Striational Antibodies Research Articles

Acquired Rippling Muscle Disease with Acetylcholine Receptor Antibodies (P1-8.008)

<h3>Objective:</h3> To report a case series of acquired rippling muscle disease (RMD) with acetylcholine receptor (AChR) antibodies. <h3>Background:</h3> Previous studies have demonstrated association of acquired RMD with autoimmune disorders, or less commonly with cancer. AChR antibodies are often observed in RMD in parallel with the presumed immune-mediated etiology of acquired RMD. Despite having AChR antibodies, acquired RMD patients may exhibit minimal or no manifestations of myasthenia gravis (MG). Treatment selection in these RMD patients may prove challenging. <h3>Design/Methods:</h3> All cases of acquired RMD seen at our institution since 2010 were identified by search of the electronic medical record. <h3>Results:</h3> Three patients with acquired RMD were identified. These were men with classic RMD symptoms beginning in the fourth to sixth decade. Two developed ocular MG after onset of RMD, while the third had no MG symptoms. None had other autoimmune disorders or malignancy. AChR-binding antibodies were detected in all three patients, and two had positive striational antibodies. None had thymoma. Creatine kinase was mildly elevated, and caveolin-3 genetic testing was negative in all three patients. Concentric needle electromyography showed electrical silence during spontaneous muscle contractions in 2 of 3 patients. The third patient exhibited decreased caveolin-3 and dystrophin sarcolemmal immunoreactivity on muscle biopsy. All patients received at least one immunosuppressive (IS) therapy. While MG symptoms responded to IS treatment, RMD symptoms were more refractory. Only one individual who received intravenous immunoglobulin (IVIg) experienced significant improvement in RMD symptoms. Symptomatic treatment for RMD yielded only minimal benefit. <h3>Conclusions:</h3> Acquired RMD is a rare disorder of muscular hyperexcitability, presumably related to an underlying immune-mediated phenomenon. Most cases of RMD/MG were heralded by RMD and may only exhibit minimal or no manifestations of MG despite AChR antibody positivity. IS therapies appear to be ineffective for RMD symptoms, although one patient had significant symptomatic benefit with IVIg. <b>Disclosure:</b> Dr. Wannarong has nothing to disclose. Dr. Gable has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Medscape, Web MD. Dr. Gable has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Pharmacy Times. Dr. Gable has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Cowen. Dr. Gable has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Argenx. Dr. Gable has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Ultragenx. Dr. Gable has received personal compensation in the range of $5,000-$9,999 for serving as a Lecture series with Medscape. Dr. Juel has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Immunovant. Dr. Juel has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion. Dr. Juel has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Accordant Health Services. The institution of Dr. Juel has received research support from argenx. The institution of Dr. Juel has received research support from Alexion. The institution of Dr. Juel has received research support from Janssen. The institution of Dr. Juel has received research support from NIH Rare Diseases Network.

Incidence and causes of overdiagnosis of myasthenia gravis.

We have encountered non-myasthenic patients being given a diagnosis of myasthenia gravis (MG). This study aims to investigate the frequency of, and factors contributing to, overdiagnosis of MG. This is a retrospective analysis of patients referred to our tertiary neuromuscular center for evaluation due to a previously suspected/confirmed MG diagnosis during a 6-year span. A total of 531 patients sought a second opinion regarding their MG diagnosis, and 77 (14.5%) were found to have non-myasthenic conditions. A total of 11 patients tested positive for acetylcholine receptor (AChR) antibodies. Repeated AChR antibodies became negative in five patients while in four patients, AChR binding antibody titers were persistently low. In seven patients, striational antibody was the only positive antibody identified. In 25 patients, a prior electrodiagnostic (EDX) study was deemed positive, including 14 patients with abnormal repetitive nerve stimulation (RNS) and 12 with abnormal single fiber electromyography (SFEMG). Technical issues were noted on prior RNS studies in 8 patients, and repeat RNS was negative in 10 patients. In eight patients with previously abnormal SFEMG, results showed minimal or equivocal abnormalities. In two patients, a repeat SFEMG was normal. Further analysis revealed atypical clinical presentation, deceptively positive ice pack test, clinically insignificant antibody result and misleading EDX finding as main contributors to MG overdiagnosis. Overdiagnosis of MG is not uncommon, and occurs more frequently in seronegative patients. To make an accurate diagnosis of MG, there is a need to recognize atypical presentations, and avoid overreliance on minor or non-specific serological and electrodiagnostic findings.

