Post-ganglionic autonomic neuropathy associated with anti-glutamic acid decarboxylase antibodies

Glutamic acid decarboxylase 65-positive autoimmune encephalitis presenting with gelastic seizure, responsive to steroid: A case report

BACKGROUND

Anti-glutamic acid decarboxylase (GAD) antibody is known to cause several autoimmune-related situations. The most known relationship is that it may cause type I diabetes. In addition, it was also reported to result in several neurologic syndromes including stiff person syndrome, cerebellar ataxia, and autoimmune encephalitis. Decades ago, isolated epilepsy associated with anti-GAD antibody was first reported. Recently, the association between temporal lobe epilepsy and anti-GAD antibody has been discussed. Currently, with improvements in examination technique, many more autoimmune-related disorders can be diagnosed and treated easier than in the past.

CASE SUMMARY

A 44-year-old female Asian with a history of end-stage renal disease (without diabetes mellitus) under hemodialysis presented with diffuse abdominal pain. The initial diagnosis was peritonitis complicated with sepsis and paralytic ileus. Her peritonitis was treated and she recovered well, but seizure attack was noticed during hospitalization. The clinical impression was gelastic seizure with the presentation of frequent smiling, head turned to the right side, and eyes staring without focus; the duration was about 5–10 s. Temporal lobe epilepsy was recorded through electroencephalogram, and she was later diagnosed with anti-GAD65 antibody positive autoimmune encephalitis. Her seizure was treated initially with several anticonvulsants but with poor response. However, she showed excellent response to intravenous methylprednisolone pulse therapy. Her consciousness returned to normal, and no more seizures were recorded after 5 d of intravenous methylprednisolone treatment.

CONCLUSION

In any case presenting with new-onset epilepsy, in addition to performing routine brain imaging to exclude structural lesion and cerebrospinal fluid studies to exclude common etiologies of infection and inflammation, checking the autoimmune profile has to be considered. In the practice of modern medicine, autoimmune-related disorders are relatively treatable and should not be missed.

Antibody Testing for Suspected Autoimmune Autonomic Dysfunction and Small Fiber Neuropathies

SUMMARY

Autonomic dysfunction and small fiber neuropathies are heterogeneous disorders with a wide array of potential etiologies. As with other neurologic diseases, autoantibodies specific to neural tissue, either in the setting of cancer or systemic autoimmunity, may cause autonomic abnormalities. Given the complex and varied functions of the autonomic nervous system, however, the presentation of these conditions may be quite variable. This, in addition to pitfalls of autonomic testing especially for the novice, can lead to inaccuracies in recognizing and characterizing these conditions. We now have a large number of autoantibodies available for testing with more in the pipeline thanks to unprecedented developments in the field of neuroimmunology. Those have been very helpful in uncovering potentially treatable mechanisms of autonomic disease, but also pose a challenge to the clinician given their multiplicity and variable specificity. Growing knowledge regarding autoimmune autonomic implications and the autonomic specificities of each antibody, in addition to the increasing attention to the relevance of antibody titers are of utmost importance for clinicians concerned with autonomic neurology. This review attempts to shed a light on the frequently encountered antibodies in relation to autonomic dysfunction.

Ataxia and ophthalmoplegia: an atypical case of Miller Fisher syndrome (MFS) with anti-GAD antibody

BACKGROUND

Miller Fisher syndrome (MFS) is frequently encountered variant of Gillian Barre Syndrome (GBS). It has distinct clinical and serological features. Here we describe an atypical GQ1b seronegative case with significantly elevated anti-glutamic acid decarboxylase antibody (GAD-Ab).

CASE DESCRIPTION

A 24-year-old previously healthy Caucasian male presented with rapidly progressive ascending weakness, binocular diplopia and autonomic instability for 2 days. Examination was remarkable for asymmetrical facial weakness (L > R), opthalmoplegia and truncal ataxia without areflexia. MRI brain was normal. CSF analysis showed elevated protein. Electromyography/Nerve Conduction Study (EMG/NCS) within the first week was normal. Antiganglioside antibodies were negative. Extended serological and neoplastic workup revealed negative anti-GQ1b antibody, but significant increase of GAD-Ab, Voltage Gated Calcium Channel (VGCC) Ab, and mild elevation of TPO Ab IgG and Thyroglobulin (Tg) Ab IgG. Clinical diagnosis of partial MFS was made. He received a course of IVIg (2 g/kg over 5 days) and had complete recovery in 3 months.

CONCLUSION

There are incomplete or atypical forms of MFS. Recognition of its various clinical presentations is essential for early diagnosis and optimal management. Further investigation is needed to elucidate the role of anti-GAD-ab and other autoimmune antibodies in the pathogenesis of GQ1b-seronegative MFS patients.

Glutamic Acid Decarboxylase (GAD-65) Autoimmunity Associated With Profound Daytime Hypersomnia, Nighttime Insomnia, Mild Autonomic Neuropathy and Axonal Sensori-Motor Polyneuropathy: A Case Report on a New Phenotype

We describe the case of a 74-year-old fit and healthy man who developed a profound sleep disorder characterized by mid-day hypersomnia and debilitating insomnia. A wide range of therapies, including a large number of stimulants and hypnotics with multiple different mechanisms of action, failed to improve his condition. Trials with oral prosthetic devices and a wide range of face masks with positive pressure assistance and multiple continuous positive airway pressure (CPAP) titration studies failed to help. Along with his sleep disorder, our patient developed a slowly evolving axonal sensorimotor polyneuropathy with a subtle autonomic neuropathy. Due to the latter two conditions, a comprehensive paraneoplastic panel was obtained and revealed extremely high titer glutamic acid decarboxylase (GAD-65) autoantibodies. This was confirmed by three independent laboratories and by cerebrospinal fluid staining of rat hippocampus, revealing the classic tram-track lines along the dentate gyrus. Our patient was treated empirically with intravenous immunoglobulin. We believe that our case reveals a unique syndrome related to GAD-65 autoantibodies and adds to the growing list of GAD-65 associated diseases. This case is particularly provocative as it raises the idea to check for GAD-65 autoimmunity in patients who suffer from a profound sleep disorder resistant to conventional treatment.

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.

Management of Autoimmune Encephalitis: An Observational Monocentric Study of 38 Patients

Over the last years the clinical picture of autoimmune encephalitis has gained importance in neurology. The broad field of symptoms and syndromes poses a great challenge in diagnosis for clinicians. Early diagnosis and the initiation of the appropriate treatment is the most relevant step in the management of the patients. Over the last years advances in neuroimmunology have elucidated pathophysiological basis and improved treatment concepts. In this monocentric study we compare demographics, diagnostics, treatment options and outcomes with knowledge from literature. We present 38 patients suffering from autoimmune encephalitis. Antibodies were detected against NMDAR and LGI1 in seven patients, against GAD in 6 patients) one patient had coexisting antibodies against GABA_A and GABA_B), against CASPR2, IGLON5, YO, Glycine in 3 patients, against Ma-2 in 2 patients, against CV2 and AMPAR in 1 patient; two patients were diagnosed with hashimoto encephalitis with antibodies against TPO/TG. First, we compare baseline data of patients who were consecutively diagnosed with autoimmune encephalitis from a retrospective view. Further, we discuss when to stop immunosuppressive therapy since how long treatment should be performed after clinical stabilization or an acute relapse is still a matter of debate. Our experiences are comparable with data from literature. However, in contrary to other experts in the field we stop treatment and monitor patients very closely after tumor removal and after rehabilitation from first attack.

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.