Neuronal antibodies in nonparaneoplastic autoimmune cerebellar ataxias

PURPOSE OF REVIEW

To describe relevant advances in nonparaneoplastic autoimmune cerebellar ataxias (ACA) with neuronal antibodies.

RECENT FINDINGS

Apart from metabotropic glutamate receptor 1(mGluR1) antibodies, in recent years, the number of neuronal antibodies against surface antigens in ACA has increased with the description of glutamate kainate receptor subunit 2 (GluK2) antibodies in young patients with cerebellitis. Around 20% of patients with contactin-associated protein-like 2 (CASPR2) encephalitis also present prominent cerebellar ataxia. However, isolate cerebellar ataxia is unusual (<4%). Outcome in patients with neuronal antibodies against surface antigens remains suboptimal despite the cerebellar ataxia probably is antibody-mediated.Concerning neuronal antibodies against intracellular antigens, up to 25% of patients with glutamic acid decarboxylase (GAD) antibodies present transient episodes of vertigo or diplopia that antedate the development of the ACA. There is in-vitro evidence that septin-5 is partially exposed to the membrane and the antibodies may interfere with septin-5 function. The clinical significance of the remaining antibodies against intracellular antigens remains unclear.

SUMMARY

The number of antibodies against surface antigens is increasing in ACA, but the response to the immunotherapy remains suboptimal. More studies are needed to clarify the role of most of the antibodies against intracellular antigens described in these patients.

IgG4 Disease-Related Ataxia

We describe a male patient presenting with cerebellar ataxia and behavioural frontotemporal dementia in whom imaging showed cerebellar atrophy. He had significantly low N-acetyl aspartate to creatine (NAA/Cr) area ratio on MR spectroscopy of the cerebellum, primarily affecting the vermis. CT body scan showed extensive abnormal tissue within the mesentery, the retroperitoneum and perinephric areas. PET-CT showed increased tracer uptake within the wall of the aorta suggestive of an aortitis and within the perinephric tissue bilaterally. Biopsy of the perinephric tissue confirmed IgG4 disease. Treatment with steroids and mycophenolate improved his clinical state, but he developed symptoms attributed to pericardiac effusion that necessitated treatment initially with drainage and subsequently with pericardial window. After a course of rituximab, he had an episode of sepsis that did not respond to appropriate treatment and died as a result. Both the imaging findings and neurological presentation with cerebellar ataxia and behavioural frontotemporal dementia are novel in the context of IgG4 disease.

Immune Ataxias: The Continuum of Latent Ataxia, Primary Ataxia and Clinical Ataxia

The clinical category of immune-mediated cerebellar ataxias (IMCAs) is now recognized after 3 decades of clinical and experimental research. The cerebellum gathers about 60% of neurons in the brain, is enriched in numerous plasticity mechanisms, and presents a large variety of antigens at the neuroglial level: ion channels and related proteins, synaptic adhesion/organizing proteins, transmitter receptors, and glial cells. Cerebellar circuitry is especially vulnerable to immune attacks. After the loss of immune tolerance, IMCAs present in an acute or subacute manner with various combinations of a vestibulocerebellar syndrome (VCS), a cerebellar motor syndrome (CMS), and a cerebellar cognitive affective syndrome/Schmahmann's syndrome (CCAS/SS). IMCAs include gluten ataxia (GA), post-infectious cerebellitis (PIC), Miller Fisher syndrome (MFS), paraneoplastic cerebellar degeneration (PCD), opsoclonus myoclonus syndrome (OMS), anti-glutamic acid decarboxylase (anti-GAD) ataxia, and glial fibrillary acidic protein (GFAP) astrocytopathy (GFAP-A). In addition, multiple sclerosis (MS), acute disseminated encephalomyelitis (ADEM), Behçet disease, and collagen-vascular disorders may also present with cerebellar symptoms when lesions involve cerebellar afferences/efferences. Patients whose clinical profiles do not fit with IMCAs are now gathered in the group of primary autoimmune cerebellar ataxias (PACAs). Latent auto-immune cerebellar ataxia (LACA) refers to a clinical stage with a slow progressive course and a lack of obvious auto-immune background. At a pre-symptomatic stage, patients remain asymptomatic, whereas at the prodromal stage aspecific symptoms occur, announcing the symptomatic neuronal loss. LACA corresponds to a time-window where an intervention could lead to preservation of plasticity mechanisms. Patients may evolve from LACA to PACA and typical IMCAs, highlighting a continuum. Immune ataxias represent a model to elucidate the sequence of events leading to destruction of cerebellar neuronal reserve and develop novel strategies aiming to restore plasticity mechanisms.

Anti-contactin-associated protein-like 2 antibody-associated cerebellar ataxia: A case report and literature review

The spectrum of anti-contactin-associated protein-like 2 (CASPR2) antibody-associated disease is expanding and the involvement of cerebellum was reported in the past few years. We report a 45-year-old male with chronically progressive cerebellar ataxia. CASPR2 antibodies were detected in his serum and cerebellar atrophy was observed on MRI. His symptoms improved prominently with steroids and intravenous immunoglobulins. 23 cases with CASPR2 antibodies and cerebellar ataxia were identified from previous publications. Most of patients showed acute or subacute onset with other typical presentations of anti-CASPR2 antibody-associated disease, such as limbic encephalitis. Immunotherapy was effective in the majority of patients.

Seizure-related 6 homolog like 2 autoimmunity: Neurologic syndrome and antibody effects

OBJECTIVE

To describe the clinical syndrome of 4 new patients with seizure-related 6 homolog like 2 antibodies (SEZ6L2-abs), study the antibody characteristics, and evaluate their effects on neuronal cultures.

METHODS

SEZ6L2-abs were initially identified in serum and CSF of a patient with cerebellar ataxia by immunohistochemistry on rat brain sections and immunoprecipitation from rat cerebellar neurons. We used a cell-based assay (CBA) of HEK293 cells transfected with SEZ6L2 to test the serum of 95 patients with unclassified neuropil antibodies, 331 with different neurologic disorders, and 10 healthy subjects. Additional studies included characterization of immunoglobulin G (IgG) subclasses and the effects of SEZ6L2-abs on cultures of rat hippocampal neurons.

