Opsoclonus-myoclonus-ataxia syndrome with autoantibodies to glutamic acid decarboxylase

Stiff-Leg Syndrome Associated with Autoimmune Retinopathy and Its Treatment with IVIg-A Case Report and Review of the Literature

Antibodies to glutamic acid decarboxylase (GAD) have been predominantly associated with stiff-person syndrome (SPS), which is often accompanied by organ-specific autoimmune diseases, such as late-onset type 1 diabetes. Autoimmune retinal pathology in SPS has recently been suggested to coexist in patients suffering from this disease; however, evidence reporting potential treatment options for the neurological and visual symptoms these patients experience remains scarce. We provide a review of the relevant literature, presenting a rare case of a middle-aged woman with autoimmune retinopathy (AIR) followed by stiff-leg syndrome who responded to intravenous immune globulin treatment (IVIg). Our report adds to previously reported data supporting the efficacy of IVIg in SPS spectrum disorders while also proposing the potential effect of IVIg in treating SPS spectrum patients with coexisting AIR.

A Rare Case of Opsoclonus Myoclonus Ataxia Syndrome Post Viral Illness

Opsoclonus myoclonus ataxia syndrome (OMAS) is a rare inflammatory neurological disorder characterized by ocular, motor, behavioral, language, and sleep disturbances. It usually affects infants and young children but may affect adults. A 28-year-old male was brought to our emergency ward with complaints of involuntary spontaneous eye movements and jerky movements of limbs with imbalance while walking. He had a history of short febrile illness 10 days prior. His magnetic resonance imaging (MRI) of the brain, cerebrospinal fluid (CSF) analysis, and other routine investigations were normal. The patient was treated with injectable methylprednisolone (1 g) given for five days along with other supportive therapy. A significant reduction in the opsoclonus, myoclonus, and ataxia was seen on a six-month follow-up. OMAS should be identified early to avoid the use of inappropriate medications, and immunotherapy must be provided as early as possible in order to prevent irreversible neurological damage.

Stiff-person Syndrome and GAD Antibody-spectrum Disorders: GABAergic Neuronal Excitability, Immunopathogenesis and Update on Antibody Therapies

Although antibodies against Glutamic Acid Decarboxylase (GAD) were originally associated with Stiff Person Syndrome (SPS), they now denote the "GAD antibody-spectrum disorders (GAD-SD)" that include Cerebellar Ataxia, Autoimmune Epilepsy, Limbic Encephalitis, PERM and eye movement disorder. In spite of the unique clinical phenotype that each of these disorders has, there is significant overlapping symptomatology characterized by autoimmune neuronal excitability. In addition to GAD, three other autoantibodies, against glycine receptors, amphiphysin and gephyrin, are less frequently or rarely associated with SPS-SD. Very high serum anti-GAD antibody titers are a key diagnostic feature for all GAD-SD, commonly associated with the presence of GAD antibodies in the CSF, a reduced CSF GABA level and increased anti-GAD-specific IgG intrathecal synthesis denoting stimulation of B-cell clones in the CNS. Because anti-GAD antibodies from the various hyperexcitability syndromes recognize the same dominant GAD epitope, the clinical heterogeneity among GAD-SD patients remains unexplained. The paper highlights the biologic basis of autoimmune hyperexcitability connected with the phenomenon of reciprocal inhibition as the fundamental mechanism of the patients' muscle stiffness and spasms; addresses the importance of high-GAD antibody titers in diagnosis, pinpointing the diagnostic challenges in patients with low-GAD titers or their distinction from functional disorders; and discusses whether high GAD-antibodies are disease markers or pathogenic in the context of their association with reduced GABA level in the brain and CSF. Finally, it focuses on therapies providing details on symptomatic GABA-enhancing drugs and the currently available immunotherapies in a step-by-step approach. The prospects of future immunotherapeutic options with antibody therapies are also summarized.

