Phenotypic presentations of paraneoplastic neuropathies associated with MAP1B-IgG

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.

Paraneoplastic neuropathies and peripheral nerve hyperexcitability disorders

Peripheral neuropathy is a common referral for patients to the neurologic clinics. Paraneoplastic neuropathies account for a small but high morbidity and mortality subgroup. Symptoms include weakness, sensory loss, sweating irregularity, blood pressure instability, severe constipation, and neuropathic pain. Neuropathy is the first presenting symptom of malignancy among many patients. The molecular and cellular oncogenic immune targets reside within cell bodies, axons, cytoplasms, or surface membranes of neural tissues. A more favorable immune treatment outcome occurs in those where the targets reside on the cell surface. Patients with antibodies binding cell surface antigens commonly have neural hyperexcitability with pain, cramps, fasciculations, and hyperhidrotic attacks (CASPR2, LGI1, and others). The antigenic targets are also commonly expressed in the central nervous system, with presenting symptoms being myelopathy, encephalopathy, and seizures with neuropathy, often masked. Pain and autonomic components typically relate to small nerve fiber involvement (nociceptive, adrenergic, enteric, and sudomotor), sometimes without nerve fiber loss but rather hyperexcitability. The specific antibodies discovered help direct cancer investigations. Among the primary axonal paraneoplastic neuropathies, pathognomonic clinical features do not exist, and testing for multiple antibodies simultaneously provides the best sensitivity in testing (AGNA1-SOX1; amphiphysin; ANNA-1-HU; ANNA-3-DACH1; CASPR2; CRMP5; LGI1; PCA2-MAP1B, and others). Performing confirmatory antibody testing using adjunct methods improves specificity. Antibody-mediated demyelinating paraneoplastic neuropathies are limited to MAG-IgM (IgM-MGUS, Waldenström's, and myeloma), with the others associated with cytokine elevations (VEGF, IL6) caused by osteosclerotic myeloma, plasmacytoma (POEMS), and rarely angiofollicular lymphoma (Castleman's). Paraneoplastic disorders have clinical overlap with other idiopathic antibody disorders, including IgG4 demyelinating nodopathies (NF155 and Contactin-1). This review summarizes the paraneoplastic neuropathies, including those with peripheral nerve hyperexcitability.

Management of Paraneoplastic Syndromes in the Era of Immune Checkpoint Inhibitors

OPINION STATEMENT

Our understanding of paraneoplastic neurologic syndromes (PNS) has blossomed over the past few decades. Clinicians have access to more robust diagnostic criteria and have a heightened index of suspicion for these disorders. Nonetheless, treatment, which typically includes immunosuppression, and response to treatment, varies. Due to persistent difficulty in making a definitive diagnosis, we favor empiric treatment when a possible diagnosis of PNS is suspected, and other alternative causes have substantially been excluded (e.g., infections, toxic-metabolic derangements, metastasis, or leptomeningeal disease). Treatment of the underlying cancer, if identified, is the first therapeutic step and can prevent disease worsening and in rare cases, can reverse neurologic symptoms. In addition to anti-cancer treatment, first line immunotherapies, which include corticosteroids, intravenous immunoglobulins (IVIG), or plasma exchange (PLEX) are typically used. If partial or no benefit is seen, second line immunotherapeutic agents such as rituximab are considered. Additionally, the severity of the initial presentation and possible risk for relapse influences the use of the latter agents. Symptomatic management is also an important component in our practice and will depend on the syndrome being treated. One of the more novel entities we are facing currently is the management of immune checkpoint (ICI)-induced PNS. In those cases, current American Society of Clinical Oncology (ASCO) guidelines are followed.

Autoimmune Axonal Neuropathies

OBJECTIVE

This article reviews autoimmune axonal neuropathies, their characteristic clinical features, disease and antibody associations, appropriate ancillary testing, treatment, and prognosis.

LATEST DEVELOPMENTS

In 2021, the American College of Rheumatology and the Vasculitis Foundation released new summary guidelines for the treatment of antineutrophil cytoplasmic autoantibody-associated vasculitides. In addition, novel autoantibodies have been recently identified; they are often paraneoplastic and associated with axonal neuropathies.

ESSENTIAL POINTS

Recognition of autoimmune axonal neuropathies is important because of the potential for effective treatment to either reverse deficits or slow the progression of disease. It is necessary to properly assess for associations with other systemic disorders (eg, systemic vasculitis, connective tissue disease, neoplasm) so that adequate treatment for both neurologic and non-neurologic aspects of the disease can be initiated.