RESULTS

In addition to the index patient, SEZ6L2-abs were identified by CBA in 3/95 patients with unclassified neuropil antibodies but in none of the 341 controls. The median age of the 4 patients was 62 years (range: 54-69 years), and 2 were female. Patients presented with subacute gait ataxia, dysarthria, and mild extrapyramidal symptoms. Initial brain MRI was normal, and CSF pleocytosis was found in only 1 patient. None improved with immunotherapy. SEZ6L2-abs recognized conformational epitopes. IgG4 SEZ6L2-abs were found in all 4 patients, and it was the predominant subclass in 2. SEZ6L2-abs did not alter the number of total or synaptic SEZ6L2 or the AMPA glutamate receptor 1 (GluA1) clusters on the surface of hippocampal neurons.

CONCLUSIONS

SEZ6L2-abs associate with a subacute cerebellar syndrome with frequent extrapyramidal symptoms. The potential pathogenic effect of the antibodies is not mediated by internalization of the antigen.

Antibodies against metabotropic glutamate receptor type 1 in a toddler with acute cerebellitis

Antibodies against metabotropic glutamate receptor type 1 (mGluR1) have been described in adults with paraneoplastic or non-paraneoplastic subacute cerebellitis. Patients responded to immunotherapy depending on disease duration. Here, we report on a 3 years 2 months old male toddler with acute onset ataxia and mGluR1 antibodies in serum and cerebrospinal fluid (CSF). He was started on prednisolone 4 weeks after disease onset and remitted largely within half a year.

Neurological Syndromes Associated with Anti-GAD Antibodies

Glutamic acid decarboxylase (GAD) is an intracellular enzyme whose physiologic function is the decarboxylation of glutamate to gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter within the central nervous system. GAD antibodies (Ab) have been associated with multiple neurological syndromes, including stiff-person syndrome, cerebellar ataxia, and limbic encephalitis, which are all considered to result from reduced GABAergic transmission. The pathogenic role of GAD Ab is still debated, and some evidence suggests that GAD autoimmunity might primarily be cell-mediated. Diagnosis relies on the detection of high titers of GAD Ab in serum and/or in the detection of GAD Ab in the cerebrospinal fluid. Due to the relative rarity of these syndromes, treatment schemes and predictors of response are poorly defined, highlighting the unmet need for multicentric prospective trials in this population. Here, we reviewed the main clinical characteristics of neurological syndromes associated with GAD Ab, focusing on pathophysiologic mechanisms.

Primary DQ effect in the association between HLA and neurological syndromes with anti-GAD65 antibodies

The primary cause of neurological syndromes with antibodies against glutamic acid decarboxylase 65 (GAD65-Ab) is unknown, but genetic predisposition may exist as it is suggested by the co-occurrence in patients and their relatives of other organ-specific autoimmune diseases, notably type 1 diabetes mellitus (T1DM), and by the reports of a few familial cases. We analyzed the human leukocyte antigen (HLA) in 32 unrelated patients and compared them to an ethnically matched sample of 137 healthy controls. Four-digit resolution HLA alleles were imputed from available Genome Wide Association data, and full HLA next-generation sequencing-based typing was also performed. HLA DQA1*05:01-DQB1*02:01-DRB1*03:01 was the most frequent class II haplotype in patients (13/32, 41%). DQB1*02:01 was the only allele found to be significantly more common in patients than in controls (20/137, 15%, corrected p = 0.03, OR 3.96, 95% CI [1.54-10.09]). There was also a trend towards more frequent DQA1*05:01 among patients compared to controls (22/137, 16%; corrected p = 0.05, OR 3.54, 95% CI [1.40-8.91]) and towards a protective effect of DQB1*03:01 (2/32, 6% in patients vs. 42/137, 31% in control group; corrected p = 0.05, OR 0.15, 95% CI [0.02-0.65]). There was no significant demographic or clinical difference between DQ2 and non-DQ2 carriers (p > 0.05). Taken together, these findings suggest a primary DQ effect on GAD65-Ab neurological diseases, partially shared with other systemic organ-specific autoimmune diseases such as T1DM. However, it is likely that other non-HLA loci are involved in the genetic predisposition of GAD65-Ab neurological syndromes.

Immune-mediated Cerebellar Ataxias: Practical Guidelines and Therapeutic Challenges

Immune-mediated cerebellar ataxias (IMCAs), a clinical entity reported for the first time in the 1980s, include gluten ataxia (GA), paraneoplastic cerebellar degenerations (PCDs), antiglutamate decarboxylase 65 (GAD) antibody-associated cerebellar ataxia, post-infectious cerebellitis, and opsoclonus myoclonus syndrome (OMS). These IMCAs share common features with regard to therapeutic approaches. When certain factors trigger immune processes, elimination of the antigen( s) becomes a priority: e.g., gluten-free diet in GA and surgical excision of the primary tumor in PCDs. Furthermore, various immunotherapeutic modalities (e.g., steroids, immunoglobulins, plasmapheresis, immunosuppressants, rituximab) should be considered alone or in combination to prevent the progression of the IMCAs. There is no evidence of significant differences in terms of response and prognosis among the various types of immunotherapies. Treatment introduced at an early stage, when CAs or cerebellar atrophy is mild, is associated with better prognosis. Preservation of the "cerebellar reserve" is necessary for the improvement of CAs and resilience of the cerebellar networks. In this regard, we emphasize the therapeutic principle of "Time is Cerebellum" in IMCAs.

Prevalence of Autoantibodies and the Efficacy of Immunotherapy for Autoimmune Cerebellar Ataxia

OBJECTIVE

Autoimmune cerebellar ataxias were recently reported to be treatable. However, the proportion of patients with cortical cerebellar atrophy of unknown etiology with autoimmune-associated cerebellar ataxia and the actual effectiveness of immunotherapy in these diseases remain unknown.

METHODS

We measured the level of autoantibodies (including anti-gliadin antibody, anti-glutamic acid decarboxylase (GAD) antibody, and anti-thyroid antibody) in 58 Japanese patients with cerebellar ataxia, excluding those with multiple system atrophy, hereditary spinocerebellar ataxia, cancer, or those who were receiving phenytoin, and the efficacy of immunotherapy was assessed.

RESULTS

Thirty-one of 58 (53%) patients were positive for anti-GAD antibody, anti-gliadin antibody, or anti-thyroid antibody. Seven of the 12 anti-gliadin antibody-positive patients, three of the four anti-GAD antibody-positive patients, and three of the six anti-thyroid antibody-positive patients responded well to immunotherapy, indicating that 59% of patients with ataxia-associated antibody-positive cerebellar ataxia undergoing immunotherapy responded well.

CONCLUSION

Some patients with cerebellar ataxia have autoimmune conditions and diagnosing autoimmune cerebellar ataxia is therefore an important component in the care of patients with this disease entity.