Acetylcholine receptor antibodies in a patient with sensory neuropathy

Antibodies to acetylcholine receptor (AChR) are detected in the vast majority of patients with generalized myasthenia gravis (MG) and are rarely detected in significant titer in other autoimmune diseases. We report a patient with an axonal predominately sensory neuropathy for over 12 years with persistent binding and modulating AChR antibodies as well as striational muscle antibodies with no evidence of MG or any neoplastic disease.

Autoantibodies in Patients With Immune-Related Adverse Events From Checkpoint Inhibitors: A Systematic Literature Review.

Immune-related adverse events (irAEs) from immune checkpoint inhibitors (ICIs) are sometimes associated with autoantibodies, but we do not know how frequently or whether these autoantibodies are present before ICI initiation. Our aim was to determine the positivity rate of autoantibodies in patients with organ-specific ICI-associated irAEs and determine their value as pretreatment biomarkers. We searched for all English, peer-reviewed publications from MEDLINE, Embase, and Cochrane Library through February 20, 2020, and included any publication describing patients with irAEs and reporting results of any autoantibody investigation. Three reviewers independently extracted data, and 1 reviewer verified all data for accuracy and quality of reporting. We identified 515 publications. Most reports described endocrine, rheumatic, gastrointestinal/hepatic, and myositis/myasthenia/myocarditis irAEs. Autoantibodies were present in close to 50% of patients with ICI-associated endocrinopathies. Anti-BP180 was found in more than 50% of patients with skin irAEs. Antibodies were also common in patients with the triad of myositis/myasthenia/myocarditis including striational antibodies (49%), acetylcholine receptor antibodies (40%), and myositis-associated antibodies (27%). Only 11% of patients with arthritis had either rheumatoid factor or cyclic citrullinated peptide antibodies, and only 30% of patients with sicca had Sjögren antibodies. Autoantibodies were also relatively uncommon in patients with hepatitis (antinuclear antibody, 18%) and colitis (perinuclear antineutrophil cytoplasmic antibody, 19%). Some cohort studies analyzing pre-ICI seropositivity suggest there may be a role for autoantibodies as biomarkers of irAEs. Reported autoantibody positivity is high in irAEs involving the endocrine organs, skin, and muscle, but lower in irAEs affecting other organ systems. Autoantibody investigations in pre-ICI treatment patients have yielded mixed results regarding their utility as a biomarker of irAEs.

Clinical Utility of Striational Antibodies in Paraneoplastic and Myasthenia Gravis Paraneoplastic Panels.

To critically assess the clinical utility of striational antibodies (StrAbs) within paraneoplastic and myasthenia gravis (MG) serologic evaluations. All Mayo Clinic patients tested for StrAbs from January 1, 2012, to December 31, 2018, utilizing Mayo's Unified Data Platform (UDP) were reviewed for neurologic diagnosis and cancer. A total of 38,502 unique paraneoplastic evaluations and 1,899 patients with MG were tested. In paraneoplastic evaluations, the StrAbs positivity rate was higher in cancer vs without cancer (5% [321/6,775] vs 4% [1,154/31,727]; p < 0.0001; odds ratio [OR] 1.35; confidence interval [CI] 1.19-1.53), but receiver operating characteristic (ROC) analysis indicated no diagnostic accuracy in cancer (area under the ROC curve [AUC] 0.505). No neurologic phenotype was significantly associated with StrAbs in the paraneoplastic group. Positivity was more common in all MG cancers compared to paraneoplastic cancers (p < 0.0001). In MG evaluations, the StrAbs positivity rate was higher in those with cancer vs without (46% [217/474] vs 26% [372/1,425]; p < 0.0001; OR 2.39, CI 1.9-2.96), with ROC analysis indicating poor diagnostic accuracy for thymic cancer (AUC 0.634, recommended cutoff = 1:60, sensitivity = 56%, specificity = 71%), with worse accuracy for extrathymic cancers (AUC 0.543). In paraneoplastic or MG evaluations, the value of antibody positivity did not improve cancer predictions. Paraneoplastic evaluated patients with positive StrAbs were more likely to obtain CT (p = 0.0001), with cancer found in 3% (12/468). Despite a statistically significant association with cancer, an expansive review of performance in clinical service demonstrates that StrAbs are neither specific nor sensitive in predicting malignancy or neurologic phenotypes. CT imaging is overutilized with positive StrAbs results. Removal of StrAbs from paraneoplastic or MG evaluations will improve the diagnostic characteristics of the current MG test. This study provides Class II evidence that the presence of StrAbs does not accurately identify patients with malignancy or neurologic phenotypes.

