Fulminant Anti-GAD antibody encephalitis presenting with status epilepticus requiring aggressive immunosuppression

IT-DEX and B cell depletion in a child with anti-GAD 65 autoimmune encephalitis presenting as NORSE: A case report

New-onset refractory status epilepticus (NORSE) is a devastating clinical condition that often leads to severe disability. Intrathecal dexamethasone (IT-DEX) has been reported to improve refractory status epilepticus. We present an 11-year-old female with anti-GAD 65 encephalitis presenting as NORSE who had minimal response to standard anti-seizure medications and first-line immunotherapies. The patient received 6 doses of IT-DEX in conjunction with rituximab which correlated with subsequent decreased neuroinflammation, reduced seizure burden and aided in weaning anesthetic infusions. Our case with literature review suggests IT-DEX may be utilized as an early intervention in those with refractory status epilepticus from various etiologies.

Paraneoplastic encephalitis

The first reports of encephalitis associated with cancer date to the 1960s and were characterized by clinical and pathologic involvement of limbic areas. This specific association was called limbic encephalitis (LE). The subsequent discovery of several "onconeural" antibodies (Abs), i.e., Abs targeting an antigen shared by neurons and tumor cells, supported the hypothesis of an autoimmune paraneoplastic etiology of LE and other forms of rapidly progressive encephalopathy. Over the past 20 years, similar clinical pictures with different clinical courses have been described in association with novel Abs-binding neuronal membrane proteins and proved to be pathogenic. The most well-known encephalitis in this group was described in 2007 as an association of a complex neuro-psychiatric syndrome, N-methyl-d-aspartate (NMDA) receptor-Abs, and ovarian teratoma in young women. Later on, nonparaneoplastic cases of NMDA receptor encephalitis were also described. Since then, the historical concept of LE and Ab associated encephalitis has changed. Some of these occur in fact more commonly in the absence of a malignancy (e.g., anti-LG1 Abs). Lastly, seronegative cases were also described. The term paraneoplastic encephalitis nowadays encompasses different syndromes that may be triggered by occult tumors.

Meningoencephalitis associated with GAD65 autoimmunity

Background

Encephalitis has been recognized in patients with autoimmunity related to the 65-kDa isoform of glutamic acid decarboxylase (GAD65) antibodies; however, patients with meningoencephalitis associated with those antibodies have been rarely identified in the medical literature. We aimed to define the frequency, clinical features, response to therapy, and functional outcomes of patients with meningoencephalitis associated with GAD antibodies.

Methods

We retrospectively studied consecutive patients attending a tertiary care center for evaluation of an autoimmune neurological disorder from January 2018 to June 2022. The modified Rankin Scale (mRS) was used to assess the functional outcome at the last follow-up.

Results

We evaluated 482 patients with confirmed autoimmune encephalitis during the study period. Four among the 25 patients with encephalitis related to GAD65 antibodies were identified. One patient was excluded owing to the coexistence of NMDAR antibodies. Three male patients aged 36, 24, and 16 years had an acute (n = 1) or subacute (n = 2) onset of confusion, psychosis, cognitive symptoms, seizures, or tremor. No patient had fever or clinical signs of meningeal irritation. Mild pleocytosis (<100 leukocytes/106) was identified in two patients, whereas one patient had normal CSF. Following immunotherapy with corticosteroids (n = 3) or intravenous immunoglobulin (n = 1), significant improvement was observed in all three cases, achieving a good outcome (mRS 1) in all cases.

Conclusion

Meningoencephalitis is an uncommon presentation of GAD65 autoimmunity. Patients present with signs of encephalitis but with meningeal enhancement and have good outcomes.