Paraneoplastic Neurologic Disorders

PURPOSE OF REVIEW

To provide an overview and highlight recent updates in the field of paraneoplastic neurologic disorders.

RECENT FINDINGS

The prevalence of paraneoplastic neurologic disorders is greater than previously reported and the incidence has been rising over time, due to improved recognition in the era of antibody biomarkers. Updated diagnostic criteria that are broadly inclusive and also contain diagnostic risk for clinical presentations (high and intermediate) and diagnostic antibodies (high, intermediate, and low) have replaced the original 2004 criteria. Antibody biomarkers continue to be characterized (e.g., KLHL-11 associated with seminoma in men with brainstem encephalitis). Some paraneoplastic antibodies also provide insight into likely immunotherapy response and prognosis. The rise of immune checkpoint inhibitors as cancer therapeutics has been associated with newly observed immune-mediated adverse effects including paraneoplastic neurological disorders. The therapeutic approach to paraneoplastic neurologic disorders is centered around cancer care and trials of immune therapy. The field of paraneoplastic neurologic disorders continues to be advanced by the identification of novel antibody biomarkers which have diagnostic utility, and give insight into likely treatment responses and outcomes.

Origins and immunopathogenesis of autoimmune central nervous system disorders

The field of autoimmune neurology is rapidly evolving, and recent discoveries have advanced our understanding of disease aetiologies. In this article, we review the key pathogenic mechanisms underlying the development of CNS autoimmunity. First, we review non-modifiable risk factors, such as age, sex and ethnicity, as well as genetic factors such as monogenic variants, common variants in vulnerability genes and emerging HLA associations. Second, we highlight how interactions between environmental factors and epigenetics can modify disease onset and severity. Third, we review possible disease mechanisms underlying triggers that are associated with the loss of immune tolerance with consequent recognition of self-antigens; these triggers include infections, tumours and immune-checkpoint inhibitor therapies. Fourth, we outline how advances in our understanding of the anatomy of lymphatic drainage and neuroimmune interfaces are challenging long-held notions of CNS immune privilege, with direct relevance to CNS autoimmunity, and how disruption of B cell and T cell tolerance and the passage of immune cells between the peripheral and intrathecal compartments have key roles in initiating disease activity. Last, we consider novel therapeutic approaches based on our knowledge of the immunopathogenesis of autoimmune CNS disorders.

Rare case of anti-CV2 paraneoplastic polyneuropathy associated with lung adenocarcinoma

We describe the first case of anti-CV2 paraneoplastic polyneuropathy associated with lung adenocarcinoma. Our patient presented with progressive unsteadiness and numbness involving bilateral upper and lower limbs. He had symmetrical length-dependent lower motor neuron pattern of weakness and numbness involving both small and large fibres with prominent sensory ataxia. An extended workup for the polyneuropathy involving a serum paraneoplastic antineuronal antibody panel showed a positive reaction for anti-CV2 antibody. CT scan of the thorax, abdomen and pelvis revealed a right upper lung nodule and histopathological examination of the nodule revealed lung adenocarcinoma. He was scheduled for chemotherapy following his discharge and there was improvement of his sensorimotor polyneuropathy following his chemotherapy.

Axonal transport deficits in the pathogenesis of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is a chronic and prevalent metabolic disease that gravely endangers human health and seriously affects the quality of life of hyperglycemic patients. More seriously, it can lead to amputation and neuropathic pain, imposing a severe financial burden on patients and the healthcare system. Even with strict glycemic control or pancreas transplantation, peripheral nerve damage is difficult to reverse. Most current treatment options for DPN can only treat the symptoms but not the underlying mechanism. Patients with long-term diabetes mellitus (DM) develop axonal transport dysfunction, which could be an important factor in causing or exacerbating DPN. This review explores the underlying mechanisms that may be related to axonal transport impairment and cytoskeletal changes caused by DM, and the relevance of the latter with the occurrence and progression of DPN, including nerve fiber loss, diminished nerve conduction velocity, and impaired nerve regeneration, and also predicts possible therapeutic strategies. Understanding the mechanisms of diabetic neuronal injury is essential to prevent the deterioration of DPN and to develop new therapeutic strategies. Timely and effective improvement of axonal transport impairment is particularly critical for the treatment of peripheral neuropathies.