Gaze-holding and anti-GAD antibody: prototypic heterogeneous motor dysfunction in immune disease

The variability in motor dysfunction is not uncommon in autoimmune disorders. Antibody-mediated system-wide malfunction or effects on the neural network shared by two independent pathophysiological processes can cause such heterogeneity. We tested this prediction for motor dysfunction during gaze holding in 11 patients with increased titers of glutamic acid decarboxylase (anti-GAD) antibody. High-resolution oculography measured horizontal and vertical eye positions. The analysis was performed with customized signal processing algorithms. Downbeat and gaze-evoked nystagmus commonly coexisted; one patient had a combination of upbeat and gaze-evoked nystagmus. The nystagmus was associated with saccadic intrusions in 10 patients; all had squarewaves, but five also had saccadic oscillations. The nystagmus and saccadic intrusions, both in the same axis of eye rotations, were not uncommon. Tandem appearance of the episodes of nystagmus and saccadic intrusions suggested a coupling between the two abnormalities. We speculated a unifying framework where the anti-GAD antibody inhibited (GAD mediated) conversion of glutamate to gamma-aminobutyric acid (GABA). Paucity GABA and excess of glutamate cause nystagmus (less GABA) and high-frequency saccadic oscillations (excessive glutamate).

Enoxaparin-induced Wunderlich syndrome in a young patient with anti-GAD 65-associated opsoclonus and limbic encephalitis: a rare complication in a rare disease

Wunderlich syndrome is a rare condition characterised by acute spontaneous non-traumatic renal haemorrhage into the subcapsular and perirenal spaces. Our case of anti-GAD65-associated autoimmune encephalitis (AE), aged 30 years, developed this complication following use of enoxaparin and was managed by selective glue embolisation of subsegmental branches of right renal cortical arteries. Our case had opsoclonus as one of the clinical manifestations, which has till now been described in only two patients of this AE. This patient received all forms of induction therapies (steroids, plasmapheresis, intravenous immunoglobulin and rituximab) following which she had good improvement in her clinical condition. The good response to immunotherapy is also a point of discussion as this has been rarely associated with anti-GAD65 AE.

Stiff-Eye Syndrome-Anti-GAD Ataxia Presenting with Isolated Ophthalmoplegia: A Case Report

Anti-GAD ataxia is one of the most common forms of immune-mediated cerebellar ataxias. Many neurological syndromes have been reported in association with anti-GAD. Ophthalmoparesis has been described in stiff person syndrome. We report a case of anti-GAD ataxia presenting initially with isolated ophthalmoplegia and showing complete resolution after immunotherapy. A 26-year-old male patient presented with ophthalmoparesis characterized by tonic upwards deviation of the right eye. In the following month, he developed progressive ataxia with anti-GAD titers of 1972 UI/mL. After treatment with methylprednisolone and immunoglobulin, there was complete resolution of symptoms and anti-GAD titers decreased. This is the first report of isolated ophthalmoparesis due to tonic eye deviation associated with anti-GAD antibodies without stiff-person syndrome. Tonic eye deviation has been reported in SPS, possibly secondary to continuous discharge in gaze holding neurons in the brainstem (similar to what occurs in spinal motor neurons). With growing evidence for ocular abnormalitites in SPS, anti-GAD associated neurological syndromes should be included in the differential diagnosis of isolated ophthalmoplegia.

Acute Movement Disorders in Childhood

Acute-onset movement disorders (MDs) are an increasingly recognized neurological emergency in both adults and children. The spectrum of possible causes is wide, and diagnostic work-up is challenging. In their acute presentation, MDs may represent the prominent symptom or an important diagnostic clue in a broader constellation of neurological and extraneurological signs. The diagnostic approach relies on the definition of the overall clinical syndrome and on the recognition of the prominent MD phenomenology. The recognition of the underlying disorder is crucial since many causes are treatable. In this review, we summarize common and uncommon causes of acute-onset movement disorders, focusing on clinical presentation and appropriate diagnostic investigations. Both acquired (immune-mediated, infectious, vascular, toxic, metabolic) and genetic disorders causing acute MDs are reviewed, in order to provide a useful clinician’s guide to this expanding field of pediatric neurology.

