepsy of unknown etiology is small but not irrelevant. None of the controls had a positive result. There was high heterogeneity among studies. In the future, a homogeneous protocol for testing neural autoantibodies is recommended.

Rare presentation of anti-GAD-65 antibody-positive autoimmune encephalitis and simultaneous onset of type 1 diabetes mellitus in a paediatric patient

A 16-year-old female patient presented with subacute onset of headaches, changes in acute mental status, expressive aphasia and auditory hallucinations. New oedema and enhancement of the temporal lobe were seen on brain MRI, with correlating subclinical seizures seen on electroencephalogram. Simultaneously, our patient was diagnosed with new-onset type 1 diabetes mellitus, with positive anti-glutamic acid decarboxylase (anti-GAD-65) antibodies in the serum. Cerebrospinal fluid studies remained negative, including anti-GAD-65 antibodies. Clinical remission was achieved with corticosteroids and intravenous immunoglobulins.

Clinical spectrum of high-titre GAD65 antibodies

OBJECTIVE

To determine clinical manifestations, immunotherapy responsiveness and outcomes of glutamic acid decarboxylase-65 (GAD65) neurological autoimmunity.

METHODS

We identified 323 Mayo Clinic patients with high-titre (>20 nmol/L in serum) GAD65 antibodies out of 380 514 submitted anti-GAD65 samples (2003-2018). Patients classified as having GAD65 neurological autoimmunity after chart review were analysed to determine disease manifestations, immunotherapy responsiveness and predictors of poor outcome (modified Rankin score >2).

RESULTS

On review, 108 patients were classified as not having GAD65 neurological autoimmunity and 3 patients had no more likely alternative diagnoses but atypical presentations (hyperkinetic movement disorders). Of remaining 212 patients with GAD65 neurological autoimmunity, median age at symptom onset was 46 years (range: 5-83 years); 163/212 (77%) were female. Stiff-person spectrum disorders (SPSD) (N=71), cerebellar ataxia (N=55), epilepsy (N=35) and limbic encephalitis (N=7) could occur either in isolation or as part of an overlap syndrome (N=44), and were designated core manifestations. Cognitive impairment (N=38), myelopathy (N=23) and brainstem dysfunction (N=22) were only reported as co-occurring phenomena, and were designated secondary manifestations. Sustained response to immunotherapy ranged from 5/20 (25%) in epilepsy to 32/44 (73%) in SPSD (p=0.002). Complete immunotherapy response occurred in 2/142 (1%). Cerebellar ataxia and serum GAD65 antibody titre >500 nmol/L predicted poor outcome.

INTERPRETATION

High-titre GAD65 antibodies were suggestive of, but not pathognomonic for GAD65 neurological autoimmunity, which has discrete core and secondary manifestations. SPSD was most likely to respond to immunotherapy, while epilepsy was least immunotherapy responsive. Complete immunotherapy response was rare. Serum GAD65 antibody titre >500 nmol/L and cerebellar ataxia predicted poor outcome.

Severe Chin-on-Chest Cervical Spine Deformity in the Setting of Stiff-Person Syndrome: A Case Report

CASE

Stiff-person syndrome (SPS) presents with progressive muscle rigidity, postural instability, and periodic debilitating spasms. Reports of axial hyperextension exist, but kyphotic deformities have not been described. We surgically treated a patient with debilitating SPS and severe cervicothoracic hyperkyphosis with posterior spinal fusion and instrumentation. At 1-year follow-up, the patient displayed better upright gait and forward gaze, 18° cervical lordosis, and improved patient-reported outcome scores.

CONCLUSION

SPS can lead to extreme spinal deformity and disease, including hyperkyphosis of the cervicothoracic spine, and can successfully be managed with a multidisciplinary team and a posterior-only correction with spinal instrumentation and fusion.

Adult-onset temporal lobe epilepsy suspicious for autoimmune pathogenesis: Autoantibody prevalence and clinical correlates

Temporal lobe adult-onset seizures (TAOS) related to autoimmunity represent an increasingly recognized disease syndrome within the spectrum of epilepsies. In this context, certain autoantibodies (autoABs) were often associated with limbic encephalitis (LE). Here, we aimed to gain insights into (a) the distribution of ‘neurological’ autoABs (neuroABs, defined as autoABs targeting neuronal surface structures or ‘onconeuronal’ ABs or anti-glutamate acid decarboxylase 65 (GAD65) autoABs) in a large consecutive TAOS patient cohort, to characterize (b) clinical profiles of seropositive versus seronegative individuals and to find (c) potential evidence for other autoABs. Blood sera/cerebrospinal fluid (CSF) of TAOS patients (n = 800) and healthy donors (n = 27) were analyzed for neuroABs and screened for other autoABs by indirect immunofluorescence on hippocampal/cerebellar sections and immunoblots of whole brain and synaptosome lysates. Serological results were correlated with clinico-neuropsychological features. 13% of TAOS patients (n = 105) were neuroAB⁺, with anti-GAD65 and anti-N-methyl-D-aspartate receptors (NMDAR) as most frequent autoABs in this group. In our screening tests 25% of neuroAB^- patients (n = 199) were positive (screening⁺), whereas all control samples were negative (n = 27). Intriguingly, key clinico-neuropsychological characteristics including magnetic resonance imaging (MRI) findings, epileptiform electroencephalographic (EEG) activity, and inflammatory cellular infiltrates in CSF were shared to a greater extent by neuroAB⁺ with neuroAB^-/screening⁺ patients than with neuroAB^-/screening^- patients. Serological testing in a large consecutive TAOS patient series revealed seropositivity for anti-GAD65 autoABs as the most frequent neuroAB. Intriguingly, neuroAB⁺ individuals were virtually indistinguishable from neuroAB^-/screening⁺ patients in several major clinical features. In contrast, neuroAB^-/screening^- TAOS patients differed in many parameters. These data support the potential presence of so far unrecognized autoABs in patients with TAOS.