A paraneoplastic syndrome misdiagnosed as ALS: What are the red flags? A case report and review of the literature

Background Paraneoplastic motor neuron disease (PMND) is a rare, non-classical form of paraneoplastic neurological syndrome (PNS). Anti-Hu and anti-CV2/CRMP5 PNS are mostly associated with small-cell lung cancer (SCLC) and consist of highly variable clinical syndromes, including sensory neuronopathy, cerebellar ataxia and/or limbic encephalitis. However, substantial motor impairment is uncommon, particularly when no sensory dysfunction co-exists. Case A 72-year-old man with a recent diagnosis of amyotrophic lateral sclerosis (ALS) was referred to our department of neurology for evaluation. The patient sub-acutely developed progressive neurological dysfunction including erectile dysfunction, behavioral changes, limb weakness, dysphagia, anorexia, as well as worsening stridor that necessitated tracheostomy due to bilateral vocal cord paralysis (BVCP). Neurological examination revealed motor weakness of upper and lower motor neuron origin with autonomic and cognitive dysfunction. Cerebrospinal fluid (CSF) analysis demonstrated pleocytosis, elevated protein, presence of oligoclonal bands (OCB), and neuronal antibody testing was positive for anti-Hu and anti-CV2/CRMP5. Based on these findings a diagnosis of a PNS was made. Evaluation for malignancy was negative, and immunosuppressive/immunomodulatory treatment was initiated but had little effect during fifteen months of follow-up. Conclusions Although PMND is very rare, in an atypical presentation, especially with features that are not usually present in ALS such as autonomic dysfunction, sensory disturbance or cognitive decline, this etiology should be in the differential diagnosis.

Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes

Objective

The contemporary diagnosis of paraneoplastic neurologic syndromes (PNSs) requires an increasing understanding of their clinical, immunologic, and oncologic heterogeneity. The 2004 PNS criteria are partially outdated due to advances in PNS research in the last 16 years leading to the identification of new phenotypes and antibodies that have transformed the diagnostic approach to PNS. Here, we propose updated diagnostic criteria for PNS.

Methods

A panel of experts developed by consensus a modified set of diagnostic PNS criteria for clinical decision making and research purposes. The panel reappraised the 2004 criteria alongside new knowledge on PNS obtained from published and unpublished data generated by the different laboratories involved in the project.

Results

The panel proposed to substitute “classical syndromes” with the term “high-risk phenotypes” for cancer and introduce the concept of “intermediate-risk phenotypes.” The term “onconeural antibody” was replaced by “high risk” (>70% associated with cancer) and “intermediate risk” (30%–70% associated with cancer) antibodies. The panel classified 3 levels of evidence for PNS: definite, probable, and possible. Each level can be reached by using the PNS-Care Score, which combines clinical phenotype, antibody type, the presence or absence of cancer, and time of follow-up. With the exception of opsoclonus-myoclonus, the diagnosis of definite PNS requires the presence of high- or intermediate-risk antibodies. Specific recommendations for similar syndromes triggered by immune checkpoint inhibitors are also provided.

Conclusions

The proposed criteria and recommendations should be used to enhance the clinical care of patients with PNS and to encourage standardization of research initiatives addressing PNS.

Leucine Zipper 4 Autoantibody: A Novel Germ Cell Tumor and Paraneoplastic Biomarker

OBJECTIVE

This study was undertaken to describe a novel biomarker of germ cell tumor and associated paraneoplastic neurological syndrome (PNS).

METHODS

Archival sera from patients with germ cell tumor-associated PNS were evaluated. We identified a common autoantigen in a human testicular cancer cell line (TCam-2) by Western blot and mass spectrometry. Its identity was confirmed by recombinant-protein Western blot, enzyme-linked immunosorbent assay (ELISA), and cell-based assay. Autoantibody specificity was confirmed by analyzing assorted control sera/cerebrospinal fluid.

RESULTS

Leucine zipper 4 (LUZP4)-immunoglobulin G (IgG) was detected in 28 patients' sera, 26 of whom (93%) were men. The median age at neurological symptom onset was 45 years (range = 28-84). Median titer (ELISA) was 1:300 (1:50 to >1:6,400, normal value < 1:50). Coexistent kelchlike protein 11-IgG was identified in 18 cases (64%). The most common presenting phenotype was rhombencephalitis (17/28, 61%). Other presentations included limbic encephalitis (n = 5, 18%), seizures and/or encephalitis (n = 2, 7%), and motor neuronopathy/polyradiculopathy (n = 4, 14%). The most common malignancy among cancer-evaluated PNS patients was seminoma (21/27, 78%). Nine of the 21 seminomas detected by whole-body fluorodeoxyglucose positron emission tomography scan (43%) were extratesticular. Both female patients had ovarian teratoma. Regressed testicular germ cell tumors were found in 4 patients. Exposure of T-cell-dendritic-cell cocultures from chronic immunosuppression-naïve LUZP4-IgG-seropositive patients to recombinant LUZP4 protein evoked a marked increase in CD69 expression on both CD4+ and CD8+ T cells when compared to vehicle-exposed and healthy control cultures.

