Neurological autoimmunity in patients with non-pulmonary neuroendocrine neoplasms: clinical manifestations and neural autoantibody profiles

BACKGROUND AND PURPOSE

Paraneoplastic neurological autoimmunity is well described with small-cell lung cancer, but information is limited for other neuroendocrine neoplasms (NENs).

METHODS

Adult patients with histopathologically confirmed non-pulmonary NENs, neurological autoimmunity within 5 years of NEN diagnosis, and neural antibody testing performed at the Mayo Clinic Neuroimmunology Laboratory (January 2008 to March 2023) were retrospectively identified. Control sera were available from patients with NENs without neurological autoimmunity (116).

RESULTS

Thirty-four patients were identified (median age 68 years, range 31-87). The most common primary tumor sites were pancreas (nine), skin (Merkel cell, eight), small bowel/duodenum (seven), and unknown (seven). Five patients received immune checkpoint inhibitor (ICI) therapy before symptom onset; symptoms preceded cancer diagnosis in 62.1% of non-ICI-treated patients. The most frequent neurological phenotypes (non-ICI-treated) were movement disorders (12; cerebellar ataxia in 10), dysautonomia (six), peripheral neuropathy (eight), encephalitis (four), and neuromuscular junction disorders (four). Neural antibodies were detected in 55.9% of patients studied (most common specificities: P/Q-type voltage-gated calcium channel [seven], muscle-type acetylcholine receptor [three], anti-neuronal nuclear antibody type 1 [three], and neuronal intermediate filaments [two]), but in only 6.9% of controls. Amongst patients receiving cancer or immunosuppressive therapy, 51.6% had partial or complete recovery. Outcomes were unfavorable in 48.3% (non-ICI-treated) and neural autoantibody positivity was associated with poor neurological outcome.

DISCUSSION

Neurological autoimmunity associated with non-pulmonary NENs is often multifocal and can be treatment responsive, underscoring the importance of rapid recognition and early treatment.

Interest of rare autoantibodies in autoimmune encephalitis and paraneoplastic neurological syndromes: the utility (or futility) of rare antibody discovery

PURPOSE OF REVIEW

The increasing recognition and diagnosis of autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) is partly due to neural autoantibody testing and discovery. The past two decades witnessed an exponential growth in the number of identified neural antibodies. This review aims to summarize recent rare antibody discoveries in the context of central nervous system (CNS) autoimmunity and evaluate the ongoing debate about their utility.

RECENT FINDINGS

In the last 5 years alone 15 novel neural autoantibody specificities were identified. These include rare neural antibody biomarkers of autoimmune encephalitis, cerebellar ataxia or other movement disorders, including multifocal presentations.

SUMMARY

Although the clinical applications of these rare antibody discoveries may be limited by the low number of positive cases, they still provide important diagnostic, prognostic, and therapeutic insights.

Genetic predisposition to autoimmune encephalitis and paraneoplastic neurological syndromes

PURPOSE OF REVIEW

We summarize the recent discoveries on genetic predisposition to autoimmune encephalitis and paraneoplastic neurological syndromes (PNS), emphasizing clinical and pathophysiological implications.

RECENT FINDINGS

The human leukocyte antigen (HLA) is the most studied genetic factor in autoimmune encephalitis and PNS. The HLA haplotype 8.1, which is widely known to be related to systemic autoimmunity, has been only weakly associated with a few types of autoimmune encephalitis and PNS. However, the strongest and most specific associations have been reported in a subgroup of autoimmune encephalitis that comprises antileucine-rich glioma-inactivated 1 (LGI1) limbic encephalitis, associated with DRB1∗07 : 01 , anticontactin-associated protein-like 2 (CASPR2) limbic encephalitis, associated with DRB1∗11 : 01 , and anti-IgLON5 disease, associated with DRB1∗10 : 01∼DQA1∗01∼DQB1∗05 . Non-HLA genes have been poorly investigated so far in autoimmune encephalitis, mainly in those lacking HLA associations such as anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, with only a few genome-wide association studies (GWAS) reporting equivocal results principally limited by small sample size.

SUMMARY

Genetic predisposition seems to be driven mostly by HLA in a group of autoimmune encephalitis characterized by being nonparaneoplastic and having predominantly IgG4 autoantibodies. The contribution of non-HLA genes, especially in those diseases lacking known or strong HLA associations, will require large cohorts enabling GWAS to be powerful enough to render meaningful results.

Anti-Hu antibody associated paraneoplastic neurological syndrome in a child with ganglioneuroblastoma: A rare case report and literature review

RATIONALE

Paraneoplastic neurological syndrome with anti-Hu antibody (Hu-PNS) is a neurological disorder that occur in patients with malignancy. The syndrome has a wide range of presentations and can present before diagnosis of primary malignancy. Familiarity with these paraneoplastic neurological syndromes can help early recognition and take appropriate regimens.

PATIENTS CONCERNS

Diagnosis and treatment of Hu-PNS.

DIAGNOSES

This is retrospective study that analyzed the clinical data of this case. Through retrospective analysis and targeted antibody screening, serum anti-Hu antibody was detected. Subsequent spinal imaging revealed a mass in the paraspinal region, which was confirmed as ganglioneuroblastoma by pathologic examination.

INTERVENTIONS

The child was treated with a course of intravenous immunoglobulin and radical surgical operation without chemotherapy.

OUTCOMES

The neurological symptoms were gradually improved and no signs indicate disease progression or tumor recurrence.

LESSONS

Hu-PNS has rarely been reported in children with ganglioneuroblastomas. They can mimic non-neoplastic processes, making detection and diagnosis difficult. Serum and/or cerebrospinal fluid onconeural antibody can strongly indicate occult cancers. Early detection of paraneoplastic neurological syndromes can help take appropriate regimens and improve prognosis.

[Paraneoplastic Disorders of Peripheral Nervous System]

Paraneoplastic disorders of the peripheral nervous system are immune-mediated neurological syndromes associated with tumors. Several clinical phenotypes have been associated with these disorders. Sensory neuronopathy is the most well-known clinical phenotype, and is caused by neuronal cell injury to the dorsal root ganglia. Symptoms of the peripheral nervous system usually lead to the discovery of tumors. Antineuronal antibodies are occasionally identified in the serum and/or cerebrospinal fluid of these patients. The prevalence of small-cell lung cancer is notable in these patients. Early tumor resection, coupled with the initiation of immunotherapy, may prove effective in improving and stabilizing clinical symptoms.

Comparative Study of Paraneoplastic and Nonparaneoplastic Autoimmune Encephalitis With GABABR Antibodies

BACKGROUND AND OBJECTIVES

While patients with paraneoplastic autoimmune encephalitis (AE) with gamma-aminobutyric-acid B receptor antibodies (GABABR-AE) have poor functional outcomes and high mortality, the prognosis of nonparaneoplastic cases has not been well studied.