Paraclinical serum markers as aids in the diagnosis of autoimmune encephalitis

Expert opinion suggests the presence ANA and thyroid antibodies may be helpful to diagnosis autoimmune encephalitis (AE). This study investigates the sensitivity of these serum markers in a cohort of 26 patients with AE. TPO-Ab, TG-Ab and ANA (titer ≥1:320) were present in 45%, 35% and 32% of patients tested, respectively. The prevalence of TPO-Ab (11.3%), TG-Ab (10.4%) and ANA ≥1:320 (3.3%) has been previously reported in disease-free populations. Although these antibodies represent non-specific markers of autoimmunity, this study demonstrated that TPO-Ab, TG-Ab and ANA were significantly elevated in AE compared to disease-free populations (p < .001, p = .003, p < .001, respectively).

How Much GAD65 Do You Have? High Levels of GAD65 Antibodies in Autoimmune Encephalitis

Neurologic Syndromes Related to Anti-GAD65 Clinical and Serologic Response to Treatment

Muñoz-Lopetegi A, de Bruijn MAAM, Boukhrissi S, Bastiaansen AEM, Nagtzaam MMP, Hulsenboom ESP, Boon AJW, Neuteboom RF, de Vries JM, Sillevis Smitt PAE, Schreurs MWJ, Titulaer MJ. Neurol Neuroimmunol Neuroinflamm. 2020;7(3):e696. doi:10.1212/NXI.0000000000000696

Objective:

Antibodies against glutamic acid decarboxylase 65 (anti-GAD65) are associated with a number of neurologic syndromes. However, their pathogenic role is controversial. Our objective was to describe clinical and paraclinical characteristics of anti-GAD65 patients and analyze their response to immunotherapy.

Methods:

Retrospectively, we studied patients (n = 56) with positive anti-GAD65 and any neurologic symptom. We tested serum and cerebrospinal fluid with enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and cell-based assay. Accordingly, we set a cutoff value of 10 000 IU/mL in serum by ELISA to group patients into high-concentration (n = 36) and low-concentration (n = 20) groups. We compared clinical and immunologic features and analyzed response to immunotherapy.

Results:

Classical anti–GAD65-associated syndromes were seen in 34 of 36 patients with high concentration (94%): stiff-person syndrome (7), cerebellar ataxia (3), chronic epilepsy (9), limbic encephalitis (9), or an overlap of 2 or more of the former (6). Patients with low concentrations had a broad, heterogeneous symptom spectrum. Immunotherapy was effective in 19 of 27 treated patients (70%), although none of them completely recovered. Antibody concentration reduction occurred in 15 of 17 patients with available pre- and posttreatment samples (median reduction 69%; range 27%-99%), of which 14 improved clinically. The 2 patients with unchanged concentrations showed no clinical improvement. No differences in treatment responses were observed between specific syndromes.

Conclusion:

Most patients with high anti-GAD65 concentrations (>10 000 IU/mL) showed some improvement after immunotherapy, unfortunately without complete recovery. Serum antibody concentrations’ course might be useful to monitor response. In patients with low anti-GAD65 concentrations, especially in those without typical clinical phenotypes, diagnostic alternatives are more likely.

Post-infectious neurological disorders

A multitude of environmental factors can result in breakdown of immune tolerance in susceptible hosts. Infectious pathogens are among the most important environmental triggers in the pathogenesis of autoimmunity. Certain autoimmune disorders have a strong association with specific infections. Several neurological autoimmune disorders are thought to occur through post-infectious mechanisms. In this review, we discuss the proposed mechanisms underlying pathogen-induced autoimmunity, and highlight the clinical presentation and treatment of several post-infectious autoimmune neurological disorders. We also highlight post-infectious neurological disorders in the setting of recent outbreaks.

Low rate of glutamic acid decarboxylase 65 (GAD-65) antibodies in chronic epilepsy

PURPOSE

Autoantibodies against glutamic acid decarboxylase 65 (GAD-65) have been identified in patients with chronic epilepsy. In this study, we ask (1) what is the frequency of GAD-65 antibodies in chronic epilepsy? (2) what is the frequency and type of epilepsy in individuals with GAD-65 antibodies?

METHODS

For cohort 1, serum samples of patients with epilepsy (without type I diabetes) were obtained from our biobank. Samples were tested for GAD-65 antibodies using a cell-based assay and confirmed by immunohistochemistry. For cohort 2, patients with positive GAD-65 antibodies were identified and their medical records were reviewed for the presence and characteristics of epilepsy.

RESULTS

Cohort 1 included 270 patients, of which 53% were women; median age was 47 years; median duration of epilepsy was 16 years. Epilepsy was focal in 87% (temporal lobe in 20%), and drug-resistant in 45%. GAD-65 antibodies were present in two out of 270 cases (0.7%) and zero controls. Cohort 2 consisted of 23 patients with known GAD-65 antibodies, of which ten had epilepsy (43%). Of these, 80% were women with a median age of 40 years and a median duration of epilepsy of 18 years. All ten patients had focal epilepsy, nine had temporal lobe epilepsy, and seven were drug resistant.

