Paraneoplastic chorea associated with CRMP-5 neuronal antibody and lung carcinoma

Autoimmune encephalitis: Early and late findings on serial MR imaging and correlation to treatment timepoints

Introduction

MRI is negative in a large percentage of autoimmune encephalitis cases or lacks findings specific to an antibody. Even rarer is literature correlating the evolution of imaging findings with treatment timepoints. We aim to characterize imaging findings in autoimmune encephalitis at presentation and on follow up correlated with treatment timepoints for this rare disease.

Methods

A full-text radiological information system search was performed for "autoimmune encephalitis" between January 2012 and June 2022. Patients with laboratory-identified autoantibodies were included. MRI findings were assessed in correlation to treatment timepoints by two readers in consensus. For statistical analysis, cell-surface vs intracellular antibody groups were assessed for the presence of early limbic, early extralimbic, late limbic, and late extralimbic findings using the χ2 test.

Results

Thirty-seven patients (female n = 18, median age 58.8 years; range 25.7 to 82.7 years) with 15 different autoantibodies were included in the study. Twenty-three (62%) patients were MRI-negative at time of presentation; 5 of these developed MRI findings on short-term follow up. Of the 19 patients with early MRI findings, 9 (47%) demonstrated improvement upon treatment initiation (7/9 cell-surface group). There was a significant difference (p = 0.046) between the MRI spectrum of cell-surface vs intracellular antibody syndromes as cell-surface antibody syndromes demonstrated more early classic findings of limbic encephalitis and intracellular antibody syndromes demonstrated more late extralimbic abnormalities.

Conclusion

MRI can be used to help narrow the differential diagnosis in autoimmune encephalitis and can be used as a monitoring tool for certain subtypes of this rare disease.

A case of immunotherapy-responsive autoimmune hemichorea

INTRODUCTION

Subacute adult-acquired hemichorea is a striking presentation with a broad differential, including ischemic, metabolic, and inflammatory causes.

CASE

We encountered a 74-year-old woman with rapid onset of hemichorea and associated encephalopathy. Following a thorough workup without identification of clear imaging or laboratory abnormalities, we empirically treated with IVIg. Her hemichorea dramatically improved. Due to relapses of hemichorea, she required repeat immunotherapy with IVIg or high dose steroids followed by maintenance mycophenolate.

DISCUSSION

This case of seronegative autoimmune hemichorea highlights the importance of a high index of suspicion for an inflammatory etiology of chorea when other causes are ruled out and performing an immunotherapy trial.

Recent advances in non-Huntington's disease choreas

INTRODUCTION

Chorea is primarily due to an imbalance of basal ganglia output pathways, often due to dysfunction or degeneration of the caudate nucleus and putamen, and can be due to many causes.

METHODS

We reviewed the recent literature to identify newly-recognized causes of chorea, including auto-immune, metabolic, and genetic. We also focused upon developments in mechanisms relating to underlying pathophysiology of certain genetic choreas and advances in therapeutics.

RESULTS

Novel autoantibodies continue to be identified as causes of chorea. Both COVID-19 infection and vaccination are reported to result rarely in chorea, although in some cases causality is not clearly established. Advances in genetic testing continue to find more causes of chorea, and to expand the phenotype of known genetic disorders. Deep brain stimulation can be successful in certain circumstances.

CONCLUSION

Our understanding of mechanisms underlying this movement disorder continues to advance, however much remains to be elucidated.

Lung Cancer Wherein Durvalumab Induced Both Anti-CRMP-5 Antibody-related Paraneoplastic Neurological Syndromes and Neurological Adverse Events

A 68-year-old man with small-cell lung cancer developed anti-collapsin response-mediator protein (CRMP)-5 antibody-related paraneoplastic neurological syndrome (PNS) presenting with ataxia and chorea during treatment with durvalumab. As a result of steroid therapy, anti-CRMP-5 antibodies became negative, hyperintense lesions on brain magnetic resonance imaging disappeared, and neurological symptoms improved. After resuming durvalumab, he became unable to walk due to neurological adverse events (nAEs). There have been no reported cases manifesting PNSs and nAEs as a result of the same immune checkpoint inhibitors (ICIs) administered at different times. Resuming ICIs in patients diagnosed with PNSs should be performed with prudence.

Paraneoplastic movement disorders

Paraneoplastic movement disorders are diverse autoimmune neurological illnesses occurring in the context of systemic cancer, either in isolation or as part of a multifocal neurological disease. Movement phenomena may be ataxic, hypokinetic (parkinsonian), or hyperkinetic (myoclonus, chorea, or other dyskinetic disorders). Some disorders mimic neurodegenerative or hereditary illnesses. The subacute onset and coexisting nonclassic features of paraneoplastic disorders aid distinction. Paraneoplastic autoantibodies provide further information regarding differentiating cancer association, disease course, and treatment responses. A woman with cerebellar ataxia could have metabotropic glutamate receptor 1 autoimmunity, in the setting of Hodgkin lymphoma, a mild neurological phenotype and response to immunotherapy. A different woman, also with cerebellar ataxia, could have Purkinje cytoplasmic antibody type 1 (anti-Yo), accompanying ovarian adenocarcinoma, a rapidly progressive phenotype and persistent disabling deficits despite immune therapy. The list of antibody biomarkers is growing year-on-year, each with its own ideal specimen type for detection (serum or CSF), accompanying neurological manifestations, cancer association, treatment response, and prognosis. Therefore, a profile-based approach to screening both serum and CSF is recommended. Immune therapy trials are generally undertaken, and include one or more of corticosteroids, IVIg, plasma exchange, rituximab, or cyclophosphamide. Symptomatic therapies can also be employed for hyperkinetic disorders.

