[Blood-brain barrier breakdown and autoimmune cerebellar ataxia].

Autoimmune cerebellar ataxia is a disease entity that affects the cerebellum and is induced by autoimmune mechanisms. The disease is classified into several etiologies, including gluten ataxia, anti-glutamate decarboxylase (GAD) ataxia, paraneoplastic cerebellar degeneration, primary autoimmune cerebellar ataxia and postinfectious cerebellar ataxia. The autoimmune response in the periphery cross-reacts with similar antigens in the cerebellum due to molecular mimicry. Breakdown of the blood‒brain barrier (BBB) could potentially explain the vulnerability of the cerebellum during the development of autoimmune cerebellar ataxia, as it gives rise to the entry of pathogenic autoantibodies or lymphocytes into the cerebellum. In this review, the maintenance of the BBB under normal conditions and the molecular basis of BBB disruption under pathological conditions are highlighted. Next, the pathomechanism of BBB breakdown in each subtype of autoimmune cerebellar ataxia is discussed. We recently identified glucose-regulated protein (GRP) 78 antibodies in paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome, and GRP78 antibodies induced by cross-reactivity with tumors can disrupt the BBB and penetrate anti-P/Q type voltage-gated calcium channel (VGCC) antibodies into the cerebellum, thus leading to cerebellar ataxia in this disease.

Ovarian mass Presenting as Paraneoplastic cerebellar degeneration with peripheral neuropathy and anti-Yo antibody.

Paraneoplastic neurological syndromes (PNS) are a group of disorders with diverse neurological manifestations that are observed in patients with various types of cancer. Any portion of the nervous system can be affected by these syndromes, which are brought on by processes other than metastasis, direct tumour spread or chemotherapy side effects. An immune-mediated attack on the cerebellar Purkinje cells and consequent cerebellar symptoms define paraneoplastic cerebellar degeneration(PCD), a subtype of the PNS. Axonal or demyelinating paraneoplastic peripheral neuropathies are both possible. Here, we describe the case of a middle-aged woman who presented with subacute-onset cerebellar symptoms and peripheral neuropathy, was discovered to have a positive anti-Yo antibody, and was later detected to have an ovarian mass. This case illustrates the significance of considering a paraneoplastic aetiology in patients with otherwise unexplained neurological manifestations and initiating an appropriate workup and early treatment for the primary malignancy.

Cerebellar Hypermetabolism in a Hodgkin Lymphoma Leads to Diagnosis of Paucisymptomatic Cryptococcus neoformans Meningitis.

ABSTRACT: Malignancy-associated cerebellar hypermetabolism on [ 18 F]FDG PET/CT has 2 major causes: paraneoplastic autoimmune encephalitis and neoplasias (leptomeningeal/cerebellar metastases and primary cerebellar tumors). We present the case of a 33-year-old man with a newly diagnosed Hodgkin lymphoma and mere episodical headache, unexpectedly displaying intense cerebellar hypermetabolism on his staging [ 18 F]FDG PET/CT. Both neurolymphomatosis and paraneoplastic subacute cerebellar degeneration were ruled out by clinical presentation, MR, and repeated lumbar punctures. Instead, cerebrospinal fluid analysis unveiled a Cryptococcus neoformans meningitis, highlighting the possibility of paucisymptomatic central nervous system infections as differential diagnosis in malignancy-related cerebellar hypermetabolism in addition to (para)neoplastic causes.

FDG PET Unveils the Course of Paraneoplastic Cerebellar Degeneration: A Semiquantitative Analysis.

ABSTRACT: In paraneoplastic cerebellar degeneration (PCD), the standard diagnostic workup might be inconclusive, especially in seronegative subtypes. Brain 18F-FDG PET is an accurate supportive diagnostic tool in immune-mediated disorders, but findings in PCD are controversial. Semiquantitative analysis of 18F-FDG PET can meaningfully assist visual assessment in different neurological conditions and has been mainly applied to disclose regional hypometabolism. We describe a seronegative PCD associated with small cell lung cancer in which 18F-FDG PET semiquantitative analysis accurately disclosed the longitudinal pathological changes of brain metabolism occurring in the acute and posttreatment remission stages and paralleling clinical impairment and response to treatment.

Paraneoplastic cerebellar degeneration diagnosed by anti-Yo determination in a young woman with early breast cancer.