CONCLUSIONS

In patients with chronic epilepsy, the frequency of GAD-65 antibodies detected with our cell-based assay was substantially lower than previously reported with use of other methods. When present, GAD-65 antibodies are associated with drug-resistant temporal lobe epilepsy. GAD-65 positive epilepsy patients merit further investigation.

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.

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.

Brain-responsive neurostimulation treatment in patients with GAD65 antibody-associated autoimmune mesial temporal lobe epilepsy

Glutamic acid decarboxylase 65‐kilodalton isoform (GAD65) antibodies have been associated with multiple nonneurological and neurological syndromes including autoimmune epilepsy (AE). Although immunotherapy remains the cornerstone for the treatment of AE, those with GAD65 Ab‐associated AE (GAD65‐AE) remain refractory to immunotherapy and antiseizure medication (ASM). Outcomes of epilepsy surgery in this patient population have also been unsatisfactory. The role of neuromodulation therapy, particularly direct brain‐responsive neurostimulation therapy, has not been previously examined in GAD65‐AE. Here, we describe four consecutive patients with refractory GAD‐65‐associated temporal lobe epilepsy (GAD65‐TLE) receiving bilateral hippocampal RNS System treatment. The RNS System treatment was well tolerated and effective in this study cohort. Three patients had a >50% clinical seizure reduction, and one patient became clinically seizure‐free following resective surgery informed by the RNS System data with continued RNS System treatment. In all four of our patients, the long‐term ambulatory data provided by the RNS System allowed us to gain objective insights on electrographic seizure lateralization, patterns, and burden as well as guided immunotherapy and ASM optimization. Our results suggest the potential utility of the RNS System in the management of ASM intractable GAD65‐AE.

Routine diagnostics for neural antibodies, clinical correlates, treatment and functional outcome

Objective

To determine frequencies, interlaboratory reproducibility, clinical ratings, and prognostic implications of neural antibodies in a routine laboratory setting in patients with suspected neuropsychiatric autoimmune conditions.

Methods

Earliest available samples from 10,919 patients were tested for a broad panel of neural antibodies. Sera that reacted with leucine-rich glioma-inactivated protein 1 (LGI1), contactin-associated protein-2 (CASPR2), or the voltage-gated potassium channel (VGKC) complex were retested for LGI1 and CASPR2 antibodies by another laboratory. Physicians in charge of patients with positive antibody results retrospectively reported on clinical, treatment, and outcome parameters.

Results

Positive results were obtained for 576 patients (5.3%). Median disease duration was 6 months (interquartile range 0.6–46 months). In most patients, antibodies were detected both in CSF and serum. However, in 16 (28%) patients with N-methyl-d-aspartate receptor (NMDAR) antibodies, this diagnosis could be made only in cerebrospinal fluid (CSF). The two laboratories agreed largely on LGI1 and CASPR2 antibody diagnoses (κ = 0.95). The clinicians (413 responses, 71.7%) rated two-thirds of the antibody-positive patients as autoimmune. Antibodies against the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), NMDAR (CSF or high serum titer), γ-aminobutyric acid-B receptor (GABABR), and LGI1 had ≥ 90% positive ratings, whereas antibodies against the glycine receptor, VGKC complex, or otherwise unspecified neuropil had ≤ 40% positive ratings. Of the patients with surface antibodies, 64% improved after ≥ 3 months, mostly with ≥ 1 immunotherapy intervention.

Conclusions

This novel approach starting from routine diagnostics in a dedicated laboratory provides reliable and useful results with therapeutic implications. Counseling should consider clinical presentation, demographic features, and antibody titers of the individual patient.

Electronic supplementary material

The online version of this article (10.1007/s00415-020-09814-3) contains supplementary material, which is available to authorized users.

Long-term outcomes in temporal lobe epilepsy with glutamate decarboxylase antibodies

OBJECTIVE

To assess the long-term outcomes of patients with temporal lobe epilepsy and CSF anti-glutamate decarboxylase antibodies (GAD65-Abs).

METHODS

We retrospectively analyzed the clinical records of 35 patients with temporal lobe epilepsy and CSF GAD65-Abs, collected from January 1993 to December 2016 and assessed cognitive impairment and seizure activity at last visit. Cognitive impairment was considered significant if impacting on daily life activities. Immunohistochemistry on rat brain slices and ELISA were used for antibody detection and titration.

RESULTS

Median age was 30 years (range 2-63), 32/35 (91%) patients were female, and median follow-up was 68 months (range 7-232). At presentation, 20 patients had isolated temporal lobe epilepsy and 15 patients had other limbic symptoms, including anterograde amnesia (n = 10) and behavioral disturbances (n = 5). Progressive clinical deterioration over follow-up was reported in 28/35 patients (80%), including gradual increase of memory impairment (n = 25), and apparition of behavioral disturbances (n = 4) or mood disorders (n = 18). At last follow-up, 24/35 (69%) patients had cognitive disturbances with an impact on patient's daily life activities, and 28/35 (80%) still had active seizures.

CONCLUSION

Most patients with temporal lobe epilepsy and CSF GAD65-Abs develop a chronic disease with progressive cognitive impairment and refractory epilepsy regardless of the presence of additional limbic symptoms at onset.

