Spontaneous downbeat nystagmus as a clue for the diagnosis of ataxia associated with anti-GAD antibodies

Assessment of anti-GAD65-associated cerebellar ataxia with 18F-FDG cerebellar uptake: ROC analysis

OBJECTIVE

Anti-glutamic acid decarboxylase 65 (anti-GAD65)-associated neurological disorders include two major phenotypes, namely Stiff person syndrome (SPS) and cerebellar ataxia (CA). Considering the potential for better outcomes with prompt immunotherapy, early detection of CA is crucial. Hence, a non-invasive imaging biomarker to detect CA with high specificity is desired. Herein, we evaluated brain 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) PET in detecting CA based on cerebellar uptake using receiver operating characteristic (ROC) analysis and five-fold cross-validation.

METHODS

This study was based on STARD 2015 guidelines: thirty patients with anti-GAD65-associated neurological disorders, 11 of whom with CA were studied. Five test sets were created after patients were randomly sorted and divided into 5 equal folds. Each iteration included 24 patients for ROC analysis and 6 patients reserved for testing. The Z scores of left cerebellum, vermis, right cerebellum, and the average of the three regions were used in ROC analysis to determine areas with significant area under the curve (AUC). The cut-off values with high specificity were determined among the 24 patients in each iteration and tested against the reserved 6 patients.

RESULTS

Left cerebellum and average of the three regions showed significant AUC above 0.5 in all iterations with left cerebellum being the highest AUC in 4 iterations. Testing the cut-off values of the left cerebellum against the reserved 6 patients in each iteration showed 100% specificity with sensitivities ranging from 0 to 75%.

CONCLUSIONS

Cerebellar 18F-FDG PET uptake can differentiate CA phenotypes from patients with SPS with high specificity.

Spontaneous Downbeat Nystagmus in Anti-GAD-Antibody-Associated Paraneoplastic Syndrome

Spontaneous downbeat nystagmus and ocular flutter are rare clinical signs. Such findings are commonly related to cerebellar pathology, predominantly ischemia. In a significant percentage of patients, the cause may not be found. If these signs are associated with ataxia, cognitive decline, and seizure, anti-glutamic acid decarboxylase-associated neurological syndrome must be suspected. Background history of tumor has to be enquired. Treatment with immune modulation helps in partial recovery of such cases.

Ocular Motor and Vestibular Characteristics of Antiglutamic Acid Decarboxylase-Associated Neurologic Disorders

BACKGROUND

Antiglutamic acid decarboxylase (GAD)-associated neurologic disorders are rare, with varied presentations, including stiff-person syndrome (SPS) and cerebellar ataxia (CA). Vestibular and ocular motor (VOM) dysfunction can be the main presentation in a subset of patients.

METHODS

Retrospective review of the Johns Hopkins Hospital medical records from 1997 to 2018 identified a total of 22 patients with a diagnosis of anti-GAD-associated SPS or CA who had detailed VOM assessments. Eight had prominent VOM dysfunction at the initial symptom onset and were referred to neurology from ophthalmology or otolaryngology ("early dominant"). Fourteen patients had VOM dysfunction that was not their dominant presentation and were referred later in their disease course from neurology to neuro-ophthalmology ("nondominant"). We reviewed clinical history, immunological profiles, and VOM findings, including available video-oculography.

RESULTS

In the 8 patients with early dominant VOM dysfunction, the average age of symptom onset was 53 years, and 5 were men. The most common symptom was dizziness, followed by diplopia. Seven had features of CA, and 4 had additional features of SPS. None had a structural lesion on brain MRI accounting for their symptoms. The most common VOM abnormalities were downbeating and gaze-evoked nystagmus and saccadic pursuit. All received immune therapy and most received symptomatic therapy. Most experienced improvement in clinical outcome measures (modified Rankin scale and/or timed 25-foot walk test) or VOM function. By contrast, in the 14 patients in whom VOM dysfunction was nondominant, most had an SPS phenotype and were women. VOM abnormalities, when present, were more subtle, although mostly still consistent with cerebellar and/or brainstem dysfunction.