A 44-year-old woman diagnosed with a HER2 positive early breast cancer, receiving neoadjuvant treatment with paclitaxel and targeted agents, trastuzumab together with pertuzumab, presented to the emergency room with gait instability and upper right limb weakness. The neurological examination was compatible with cerebellar alteration showing right dissymmetry of the finger-nose and heel-knee manoeuvre. A head CT and a brain MRI were performed and negative. The electromyography showed alterations of the pyramidal pathway and somatosensory pathway. In order to determine the cause of the cerebellar affection, a lumbar puncture was performed. The cerebrospinal fluid analysis was non-specific, but the antineuronal anti-Yo antibody was positive, being diagnosed of a paraneoplastic cerebellar degeneration (PCD). A positron emission tomography CT ruled out metastatic disease. The patient completed four cycles of antiHER2 blockade and weekly paclitaxel, achieving a complete pathological response. One year later, she maintains a complete remission but the PCD still prevails.

Immunological Bases of Paraneoplastic Cerebellar Degeneration and Therapeutic Implications.

Paraneoplastic cerebellar degeneration (PCD) is a rare immune-mediated disease that develops mostly in the setting of neoplasia and offers a unique prospect to explore the interplay between tumor immunity and autoimmunity. In PCD, the deleterious adaptive immune response targets self-antigens aberrantly expressed by tumor cells, mostly gynecological cancers, and physiologically expressed by the Purkinje neurons of the cerebellum. Highly specific anti-neuronal antibodies in the serum and cerebrospinal fluid represent key diagnostic biomarkers of PCD. Some anti-neuronal antibodies such as anti-Yo autoantibodies (recognizing the CDR2/CDR2L proteins) are only associated with PCD. Other anti-neuronal antibodies, such as anti-Hu, anti-Ri, and anti-Ma2, are detected in patients with PCD or other types of paraneoplastic neurological manifestations. Importantly, these autoantibodies cannot transfer disease and evidence for a pathogenic role of autoreactive T cells is accumulating. However, the precise mechanisms responsible for disruption of self-tolerance to neuronal self-antigens in the cancer setting and the pathways involved in pathogenesis within the cerebellum remain to be fully deciphered. Although the occurrence of PCD is rare, the risk for such severe complication may increase with wider use of cancer immunotherapy, notably immune checkpoint blockade. Here, we review recent literature pertaining to the pathophysiology of PCD and propose an immune scheme underlying this disabling disease. Additionally, based on observations from patients' samples and on the pre-clinical model we recently developed, we discuss potential therapeutic strategies that could blunt this cerebellum-specific autoimmune disease.

GRP78 antibodies damage the blood-brain barrier and relate to cerebellar degeneration in Lambert-Eaton myasthenic syndrome.

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease of the neuromuscular junction caused by autoantibodies binding to P/Q-type voltage-gated calcium channels. Breakdown of the blood-brain barrier and diffusion of cerebellar granule/Purkinje cell-reactive autoantibodies into the CNS are critical for the pathogenesis of paraneoplastic cerebellar degeneration (PCD) with Lambert-Eaton myasthenic syndrome. We recently found evidence that glucose-regulated protein 78 (GRP78) autoantibodies in the plasma of patients with neuromyelitis optica promote the CNS access of AQP4 autoantibodies. In the present study, we investigated whether the GRP78 autoantibodies in PCD-LEMS IgG boost the brain uptake of cerebellar cell-reactive antibodies across the blood-brain barrier and facilitate cerebellar dysfunction. We first evaluated the effects of purified IgG from PCD-LEMS or PCD patients on the blood-brain barrier function in human brain microvascular endothelial cells using a high content imaging system with nuclear factor κB p65 and intracellular adhesion molecule 1 (ICAM1) immunostaining. Next, we identified GRP78 autoantibodies causing blood-brain barrier permeability in PCD-LEMS IgG by co-immunoprecipitation and the living cell-based antibody binding assays. Exposure of brain microvascular endothelial cells to IgG from PCD-LEMS patients induced nuclear factor κB p65 nuclear translocation, ICAM1 upregulation, reduced claudin-5 expression, increased permeability and increased autocrine IL-1ß and IL-8 secretion; the IgG from patients with Lambert-Eaton myasthenic syndrome did not have these effects. We detected GRP78 autoantibodies in the IgG of LEMS-PCD (83.3%, n = 18), but observed fewer in patients with LEMS (6.6%, n = 15) and none were observed in the control subjects (n = 8). The depletion of GRP78 autoantibodies reduced the biological effect of LEMS-PCD IgG on brain microvascular endothelial cells. These findings suggest that GRP78 autoantibodies play a role beyond neuromyelitis optica and that they have direct implications in the phenotypic differences between PCD-LEMS and LEMS.