Predisposing factors and prognosis of status epilepticus in patients with autoimmune encephalitis

The aim of this study was to study the predisposing factors and prognosis of status epilepticus (SE) in patients with autoimmune encephalitis (AE).A total of 227 cases of AE were collected from the inpatient department of West China Hospital of Sichuan University from January 2010 to May 2018. All patients met the 2015 criteria for the diagnosis of AE. The binary logistic regression model was used to multivariate and retrospective chart analysis the predisposition factors for SE and its prognostic factors.Of the 227 patients with AE, 50 (22.03%) had SE during hospitalization, and 19 patients with SE had a poor prognosis (modified Rankin score MRS = 3-6), and 7 patients with no SE had a poor prognosis. In the logistic regression model, electroencephalograms (EEGs) abnormalities (P = .000) and head magnetic resonance imaging (MRI) abnormalities (P = .003) were associated with a predisposition to SE, while Glasgow scores <8 (P = .027), abnormal EEG (P = .046), delayed immunotherapy (P = .012), and SE duration at admission lasting >30 minutes (P = .023) were risk factors for a poor prognosis of SE.SE is a common complication in patients with AE. EEG and MRI abnormalities may be predisposing factors for SE. Glasgow scores <8 points, abnormal EEG, delayed immunotherapy, and SE duration lasting >30 minutes at admission are risk factors for a poor prognosis in patients with SE.

Cerebellar Ataxia Followed by Stiff Person Syndrome in a Patient with Anti-GAD Antibodies

Anti-GAD antibody syndrome is a result of the production of antibodies against glutamic acid decarboxylase (GAD), the main enzyme responsible for the production of gamma-aminobutyric acid (GABA). Several neurological manifestations including cerebellar ataxia and stiff person syndrome have been reported in association with anti-GAD antibodies. In this paper, we present a case of a young woman with anti-GAD antibodies who initially presented with cerebellar ataxia followed by stiff person syndrome three and a half years later. Having both cerebellar ataxia and stiff person syndrome is a rare occurrence in anti-GAD antibody syndrome. We emphasise the importance of long-term follow-up of patients with anti-GAD antibody syndrome, as delayed neurological manifestations can occur.

Overrepresentation of epilepsy in children with type 1 diabetes is declining in a longitudinal population study in Finland

AIM

The aim was to determine temporal changes in increased risk of epilepsy among children with type 1 diabetes.

METHODS

The incidence of epilepsy up to age 15 in children with prior type 1 diabetes was analysed regarding the general Finnish child population using data from the Finnish nationwide hospital register. Type 1 diabetes and epilepsy were identified by the International Classification of Diseases 9th and 10th revision codes. Epilepsy was defined according to ILAE guidelines. The analyses were done using negative binomial regression models.

RESULTS

Preceding type 1 diabetes was diagnosed in 6162 (0.91%) of the 679 375 general children population. Incidence rate of new-onset epilepsy among children with type 1 diabetes was higher than in controls (140 vs 82 per 100 000 person-years at risk, respectively). The excess incidence diminished with time (P = 0.033 for diabetes to birth cohort interaction), from over twofold in birth cohort 1990-1993 [incidence rate ratio 2.2 (95% CI 1.7-2.9)] to 40% in birth cohort 1998-2000 [1.4 (95% CI 1.001-1.9)].

CONCLUSION

In a population study setting, children with type 1 diabetes had an increased, but slowly declining risk of developing epilepsy. Future research may elucidate the underlying mechanisms.

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.

SPS: Understanding the complexity

INTRODUCTION

Stiff-person syndrome (SPS), first described in 1956 by Moersch and Woltman, is a progressive autoimmune disorder with core features of chronic fluctuating progressive truncal and limb rigidity and painful muscle spasms leading to gait difficulties, falls and an appearance that resembles tin soldiers. The syndrome is a rare, highly disabling disorder of the central nervous and frequently results in significant disability. Understanding of the etiology, clinical spectrum, diagnostic workup and therapeutic modalities for this painful and disabling disorder has vastly evolved over the past few years with more confidence in classifying and treating the patients. The purpose of this review is to increase the awareness, early detection, and treatment of this disabling disease.

METHOD

PubMed was searched, all date inclusive, using the following phrases: stiff person syndrome,anti-Glutamic acid decarboxylase (Anti-GAD) antibody syndrome, Progressive encephalomyelitis with rigidity and myoclonus (PERM), and Paraneoplastic Stiff Person syndrome. No filters or restrictions were used. A total of 888 articles were identified.

RESULTS

The results were narrowed to 190 citations after excluding non-English and duplicate reports. Clinical presentation, laboratory testing, treatment, and prognosis were categorized and summarized.

DISCUSSION

In this article we will discuss the epidemiology, presentation and classification. Explain the pathophysiology of SPS and the autoimmune mechanisms involved. Discuss the diagnostic approach and treatments available, as well as, the prognosis and outcome.

Autoimmune Epilepsy

The field of autoimmune epilepsy has evolved substantially in the last few decades with discovery of several neural autoantibodies and improved mechanistic understanding of these immune-mediated syndromes. A considerable proportion of patients with epilepsy of unknown etiology have been demonstrated to have an autoimmune cause. The majority of the patients with autoimmune epilepsy usually present with new-onset refractory seizures along with subacute progressive cognitive decline and behavioral or psychiatric dysfunction. Neural specific antibodies commonly associated with autoimmune epilepsy include leucine-rich glioma-inactivated protein 1 (LGI1), N-methyl-D-aspartate receptor (NMDA-R), and glutamic acid decarboxylase 65 (GAD65) IgG. Diagnosis of these cases depends on the identification of the clinical syndrome and ancillary studies including autoantibody evaluation. Predictive models (Antibody Prevalence in Epilepsy and Encephalopathy [APE2] and Response to Immunotherapy in Epilepsy and Encephalopathy [RITE2] scores) based on clinical features and initial neurological assessment may be utilized for selection of cases for autoimmune epilepsy evaluation and management. In this article, we will review the recent advances in autoimmune epilepsy and provide diagnostic and therapeutic algorithms for epilepsies with suspected autoimmune etiology.