Hematologic malignancies and hematopoietic stem cell transplantation

Paraneoplastic neurologic syndromes are rarely associated with hematologic malignancies. In their rarity, lymphomas are the diseases with more frequent paraneoplastic neurologic syndrome. High-risk antibodies are absent in most lymphoma-associated paraneoplastic neurologic syndromes, with the exception of antibodies to Tr/DNER in paraneoplastic cerebellar degeneration, mGluR5 in limbic encephalitis, and mGluR1 in some cerebellar ataxias. Peripheral nervous system paraneoplastic neurologic syndromes are rare and heterogeneous, with a prevalence of demyelinating polyradiculoneuropathy in non-Hodgkin lymphoma. Polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin changes (POEMS) is a rare, paraneoplastic syndrome due to an underlying plasma cell disorder. The diagnosis is based on defined criteria, and vascular endothelial growth factor (VEGF), not an antibody, is considered a reliable diagnostic marker that also mirrors therapy response. As with the paraneoplastic neurologic syndromes in solid tumors, therapies rely on cancer treatment associated with immunomodulatory treatment with better response in PNS with antibodies to surface antigens. The best outcome is generally present in Ophelia syndrome/limbic encephalitis with anti-mGluR5 antibodies, with frequent complete recovery. Besides patients with isolated osteosclerotic lesions (where radiotherapy is indicated), hematopoietic stem-cell transplantation is the therapy of choice in patients with POEMS syndrome. In the paraneoplastic neurologic syndromes secondary to immune checkpoint inhibitors, discontinuation of the drug together with immunomodulatory treatment is recommended.

Clinical approach to diagnosis of paraneoplastic neurologic syndromes

The correct diagnosis of a paraneoplastic neurologic syndrome (PNS) first requires the identification of the syndrome as one of those defined as high-risk (previously called classical) or intermediate-risk for cancer in the 2021 PNS diagnostic criteria. Testing for neuronal antibodies should be restricted to these syndromes as indiscriminate request decreases the diagnostic value of the antibodies. Identifying onconeural (high-risk for cancer) or intermediate-risk for cancer antibodies supports the paraneoplastic diagnosis and mandates the search for an underlying cancer. Tumor screening must follow the published guidelines. Repeated screening is indicated in neurologic syndromes with onconeural antibodies and patients with high-risk for cancer neurologic syndromes unless they present neuronal antibodies which are not associated with cancer. Neuronal antibodies should be screened by immunohistochemistry and confirmed by immunoblot (intracellular antigens) or cell-based assay (CBA) (surface antigens). Positive results only by immunoblot or CBA should be taken with caution. Although the 2021 diagnostic criteria for PNS do not capture all PNS, as they do not allow to diagnose definite PNS neurologic syndromes without neuronal antibodies, the updated criteria represent a step forward to differentiate true PNS from neurologic syndromes that coincide in time with cancer diagnosis without having a pathogenic link.

Paraneoplastic antibodies targeting intracellular antigens

Although they are relatively rare, the diagnosis of paraneoplastic neurologic syndromes (PNS) can be aided by the identification of neural autoantibodies in patients' serum and cerebrospinal fluid (CSF). They often clinically manifest as characteristic syndromes, including limbic encephalitis, opsoclonus-myoclonus syndrome, paraneoplastic cerebellar degeneration, and paraneoplastic encephalomyelitis. The antibodies are directed either toward intracellular targets, or epitopes on the cell surface. As compared to cell surface antibodies, intracellular paraneoplastic autoantibodies are more classically associated with cancer, most often lung, breast, thymoma, gynecologic, testicular, and/or neuroendocrine cancers. The malignancies themselves tend to be small and regionally contained, attesting to the strength of the immune system in cancer immunosurveillance. Typically, the intracellular antibodies are not directly pathogenic and tend to be associated with PNS that are poorly responsive to treatment. With some notable exceptions, including patients with PNS associated with testicular cancer, patients with intracellular antibodies are typically older individuals, in their 7th decade of life and beyond. Many of them are current or former smokers. Treatment strategies include tumor removal as well as immunotherapy to treat the concomitant PNS. Newer technologies and the ever-broadening use of cancer immunotherapies are contributing to the continued identification of novel intracellularly targeted autoantibodies.

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.

Pathogenesis and immunopathology of paraneoplastic disorders

Paraneoplastic neurologic syndromes (PNS) represent a rare group of immune-mediated complications associated with an underlying tumor. Ectopic protein expression in neoplastic cells or an aberrant immune regulation in the course of hematooncologic diseases or thymomas trigger an autoimmune response that may affect any part of the central and/or peripheral nervous system. Recent advances in drug therapies as well as novel animal models and neuropathologic studies have led to further insights on the immune pathomechanisms of PNS. Although the syndromes share common paths in pathogenesis, they may differ in the disease course, prognosis, and therapy targets, depending on the localization and type of antibody epitope. Neuropathologic hallmarks of PNS associated with antibodies directed against intracellular epitopes are characterized by T cell-dominated inflammation, reactive gliosis including microglial nodules, and neuronal degeneration. By contrast, the neuropathology of cell surface antibody-mediated PNS strongly depends on the targeted antigen and varies from B cell/plasma cell-dominated inflammation and well-preserved neurons together with a reduced expression of the target antigen in anti-NMDAR encephalitis to irreversible Purkinje cell loss in anti-P/Q-type VGCC antibody-associated paraneoplastic cerebellar degeneration. The understanding of different pathomechanisms in PNS is important because they strongly correspond with therapy response and prognosis, and should guide treatment decisions.

An overview on CV2/CRMP5 antibody-associated paraneoplastic neurological syndromes

Paraneoplastic neurological syndrome refers to certain malignant tumors that have affected the distant nervous system and caused corresponding dysfunction in the absence of tumor metastasis. Patients with this syndrome produce multiple antibodies, each targeting a different antigen and causing different symptoms and signs. The CV2/collapsin response mediator protein 5 (CRMP5) antibody is a major antibody of this type. It damages the nervous system, which often manifests as limbic encephalitis, chorea, ocular manifestation, cerebellar ataxia, myelopathy, and peripheral neuropathy. Detecting CV2/CRMP5 antibody is crucial for the clinical diagnosis of paraneoplastic neurological syndrome, and anti-tumor and immunological therapies can help to alleviate symptoms and improve prognosis. However, because of the low incidence of this disease, few reports and no reviews have been published about it so far. This article intends to review the research on CV2/CRMP5 antibody-associated paraneoplastic neurological syndrome and summarize its clinical features to help clinicians comprehensively understand the disease. Additionally, this review discusses the current challenges that this disease poses, and the application prospects of new detection and diagnostic techniques in the field of paraneoplastic neurological syndrome, including CV2/CRMP5-associated paraneoplastic neurological syndrome, in recent years.

