Immune Checkpoint Inhibitor-Related Cerebellar Toxicity: Clinical Features and Comparison with Paraneoplastic Cerebellar Ataxia.

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy, and the association with immune-related adverse events (irAEs) is well-established. However, cerebellar irAEs are poorly defined and their relationship with paraneoplastic disorders remains unclear. Our aim was (i) to characterize cerebellar irAE; (ii) to compare it with paraneoplastic cerebellar ataxia (PCA). We performed a multicenter, retrospective, cohort study of patients developing new-onset, immune-mediated, isolated/predominant cerebellar dysfunction after ICI administration. In addition, a systematic review following PRISMA guidelines was performed. Cerebellar irAE cases were compared with a consecutive cohort of patients with PCA. Overall, 35 patients were included, of whom 12 were original cases (males: 25/35 (71%), median age: 65 [range: 20-82]). The most frequent tumor was non-small cell lung cancer (12/35, 34%). Anti-PD1 were adopted in 19/35 (54%). Symptoms developed at a median of 11 weeks after ICI onset. Neuronal antibodies were detected in 15/31 patients tested (48%). Cerebrospinal fluid was inflammatory in 25/30 (83%). Magnetic resonance imaging showed cerebellar hyperintensities in 8/35 (23%). Immunotherapy was applied in 33/35 cases (94%), and most patients improved with residual disability (16/35, 46%). When compared with a series of PCA (n = 15), the cerebellar irAE group was significantly more associated with male sex, lung cancer (rather than gynecological/breast cancers), isolated ataxia, and a better outcome. We provide a detailed characterization of cerebellar irAE. Compared to PCA, differences exist in terms of tumor association, clinical features, and outcome. Clinical presentation-antibody-tumor triad in the ICI group only partially reflects the associations described in paraneoplastic disorders.

What we've learnt about autoimmune neurological diseases from neuropathology.

Antibody-associated autoimmune neurological diseases are a group of disorders with various immune effector mechanisms that result in significant differences in disease course and prognosis. Paraneoplastic or idiopathic autoimmune encephalitis associated with antibodies against intracellular antigens are mostly characterized by a T-cell-dominated inflammation with neuronal loss, astrogliosis, and microglial nodules. In anti-Yo paraneoplastic cerebellar degeneration CD8+/granzymeB+ T cells were demonstrated in close apposition to neurons along with a nuclear upregulation of the activator of transcription 1, suggesting an important role of interferon-gamma in disease pathogenesis. Early and late disease stages may show different lesion types. For example, tissue samples from patients with temporal lobe epilepsy associated with antiglutamic acid decarboxylase 65 antibodies in early disease stages show numerous infiltrating T cells targeting hippocampal neurons and high numbers of B cells and plasma cells, while in chronic stages inflammation gets less and is followed by hippocampal sclerosis. Similarly, antiglial fibrillary acidic protein meningoencephalomyelitis may show loss of astrocytes only in the very early lesions, whereas in subacute and chronic stages astrocytes can get replenished most likely due to their high regeneration potential. In contrast, neuropathology of autoimmune neurological diseases mediated by surface antibodies is mostly characterized by a dysfunction of neurons in the absence of immune-mediated neuronal damage. The interaction of surface antibodies with their target antigen and the resulting downstream mechanisms are variable and can range from an internalization of the receptor in well-preserved neurons in anti-N-methyl-D-aspartate receptor encephalitis to an irreversible internalization and blocking of the receptor that may be associated with an accumulation of phosphorylated tau in specific brain regions in anti-IgLON5 disease. Interestingly, anti-IgLON5 patients with short disease duration were shown to present prominent deposition of IgG4 in the neuropil and on neuronal membranes in the absence of neuronal tau deposits, suggesting that the immune mechanisms precede neurodegeneration. Knowledge about pathomechanisms and patterns of tissue damage in different disease stages of antibody-associated autoimmune diseases will help to identify novel biomarkers and can give important clues for possible therapeutic interventions.

Analytical evaluation of a GAD65 antibodies chemiluminescence immunoassay for CSF in neurological syndromes.