GAD antibody-spectrum disorders: progress in clinical phenotypes, immunopathogenesis and therapeutic interventions

Antibodies against glutamic acid decarboxylase (GAD), originally linked to stiff person syndrome (SPS), now denote the "GAD antibody-spectrum disorders" (GAD-SD) that also include autoimmune epilepsy, limbic encephalitis, cerebellar ataxia and nystagmus with overlapping symptomatology highlighting autoimmune neuronal excitability disorders. The reasons for the clinical heterogeneity among GAD-antibody associated syndromes remain still unsettled, implicating variable susceptibility of GABAergic neurons to anti-GAD or other still unidentified autoantibodies. Although anti-GAD antibody titers do not correlate with clinical severity, very high serum titers, often associated with intrathecal synthesis of anti-GAD-specific IgG, point to in-situ effects of GAD or related autoantibodies within the central nervous system. It remains, however, uncertain what drives these antibodies, why they persist and whether they are disease markers or have pathogenic potential. The review, focused on these concerns, describes the widened clinical manifestations and overlapping features of all GAD-SD; addresses the importance of GAD antibody titers and potential significance of GAD epitopes; summarizes the biologic basis of autoimmune hyperexcitability; highlights the electrophysiological basis of reciprocal inhibition in muscle stiffness; and provides practical guidelines on symptomatic therapies with gamma-aminobutyric acid-enhancing drugs or various immunotherapies.

Serum IgG-induced microglial activation enhances neuronal cytolysis via the NO/sGC/PKG pathway in children with opsoclonus-myoclonus syndrome and neuroblastoma

Background

Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disease. Some children with OMS also have neuroblastoma (NB). We and others have previously documented that serum IgG from children with OMS and NB induces neuronal cytolysis and activates several signaling pathways. However, the mechanisms underlying OMS remain unclear. Here, we investigated whether nitric oxide (NO) from activated microglias and its cascade contribute to neuronal cytolysis in pediatric OMS.

Methods

The activation of cultured cerebral cortical and cerebellar microglias incubated with sera or IgG isolated from sera of children with OMS and NB was measured by the expression of the activation marker, cytokines, and NO. Neuronal cytolysis was determined after exposing to IgG-treated microglia-conditioned media. Using inhibitors and activators, the effects of NO synthesis and its intracellular cascade, namely soluble guanylyl cyclase (sGC) and protein kinase G (PKG), on neuronal cytolysis were evaluated.

Results

Incubation with sera or IgG from children with OMS and NB increased the activation of cerebral cortical and cerebellar microglias, but not the activation of astrocytes or the cytolysis of glial cells. Moreover, the cytolysis of neurons was elevated by conditioned media from microglias incubated with IgG from children with OMS and NB. Furthermore, the expression of NO, sGC, and PKG was increased. Neuronal cytolysis was relieved by the inhibitors of NO signaling, while neuronal cytolysis was exacerbated by the activators of NO signaling but not proinflammatory cytokines. The cytolysis of neurons was suppressed by pretreatment with the microglial inhibitor minocycline, a clinically tested drug. Finally, increased microglial activation did not depend on the Fab fragment of serum IgG.

Conclusions

Serum IgG from children with OMS and NB potentiates microglial activation, which induces neuronal cytolysis through the NO/sGC/PKG pathway, suggesting an applicability of microglial inhibitor as a therapeutic candidate.

Opsoclonus Following Downbeat Nystagmus in Absence of Visual Fixation in Multiple System Atrophy: Modulation and Mechanisms

We report atypical opsoclonus in a patient with multiple system atrophy and propose a mechanism based on the patterns of modulation by visual, vestibular, and saccadic and vergence stimulation. Firstly, the 6-Hz opsoclonus mostly in the vertical plane occurred only after the development of downbeat nystagmus in darkness without visual fixation. Even after a substantial build-up, visual suppression of the opsoclonus was immediate and complete. Furthermore, the latency for re-emergence of opsoclonus in darkness was greater when the duration of preceding visual fixation was longer. Secondly, the effect of preceding downbeat nystagmus on the development of opsoclonus was evaluated by changing the head position. The opsoclonus did not occur in the supine position when the downbeat nystagmus was absent. After horizontal head shaking, the opsoclonus in the vertical plane gradually evolved into horizontal plane and resumed its vertical direction again after vertical head shaking. Thirdly, any opsoclonus was not triggered by imaginary saccades in the supine position. Lastly, combined vergence and saccadic eye movements during the Müller paradigm did not induce opsoclonus. From these findings of modulation, we suggest that the opsoclonus observed in our patient was invoked by vestibular signals. When the function of the omnipause neurons and saccadic system was impaired, the centrally mediated vestibular eye velocity signals may activate the saccadic system to generate opsoclonus. These atypical patterns of opsoclonus, distinct from the classic opsoclonus frequently observed in para-neoplastic or para-infectious disorders, may be an unrevealing sign of degenerative brainstem or cerebellar disorders.