Tenascin-R Autoimmunity: Isolated Tremor Reversed with Immunotherapy

Autoimmune movement disorders are increasingly recognized, but isolated tremor is extremely rare. We describe a 70-year-old male with rapidly progressive, severe postural and intention tremor and weight loss. His cerebrospinal fluid was inflammatory and harbored a neural tissue-restricted antibody. The autoantigen was identified by immunoprecipitation and mass spectrometry and confirmed by antigen-specific assays to be specific for tenascin-R. He was investigated for cancer and diagnosed with follicular lymphoma that expressed tenascin-R suggesting a paraneoplastic origin; cancer treatment and immunotherapy led to complete recovery. With this individualized patient approach and antibody discovery, we expand the spectrum of antibodies accompanying autoimmune hyperkinetic movement disorders. ANN NEUROL 2023;94:502-507.

Autoimmune-mediated encephalitis and mimics: A neuroimaging review

Autoimmune encephalitis is a category of autoantibody-mediated neurological disorders that often presents a diagnostic challenge due to its variable clinical and imaging findings. The purpose of this image-based review is to provide an overview of the major subtypes of autoimmune encephalitis and their associated autoantibodies, discuss their characteristic clinical and imaging features, and highlight several disease processes that may mimic imaging findings of autoimmune encephalitis. A literature search on autoimmune encephalitis was performed and publications from neuroradiology, neurology, and nuclear medicine literature were included. Cases from our institutional database that best exemplify major imaging features were presented.

Paraneoplastic motor disorders

Paraneoplastic neurological disorders (PNDs) are heterogeneous clinicopathologic syndromes that occur throughout the neuraxis resulting from damage to organs or tissues remote from the site of a malignant neoplasm or its metastases. The discordance between severe neurological disability and even an indolent malignancy suggests an underlying neuroimmunologic host immune response that inflicts nervous tissue damage while inhibiting malignant tumor growth. Motor system involvement, like other symptoms and signs, is associated with focal or diffuse involvement of the brain, spinal cord, peripheral nerve, neuromuscular junction or muscle, alone or in combination due to an underlying neuroimmune and neuroinflammatory process targeting neural-specific antigens. Unrecognized and therefore untreated, PNDs are often lethal making early detection and aggressive treatment of paramount importance. While the combination of clinical symptoms and signs, and analysis of detailed body and neuroimaging, clinical neurophysiology and electrodiagnostic studies, and tumor and nervous system tissue biopsies are all vitally important, the certain diagnosis of a PND rests with the discovery of a corresponding neural-specific paraneoplastic autoantibody in the blood and/or spinal cerebrospinal fluid.

Motor symptoms in nonparaneoplastic CNS disorders associated with neural antibodies

Motor symptoms are common, and sometimes predominant, in almost all nonparaneoplastic CNS disorders associated with neural antibodies. These CNS disorders can be classified into five groups: (1) Autoimmune encephalitis with antibodies against synaptic receptors, (2) cerebellar ataxias associated with neuronal antibodies that mostly target intracellular antigens. (3) Stiff-person syndrome and progressive encephalomyelitis with rigidity and myoclonus which have antibodies against glutamic acid decarboxylase and glycine receptor, respectively. Both diseases have in common the presence of predominant muscle stiffness and rigidity. (4) Three diseases associated with glial antibodies. Two present motor symptoms mainly due to the involvement of the spinal cord: neuromyelitis optica spectrum disorders with aquaporin-4 antibodies and myelin oligodendrocyte glycoprotein antibody-associated disease. The third disorder is the meningoencephalitis associated with glial fibrillar acidic protein antibodies which frequently also presents a myelopathy. (5) Two antibody-related diseases which are characterized by prominent sleep dysfunction: anti-IgLON5 disease, a disorder that frequently presents a variety of movement disorders, and Morvan syndrome associated with contactin-associated protein-like 2 antibodies and clinical manifestations of peripheral nerve hyperexcitability. In this chapter, we describe the main clinical features of these five groups with particular emphasis on the presence, frequency, and types of motor symptoms.

Immunity, Ion Channels and Epilepsy

Epilepsy is a common chronic neurological disorder in modern society. One of the major unmet challenges is that current antiseizure medications are basically not disease-modifying. Among the multifaceted etiologies of epilepsy, the role of the immune system has attracted considerable attention in recent years. It is known that both innate and adaptive immunity can be activated in response to insults to the central nervous system, leading to seizures. Moreover, the interaction between ion channels, which have a well-established role in epileptogenesis and epilepsy, and the immune system is complex and is being actively investigated. Some examples, including the interaction between ion channels and mTOR pathways, will be discussed in this paper. Furthermore, there has been substantial progress in our understanding of the pathophysiology of epilepsy associated with autoimmune encephalitis, and numerous neural-specific autoantibodies have been found and documented. Early recognition of immune-mediated epilepsy is important, especially in cases of pharmacoresistant epilepsy and in the presence of signs of autoimmune encephalitis, as early intervention with immunotherapy shows promise.

