Mechanisms of immune tolerance breakdown in paraneoplastic neurological syndromes.

Paraneoplastic neurological syndromes (PNS) are rare autoimmune disorders triggered by the presence of a cancer. The autoimmunity is herein directed against proteins expressed both in the tumor and in the nervous system, namely the onconeural antigens, against which are directed specific autoantibodies, each of them characterizing a neurological syndrome. The mechanisms of the immune tolerance breakdown in PNS leading to the production of specific autoantibodies directed against the nervous system and leading to the immune attack begins to be explained. Each syndrome is associated with a specific histo-molecular subtype of tumor suggesting a link between the PNS genesis and oncogenesis. The expression of the onconeural antigen by these tumors is insufficient to explain the immune tolerance breakdown. In some PNS tumors, alterations of the antigen have been identified: mutations, gene copy number variation and overexpression of transcript and protein. But in others PNS, no such molecular alterations of the onconeural antigens have been demonstrated. In these cases, other mechanisms of neoantigen generation that may be involved remain to be deciphered. Cancer outcomes of PNS tumors are also characterized by the high frequency of lymph node metastasis at diagnosis. At the primary tumor site, the antitumor immune reaction seems to be particularly intense and characterized by a prominence of B-cell and Ig-secreting plasma cells that may generate the autoantibody secretion. The immune control mechanisms leading to such organization of the immune attack are not known to date. Renewed research efforts are thus needed to better understand the mechanism of immune tolerance breakdown in each PNS and determine potential targets to meet the therapeutic challenges posed by these rare disorders.

A case of corticobasal syndrome possibly associated with anti-Yo antibodies.

INTRODUCTION: Corticobasal syndrome (CBS) is a rare form of atypical parkinsonism, most commonly caused by neurodegenerative disorders. Autoimmune underlying conditions are extremely rare, and anti-Yo antibody-associated CBS has not been reported yet. CASE REPORT: Herein, we describe a case of a 68-year-old woman presenting with progressive dysarthria, gait instability and difficulty using her left hand with subacute deterioration during the last 3 months. Neurological examination revealed asymmetrical parkinsonism and pyramidal syndrome, reflex myoclonus and dystonia of her left upper limb, accompanied by apraxia of her left lower limb, fulfilling the criteria for possible CBS. Neuroimaging showed asymmetric frontoparietal atrophy, while cerebrospinal fluid and dopamine transporter imaging were normal. Prior to our evaluation, antineuronal autoantibody testing indicated positive anti-Yo antibodies. There was mild improvement after second IVIG cycle, and further investigation revealed no tumor. CONCLUSION: Although autoimmune etiology of this case cannot be certain, it highlights the potential expansion of the clinical spectrum of anti-Yo-associated paraneoplastic syndrome.

Opercular myoclonic-anarthric status (OMASE) secondary to anti-Hu paraneoplastic neurological syndrome.

Focal Opercular Myoclonic - Anarthric Status Epilepticus (OMASE) is a rare form of focal motor status epilepticus caused by several etiologies. It is characterized by fluctuating dysarthria and epileptic myoclonus involving the bilateral glossopharyngeal musculature. We present the case of a 52-year-old woman who experienced gradual and progressive paralysis and myoclonus of facial and bulbar muscles; additional tests revealed the presence of right breast ductal adenocarcinoma and positive serum anti-Hu and anti-GAD65 antibodies. High doses of steroid pulses, anti-seizure therapy, and rituximab partially controlled myoclonus; the tumor resection improved dysphagia and dysarthria.

Anti-RGS8 paraneoplastic cerebellar ataxia is preferentially associated with a particular subtype of Hodgkin's lymphoma.

Ataxia with anti-regulator of G-protein signaling 8 autoantibodies (RGS8-Abs) is an autoimmune disease recently described in four patients. The present study aimed to identify other patients with RGS8-Abs, describe their clinical features, including the link between RGS8-related autoimmune cerebellar ataxia (ACA) and cancer. Patients with RGS8-Abs were identified retrospectively in the biological collections of the French Reference Center for Paraneoplastic Neurological Syndrome and the University of California San Francisco Center for Encephalitis and Meningitis. Clinical data were collected, and cerebrospinal fluid, serum, and tumor pathological samples were retrieved to characterize the autoantibodies and the associated malignancies. Only three patients with RGS8-Abs were identified. All of them presented with a pure cerebellar ataxia of mild to severe course, unresponsive to current immunotherapy regimens for ACA. Two patients presented with a Hodgkin lymphoma of the rare specific subtype called nodular lymphocyte-predominant Hodgkin lymphoma, with very mild extension. Autoantibodies detected in all patients enriched the same epitope on the RGS8 protein, which is an intracellular protein physiologically expressed in Purkinje cells but also ectopically expressed specifically in lymphoma cells of patients with RGS8-related ACA. The present results and those of the four cases previously described suggest that RGS8-Abs define a new paraneoplastic neurological syndrome of extreme rarity found mostly in middle-aged males that associates pure cerebellar ataxia and a particular lymphoma specifically expressing the RGS8 antigen. As in other paraneoplastic ACA with intracellular antigen, the disease course is severe, and patients tend to exhibit a poor response to immune therapy.