Membranous nephropathy and cerebellar degeneration with anti-GAD antibodies in type 2 diabetes mellitus

AIMS

To study the potential pathogenic significance of the coexistence of membranous nephropathy, cerebellar degeneration and anti-glutamic acid decarboxylase (GAD) autoantibodies in patients with diabetes.

METHODS

We performed a direct immunocytochemistry on human kidney slides, electron microscopy on human kidney biopsy, direct immunofluorescence on human kidney biopsy. Baboon and rat kidney cell lines were fractionated and subjected to western blotting with antibodies to GAD.

RESULTS

In this patient we demonstrate the presence of autoantibodies to GAD, which is highly enriched in podocytes plasma membrane and tubular cells of the kidney as well as sub-endothelial IgG and complement C3 deposits in the glomerular basement membrane (GBM).

CONCLUSIONS

We hypothesize the existence in this patient of a common autoimmune pathogenic mechanism with GAD as the autoantigenic determinant, underlying cerebellar degeneration and membranous nephropathy.

'Medusa head ataxia': the expanding spectrum of Purkinje cell antibodies in autoimmune cerebellar ataxia. Part 2: Anti-PKC-gamma, anti-GluR-delta2, anti-Ca/ARHGAP26 and anti-VGCC

Serological testing for anti-neural autoantibodies is important in patients presenting with idiopathic cerebellar ataxia, since these autoantibodies may indicate cancer, determine treatment and predict prognosis. While some of them target nuclear antigens present in all or most CNS neurons (e.g. anti-Hu, anti-Ri), others more specifically target antigens present in the cytoplasm or plasma membrane of Purkinje cells (PC). In this series of articles, we provide a detailed review of the clinical and paraclinical features, oncological, therapeutic and prognostic implications, pathogenetic relevance, and differential laboratory diagnosis of the 12 most common PC autoantibodies (often referred to as 'Medusa head antibodies' due their characteristic somatodendritic binding pattern when tested by immunohistochemistry). To assist immunologists and neurologists in diagnosing these disorders, typical high-resolution immunohistochemical images of all 12 reactivities are presented, diagnostic pitfalls discussed and all currently available assays reviewed. Of note, most of these antibodies target antigens involved in the mGluR1/calcium pathway essential for PC function and survival. Many of the antigens also play a role in spinocerebellar ataxia. Part 1 focuses on anti-metabotropic glutamate receptor 1-, anti-Homer protein homolog 3-, anti-Sj/inositol 1,4,5-trisphosphate receptor- and anti-carbonic anhydrase-related protein VIII-associated autoimmune cerebellar ataxia (ACA); part 2 covers anti-protein kinase C gamma-, anti-glutamate receptor delta-2-, anti-Ca/RhoGTPase-activating protein 26- and anti-voltage-gated calcium channel-associated ACA; and part 3 reviews the current knowledge on anti-Tr/delta notch-like epidermal growth factor-related receptor-, anti-Nb/AP3B2-, anti-Yo/cerebellar degeneration-related protein 2- and Purkinje cell antibody 2-associated ACA, discusses differential diagnostic aspects, and provides a summary and outlook.

'Medusa head ataxia': the expanding spectrum of Purkinje cell antibodies in autoimmune cerebellar ataxia. Part 3: Anti-Yo/CDR2, anti-Nb/AP3B2, PCA-2, anti-Tr/DNER, other antibodies, diagnostic pitfalls, summary and outlook

Serological testing for anti-neural autoantibodies is important in patients presenting with idiopathic cerebellar ataxia, since these autoantibodies may indicate cancer, determine treatment and predict prognosis. While some of them target nuclear antigens present in all or most CNS neurons (e.g. anti-Hu, anti-Ri), others more specifically target antigens present in the cytoplasm or plasma membrane of Purkinje cells (PC). In this series of articles, we provide a detailed review of the clinical and paraclinical features, oncological, therapeutic and prognostic implications, pathogenetic relevance, and differential laboratory diagnosis of the 12 most common PC autoantibodies (often referred to as 'Medusa head antibodies' due to their characteristic somatodendritic binding pattern when tested by immunohistochemistry). To assist immunologists and neurologists in diagnosing these disorders, typical high-resolution immunohistochemical images of all 12 reactivities are presented, diagnostic pitfalls discussed and all currently available assays reviewed. Of note, most of these antibodies target antigens involved in the mGluR1/calcium pathway essential for PC function and survival. Many of the antigens also play a role in spinocerebellar ataxia. Part 1 focuses on anti-metabotropic glutamate receptor 1-, anti-Homer protein homolog 3-, anti-Sj/inositol 1,4,5-trisphosphate receptor- and anti-carbonic anhydrase-related protein VIII-associated autoimmune cerebellar ataxia (ACA); part 2 covers anti-protein kinase C gamma-, anti-glutamate receptor delta-2-, anti-Ca/RhoGTPase-activating protein 26- and anti-voltage-gated calcium channel-associated ACA; and part 3 reviews the current knowledge on anti-Tr/delta notch-like epidermal growth factor-related receptor-, anti-Nb/AP3B2-, anti-Yo/cerebellar degeneration-related protein 2- and Purkinje cell antibody 2-associated ACA, discusses differential diagnostic aspects and provides a summary and outlook.

'Medusa-head ataxia': the expanding spectrum of Purkinje cell antibodies in autoimmune cerebellar ataxia. Part 1: Anti-mGluR1, anti-Homer-3, anti-Sj/ITPR1 and anti-CARP VIII

Serological testing for anti-neural autoantibodies is important in patients presenting with idiopathic cerebellar ataxia, since these autoantibodies may indicate cancer, determine treatment and predict prognosis. While some of them target nuclear antigens present in all or most CNS neurons (e.g. anti-Hu, anti-Ri), others more specifically target antigens present in the cytoplasm or plasma membrane of Purkinje cells (PC). In this series of articles, we provide a detailed review of the clinical and paraclinical features, oncological, therapeutic and prognostic implications, pathogenetic relevance, and differential laboratory diagnosis of the 12 most common PC autoantibodies (often referred to as 'Medusa-head antibodies' due to their characteristic somatodendritic binding pattern when tested by immunohistochemistry). To assist immunologists and neurologists in diagnosing these disorders, typical high-resolution immunohistochemical images of all 12 reactivities are presented, diagnostic pitfalls discussed and all currently available assays reviewed. Of note, most of these antibodies target antigens involved in the mGluR1/calcium pathway essential for PC function and survival. Many of the antigens also play a role in spinocerebellar ataxia. Part 1 focuses on anti-metabotropic glutamate receptor 1-, anti-Homer protein homolog 3-, anti-Sj/inositol 1,4,5-trisphosphate receptor- and anti-carbonic anhydrase-related protein VIII-associated autoimmune cerebellar ataxia (ACA); part 2 covers anti-protein kinase C gamma-, anti-glutamate receptor delta-2-, anti-Ca/RhoGTPase-activating protein 26- and anti-voltage-gated calcium channel-associated ACA; and part 3 reviews the current knowledge on anti-Tr/delta notch-like epidermal growth factor-related receptor-, anti-Nb/AP3B2-, anti-Yo/cerebellar degeneration-related protein 2- and Purkinje cell antibody 2-associated ACA, discusses differential diagnostic aspects and provides a summary and outlook.