CONCLUSIONS

Individuals with anti-GAD-associated neurologic disorders may present with prominent VOM abnormalities at the initial symptom onset that localize to the cerebellum and/or brainstem. In our cohort, immune and symptomatic therapies improved clinical outcomes and symptomatology.

Downbeat nystagmus: a clinical review of diagnosis and management

PURPOSE OF REVIEW

This review will extensively cover the clinical manifestations, causes, diagnostic evaluation, and management strategies of downbeat nystagmus (DBN).

RECENT FINDINGS

Historically, MRI to assess for structural lesions at the cervicomedullary junction has been the primary diagnostic test in the evaluation of DBN since the 1980s. In recent years, there is increasing awareness of nonstructural causes of DBN including gluten ataxia, nutritional deficiencies, and paraneoplastic syndromes, among others. Medical management with aminopyridines has become first-line therapy in addition to disease-specific therapies.

SUMMARY

DBN is a common form of acquired nystagmus and the differential diagnosis remains broad, including both benign and potentially fatal causes. For practical purposes, the causes can be categorized as structural vs. nonstructural with MRI as the ideal, initial diagnostic study to differentiate the two. General therapeutic options include pharmacotherapy to enhance Purkinje cell function, strabismus surgery or prisms to shift null points, and behavioural changes. Disease-specific treatment is necessarily broad, though a significant proportion of patients will be idiopathic.

Downbeat Nystagmus in a 7-Year-Old Girl With Epstein-Barr Virus-Associated Meningitis and Cerebellitis

Downbeat nystagmus is a type of jerk nystagmus that may be seen in patients with lesions affecting the vestibulocerebellum. This is a case of a 7-year-old girl presenting with a history of fever, headache, and episodic vertigo with downbeat nystagmus. The diagnosis of Epstein-Barr virus meningitis with acute cerebellitis was made by contrast magnetic resonance imaging, cerebrospinal fluid analysis, and serum Epstein-Barr virus titers. Contrast magnetic resonance imaging demonstrated enhancement of the meninges and inferior cerebellar folia, correlating with the neuroophthalmological symptom of downbeat nystagmus.

Autoimmune Encephalitis in Latin America: A Critical Review

Autoimmune encephalitis is an increasingly recognized cause of encephalitis. The majority of case series report patients residing in developed countries in the northern hemisphere. The epidemiologic features of autoimmune encephalitis in Latin America are still unclear. The aim of the study was to perform a review of the clinical presentation of autoimmune encephalitis in Latin America and compare to world literature. References were identified by an in-depth literature search and selected on the basis of relevance to the topic and authors' judgment. We selected clinical studies and case reports published from 2007 to July, 2020 including patients from Latin American countries. Of the 379 patients included, the majority were cases of anti-NMDA receptor encephalitis (93.14%), followed by anti-VGKC-complex encephalitis (N = 17; 4.48%), anti-GAD encephalitis (N = 9; 2.37%), anti-AMPA receptor encephalitis (N = 1; 0.26%), anti-GABA receptor encephalitis (N = 1; 0. 26%), anti-mGluR5 encephalitis (N = 1; 0. 26%), and anti-mGluR1 encephalitis (N = 1; 0. 26%). Reported cases of Anti-NMDA encephalitis in Latin-America had a very slight female predominance, lower prevalence of associated tumors and a lower incidence of extreme delta brush on electroencephalogram. Autoimmune encephalitis is possibly underdiagnosed in underdeveloped countries. Its outcome after treatment, however, appears to be similarly favorable in Latin American patients as has been reported in developed countries based on available case reports and case series. Regional specificities in the manifestation of autoimmune encephalitis could be related to epidemiologic factors, such as the presence of different triggers and different genetic and immunologic background, that need to be studied by future research.