OBJECTIVES: Antibodies against glutamic acid decarboxylase isoform 65 (GAD-Ab) have been found in different severe neurological conditions associated with altered synthesis of γ-aminobutyric acid (GABA). Serum GAD-Ab can be found in up to 90 % of patients with type 1 diabetes mellitus (T1DM), mostly at relatively low concentrations, while high concentrations of GAD-ab are thought to be more frequently associate to a neurological condition, with levels 100-folds higher than those found in T1DM. Although CSF testing is recommended when suspecting a GAD-associated neurological syndrome, no commercial immunoassay is validated for this use and no cut-off is internationally recognized to support the diagnosis. METHODS: In this study we validated CSF testing of GAD-Ab on an automated chemiluminescence (CLIA) immunoassay that had previously shown good agreement with ELISA on serum. RESULTS: We tested 43 CSF from patients with typical GAD-associated neurological disorders and patients with other neurological conditions, identifying a clinical cut-off of 18 kIU/L that discriminated GAD-disease with an area under the curve (AUC) of 0.921. CLIA showed good analytical performances on repeatability and recovery tests in CSF and confirmed an excellent agreement with ELISA. CONCLUSIONS: GAD-Ab associated neurological disorders are rare but CSF testing for GAD-Ab is a common request for neurologists when suspecting an insidious autoimmune central nervous system disease. CLIA platforms are expected to be increasingly adopted in clinical laboratories due to their flexibility and reliability, therefore studies on decisional levels should be implemented for improving the interpretation and utilization of laboratory data.

Inositol 1,4,5-trisphosphate receptor type 1 autoantibody (ITPR1-IgG/anti-Sj)-associated autoimmune cerebellar ataxia, encephalitis and peripheral neuropathy: review of the literature.

BACKGROUND: In 2014, we first described novel autoantibodies to the inositol 1,4,5-trisphosphate receptor type 1 (ITPR1-IgG/anti-Sj) in patients with autoimmune cerebellar ataxia (ACA) in this journal. Here, we provide a review of the available literature on ITPR1-IgG/anti-Sj, covering clinical and paraclinical presentation, tumour association, serological findings, and immunopathogenesis. METHODS: Review of the peer-reviewed and PubMed-listed English language literature on ITPR1-IgG/anti-Sj. In addition, we provide an illustrative report on a new patient with ITPR1-IgG-associated encephalitis with cognitive decline and psychosis. RESULTS: So far, at least 31 patients with serum ITPR1-IgG/anti-Sj have been identified (clinical information available for 21). The most common manifestations were ACA, encephalopathy with seizures, myelopathy, and (radiculo)neuropathy, including autonomic neuropathy. In 45% of cases, an underlying tumour was present, making the condition a facultative paraneoplastic neurological disorder. The neurological syndrome preceded tumour diagnosis in all but one case. In most cases, immunotherapy had only moderate or no effect. The association of ITPR1-IgG/anti-Sj with manifestations other than ACA is corroborated by the case of a 48-year-old woman with high-titre ITPR1-IgG/anti-Sj antibodies and rapid cognitive decline, affecting memory, attention and executive function, and psychotic manifestations, including hallucinations, investigated here in detail. FDG-PET revealed right-temporal glucose hypermetabolism compatible with limbic encephalitis. Interestingly, ITPR1-IgG/anti-Sj mainly belonged to the IgG2 subclass in both serum and cerebrospinal fluid (CSF) in this and further patients, while it was predominantly IgG1 in other patients, including those with more severe outcome, and remained detectable over the entire course of disease. Immunotherapy with intravenous methylprednisolone, plasma exchange, and intravenous immunoglobulins, was repeatedly followed by partial or complete recovery. Long-term treatment with cyclophosphamide was paralleled by relative stabilization, although the patient noted clinical worsening at the end of each treatment cycle. CONCLUSIONS: The spectrum of neurological manifestations associated with ITPR1 autoimmunity is broader than initially thought. Immunotherapy may be effective in some cases. Studies evaluating the frequency of ITPR1-IgG/anti-Sj in patients with cognitive decline and/or psychosis of unknown aetiology are warranted. Tumour screening is essential in patients presenting with ITPR1-IgG/anti-Sj.