INTERPRETATION

LUZP4-IgG represents a novel serological biomarker of PNS and has high predictive value for germ cell tumors. The demonstrated antigen-specific T-cell responses support a CD8+ T-cell-mediated cytotoxic paraneoplastic and antitumor potential. ANN NEUROL 2021;89:1001-1010.

Paraneoplastic neurological syndrome: an evolving story

Paraneoplastic neurological syndrome (PNS) comprises a group of neurological disorders that result from a misguided immune response to the nervous system triggered by a distant tumor. These disorders frequently manifest before the diagnosis of the underlying neoplasm. Since the first reported case in 1888 by Oppenheim, the knowledge in this area has evolved rapidly. Several classic PNS have been described, such as limbic encephalitis, paraneoplastic cerebellar degeneration, encephalomyelitis, opsoclonus-myoclonus, sensory neuronopathy, Lambert-Eaton Myasthenic syndrome, and chronic gastrointestinal dysmotility. It is now recognized that PNS can have varied nonclassical manifestations that extend beyond the traditional syndromic descriptions. Multiple onconeural antibodies with high specificity for certain tumor types and neurological phenotypes have been discovered over the past 3 decades. Increasing use of immune checkpoint inhibitors (ICIs) has led to increased recognition of neurologic ICI-related adverse events. Some of these resemble PNS. In this article, we review the clinical, oncologic, and immunopathogenic associations of PNS.

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.

Paraneoplastic Myeloneuropathies: Clinical, Oncologic, and Serologic Accompaniments

Objective

To test the hypothesis that myeloneuropathy is a presenting phenotype of paraneoplastic neurologic syndromes we retrospectively reviewed clinical, radiologic, and serologic features of 32 patients with concomitant paraneoplastic spinal cord and peripheral nervous system involvement.

Methods

Observational study investigating patients with myeloneuropathy and underlying cancer or onconeural antibody seropositivity.

Results

Among 32 patients with paraneoplastic myeloneuropathy, 20 (63%) were women with median age 61 years (range 27–84 years). Twenty-six patients (81%) had classified onconeural antibodies (amphiphysin, n = 8; antineuronal nuclear antibody [ANNA] type 1 [anti-Hu], n = 5; collapsin response mediator protein 5 [CRMP5] [anti-CV2], n = 6; Purkinje cell cytoplasmic antibody type 1 [PCA1] [anti-Yo], n = 1; Purkinje cell cytoplasmic antibody type 2 [PCA2], n = 2; kelch-like protein 11 [KLHL11], n = 1; and combinations thereof: ANNA1/CRMP5, n = 1; ANNA1/amphiphysin, n = 1; ANNA3/CRMP5, n = 1). Cancer was confirmed in 25 cases (onconeural antibodies, n = 19; unclassified antibodies, n = 3; no antibodies, n = 3). Paraneoplastic myeloneuropathies had asymmetric paresthesias (84%), neuropathic pain (78%), subacute onset (72%), sensory ataxia (69%), bladder dysfunction (69%), and unintentional weight loss >15 pounds (63%). Neurologic examination demonstrated concomitant distal or asymmetric hyporeflexia and hyperreflexia (81%), impaired vibration and proprioception (69%), Babinski response (68%), and asymmetric weakness (66%). MRI showed longitudinally extensive (45%), tract-specific spinal cord T2 hyperintensities (39%) and lumbar nerve root enhancement (38%). Ten of 28 (36%) were unable to ambulate independently at last follow-up (median 24 months, range 5–133 months). Combined oncologic and immunologic therapy had more favorable modified Rankin Scale scores at post-treatment follow-up compared to those receiving either oncologic or immunologic therapy alone (2 [range 1–4] vs 4 [range 2–6], p < 0.001).

Conclusions

Paraneoplastic etiologies should be considered in the evaluation of subacute myeloneuropathies. Recognition of key characteristics of paraneoplastic myeloneuropathy may facilitate early tumor diagnosis and initiation of immunosuppressive treatment.