CDR2L Is the Major Yo Antibody Target in Paraneoplastic Cerebellar Degeneration.

The pathogenesis of Yo-mediated paraneoplastic cerebellar degeneration (PCD) is unclear. We applied cerebrospinal fluid and serum from PCD patients as well as CDR2 and CDR2L antibodies to neuronal tissue, cancer cell lines, and cells transfected with recombinant CDR2 and CDR2L to elucidate which is the major antigen of Yo antibodies. We found that Yo antibodies bound endogenous CDR2L, but not endogenous CDR2. However, Yo antibodies can bind the recombinant CDR2 protein used in routine clinical testing for these antibodies. Because Yo antibodies only bind endogenous CDR2L, we conclude that CDR2L is the major antigen of Yo antibodies in PCD. ANN NEUROL 2019;86:316-321.

IFN-γ is a therapeutic target in paraneoplastic cerebellar degeneration.

Paraneoplastic neurological disorders result from an autoimmune response against neural self-antigens that are ectopically expressed in neoplastic cells. In paraneoplastic disorders associated to autoantibodies against intracellular proteins, such as paraneoplastic cerebellar degeneration (PCD), current data point to a major role of cell-mediated immunity. In an animal model, in which a neo-self-antigen was expressed in both Purkinje neurons and implanted breast tumor cells, immune checkpoint blockade led to complete tumor control at the expense of cerebellum infiltration by T cells and Purkinje neuron loss, thereby mimicking PCD. Here, we identify 2 potential therapeutic targets expressed by cerebellum-infiltrating T cells in this model, namely α4 integrin and IFN-γ. Mice with PCD were treated with anti-α4 integrin antibodies or neutralizing anti-IFN-γ antibodies at the onset of neurological signs. Although blocking α4 integrin had little or no impact on disease development, treatment using the anti-IFN-γ antibody led to almost complete protection from PCD. These findings strongly suggest that the production of IFN-γ by cerebellum-invading T cells plays a major role in Purkinje neuron death. Our successful preclinical use of neutralizing anti-IFN-γ antibody for the treatment of PCD offers a potentially new therapeutic opportunity for cancer patients at the onset of paraneoplastic neurological disorders.

Paraneoplastic cerebellar degeneration: Yo antibody alters mitochondrial calcium buffering capacity.

AIM: Neurodegeneration is associated with dysfunction of calcium buffering capacity and thereby sustained cellular and mitochondrial calcium overload. Paraneoplastic cerebellar degeneration (PCD), characterized by progressive Purkinje neurone degeneration following paraneoplastic Yo antibody internalization and binding to cerebellar degeneration-related protein CDR2 and CDR2L, has been linked to intracellular calcium homeostasis imbalance due to calbindin D28k malfunction. Therefore, we hypothesized that Yo antibody internalization affects not only calbindin calcium binding capacity, but also calcium-sensitive mitochondrial-associated signalling, causing mitochondrial calcium overload and thereby Purkinje neurone death. METHODS: Immunohistochemically, we evaluated cerebellar organotypic slice cultures of rat brains after inducing PCD through the application of Yo antibody-positive PCD patient sera or purified antibodies against CDR2 and CDR2L how pharmacologically biased mitochondrial signalling affected PCD pathology. RESULTS: We found that Yo antibody internalization into Purkinje neurons caused depletion of Purkinje neurone calbindin-immunoreactivity, cannabinoid 1 receptor over-activation and alterations in the actions of the mitochondria permeability transition pore (MPTP), voltage-dependent anion channels, reactive oxygen species (ROS) and Na+ /Ca2+ exchangers (NCX). The pathological mechanisms caused by Yo antibody binding to CDR2 or CDR2L differed between the two targets. Yo-CDR2 binding did not alter the mitochondrial calcium retention capacity, cyclophilin D-independent opening of MPTP or activity of NCX. CONCLUSION: These findings suggest that minimizing intracellular calcium overload toxicity either directly with cyclosporin-A or indirectly with cannabidiol or the ROS scavenger butylated hydroxytoluene promotes mitochondrial calcium homeostasis and may therefore be used as future neuroprotective therapy for PCD patients.

Cerebellar cortical degeneration associated with feline leukemia virus infection and cerebellar lymphoma in a young cat.