Analysis of Relation Between Electroclinical Features and Cerebrospinal Fluid Antibody Titers in Patients With anti-NMDAR Encephalitis

PURPOSE

This study aimed to determine the relation between electroclinical features and cerebrospinal fluid (CSF) antibody titers in patients with anti- N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis.

METHOD

Clinical symptoms and electroencephalography (EEG) at different stages were analyzed in 51 hospitalized patients with anti-NMDAR encephalitis.

RESULTS

Behavioral changes were the initial symptoms in 90.9% (20/22) of female patients with high (1:10 or 1:32) CSF antibody titers. A greater number of clinical symptoms were observed in the patients with high CSF antibody titers than in those with low (1:1 or 1:3.2) CSF antibody titers (mean 3.11 ± 1.06 vs 1.62 ± 0.65, P = .000). The number of clinical symptoms was greater in the female patients than in the male patients (mean 3.52 ± 0.98 vs 2.69 ± 1.09, P = .000). At the peak stage, worse background activity (BA) in EEG recordings was observed in patients with high CSF antibody titers than in those with low CSF antibody titers (Mann-Whitney U test, P = .001). The peak-stage BA in EEG was worse in female patients than in male patients (Mann-Whitney U test, P = .000). Modified Rankin scale scores were higher in patients with high CSF antibody titers than in those with low CSF antibody titers (mean 2.62 ± 1.42 vs 0.75 ± 0.97, P = .000). Brush patterns and constant chewing were observed primarily in female patients with high CSF antibody titers. Epileptic discharges were located predominately in the frontal regions and were noted to vary.

CONCLUSION

The electroclinical features of patients with anti-NMDAR encephalitis were associated with gender and CSF antibody titers.

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.

Mesial temporal lobe epilepsy with hippocampal sclerosis is infrequently associated with neuronal autoantibodies

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is characterized by its well-defined clinical profile. Limbic encephalitis is increasingly recognized as a possible etiology of adult-onset MTLE-HS, and neuronal autoantibodies have been detected in patients even without previous signs of encephalitis. The aim of this study is to analyze the frequency of specific autoantibodies in patients with MTLE-HS. A case-control study was carried out with 100 patients with MTLE-HS and 50 healthy controls. Sera samples from subjects were tested by indirect immunofluorescence assay for detection of anti-N-methyl-d-aspartate receptor (NMDA-R), anti-contactin-associated protein-like 2 (CASPR2), anti-leucine-rich glioma inactivated 1 (LGI1), anti-gamma aminobutyric acid B receptor (GABA-B-R), anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid 1 and 2 receptors (AMPA-1-R and AMPA-2-R), and enzyme-linked immunosorbent assay for detection of anti-glutamic acid decarboxylase 65 (GAD65). Mean age of patients and controls was 41.2 vs 42 years, and 55% vs 56% were female. Mean duration of epilepsy was 27.2 years. No neuronal autoantibodies were found in either group, except for anti-GAD65 in 3 patients and 2 controls. This study adds to the mounting evidence that, in Brazilian patients, MTLE-HS without signs and symptoms of autoimmune encephalitis may be infrequently associated with these autoantibodies. Differences regarding accuracy of used methodologies for autoantibody detection and genetic and environmental characteristics are discussed. Further works with different methodologies tested simultaneously in different populations may help clarify the incongruent study results about autoantibodies in MTLE-HS.

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.

Anti-GAD antibodies in a cohort of neuropsychiatric patients

OBJECTIVE

Antiglutamate decarboxylase (anti-GAD) antibodies are associated with several neurological manifestations, like epilepsy and movement disorders. However, in daily neurological practice, it remains hard to define when to test for anti-GAD antibodies in patients with neurologic and/or psychiatric symptoms. Therefore, here, we report the patient characteristics of a large retrospective cohort of patients tested for anti-GAD antibodies in clinical practice and compare the characteristics of anti-GAD positive and anti-GAD negative patients.

METHODS

We blindly assessed relevant clinical symptoms and comorbidities and functional outcome with the modified Rankin Scale (mRS) in a retrospective observational cohort of all patients in which the decision to assess anti-GAD levels had been made based solely on the presence of possible associated neurological and/or psychiatric symptoms (N=119).

RESULTS

Out of 119 patients, 17 (14.3%) were anti-GAD positive. The anti-GAD positive patients had a median age of 30years (range: 3-64; 2 children). They all had epilepsy, with 8 (47%) patients reporting cognitive complaints. Psychiatric symptoms were less prevalent in anti-GAD positive patients, only 1 anti-GAD positive patient (6%) versus 34 anti-GAD negative patients (33%) reported psychiatric symptoms (p=0.021). The most frequent comorbidity of anti-GAD positive patients was diabetes mellitus type 1 (n=8). Twelve (71%) and 13 (78%) of the anti-GAD positive patients were functionally independent at the time of diagnosis and after one year, respectively (mRS score: 0 to 2). There was no significant difference in functional status at any time during follow-up compared with the anti-GAD negative group.