Anti-Glutamic Acid Decarboxylase (GAD) 65 Encephalitis Mistaken for Herpes Encephalitis and Hashimoto’s Encephalitis (HE): A Case Report

Autoimmune encephalitis is increasingly recognized in clinical practice. We are presenting a 72-year-old female patient who initially presented with a new onset seizure with temporal lobe abnormality on imaging. This was initially attributed to herpes encephalitis although herpes polymerase chain reaction (PCR) was negative. The patient was treated with acyclovir and antiepileptic medication (AEM) with some clinical improvement. She presented again with refractory seizure evolving to status epilepticus. Escalation of AEMs was pursued and positive anti-thyroid peroxidase (TPO) antibody prompted consideration of Hashimoto's encephalitis (HE) and treatment with high-dose corticosteroids and intravenous immunoglobulin (IVIG). However, poor response to steroid argued against HE, and extended autoimmune encephalitis panel revealed positive anti-glutamic acid decarboxylase (GAD) antibody. This case raises the clinical pearl that anti-thyroid antibodies, e.g anti-TPO antibody, can be seen in those with autoimmune encephalopathies other than HE and HE remains a diagnosis of exclusion. It also helps to remind clinicians that a new onset refractory seizure even with temporal lobe changes is not pathognomonic for herpes encephalitis, and although negative serology does not rule out the diagnosis, it is recommended to rule out autoimmune encephalitis as it shares similar clinical and radiological picture.

A Rare Presentation of a Complex Mixed Autoimmune Encephalitis Diagnosis: A Case Report and Literature Review

This case report presents a unique case of a difficult differential diagnosis of autoimmune encephalitis (AE) in the setting of Mycoplasma pneumoniae. A 40-year-old female with a history of Hashimoto thyroiditis, polycystic ovarian syndrome, and a lower respiratory infection presented to the emergency department with new-onset progressive neurological symptoms. These included generalized tonic-clonic seizure and worsening respiratory status that required intubation and tracheostomy. Blood cultures returned positive for M. pneumoniae. We concluded this to be a mixed diagnosis case of anti-glutamic acid decarboxylase 65 (anti-GAD65), Bickerstaff’s brainstem encephalitis (BBE), Hashimoto’s encephalopathy (HE), and Miller Fisher Syndrome (MFS) concurrently in the setting of M. pneumoniae. Initial treatment with intravenous immunoglobulin showed minimal improvement; however, subsequent treatment with plasmapheresis proved to be beneficial for the patient. Over the course of the plasma exchange therapy (PLEX), the patient slowly became more alert, attentive, and verbal. She was able to answer simple questions and follow commands. Common trends of age, gender, presenting symptoms, associated antibodies, and sessions of PLEX in different AE diseases were identified through a literature review. Only 69.7% of the cases implemented PLEX or plasmapheresis. Currently, there is no standard protocol for the treatment of AE. Our case report aims to present a clinically complicated example of AE and to provide further evidence to support PLEX as an important therapeutic option.

Stiff-person Syndrome and GAD Antibody-spectrum Disorders: GABAergic Neuronal Excitability, Immunopathogenesis and Update on Antibody Therapies

Although antibodies against Glutamic Acid Decarboxylase (GAD) were originally associated with Stiff Person Syndrome (SPS), they now denote the "GAD antibody-spectrum disorders (GAD-SD)" that include Cerebellar Ataxia, Autoimmune Epilepsy, Limbic Encephalitis, PERM and eye movement disorder. In spite of the unique clinical phenotype that each of these disorders has, there is significant overlapping symptomatology characterized by autoimmune neuronal excitability. In addition to GAD, three other autoantibodies, against glycine receptors, amphiphysin and gephyrin, are less frequently or rarely associated with SPS-SD. Very high serum anti-GAD antibody titers are a key diagnostic feature for all GAD-SD, commonly associated with the presence of GAD antibodies in the CSF, a reduced CSF GABA level and increased anti-GAD-specific IgG intrathecal synthesis denoting stimulation of B-cell clones in the CNS. Because anti-GAD antibodies from the various hyperexcitability syndromes recognize the same dominant GAD epitope, the clinical heterogeneity among GAD-SD patients remains unexplained. The paper highlights the biologic basis of autoimmune hyperexcitability connected with the phenomenon of reciprocal inhibition as the fundamental mechanism of the patients' muscle stiffness and spasms; addresses the importance of high-GAD antibody titers in diagnosis, pinpointing the diagnostic challenges in patients with low-GAD titers or their distinction from functional disorders; and discusses whether high GAD-antibodies are disease markers or pathogenic in the context of their association with reduced GABA level in the brain and CSF. Finally, it focuses on therapies providing details on symptomatic GABA-enhancing drugs and the currently available immunotherapies in a step-by-step approach. The prospects of future immunotherapeutic options with antibody therapies are also summarized.