Autoimmune and Paraneoplastic Chorea: A Review of the Literature

Autoimmune chorea syndromes represent a vast array of paraneoplastic, parainfectious and idiopathic disorders. It is increasingly apparent that familiarity with these disorders is critically important, as they may be treatable or may be part of a syndrome requiring further work-up and monitoring. These disorders are mediated by an aberrant immunologic attack with resultant neuronal dysfunction, manifesting as chorea. These conditions are typically accompanied by other neurologic or systemic manifestations. In this review we outline the clinical features, epidemiologic factors, and delineate the specific antibodies associated with each of these autoimmune mediated disorders. We highlight up to date information regarding this heterogeneous group of disorders, including a discussion of parainfectious Sydenham's chorea; paraneoplastic syndromes associated with CRMP-5 (collapsin response mediated protein-5/CV2) and ANNA-1 (antineuronal nuclear antibody / Hu) antibodies, in addition to neuronal antibody-associated disorders including anti-NMDAR, LGI1 (leucine-rich glioma inactivated-1) and CASPR2 (contactin associated protein-2). We discuss the more recently described entities of IgLON5, which has evidence of both immunologic and degenerative pathophysiology, in addition to PDE-10A antibody-associated chorea. We also outline chorea secondary to systemic diseases including Systemic Lupus Erythematosus (SLE) and Primary Antiphospholipid Syndrome (PAPS). We provide a framework for diagnosis and treatment.

Spontaneous Regression of Small Cell Lung Carcinoma and Associated Hemichorea

The spontaneous regression (SR) of cancer is defined as either partial or complete, and temporary or permanent, disappearance without appropriate treatment for the disease, and this phenomenon is rare in the case of small cell lung carcinoma (SCLC). We herein report an 83-year-old woman who presented with left-sided hemichorea associated with anti-SOX1 (SOX1-Ab) and -CV2/CRMP5 (CV2/CRMP5-Ab) antibodies with SR following a 7-year interval free of disease progression of SCLC. Hemichorea can present with the coexistence of anti-SOX1 and CV2/CRMP5-Ab with SR after a long interval free of SCLC. The immune response associated with these onco-neural antibodies may become independent of the original tumor trigger and remain active for many years.

Nodal Peripheral T-cell Lymphoma with T Follicular Helper Phenotype Presenting as Chorea During Treatment: A Case Report and Literature Review

A 72-year-old man presented with chorea while undergoing treatment for recurrence of nodal peripheral T-cell lymphoma with T follicular helper (TFH) phenotype. An examination by brain N-isopropyl-p-iodoamphetamine (123I-IMP)-single photon emission computed tomography (SPECT) revealed no abnormalities other than a decreased cerebral blood flow (CBF) in the left striatum. After four courses of salvage chemotherapy, his clinical symptoms and asymmetric cerebral perfusion improved, suggesting that the decreased CBF had caused chorea. The significance of brain SPECT has not been fully clarified in patients with chorea-associated malignant lymphoma, warranting further investigations. Brain SPECT is an alternative approach to identify abnormalities in such patients.

Paraneoplastic neurological syndromes: a practical approach to diagnosis and management

Paraneoplastic neurological syndromes (PNS) are the immune-mediated effects of a remote cancer and are characterised by an autoantibody response against antigens expressed by the tumour. Classically, well-characterised 'onconeuronal' antibodies target intracellular antigens and hence cannot access their antigens across intact cell membranes. The pathogenic mediators are likely to be neuronal-specific T cells. There is a variable response to immunotherapies and the clinical syndrome helps to direct the search for a specific set of tumours. By contrast, many newly emerging autoantibodies with oncological associations target cell surface epitopes and can exert direct pathogenic effects on both the central and peripheral nervous systems. Patients with these cell-surface directed autoantibodies often clearly respond to immunotherapies. Overall, the clinical, serological and oncological features in an individual patient helps determine the clinical relevance of the syndrome and hence guide its management. We summarise current knowledge and a practical approach to the investigation, diagnosis, treatment and outcomes of patients with suspected PNS.

A Longitudinal, Observational Analysis of Neuronal Injury Biomarkers in a Case Report of a Patient With Paraneoplastic Anti-CRMP5 Antibody-Associated Transverse Myelitis

Biomarkers are needed to guide therapeutic decision making in autoimmune and paraneoplastic neurologic disorders. Here, we describe a case of paraneoplastic collapsing response-mediator protein-5 (CRMP5)-associated transverse myelitis (TM) where plasma neurofilament light (NfL) chain and glial fibrillary protein (GFAP) levels were observed over a 14-month clinical course, correlating with radiographical and clinical outcome measures in response to treatment. Blood and CSF samples obtained at diagnosis as well as 7 and 14 months into treatment. At the time of initial diagnosis, both plasma NfL (782.62 pg/ml) and GFAP (283.26 pg/ml) were significantly elevated. Initial treatment was with IV steroids and plasma exchange (PLEX) followed by neuroendocrine tumor removal, chemotherapy, and radiation. After initial improvement with chemotherapy, the patient experienced clinical worsening and transient elevation of plasma NfL (103.27 pg/ml and GFAP (211.58 pg/ml) levels. Whole body positron emission tomography PET scan did not demonstrate recurrence of malignancy. Repeat PLEX and rituximab induction resulted in improvements in patient function, neurologic exam, and plasma biomarker levels. To our knowledge, this is the first described longitudinal, prospective analysis of neuronal injury biomarkers and association of clinical treatment outcomes in CRMP5 myelitis. Our findings suggest that clinical improvement correlates with NfL and GFAP concentrations.

Neoplastic Meningitis and Paraneoplastic Syndromes

Neoplastic meningitis (NM) and paraneoplastic syndromes (PNSs) are a rare group of disorders present in patients with cancer. Clinical diagnosis of these conditions is challenging, and imaging and laboratory analysis play a significant role in diagnosing. Diagnosis of NM largely depends on documenting circulating tumor cells in the cerebrospinal fluid (CSF) and/or leptomeningeal and nodular enhancement on contrast-enhanced MR imaging of the brain or axial spine. PNSs encompass a variety of symptoms or syndromes. Paraneoplastic neuronal disorder diagnosis requires a multidimensional approach, high clinical suspicion, CSF and serum examination, and imaging. Neuroimaging is an integral part in the evaluation.