Background: Cerebellar cortical degeneration (CCD) is the premature death of cerebellar neurons of heterogeneous etiology that is uncommonly observed as a neurological complication of certain neoplasia. Case Description: Here, we report an 8-month-old male domestic cat with altered consciousness, symmetric ataxia, hypermetric gait, vertical positional nystagmus, mydriasis, strabismus, intention tremor of the head, and increased patellar reflexes. Neuroanatomical diagnosis suggested a multifocal brain dysfunction (cerebellar and cerebral). The cat tested seropositive for feline leukemia virus. Cerebrospinal fluid analysis indicated mononuclear and neutrophilic pleocytosis. Contrast computed tomography imaging revealed multiple hypodense heterogeneous areas in both cerebral hemispheres, mild ventriculomegaly at the level of the caudal fossa, and a circular sharply marginated, homogeneously hyperdense mass occupying the right cerebellar hemisphere. Postmortem study indicated a 1.1 × 1.3 × 1.2 cm mass in the right cerebellar hemisphere close to the vermis. Histopathological analysis showed diffuse and severe Purkinje cell loss with a decrease in granular cell density and moderate gliosis compatible with CCD. Further, numerous neoplastic lymphoid cells were observed in the infiltrated mass, consistent with a diagnosis of central nervous system (CNS) lymphoma. Immunohistochemistry showed CD20 expression, indicative of a B-cell immunophenotype. In humans, CCD is reported as a rare paraneoplastic syndrome in patients with Hodgkin lymphoma. CNS lymphoma and/or Feline Leukemia Virus (FeLV) infection were both considered as a possible cause of CCD in this case. Conclusion: This is the first described case of possible paraneoplastic cerebellar cortical degeneration associated with CNS lymphoma and/or FeLV infection in a domestic cat.

Transcriptomic immune profiling of ovarian cancers in paraneoplastic cerebellar degeneration associated with anti-Yo antibodies.

BACKGROUND: Paraneoplastic neurological syndromes are rare conditions where an autoimmune reaction against the nervous system appears in patients suffering from a tumour, but not linked to the spreading of the tumour. A break in the immune tolerance is thought to be the trigger. METHODS: The transcriptomic profile of 12 ovarian tumours (OT) from patients suffering from paraneoplastic cerebellar degeneration (PCD) linked to anti-Yo antibodies (anti-Yo PCD OT) was compared with 733 ovarian tumours (OT control) from different public databases using linear model analysis. RESULTS: A prominent significant transcriptomic over-representation of CD8+ and Treg cells was found in anti-Yo PCD OT, as compared to the OT control. However, the overall degree of immune cell infiltration was similar, according to the ESTIMATE immune score. We also found an under-representation of M2 macrophages in anti-Yo PCD OT. Furthermore, the differentially expressed genes were enriched for AIRE-related genes, a well-known transcription factor associated with a broad range of autoimmune diseases. Finally, we found that the differentially expressed genes were correlated to the transcriptomic profiling of the cerebellar structures. CONCLUSIONS: Our data pinpointed the enrichment of acquired immune response, particularly high density of CD8+ lymphocytes, and high-level expression of CDR-related antigens in anti-Yo PCD OT.

Paraneoplastic cerebellar degeneration associated with cerebellar hypermetabolism: Case report.

RATIONALE: Paraneoplastic cerebellar degeneration (PCD) is an immune-mediated neurological deficit affecting the cerebellum. Anti-Yo antibody positive PCD is a rare occurrence most likely associated with gynecologic or breast malignancies. The identification of the underlying tumor is a diagnostic challenge in many of these patients. PATIENT CONCERNS: We present a 68-year-old woman with acute symptoms of PCD as a first sign of underlying occult malignancy. Further investigation revealed a positive anti-Yo antibody. Although brain magnetic resonance imaging (MRI) was unremarkable, positron emission tomography (PET)/computed tomography (CT) revealed intense hypermetabolism of cerebellum and diffused hypometabolism in the rest of brain. On 1-year follow-up, despite the primary malignancy is still unknown, her symptoms improved significantly after immunotherapy. DIAGNOSES: Paraneoplastic cerebellar degeneration. INTERVENTIONS: The patient was given IV methylprednisolone 500 mg once a day for 5 consecutive days, followed by oral prednisone 60 mg once a day for 3 months. OUTCOMES: The patient's symptoms were gradually improved during the hospitalization period. On one year follow up, she was able to walk independently and perform some simple tasks. LESSONS: Cerebellar hypermetabolism in PCD suspected patients may help confirming the diagnosis in an earlier stage and may predict a better outcome after immunotherapy.