CONCLUSION

Antiglutamate decarboxylase (anti-GAD) antibodies relate to epilepsy with or without cognitive complaints. However, psychiatric symptoms were almost absent in anti-GAD positive patients, and the presence of anti-GAD antibodies contributed little to the prognosis in our cohort.

GAD65 autoantibody characteristics in patients with co-occurring type 1 diabetes and epilepsy may help identify underlying epilepsy etiologies

Background

Autoantibodies against the smaller isoform of glutamate decarboxylase (GAD65Ab) reflect autoimmune etiologies in Type 1 diabetes (T1D) and several neurological disorders, including Stiff Person Syndrome (SPS). GAD65Ab are also reported in cases of epilepsy, indicating an autoimmune component. GAD65Ab in patients with co-occurring T1D, epilepsy or SPS may be part of either autoimmune pathogenesis. To dissect the etiologies associated with GAD65Ab, we analyzed GAD65Ab titer, epitope specificity and enzyme inhibition in GAD65Ab-positive patients diagnosed with epilepsy (n = 28), patients with epilepsy and T1D (n = 10), patients with SPS (n = 20), and patients with T1D (n = 42).

Results

GAD65Ab epitope pattern in epilepsy differed from T1D and SPS patients. Four of 10 patients with co-occurring T1D and epilepsy showed GAD65Ab profiles similar to T1D patients, while lacking GAD65Ab characteristics found in GAD65Ab-positive epilepsy patients. One of these patients responded well to anti-epileptic drugs (AEDs), while another patient did not require medication for seizure control. The third patient was refractory due to a diagnosis of meningioma. The response of the remaining patient to AEDs was unknown. GAD65Ab in the remaining six patients with T1D and epilepsy showed profiles similar to those in epilepsy patients.

Conclusions

Different autoimmune responses associated with T1D, epilepsy and SPS are reflected by disease-specific GAD65Ab patterns. Moreover, the epileptic etiology in patients diagnosed with both T1D and epilepsy may present two different etiologies regarding their epileptic condition. In one group T1D co-occurs with non-autoimmune epilepsy. In the other group GAD65Ab are part of an autoimmune epileptic condition.

Antiglutamic acid decarboxylase 65 (GAD65) antibody-associated epilepsy

Glutamic acid decarboxylase (GAD) antibody-associated encephalitis causes both acute seizures and chronic epilepsy with predominantly temporal lobe onset. This condition is challenging in diagnosis and management, and the incidence of GAD antibody (Ab)-related epilepsy could be much higher than commonly believed. Imaging and CSF evidence of inflammation along with typical clinical presentations, such as adult onset temporal lobe epilepsy (TLE) with unexplained etiology, should prompt testing for the diagnostic antibodies. High serum GAD Ab titer (≥2000U/mL or ≥20nmol/L) and evidence of intrathecal anti-GAD Ab synthesis support the diagnosis. Unlike other immune-mediated epilepsies, antiglutamic acid decarboxylase 65 (GAD65) antibody-mediated epilepsy is often poorly responsive to antiepileptic drugs (AEDs) and only moderately responsive to immune therapy with steroids, intravenous immunoglobulin (IVIG), or plasma exchange (PLEX). Long-term treatment with more aggressive immunosuppressants such as rituximab (RTX) and/or cyclophosphamide is often necessary and may be more effective than current immunosuppressive approaches. The aim of this review is to review the physiology, pathology, clinical presentation, related ancillary tests, and management of GAD Ab-associated autoimmune epilepsy by searching the keywords and to promote the recognition and the initiation of proper therapy for this condition.

Seizure semiology: an important clinical clue to the diagnosis of autoimmune epilepsy

Objective

The purpose of this study is to analyze the seizure semiologic characteristics of patients with autoimmune epilepsy (AE) and describe the investigation characteristics of AE using a larger sample size.

Methods

This observational retrospective case series study was conducted from a tertiary epilepsy center between May 2014 and March 2017. Cases of new‐onset seizures were selected based on laboratory evidence of autoimmunity. At the same time, typical mesial temporal lobe epilepsy (MTLE) patients with hippocampal sclerosis (HS) were recruited as the control group from the subjects who underwent presurgical evaluation during the same period.

Results

A total of 61 patients with AE were identified. Specific autoimmune antibodies were detected in 39 patients (63.93%), including anti‐VGKC in 23 patients (37.70%), anti‐NMDA‐R in 9 patients (14.75%), anti‐GABA_B‐R in 6 patients (9.84%), and anti‐amphiphysin in 1 patient (1.64%). Regarding the seizure semiology, no significant differences were noted between AE patients with autoantibody and patients with suspected AE without antibody. Compared to typical MTLE patients with HS, both AE patients with autoantibody and patients with suspected AE without antibody had the same seizure semiologic characteristics, including more frequent SPS or CPS, shorter seizure duration, rare postictal confusion, and common sleeping SGTC seizures.

Significance

This study highlights important seizure semiologic characteristics of AE. Patients with autoimmune epilepsy had special seizure semiologic characteristics. For patients with autoimmune epilepsy presenting with new‐onset seizures in isolation or with a seizure‐predominant neurological disorder, the special seizure semiologic characteristics may remind us to test neuronal nuclear/cytoplasmic antibodies early and initiate immunomodulatory therapies as soon as possible. Furthermore, the absence of neural‐specific autoantibodies does not rule out AE.