METHODS

Patients with GABABR-AE from the French and the Dutch Paraneoplastic Neurologic Syndromes Reference Centers databases were retrospectively included and their data collected; the neurologic outcomes of paraneoplastic and nonparaneoplastic cases were compared. Immunoglobulin G (IgG) isotyping and human leukocyte antigen (HLA) genotyping were performed in patients with available samples.

RESULTS

A total of 111 patients (44/111 [40%] women) were enrolled, including 84 of 111 (76%) paraneoplastic and 18 of 111 (16%) nonparaneoplastic cases (cancer status was undetermined for 9 patients). Patients presented with seizures (88/111 [79%]), cognitive impairment (54/111 [49%]), and/or behavioral disorders (34/111 [31%]), and 54 of 111 (50%) were admitted in intensive care unit (ICU). Nonparaneoplastic patients were significantly younger (median age 54 years [range 19-88] vs 67 years [range 50-85] for paraneoplastic cases, p < 0.001) and showed a different demographic distribution. Nonparaneoplastic patients more often had CSF pleocytosis (17/17 [100%] vs 58/78 [74%], p = 0.02), were almost never associated with KTCD16-abs (1/16 [6%] vs 61/70 [87%], p < 0.001), and were more frequently treated with second-line immunotherapy (11/18 [61%] vs 18/82 [22%], p = 0.003). However, no difference of IgG subclass or HLA association was observed, although sample size was small (10 and 26 patients, respectively). After treatment, neurologic outcome was favorable (mRS ≤2) for 13 of 16 (81%) nonparaneoplastic and 37 of 84 (48%) paraneoplastic cases (p = 0.03), while 3 of 18 (17%) and 42 of 83 (51%) patients had died at last follow-up (p = 0.008), respectively. Neurologic outcome no longer differed after adjustment for confounding factors but seemed to be negatively associated with increased age and ICU admission. A better survival was associated with nonparaneoplastic cases, a younger age, and the use of immunosuppressive drugs.

DISCUSSION

Nonparaneoplastic GABABR-AE involved younger patients without associated KCTD16-abs and carried better neurologic and vital prognoses than paraneoplastic GABABR-AE, which might be due to a more intensive treatment strategy. A better understanding of immunologic mechanisms underlying both forms is needed.

Clinical Presentation, Management, and Diagnostic Performance of 2021 Criteria for Paraneoplastic Neurologic Syndromes in Childhood

BACKGROUND AND OBJECTIVES

Paraneoplastic neurologic syndromes (PNSs) are remote neurologic immune-related effects of tumors. The clinical characteristics of pediatric PNSs remain unclear. We retrospectively examined the clinical characteristics of cases of pediatric PNSs and assessed the performance of the 2021 diagnostic criteria in children.

METHODS

Patients hospitalized in the Beijing Children's Hospital between June 2015 and June 2023 and fulfilling the description of definite by 2004 diagnostic criteria of PNSs were included. A retrospective analysis of clinical characteristics was conducted, and the 2021 diagnostic criteria were applied to rediagnostic stratification.

RESULTS

Among the 42 patients included, the most common neurologic syndrome was opsoclonus-myoclonus syndrome (OMS) (62%), followed by rapidly progressive cerebellar syndrome (26%). Most tumors were neuroblastomas (88%), with few being ovarian teratomas (10%). Approximately 71% (30/42) of patients were classified as definite and 24% (10/42) as probable according to the 2021 criteria. All cases judged as probable exhibited rapidly progressive cerebellar ataxia with neuroblastoma. For OMS, chemotherapy was administered based on the tumor's risk stage, accompanied by regular infusion of IV gamma globulin and oral steroids following tumor diagnosis. Twenty-one patients underwent regular follow-ups over 4.92 (0.58-7.58) years. The initial hospitalization recorded a median score of 12 (7-14) on the Mitchell and Pike OMS rating scale, decreasing to 0 (0-5) at the final follow-up. In cases of rapidly progressive cerebellar syndrome, a similar therapeutic regimen was used. Nine patients underwent regular follow-ups over 4.42 (1.17-7.50) years. The mean modified Rankin scale score at first hospitalization was 4 (3-4), reducing to 1 (0-4) at the final follow-up. Only 17% (5/30) of patients across both groups exhibited poor response to this regimen. Among these 5 patients, 4 belonged to the low-risk group (without chemotherapy).

DISCUSSION

OMS followed by rapidly progressive cerebellar ataxia are the most common forms of PNSs in children and are associated with neuroblastoma. An aggressive approach with multiple immunotherapies may improve the prognosis of neuroblastoma-associated PNSs. The 2021 criteria perform well in pediatric PNSs. However, we propose upgrading the classification of antibody-negative rapidly progressive cerebellar ataxia with neuroblastoma to definite diagnosis. This adjustment aims to further improve the diagnostic efficacy of this diagnostic criterion in childhood.

Antibody-positive autoimmune encephalitis and paraneoplastic neurological syndrome: A Swedish case series

OBJECTIVE

This study aimed to explore the clinical characteristics and temporal disease course of patients with autoimmune encephalitis (AE) and paraneoplastic neurological syndrome (PNS) in Sweden.

METHODS

Thirty-seven antibody-positive AE and PNS cases were identified in the Healthcare region Mid Sweden between 2015 and 2019. Clinical data were collected through a retrospective review of electronic health records. Patients were divided into three subgroups based on antibody type: neuronal surface antibodies (NSAbs), onconeural antibodies, and anti-GAD65 antibodies.

RESULTS

Nineteen patients had NSAbs, 11 onconeural antibodies, and seven anti-GAD65 antibodies. Anti-LGI1 and anti-NMDAR were the most frequently detected NSAbs, with anti-NMDAR cases having an older-than-expected age distribution (median age 40, range 17-72). Only 11 of 32 (30%) of patients had findings suggesting encephalitis on initial MRI, but 28 of 31 (90%) had pathological findings on initial cerebrospinal fluid analysis. All patients but one had abnormal EEG findings. Median time to immunotherapy was comparable among the three subgroups, whereas patients with anti-LGI1, anti-CASPR2, and anti-IgLON5 had an eightfold longer time to immunotherapy than anti-NMDAR and anti-GABA-B (p = .0016). There was a seasonal variation in onset for patients with non-tumor-related NSAbs and anti-GAD65 antibodies, with most patients (72%) falling ill in spring or summer.

CONCLUSION

Swedish patients with AE and PNS had similar clinical characteristics as previously described cohorts from other geographical regions except for anti-NMDAR encephalitis, with older onset than expected. The onset of non-tumor-related AE occurred predominantly in the warm seasons, and AE with a more insidious onset was associated with delayed treatment initiation.

Evaluation of the Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes in China

Background

Recently, the paraneoplastic neurologic syndrome (PNS) diagnostic criteria have received a major update with a new score system over the past 16 years. We aimed to evaluate the diagnostic performance and clinical utility in China.

Methods

An eligible cohort of 113 Chinese patients diagnosed with PNSs from the Second Affiliated Hospital School of Medicine Zhejiang University and published data were enrolled retrospectively. Data including clinical phenotype, antibody type, the presence of cancer, and duration of follow-up were reviewed and re-evaluated to classify the diagnostic levels for the 2004 and 2021 PNS criteria. The performances of these 2 criteria were compared. The critical parameters of antibody and cancer for the updated criteria were further explored.