Paraneoplastic disorders of the nervous system

This article on paraneoplastic neurologic disorders provides an update on the diagnostic approach, utility and pitfalls of autoantibody testing and emerging settings in which these disorders are encountered. Recognition of the clinical and neuroimaging features accompanying paraneoplastic neurologic disorders is crucial to select those at highest risk who need neural antibody testing and screening for cancer. Cursory knowledge of the antibody assay methodology being ordered is important as the false positive rate varies by the technique utilized for detection. Antibodies can generally be stratified by the location of the target antigen (intraceullar versus cell-surface/synaptic) which informs frequency of cancer association, treatment response and prognosis. The therapeutic approach generally involves detection of the underlying cancer and combinations of oncologic treatments and immunosuppressant medications. The occurrence of paraneoplastic autoimmune neurologic disorders in novel settings, such as with immune checkpoint inhibitor use, has improved understanding of their pathogenesis and increased the likelihood neurologists will encounter such patients in their practice.

Autoimmune encephalopathies presenting as dementia of subacute onset and rapid progression

The terms autoimmune dementia and autoimmune encephalopathy may be used interchangeably; autoimmune dementia is used here to emphasize its consideration in young-onset dementia, dementia with a subacute onset, and rapidly progressive dementia. Given their potential for reversibility, it is important to distinguish the rare autoimmune dementias from the much more common neurodegenerative dementias. The presence of certain clinical features [e.g. facio-brachial dystonic seizures that accompany anti-leucine-rich-glioma-inactivated-1 (LGI1) encephalitis that can mimic myoclonus] can be a major clue to the diagnosis. When possible, objective assessment of cognition with bedside testing or neuropsychological testing is useful to determine the degree of abnormality and serve as a baseline from which immunotherapy response can be judged. Magnetic resonance imaging (MRI) head and cerebrospinal fluid (CSF) analysis are useful to assess for inflammation that can support an autoimmune etiology. Assessing for neural autoantibody diagnostic biomarkers in serum and CSF in those with suggestive features can help confirm the diagnosis and guide cancer search in paraneoplastic autoimmune dementia. However, broad screening for neural antibodies in elderly patients with an insidious dementia is not recommended. Moreover, there are pitfalls to antibody testing that should be recognized and the high frequency of some antibodies in the general population limit their diagnostic utility [e.g., anti-thyroid peroxidase (TPO) antibodies]. Once the diagnosis is confirmed, both acute and maintenance immunotherapy can be utilized and treatment choice varies depending on the accompanying neural antibody present and the presence or absence of cancer. The target of the neural antibody biomarker may help predict treatment response and prognosis, with antibodies to cell-surface or synaptic antigens more responsive to immunotherapy and yielding a better overall prognosis than those with antibodies to intracellular targets. Neurologists should be aware that autoimmune dementias and encephalopathies are increasingly recognized in novel settings, including post herpes virus encephalitis and following immune-checkpoint inhibitor use.

Generalized and orofacial choreoathetosis: a case report of anti-CV2 paraneoplastic syndrome after cardiac arrest

CV2/CRMP5 is the most common antibody accompaniment of paraneoplastic choreoathetosis. We present a case of paraneoplastic choreothetosis with associated cerebellar dysfunction, peripheral neuropathy, and likely dysautonomia. Our patient developed a movement disorder after a cardiopulmonary arrest, which unfortunately masked the true etiology of his symptoms. He was later found to have extensive stage small cell lung cancer, with further evaluation revealing seropositivity for anti-CV2 antibodies. Choreoathetosis is a known sequelae of hypoxic-ischemic brain injury, but clinicians should continue to keep an open mind. The utility of immunotherapy is unclear in these circumstances and many physicians adopt a symptom-based approach.

Paraneoplastic neurological syndromes: clinical presentations and management

We provide an overview of the varied presentations of paraneoplastic neurological syndromes. We also review the onconeural antibodies and their particular oncological and neurological associations. Recognition of these syndromes and their oncological associations is crucial, as early diagnosis and management has been associated with better patient outcomes. Specific management strategies and prognosis vary widely depending on the underlying etiology. An understanding of the relevant clinical details, imaging findings, and other diagnostic information can help tailor treatment approaches. We provide an outline of the diagnostic evaluation and treatment of various paraneoplastic neurological disorders, presenting with central and/or peripheral nervous system involvement. We briefly discuss neurologic immune checkpoint inhibitor-related adverse events, which can occasionally present with paraneoplastic neurological syndrome phenotypes.

[A case of anti-SRY-Related HMG-Box Gene 1 (SOX1) antibody-positive chorea]

A 77-year-old man with a history of lung cancer at the age of 71 developed involuntary right leg movement for a month. Neurological examination revealed a right-sided hemi-chorea. Autoimmune disease was suspected owing to the presence of oligoclonal bands and the elevated IgG-index in the cerebrospinal fluid. We detected anti-SRY-Related HMG-Box Gene 1 (SOX1) antibodies, known to be serological markers of Lambert-Eaton syndrome with small cell lung cancer, but not tumors. The results of tests for antiphospholipid, anti-LGI1, and anti-CASPR2 antibodies associated with non-paraneoplastic autoimmune chorea were all negative. This is the first suggestive case of autoimmune chorea in which anti-SOX1 antibodies were detected.

Case Report: Innate Immune System Challenge Unleashes Paraneoplastic Neurological Autoimmunity

Paraneoplastic autoimmune neurological disorders reflect tumor-initiated immune responses against onconeural antigens. Symptoms and signs can affect the central and/or peripheral nervous systems, neuromuscular junction or muscle, and typically evolve subacutely before an underlying neoplasm is discovered. We describe four patients whose neurological symptoms were precipitated by potent innate immune system challenges: bladder instillation of BCG, tick bite and an "alternative cancer therapy" with bacterial extracts and TNF-α. We hypothesize that a tumor-initiated autoimmune response (evidenced by autoantibody profiles), pre-dating the immune system challenge, was unmasked or amplified in these patients by cytokines released systemically from innate immune cells activated by microbial pathogen-associated molecular patterns (PAMPs). The resultant upregulation of cognate onconeural peptides as MHC1 protein complexes on neural cell surfaces would render those cells susceptible to killing by CD8+ T cells, thus precipitating the patient's neurological symptoms.