Cerebellar ataxia induced by 3-AP affects immunological function

OBJECTIVE

We previously showed that the cerebellum modulates the immune system. Here we determined whether cerebellar ataxia alters immunological function to further demonstrate an involvement of the cerebellum in immune modulation.

METHODS

Neurotoxin 3-acetylpyridine (3-AP) was intraperitoneally injected in rats to induce cerebellar ataxia. Behavior and motor coordination were tested on day 7 following 3-AP injection. Nissl staining and high-performance liquid chromatography (HPLC) were used to determine neuronal loss and neurotransmitter contents, respectively, in all the three cerebellar nuclei, fastigial nucleus (FN), interposed nucleus (IN) and dentate nucleus (DN). T and B lymphocyte differentiation and function were measured by flow cytometry, Western blot and ELISA.

RESULTS

3-AP induced motor discoordination and locomotor reduction. In all the three cerebellar nuclei, FN, IN and DN, there was a neuronal loss and a decrease in contents of glutamate and GABA (but not glycine) after 3-AP injection. Importantly, CD4+ T cells, but not CD8+ T cells, were increased by the 3-AP treatment. Moreover, interferon (IFN)-γ-producing cells and interleukin (IL)-17-producing cells were decreased in cerebellar ataxia rats, but IL-4-producing cells and CD25-expressing cells were increased. Expression of the T helper (Th)1- and Th17-related cytokines, IFN-γ, IL-2, IL-17 and IL-22, was downregulated in CD4+ cells in cerebellar ataxia rats, while expression of the Th2 and regulatory T (Treg)-related cytokines, IL-4, IL-5, IL-10 and transforming growth factor (TGF)-β, was upregulated. Furthermore, B lymphocyte number and anti-bovine serum albumin (BSA) IgM and IgG antibody levels were elevated in cerebellar ataxia.

CONCLUSION

Cerebellar ataxia alters cellular and humoral immunity.

Paraneoplastic cerebellar ataxia associated with anti-Hu antibodies and benign ganglioneuroma

We describe a case of cerebellar ataxia associated with anti-Hu antibodies and benign ganglioneuroma. A 28-year-old woman developed progressive ataxia with hyporeflexia at the age of 19. Brain MRI showed progressive cerebellar atrophy. Neurophysiological studies, screening of immune-mediated ataxias, oncological markers, vitamin E and genetic tests for spinocerebellar ataxia types 1,2,3, Friedreich ataxia and POLG1 were negative. Anti-Hu antibodies were positive in Western blot and indirect immunofluorescence (1:640). Total-body computed tomography revealed a mediastinum mass; the histological diagnosis was maturing ganglioneuroma. Immunohistochemistry showed a mild reaction between the tumor and the patient's serum, and no reaction between the tumor and control serum. After surgery, serum anti-Hu titer decreased, while ataxic symptoms initially worsened and then stabilized. Ganglioneuroma is a benign tumor, usually derived from the maturation of a neuroblastoma. The benign histology and the presence of anti-Hu antibodies could be related to the positive oncological prognosis and to the slow clinical course mimicking a degenerative ataxia.

LADA type diabetes, celiac diasease, cerebellar ataxia and stiff person syndrome. A rare association of autoimmune disorders

Celiac disease--in its typical form--is a chronic immune-mediated enteropathy with typical clinical symptoms that develops against gliadin content of cereal grains, and is often associated with other autoimmune diseases. In cases of atypical manifestation classic symptoms may be absent or mild, and extra-intestinal symptoms or associated syndromes dominate clinical picture. The authors present a longitudinal follow-up of such a case. A 63-years old woman was diagnosed with epilepsy at the age of 19, and with progressive limb ataxia at the age of 36, which was initially thought to be caused by cerebellar atrophy, later probably by stiff person syndrome. At the age 59, her diabetes mellitus manifested with type 2 diabetic phenotype, but based on GAD positivity later was reclassified as type 1 diabetes. Only the last check-up discovered the celiac disease, retrospectively explaining the entire disease course and neurological symptoms. By presenting this case, the authors would like to draw attention to the fact that one should think of the possibility of celiac disease when cerebellar ataxia, progressive neurological symptoms and diabetes are present at the same time. An early diagnosis may help to delay the progression of disease and help better treatment.

Antiphospholipid antibodies and cerebellar ataxia: a clinical analysis and literature review

BACKGROUND

Although it has been established that antiphospholipid antibodies (APAbs) bind to and modulate the signaling of cerebellar neurons in vitro, the clinical correlation between increased APAbs and cerebellar ataxia has rarely been investigated.

METHODS

We reviewed 10 patients presenting with cerebellar ataxia with increased blood APAbs from our database along with 3 APAb-associated cerebellar ataxia patients in the literature.

RESULTS

Of these 10 patients, 4 exhibited a subacute onset of progressive ataxia, and there were no significant structural changes in their brains that appeared to be responsible for the symptoms. Another 6 showed a chronic course of ataxia, and shared similar morphological changes that included symmetrical lesions in bilateral hemispheres, periventricular lucency and central and temporal atrophy of varying severity; the cerebellum was spared. The predominant APAbs for subacute and chronic ataxia were the anti-beta2-glycoprotein I antibody and anticardiolipin antibody, respectively. Cancer was found in 1 patient with subacute ataxia and in 4 with chronic ataxia. The removal of the cancer, the plasmapheresis and immunosuppressive therapy successfully abolished the ataxia and increased APAb levels in all 5 patients.

CONCLUSIONS

The relation between APAbs and nonvascular neurological disorders, such as cerebellar ataxia, should be further studied. APAbs may mediate neurological deficits via different mechanisms such as structural damage or functional neurotoxicity. Clinically, the examination of blood APAb levels is recommended for patients with cerebellar ataxia without a determined cause, and the further survey of systemic cancers in the case of APAb positivity is also recommended. Finally, plasmapheresis is a reasonable and effective treatment for APAb-associated cerebellar ataxia.