Results

The cohort consisted of 69 males and 44 females with a median age of 60 years. Limbic encephalitis (23, 20.4%), anti-Hu antibody (32, 28.3%), and small-cell lung cancer (32, 28.3%) were the most common clinical phenotype, detected antibody, and concomitant cancer, respectively. A total of 97 (85.8%) patients were diagnosed with definite PNS according to the 2004 criteria: only 42.3% (41/97) fulfilled the 2021 criteria, while the remaining 40, 14, and 2 re-diagnosed with probable PNS, possible PNS, and non-PNS. The requirement of cancers consistent with antibody and phenotype increased the specificity and thus greatly enhanced the accuracy of the 2021 criteria.

Conclusion

The updated criteria for PNS emphasized the consistency between cancer phenotype and antibody and showed a better diagnostic value. A better diagnostic yield could benefit disease management.

Immunophenotypical characterization of paraneoplastic neurological syndrome patients: a multicentric study

Paraneoplastic neurological syndromes (PNS) are a group of rare and severe immune-mediated disorders that affect the nervous system in patients with cancer. The best way to diagnose a paraneoplastic neurological disorder is to identify anti-onconeural protein antibodies that are specifically associated with various cancers. The aim of this multicentric study was to clinically and immunologically characterize patients with PNS and study their association with cancer. Patients suspected to have PNS were enrolled from various clinical centres and were characterized immunologically. This study population consisted of 112 patients. Onset of PNS was mainly subacute (76 %). PNS patients had various neurological disorders and symptoms. PNS developed before the diagnosis of cancer in 28 definite PNS patients and in six suspected PNS patients. The most frequent autoantibodies detected in PNS patients were anti-Hu and anti-Yo. One definite PNS patient with cerebellar syndrome had anti-Tr antibody and seven patients had atypical antibodies. The literature associates these antibodies with various neurological disorders and cancers. Our observations confirm the important role of autoantibodies in PNS and their importance for the early diagnosis of cancer in PNS patients.

Significance of Autoantibodies in Autoimmune Encephalitis in Relation to Antigen Localization: An Outline of Frequently Reported Autoantibodies with a Non-Systematic Review

Autoantibodies related to central nervous system (CNS) diseases propel research on paraneoplastic neurological syndrome (PNS). This syndrome develops autoantibodies in combination with certain neurological syndromes and cancers, such as anti-HuD antibodies in encephalomyelitis with small cell lung cancer and anti-Yo antibodies in cerebellar degeneration with gynecological cancer. These autoantibodies have roles in the diagnosis of neurological diseases and early detection of cancers that are usually occult. Most of these autoantibodies have no pathogenic roles in neuronal dysfunction directly. Instead, antigen-specific cytotoxic T lymphocytes are thought to have direct roles in neuronal damage. The recent discoveries of autoantibodies against neuronal synaptic receptors/channels produced in patients with autoimmune encephalomyelitis have highlighted insights into our understanding of the variable neurological symptoms in this disease. It has also improved our understanding of intractable epilepsy, atypical psychosis, and some demyelinating diseases that are ameliorated with immune therapies. The production and motility of these antibodies through the blood-brain barrier into the CNS remains unknown. Most of these recently identified autoantibodies bind to neuronal and glial cell surface synaptic receptors, potentially altering the synaptic signaling process. The clinical features differ among pathologies based on antibody targets. The investigation of these antibodies provides a deeper understanding of the background of neurological symptoms in addition to novel insights into their basic neuroscience.

Treatment of Movement Disorder Emergencies in Autoimmune Encephalitis in the Neurosciences ICU

Immune response against neuronal and glial cell surface and cytosolic antigens is an important cause of encephalitis. It may be triggered by activation of the immune system in response to an infection (para-infectious), cancer (paraneoplastic), or due to a patient's tendency toward autoimmunity. Antibodies directed toward neuronal cell surface antigens are directly pathogenic, whereas antibodies with intracellular targets may become pathogenic if the antigen is transiently exposed to the cell surface or via activation of cytotoxic T cells. Immune-mediated encephalitis is well recognized and may require intensive care due to status epilepticus, need for invasive ventilation, or dysautonomia. Patients with immune-mediated encephalitis may become critically ill and display clinically complex and challenging to treat movement disorders in over 80% of the cases (Zhang et al. in Neurocrit Care 29(2):264-272, 2018). Treatment options include immunotherapy and symptomatic agents affecting dopamine or acetylcholine neurotransmission. There has been no prior published guidance for management of these movement disorders for the intensivist. Herein, we discuss the immune-mediated encephalitis most likely to cause critical illness, clinical features and mechanisms of movement disorders and propose a management algorithm.

An autoimmune-based, paraneoplastic neurologic syndrome following checkpoint inhibition and concurrent radiotherapy for merkel cell carcinoma: case report

PURPOSE

Merkel cell carcinoma is highly sensitive to both radiation and immunotherapy. Moreover, concurrent radioimmunotherapy may capitalize on anti-tumor immune activity and improve Merkel cell treatment response, although an enhanced immune system may cross-react with native tissues and lead to significant sequelae.

METHODS

Here we present a case study of a patient with metastatic Merkel cell carcinoma treated with radiotherapy concurrent with pembrolizumab.

RESULTS

After radioimmunotherapy, the patient developed sensory neuropathy, visual hallucinations, and mixed motor neuron findings. Neurologic dysfunction progressed to profound gastrointestinal dysmotility necessitating parenteral nutrition and intubation with eventual expiration.

CONCLUSION

This case represents a unique autoimmune paraneoplastic neurologic syndrome, likely specific to neuroendocrine tumors and motivated by concurrent radioimmunotherapy. Recognition of the potential role of radioimmunotherapy may provide an advantage in anticipating these severe sequelae.

Autoimmune encephalitis in the elderly: who to test and what to test for

The awareness and understanding of autoimmune encephalitis are blossoming in neurology, and patients are being diagnosed and successfully treated with immunotherapy. The diverse symptomatology associated with autoimmune encephalitis means that patients may present initially to mental health services, which are, as yet, less well equipped to identify and investigate such phenomena. Older adult mental health services are used to managing complexity, but the range of pathologies presenting with unusual symptoms that may mimic autoimmune encephalitis is wide and there is no clear guidance as to when and how to investigate for possible autoimmune encephalitis. This paper examines the evidence supporting investigation and management strategies for patients with possible autoimmune encephalitis presenting to older adult psychiatrists.