Cancer-associated neuromyelitis optica spectrum disorder: a case report with literature review.

Neuromyelitis optica spectrum disorders (NMOSD) is one of autoimmune inflammatory diseases and is characterized by area postrema syndrome, brainstem syndrome, optic neuritis, and/or myelitis. Typical myelitis is longitudinally extended transverse myelitis (LETM) which extends over three vertebral bodies. Several previous case reports have suggested association between cancer and NMOSD. A 50-year-old woman had breast cancer and underwent mastectomy and, 10 months later, she had developed acutely progressive dysbasia. Spine MRI showed LETM in 13 vertebrae length and blood test revealed positive anti-aquaporin 4 (anti-AQP4) antibody based on enzyme-linked immunosorbent assay with index of over 40. She was treated by intravenous methylprednisolone, plasma exchange, and intravenous immunoglobulin, followed by oral prednisolone. The condition had mostly recovered after the treatment. A small population of NMOSD has the aspect of paraneoplastic neurological syndrome. The age of onset in patients with cancer-associated NMOSD tends to be higher than that in individuals with NMOSD due to any causes of NMOSD.

Significant improvement in paraneoplastic neurological syndromes without identifiable anti-neural antibodies in patients with breast cancer after breast surgery.

Paraneoplastic neurological syndromes (PNS) are neurological disorders that occur in close association with tumors without direct metastasis or invasion of the tumors and in which anti-neural antibodies may be present. Cerebellar ataxia is a common form of PNS in patients with breast cancer. However, reports of symptom improvement with breast cancer treatment are more common in patients with positive anti-neural antibodies and are rarely seen in those with negative anti-neural antibodies. In addition, there have been few quantitative evaluations of symptom improvement. We report a case in which neurological symptoms significantly improved after surgical treatment for breast cancer. The patient was a 78-years-old woman with subacute progressive cerebellar ataxia. A subsequent diagnosis of breast cancer led to the diagnosis of "PNS probable". A comprehensive search for anti-neural antibodies was negative in all cases. The quantitative index of the Scale for the Assessment and Rating of Ataxia (SARA) score, a standard evaluation method for ataxia in spinocerebellar degeneration, improved after breast cancer surgery. This case may provide a rationale for treating breast cancer patients negative for anti-neural antibodies, with the possibility of improving neurological symptoms.

Trismus as the Initial Presentation of Anti-Hu Paraneoplastic Neurological Syndrome.

A 73-year-old man presented with subacute trismus and pancerebellar dysfunction. Brain imaging and routine blood test results were unremarkable. Chest computed tomography revealed an indistinctly enhancing 4.7 × 2.5 × 1.8-cm3 pulmonary mass in the right upper lung, with enlarged right paratracheal and hilar lymph nodes. Biopsy of the right supraclavicular lymph node confirmed metastatic carcinoma, with differential diagnoses of small cell carcinoma and poorly differentiated carcinoma, indicating lung cancer as the primary source. Paraneoplastic immunohistochemistry screening revealed anti-Hu antibodies in the serum at a titer of 1:7680 (normal range <1:240) and in the cerebrospinal fluid (CSF) at a titer of 1:256 (normal range <1:2). The line blot method yielded positive results for anti-Zic4 antibodies in serum, with a titer of >1:10 (normal range <1:10), whereas CSF anti-Zic4 was negative (normal range <1:2). The patient developed non-responsive hospital-acquired pneumonia and respiratory failure, and discharged himself against medical advice. This rare case indicates that trismus can be an initial manifestation of anti-Hu paraneoplastic neurological syndrome, and emphasizes the importance of clinical awareness.

Gait instability, ophthalmoplegia, and chorea with orofacial dyskinesia in a man with anti-Ri antibodies: a case report.