Novelties in Autoimmune and Paraneoplastic Cerebellar Ataxias: Twenty Years of Progresses.

Major advances in our knowledge concerning autoimmune and paraneoplastic cerebellar ataxias have occurred in the last 20 years. The discovery of several neural antibodies represents an undeniable contribution to this field, especially those serving as good biomarkers of paraneoplastic neurological syndromes and those showing direct pathogenic effects. Yet, many patients still lack detectable or known antibodies, and also many antibodies have only been reported in few patients, which makes it difficult to define in detail their clinical value. Nevertheless, a notable progress has additionally been made in the clinical characterization of patients with the main neural antibodies, which, although typically present with a subacute pancerebellar syndrome, may also show either hyperacute or chronic onsets that complicate the differential diagnoses. However, prodromal and transient features could be useful clues for an early recognition, and extracerebellar involvement may also be highly indicative of the associated antibody. Moreover, important advances in our understanding of the pathogenesis of cerebellar ataxias include the description of antibody effects, especially those targeting cell-surface antigens, and first attempts to isolate antigen-specific T-cells. Furthermore, genetic predisposition seems relevant, although differently involved according to cancer association, with particular HLA observed in non-paraneoplastic cases and genetic abnormalities in the tumor cells in paraneoplastic ones. Finally, immune checkpoint inhibitors used as cancer immunotherapy may rarely induce cerebellar ataxias, but even this undesirable effect may in turn serve to shed some light on their physiopathology. Herein, we review the principal novelties of the last 20 years regarding autoimmune and paraneoplastic cerebellar ataxias.

SOX-1 antibodies in a patient with Crohn's disease: a case report.

BACKGROUND: The anti-SOX-1 antibodies have been mainly associated with Lambert-Eaton Myasthenic Syndrome (LETMS) and Small-Cell Lung Cancer (SCLC). In this report, we describe the interesting case of a patient with serum anti-SOX-1 antibodies and Crohn's Disease (CD) with ensuing neurological symptoms. CASE PRESENTATION: A Caucasian 67-year-old female was admitted to the Emergency Department with seizures, vertigo, emesis, nausea, postural instability and recurrent falls, over a period of 10 days. She had been affected by Crohn's Disease since 1991. A CT scan failed to detect any ischemic or haemorrhagic lesion. A brain MRI revealed signs of leukoencephalopathy. Western blot analysis of her serum revealed a high titre of the onconeural antibody anti-SOX1, consistent with a neurological, cerebellar type, paraneoplastic syndrome. In spite of multiple efforts to unmask a possible underlying malignancy, no neoplastic lesion cropped up during hospitalization. Her clinical conditions progressively deteriorated, up to respiratory failure; a few days later she died, due to ensuing septic shock and Multiple Organ Failure. CONCLUSIONS: Our experience may usher and reveal a new role of anti-neural antibodies, so far reckoned an early indicator of associated malignancy, suggesting that neurological syndromes associated with such antibodies may complicate also chronic Gastrointestinal (GI) diseases. As of now, testing for anti-neuronal antibodies appeared unnecessary within the diagnostic assessment of gastroenterological disorders, which may lead to overlooking incident neurologic autoimmune diseases. Further exploration of such research hypothesis in clinical grounds appears intriguing.

Opsoclonus-myoclonus syndrome associated with pancreatic neuroendocrine tumor: a case report.

BACKGROUND: Opsoclonus-myoclonus syndrome (OMS) is a rare, immune-mediated neurological disorder. In adults, the pathogenesis can be idiopathic, post-infectious or paraneoplastic, the latter etiology belonging to the ever-expanding group of defined paraneoplastic neurological syndromes (PNS). In contrast to other phenotypes of PNS, OMS cannot be ascribed to a single pathogenic autoantibody. Here, we report the first detailed case of paraneoplastic, antibody-negative OMS occurring in association with a pancreatic neuroendocrine tumor (pNET). CASE PRESENTATION: A 33-year-old female presented with a two-week history of severe ataxia of stance and gait, dysarthria, head tremor, myoclonus of the extremities and opsoclonus. Her past medical history was notable for a metastatic pancreatic neuroendocrine tumor, and she was subsequently diagnosed with paraneoplastic opsoclonus-myoclonus syndrome. Further workup did not reveal a paraneoplastic autoantibody. She responded well to plasmapheresis, as she was refractory to the first-line therapy with corticosteroids. CONCLUSIONS: This case expands current knowledge on tumors associated with paraneoplastic opsoclonus-myoclonus syndrome and the age group in which it can occur. It further adds evidence to the effectiveness of plasmapheresis in severe cases of opsoclonus-myoclonus syndrome with a lack of response to first-line therapy.