[Paraneoplastic neurologic syndromes: laboratory diagnostics and immunological aspects]

Paraneoplastic neurologic syndromes (PNS) and autoimmune encephalitis (AE) are rare neurological disorders, which have similar symptoms, but vary in outcome and treatment strategy. In our retrospective statistical study we evaluated the autoantibody test results of serum and CSF from 2362 patients with suspected PNS and 1034 patients with suspected AE. For autoantibody testing, immunoblot assay (PNS) and cell-based indirect immunofluorescence assay (AE) were used. Autoantibodies were present in 8% of patients with suspected PNS: anti-Yo > anti-Hu > anti-Ma2 > anti-CV2 > anti-titin > anti-Zic4 > anti-amphiphysin > anti-Ri > anti-GAD65 > anti-Sox1 > anti-recoverin. Mostly elderly women were affected. Autoantibodies were present in 5.8% of patients with suspected AE: anti-NMDAR (young women) > anti-LGI1 (middle-aged men) > anti-GABABR (elderly men) > anti-Caspr2 (adult men). Our results correspond to the data described in the literature. The number of patients with suspected PNS and AE shows an increasing tendency, where the autoantibody testing with modern laboratory diagnostic methods helps in the early introduction of the appropriate therapy.

Kelch-like Protein 11 Antibodies in Seminoma-Associated Paraneoplastic Encephalitis

A 37-year-old man with a history of seminoma presented with vertigo, ataxia, and diplopia. An autoantibody specific for kelch-like protein 11 (KLHL11) was identified with the use of programmable phage display. Immunoassays were used to identify KLHL11 IgG in 12 other men with similar neurologic features and testicular disease. Immunostaining of the patient's IgG on mouse brain tissue showed sparse but distinctive points of staining in multiple brain regions, with enrichment in perivascular and perimeningeal tissues. The onset of the neurologic syndrome preceded the diagnosis of seminoma in 9 of the 13 patients. An age-adjusted estimate of the prevalence of autoimmune KLHL11 encephalitis in Olmsted County, Minnesota, was 2.79 cases per 100,000 men. (Funded by the Rochester Epidemiology Project and others.).

Clinical Heterogeneity in Patients with Glutamate Decarboxylase Antibody

OBJECTIVE

To explore the diversity and clinical features of anti-glutamate decarboxylase (GAD) antibody-associated neurological diseases.

METHODS

Clinical data of a series of 5 patients positive for anti-GAD antibodies were retrospectively analyzed.

RESULTS

All 5 patients were female, with a median age of 41.5 years (range 19-60 years). Their neurological symptoms included stiff-person syndrome (SPS), encephalitis, myelitis, cramp, visual loss, and paresthesia. Three patients (60%) were diagnosed with tumors, 2 cases of thymic tumor and 1 of breast cancer. On immunohistochemistry for tumor pathology, expression of GAD65 was found only in 1 patient. Four patients (80%) had abnormal brain MRI findings. All patients received immunotherapy and improved significantly after treatment, but 4 (80%) then experienced a relapse.

CONCLUSIONS

Neurological manifestations in anti-GAD-positive patients are diverse and include SPS, encephalitis, myelitis, cramp, visual loss, and paresthesia.

Paraneoplastic Disorders

PURPOSE OF REVIEW

Paraneoplastic neurologic syndromes target specific areas of the nervous system with pathogenic autoantibodies or T-cell responses. Each syndrome conveys a risk of particular tumors. Expanded paraneoplastic antibody testing has led to improved diagnosis but created challenges involving appropriate interpretation of test results.

RECENT FINDINGS

Peripheral nervous system paraneoplastic disorders such as myasthenia gravis and Lambert-Eaton myasthenic syndrome involve pathogenic autoantibodies. Recently, the pathogenic mechanisms and antigens of these disorders have been further elucidated. Paraneoplastic syndromes associated with onconeuronal antibodies, such as anti-Hu, have strong cancer associations and limited response to treatment. Autoimmunity to central nervous system membrane proteins, such as the N-methyl-D-aspartate (NMDA) receptor or leucine-rich, glioma inactivated 1 (LGI1), defines an expanding group of disorders with better prognosis and more variable cancer associations. In these diseases, the autoantibodies are either proven to be or are potentially pathogenic. An animal model of anti-NMDA receptor encephalitis will allow novel treatments to be developed. Autoantibodies to intracellular synaptic antigens, such as glutamic acid decarboxylase 65 (GAD65), are associated with diverse disorders such as stiff person syndrome, and the pathophysiology of these diseases is unclear.

SUMMARY

Paraneoplastic disorders have diverse clinical manifestations, including weakness, sensory neuronopathy, encephalitis, epilepsy, and psychosis. Proper use of antibody testing may assist with diagnosis. Treatment may require immunotherapy and tumor treatment.

Various clinical features of patients with anti-Hu associated paraneoplastic neurological syndromes: An observational study

To describe and analyze the clinical features and prognosis of patients with anti-Hu associated paraneoplastic neurological syndromes (PNS).The symptoms, MRI findings, cerebrospinal fluid (CSF) changes, electroencephalogram (EEG) characteristics and prognoses of 9 well-diagnosed anti-Hu associated PNS patients were analyzed.The study enrolled 6 female and 3 male patients. Three patients presented with vertigo and 6 patients exhibited a depressed mood, numbness of the lower limbs, generalized pains, seizures, mental disturbances, and a temporary unilateral hand tremor on initial presentation. Three patients presented with MRI abnormalities localized in the mesial temporal lobe and the thalamus. Abnormal interictal EEG readings were observed in all 5 patients who underwent EEG study. Four patients were found lung cancer (3 during hospitalization, 1 during follow-up). Seven patients were treated with immunotherapy and improved in symptoms. Three patients died during follow-up (2 with lung cancer).The clinical manifestation of anti-Hu associated PNS is diverse and multifocal. EEG may be more sensitive than MRI for early diagnosis of PNS. Long-term follow-up for patients with CT-negative anti-Hu associated PNS is necessary.

Effect of thymectomy on refractory autoimmune status epilepticus

Refractory status epilepticus (RSE) is an increasingly recognized manifestation of autoimmune encephalitis, which can occur either as a paraneoplastic or non-paraneoplastic disorder. The effect of tumor removal in paraneoplastic status epilepticus has never been explored systematically, although early tumor treatment is usually recommended. In this study, we report clinical, pathological and EEG findings of a patient who developed RSE as one of multiple paraneoplastic manifestations of thymoma and the effect of thymectomy on seizure outcome. To our knowledge, this is the first report of successful treatment of RSE with tumor removal in paraneoplastic encephalitis.

Anti-Ma2-associated limbic encephalitis with coexisting chronic inflammatory demyelinating polyneuropathy in a patient with non-Hodgkin lymphoma: A case report

RATIONALE

We report the rare case of a 74-year-old man with anti-Ma2-associated paraneoplastic neurologic syndrome (PNS), and review and analyze the clinical manifestations, diagnosis, and treatment of the disease.

PATIENT CONCERNS

The patient presented with a 5-month history of muscle weakness, progressive body aches, and weakness and numbness in both lower extremities. Before his hospitalization, he had experienced cognitive function decline; ptosis, inward gaze, and vertical gaze palsy in the right eye; and occasional visual hallucinations. Brain and spinal cord magnetic resonance imaging (MRI) yielded normal results. Anti-Ma2 antibodies were detected in both serum and cerebrospinal fluid. A 4-hour electroencephalogram showed irregular sharp slow waves and δ waves in the temporal region. Electromyography showed peripheral nerve demyelination. Positron-emission tomography/computed tomography (PET-CT) examination revealed hypermetabolism in the lymph nodes of the whole body. Biopsy of the lymph nodes showed non-Hodgkin lymphoma.