A 79-year-old man was admitted for 2 weeks of dizziness, followed by diplopia, involuntary movement and progressive gait disturbances. Neurologic examination revealed horizontal and vertical gaze paresis, bilateral choreiform movement with orofacial dyskinesia, and limb/truncal ataxia. MRI revealed fluid-attenuated inversion recovery image-hyperintense signal abnormalities in the dorsal midbrain, pontine and medulla. Within another few days, the patient developed type II acute respiratory failure requiring artificial invasive ventilation. Because autoimmune encephalitis was suspected, he received intravenous immunoglobulin therapy followed by intravenous methylprednisolone, but only his ophthalmoplegia improved minimally. Serological tests were positive for anti-Ri onconeural antibodies. CT-guided mediastinal lymph node biopsy was performed and revealed small cell lung carcinoma. We report the rare manifestation of anti-Ri antibody-associated paraneoplastic neurological syndrome (PNS), and this case can alert us to the importance of respiratory management in this diverse neurologic disease. Furthermore, PNSs positive for anti-Ri antibodies should be added to the list of differential diagnoses of chorea with orofacial dyskinesia.

Overview of treatment strategies in paraneoplastic neurological syndromes.

Treatment strategies in paraneoplastic neurological syndromes rely on the three pillars of tumor treatment, immunotherapy, and symptomatic treatment, the first one being by far the most important in the majority of patients and syndromes. Classically, antibodies against extracellular antigens are directly pathogenic, and patients with these syndromes are more responsive to immunomodulatory or immunosuppressive treatments than the ones with antibodies against intracellular targets. This chapter first discusses some general principles of tumor treatment and immunotherapy, followed by a closer look at specific treatment options for different clinical syndromes, focusing on symptomatic treatments.

Inflammatory sensory neuronopathies.

Inflammatory sensory neuronopathies are rare disorders mediated by dysimmune mechanisms targeting sensory neurons in the dorsal root ganglia. They constitute a heterogeneous group of disorders with acute, subacute, or chronic courses, and occur with cancer, systemic autoimmune diseases, notably Sjögren syndrome, and viral infections but a noticeable proportion of them remains isolated. Identifying inflammatory sensory neuronopathies is crucial because they have the potential to be stabilized or even to improve with immunomodulatory or immunosuppressant treatments provided that the treatment is applied at an early stage of the disease, before a definitive degeneration of neurons. Biomarkers, and notably antibodies, are crucial for this early identification, which is the first step to develop therapeutic trials.

Paraneoplastic Cerebellar Degeneration Leading to an Early Diagnosis of Peritoneal Serous Papillary Carcinoma.

A 77-year-old female with a subacute progression of ataxia and serum anti-Yo antibodies was suspected to have paraneoplastic cerebellar degeneration (PCD). An examination of an underlying cancer showed no abnormality in the gynecological organs, but the findings did show a mass in the Douglas fossa. The mass was resected and diagnosed as stage IIB peritoneal serous papillary carcinoma (PSPC), a rare gynecologic cancer that is difficult to diagnose in the early stages. PCD was treated with intravenous immunoglobulin (IVIG). For an early diagnosis and treatment, PSPC should be included in the list of malignancies that cause PCD with anti-Yo antibodies.

Autoimmune Movement Disorders Complicating Treatment with Immune Checkpoint Inhibitors.

BACKGROUND: Immune checkpoint inhibitors (ICI) may trigger autoimmune neurological conditions, including movement disorders (MD). OBJECTIVES: The aim of this study was to characterize MDs occurring as immune-related adverse events (irAEs) of ICIs. METHODS: A systematic literature review of case reports/series of MDs as irAEs of ICIs was performed. RESULTS: Of 5682 eligible papers, 26 articles with 28 patients were included. MDs occur as a rare complication of cancer immunotherapy with heterogeneous clinical presentations and in most cases in association with other irAEs. Inflammatory basal ganglia T2/fluid attenuated inversion recovery abnormalities are rarely observed, but brain imaging is frequently unrevealing. Cerebrospinal fluid findings are frequently suggestive of inflammation. Half of cases are associated with a wide range of autoantibodies. Steroids and ICI withdrawal usually lead to improvement, even though some patients experienced relapses or a severe clinical course. CONCLUSION: MDs are a rare complication of ICIs that should be promptly recognized to offer patients a correct diagnosis and treatment.

Overview of Paraneoplastic Autoantibody-Mediated Cognitive Impairment and Behavioral Changes: A Narrative Review.