Anti-Yo-Associated Paraneoplastic Cerebellar Degeneration Manifesting as Acute Cerebellitis with Posterior Cranial Fossa Hypertension.

BACKGROUND: Paraneoplastic cerebellar degeneration (PCD) is a rare complication of some malignant cancers. It is most commonly described in women with gynecologic or breast malignancies; however, there have been reports in other types of cancers. Symptoms include ataxia, dysarthria, and tremors, which could be the first manifestations of an underlying malignancy. CASE DESCRIPTION: A 50-year-old woman had an acute PCD with anti-Yo antibodies from an underlying breast invasive ductal carcinoma. She presented with intracranial hypertension in the posterior cranial fossa that required an emergent decompressive craniectomy. CONCLUSIONS: PCD is an uncommon disease that may manifest initially as posterior cranial fossa hypertension and subsequent acute hydrocephalus owing to diffuse cerebellar swelling. To our knowledge, this is the first described case of an anti-Yo PCD that has manifested as acute posterior cranial fossa hypertension owing to diffuse cerebellar edema. Early diagnosis and treatment should be pursued to improve long-term outcomes.

Genetic alterations and tumor immune attack in Yo paraneoplastic cerebellar degeneration.

Paraneoplastic cerebellar degenerations with anti-Yo antibodies (Yo-PCD) are rare syndromes caused by an auto-immune response against neuronal antigens (Ags) expressed by tumor cells. However, the mechanisms responsible for such immune tolerance breakdown are unknown. We characterized 26 ovarian carcinomas associated with Yo-PCD for their tumor immune contexture and genetic status of the 2 onconeural Yo-Ags, CDR2 and CDR2L. Yo-PCD tumors differed from the 116 control tumors by more abundant T and B cells infiltration occasionally organized in tertiary lymphoid structures harboring CDR2L protein deposits. Immune cells are mainly in the vicinity of apoptotic tumor cells, revealing tumor immune attack. Moreover, contrary to un-selected ovarian carcinomas, 65% of our Yo-PCD tumors presented at least one somatic mutation in Yo-Ags, with a predominance of missense mutations. Recurrent gains of the CDR2L gene with tumor protein overexpression were also present in 59% of Yo-PCD patients. Overall, each Yo-PCD ovarian carcinomas carried at least one genetic alteration of Yo-Ags. These data demonstrate an association between massive infiltration of Yo-PCD tumors by activated immune effector cells and recurrent gains and/or mutations in autoantigen-encoding genes, suggesting that genetic alterations in tumor cells trigger immune tolerance breakdown and initiation of the auto-immune disease.

Paraneoplastic cerebellar syndromes associated with antibodies against Purkinje cells.

The paraneoplastic cerebellar syndrome presents as severe neuroimmunological disease associated with malignancies. Antibodies against antigens expressed by tumor cells cross-react with proteins of cerebellar Purkinje cells leading to neuroinflammation and neuronal loss. These antineuronal antibodies are preferentially investigated by serological analyses while examination of the cerebrospinal fluid is only performed infrequently. We retrospectively investigated 12 patients with antineuronal antibodies against Purkinje cells with a special focus on cerebrospinal fluid. Our results confirm a subacute disease with a severe cerebellar syndrome in 10 female patients due to anti-Yo antibodies associated mostly with gynecological malignancies. While standard cerebrospinal fluid parameters infrequently revealed pathological results, all patients presented oligoclonal bands indicating intrathecal IgG synthesis. Analyses of anti-Yo antibodies in cerebrospinal fluid by calculating the antibody specific index revealed intrathecal synthesis of anti-Yo antibodies in these patients. In analogy to anti-Yo syndrome, an intrathecal production of anti-Tr antibodies in one patient who presented with a paraneoplastic cerebellar syndrome was detected. In an additional patient, anti-Purkinje cell antibodies of unknown origin in the cerebrospinal fluid but not in serum were determined suggesting an isolated immune reaction within the central nervous system (CNS) and underlining the importance of investigating the cerebrospinal fluid. In conclusion, patients with a cerebellar syndrome display a distinct immune reaction within the cerebrospinal fluid including intrathecal synthesis of disease-specific antibodies. We emphasize the importance of a thorough immunological work up including investigations of both serum and cerebrospinal fluid.