Neurologic Complications of Immune Checkpoint Inhibitors in Thoracic Malignancies

Immune checkpoint inhibitors (ICIs) have transformed the prognosis of cancers previously considered lethal. The spectrum of therapeutic indications is rapidly expanding, including the vast majority of thoracic malignancies. By enhancing the immune responses against cancer, the ICI treatments lead to the development of immune-related adverse events (irAEs) that may affect any organ. Severity varies from mild to fatal clinical manifestations. Neurologic involvement is relatively rare and highly heterogeneous, including central and peripheral nervous system diseases associated with neural-specific autoantibodies or not, central nervous system vasculitis, and granulomatous and demyelinating disorders. Symptoms often manifest within the first four cycles of treatment and can develop regardless of the class of ICI used. An unfavorable outcome is found in up to one-third of patients and is generally associated with the patients' clinical characteristics (e.g., age, coexistence of systemic adverse events), cancer type (e.g., lung cancer versus other), and specific clinical setting (e.g., ICI treatment in patients with preexisting paraneoplastic neurologic autoimmunity, ICI rechallenge after a first neurologic irAE). Diagnosis should be suspected in patients with new-onset neurologic symptoms while on ICI treatment which are not explained by metastatic disease or other metabolic/infectious disorders. Recommended treatment is based on clinical severity and consists of ICI discontinuation with or without immunosuppressive/immunomodulatory therapy, although alternative approaches are reasonable depending on cancer status (e.g., aggressive immunosuppression without discontinuing ICI in patients with initial cancer response). Early recognition and appropriate treatment of these neurologic irAEs are crucial for improved patient outcomes and therapeutic planning.

Autoimmune encephalitis with psychiatric features in adults: historical evolution and prospective challenge

Our review aims to delineate the psychiatric spectrum of autoantibody-associated autoimmune encephalitis over time through its discoveries of antibodies. We searched in PubMed for appropriate articles depicting the first appearance and spectrum of psychiatric symptomatology in autoantibody-positive encephalitis for this narrative review. Memory impairment was first associated with autoantibodies against intracellular antigens such as anti-HuD antibodies in 1993. 8 years later, autoantibodies against cell membrane surface antigens such as voltage-gated potassium channels were described in conjunction with memory dysfunction. The spectrum of psychiatric syndromes was amplified between 1990 and 2020 to include disorientation, behavior, cognitive dysfunction, obsessive compulsive behavior and suicidality in encephalitis patients occurring together mainly with antibodies against surface antigens, less so against intracellular antigens. In general, we found no specific psychiatric symptoms underlying specific autoantibody-associated encephalitis. As fundamental data on this issue have not been systemically assessed to date, we cannot know whether our specific findings would remain from systematic studies, i.e., on the association between cerebrospinal fluid N-methyl-D-aspartate receptor antibodies in catatonia. The psychiatric symptomatology overlaps between psychiatric domains and occurs frequently in antibody-positive encephalitis. No specific psychiatric symptoms imply an underlying, specifically autoantibody-associated encephalitis. The psychiatric phenotypology associated with antibody-positive encephalitis has evolved tremendously recently, and this new evidence reveals its relevance for future diagnostic and treatment aspects of autoimmune encephalitis patients.

Antibody-related movement disorders - a comprehensive review of phenotype-autoantibody correlations and a guide to testing

Background

Over the past decade increasing scientific progress in the field of autoantibody-mediated neurological diseases was achieved. Movement disorders are a frequent and often prominent feature in such diseases which are potentially treatable.

Main body

Antibody-mediated movement disorders encompass a large clinical spectrum of diverse neurologic disorders occurring either in isolation or accompanying more complex autoimmune encephalopathic diseases. Since autoimmune movement disorders can easily be misdiagnosed as neurodegenerative or metabolic conditions, appropriate immunotherapy can be delayed or even missed. Recognition of typical clinical patterns is important to reach the correct diagnosis.

Conclusion

There is a growing number of newly discovered antibodies which can cause movement disorders. Several antibodies can cause distinctive phenotypes of movement disorders which are important to be aware of. Early diagnosis is important because immunotherapy can result in major improvement.In this review article we summarize the current knowledge of autoimmune movement disorders from a point of view focused on clinical syndromes. We discuss associated clinical phenomenology and antineuronal antibodies together with alternative etiologies with the aim of providing a diagnostic framework for clinicians considering underlying autoimmunity in patients with movement disorders.

Autoimmune encephalitis management: MS centers and beyond

Traditionally, multiple sclerosis (MS) specialists have been the go-to providers for managing certain treatable non-demyelinating inflammatory or autoimmune central nervous system (CNS) disorders. The advent of increased incidence (mostly due to improved recognition) prompts the question: who should be managing autoimmune encephalitis? These patients are generally first encountered in the hospital, as well as general neurology and subspecialty clinics, such as epilepsy. Autoimmune neurology is a specialty which gives focus to evaluation and treatment of patients with autoimmune encephalitis, among other disorders, and trains neurologists accordingly. Some of those experts are dual trained in both MS and non-MS inflammatory/autoimmune CNS disorders. Many other autoimmune specialists are trained in non-MS care, such as hospital neurology, movement disorders, and epilepsy. General and other subspecialty providers increasingly find the need to be versed in management of autoimmune encephalitis.

Anti-CV2 Autoimmune Encephalitis With Parkinson-Like Symptoms and Bilateral Leukoencephalopathy-A Case Report

Objective: To present a patient with anti-CV2 autoimmune encephalitis admitted for Parkinson-like symptoms and bilateral leukoencephalopathy.

Case report: The patient was admitted for Parkinson-like symptoms combined with loss of taste. Serum anti-CV2 antibody was positive. Cranial magnetic resonance imaging revealed bilateral leukoencephalopathy. Breast cancer was detected by positron emission tomography (PET) and ultrasound. Immunotherapy was not performed. Modified radical mastectomy revealed a pT1cN0M0 breast cancer, positive for estrogen and progesterone receptors, and HER2 negative. The resting tremors disappeared by 1 week after surgery. The modified Rankin score (mRS) was four before surgery, and decreased to one at 9 months after surgery.

