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.

Atypical Ataxia Presentation in Variant Ataxia Telangiectasia: Iranian Case-Series and Review of the Literature.

Ataxia-telangiectasia (AT) is a rare autosomal recessive neurodegenerative multisystem disorder. A minority of AT patients can present late-onset atypical presentations due to unknown mechanisms. The demographic, clinical, immunological and genetic data were collected by direct interview and examining the Iranian AT patients with late-onset manifestations. We also conducted a systematic literature review for reported atypical AT patients. We identified three Iranian AT patients (3/249, 1.2% of total registry) with later age at ataxia onset and slower neurologic progression despite elevated alpha-fetoprotein levels, history of respiratory infections, and immunological features of the syndrome. Of note, all patients developed autoimmunity in which a decrease of naïve T cells and regulatory T cells were observed. The literature searches also summarized data from 73 variant AT patients with atypical presentation indicating biallelic mild mutations mainly lead to an atypical phenotype with an increased risk of cancer. Variant AT patients present with milder phenotype or atypical form of classical symptoms causing under- or mis- diagnosis. Although missense mutations are more frequent, an atypical presentation can be associated with deleterious mutations due to unknown modifying factors.

Bickerstaff's brainstem encephalitis associated with anti-GM1 and anti-GD1a antibodies.

Bickerstaff's brainstem encephalitis (BBE) is a Guillain-Barré syndrome (GBS) spectrum disorder associated with predominantly central nervous system predilection. Patients exhibit a variable constellation of depressed consciousness, bilateral external ophthalmoplegia, ataxia and long tract signs. Although the pathophysiology is not fully understood, it has been associated with anti-GQ1b antibodies in two-thirds of patients. We present a patient with clinical features consistent with BBE and positive anti-GM1 and anti-GD1a antibodies. A diagnostic approach to the acutely unwell patient with brainstem encephalitis is explored in this clinical context with a literature review of the aforementioned ganglioside antibody significance. Intravenous immunoglobulin therapy is highlighted in BBE using up-to-date evidence-based extrapolation from GBS.

[Ataxia - a group of heterogeneous diseases]. / Ataxier ­ en heterogen grupp och en klinisk utmaning.

Ataxias constitute a group of heterogeneous diseases with overlapping symptoms. The clinical investigation should primarily seek for treatable conditions such as neurometabolic disorders and autoimmune diseases. Rapid progression is often characteristic for paraneoplastic cerebellar degeneration, autoimmune diseases or multiple system atrophy (MSA). The rapid development of massive parallel DNA sequencing and its increased accessibility have enabled for improved diagnostic resolution of patients. A diagnosis based on the etiology is crucial for prognosis and treatment of ataxias. In hereditary forms, the identification of causative genetic factors is essential for family planning.

Clofibrate, a PPAR-α agonist, abrogates sodium fluoride-induced neuroinflammation, oxidative stress, and motor incoordination via modulation of GFAP/Iba-1/anti-calbindin signaling pathways.

Fluoride is an environmental contaminant that is ubiquitously present in air, water, and soil. It is commonly added in minute quantity to drinking water, toothpaste, and mouth rinses to prevent tooth decay. Epidemiological findings have demonstrated that exposure to fluoride induced neurodevelopmental toxicity, developmental neurotoxicity, and motor disorders. The neuroprotective effect of clofibrate, a peroxisome proliferator-activated receptor alpha agonist, was investigated in the present study. Forty male Wistar rats were used for this study and randomly grouped into 10 rats per group as control, sodium fluoride (NaF) alone (300 ppm), NaF plus clofibrate (250 mg/kg), and NaF plus lisinopril (10 mg/kg), respectively, for 7 days. NaF was administered in drinking water while clofibrate and lisinopril were administered by oral gavage. Markers of neuronal inflammation and oxidative stress, acetylcholinesterase activity, and neurobehavioral (hanging wire and open field) tests were performed. Immunohistochemistry was performed on brain tissues, and they were probed with glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1, and cerebellar Ca2+ -binding protein calbindin-D28k. The results showed that NaF significantly increased of oxidative stress and neuroinflammation and inhibited AChE activity. Immunostaining showed reactive astrocytes, microgliosis, loss of dendritic spines, and arborization in Purkinje cells in rats administered only NaF. Neurobehavioral results showed that cotreatment of NaF with clofibrate improved muscular strength and locomotion, reduced anxiety, and significantly reduced astrocytic count. Overall, cotreatment of NaF with either clofibrate or lisinopril showed neuroprotective effects by mitigating neuronal inflammation and oxidative and motor incoordination. Hence, clofibrate could be seen as a novel drug candidate against neurodegeneration and motor disorders.