DIAGNOSIS

A clinical diagnosis of lymphoma and PNS was made.

INTERVENTIONS

The patient was treated with intravenous dexamethasone (15 mg/day) for 3 days.

LESSONS

We have presented a rare case of a PNS involving both the central and peripheral nervous systems. The clinical features of this case indicated anti-Ma2-associated encephalitis and chronic inflammatory demyelinating polyneuropathy. PET-CT played a critical role in enabling early diagnosis and prompt treatment in this case.

Autoimmune paraneoplastic syndromes associated to lung cancer: A systematic review of the literature Part 4: Neurological paraneoplastic syndromes, involving the peripheral nervous system and the neuromuscular junction and muscles

The development of new immune treatment in oncology and particularly for lung cancer may induce new complications, particularly activation or reactivation of auto-immune diseases. In this context, a systematic review on the auto-immune paraneoplastic syndromes that can complicate lung cancer appears useful. This article is the fourth of a series of five and deals mainly with neurological paraneoplastic syndromes involving the peripheral nervous system and the neuromuscular junction and muscles.

Immune-Mediated Neuropathies following Autologous Stem Cell Transplantation for Multiple Myeloma: Case Series and Review of the Literature

Neuropathy is a common finding in patients with multiple myeloma. Several different factors can cause neuropathy in these patients, such as the underlying disease itself, medications used for treatment, or immune-mediated processes. Immune-mediated neuropathies (IMN) consist of a heterogeneous spectrum of peripheral nerve disorders. Although IMN is associated with several hematological disorders, it remains a very rare complication of hematopoietic stem cell transplantation (HCT). We describe our experiences of 3 patients with multiple myeloma who experienced IMN following autologous HCT (auto-HCT). These 3 patients were felt to have IMN clearly attributable to auto-HCT because of a clear temporal association with auto-HCT and absence of any other obvious causative factor. The variety in their clinical presentations, diagnostic approach, and approaches to management are explained. The pathophysiology of how HCT may predispose to IMN remains poorly understood. Our report helps highlight several potential causes of this phenomenon, such as a paraneoplastic syndrome, immune reconstitution syndrome, or drug toxicity. We emphasize that a comprehensive approach is needed to address this rare entity, and that there should be a low threshold to initiate immune-specific therapy, such as plasmapheresis, if symptoms do not resolve spontaneously.

Paraneoplastic epilepsy

Epilepsy can be a manifestation of paraneoplastic syndromes which are the consequence of an immune reaction to neuronal elements driven by an underlying malignancy affecting other organs and tissues. The antibodies commonly found in paraneoplastic encephalitis can be divided into two main groups depending on the target antigen: 1) antibodies against neuronal cell surface antigens, such as against neurotransmitter (N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), gamma-aminobutyric acid (GABA)) receptors, ion channels (voltage-gated potassium channel (VGKC)), and channel-complex proteins (leucine rich, glioma inactivated-1 glycoprotein (LGI1) and contactin-associated protein-2 (CASPR2)) and 2) antibodies against intracellular neuronal antigens (Hu/antineuronal nuclear antibody-1 (ANNA-1), Ma2/Ta, glutamate decarboxylase 65 (GAD65), less frequently to CV2/collapsin response mediator protein 5 (CRMP5)). In this review, we provide a comprehensive survey of the current literature on paraneoplastic epilepsy indexed by the associated onconeuronal antibodies. While a range of seizure types can be seen with paraneoplastic syndromes, temporal lobe epilepsy is the most common because of the association with limbic encephalitis. Early treatment of the paraneoplastic syndrome with immune modulation/suppression may prevent the more serious potential consequences of paraneoplastic epilepsy.

[Paraneoplastic neurological syndromes: an update]

Paraneoplastic neurological syndromes are a group of neurological syndromes secondary to an underlying malignancy. Associated autoantibodies can be classified according to the cellular localization of the antigen target. Onconeuronal autoantibodies (targeting intracellular antigens) strongly associate with cancer and the response to immunotherapy is often disappointing. Identifying and treating the underlying malignancy is a high priority. However, immunomodulation can provide a favourable outcome for neurological symptoms associated with autoantibodies specific for cell membrane antigens. An early recognition of these disorders following the triad "clinical neurological syndrome--specific autoantibodies--tumour research" is important so that patients can benefit from appropriate targeted treatments.

Paraneoplastic disorders

PURPOSE OF REVIEW

Paraneoplastic disorders are autoimmune diseases associated with risks for specific cancers and marked by specific autoantibodies. They cause diverse clinical syndromes of the central and peripheral nervous systems.

RECENT FINDINGS

In the peripheral nervous system, autoimmunity to synaptic or axonal proteins has long been recognized to associate with specific cancers. In these disorders, typified by myasthenia gravis, the antibodies are directly toxic, and recovery with immunotherapy is the rule. In contrast, the classic paraneoplastic syndromes involve a higher risk of cancer, autoantibodies to intracellular proteins (eg, Hu proteins), T-cell-dependent disease mechanisms targeting the CNS or peripheral nervous system, and a poor response to treatment. Following the discovery of N-methyl-D-aspartate (NMDA) receptor antibodies, a new and expanding group of disorders involving autoantibodies to CNS synaptic and neuronal membrane proteins and a favorable response to immunotherapy emerged. A final group of disorders involves antibodies to intracellular synaptic proteins, such as glutamic acid decarboxylase 65 (GAD65), and it is unclear whether these diseases involve antibody or T-cell mechanisms.

SUMMARY

Neurologists should recognize the clinical syndromes associated with paraneoplastic disorders, utilize autoantibody and other testing to confirm the diagnosis, understand the pathologic basis of the diseases, and promptly give appropriate therapies.

Recent developments in paraneoplastic disorders of the nervous system

Paraneoplastic disorders of the nervous system (PNDs) are rare and unique disorders, where a specific pattern of neural damage occurs as a side effect of the interaction between the neoplasm and the host immune response. Clinical recognition of PNDs may be challenging but can lead to early detection of an occult neoplasm. Their study may lead to a better understanding of nervous system autoimmunity and even to devising novel immunotherapies against certain tumor types. Familiarity with the clinical syndromes, neuroradiological findings, autoantibodies, and tissue responses associated with PND may help arrive at a correct diagnosis in most cases.

[Paraneoplastic neurological syndromes and autoimmune encephalitis]

Paraneoplastic neurological syndromes (PNS) are defined as remote effects on the central and peripheral nervous system that are not caused directly by the tumor, its metastases and treatment, or metabolic disorders. The most probable cause is a falsely initiated immune reaction. Well-defined classical PNSs are associated with distinct tumors and occur with onconeural antibodies directed against intracellular neuronal antigens. However, response to therapy is limited. Recently, new antibodies directed against neuronal surface antigens were described in encephalitic syndromes of autoimmune origin. These probably antibody-mediated disorders are more frequent than classical PNS, occur with or without tumor association and often show a good response to immunosuppressive treatment.