Gravity-Independent Upbeat Nystagmus in Syndrome of Anti-GAD Antibodies

An autoimmune disorder of the central nervous system, stiff person syndrome, frequently presents with increased titers of 65KD anti-glutamic acid decarboxylase (anti-GAD) antibodies. The clinical phenomenology of this syndrome includes stiffness, ataxia, vertigo due to horizontal gaze-evoked and downbeat vertical nystagmus, and dysmetria of saccades and reaching movements. Here, we describe a novel phenomenology of syndrome of anti-GAD antibody, non-position-dependent upbeat nystagmus and superimposed horizontal gaze-evoked nystagmus. Lack of gravity dependence of primary position upbeat nystagmus, intense nystagmus on up-gaze, relatively stable gaze on downward orientation, and the exponentially decaying waveform suggests neural integrator dysfunction. The titer of anti-GAD in our patient (30 U/ml) was consistent with a variant called "low-titer anti-GAD syndrome". In addition of presenting as an unusual manifestation of a rare neurological syndrome, this case presents a neurochemical correlate of upbeat nystagmus in GABA-mediated control system involving horizontal and vertical neural integrators. Furthermore, the variant of "low-titer anti-GAD syndrome" suggests that GABAergic system may be affected at lower level or antibodies, and/or the epitopes of antibody in those with full-blown clinical syndrome, but low titers of anti-GAD may be different.

IGF-1 alleviates serum IgG-induced neuronal cytolysis through PI3K signaling in children with opsoclonus-myoclonus syndrome and neuroblastoma

BACKGROUND

Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder, usually accompanied by neuroblastoma (NB). There is no targeted treatment and animal model of OMS. We aimed to investigate whether insulin-like growth factor 1 (IGF-1)/phosphoinositide 3-kinase (PI3K) signaling alleviates neuronal cytolysis in pediatric OMS.

METHODS

Cultured rat cerebral cortical neurons and cerebellar neurons were incubated with sera or IgG isolated from sera of children with OMS and NB. Cytolysis and PI3K expression were measured by the lactate dehydrogenase assay and enzyme-linked immunosorbent assay, respectively. Using inhibitors and activators, the effects of IGF-1 and PI3K on cytolysis were investigated.

RESULTS

The incubation of sera or IgG from children with OMS and NB increased cytolysis in not only cerebellar neurons, but also cerebral cortical neurons. Furthermore, the IGF-1 receptor antagonist NVP-AEW541 exaggerated cytolysis in children with OMS and NB. IGF-1 alleviated cytolysis, which was blocked by the PI3K inhibitor LY294002. Additionally, sera or IgG from children with OMS and NB compensatively elevated PI3K expression. LY294002 exacerbated cytolysis; whereas, the PI3K activator 740 Y-P suppressed cytolysis.

CONCLUSION

IGF-1/PI3K signaling alleviates the cytolysis of cultured neurons induced by serum IgG from children with OMS and NB, which may be innovation therapy targets.

Slow saccades in cerebellar disease

Eye movements are frequently considered diagnostic markers indicating involvement of the cerebellum. Impaired amplitude of saccades (saccade dysmetria), impaired gaze holding function (horizontal or downbeat nystagmus), and interrupted (choppy) pursuit are typically considered hallmarks of cerebellar disorders. While saccade dysmetria is a frequently considered abnormality, the velocity of saccades are rarely considered part of the constellation of cerebellar involvement. Reduced saccade velocity, frequently called “slow saccades” are typically seen in a classic disorder of the midbrain called progressive supranuclear palsy. It is also traditionally diagnostic of spinocerebellar ataxia type 2. In addition to its common causes, the slowness of vertical saccades is not rare in cerebellar disorders. Frequently this phenomenology is seen in multisystem involvement that substantially involves the cerebellum. In this review we will first discuss the physiological basis and the biological need for high saccade velocities. In subsequent sections we will discuss disorders of cerebellum that are known to cause slowing of saccades. We will then discuss possible pathology and novel therapeutic strategies.