Myelin uncompaction and axo-glial detachment in chronic ataxic neuropathy with monospecific IgM antibody to ganglioside GD1b.

To describe clinical features, disease course, treatment response, and sural nerve biopsy findings in a patient with chronic sensory ataxic neuropathy, Binet stage A chronic lymphocytic leukemia, and monoclonal IgMλ paraprotein against ganglioside GD1b. During 9 months of hospitalization at two neurologic centers, the patient underwent serial neurologic examinations, neurophysiologic studies, imaging investigations, extensive laboratory work-up, bone marrow, and sural nerve biopsies. The patient had a severe progressive sensory neuropathy accompanied by motor involvement, dysautonomia, and marked bulbar weakness with preserved ocular movements. Conduction studies were characterized by prolonged F-wave minimal latencies, prolonged distal latencies, reduction of compound motor action potentials, and absence of sensory nerve action potentials. Sural nerve biopsy showed endoneurial edema, axonal degeneration, and regeneration, in the absence of cellular inflammation, macrophagic activation, and B-lymphocyte infiltration; no IgM or complement deposition was detected. Myelinated fibers showed redundant/abnormally thickened myelin, myelin vacuolation, and frank intramyelinic edema with condensed axoplasm. Ultrastructural features included axo-glial detachment, disruption of membrane integrity, and myelin uncompaction. This study shows that monospecific anti-GD1b IgM paraprotein is associated with non-inflammatory nerve damage. We suggest that the loss of myelin and axonal integrity reflects antibody-induced disruption of membrane lipid rafts.

Role of Microglia in Ataxias.

Microglia, the resident macrophages of the central nervous system, critically influence neural function during development and in adulthood. Microglia are also profoundly sensitive to insults to the brain to which they respond with process of activation that includes spectrum of changes in morphology, function, and gene expression. Ataxias are a class of neurodegenerative diseases characterized by motor discoordination and predominant cerebellar involvement. In case of inherited forms of ataxia, mutant proteins are expressed throughout the brain and it is unclear why cerebellum is particularly vulnerable. Recent studies demonstrated that cerebellar microglia have a uniquely hyper-vigilant immune phenotype compared to microglia from other brain regions. These findings may indicate that microglia actively contribute to cerebellar vulnerability in ataxias. Here we review current knowledge about cerebellar microglia, their activation, and their role in the pathogenesis of ataxias. In addition, we briefly review advantages and disadvantages of several experimental approaches available to study microglia.

Advances in Therapies of Cerebellar Disorders: Immune-mediated Ataxias.

The identification of an increasing number of immune mediated ataxias suggests that the cerebellum is often a target organ for autoimmune insults. The diagnosis of immune mediated ataxias is challenging as there is significant clinical overlap between immune mediated and other forms of ataxia. Furthermore the classification of immune mediated ataxias requires further clarification particularly for those ataxias where no specific antigenic trigger and associated antibodies have been identified. Recognition of immune mediated ataxias remains imperative as therapeutic interventions can be effective, although given the relative rarity of this entity, large-scale treatment trials may not be feasible. This review will discuss advances in therapies for immune mediated ataxias based on what is currently available in the literature.

Co-occurrence of acute ophthalmoplegia (without ataxia) and idiopathic intracranial hypertension.

BACKGROUND: Acute ophthalmoparesis without ataxia was designated as 'atypical Miller Fisher syndrome' as it presents with progressive, relatively symmetrical ophthalmoplegia, but without ataxia nor limb weakness, in the presence of anti-GQ1b antibody. Idiopathic intracranial hypertension is characterized by signs of raised intracranial pressure occurring in the absence of cerebral pathology, with normal composition of cerebrospinal fluid and a raised opening pressure of more than 20 cmH2O during lumbar puncture. We aim to report a rare case of acute ophthalmoplegia with co-occurrence of raised intracranial pressure. CASE DESCRIPTION: A 28-year-old gentleman with body mass index of 34.3 was referred to us for management of double vision of 2 weeks duration. His symptom started after a brief episode of upper respiratory tract infection. His best corrected visual acuity was 6/6 OU. He had bilateral sixth nerve palsy worse on the left eye and bilateral hypometric saccade. His deep tendon reflexes were found to be hyporeflexic in all four limbs. No sensory or motor power deficit was detected, and his gait was normal. Plantar reflexes were downwards bilaterally and cerebellar examination was normal. Both optic discs developed hyperaemia and swelling. Magnetic resonance imaging of brain was normal and lumbar puncture revealed an opening pressure of 50 cmH2O. Anti-GQ1b IgG and anti-GT1a IgG antibody were tested positive. CONCLUSION: Acute ophthalmoparesis without ataxia can present with co-occurrence of raised intracranial pressure. It is important to have a full fundoscopic assessment to look for papilloedema in patients presenting with Miller Fisher syndrome or acute ophthalmoparesis without ataxia.