[Paraneoplastic neurological syndrome and autoantibodies]

Paraneoplastic neurological syndrome (PNS) is a rare disorder caused by the remote effects of cancer is considered as caused by humoral or cell-mediated immunity. Several autoantibodies related to PNS have been discovered since the 1980s. These antibodies were classified into 2 categories based on the PNS diagnostic criteria recommended by PNS Euronetwork in 2004: well-characterized onconeural antibodies and partially characterized onconeural antibodies. Recently, techniques for the detection of these antibodies have been developed. Additional autoantibodies have been shown for neural surface antigens related to autoimmune-mediated encephalitis in patients with and without cancer. Because the PNS neurological symptoms often precede tumor diagnosis, the antibodies are useful diagnostic markers for PNS and occult tumors. Anti-tumor therapies are essential for PNS, and successful immunotherapies depend on the location of antigens, whether intracellular or on the surface of membranes. Generally, the latter cases are responsive to therapy. Only a limited numbers of cases with intracellular antigens have been improved by early and aggressive immunotherapies. Neurologists should be alert for PNS and check the presence of autoantibodies at the start of therapies when encountering rapidly progressive neurological symptoms of unknown origin. Here, we describe the relationship between onconeural antibodies, clinical features, tumor types, and response to immunotherapies.

[A man with sexual disinhibition caused by paraneoplastic limbic encephalitis]

A 63-year-old man with symptoms of depression and sexual disinhibition was admitted to a psychiatric clinic for the elderly. Because the man’s symptoms rapidly became more severe he was referred to the emergency room. There, his illness was diagnosed as paraneoplastic limbic encephalitis with positive anti-Hu antibodies; this is a paraneoplastic neurological syndrome presenting with short-term memory loss, epileptic seizures and psychiatric symptoms. For the prognosis of the illness it is essential that the syndrome is diagnosed as early as possible. Since patients sometimes present with mainly psychiatric symptoms it is important that psychiatrists are fully informed about the symptoms and are able to make an accurate diagnosis.

[Autoimmune encephalitis, clinical, radiological and immunological data]

INTRODUCTION

Encephalitis is an inflammatory or infectious disease with an acute or subacute presentation. Immunological abnormalities in serum can be found but may be underdiagnosed. In several cases, a paraneoplastic origin with anti-neuron antibodies is noted. In all cases, other auto-antibodies can be found with or without any neoplastic mechanism.

OBJECTIVES

The aim of our study was to describe a clinical, radiological and immunological cohort of patients with autoimmune encephalitis and suggest a diagnostic and therapeutic algorithm.

PATIENTS AND METHOD

We performed a retrospective study in an immunological unit of neurology. All patients with autoimmune encephalitis between March 2000 and October 2009 were included. The clinical, imaging and immunological evaluations were recorded for each patient.

RESULTS

Our cohort included 16 patients (eight men and eight women), mean age 45.3±10years. All patients had acute or subacute neuropsychological or neuropsychiatric impairment and all patients but one had temporal lobe dysfunction confirmed by cerebral MRI, PET or SPECT. Epilepsy was observed in 56% of cases, extra-temporal lobe impairment in 50%, including sleep disturbances. A cancer was found in only 25% (two small-cell lung cancers, one testis seminoma, one non-small-cell lung cancer with Merckel cells cancer). Anti-neuron antibodies were noted in 56% of cases (two with anti-voltage gate potassium channel complex antibodies (ab), two with anti-NMDA-R ab, two with anti-glutamate acid decarboxylase ab, one with anti-Ma2, two with anti-Hu ab and two remained uncharacterized). Systemic antibodies were found in 50% (one anti-gangliosides, one anti-SSA and one anti-DNA and four antinuclear ab uncharacterized, two anti-TPO and two anti-phospholipids). All patients received immunomodulatory treatments, including intravenous immunoglobulins (IgIV) and cancer was treated. Five patients achieved complete recovery, partial improvement was observed in 10 patients and two patients died.

DISCUSSION

Despite clinical homogeneity at presentation, clinical outcome seems to be different between patients with antibodies against neuronal surface antigens and those with antibodies against intracellular antigens, which are more likely refractory to immunotherapy and paraneoplastic. The frequency of extra-temporal lobe impairment suggests that the term of limbic encephalitis should be changed to autoimmune encephalitis.

SOX1 antibodies in sera from patients with paraneoplastic neurological syndromes

OBJECTIVES

SOX1 antibodies have been described in patients with Lambert-Eaton myasthenic syndrome (LEMS) in association with voltage-gated calcium channel antibodies as serological markers of small cell lung cancer (SCLC). This study was aimed to screen for additional SOX1 autoimmunity in onconeural antibody-positive sera from patients with paraneoplastic neurological syndromes (PNS) other than LEMS and to identify the clinical-immunological profile and associated tumours of patients with coexisting SOX1 antibodies.

METHODS

We retrospectively analysed sera from 55 patients with different PNS positive for well-characterized antineuronal antibodies for the presence of SOX1 antibodies by recombinant ELISA and immunoblot.

RESULTS

Eight (14.5%) patients showed additional SOX1 antibodies in the ELISA and the recombinant immunoblot. Five patients had coexisting Hu antibodies, while the other three showed coexisting CV2/CRMP5, amphiphysin, and coexisting CV2/CRMP5 and Hu antibodies, respectively. PNS included (partially overlapping) subacute sensory neuropathy, subacute sensorimotor neuropathy, cerebellar degeneration, brainstem encephalitis, encephalomyelitis and limbic encephalitis. No tumour was detected in two patients, while the others had lung cancer (four SCLC and two non-SCLC). One patient showed SOX1-specific intrathecal antibody synthesis.

CONCLUSIONS

We describe SOX1 reactivity for the first time overlapping with CV2/CRMP5 and amphiphysin antibodies. SOX1 reactivity is predominantly associated with Hu antibodies and SCLC, but can occur also in other types of lung cancer. Neurological manifestations present in patients with coexisting SOX1 antibodies and well-characterized antineuronal antibodies do not differ from those previously described in patients positive for antineuronal antibodies but no SOX1-specific anti-glial antibodies.

Anti-Hu-associated paraneoplastic encephalomyelitis with esophageal small cell carcinoma

A 63-year-old woman had anti-Hu-associated paraneoplastic encephalomyelitis (anti-Hu syndrome) caused by esophageal small cell carcinoma (SCC). The patient developed bilateral limbic encephalitis, followed by myelitis, brain stem encephalitis, and autonomic failure. Extensive examination demonstrated SCC of the abdominal lymph nodes that was retrospectively diagnosed as metastasis of esophageal SCC on autopsy. The neuropathological findings were characterized by widespread neuronal loss and gliosis in the central nervous system, as well as patchy loss of myelin and axons in the spinal nerve roots with perivascular lymphocytic infiltration. This is the first detailed clinical and neuropathological report of anti-Hu syndrome caused by esophageal SCC.