Cognitive dysfunction and behavioral change can be some of the manifestations of cancer, occurring as a part of paraneoplastic neurological syndrome, most commonly in small cell lung cancer. Paraneoplastic limbic encephalitis is the leading cause of cognitive disturbance and abnormal behavior in paraneoplastic syndromes, which is usually autoantibody-mediated. Autoantibodies are the main contributors to the development of cognitive dysfunction and behavioral change in cancer patients, with studies suggesting a higher liability for antibody-positive cancer patients to be affected. Anti-NMDAR and anti-AMPAR are antibodies targeted against surface antigens, manifesting predominantly as memory disturbance, abnormal behavior, psychiatric symptoms, and seizures. Other surface antigen-targeted antibodies include anti-GABA, anti-CASPR2, and anti-LGI1, which were shown to have cognitive function impairment and abnormal behavior as some of the main presentations, predominantly affecting memory. Cognitive deterioration and changes in behavior were also relatively common with some of the intracellular antigen-targeted antibodies, including anti-Hu, anti-SOX1, anti-PCA2, and anti-Zic2. Affected behavior and cognition, however, were reported less commonly in other paraneoplastic antibodies against intracellular antigens (anti-Yo, anti-GAD, anti-Ma2, anti-Ri, anti-CV2, and anti-KLHL11). Our article will provide a comprehensive review of the clinical manifestations of cognitive impairment and behavioral changes among cancer patients who develop paraneoplastic syndrome. Additionally, this review will discuss the role of specific paraneoplastic autoantibodies and the clinical spectrum linked to each separately.

Breast cancer's hidden partner: meningoencephalitis as a paraneoplastic revelation: a rare presentation of invasive ductal carcinoma of breast: a case report.

Introduction and importance: Paraneoplastic neurologic syndromes encompass a group of neurologic disorders arising from pathological processes unrelated to metastasis, metabolic disturbances, infections, coagulopathy, or treatment-related side effects. These syndromes can affect various regions of the nervous system, resulting in diverse clinical manifestations. Case presentation: The authors present a rare case of anti-amphiphysin-associated meningoencephalitis in a South Asian Pakistani woman. Initially, the patient was managed for suspected infectious meningitis, but empirical treatment failed to yield improvement. Subsequent investigations unveiled a paraneoplastic syndrome secondary to breast cancer. Discussion: Diagnosing these clinical entities is challenging due to their multifaceted presentations, often leading to delayed identification, increased patient suffering, economic burdens, and preventable complications. Conclusion: Anti-amphiphysin-associated meningoencephalitis is a rare manifestation of paraneoplastic syndromes. It is crucial to raise awareness among healthcare professionals about the diverse presentations of paraneoplastic syndromes.

Autonomic nervous system involvement in autoimmune encephalitis and paraneoplastic neurological syndromes.

In autoimmune neurological diseases, the autonomic nervous system can be the primary target of autoimmunity (e.g. autoimmune autonomic ganglionopathy), or, more frequently, be damaged together with other areas of the nervous system (e.g. Guillain-Barré syndrome). Patients with autoimmune encephalitis and paraneoplastic neurological syndromes (PNS) often develop dysautonomia; however, the frequency and spectrum of autonomic signs and symptoms remain ill defined except for those scenarios in which dysautonomia is a core feature of the disease. Such is the case of Lambert-Eaton myasthenic syndrome, Morvan syndrome or anti-NMDAR encephalitis; in the latter, patients with dysautonomia have been reported to carry a more severe disease and to retain higher disability than those without autonomic dysfunction. Likewise, the presence of autonomic involvement indicates a higher risk of death due to neurological cause in patients with anti-Hu PNS. However, in anti-Hu and other PNS, as well as in the context of immune checkpoint inhibitors' toxicities, the characterization of autonomic involvement is frequently overshadowed by the severity of other neurological symptoms and signs. When evaluated with tests specific for autonomic function, patients with autoimmune encephalitis or PNS usually show a more widespread autonomic involvement than clinically suggested, which may reflect a potential gap of care when it comes to diagnosing dysautonomia. This review aims to revise the autonomic involvement in patients with autoimmune encephalitis and PNS, using for that purpose an antibody-based approach. We also discuss and provide general recommendations for the evaluation and management of dysautonomia in these patients.

Small-cell Lung Carcinoma with Gastrointestinal Pseudo-obstruction as a Paraneoplastic Neurological Syndrome Elicited by an Immune Checkpoint Inhibitor.