Paraneoplastic Neurological Syndromes: Transitioning Between the Old and the New.

PURPOSE OF REVIEW: Paraneoplastic neurological syndromes (PNS) are caused by nervous system-targeting aberrant anti-tumoral immune responses. We review the updated criteria for PNS diagnosis, incorporating novel information on clinical phenotypes, neuronal autoantibodies (Nabs), and tumors. The impact of the oncologic use of immune checkpoint inhibitors (ICI) on PNS occurrence is also addressed. RECENT FINDINGS: Clinical phenotypes and Nabs are redefined as "high/intermediate/low" risk, following the frequency of cancer association. Nabs, the diagnostic hallmark of PNS, can target intracellular or surface neuronal proteins, with important prognostic and pathogenic implications. Many novel assays have been incorporated into laboratory diagnostics, that is becoming increasingly complex. ICI fight tumors, but favor autoimmunity, thus increasing the incidence of PNS-like disorders. Overcoming the old PNS criteria, the new ones are centered around the presence of tumor. Clinical presentation, Nabs, and tumor findings are translated in diagnostic scores, providing a useful tool for PNS diagnosis and management.

Paraneoplastic neurological syndrome: growing spectrum and relevance.

Paraneoplastic neurological syndromes (PNSs) are group of disorders affecting one or multiple parts of the neuroaxis associated with underlying tumors. An antibody or autoantigen-specific cell-mediated immune response against neural antigen expressed in the tumor is the potential etiology for these rare but refractory disorders. In recent years, wide variety of neurological presentations and autoantibodies has been associated with paraneoplastic autoimmunity, leading to formulation of an updated expert consensus PNS diagnostic criteria. Recognition of these phenotypes and use of serological biomarkers may aid neurologists in early diagnosis of PNS cases encountered in the inpatient or outpatient practice. In this review article, we provide an overview of various clinical, radiological, and immunopathological characteristics of PNS. Furthermore, we discuss the updated PNS criteria and increasing recognition of neurological presentations resembling the PNS among patients receiving immune checkpoint inhibitors.

Paraneoplastic Demyelinating Inflammatory Neuropathy Revealing Metastatic Seminoma: A Case Report.

Paraneoplastic neurological syndrome (PNS) is uncommon and not well known. PNS can reveal cancer, but its role in seminomas has not been described explicitly. We report the case of a 36-year-old man with unremarkable medical history and no comorbidities who was diagnosed with a retroperitoneal metastatic seminoma. The patient's general condition deteriorated, and he developed progressive neurological palsy without other clinical anomalies. Electromyography revealed demyelinating, non-lengthy neuropathy. Guillain-Barré syndrome was initially suspected. However, a positron emission tomography scan revealed a retroperitoneal mass, and blood markers revealed increased human chorionic gonadotropin. The patient was diagnosed with PNS, and a computed tomography-guided biopsy revealed a metastatic seminoma without a primary tumor. No circulating neural antibodies were detected. Human polyvalent immunoglobulin was simultaneously administered with chemotherapy. After three cycles of a cisplatin-etoposide-bleomycin, a complete biological and metabolic response rate was observed, and his neurological symptoms rapidly improved. Four years later, the patient responded completely, without any neurological complaints. Paraneoplastic demyelinating inflammatory neuropathy can lead to advanced seminoma diagnosis. Prompt management of seminomas with cisplatin-based regimens provides the best chance of cure for both advanced seminoma and paraneoplastic syndrome.

Immunomodulation in the acute phase of autoimmune encephalitis.