Seizures and risk of epilepsy in autoimmune and other inflammatory encephalitis

PURPOSE OF REVIEW

The aim of this study was to assess the seizure manifestations and risk of epilepsy in encephalitis associated with antibodies against neuronal cell-surface (autoimmune encephalitis) or myelin-associated antigens, and to review several chronic epileptic disorders, including Rasmussen's encephalitis, fever-induced refractory epileptic syndromes (FIRES) and new-onset refractory status epilepticus (NORSE).

RECENT FINDINGS

Seizures are a frequent manifestation of autoimmune encephalitis. Some autoimmune encephalitis may associate with characteristic features: faciobrachial dystonic seizures (anti-LGI1 encephalitis), electroencephalogram extreme delta brush (anti-NMDAR) or multifocal FLAIR-MRI abnormalities (anti-GABAAR). In anti-LGI1 encephalitis, cortical, limbic and basal ganglia dysfunction results in different types of seizures. Autoimmune encephalitis or myelin-antibody associated syndromes are often immunotherapy-responsive and appear to have a low risk for chronic epilepsy. In contrast patients with seizures related to GAD65-antibodies (an intracellular antigen) frequently develop epilepsy and have suboptimal response to treatment (including surgery). Rasmussen's encephalitis or FIRES may occur with autoantibodies of unclear significance and rarely respond to immunotherapy. A study of patients with NORSE showed that 30% developed chronic epilepsy.

SUMMARY

Although seizures are frequent in all types of autoimmune encephalitis, the risk for chronic epilepsy is dependent on the antigen: lower if located on the cell-surface, and higher if intracellular. For other disorders (Rasmussen's encephalitis, FIRES, NORSE), the prognosis remains poor.

Investigation of anti-neuronal antibodies in status epilepticus of unknown etiology: a prospective study

There have been recent reports of antibody-mediated status epilepticus. The objective of our study was to investigate the prevalence of neuronal autoantibodies in patients with status epilepticus (SE) with unresolved etiology. The presence of neuronal autoantibodies was investigated prospectively in adult patients with SE who presented to our clinic between February 2012 and December 2013 with unresolved etiology. Clinical and electrophysiologic features of seropositive patients were recorded. Also, seronegative and seropositive patient groups were compared in terms of demographic and clinical features, treatment responses, and outcomes. Neuronal antibodies against N-methyl-D-aspartate receptor (NMDA-R) were positive in 2 patients, against glycine receptor (Gly-R) in 2 patients, and against gamma-aminobutyric acid-A receptor [GABA(A)R] in 1 patient, which constituted a total of 5 (22.7%) of 22 patients with SE with unidentified etiology. One of three patients with systemic tumors was positive for GABA(A)R antibody. Four patients had a short epilepsy duration, while one of the NMDA-R antibody-positive patients had chronic epilepsy and double cortex finding in MRI. There was no significant difference between seropositive and seronegative patient groups in terms of demographic and clinical features, treatment responses, and outcomes. Neuronal antibodies are found in a sizeable portion of de novo SE patients, who are potential candidates of autoimmune encephalitis. Alternatively, these antibodies may presumably also emerge in SE patients with a chronic epilepsy history as an epiphenomenon. Further research is required to make the distinction between these two different antibody formation mechanisms.

Autoantibodies against voltage-gated potassium channel and glutamic acid decarboxylase in psychosis: A systematic review, meta-analysis, and case series

Antibodies to the voltage-gated potassium channel (VGKC) complex and glutamic acid decarboxylase (GAD) have been reported in some cases of psychosis. We conducted the first systematic review and meta-analysis to investigate their prevalence in people with psychosis and report a case series of VGKC-complex antibodies in refractory psychosis. Only five studies presenting prevalence rates of VGKC seropositivity in psychosis were identified, in addition to our case series, with an overall prevalence of 1.5% (25/1720) compared to 0.7% in healthy controls (12/1753). Meta-analysis established that the pooled prevalence of GAD65 autoantibodies was 5.8% (95% confidence interval [CI]: 2.0-15.6%; I²  = 91%; nine studies) in psychotic disorders, with a prevalence of 4.6% (95%CI: 1.2-15.9%; nine studies; I²  = 89%) and 6.2% (95%CI: 1.2-27.0%; two studies; I²  = 69%) in schizophrenia and bipolar disorder, respectively. People with psychosis were more likely to have GAD65 antibodies than controls (odds ratio [OR], 2.24; 95%CI: 1.28-3.92%; P = 0.005; eight studies; I²  = 0%). Among 21 participants with treatment-resistant psychosis, none had VGKC antibodies. The prevalence of VGKC antibodies is low in psychosis. Our preliminary meta-analysis suggests that GAD autoantibodies are more common in people with psychosis than in controls, although few studies accounted for the possibility of co-existing type 1 diabetes mellitus and the clinical significance of reported GAD titers remains unclear. The paucity of studies reporting thresholds for defining GAD abnormality and rates of comorbid type 1 diabetes mellitus precludes interpretations regarding the influence of GAD antibodies on the development of psychotic disorders and may have led to an overestimate of the prevalence of GAD. Our case series fails to support the hypothesis that VGKC antibodies are linked to treatment resistance in psychosis, but the literature to date is remarkably sparse.