Diagnosis and Management of Status Epilepticus

Seizures are among the most common neurological presentations to the emergency room. They present on a spectrum of severity from isolated new-onset seizures to acute repetitive seizures and, in severe cases, status epilepticus. The latter is the most serious, as it is associated with high morbidity and mortality. Prompt recognition and treatment of both seizure activity and associated acute systemic complications are essential to improve the overall outcome of these patients. The purpose of this review is to provide the current viewpoint on the diagnostic evaluation and pharmacological management of patients presenting with status epilepticus, and the common associated systemic complications.

Thalamic Lesions in a Toddler with Glutamic Acid Decarboxylase Autoimmune Encephalitis

We present a child with glutamic acid decarboxylase (GAD) autoimmune encephalitis (AE) with bilateral thalamic lesions on magnetic resonance imaging (MRI) of the brain. A healthy 21-month-old girl, after superrefractory status epilepticus (SE) and fever developed dyskinesia and ataxia, which we subsequently diagnosed as GAD AE. She showed remarkable response to treatment with methylprednisolone and intravenous immunoglobulin (IVIg). Following an initial normal MRI of her brain, a further brain imaging showed bilateral thalamic lesions. This is an unusual finding since brain imaging abnormalities, when found in GAD AE, mostly involve the mesial temporal lobe structures. Thalamic lesions in GAD AE have not been reported previously.

[Pharmacotherapy and intensive care aspects of status epilepticus: update 2020/2021]

Die gezielte Therapie epileptischer Ereignisse und im Speziellen des Status epilepticus (SE) setzt das sichere Erkennen der Krankheitsbilder voraus, wofür gerade bei Formen mit vorwiegend nichtmotorischen Symptomen klinische und elektroenzephalographische Expertise notwendig ist. Die im Jahr 2020 erfolgte Fortschreibung der deutschen Leitlinie zur Behandlung des SE hält an der streng stufengerechten Therapie fest, die eskalierend die Anwendung von Benzodiazepinen, spezifischen Antiepileptika und Anästhetika vorsieht. Bisher ist die Eingrenzung eines in den allermeisten Fällen wirksamen sowie zugleich sicheren und interaktionsfreien Antiepileptikums nicht gelungen. Individuelle Vorerkrankungen und aktuelle Begleitumstände gehen daher genauso wie Erfahrungen des Behandlerteams in die differenzierte Behandlung des SE ein. Insbesondere bei therapierefraktären Formen des SE erweist sich die Therapie als durchaus kompliziert und hat regelhaft intensivmedizinische Implikationen. Mithin ergeben sich im Zuge der modernen SE-Behandlung zahlreiche interdisziplinäre Schnittstellen. Zukünftige wissenschaftliche Fragstellungen werden sich u. a. mit der optimalen Therapie des nonkonvulsiven SE und hier v. a. dem Ausmaß und dem Zeitpunkt von adäquaten Therapieschritten sowie mit assoziierten ethischen Fragen einer Therapieeskalation beschäftigen.

Pro- and anti-inflammatory response in neurological disorders associated to anti-glutamate decarboxylase antibodies

Rare conditions showing psychiatric symptoms and movement disorders have been linked with the presence of anti-glutamate decarboxylase antibodies. Proinflammatory and antiinflammatory immune responses were assessed in patients with neurological disorders associated to anti-glutamic acid decarboxylase antibodies (NDGAD). Immunoregulatory and proinflammatory cell populations were quantified by flow cytometry. No polarization toward Th1, Th2, or Th17 phenotypes was observed in NDGAD patients. Immunoregulatory responses were significantly reduced for Breg, activated Treg, Tr1, and Th3 cells, suggesting a deficient regulatory response, while intermediate monocyte levels were increased. The reduced levels of regulatory T and B cells suggest an impairment in regulatory immune response, while intermediate monocytes could be playing a role in the increased proinflammatory response.