Gastrointestinal pseudo-obstruction (GIPO) is a phenotype of the paraneoplastic neurological syndrome (PNS). We herein report a case of small-cell lung carcinoma (SCLC) with GIPO elicited by an immune checkpoint inhibitor (ICI). A 75-year-old man with SCLC developed intractable intestinal obstruction after receiving one course of anticancer drugs (durvalumab, etoposide, and carboplatin). The serum anti-Hu antibody (Hu-Ab) was positive, and the patient was diagnosed with GIPO. Corticosteroid treatment did not improve the GIPO, and the patient died. There are few reports of GIPO after ICI treatment in patients with lung cancer, so a further investigation will be required to elucidate the mechanism by which ICIs elicit PNS. Checking for neuronal antibodies may help identify patients with SCLC who are at risk of developing PNS due to ICI treatment.

A Case of Paraneoplastic Neurological Syndrome Leading to the Diagnosis of Large Cell Neuroendocrine Carcinoma From Opsoclonus-Myoclonus Syndrome.

Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder characterized by myoclonus, ataxia, and tremors. It can be classified as neoplastic or idiopathic, with small cell lung cancer being commonly associated. Herein, we present a rare case of refractory paraneoplastic neurological syndrome (PNS) caused by large cell neuroendocrine carcinoma (LCNEC), a rare form of non-small cell lung cancer (NSCLC). A 60-year-old otherwise healthy man presented with acute-onset dysarthria, gait instability, and numbness on the right side of his body. According to the clinical symptoms and neurological examination, we initially suspected cerebellar infarction; however, brain imaging revealed no abnormal findings. After a few days, the patient developed worsening horizontal nystagmus, irregular ocular rhythms, and generalized involuntary movements, indicative of OMS. A systemic evaluation revealed a solitary nodule in the lower lobe of the right lung, leading to a clinical diagnosis of PNS. The patient underwent segmentectomy to treat an early-stage LCNEC nodule after one month from onset. Despite all therapeutic interventions, OMS was refractory, and after consulting with the person himself and the family, palliative care was selected. However, the patient showed a clinical response belatedly five months after surgery. This case highlights the importance of considering PNS, and that it may be associated with a rare malignancy when cerebellar symptoms are observed, and the challenges in managing refractory PNS associated with rare forms of NSCLC.

Anti-Kelch-like protein 11 antibody encephalitis: a case report and literature review.

Anti-Kelch-like protein 11 (KLHL11) antibody encephalitis is a rare clinical condition characterized by autoimmune-mediated encephalomyelitis associated with the presence of KLHL11 antibodies. Diagnosis requires the detection of serum and cerebrospinal fluid anti-KLHL11 antibodies, while immunotherapy serves as the principal treatment approach. This paper presents a case report highlighting the emergence of anti-KLHL11 antibody encephalitis. A 66-year-old male patient presented with seizures, impaired cognitive function, disturbance of consciousness, apathy, hypologia, dysphoria, and ataxia. Serum and cerebrospinal fluid (CSF) were identified as positive for anti-KLHL11 antibodies, leading to a diagnosis of autoimmune encephalitis associated with KLHL11 antibodies. After treatment with glucocorticoid, the patient did not experience further convulsions and recovered consciousness, with improved cognitive function. Tumor screening suggested the presence of an underlying malignancy. The clinical manifestations of anti-KLHL11 antibody encephalitis vary widely, and timely identification and treatment can improve prognosis.

A Case of Anti-Ma2 Encephalitis Presenting with Pendular Torsional Nystagmus.

Antibodies against the neuronal protein Ma2 have been reported in a peculiar form of paraneoplastic encephalitis with prominent involvement of the limbic, brainstem, and diencephalic structures and usually associated with germ cell testicular, lung, or breast cancer. The diagnosis is frequently challenged by atypical clinical manifestations including parkinsonism, sleep disturbances, hypothalamic-pituitary dysfunctions, and motor neuron-like syndrome. In recent years, the advent of monoclonal antibodies targeting immune checkpoints has deeply changed the treatment of different tumors, especially melanoma and lung cancer. However, given their nature, an increasing number of neurological immune-related adverse events, including ocular motor abnormalities, have been described. Here, we report a woman with advanced non-small cell lung cancer treated with anti-PD-L1 durvalumab, presenting with an isolated pendular torsional nystagmus, in association with anti-Ma2 antibodies. This peculiar case widens our knowledge on the clinical presentation of anti-Ma2 encephalitis associated with checkpoint inhibitors.