Update on opsoclonus-myoclonus syndrome in adults

Opsoclonus-myoclonus syndrome in adults is a rare and heterogeneous disorder with the clinical features of opsoclonus, myoclonus, ataxia, and behavioral and sleep disturbances. The pathophysiology is thought to be immunological on the basis of paraneoplastic or infectious etiologies. Immunomodulatory therapies should be performed although the response may be incomplete. A number of autoantibodies have been identified against a variety of antigens, but no diagnostic immunological marker has yet been identified. This review focuses on underlying mechanisms of opsoclonus-myoclonus syndrome, including findings that have been identified recently, and provides an update on the clinical features and treatments of this condition.

The role of the laboratory in the expanding field of neuroimmunology: Autoantibodies to neural targets

Accelerated identification of autoantibodies associated with previously idiopathic neurological disease has provided insights into disease mechanisms, enhanced understanding of neurological function, and opportunities for improved therapeutic interventions. The role of the laboratory in the expanding field of neuroimmunology is critical as specific autoantibody identification provides guidance to clinicians in diagnosis, prognosis, tumor search strategies, and therapeutic interventions. The number of specific autoantibodies identified continues to increase and newer testing strategies increase efficiencies in the laboratory and availability to clinicians. The need for broadly targeted efficient testing is underscored by the variability in clinical presentation and tumor associations attributable to a specific autoantibody, and conversely the various autoantibody specificities that can be the cause of a given clinical presentation. While many of the antineural antibodies were first recognized in the setting of neoplastic disease, idiopathic autoimmune neurological disease in the absence of underlying tumor is increasingly recognized. Appropriation of therapeutic modalities used to treat autoimmune disease to treat these autoantibody mediated neurological diseases has improved patient outcomes. Interaction between clinicians and laboratorians is critical to our understanding of these diseases and optimization of the clinical benefits of our increasing knowledge in neuroimmunology.

Brain volumetric analysis and cortical thickness in adults with saccadic intrusions (ocular flutter or opsoclonus-myoclonus syndrome)

OBJECTIVES

Ocular flutter (OF) and opsoclonus are considered a continuum with a similar pathogenesis. Due to the rarity of this disease in the adult population, little is known about the brain morphological changes in the chronic phase of the disease.

PATIENTS AND METHODS

Six magnetic resonance imaging from adults with previous history of OF/Opsoclonus and 12 healthy patients (paired by age and sex) were analyzed in order to identify the long term cortical thickness pattern in this rare disease by using Freesurfer.

RESULTS

Patients with OF/Opsoclonus showed reduced cerebellum cortical volume with a subsequent diminution in total cerebellar volume. White mater cerebellum volume was not modified. In addition, we have also identified a significant supratentorial gray matter volume decrease in OF/Opsoclonus patients, involving both the cortical and the subcortical gray matter.

CONCLUSIONS

OF/Opsoclonus in adults may be associated with cortical and subcortical gray matter atrophy, as well as decreased cerebellar cortical volume. Further larger prospective studies are necessary to confirm these results.

Autoimmune Movement Disorders: a Clinical and Laboratory Approach

Autoimmune movement disorders are caused by an aberrant immune response to neural self-antigens. These disorders may be paraneoplastic, parainfectious, or (most commonly) idiopathic. The neurological presentations are diverse, and sometimes multifocal. Movement disorders can occur as part of the spectrum with phenotypes including chorea, myoclonus, ataxia, CNS hyperexcitability (including stiff-person syndrome), dystonia, and parkinsonism. Symptoms are subacute in onset and may have a fluctuating course. The best characterized disorders are unified by neural autoantibodies identified in serum or cerebrospinal fluid. The antibody specificity may predict the association with cancer and the response to immunotherapy. In this article, we review autoimmune-mediated movement disorders, associated cancers, diagnosis, and treatment.