[Autoantibodies associated with autoimmune-mediated cerebellar ataxia]

Various autoantibodies are associated with autoimmune-mediated cerebellar ataxia. Anti-Yo, -Zic, -CARPVIII, -Tr, -Ri, -Hu, -Ma, -CRMP-5, -ANNA-3, -PCA-2, -VGCC, and -mGluR antibodies (Abs) are found in paraneoplastic cerebellar ataxia, whereas anti-GAD, -thyroid, and -gliadin Abs are found in non-paraneoplastic cerebellar ataxia. Most of these antibodies are not pathogenic but are diagnostic markers. However, anti-VGCC, anti-mGluR, and anti-GAD Abs have been shown to cause cerebellar ataxia, because administration of these Abs mimics cerebellar ataxia in vivo. Experiments using in vitro preparations show that anti-VGCC Ab depresses excitatory synaptic transmissions, and anti-GAD Ab suppresses inhibitory synaptic transmissions. Anti-mGluR Ab interferes with the induction of synaptic plasticity. These results suggest that pathogenic Abs elicit cerebellar synaptic dysfunction, and thereby cause ataxia in patients.

[A case of acute cerebellar ataxia following infectious mononucleosis accompanied by intrathecal anti-glutamate receptor δ2 antibody]

An 18-year-old woman was admitted because of sore throat and pain in the epigastric region. On admission, she presented with swollen tonsils and hepatosplenomegaly. Blood examinations revealed the presence of atypical lymphocytes, liver damage and anti-VCA IgM and IgG antibodies. These findings led to diagnosis of infectious mononucleosis. After admission, her condition improved, but on hospital day 4, she suddenly developed cerebellar ataxia in the trunk and four limbs. Cranial MRI findings were normal. Cerebrospinal fluid (CSF) collected on hospital day 6 showed normal cell counts and normal concentrations of protein and glucose. EB virus DNA and anti-VCA IgM and IgG antibodies were negative and glutamate receptor δ2 antibody was positive in CSF collected on hospital day 11. We diagnosed acute cerebellar ataxia (ACA) and performed methylprednisolone pulse therapy. After this therapy, her cerebellar ataxia improved over a few days. This is the first reported case of ACA after EB virus infection presenting with glutamate receptor δ2 antibody in CSF. The glutamate receptor δ2 subunit is expressed on cerebellar Purkinje cells. Therefore, the presence of the antibody may be associated with cerebellar dysfunction. In the present case, secondary immune reactions after EB virus infection may have produced the antibody.

Opposing roles for CXCR3 signaling in central nervous system versus ocular inflammation mediated by the astrocyte-targeted production of IL-12

CXCR3 and its ligands are important for the trafficking of activated CD4(+) T(H)1 T cells, CD8(+) T cells, and natural killer cells during inflammation. Recent functional studies demonstrate a more diverse role of CXCR3 in inflammatory diseases of the central nervous system (CNS). We examined the impact of CXCR3 on a less complex interferon-γ-dependent, type 1 cell-mediated immune response in the CNS, induced in mice by the transgenic production of glial fibrillary acidic protein IL-12 (GF-IL12) by astrocytes and retinal Müller cells. GF-IL12 mice develop ataxia because of severe cerebellar inflammation but have little overt ocular disease. Surprisingly, CXCR3-deficient GF-IL12 mice (GF-IL12/CXCR3KO) have drastically reduced ataxia but developed cataracts, severe ocular inflammation, and eye atrophy. Most GF-IL12/CXCR3KO mice had minimal cerebellar inflammation but severe retinal disorganization, loss of photoreceptors, and lens destruction in the eye. The number of CD3(+), CD11b(+), and natural killer 1.1(+) cells were reduced in the CNS but highly increased in the eyes of GF-IL12/CXCR3KO compared with GF-IL12 mice. High levels of interferon-γ, IL-1, tumor necrosis factor α, CXCL9, CXCL10, and CCL5 were found in GF-IL12 cerebelli and GF-IL12/CXCR3KO eyes. Our findings demonstrate key but paradoxical functions for CXCR3 in IL-12-induced immune disease in the CNS, promoting inflammation in the brain yet restricting it in the eye. We conclude that the function of CXCR3 in cellular immune disease is driven by a common trigger and is controlled by tissue-specific factors.

[A case of persistent cerebellar ataxia complicated by conversion disorder--confirmed by positive cerebrospinal fluid glutamate receptor delta2 and epsilon2 antibodies]

We recently encountered a 13-year-old girl who developed persistent cerebellar symptoms one month after mixed measles/rubella vaccination, making it difficult to distinguish this condition from conversion disorders. Severe truncal ataxia was the initial manifestation in this case. The patient had no abnormalities in objective tests but began to show extraordinary circadian variations in certain parameters. Her cerebellar symptoms were thus considered to possibly be associated with conversion disorders. Later, she tested positive for cerebrospinal fluid anti-glutamic acid receptor (GluR) delta2 antibody. The lymphocyte stimulation test yielded a positive reaction to GluRdelta2 antigen. In addition, in the chronic stage SPECT revealed reduced cerebellar blood flow. She was thus diagnosed as having persistent cerebellar ataxia due to autoimmune mechanisms and modification of cerebellar symptoms due to secondary conversion disorders. Our experience with this case suggests that checking cerebrospinal fluid for anti-GluRdelta2 antibody is possibly useful for distinguishing between conversion disorders and cerebellar ataxia due to autoimmune mechanisms.

Gluten sensitivity: associated sporadic cerebellar ataxia in Taiwan

PURPOSE

Gluten sensitivity (GS) is related to the pathogenesis of sporadic or hereditary ataxia.

METHODS

Total of 194 healthy controls and patients with either hereditary ataxia (n=207) or sporadic ataxia (n=361) were tested for the circulating gluten-related autoantibodies which serve as biomarkers to interpret the existence of GS.

RESULTS

The incidences of GS in each population were 1% in normal subjects, 2% in hereditary ataxia patients and 9% in sporadic ataxia patients. High serum level of anti-gliadin IgG/IgA and t-transglutaminase IgA were disclosed at the sporadic ataxia patients compared with normal subjects. However, the anti-gliadin IgG is more specific to the disease of sporadic ataxia.

CONCLUSION

Relatively higher incidence of GS was found in the population of sporadic ataxia patients but not in either normal subjects or hereditary ataxia patients in Taiwan. Anti-gliadin IgG still is a very powerful indicator to implicate the immune-related sporadic ataxia and we conclude that GS-related sporadic ataxia exists in Taiwan with linkage to autoimmune events.