Autoimmune encephalitides constitute an emerging group of diseases for which the diagnosis and management may be challenging, and are usually associated with antibodies against neuroglial antigens used as biomarkers. In this review, we aimed to clarify the diagnostic approach to patients with encephalitis of suspected autoimmune origin in order to initiate early immunotherapy, and to summarize the evidence of current immunotherapies and alternative options assessed for refractory cases. Currently, the general therapeutic approach consists of steroids, IVIG, and/or plasma exchange as first-line medications, which should be prescribed once a diagnosis of possible autoimmune encephalitis is established. For patients not responding to these treatments, rituximab and cyclophosphamide are used as second-line immunotherapy. Additionally, alternative therapies, chiefly tocilizumab and bortezomib, have been reported to be useful in particularly refractory cases. Although the aforementioned approach with first and second-line immunotherapy is widely accepted, the best therapeutic strategy is still unclear since most available evidence is gathered from retrospective non-controlled studies. Moreover, several predictors of good long-term prognosis have been proposed such as response to first-line therapies, modified Rankin score lesser than 4 at the worst neurologic status, no need for admission in intensive care unit, and early escalation to second-line immunotherapy. Thus, the lack of solid evidence underlines the necessity of future well-conducted trials addressing both the best therapeutic regimen and the outcome predictors, but since autoimmune encephalitides have a relatively low incidence, international collaborations seem imperative to reach a reasonable study population size.

Granzyme B in peripheral blood mononuclear cells as a measure of cell-mediated immune response in paraneoplastic neurological syndromes and malignancy.

BACKGROUND: Paraneoplastic neurological syndromes (PNS) may coexist with ovarian or lung cancers. Some tumors coexisting with PNS are smaller and have a better prognosis than tumors without PNS. PNS may constitute an opportunity to observe a natural immune antitumor response. We aimed to investigate a cytotoxic immune response by measuring granzyme B (GrB) in peripheral blood mononuclear cells (PBMC) in patients affected with ovarian or lung malignancy, with and without accompanying PNS. METHODS: We enrolled patients with: nonmalignant lesions (n = 21), ovarian cancer (n = 19), lung cancer (n = 57), and PNS (n = 30). PBMC were isolated by density gradient centrifugation with Ficoll-Paque. We evaluated the expression of GrB in PBMC lysates by ELISA and normalized to protein content as measured by the Lowry method. RESULTS: GrB levels in PBMC in the group with malignant tumors-median 1650 pg/mg protein (interquartile range 663-3260 pg/mg) and in patients with PNS-median 1890 pg/mg protein (range 1290-2640 pg/mg) was lower than in control group with nonmalignant lesions-median 5240 pg/mg protein (range 2160-7440 pg/mg), p = 0.0003 and p = 0.0038, respectively. The differences in GrB levels in PBMC between these groups were independent of epidemiological factors-age, sex, body mass index (BMI), and the number of immune cells, as confirmed by multiple regression analysis. Within the group of patients with malignancy and PNS, GrB levels in PBMC were elevated if onconeural antibodies were detected (2610; 2390-3700 pg/mg protein) as compared to patients without antibodies (1680; 970-1880 pg/mg protein, p = 0.035). GrB in PBMC was higher if the malignancy was diagnosed at the low (3060; 2120-5220 pg/mg protein) as compared to the high stage (1330; 348-2140, p = 0.00048). In patients with lung cancer, the expression of GrB in PBMC was lower (1430; 635-2660 pg/mg protein) than in the group with ovarian cancer (2580; 1730-3730, p = 0.02). CONCLUSION: The cytotoxic response measured in peripheral blood by GrB in PBMC is impaired both in the course of malignancy and PNS. Levels of GrB in PBMC were higher if onconeural antibodies were detected. Tracking reactive immune responses, such as GrB in PBMC may have diagnostic and monitoring value in malignancy and PNS.

Contribution of Immune-Mediated Paraneoplastic Syndromes to Neurological Manifestations of Neuroendocrine Tumours: A Retrospective Study.