Clinical Approach to Supranuclear Brainstem Saccadic Gaze Palsies

Failure of brainstem supranuclear centers for saccadic eye movements results in the clinical presence of a brainstem-mediated supranuclear saccadic gaze palsy (SGP), which is manifested as slowing of saccades with or without range of motion limitation of eye movements and as loss of quick phases of optokinetic nystagmus. Limitation in the range of motion of eye movements is typically worse with saccades than with smooth pursuit and is overcome with vestibular–ocular reflexive eye movements. The differential diagnosis of SGPs is broad, although acute-onset SGP is most often from brainstem infarction and chronic vertical SGP is most commonly caused by the neurodegenerative condition progressive supranuclear palsy. In this review, we discuss the brainstem anatomy and physiology of the brainstem saccade-generating network; we discuss the clinical features of SGPs, with an emphasis on insights from quantitative ocular motor recordings; and we consider the broad differential diagnosis of SGPs.

Cerebellar disease associated with anti-glutamic acid decarboxylase antibodies: review

Several neurological syndromes have been recognized associated to GAD antibodies. Among those disorders, cerebellar ataxia (CA) is one of the most common, along with stiff-person syndrome. Patients with GAD associated CA present with a progressive pancerebellar syndrome, with a subacute or chronic evolution, along with other neurological manifestations such as stiffness, oculomotor dysfunction, epilepsy, and cognitive dysfunction. These symptoms may be preceded by the so-called "brainstem attacks", where manifestations consistent with transient dysfunction of the brainstem may be observed. These patients frequently have extra-neurologic autoimmune manifestations such as diabetes mellitus type 1, polyendocrine autoimmune syndrome, pernicious anemia, vitiligo, etc. A proportion of patients may present with an underlying neoplasia, but the course is less aggressive than in those patients with classical paraneoplastic CA with onconeural antibodies. The diagnosis is based on the present of high serum and CSF titers of GAD antibodies, with intrathecal production of such antibodies. Treatment is aimed to decrease the immunological response with intravenous immunoglobulin, steroids, rituximab and oral immunosuppressive drugs. A subacute presentation and rapid initiation of immunotherapy seem to be the predictors of a favorable clinical response.

Basic and translational neuro-ophthalmology of visually guided saccades: disorders of velocity

Introduction

Saccades are rapid, yoked eye movements in an effort to direct a target over fovea. The complex circuitry of saccadic eye movements has been exhaustively described. As a result clinicians can elegantly localize the pathology if it falls on the neuraxis responsible for saccades. Traditionally saccades are studied with their quantitative characteristics such as amplitude, velocity, duration, direction, latency and accuracy.

Areas covered

Amongst all subtypes, the physiology of the visually guided saccades is most extensively studied. Here we will review the basic and pertinent neuro-anatomy and physiology of visually guided saccade and then discuss common or classic disorders affecting the velocity of visually guided saccades. We will then discuss the basic mechanism for saccade slowing in these disorders.

Expert commentary

Prompt appreciation of disorders of saccade velocity is critical to reach appropriate diagnosis. Disorders of midbrain, cerebellum, or basal ganglia can lead to prolonged transition time during gaze shift and decreased saccade velocity.

Opsoclonus in a patient with increased titers of anti-GAD antibody provides proof for the conductance-based model of saccadic oscillations

Paucity in gamma-amino butyric acid (GABA) due to blockage in the action of glutamic acid decarboxylase (GAD), as seen in the syndrome of anti-GAD antibody, causes adult onset cerebellar ataxia, muscle rigidity, and episodic spasms. Downbeat nystagmus, saccadic dysmetria, impaired ocular pursuit, and impaired cancelation of vestibular ocular reflex are typical ocular motor deficits in patients with syndrome of anti-GAD antibody. We describe opsoclonus, in addition to downbeat nystagmus, in a patient with increased titers of anti-GAD antibody. Paucity in GABA leading to disinhibition to Purkinje target neurons at deep cerebellar and vestibular nuclei might have caused downbeat nystagmus in our patient. Anti-GAD antibody can also increase levels of glutamate the precursor of GABA and the substrate for the action of GAD. We propose that opsoclonus might be due to increased levels of glutamate and subsequent hyperexcitability of excitatory and inhibitory burst neurons leading to reverberation in their reciprocally innervating circuit.

