Two Cases of Pediatric Leucine-Rich Glioma-Inactivated Protein-1 Encephalitis: Clinical Course, Challenges, and Implications.

BACKGROUND: Leucine-rich glioma-inactivated protein 1 (LGI-1) encephalitis is a rare form of autoimmune limbic encephalitis. Although relatively well documented in adults, pediatric cases are rare and remain poorly understood. METHODS: We reviewed two pediatric cases of LGI-1 encephalitis from a single tertiary care facility retrospectively. The detailed analysis included assessment of the initial presentation, clinical progression, diagnostic challenges, treatments, and outcome. To contextualize the differences between pediatric and adult manifestations of disease, we compared these findings with existing literature. RESULTS: Both cases illustrate the diagnostic challenges faced at initial presentation due to the rarity of this diagnosis in children and the absence of characteristic faciobrachial dystonic seizures, which is common in adults. The constellation of neuropsychiatric symptoms and refractory focal seizures led to a high clinical suspicion for autoimmune encephalitis, therefore, both cases were treated empirically with intravenous methylprednisolone. The diagnosis in both cases was confirmed with positive serum antibody testing, reinforcing that LGI-1 antibodies are more sensitive in the serum rather than the cerebrospinal fluid (CSF). Seizure control and improvement in cognitive symptoms was achieved through a combination of immunotherapy and antiseizure medications. CONCLUSIONS: This case series underscores the significance of considering LGI-1 encephalitis in the differential diagnosis of pediatric patients exhibiting unexplained neuropsychiatric symptoms and focal seizures and emphasizes the importance of performing both serum and CSF antibody testing. It is necessary to conduct further research to identify the full range of pediatric presentations and to determine the optimal treatment protocol.

Study on clinical features and factors related to long-term outcomes of antibody-negative autoimmune encephalitis.

OBJECTIVE: To delineate the clinical characteristics of antibody-negative autoimmune encephalitis (AE) and to investigate factors associated with long-term outcomes among antibody-negative AE. METHODS: Patients diagnosed with antibody-negative AE were recruited from January 2016 to December 2022 at the Second Xiangya Hospital of Central South University. The study assessed the long-term outcomes of antibody-negative AE using the modified Rankin scale (mRS) and the Clinical Assessment Scale in Autoimmune Encephalitis (CASE). Predictors influencing long-term outcomes were subsequently analyzed. External validation of RAPID scores (refractory status epilepticus [RSE], age of onset ≥60 years, ANPRA [antibody-negative probable autoimmune encephalitis], infratentorial involvement, and delay of immunotherapy ≥1 month) was performed. RESULTS: In total, 100 (47 females and 53 males) antibody-negative AE patients were enrolled in this study, with approximately 49 (49%) experiencing unfavorable long-term outcomes (mRS scores ≥3). Antibody-negative AE was subcategorized into ANPRA, autoimmune limbic encephalitis (LE), and acute disseminated encephalomyelitis (ADEM). Psychiatric symptoms were prevalent in LE and ANPRA subtypes, while weakness and gait instability/dystonia were predominant in the ADEM subtype. Higher peak CASE scores (odds ratio [OR] 1.846, 95% confidence interval [CI]: 1.163-2.930, p = 0.009) and initiating immunotherapy within 30 days (OR 0.210, 95% CI: 0.046-0.948, p = 0.042) were correlated with long-term outcomes. Receiver operating characteristic (ROC) analysis returned that the RAPID scores cutoff of 1.5 best discriminated the group with poor long-term outcomes (sensitivity 85.7%, specificity 56.9%). INTERPRETATION: The ANPRA subtype exhibited poorer long-term outcomes compared to LE and ADEM subtypes, and early immunotherapy was crucial for improving long-term outcomes in antibody-negative AE. The use of RAPID scoring could aid in guiding clinical decision making.

Stiff Person Syndrome and GAD Antibody-Spectrum Disorders.