Conclusion: Anti-CV2 autoimmune encephalitis can present as Parkinsonism with bilateral leukoencephalopathy on MRI. PET scanning can be useful to reveal an occult cancer. Treatment of the cancer may improve the paraneoplastic neurological syndrome without the need of immunosuppressive therapy.

Collapsin Response-Mediator Protein 5-Associated Retinitis, Vitritis, and Optic Disc Edema

PURPOSE

Collapsin response-mediator protein 5 (CRMP5) immunoglobulin G (IgG) has been associated with paraneoplastic optic neuritis, vitritis, retinitis, or a combination thereof, but few reports of these findings exist in the literature. We reviewed the neuro-ophthalmic findings and visual outcomes in a large series of CRMP5 IgG-positive patients to characterize further its clinical phenotype and response to treatment.

DESIGN

Retrospective case series.

PARTICIPANTS

Seventy-six patients with CRMP5 autoimmunity examined at the Mayo Clinic, Rochester, Minnesota.

METHODS

Single academic medical center chart review of all CRMP5 IgG-positive (serum titer, >1:240) patients seen between 2001 and 2017.

MAIN OUTCOME MEASURES

Neuro-ophthalmic manifestations and outcomes of CRMP5 autoimmunity, coexisting neural autoantibody presence and paraneoplastic associations, and the impact of immunosuppressant therapy.

RESULTS

Twenty-nine of 76 patients (38%) demonstrated neuro-ophthalmic manifestations. Of the 29 patients with neuro-ophthalmic findings, the median age was 67 years (range, 33-88 years) and 20 (69%) were women. Cancer was diagnosed in 62% of the patients (small-cell carcinoma in 83%). Neuro-ophthalmic symptoms occurred before the diagnosis of cancer in 72%. Seventeen of 29 patients (59%) showed ocular (i.e., anterior visual pathway or intraocular) manifestations; presenting median visual acuity was 20/50 (range, 20/20-counting fingers) and the final median visual acuity was 20/40 (range, 20/20-hand movements). Fourteen of 17 patients (82%) demonstrated optic neuropathy, with 12 of these patients also showing retinitis or uveitis. Three of 17 patients (18%) showed retinitis or uveitis without optic neuropathy. All 12 patients with optic neuropathy and a documented fundus examination at visual symptom onset demonstrated optic disc edema. No patients showed optic nerve enhancement on magnetic resonance imaging. Twelve of 29 patients (41%) demonstrated ocular motility dysfunction consisting of central nystagmus and diplopia. Among those receiving immunosuppressive therapy, visual function improved in 50%.

CONCLUSIONS

In our cohort of 29 CRMP5 IgG-positive patients with neuro-ophthalmic manifestations, optic neuropathy presented with optic disc edema, often associated with uveitis, retinitis, or both. The combination of retinitis, vitritis, and optic disc edema without optic nerve enhancement should prompt serologic testing for CRMP5 IgG to expedite vision-sparing immunosuppressant therapy and a targeted search for a systemic cancer.

Paraneoplastic movement disorders: phenomenology, diagnosis, and treatment

Paraneoplastic syndromes include, by definition, any symptomatic and non-metastatic condition associated with a neoplasm. Paraneoplastic movement disorders are a heterogeneous group of syndromes encompassing both hyperkinetic and hypokinetic conditions, characterized by acute/sub-acute onset, rapidly progressive evolution, and multifocal localizations with several overlapping features. These movement disorders are immune-mediated, as shown by the rapid onset and by the presence of antineuronal antibodies in biological samples of patients, fundamental for the diagnosis. Antineuronal antibodies could be targeted against intracellular or neuronal surface antigens. Paraneoplastic movement disorders associated with anti-neuronal surface antigens antibodies respond more frequently to immunotherapy. The underlying tumors may be different, according to the clinical presentation, age, and gender of patients. Our search considered articles involving human subjects indexed in PubMed. Abstracts were independently reviewed for eligibility criteria by one author and validated by at least one additional author. In this review, we sought to critically reappraise the clinical features and the pathophysiological mechanisms of paraneoplastic movement disorders, focusing on diagnostic and therapeutic strategies. Our main aim is to make clinicians aware of paraneoplastic movement disorders, and to provide assistance in the early diagnosis and management of these rare but life-threatening conditions.

Phosphodiesterase 10A IgG: A novel biomarker of paraneoplastic neurologic autoimmunity

OBJECTIVE

To describe a novel antibody biomarker of neurologic paraneoplastic autoimmunity specific for phosphodiesterase 10A (PDE10A), a striatum-enriched phosphodiesterase, and to characterize the clinical phenotype of patients with PDE10A immunoglobulin G (IgG).

METHODS

We describe 7 patients with autoantibodies specific for PDE10A identified in the Mayo Clinic Neuroimmunology Laboratory. Patient specimens (sera, 7; CSF, 4) produced identical basal ganglia-predominant synaptic staining of murine brain tissue by indirect immunofluorescence. The autoantigen was identified by immunoprecipitation and mass spectrometry as PDE10A, and confirmed by antigen-specific recombinant Western blot and cell-based assays, and immune absorption experiments.

RESULTS

The median patient age was 70 years (range 66-76); 4 were men. Four patients with clinical information available had movement disorders (hyperkinetic in 3 [chorea, ballismus, dystonia] and parkinsonism in 1). All patients but one had cancer (lung [adenocarcinoma 1, squamous cell carcinoma 1, poorly differentiated mesenchymal carcinoma 1], renal adenocarcinoma 2, and pancreatic adenocarcinoma 1). Two of the 7 patients developed hyperkinetic movement disorders during treatment with immune checkpoint inhibitors (nivolumab and pembrolizumab), though none of 26 cancer control patients treated with immune checkpoint inhibitors harbored PDE10A IgG in their serum. MRIs from those 2 patients with hyperkinetic movement disorders demonstrated fluid-attenuated inversion recovery/T2 basal ganglia hyperintensities, and their CSF harbored unique oligoclonal bands. One of those 2 patients had substantial improvement after corticosteroids. One patient's renal adenocarcinoma expressed PDE10A by immunohistochemistry.