Ataxia

Ataxia is a disorder of balance and coordination resulted from dysfunctions involving cerebellum and its afferent and efferent connections. While a variety of disorders can cause secondary ataxias, the list of genetic causes of ataxias is growing longer. Genetic abnormalities may involve mitochondrial dysfunction, oxidative stress, abnormal mechanisms of DNA repair, possible protein misfolding, and abnormalities in cytoskeletal proteins. Few ataxias are fully treatable while hope for efficacious gene therapy and pharmacotherapy is emerging. A discussion of the ataxias is presented here with brief mention of acquired ataxias, and a greater focus on inherited ataxias.

Alternating skew deviation in association with anti-glutamic acid decarboxylase antibodies

The presence of an elevated anti-glutamic acid decarboxylase (GAD) antibody level has been associated with a number of eye movement abnormalities, as well as other findings including cerebellar ataxia and insulin dependent diabetes mellitus. Skew deviation in association with anti-GAD antibodies has not been previously reported. Here we report a case of alternating skew deviation along with cerebellar-brainstem signs in a patient with an elevated anti-GAD antibody titer. Follow-up neurologic evaluation after treatment with intravenous immunoglobulin revealed improvement in cerebellar-brainstem signs, while ophthalmic evaluation was stable.

Opsoclonus-myoclonus syndrome following rotavirus gastroenteritis

Opsoclonus-myoclonus syndrome (OMS) is a rare neurologic disorder characterized by opsoclonus, myoclonus, ataxia and behavioral disturbance. In the pathogenesis, an autoimmune process with infectious or paraneoplastic trigger has been suggested. We describe the case of a 22-month-old girl with OMS following rotavirus gastroenteritis. Rotavirus should be considered in the differential diagnosis of OMS in children.

GABA-A receptor impairment in cerebellar ataxia with anti-glutamic acid decarboxylase antibodies

Antibodies against glutamic acid decarboxylase (GAD-Abs) are associated with cerebellar ataxia, which is refractory to treatment with GABAergic drugs. To investigate the GABAergic neuronal system in vivo, we performed a combined positron emission tomography (PET) study with [(11)C]-flumazenil and [(18)F]-fluorodeoxyglucose (FDG) in three patients with cerebellar ataxia with GAD-Abs. The GABA-A receptor function was investigated using flumazenil, which is a selective GABA-A receptor ligand, while FDG-PET using a three-dimensional stereotactic surface projection analysis was performed to estimate the metabolic rates of glucose (MRGlc) in the patients. GABAergic drugs showed no efficacy for the cerebellar ataxia in all three patients, and all three displayed a significant decrease in flumazenil binding in the cerebellum. No MRGlc decrease in the cerebellum was found in the two patients who presented with amelioration of cerebellar ataxia following intravenous immunoglobulin (IVIG) therapy, whereas a significant MRGlc decrease in the cerebellar hemisphere was observed in another patient who showed severe cerebellar atrophy on magnetic resonance images and no response to the IVIG therapy. The decreased flumazenil binding in the present patients indicated cerebellar GABA-A receptor impairment, which may be due to either neuronal cell loss, as demonstrated by the decreased MRGlc, or a dysfunction in GABAergic neuronal inhibition. Although GAD-Abs have been postulated to prevent the synthesis of GABA, resulting in decreased GABAergic transmission, the GABA-A receptor impairment may play another pathogenic role in cerebellar ataxia associated with GAD-Abs resulting in a condition refractory to GABAergic drug therapy.

Presentation of opsoclonus myoclonus ataxia syndrome with glutamic acid decarboxylase antibodies

In this rare case, the patient presented with opsoclonus, myoclonus and ataxia. Serological and imaging studies revealed high glutamic acid decarboxylase antibody (GAD-Ab) levels. High-dose corticosteroids were of no benefit and subsequent intravenous immunoglobulin (IVIg) administration proved resolution of the condition. Levetiracetam proved useful in symptomatically controlling the myoclonus. Follow-up GAD-Ab levels were within normal limits.