Acute microglia ablation induces neurodegeneration in the somatosensory system.

Previous studies have reported that microglia depletion leads to impairment of synapse formation and these cells rapidly repopulate from CNS progenitors. However, the impact of microglia depletion and repopulation in the long-term state of the CNS environment has not been characterized. Here, we report that acute and synchronous microglia depletion and subsequent repopulation induces gray matter microgliosis, neuronal death in the somatosensory cortex and ataxia-like behavior. We find a type 1 interferon inflammatory signature in degenerating somatosensory cortex from microglia-depleted mice. Transcriptomic and mass cytometry analysis of repopulated microglia demonstrates an interferon regulatory factor 7-driven activation state. Minocycline and anti-IFNAR1 antibody treatment attenuate the CNS type 1 interferon-driven inflammation, restore microglia homeostasis and reduce ataxic behavior. Neither microglia depletion nor repopulation impact neuropathology or T-cell responses during experimental autoimmune encephalomyelitis. Together, we found that acute microglia ablation induces a type 1 interferon activation state of gray matter microglia associated with acute neurodegeneration.

The Significance of Low Titre Antigliadin Antibodies in the Diagnosis of Gluten Ataxia.

BACKGROUND: Patients with gluten ataxia (GA) without enteropathy have lower levels of antigliadin antibodies (AGA) compared to patients with coeliac disease (CD). Magnetic Resonance Spectroscopy (NAA/Cr area ratio) of the cerebellum improves in patients with GA following a strict gluten-free diet (GFD). This is associated with clinical improvement. We present our experience of the effect of a GFD in patients with ataxia and low levels of AGA antibodies measured by a commercial assay. METHODS: Consecutive patients with ataxia and serum AGA levels below the positive cut-off for CD but above a re-defined cut-off in the context of GA underwent MR spectroscopy at baseline and after a GFD. RESULTS: Twenty-one consecutive patients with GA were included. Ten were on a strict GFD with elimination of AGA, 5 were on a GFD but continued to have AGA, and 6 patients did not go on a GFD. The NAA/Cr area ratio from the cerebellar vermis increased in all patients on a strict GFD, increased in only 1 out of 5 (20%) patients on a GFD with persisting circulating AGA, and decreased in all patients not on a GFD. CONCLUSION: Patients with ataxia and low titres of AGA benefit from a strict GFD. The results suggest an urgent need to redefine the serological cut-off for circulating AGA in diagnosing GA.

CANOMAD and other chronic ataxic neuropathies with disialosyl antibodies (CANDA).

INTRODUCTION: CANOMAD/CANDA are syndromes characterized by ataxic neuropathy, ophthalmoplegia, monoclonal gammopathy, cold agglutinins and disialosyl antibodies. METHODS: A retrospective review of our neuromuscular autoantibody panel database was performed. Anti-GD1b seropositive patients with ataxia were included. RESULTS: Eleven patients were identified. Median age at onset was 56 years. Median disease duration was 6 years. All patients had gait disorders. Nine had ocular motility abnormalities. Most had a monoclonal protein and all had elevated serum IgM. Electrodiagnostic studies showed a mixed axonal/demyelinating pattern (6), an axonal pattern (4), or a pure demyelinating pattern (1). Ultrasounds showed nerve enlargement patterns consistent with acquired demyelination. A nerve biopsy showed near complete loss of myelinated axons with preservation of smaller axons. Rituximab was the most effective immunotherapy. CONCLUSION: CANOMAD/CANDA are rare and debilitating disorders with characteristic clinical and diagnostic findings. In our cohort, nerve ultrasound showed regional nerve enlargement and rituximab was the most effective immunomodulatory therapy.

Expanding spectrum of contactin-associated protein 2 (CASPR2) autoimmunity-syndrome of parkinsonism and ataxia.

Contactin-associated protein 2 (CASPR2) antibodies are originally associated with Morvan's syndrome and peripheral nerve hyper excitability. Our objective was to study retrospectively the clinical spectrum of CASPR2 antibody-positive patients in our hospital. This is a retrospective observational study. Patients treated at the Amrita Institute of Medical Sciences from May 2013 to April 2016, who were tested positive for CASPR2 antibodies, were included. A total of 1584 samples were tested in the neuroimmunology laboratory during the study period for voltage-gated potassium channel (VGKC) complex antibodies-leucine-rich glioma-inactivated protein 1 (LGI1) and CASPR2 antibodies. Thirty-four were positive for LGI1, 13 were positive for CASPR2, and 7 were for both (total 54-3.4% positivity). Of these 54 cases, 11 were treated in our hospital. Seven were positive for LGI1, three for CASPR2, and one for both. The patient who had both CASPR2 and LGI1 antibody positive had Morvan's syndrome. One patient with CASPR2 had neuromyotonia. The other patient was admitted with status epilepticus with a syndrome of parkinsonism and ataxia. The third patient had encephalopathy and myoclonus with a syndrome of parkinsonism and ataxia. Two of them underwent siddha treatment for other ailments prior to the onset of the disease for other ailments. Our short series shows the expanding spectrum of CASPR2 autoimmunity. Syndrome of parkinsonism and ataxia is an important manifestation of CASPR2 autoimmunity where we can offer a definitive treatment.