CONCLUSIONS

PDE10A IgG defines a novel rare neurologic autoimmune syndrome and expands the spectrum of diagnosable paraneoplastic CNS disorders. The intracellular location of PDE10A suggests a T-cell-mediated pathology targeting cells displaying MHC1-bound PDE10A peptides.

Autoimmune Epilepsy

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

The role of the laboratory in the expanding field of neuroimmunology: Autoantibodies to neural targets

Accelerated identification of autoantibodies associated with previously idiopathic neurological disease has provided insights into disease mechanisms, enhanced understanding of neurological function, and opportunities for improved therapeutic interventions. The role of the laboratory in the expanding field of neuroimmunology is critical as specific autoantibody identification provides guidance to clinicians in diagnosis, prognosis, tumor search strategies, and therapeutic interventions. The number of specific autoantibodies identified continues to increase and newer testing strategies increase efficiencies in the laboratory and availability to clinicians. The need for broadly targeted efficient testing is underscored by the variability in clinical presentation and tumor associations attributable to a specific autoantibody, and conversely the various autoantibody specificities that can be the cause of a given clinical presentation. While many of the antineural antibodies were first recognized in the setting of neoplastic disease, idiopathic autoimmune neurological disease in the absence of underlying tumor is increasingly recognized. Appropriation of therapeutic modalities used to treat autoimmune disease to treat these autoantibody mediated neurological diseases has improved patient outcomes. Interaction between clinicians and laboratorians is critical to our understanding of these diseases and optimization of the clinical benefits of our increasing knowledge in neuroimmunology.

Autoimmune epilepsy: findings on MRI and FDG-PET

Autoimmune epilepsy (AE) is becoming increasingly recognized as a potentially reversible cause of frequent or medically intractable seizures and cognitive deterioration. We describe various presentations of autoimmune encephalopathy which have specifically presented with seizure and describe reported imaging findings. This is organized as a review of the more common autoantibodies which can specifically precipitate seizure according to the intracellular or extracellular location of the targeted antigen. For each antibody, we illustrate their pathophysiology, characteristic clinical presentations with typical effective treatments and prognoses and imaging findings on MRI and PET/CT exams. Parenchymal involvement is variable with the limbic structures typically affected; however, non-limbic cortex, cerebellum, brainstem and basal ganglia can also be involved. In the acute setting, affected regions typically demonstrate T₂ hyperintensity with mild mass effect from edema and increased ¹⁸F-fludeoxyglucose uptake. Chronically involved parenchyma will often undergo atrophy and demonstrate decreased metabolism; mesial temporal sclerosis is often the end result when the limbic system is involved. Without treatment, long-term effects from AE range from ongoing cognitive dysfunction and refractory seizures to death. Familiarity with AE may prompt appropriate antibody screening, particularly in cases of refractory seizure disorders. Early investigation and proper management of AE cases may help to prevent parenchymal and neurologic deterioration in these patients.

[A case of hemichorea associated with lung adenocarcinoma]

An 81-year-old woman admitted to our hospital due to involuntary movement on her right extremities. Laboratory tests, including autoantibodies, were unremarkable and only age related changes were observed on brain MRI. Chest CT revealed lung adenocarcinoma. She was diagnosed as having paraneoplastic chorea. After removal of the tumor, her chorea was dramatically improved. One year after the operation, abnormal high intensity lesions were seen in bilateral caudate nuclei and globus pallidus on MRI. A part of the left caudate nucleus was enhanced by gadolinium. Here we show a clinical picture and neuroradiological findings of paraneoplastic chorea associated with lung adenocarcinoma.

Autoimmune CRMP5 neuropathy phenotype and outcome defined from 105 cases

Objective

To establish the phenotype and clinical outcomes of collapsin response-mediator protein-5 (CRMP5) autoimmune neuropathy in comparison with anti-neuronal nuclear antibody type 1 (ANNA1)–immunoglobulin G (IgG) neuropathy.

Methods

Patients with CRMP5-IgG and/or ANNA1-IgGs were identified in our service-line testing, and medical records were reviewed.

Results

One hundred five patients with CRMP5-IgG neuropathy (88% smokers; 69% having cancer, most commonly small cell lung cancer [75%]) were identified and compared to 51 patients with ANNA1-IgG neuropathy, 27 with coexisting CRMP5-IgG. Patients with CRMP5 had painful axonal polyradiculoneuropathy (65%), mostly asymmetric onset (84%), with neuropathy predating cancer diagnosis by 185 days (range 60–540 days). Most cases (79%) had moderate to severe neuropathic pain, all on neuropathic medications (median 2, range 1–4), opioids in 39%. Nerve biopsies (n = 2) showed microvascular inflammation with axonal degeneration. Compared to ANNA1 alone, CRMP5 neuropathy has a higher prevalence of pain (79% vs 46%, p = 0.008), asymmetric polyradiculoneuropathy (54% vs 12%, p < 0.001), and inflammatory spinal fluids (elevated CSF protein or nucleated cell count 92% vs 60%, p = 0.022). Cerebellar ataxia (21%), myelopathy (19%), and optic neuritis and/or retinitis (11%) were common neurologic accompaniments. CRMP5 cases had significant pain reduction by immunotherapy (p < 0.001). Specifically, high-dose corticosteroid administration was associated with improvement/stabilization in neuropathy impairment scores (p = 0.012) (Class IV). Patients with CRMP5 had better 5-year survival than patients with ANNA1 (67% vs 32%, p = 0.012).

Conclusion

Painful axonal asymmetric polyradiculoneuropathy is established as the major CRMP5 autoimmune neuropathy presentation and is distinguishable from other paraneoplastic neuropathies, including by ANNA1 autoimmunity. Patients with this phenotype should be prompted for CRMP5-IgG testing to assist in early cancer diagnosis.