Innate and adaptive immunity in human epilepsies

Inflammatory mechanisms have been increasingly implicated in the origin of seizures and epilepsy. These mechanisms are involved in the genesis of encephalitides in which seizures are a common complaint. Experimental and clinical evidence suggests different inflammatory responses in the brains of patients with epilepsy depending on the etiology. In general, activation of both innate and adaptive immunity plays a role in refractory forms of epilepsy. Epilepsies in which seizures develop after infiltration of cells of the adaptive immune system in the central nervous system (CNS) include a broad range of epileptic disorders with different (known or unknown) etiologies. Infiltration of lymphocytes is observed in autoimmune epilepsies, especially the classical paraneoplastic encephalitides with antibodies against intracellular tumor antigens. The presence of lymphocytes in the CNS also has been found in focal cerebral dysplasia type 2 and in cortical tubers. Various autoantibodies have been shown to be associated with temporal lobe epilepsy (TLE) and hippocampal sclerosis of unknown etiology, which may be due to the presence of viral DNA. During the last decade, an increasing number of antineuronal autoantibodies directed against membranous epitopes have been discovered and are associated with various neurologic syndromes, including limbic encephalitis. A major challenge in epilepsy is to define biomarkers, which would allow the recognition of patient populations who might benefit from immune-modulatory therapies. Some peripheral inflammatory markers appear to be differentially expressed in patients with medically controlled and medically refractory and, as such, could be used for diagnostic, prognostic, or therapeutic purposes. Establishing an autoimmune basis in patients with drug-resistant epilepsy allows for efficacious and targeted immunotherapy. Although current immunotherapies can give great benefit to the correctly identified patient, there are limitations to their efficacy and they may have considerable side effects. Thus the identification of new immunomodulatory compounds remains of utmost importance.

Inhibition of glutamate decarboxylase (GAD) by ethyl ketopentenoate (EKP) induces treatment-resistant epileptic seizures in zebrafish

Epilepsy is a chronic brain disorder characterized by recurrent seizures due to abnormal, excessive and synchronous neuronal activities in the brain. It affects approximately 65 million people worldwide, one third of which are still estimated to suffer from refractory seizures. Glutamic acid decarboxylase (GAD) that converts glutamate into GABA is a key enzyme in the dynamic regulation of neural network excitability. Importantly, clinical evidence shows that lowered GAD activity is associated with several forms of epilepsy which are often treatment resistant. In the present study, we synthetized and explored the possibility of using ethyl ketopentenoate (EKP), a lipid-permeable GAD-inhibitor, to induce refractory seizures in zebrafish larvae. Our results demonstrate that EKP evoked robust convulsive locomotor activities, excessive epileptiform discharges and upregulated c-fos expression in zebrafish. Moreover, transgenic animals in which neuronal cells express apoaequorin, a Ca²⁺-sensitive bioluminescent photoprotein, displayed large luminescence signals indicating strong EKP-induced neuronal activation. Molecular docking data indicated that this proconvulsant activity resulted from the direct inhibition of both gad67 and gad65. Limited protective efficacy of tested anti-seizure drugs (ASDs) demonstrated a high level of treatment resistance of EKP-induced seizures. We conclude that the EKP zebrafish model can serve as a high-throughput platform for novel ASDs discovery.

Anti-Neuronal Autoantibodies in Both Drug Responsive and Resistant Focal Seizures with Unknown Cause

BACKGROUND

and Objective Autoimmunity is an emerging field of research in the etiology of different neurological disorders including epilepsy. We aimed to investigate the presence of neuronal autoantibodies in focal epilepsy with unknown cause and their clinical correlates in both drug-responsive and resistant patients.

METHOD

Between 2009 and 2010 94 patients were prospectively enrolled, had their antibodies tested and clinically followed." An additional 50 age- and gender-matched controls were also tested for antibodies. Age at examination, gender, age at onset, seizure frequency, risk factors, seizure precipitants, and type of seizures were noted. Plasma obtained from patients was frozen at -80°C and analysed for autoantibodies against VGKC-complex, VGCC, GAD, LGI1, CASPR2, NMDA, AMPA and GABAB receptors with immunocytochemistry and radioimmunoassay as required.

RESULTS

Thirteen (13.8%) patients, but none of the controls, had antibodies (p=0.003). Antibodies were directed against the uncharacterized components of VGKC-complex in 5 patients (5.3%), GAD in 4 patients (4.2%), NMDA-R in 1 patient (1%), AMPA-R in 1 patient (1%) and both GAD and VGKC-complex in 2 patients (2.1%). Prognosis of epilepsy, in subsequent follow-up, did not correlate to general presence of anti-neuronal antibodies with slightly more patients with antibodies epilepsy control than without (76.9% vs. 69.1%, not-statistically significant. Three patients with suspected active autoimmunity and epilepsy who were treated, showed a response to treatment with a reduction in the seizure frequency. Although most clinical features were identical between seropositive and seronegative patient groups, seropositive patients were more likely to have inflammatory/autoimmune disorders in their medical history.

DISCUSSION

In keeping with previous studies, we have shown anti-neuronal antibodies in a proportion of focal epilepsy patients. Although autoimmunity might merely occur as a bystander effect in many chronic neurological disorders, association of anti-neuronal antibodies with good response to immunotherapy and coexisting autoimmune disorders suggests that anti-neuronal autoimmunity might participate in seizure formation at least in a subgroup of focal epilepsy patients.

CONCLUSION

Immunity may play a role in some patients with unknown etiology regardless of prognosis and immunmodulatuar treatment may be helpful in seropositive group.