Fatal Meningitis in Swine after Intrathecal Administration of Adeno-associated Virus Expressing Syngeneic Interleukin-10.

Interleukin-10 (IL-10) delivered by intrathecal (i.t.) gene vectors is a candidate investigational new drug (IND) for several chronic neurological disorders such as neuropathic pain. We performed a preclinical safety study of IL-10. A syngeneic large animal model was used delivering porcine IL-10 (pIL-10) to the i.t. space in swine by adeno-associated virus serotype 8 (AAV8), a gene vector that was previously found to be nontoxic in the i.t. space. Unexpectedly, animals became ill, developing ataxia, seizures, and an inability to feed and drink, and required euthanasia. Necropsy demonstrated lymphocytic meningitis without evidence of infection in the presence of normal laboratory findings for body fluids and normal histopathology of peripheral organs. Results were replicated in a second animal cohort by a team of independent experimenters. An extensive infectious disease and neuropathology workup consisting of comprehensive testing of tissues and body fluids in a specialized research veterinary pathology environment did not identify a pathogen. These observations raise the concern that i.t. IL-10 therapy may not be benign, that previously used xenogeneic models testing the human homolog of IL-10 may not have been sensitive enough to detect toxicity, and that additional preclinical studies may be needed before clinical testing of IL-10 can be considered.

Effect of gluten-free diet on cerebellar MR spectroscopy in gluten ataxia.

OBJECTIVE: To evaluate the effect of gluten free diet (GFD) on magnetic resonance spectroscopy (MRS) of the cerebellum in patients with gluten ataxia (GA). METHODS: Patients with GA, defined as sporadic ataxia with positive antigliadin antibodies in the absence of an alternative cause, routinely undergo MRS at baseline and after the introduction of GFD as part of their clinical care. We present our experience of the effect of GFD on MRS of the cerebellum. RESULTS: A total of 117 consecutive patients with GA were included in this report. Sixty-three were on strict GFD with elimination of antigliadin antibodies, 35 were on GFD but were still positive for antigliadin antibodies, and 19 patients opted not to go on GFD. The N-acetylaspartate (NAA)/creatine (Cr) area ratio from the cerebellar vermis increased in 62 out of 63 (98%) patients on strict GFD, in 9 of 35 (26%) patients on GFD but positive antibodies, and in only 1 of 19 (5%) patients not on GFD. The NAA/Cr ratio decreased in all 14 ataxia control patients (cerebellar variant of multisystem atrophy). There were no differences in the MRS results between those patients who had and those who did not have enteropathy (celiac disease) within each group. CONCLUSIONS: The demonstration of increased NAA/Cr ratio on repeat scanning following strict GFD strengthens previous findings of clinical improvement of the ataxia in patients with GA. The presence of enteropathy is not a prerequisite for such improvement; therefore patients with positive serology and negative duodenal biopsy should still be treated with strict GFD.

Animal models to study non-celiac gluten sensitivity.

Non-celiac gluten sensitivity (NCGS), sometimes known as non-celiac wheat sensitivity (NCWS), has recently received much attention, both scientific as well as from the alternative medical community. Over the past 5 years, there are over 200 publications on NCGS indexed on the PubMed database, the gluten-free market has been growing bigger, and it is clear that the number of consumers who are on a gluten-free diet (GFD) possibly because of a suspicion for NCGS appears to grow even faster. Nevertheless, despite these three rising events, many questions about NCGS remain unresolved. It is likely that NCGS represents a heterogeneous group of disorders linked by a common response to a GFD. It is still not fully understood how gluten, and likely other wheat proteins and components, could activate and drive the pathophysiology of NCGS. As a result, there are still no clear biomarkers, no robust clinical diagnostic criteria, nor a conclusive definition for NCGS. This heterogeneity can be approached by reducing the variables, in particular those of human behaviour and placebo effect, by studying animal models to address specific biological effects of wheat and/or gluten-related proteins. Herein we review the animal models and their potential to be used to advance our understanding of these disorders and potentially address their prevention and treatment.