[A case of recurrent paraneoplastic cerebellar ataxia with antibodies to GluR epsilon 2 causally related to ganglioneuroma]

Acute cerebellar ataxia (ACA) in childhood following viral infection is a self-limited disease. We present a boy with recurrent episodes of paraneoplastic cerebellar ataxia associated with a ganglioneuroma. A 20-month-old boy developed the first episode of cerebellar ataxia after nonspecific respiratory tract infections. During this episode he showed a wide gait and truncal ataxia with intention tremor and horizontal nystagmus. Our initial diagnosis was ACA, and gradual improvement of ataxia was observed thereafter. At 2 years and 6 months, similar cerebellar symptoms recurred after respiratory tract infections. Speech difficulty and cognitive problems developed thereafter. We suspected paraneoplastic syndrome. Computed tomography revealed a retroperitoneal tumor, and autoantibodies against GluR epsilon 2 were detected in the cerebrospinal fluid. After the tumor resection, the cerebellar symptoms did not recur and speech difficulty and cognitive problems improved gradually. Recent neuroimaging and neuropsychological studies have revealed that cerebellar function contributes to higher brain functions including cognition and learning. We will follow up this patient's long-term cognitive function and consider special educational support and programs.

Recurrent and reversible cerebellar ataxia with concomitant episodes of hyperthyroidism: a new autoimmune syndrome

A new disorder with possible autoimmune background is described in a 67-year-old man. He had experienced episodes of cerebellar ataxia induced by infections over the last 40 years. In 1963 he had thyrotoxicosis. The patient underwent bilateral subtotal thyroidectomy. Recently it has been possible to detect involvement also of his remaining thyroid gland, with findings compatible with hyperthyroidism concomitant with his cerebellar atixia.

Intravenous immunoglobulin therapy for autoantibody-positive cerebellar ataxia

OBJECTIVE

It has been reported that autoimmune cerebellar ataxias, such as anti-glutamic acid decarboxylase (GAD)-antibody-positive cerebellar ataxia and gluten ataxia, are treatable. Here, we examined the therapeutic efficacy of intravenous immunoglobulin (IVIg) on autoantibody-positive cerebellar ataxia.

PATIENTS AND METHODS

IVIg therapy was administered in seven autoantibody-positive cerebellar ataxia patients. Therapeutic efficacy was examined in terms of its effects on clinical symptoms and changes in brain perfusion using single photon emission computed tomography (SPECT).

RESULTS

Treatment was effective in four cerebellar cortical atrophy patients (two anti-GAD antibody-positive and two anti-gliadin antibody-positive) and in one anti-thyroid antibody-positive spinocerebellar ataxia type 3 (SCA3) patient, but not in two multiple system atrophy (MSA) patients. All four IVIg effective patients who underwent SPECT showed apparent increases in cerebellar perfusion.

CONCLUSION

If cerebellar ataxia with an autoimmune mechanism is suspected and radiological findings do not reveal MSA, it is worth considering immunotherapy including IVIg.

Reversibility of cerebellar GABAergic synapse impairment induced by anti-glutamic acid decarboxylase autoantibodies

Anti-glutamic acid decarboxylase autoantibodies (GAD-Abs) are found in some patients with cerebellar ataxia. We reported previously that CSF IgGs depress cerebellar GABAergic synaptic transmissions by a presynaptic mechanism. Using whole-cell recordings from rat cerebellar slices, we found in the present study that CSF IgG-induced depressive effects were abolished by absorption of GAD-Abs using recombinant GAD. Furthermore, forskolin, an activator of cAMP, recovered the CSF IgG-induced reduction of GABA release. Our results provide evidence that GAD-Abs in the CSF elicited physiopathological effects on cerebellar GABA synapses in vitro and that such synaptic impairment was reversible.

[Steroid treatment in four cases of anti-GAD cerebellar ataxia]

INTRODUCTION

Few neurological diseases are linked with anti-glutamic acid decarboxylase antibodies (GAD-ab); stiff man syndrome is an example. Cerebellar ataxia is a new feature of this expanding spectrum. No therapeutic trial is yet available in these diseases. We here report on four patients suffering from cerebellar ataxia linked with GAD-ab and review the data in the literature on this recently described syndrome.

METHOD

We conducted an open trial with monthly pulsed steroids. Steroid pulses were given six months followed with placebo for another six months. Main clinical and biological parameters were monitored monthly (International Cooperative Cerebellar Ataxia Rating Scale [ICARS] and GAD-ab).

RESULT

The clinical response was found limited and inconstant. Transient decline in GAD-ab level was noted in two patients. Moreover, GAD-ab level was found highly variable and did not correlate with clinical parameters.

DISCUSSION

Cerebellar ataxia with GAD-ab is an increasingly described syndrome. Outcome can be severe, leading to definitive cerebellar atrophy. Diagnosis is supported by high level of serum GAD-ab with intrathecal secretion. Experimental data have suggested a direct excitotoxic effect of GAD-ab on Purkinje cells. Response to various treatments is often disappointing. Improvement has been obtained with veinoglobulins in individual patients. A weak clinical and biological response was associated with monthly steroid pulses.

Acute cerebellar ataxia and consecutive cerebellitis produced by glutamate receptor delta2 autoantibody

Acute cerebellar ataxia is usually a self-limited benign disease, which may develop in children after certain viral infections or vaccinations. There are several reports of acute cerebellar ataxia associated with autoantibodies. Glutamate receptor delta2, a member of the glutamate receptor family, is predominantly expressed in cerebellar Purkinje cells and plays a crucial role in cerebellar functions. To date anti-GluRdelta2 autoantibody was detected in a patient with chronic cerebellitis. Herein, an 18-month-old boy presented with cerebellar ataxia 9 days following a mild respiratory tract infection. Although cerebellar ataxia gradually improved, it worsened yet again following mumps and varicella virus infection. Cerebro-spinal fluid examination and magnetic resonance imaging of the brain demonstrated pleocytosis and meningeal enhancement, respectively. Furthermore, glutamate receptor delta2 autoantibody was detected in serum and cerebro-spinal fluid. Thus, we believe that the glutamate receptor delta2 autoantibody may play a role in cerebellar ataxia and consecutive cerebellitis.