INTRODUCTION: Neurological symptoms associated with neuroendocrine tumours (NETs) may be related to metastatic disease or paraneoplastic syndromes (PNSs); these last are often associated with autoantibodies targeting various onconeural antigens. To better characterize neurological PNSs related to NETs, we report the largest case-series study to date. METHODS: We retrospectively reviewed the charts of all patients diagnosed with NETs of the gastrointestinal tract who presented with neurological symptoms at either of 2 tertiary academic hospitals (Henri Mondor and Beaujon, France) between 1994 and 2016. All patients underwent extensive neurological tests including clinical, laboratory, and radiological investigations. The clinical response to immunomodulating agents was recorded. RESULTS: In the 13 identified patients, the most common presentations were peripheral neuropathy (46.2%) and encephalopathy (26.6%). Of the 6 (53.3%) patients whose serum anti-neuronal antibodies were assayed, 5 had high titres. Short-term oral corticosteroid and immunosuppressant drug therapy was given to 4 of these patients, of whom 3 had a clinical response and 1 no response. Repeated high-dose intravenous immunoglobulin therapy induced a complete clinical response in 1 patient. Encephalopathy resolved fully after hepatectomy or intrahepatic chemoembolization for liver metastases in another 2 patients. DISCUSSION: The neurological symptoms associated with NETs may be due in part to autoimmune PNS. Based on experience at our 2 centres, we estimate that autoimmune PNS occurs in about 1% of patients with NETs. Early symptom recognition allows the initiation of effective treatments including corticosteroids, immunosuppressive drugs, and/or intravenous immunoglobulins.

The use of eye-movement recording in patients with anti-Hu antibody-associated paraneoplastic neurological syndromes to objectively determine extent and course of disease.

BACKGROUND AND PURPOSE: Paraneoplastic neurological syndromes with Hu-antibodies (Hu-PNS) are immune-mediated disorders in patients with malignancies, most frequently small cell lung cancer, affecting both the peripheral and central nervous system (CNS). In Hu-PNS, brainstem and cerebellar involvement are common. Here, we assessed whether eye-movement disturbances can be used for diagnosis and monitoring of CNS involvement in Hu-PNS. METHODS: Twenty-nine patients with Hu-PNS (17 females; mean age, 63.2 years,) and 14 healthy age-matched controls (seven females; mean age, 60.2 years) were included. Saccadic and smooth pursuit eye movements in response to visual stimuli were recorded with video-oculography. Eye movements were scored quantitatively (number of correction saccades, saccadic intrusions, and saccades during fixation period) and qualitatively by two eye-movement experts. In 20 patients, up to three follow-up measurements were made during subsequent hospital visits with fixed 4-week intervals. Disease course was assessed using the modified Rankin Scale. RESULTS: Eye movements were disturbed in 26 of 29 Hu-PNS patients, with horizontal eye movements being in general more impaired. Moreover, in 12 of the 14 Hu-PNS patients without clinical CNS involvement, eye movements were disturbed. Changes in eye-movement control over a period of up to 12 weeks were significantly correlated with the clinical response to treatment (ρ = 0.52, p = 0.02). CONCLUSIONS: Hu-PNS often affects eye-movement control, also in the absence of CNS signs or symptoms. Eye-movement recordings in Hu-PNS patients might be a useful tool to objectively monitor progression and treatment efficacy in Hu-PNS patients.

Central nervous system complications associated with immune checkpoint inhibitors.