Elderly-onset neuromyelitis optica which developed after the diagnosis of prostate adenocarcinoma and relapsed after a 23-valent pneumococcal polysaccharide vaccination

We report a case of elderly-onset neuromyelitis optica (NMO) positive for the anti-aquaporin-4 (AQP-4) antibody; symptoms developed after the diagnosis of prostate adenocarcinoma and relapsed after a 23-valent pneumococcal polysaccharide vaccination. We suggest that activation of CD4-positive T cells and secretion of interferon-gamma induced by adenocarcinoma and complement activation induced by vaccination are responsible for the onset and relapse of NMO, even if a patient is positive for the anti-AQP-4 antibody. This case supports the previous experimental finding that the anti-AQP-4 antibody does not cause NMO-like lesions when injected alone, but does so after the induction of T cell-mediated experimental autoimmune encephalomyelitis or when co-injected with human complement.

Movement disorders in paraneoplastic and autoimmune disease

PURPOSE OF REVIEW

The most relevant advances in immune-mediated movement disorders are described, with emphasis on the clinical--immunological associations, novel antigens, and treatment.

RECENT FINDINGS

Many movement disorders previously considered idiopathic or degenerative are now recognized as immune-mediated. Some disorders are paraneoplastic, such as anti-CRMP5-associated chorea, anti-Ma2 hypokinesis and rigidity, anti-Yo cerebellar ataxia and tremor, and anti-Hu ataxia and pesudoathetosis. Other disorders such as Sydenham's chorea, or chorea related to systemic lupus erythematosus and antiphospholipid syndrome occur in association with multiple antibodies, are not paraneoplastic, and are triggered by molecular mimicry or unknown mechanisms. Recent studies have revealed a new category of disorders that can be paraneoplastic or not, and associate with antibodies against cell-surface or synaptic proteins. They include anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, which may cause dyskinesias, chorea, ballismus or dystonia (NMDAR antibodies), the spectrum of Stiff-person syndrome/muscle rigidity (glutamic acid decarboxylase, amphiphysin, GABA(A)-receptor-associated protein, or glycine receptor antibodies), neuromyotonia (Caspr2 antibodies), and opsoclonus--myoclonus--ataxia (unknown antigens).

SUMMARY

Neurologists should be aware that many movement disorders are immune-mediated. Recognition of these disorders is important because it may lead to the diagnosis of an occult cancer, and a substantial number of patients, mainly those with antibodies to cell-surface or synaptic proteins, respond to immunotherapy.

Onconeural antibodies in patients with neurological symptoms: detection and clinical significance

BACKGROUND

Onconeural antibodies are strongly associated with cancer and paraneoplastic neurological syndromes (PNS). Most of these antibodies are well-characterized (antibodies against Hu, Yo, Ri, CRMP5, amphiphysin, Ma2 and Tr) and are in common use for the diagnosis of definite PNS.

MATERIALS AND METHODS

Literature on detection and clinical significance of onconeural antibodies were identified by using relevant search terms in PubMed and reviewed.

CONCLUSIONS

The onconeural antibodies are directed against intracellular antigens and their pathogenic role is still largely unknown. They are highly specific markers of paraneoplastic aetiology in patients with neurological symptoms. Detection of an onconeural antibody in a patient with neurological symptoms should lead to prompt investigation for cancer. However, absence of detectable onconeural antibodies does not exclude the PNS diagnosis. In particular, failure to detect antibodies in patients without classical PNS symptoms may result in less vigorous cancer screening and diagnostic delay. Neuronal antibodies that are directed to synaptic proteins or proteins of the cell membrane are also associated with neurological symptoms, and probably have pathogenic effects. The association between these antibodies and cancer is less robust, and they are usually not included among the onconeural antibodies.

[Anti-NMDA receptor paraneoplastic encephalitis: complete recovery after ovarian teratoma removal]

INTRODUCTION

A paraneoplastic syndrome characterized by neuropsychiatric symptoms, involuntary movements and seizures has been recently associated with antibodies targeting NMDA (N-methyl-D-aspartate) receptor in patients with an ovarian teratoma. Severe neurological impairment is frequent and treatment in the intensive care unit is often required because of ventilatory failure and life-threatening autonomic instability. Tumor removal is curative in many cases and neurological improvement is demonstrated shortly after surgery.

CASE REPORT

Here we report on a patient with paraneoplastic encephalitis manifested by unconsciousness and coreo-athetosic movements related to NMDA receptor antibodies associated with an immature ovarian teratoma grade III. She made a complete recovery after oophorectomy, intravenous immunoglobulin and corticosteroids.

CONCLUSIONS

Treatment of paraneoplastic syndromes is based on specific therapy for underlying tumor associated to immunomodulators. As in this case, anti-NMDA encephalitis may significantly improve after tumor removal and intra-venous immunoglobuline.

Thymoma and paraneoplastic myasthenia gravis

Paraneoplastic autoimmune diseases associate occasionally with small cell lung cancers and gynecologic tumors. However, myasthenia gravis (MG) occurs in at least 30% of all patients with thymomas (usually present at MG diagnosis). These epithelial neoplasms almost always have numerous admixed maturing polyclonal T cells (thymocytes). This thymopoiesis-and export of mature CD4(+)T cells-particularly associates with MG, though there are rare/puzzling exceptions in apparently pure epithelial WHO type A thymomas. Other features potentially leading to inefficient self-tolerance induction include defective epithelial expression of the autoimmune regulator (AIRE) gene and/or of major histocompatibility complex class II molecules in thymomas, absence of myoid cells, failure to generate FOXP3(+) regulatory T cells, and genetic polymorphisms affecting T-cell signaling. However, the strong focus on MG/neuromuscular targets remains unexplained and suggests some biased autoantigen expression, T-cell selection, or autoimmunization within thymomas. There must be further clues in the intriguing serological and cellular parallels in some patients with late-onset MG but without thymomas-and in others with AIRE mutations-and in the contrasts with early-onset MG, as discussed here.