Super refractory status epilepticus secondary to anti-GAD antibody encephalitis successfully treated with aggressive immunotherapy

Antibodies against glutamic acid decarboxylase are reported in association with a number of neurological conditions including limbic encephalitis. We report a case of anti-GAD-antibody associated encephalitis presenting with super-refractory status epilepticus. We describe the clinical course, management, and the outcome. In addition, we review the presentation and outcomes of reported cases of anti-GAD encephalitis. Similar to the reported cases of anti-GAD encephalitis, our case was refractory to treatment with conventional antiseizure medication. Treatment with intravenous immune globulin (IVIG), high dose corticosteroids, and plasmapheresis had partial response, but escalation of treatment to the use of tocilizumab was associated with significant clinical improvement.

Therapeutic Options for Patients with Refractory Status Epilepticus in Palliative Settings or with a Limitation of Life-Sustaining Therapies: A Systematic Review

BACKGROUND

Refractory status epilepticus (RSE) represents a serious medical condition requiring early and targeted therapy. Given the increasing number of elderly or multimorbid patients with a limitation of life-sustaining therapy (LOT) or within a palliative care setting (PCS), guidelines-oriented therapy escalation options for RSE have to be omitted frequently.

OBJECTIVES

This systematic review sought to summarize the evidence for fourth-line antiseizure drugs (ASDs) and other minimally or non-invasive therapeutic options beyond guideline recommendations in patients with RSE to elaborate on possible treatment options for patients undergoing LOT or in a PCS.

METHODS

A systematic review of the literature in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, focusing on fourth-line ASDs or other minimally or non-invasive therapeutic options was performed in February and June 2020 using the MEDLINE, EMBASE and Cochrane databases. The search terminology was constructed using the name of the specific ASD or therapy option and the term 'status epilepticus' with the use of Boolean operators, e.g. "(brivaracetam) AND (status epilepticus)". The respective Medical Subject Headings (MeSH) and Emtree terms were used, if available.

RESULTS

There is currently no level 1, grade A evidence for the use of ASDs in RSE. The best evidence was found for the use of lacosamide and topiramate (level 3, grade C), followed by brivaracetam, perampanel (each level 4, grade D) and stiripentol, oxcarbazepine and zonisamide (each level 5, grade D). Regarding non-medicinal options, there is little evidence for the use of the ketogenic diet (level 4, grade D) and magnesium sulfate (level 5, grade D) in RSE. The broad use of immunomodulatory or immunosuppressive treatment options in the absence of a presumed autoimmune etiology cannot be recommended; however, if an autoimmune etiology is assumed, steroid pulse, intravenous immunoglobulins and plasma exchange/plasmapheresis should be considered (level 4, grade D). Even if several studies suggested that the use of neurosteroids (level 5, grade D) is beneficial in RSE, the current data situation indicates that there is formal evidence against it.

CONCLUSIONS

RSE in patients undergoing LOT or in a PCS represents a challenge for modern clinicians and epileptologists. The evidence for the use of ASDs in RSE beyond that in current guidelines is low, but several effective and well-tolerated options are available that should be considered in this patient population. More so than in any other population, advance care planning, advance directives, and medical ethical aspects have to be considered carefully before and during therapy.

Clinical characteristics and outcomes of autoimmune encephalitis patients associated with anti-glutamate decarboxylase antibody 65

OBJECTIVE

This study was to investigate the clinical characteristics and prognosis of autoimmune encephalitis (AE) associated with anti-Glutamic Acid Decarboxylase 65 (GAD65).

PATIENTS AND METHODS

From Jan 2016 to Aug 2018, three patients diagnosed as anti-GAD65 AE in our hospital were retrospectively analyzed for their general demographic characteristics, clinical presentation, cerebrospinal fluid (CSF) cytology, brain imaging, EEG, treatment and prognosis.

RESULTS

We found that Anti-GAD65 AE may be more common in young and middle-aged women, with initial presentations of refractory status epilepticus or cognitive decline following the disease progresses, but with less psychiatric symptoms than other types of AEs. The abnormal signals of MRI may be obvious in bilateral frontal, temporal lobe and hippocampus.

CONCLUSION

The production of anti-GAD65 may have a certain latency period, and it is usually negative at the onset stage. More studies need to be performed on larger populations and further understand the potential mechanisms underlying the above clinical features of anti-GAD65 AE.

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.

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.