Acute cerebellar ataxia: differential diagnosis and clinical approach

Cerebellar ataxia is a common finding in neurological practice and has a wide variety of causes, ranging from the chronic and slowly-progressive cerebellar degenerations to the acute cerebellar lesions due to infarction, edema and hemorrhage, configuring a true neurological emergency. Acute cerebellar ataxia is a syndrome that occurs in less than 72 hours, in previously healthy subjects. Acute ataxia usually results in hospitalization and extensive laboratory investigation. Clinicians are often faced with decisions on the extent and timing of the initial screening tests, particularly to detect treatable causes. The main group of diseases that may cause acute ataxias discussed in this article are: stroke, infectious, toxic, immune-mediated, paraneoplastic, vitamin deficiency, structural lesions and metabolic diseases. This review focuses on the etiologic and diagnostic considerations for acute ataxia.

Autoimmune encephalitis: a review of diagnosis and treatment

Autoimmune encephalitis (AIE) is one of the most common causes of noninfectious encephalitis. It can be triggered by tumors, infections, or it may be cryptogenic. The neurological manifestations can be either acute or subacute and usually develop within six weeks. There are a variety of clinical manifestations including behavioral and psychiatric symptoms, autonomic disturbances, movement disorders, and seizures. We reviewed common forms of AIE and discuss their diagnostic approach and treatment.

Vertical nystagmus associated with glutamic acid decarboxylase antibodies responding to cyclophosphamide

Several neurological disorders have been described in patients with autoimmunity associated with GAD antibodies. Among these disorders, nystagmus and oculomotor dysfunction are increasingly recognized, although they have been rarely reported isolated or as the main manifestation of anti-GAD autoimmunity. Moreover, therapeutic approaches for such patients are unclear. Here we present a 44-year-old man with disabling oscillopsia secondary to downbeat nystagmus, abnormal saccades, ocular pursuit and optokinetic nystagmus, as well as mild gait ataxia and cerebellar atrophy associated with high serum GAD antibodies with intrathecal secretion of such antibodies. The patient did not have clinical benefit with plasma exchange, but had a robust symptomatic improvement with cyclophosphamide. We discuss the possible pathogenic role of GAD antibodies in nystagmus and the role of immunotherapy in these patients.

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.

Finger extension weakness and downbeat nystagmus motor neuron disease syndrome: A novel motor neuron disorder?

Introduction: Disturbances of eye movements are infrequently encountered in motor neuron diseases (MNDs) or motor neuropathies, and there is no known syndrome that combines progressive muscle weakness with downbeat nystagmus. Methods: To describe the core clinical features of a syndrome of MND associated with downbeat nystagmus, clinical features were collected from 6 patients. Results: All patients had slowly progressive muscle weakness and wasting in combination with downbeat nystagmus, which was clinically most obvious in downward and lateral gaze. Onset was in the second to fourth decade with finger extension weakness, progressing to other distal and sometimes more proximal muscles. Visual complaints were not always present. Electrodiagnostic testing showed signs of regional motor axonal loss in all patients. Discussion: The etiology of this syndrome remains elusive. Because finger extension weakness and downbeat nystagmus are the discriminating clinical features of this MND, we propose the name FEWDON‐MND syndrome. Muscle Nerve56: 1164–1168, 2017

Clinical characteristics of patients with cerebellar ataxia associated with anti-GAD antibodies

ABSTRACT The enzyme glutamic acid decarboxylase (GAD), present in GABAergic neurons and in pancreatic beta cells, catalyzes the conversion of gamma-aminobutyric acid (GABA). The cerebellum is highly susceptible to immune-mediated mechanisms, with the potentially treatable autoimmune cerebellar ataxia associated with the GAD antibody (CA-GAD-ab) being a rare, albeit increasingly detected condition. Few cases of CA-GAD-ab have been described. Methods This retrospective and descriptive study evaluated the clinical characteristics and outcomes of patients with CA-GAD-ab. Result Three patients with cerebellar ataxia, high GAD-ab titers and autoimmune endocrine disease were identified. Patients 1 and 2 had classic stiff person syndrome and insidious-onset cerebellar ataxia, while Patient 3 had pure cerebellar ataxia with subacute onset. Patients received intravenous immunoglobulin therapy with no response in Patients 1 and 3 and partial recovery in Patient 2. Conclusion CA-GAD-ab is rare and its clinical presentation may hamper diagnosis. Clinicians should be able to recognize this potentially treatable autoimmune cerebellar ataxia.