Cognitive decline in a patient with anti-glutamic acid decarboxylase autoimmunity; case report

Background

Glutamic acid decarboxylase (GAD) is the rate-limiting enzyme for producing γ-aminobutyric acid, and it has been suggested that antibodies against GAD play a role in neurological conditions and type 1 diabetes. However, it is not known whether dementia appears as the sole neurological manifestation associated with anti-GAD antibodies in the central nervous system.

Case presentation

We describe the clinical, neuropsychological, and neuroradiological findings of a 73-year-old female with cognitive dysfunction and type 1A diabetes. Observation and neuropsychological studies revealed linguistic problems, short-term memory disturbance, and frontal dysfunction. MRI showed no significant lesion except for confluent small T2-hyperintensity areas localized in the left basal ganglia. ¹⁸F-fluorodeoxy glucose-positron emission tomography (FDG-PET) and ¹²³I-N-isopropyl-p-iodoamphetamine-single photon emission computed tomography (IMP-SPECT) studies showed bifrontal hypometabolism and hypoperfusion. Immunomodulating therapy with intravenous high-dose immunoglobulin resulted in no remission of the cognitive symptoms.

Conclusions

Cognitive dysfunction may develop as an isolated neurological manifestation in association with type 1A diabetes and anti-GAD autoimmunity. A systematic study with extensive neuropsychological assessment is indicated in patients with type 1 diabetes and anti-GAD autoimmunity.

Anti-glutamic Acid decarboxylase antibody-associated ataxia as an extrahepatic autoimmune manifestation of hepatitis C infection: a case report

Extrahepatic immunological manifestations of hepatitis C virus (HCV) are well described. In addition, antiglutamic acid decarboxylase (GAD) antibody-associated cerebellar ataxia is well-established entity. However, there have been no reports in the literature of anti-GAD antibody-associated ataxia as an extrahepatic manifestation of HCV infection. We report the case of a young woman with chronic hepatitis C virus and multiple extrahepatic autoimmune diseases including Sjögren syndrome and pernicious anemia who presented with subacute midline cerebellar syndrome and was found to have positive antiglutamic acid decarboxylase (GAD) antibody in the serum and cerebrospinal fluid. An extensive diagnostic workup to rule out neoplastic growths was negative, suggesting the diagnosis of nonparaneoplastic antiglutamic acid decarboxylase antibody-associated cerebellar ataxia as an additional extrahepatic manifestation of hepatitis C virus infection. The patient failed to respond to high-dose steroids and intravenous immunoglobulin. Treatment with the monoclonal antibody rituximab stabilized the disease. We postulate that anti-GAD associated ataxia could be an extrahepatic manifestation of HCV infection.

Opsoclonus-myoclonus syndrome in anti-N-methyl-D-aspartate receptor encephalitis

BACKGROUND

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis has been recently reported as autoimmune/paraneoplastic encephalitis, affecting mostly young females.

OBJECTIVE

To describe opsoclonus-myoclonus syndrome in association with anti-NMDAR antibodies.

DESIGN

Case report.

SETTING

Geneva University Hospital. Patient A 23-year-old woman with opsoclonus-myoclonus syndrome.

RESULTS

Two weeks after an episode of gastroenteritis, the patient developed symptoms of depression associated with psychomotor slowing, progressive gait instability, and opsoclonus-myoclonus. Cerebrospinal fluid examination showed mild lymphocytic pleocytosis and intrathecal IgG synthesis with oligoclonal bands. The patient's condition worsened rapidly to an akinetic mutism, followed by a period of agitation, delirium, and hallucinations. These gradually subsided; however, a frontal behavior and executive dysfunction persisted 5 months after symptom presentation. No tumor was found. Anti-NMDAR antibodies were found in the cerebrospinal fluid.

CONCLUSIONS

Opsoclonus-myoclonus may occur in patients with anti-NMDAR encephalitis. Prompt diagnosis of this disorder is important because after tumor removal and immunomodulatory therapies it has a relatively good prognosis.