Post-malaria neurological syndrome: clinical and laboratory findings in one patient

Post-malaria neurological syndrome (PMNS) is a rare complication of malaria. It follows recovery from an episode of Plasmodium falciparum malaria and is characterised by symptoms and signs of encephalopathy. Patients usually improve without any specific treatment. The pathogenesis is unknown, but it is probably immunologically mediated. The objective of this case study is to describe the first Italian patient with PMNS. A 60-year-old Italian man developed acute P. falciparum malaria after a stay in French Guinea. Twenty days after recovering from malaria, he became confused, developed generalised weakness, limb tremors, shivering and dizziness. These symptoms continued for three days, then resolved spontaneously. Neuroimaging was normal. Cerebrospinal fluid analysis revealed breakdown of the blood/brain barrier, without oligoclonal bands and normal IgG index. Our patient presented a mild diffuse encephalopathy suggestive of a generic activation of the immune system without any specific reaction against antigens within the CNS.

Epilepsy and cerebellar ataxia associated with anti-glutamic acid decarboxylase antibodies

Anti-glutamic acid decarboxylase (GAD) antibodies are described in stiff-person syndrome and also in other neurological syndromes, including cerebellar ataxia and epilepsy. This paper reports the case of a patient who had chronic focal epilepsy, upbeat nystagmus and cerebellar ataxia, associated with a polyautoimmune response including anti-GAD antibodies. Both gait and nystagmus improved markedly after immunosuppressive treatment with corticosteroids and azathioprine. After the introduction of benzodiazepines, previously refractory seizures were completely controlled. Anti-GAD antibodies should be actively sought out in pharmacoresistant epilepsy, particularly if other neurological abnormalities are present. Combined treatment with immunosuppressants and gammahydroxybutyric acidergic agents may be highly effective.

Selective loss of Purkinje cells in a patient with anti-glutamic acid decarboxylase antibody-associated cerebellar ataxia

Anti-glutamic acid decarboxylase antibody is associated with the development of progressive cerebellar ataxia and slowly progressive insulin-dependent diabetes mellitus. Previously, the neurophysiological characteristics of IgG in the cerebrospinal fluid of a patient with anti-glutamic acid decarboxylase antibody-associated progressive cerebellar ataxia and slowly progressive insulin-dependent diabetes mellitus were reported. Using a voltage-gated whole-cell recording technique, it was observed that the IgG in the cerebrospinal fluid of the patient selectively suppressed the inhibitory postsynaptic currents in the Purkinje cells. The patient died from aspiration pneumonia. Postmortem examination showed almost complete depletion of the Purkinje cells with Bergmann gliosis. Therefore, the main cause of cerebellar ataxia observed in this case may be attributed to the near-complete depletion of the Purkinje cells. In this paper, the pathomechanisms underlying Purkinje cell damage are discussed.

Un nouveau cas d'ataxie cérébelleuse à anticorps anti-GAD traité par corticoïdes et initialement séronégatif

INTRODUCTION

Cerebellar ataxia with antiglutamic acid decarboxylase antibodies (GAD-ab) is an exceptional newly recognized autoimmune disorder. The cerebellar ataxia may occur in isolation or be associated with stiff man syndrome another rare GAD-Ab induced disorder of central nervous system.

EXEGESIS

A 38-year-old woman with a past history of Graves disease presented with insidious cerebellar symptoms including ataxic gait, dysmetria, dysarthria, and oscillopsia. A thorough survey of markers of paraneoplastic cerebellar ataxia and collagen diseases was negative. Her serum contained high level of GAD-ab (647.2 U/ml) and MRI evidenced pure cerebellar atrophy leading to diagnosis of autoimmune cerebellar ataxia. Under corticosteroids, cerebellar symptoms partially improved, but serum GAD-ab titre dramatically decreased.

CONCLUSION

Testing for GAD-ab may be indicated in patients with idiopathic cerebellar ataxia, particularly mature women with organ-specific autoimmune diseases. Corticosteroids must be started to prevent irreversible cerebellar atrophy.

Paraneoplastic rhombencephalitis and brachial plexopathy in two cases of amphiphysin auto-immunity

Amphiphysin, a synaptic vesicle protein, is an auto-immune target in rare cases of paraneoplastic neurological disorders. We report two additional cases with distinct neurological syndromes and paraneoplastic anti-amphiphysin antibodies. The first patient, a 59-year-old man, presented with cerebellar and cranial nerve dysfunction and small cell lung carcinoma. The second, a 77-year- old woman, presented with left brachial plexopathy followed by sensorimotor neuropathy and breast carcinoma.

Autoantibodies in postinfectious acute cerebellar ataxia

The authors found serum immunoglobulin M (IgM) autoantibody in a patient with typical acute cerebellar ataxia (ACA) and identified the antigen molecule as triosephosphate isomerase (TPI). TPI antigenicity to the patient's antibody was the highest in the cerebellar tissue. Eight of 23 patients with ACA had increased IgM anti-TPI antibody titers vs those of healthy controls. Preceding Epstein-Barr virus infection was confirmed serologically in all 8 patients. Anti-TPI antibody decreased with clinical improvement.

Ataxie avec sensibilité au gluten, mythe ou réalité ?

INTRODUCTION

Gluten ataxia refers to the association of idiopathic ataxia despite exhaustive investigations with gluten sensitivity defined by anti-gliadin antibodies (AGA) presence in blood. This is a controversial concept.

PATIENTS AND METHODS

We screened 33 patients, who were hospitalized in 2003 and had subacute or chronic ataxia for presence of circulating AGA. Twelve patients were positive and their clinical and biological features were studied.

RESULTS

Among the twelve patients, we concluded that gluten ataxia was present in only eight, including one case of celiac disease. Among these eight patients, five had the usual features of gluten ataxia (progressive cerebellar ataxia affecting mainly lower limbs), but one patient presented unusual left cerebellar hemisyndrome and the two others displayed polyneuropathy with proprioceptive ataxia. Cerebellar atrophy was confirmed with magnetic resonance imaging in five cases and association with other antibodies was found in six cases. Among the four other patients positive for AGA, investigations revealed one case of multiple sclerosis, one case of late-onset Friedreich ataxia, one case of basilar tuberculous meningitis and one case of type 2 diabetes.

CONCLUSION

Screening for AGA presence should be systematically performed at presentation of patients with unknown etiology ataxia; in the event AGA are present without any other etiology, treatment with gluten-free diet must be discussed. However, the responsibility of AGA in the pathogenesis of neurological signs is highly debatable and further experimental work is required. Two pathophysiological hypotheses are suggested: (1) overexpression of cerebellar epitopes, in case of primary cerebellar pathology, leading to excessive immune response directed against these epitopes; and (2) molecular mimicry with cross-reactivity of antigens usually directed against gliadin, but also recognizing Purkinje cells epitopes.