[Neurological syndromes, encephalitis]

The remote effects of malignant tumors in most cases of paraneoplastic neurological syndromes(PNS)are mediated by autoimmune processes against antigens shared by the tumor cells and the nervous tissue(onconeural antigens). Onconeural (or paraneoplastic)antibodies are broadly categorized into two groups according to the location of the corresponding onconeural antigens, inside or on the surface of neurons. Antibodies established as clinically relevant diagnostic markers for PNS are designated as well-characterized onconeural antibodies (or classical antibodies)that target intracellular antigens(Hu, Yo, Ri, CV2/CRMP5,Ma2, and amphiphysin). They also serve as useful markers in detecting primary tumors. Recent identification of new antibodies as markers of subtypes of limbic encephalitis has also expanded the concept of autoimmune limbic encephalitis. These autoantibodies are directed to neuronal cell-surface antigens including neurotransmitter receptors(NMDA, AMPA, and GABAB receptors)and ion channels(VGKC). They are less frequently associated with cancer, so that they cannot be used as specific markers for PNS. Autoimmune limbic encephalitis with anti-neuronal cell surface antobodies and paraneoplastic limbic encephalitis with classical antibodies overlap in some clinical features but are pathophysiologically distinct. Classical antibodies are not simple tumor markers. They seem to be closely related to the disease mechanisms because specific intrathecal synthesis has been shown in PNS patients. However, attempts to produce an animal model of PNS by passive transfer of these antibodies have been unsuccessful, and there is no direct evidence demonstrating the pathogenic role of classical antibodies. Instead, some circumstantial evidence, including pathological studies showing extensive infiltrates of T cells in the CNS of the patients, supports the hypothesis that cytotoxic-T cell mechanisms cause irreversible neuronal damage. On the other hand, humoral immune response is probably the principal mechanism in autoimmune encephalitis associated with antibodies against neuronal cell-surface antigens. Those antibodies are supposed to mediate neural dysfunction which may be reversed by immunosuppression therapy, while the exact mechanism remains to be elucidated. Further accumulation of the cases and longer observation would be necessary to delineate the clinical spectrum of each type of newly-identified autoimmune limbic encephalitis. Early diagnosis and optimal oncological treatment is a prerequisite for better prognosis of PNS patients. Detection of the primary tumor at very early stages including carcinoma in situ is a challenging issue. Optimization of immunosuppression/ immunomodulation therapy for each patient according to the underlying pathophysiological processes is another important clinical issue.

[Pathogenesis of paraneoplastic neurological syndromes]

Paraneoplastic neurological syndromes (PNS) are thought to be caused by autoimmune processes triggered by the cancer and directed against antigens common to both the cancer and the nervous system. There are several clinical phenotypes in combinations with the neurological syndromes, origin of cancer and the specific autoantibodies. PNS with antibodies against channel receptors on the cell surface tend to respond favorably to antibody-depletion therapies; this suggests that the antibodies detected in these PNS groups are closely related to their pathogenesis. PNS having the antibodies against intracellular proteins might be caused by cytotoxic T cell-mediated cell death. This is because the following findings; 1) the prominent mononuclear cells in CSF, 2) the infiltration of inflammatory cells, mainly CD8+ T lymphocytes, in the tumor and the nervous tissue. In addition, T cell receptor usage of infiltrated T lymphocytes in the affected CNS lesions has been shown to be oligoclonal. We observed that the disease model could not be produced using only anti-intracellular antibodies such as anti-Yo or anti-Hu antibodies, but that CTL activity could be induced in CD8+ T cells isolated from the peripheral mononuclear cells obtained from PNS patients with anti-Yo or anti-Hu antibodies. The anti-Yo- or anti-Hu-antibody-positive patients possess common human leukocyte antigen (HLA) class I motifs. This implies that in patients with anti-Yo or anti-Hu antibodies, the presentation of the certain antigen peptides on the cell surface could be used to stimulate CD8+ T lymphocytes that could attack their target tissues as effectors. Antigen-specific CTL-mediated cell death has been observed in cancer immunology and PNS appears to be a potential candidates for a future CTL-mediated neurological disease model.

[Neuropathy associated with paraneoplastic neurological syndrome]

Paraneoplastic neurological syndromes (PNSs) are the remote effects of cancer on the nervous system. The peripheral nervous system is an important targets of PNS. The neuropathies associated with PNS are reviewed in this article. Among the various paraneoplastic neuropathies, the main classical syndorome of PNS is subacute sensory neuronopathy that involves the cell bodies of sensory neurons in the dorsal root ganglia. Its clinical symptoms include sensory ataxia. Onconeuronal antibodies such as anti-Hu and anti-CV2/CRMP5 antibodies are frequently associated with this syndrome. In contrast to this classical form of PNS, non-classical syndromes are considered as heterogeneous neuropathies. The clinical features of non-classical syndromes are variable and no evident association between a clinical phenotype and onconeuronal antibodies has been established. Early detection and treatment of cancer is an essential for management of PNS. Neuropathies with paraproteinemia are also important clinical entities of PNS. IgM M-protein is most likely to cause neuropathy. Patients with IgM paraproteinemic neuropathy is usually characterized by predominan distal and sensory impairment, prolonged distal motor latencies in nerve conduction studies, and the presence of anti-MAG and SGPG antibodies.

[Paraneoplastic neurological syndrome--definition and history]

Paraneoplastic neurological syndrome (PNS) may affect any part of the nervous system and muscles. PNS is a rare disorder caused by the remote effects of cancer and is considered to be immune-mediated. Since the 1980s, several specific onco-neural antibodies and T-cell responses against onco-neural molecules have been reported, as shown in the historical review in this article. Immunoresponses to cancer are considered to cross-react with self-antigens in the nervous system or muscle. The presence of such onco-neural antibodies is a useful diagnostic marker for PNS and occult cancer. Despite sustained efforts to elucidate the effects of such antibodies on neuron, only a few onco-neural antibodies have been identified as primary effectors of neurological symptoms. However the absence of these antibodies does not exclude a PNS. In some instances, these antibodies can be detected in cancer patients without PNS. PNS diagnosis requires excluding many other complications of cancer and mimics of other neurological diseases as differential diagnoses. Recently, an international panel of experts provided useful diagnostic criteria for PNS. These criteria are based on well-characterized onco-neural antibodies and specific neurological syndromes. Probable cases of PNS are strongly advised to undergo early antitumor therapy and immunotherapy to prevent progressive neuronal death. As the symptoms of PNS often appear before the diagnosis of malignant cancer, repeated searches for occult cancer are recommended, if the tumor has not yet been found. Further studies are required to clarify the exact mechanisms underlying neuronal damage in PNS, which may lead to the development of more rational therapies and greater understanding of immunology in the nervous system.

Antibody to CCDC104 is associated with a paraneoplastic antibody to CDR2 (anti-Yo)

Patients with cancer may develop paraneoplastic neurological syndromes (PNS) in which onconeural antibodies are important diagnostic findings. As the functional role of onconeural antibodies is largely unknown, insight gained by identifying associated antibodies may help to clarify the pathogenesis of the PNS. In this study, we identified patients with Yo antibodies who also had antibodies to an uncharacterized protein called coiled-coil domain-containing protein 104 (CCDC104). We found a significant association between CCDC104 and Yo antibodies (4 of 38, 10.5%), but not other onconeural antibodies (0 of 158) (P = 0.007, Fisher's exact test). The prevalence of CCDC104 antibodies was approximately similar in patients with cancer (8 of 756, 1.1%) and in healthy blood donors (2 of 300, 0.7%). CCDC104 antibodies were not associated with PNS, as this was found in only two of the ten CCDC104-positive patients. The CCDC104 protein, whose function is unknown, is expressed in various human tissues, including the brain, and is localized mainly to the nucleus, but is also found in the cytoplasm. The association between Yo and CCDC104 antibodies may indicate functional similarities.