OBJECTIVE: To describe the spectrum and outcome of central nervous system complications associated with immune checkpoint inhibitors (CNS-ICI). METHODS: Patients with CNS-ICI were identified and their characteristics compared with ICI-related peripheral neuropathy (PN-ICI). RESULTS: We identified 19 patients with CNS-ICI. The patients were receiving nivolumab (n=8), pembrolizumab (n=6), a combination of ipilimumab-nivolumab (n=3), ipilimumab-durvalumab (n=1), or atezolizumab (n=1). Underlying malignancies included non-small-cell lung cancer (n=8), melanoma (n=3), and other less common tumours (n=8). Neurological phenotypes were limbic encephalitis (n=8), meningoencephalitis (n=4) and cerebellitis (n=4). Two patients developed isolated confusion and one parkinsonism. Associated autoantibodies included onconeural (Ma2, n=7; Hu, n=1), astrocytic (glial fibrillar acidic protein, n=2) and neuronal surface (contactin-associated protein-like 2, n=1) specificities. ICIs were withheld and corticosteroid treatment was given in all cases. Five patients received intravenous immunoglobulin, two rituximab, one plasmapheresis and one infliximab. Overall, six patients died. Readministration of ICI was attempted in three patients, without further relapses. Non-small-cell lung cancer was significantly more frequent in patients with CNS-ICI (p<0.01), while melanoma and ipilimumab treatment were more common in PN-ICI (p<0.01 and p=0.01). Conversely, CNS-ICI cases were more frequently antibody-positive than PN-ICI (p<0.01) and showed a strong trend towards poorer outcome (p=0.053). CONCLUSION: Three main clinical phenotypes characterise CNS complications of ICIs, each with distinct immunological background, disease course and response to treatment. Other clinical manifestations (including parkinsonism and steroid-responsive confusion) are also possible. Underlying cancers, antibody prevalence and outcome appear different from those of patients with PN-ICI.

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.

A large screen for paraneoplastic neurological autoantibodies; diagnosis and predictive values.

BACKGROUND: Paraneoplastic neurological syndromes (PNS) are a group of syndromes that affect the central and peripheral neuromuscular system in association with cancer. Specific antibodies may assist in the diagnosis of PNS. The antibodies tested can be classified into those directed against intracellular neuronal proteins ("well characterized" PNS: Hu, Yo, RI, CV2, amphiphysin, Ma1, Ma2) and those directed against neural surface antigens (autoimmune encephalitis syndromes: NMDA, AMPA, LGI1, CASPR2, GABAR). We aimed to characterize patients with unexplained neuropsychiatric symptoms, in whom positive PNS antibodies were detected in the Sheba medical center, a large referral hospital. METHODS: Clinical and demographic data of patients with positive PNS antibodies were collected during the years 2002-2016. Antibodies were tested by either Line immunoassay or by cell-based indirect immunofluorscent assay. RESULTS: During the follow up of 14 years, 4010 PNS tests were performed in patients with unexplained neuropsychiatric symptoms. Seventy-two were found to be positive; among them we had full clinical data access to 44. The most frequent antibodies were anti-Hu (31.8%), anti-Yo (18.2%), anti-CV2 (13.6%), and anti-NMDA (9.1%), and the most common cancers were small-cell lung (SCLC) and ovarian cancers. In the well characterized paraneoplastic group, cancer was diagnosed in 55.9% of the patients, and in the autoimmune encephalitis group, 40.0% were diagnosed with cancer. A positive correlation between antibody titer and the presence of cancer was found. Ninety percent of the tests in patients who were found positive were ordered by a neurologist or neuro-oncologist. CONCLUSIONS: The titers of PNS auto-antibodies can predict cancer in patients whom anti-PNS antibodies are tested. In addition, consultation with a specialist should be considered before this test is ordered.

Neuronal autoantibodies associated with cognitive impairment in melanoma patients.