OBJECTIVE: Antibodies against glutamic acid decarboxylase (GAD), originally associated with stiff person syndrome (SPS), define the GAD antibody-spectrum disorders that also include cerebellar ataxia, autoimmune epilepsy, limbic encephalitis, progressive encephalomyelitis with rigidity and myoclonus (PERM), and eye movement disorders, all of which are characterized by autoimmune neuronal excitability. This article elaborates on the diagnostic criteria for SPS and SPS spectrum disorders, highlights disease mimics and misdiagnoses, describes the electrophysiologic mechanisms and underlying autoimmunity of stiffness and spasms, and provides a step-by-step therapeutic scheme. LATEST DEVELOPMENTS: Very-high serum GAD antibody titers are diagnostic for GAD antibody-spectrum disorders and also predict the presence of GAD antibodies in the CSF, increased intrathecal synthesis, and reduced CSF γ-aminobutyric acid (GABA) levels. Low serum GAD antibody titers or the absence of antibodies generates diagnostic challenges that require careful distinction in patients with a variety of painful spasms and stiffness, including functional neurologic disorders. Antibodies against glycine receptors, first found in patients with PERM, are seen in 13% to 15% of patients with SPS, whereas amphiphysin and gephyrin antibodies, seen in 5% of patients with SPS spectrum disorders, predict a paraneoplastic association. GAD-IgG from different SPS spectrum disorders recognizes the same dominant GAD intracellular epitope and, although the pathogenicity is unclear, is an excellent diagnostic marker. The biological basis of muscle stiffness and spasms is related to autoimmune neuronal hyperexcitability caused by impaired reciprocal γ-aminobutyric acid-mediated (GABA-ergic) inhibition, which explains the therapeutic response to GABA-enhancing agents and immunotherapies. ESSENTIAL POINTS: It is essential to distinguish SPS spectrum disorders from disease mimics to avoid both overdiagnoses and misdiagnoses, considering that SPS is treatable if managed correctly from the outset to prevent disease progression. A step-by-step, combination therapy of GABA-enhancing medications along with immunotherapies ensures prolonged clinical benefits.

Encefalitis límbica asociada a secreción inadecuada de hormona antidiurética. Reporte de un caso y revisión de la literatura / Limbic encephalitis associated with inappropriate secretion of antidiuretic hormone. A case report and literature review / Encefalite límbica associada à secreção inapropriada de hormônio antidiurético. Relato de caso e revisão da literatura

La encefalitis límbica (EL) autoinmune es una afección neurológica infrecuente de curso subagudo con manifestaciones neuropsicológicas. Actualmente el tratamiento inmunoterápico agudo o de mantenimiento es dirigido según el anticuerpo neural acompañante y la presencia o ausencia de cáncer. Presentamos el caso de una mujer de 52 años con hipotiroidismo autoinmune, síndrome de secreción inadecuada de hormona antidiurética (SIADH) e hiponatremia (hipoNa) persistente, con evolución progresiva de perdida de la memoria y crisis distónicas faciobraquiales (DFBC) a quien se le realiza un diagnóstico oportuno de encefalitis límbica. Recibió tratamiento intravenoso combinado en base a corticoides e inmunoglobulina con buena respuesta y morbilidad mínima neuropsicológica. El reconocimiento de esta patología permite un diagnóstico y tratamiento temprano, imprescindible para mejorar el pronóstico de estos pacientes.

Autoimmune limbic encephalitis is a rather unusual neurological condition with subacute progression and neuropsychological symptoms. Currently, acute or maintenance treatment with immunotherapy is targeted depending on the accompanying neural specific antibody and the presence or absence of cancer. The study presents the case of a 52-year-old woman suffering from autoimmune hypothyroidism, syndrome of inappropriate secretion of anti-diuretic hormone (SIADH) and persistent hyponatremia, with progressive evolution which involved memory loss and faciobrachial dystonic seizures (FBDS). She was timely diagnosed with limbic encephalitis and was treated with intravenous combined corticosteroids and immunoglobulin therapy. Response was good, with minimum neuropsychological. Recognizing this condition allows for early diagnosis and treatment, what is key to improve the prognosis of these patients.