Gluten sensitivity in Japanese patients with adult-onset cerebellar ataxia

OBJECTIVE

Gluten sensitivity is associated with multiple neurological abnormalities including gluten ataxia, motor neuron disease-like neuropathy, small fiber type neuropathy, cognitive impairment, and even parkinsonism. We investigated whether or not gluten sensitivity is involved in Japanese patients with idiopathic cerebellar ataxia with extracerebellar presentation.

PATIENTS OR MATERIALS

Fourteen patients with idiopathic cerebellar ataxia with extracerebellar presentation (autonomic instability, parkinsonism, or pyramidal dysfunction in varying combinations) were screened for anti-gliadin antibodies (AGA) to analyze for the presence or absence of gluten sensitivity. Patients with typical MR findings of multiple system atrophy of the cerebellar type were excluded. As disease controls without cerebellar ataxia, 9 patients with Parkinson's disease and 18 patients with amyotrophic lateral sclerosis were screened for AGA. Forty-seven normal controls were also screened for AGA.

RESULTS

We found a high prevalence of AGA in 5 (36%) of 14 cerebellar ataxia patients, but in only 1 (4%) of 27 disease controls without cerebellar ataxia (odds ratio, 14.4; 95% CI, 1.41147; p<0.05) and in only 1 (2%) of 47 normal controls (odds ratio, 25.6; 95% CI, 2.66246; p<0.001). Among the cerebellar ataxia patients, atypical features such as sensorimotor neuropathy and/or mild cognitive impairment were more prevalent in the AGA-positive group (60%) than in the AGA-negative group (0%). In one of the ataxic patients with AGA, a gluten-free diet had positive effects on neurological symptoms and nutritional status.

CONCLUSION

Gluten sensitivity is involved in at least some of the unexplained neurological symptoms of Japanese patients with adult-onset, sporadic cerebellar ataxia.

Cerebellar ataxia, peripheral neuropathy, "gluten sensitivity" and anti-neuronal autoantibodies

"Gluten sensitive" neurological syndromes (ataxia, peripheral neuropathy, and other conditions) have been hypothesised in patients with various idiopathic neuropathologies, detectable anti-gliadin antibodies and HLA-DQ2 or DQ7. Further investigation of these cases has suggested a high incidence of anti-neuronal antibodies (anti-Purkinje, anti- neuronal nuclear, anti-GAD). This study investigates this contentious area. Over a two-year period, from a local UK population base of two million, seeing over 5000 general neurology referrals per year, we collected 20 cases with idiopathic ataxia, and 32 with idiopathic peripheral neuropathy, and referred them all for blinded antibody testing. 30 adult healthy blood donors, and 7 cases of hereditary ataxia were used as control subjects. Anti-gliadin antibodies (IgG and or IgA) were found in 40% of cases with idiopathic ataxia, 34% with idiopathic peripheral neuropathy, 17% healthy blood donors and 43% with hereditary ataxia. None was positive for antiPurkinje cell or anti-neuronal nuclear antibodies. Only two patients with idiopathic ataxia were positive for antiGAD antibodies (one also being anti-gliadin positive). We were unable to confirm the findings of other groups. First, cases of so-called "gluten sensitive" neurological syndromes were extremely rare in our centre. Second, our idiopathic cases, whether they be gliadin antibody seropositive or not (i.e. "gluten sensitive" or not) were rarely neuronal autoantibody positive.

Cerebellar ataxia and acute motor axonal neuropathy associated with Anti GD1b and Anti GM1 antibodies

The anti-GD1b antibody is known to bind to the cerebellar granular layer or spinocerebellar Ia fibers. A few cases of anti-GD1b positive acute inflammatory demyelinating polyneuropathy with prominent cerebellar ataxia were reported. Recently, we encountered a middle-aged woman with Guillain Barré syndrome (GBS) with severe cerebellar ataxia and relatively mild motor weakness. Anti-GD1b Ig G antibody and anti-GM1 Ig G antibody titers were markedly elevated in her serum. She was diagnosed with acute motor axonal neuropathy (AMAN) with prominent cerebellar ataxia based on the results of the serial nerve conduction study suggesting axonal neuropathy. This case presents the clinico-pathogenic role of autoantibodies to the GD1b and the GM1 in acute inflammatory neuropathy.

Antibodies to cerebellar nerve fibres in two patients with paraneoplastic cerebellar ataxia

The aim of this study was to characterize two new atypical anti-neuronal antibodies using an immunohistochemical method on rat cerebellum and Western blot techniques with primate cerebellar tissue and with recombinant neuronal proteins. Atypical sera from two patients with paraneoplastic neurological syndromes associated with different tumours were detected. Case number 1 presented cerebellar degeneration and Merkel cell carcinoma and case number 2 paraneoplastic brainstem encephalitis and malignant fibrous histiocytoma. By immunohistochemistry, the two new atypical antibodies showed a similar fibrillar positivity in the molecular and granular layers and around the Purkinje cells. The dot blot with recombinant neuronal proteins (HuD, NOVA-1, CDR62/Yo, Amphiphysin) was negative, whereas the Western blot with neuronal antigens of primate cerebellum identified two different proteins with molecular weights (64 kD in case number 1, and 70 kD in case number 2). In conclusion, the two new antibody reactivities against nerve fibres should be integrated into the diagnostic paraneoplastic neurological syndromes guidelines.

Anti-GAD Antibodies and Periodic Alternating Nystagmus

BACKGROUND

Autoantibodies directed against glutamic acid decarboxylase (GAD-Ab) have recently been described in a few patients with progressive cerebellar ataxia, suggesting an autoimmune physiopathologic mechanism.

OBJECTIVE

To determine the exact role of GAD-Ab and gamma-aminobutyric acid (GABA)-ergic neurotransmission in the pathogenesis of cerebellar ataxia.

DESIGN

Case report.

SETTING

University neurological hospital.

PATIENT

We report the case of a patient with subacute cerebellar ataxia associated with GAD-Ab showing periodic alternating nystagmus (PAN).

INTERVENTION

Baclofen, a GABAergic medication, was given to the patient.

MAIN OUTCOME MEASURES

Eye movement recording of spontaneous nystagmus and postrotatory vestibular responses.

RESULTS

Baclofen was effective in suppressing PAN and improving postrotatory vestibular responses but not for improving cerebellar ataxia.

CONCLUSION

The presence of PAN and the response to baclofen provide a unique opportunity to suggest a direct role of GAD-Ab in cerebellar dysfunction in this patient.