BACKGROUND: Cancer-related cognitive impairment is an important complication in cancer patients, yet the underlying mechanisms remain unknown. Over the last decade, the field of paraneoplastic neurological syndromes has been dramatically changed by the discovery of new neuronal autoantibodies, some of them associated with cognitive impairment. We aimed to assess the prevalence of neuronal autoantibodies in melanoma patients and their association with neurological and cognitive dysfunction. PATIENTS AND METHODS: A total of 157 consecutive melanoma patients with a median age of 63 years were recruited at the Department of Dermatology, Charité-Universitätsmedizin Berlin and tested for neuronal autoantibodies. A comprehensive neuropsychological assessment was carried out in a selected subgroup of 84 patients after exclusion of patients with confounding factors for a cognitive dysfunction, including brain metastases, relevant medication, and neurological disorders. RESULTS: Neuronal autoantibodies were found in 22.3% of melanoma patients. The most frequent antibodies were IgA/IgM anti-NMDAR antibodies. Applying the International Cognition and Cancer Task Force criteria, 36.9% had cognitive impairment, however, with a threefold higher odds in antibody-positive compared with antibody-negative patients (57.1% versus 30.2%, OR = 3.1, 95% CI: 1.1 to 8.6; P = 0.037). In patients with anti-NMDAR antibodies, this impairment increased with higher antibody titers (P = 0.007). Antibody-positive patients had a significantly impaired overall cognitive performance (z-value: -0.38 ± 0.69 versus 0.00 ± 0.56; P = 0.014) as well as significant impairments in tests of memory, attention, and executive function. In a multiple linear regression analysis, autoantibodies were an independent risk factor for cognitive impairment (B = -0.282; 95% CI: -0.492 to -0.071; P = 0.009). Autoantibody seropositivity was associated with immune checkpoint inhibitor treatment and a history of autoimmune diseases. CONCLUSIONS: A large number of melanoma patients harbor neuronal autoantibodies that are associated with significant cognitive impairment affecting memory, attention, and executive function. Neuronal autoantibodies might represent a pathophysiological factor and possible biomarker in the development of cancer-related cognitive impairment.

Autoimmune response in lung cancer patients with neurological paraneoplastic syndromes.

AIM OF THE STUDY: The aim of this study was to evaluate granzyme B, perforin and FasL expression in peripheral blood mononuclear cells (PBMCs) in lung cancer patients and in paraneoplastic neurological syndromes (PNS). CLINICAL RATIONALE FOR THE STUDY: Cellular immune response is activated as part of anti-tumour reaction of the malignancy-bearing host. Paraneoplastic neurological syndromes (PNS) are defined as indirect effects of cancer on the nervous system and are considered immune-mediated. Such stimulation of the immune system may limit the aggressiveness of cancer and the development of metastasis, and thereby improve survival. Granzyme B and perforin pathway, and Fas ligand (FasL) - Fas receptor interaction play an important role in cytotoxic response. MATERIALS AND METHODS: Fifty-two patients were included in the study: 28 subjects with PNS and 24 subjects with lung cancer. PNS cases were diagnosed according to the Graus criteria. The presence of onconeural antibodies (anti-Hu/anti-Ri/anti-Yo/anti-Ma/Ta/anti-CV2/anti-amphiphysin/anti-myelin/anti-neuroendothelium/anti-MAG/anti-GAD) was detected with indirect immunofluorescence and confirmed with Line Blotting. The expression of granzyme B, perforin and FasL was detected in PBMCs with ELISA. RESULTS: PPBMC-FasL expression was increased in lung cancer compared to other patient groups. The granzyme to FasL ratio was significantly higher in lung cancer patients with peripheral than with central PNS involvement. In a multiple regression model, sex was an independent factor influencing PBMC expression of granzyme and perforin. CONCLUSIONS: FasL expression in PBMCs is up-regulated in lung cancer patients. The interplay between granzyme B and FasL may be involved in the development of PNS at the level of the peripheral and the central nervous systems in different manners. Gender is associated with PBMC expression of granzyme B and perforin in lung cancer patients. CLINICAL IMPLICATIONS: The novel findings that we report broaden the current knowledge on PNS pathomechanism, with aspects that have not been previously explored. Our findings provide a rationale for further exploration of the granzyme B/FasL pathway with regards to its potential diagnostic value. However, our study is preliminary and needs further research, especially in the context of the prognostic value of the proposed markers.

Updates in the Diagnosis and Treatment of Paraneoplastic Neurologic Syndromes.

The disorders of the central nervous system associated with cancer by remote immune-mediated mechanisms are a heterogeneous group. These disorders encompass the classic paraneoplastic disorders and the recently recognized autoimmune encephalitis associated with antibodies against neuronal cell surface or synaptic proteins that occur with or without cancer association. In the last decade, the new surge of interest in neuronal diseases associated with anti-neuronal antibodies led to the rapid discovery of new forms of disease that have different manifestations and were not previously suspected to be immune mediated. The recognition of these syndromes is important because it may lead to early detection of an underlying malignancy and prompt initiation of treatment, improving chances for a better outcome.