A encefalite límbica (LE) autoimune é uma condição neurológica rara de curso subagudo com manifestações neuropsiquiátrica. Atualmente, o tratamento com imunoterapia aguda ou de manutenção é orientado de acordo com o anticorpo neural e a presença ou ausência de câncer. Apresentamos o caso de uma mulher de 52 anos com hipotireoidismo autoimune, síndrome de secreção inapropriada de hormônio antidiurético e hiponatremia persistente, com evolução progressiva da perda de memória e crises distônicas faciobraquiais que foi diagnosticada oportunamente como encefalite límbica. Recebeu tratamento endovenoso combinado à base de corticoide e imunoglobulina com boa resposta e morbidade neuropsiquiátrica mínima. O reconhecimento desta patologia permite um diagnóstico e tratamento precoces, essenciais para melhorar o prognóstico desses pacientes.

Encefalitis límbica: clínica, patogenia y problemas diagnósticos / Limbic encephalitis: clinic, pathogenesis and diagnostic problems

La encefalitis límbica es una enfermedad infrecuente y potencialmente grave, que puede o no ser paraneoplásica y se caracteriza por déficit de la memoria reciente, alteraciones psiquiátricas y convulsiones. De origen autoinmunitario, está asociada a anticuerpos séricos e intratecales contra antígenos neuronales intracelulares y de superficie, con especial afectación de zonas límbicas. En este artículo se revisan aspectos históricos y epidemiológicos, patogenia, síndromes más frecuentes y mejor delimitados, histopatología y estudios complementarios. Se repasan también las dificultades del diagnóstico diferencial y la necesidad de descartar siempre un tumor subyacente. La detección de autoanticuerpos neuronales es importante para el diagnóstico, la planificación terapéutica y el pronóstico. La inmunoterapia y, si corresponde, el tratamiento de la neoplasia son cruciales para lograr una recuperación neurológica sustancial. La encefalitis límbica es una entidad probablemente subdiagnosticada, con un pronóstico más favorable si se trata de forma temprana. El actual conocimiento de su patogenia puede además aportar claridad para la mejor comprensión de otros síndromes neurológicos y psiquiátricos que puedan compartir mecanismos autoinmunitarios, como algunos trastornos psicóticos y epilepsias farmacorresistentes. (AU)

Limbic encephalitis is a rare and potentially serious disease, which may or may not be paraneoplastic and is characterized by recent memory deficits, psychiatric disturbances and seizures. Of autoimmune origin, it is associated with serum and intrathecal antibodies against intracellular and surface neuronal antigens, with special involvement of limbic areas. This article reviews historical and epidemiological aspects, pathogenesis, more frequent and better defined syndromes, histopathology and complementary studies. The difficulties of differential diagnosis and the need to always rule out an underlying tumor are also reviewed. Detection of neuronal autoantibodies is important for diagnosis, therapeutic planning and prognosis. Immunotherapy and, if appropriate, neoplasm treatment, are crucial to achieve substantial neurological recovery. Limbic encephalitis is probably an underdiagnosed entity, with a more favorable prognosis if treated early. The current knowledge of its pathogenesis may also provide clarity for a better understanding of other neurological and psychiatric syndromes that may share autoimmune mechanisms, such as some psychotic disorders and drug-resistant epilepsies. (AU)

What should you know about limbic encephalitis? / O que deve saber sobre encefalites auto-imunes?

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

A encefalite autoimune é uma doença inflamatória caracterizada por envolvimento subagudo da memória de curto prazo, presença de sintomas psicóticos e crises epilépticas. Dada a diversidade de sintomas na apresentação, o diagnóstico diferencial é um verdadeiro desafio. Anteriormente, era considerada uma doença rara, de etiologia paraneoplásica e com mau prognóstico. No entanto, com a recente descoberta dos anticorpos dirigidos à superfície da membrana, é atualmente reconhecido que uma grande parte dos casos não tem uma neoplasia subjacente e apresenta um ótimo prognóstico. Assim, o diagnóstico e tratamento imunoterápico precoces são de extrema importância.