Striational Muscle Antibody Positivity Heralding a Diagnosis of Autoimmune Encephalitis associated with Epiglottic Squamous Cell Carcinoma: A Case Report

A 59 yo woman presented to our emergency room with confusion, spells of loss of awareness over four weeks with malaise, weakness, gait difficulties, and 30 lb weight loss over one year. Brain imaging was unremarkable. EEGs revealed diffuse slowing, triphasic GPDs, and left temporal epilepti form discharges. Spinal fluid showed an elevated protein count. She received a working diagnosis of autoimmune encephalitis and received steroids and antiepileptic medications. She experienced an improvement in symptoms and went home. Follow up revealed elevated striational muscle antibodies and enhancement of spinal nerve roots suggesting an autoimmune neurological syndrome. She received intravenous immune globulin (IVIg) therapy and had periods of improvement followed by worsening a few months later with each dose of IVIg. She presented to the hospital a year with worsening dysphagia and an endoscopy showing an epiglottic mass. Pathology confirmed squamous cell carcinoma, and she received chemotherapy and radiation. We wish to share this rare case of autoimmune encephalitis presenting with only striational antibodies as a heralding sign of a tumor. We postulate that, in the correct context, the presence of striational antibodies alone, despite low titers, may support a diagnosis of autoimmune encephalitis from underlying malignancy.

Clinical differences between early-and late-onset myasthenia

Objective To explore the clinical differences between patients with early-onset myasthenia gravis(EOMG)and those with late-onset myasthenia gravis(LOMG). Methods This was a retrospective study enrolling 157 MG patients.Based on the age of onset, patients were divided into the EOMG group(n=85)and the LOMG group(n=72). The groups were compared on clinical characteristics, including clinical manifestations, MG classification, electrophysiological findings on repetitive nerve stimulation(RNS), single fiber electromyography(SFEMG), levels of antibody against acetylcholine receptors(Ach-R Ab), antibody to muscle-specific kinase(MuSK Ab), titin antibody(Titin Ab), ryanodine receptor antibody(RyR Ab), thyroid function, thymectomy, thymus pathology and responses to treatment. Results The mean ages of onset were markedly different〔(40.9±9.7)years vs.(62.0±12.2)years, P 0.05). Moreover, patients in the EOMG group were more likely to have abnormal thyroid function and higher percentages of receiving steroids, tacrolimus, plasma exchange therapy, and thymectomy(P<0.05). Conclusions The clinical profiles of LOMG are different from those of EOMG in clinical manifestations, thyroid function, thymectomy frequency, striational antibody levels and disease-modifying drug options. Key words: Myasthenia gravis; Recepors, cholinergic

Significance of Striational Antibodies in the Context of Neuropathy

A 88-year-old Caucasian male diagnosed with prostate cancer and treated 1 year ago with transurethral resection of the prostate presents with a 3-month history of progressive fatigue/ malaise, and ataxia with inability to ambulate. He was previously able to ambulate with assistance. On exam, he had a positive Romberg sign which has been present for years, as well as loss of proprioception and vibration sense in both lower extremities in addition to patellar areflexia and dysmetria. He was on many sedatives, which after holding during hospitalization, did not result in any improvement in his functional status. He was compliant with degarelix for prostate cancer treatment. A bone scan showed uptake in the anterior left 6th rib, anterior left iliac crest, and left ischium suspicious for metastatic disease.

Clonal heterogeneity of thymic B cells from early-onset myasthenia gravis patients with antibodies against the acetylcholine receptor

Myasthenia gravis (MG) with antibodies against the acetylcholine receptor (AChR–MG) is considered as a prototypic autoimmune disease. The thymus is important in the pathophysiology of the disease since thymus hyperplasia is a characteristic of early-onset AChR–MG and patients often improve after thymectomy. We hypothesized that thymic B cell and antibody repertoires of AChR–MG patients differ intrinsically from those of control individuals. Using immortalization with Epstein–Barr Virus and Toll-like receptor 9 activation, we isolated and characterized monoclonal B cell lines from 5 MG patients and 8 controls. Only 2 of 570 immortalized B cell clones from MG patients produced antibodies against the AChR (both clones were from the same patient), suggesting that AChR-specific B cells are not enriched in the thymus. Surprisingly, many B cell lines from both AChR–MG and control thymus samples displayed reactivity against striated muscle proteins. Striational antibodies were produced by 15% of B cell clones from AChR–MG versus 6% in control thymus. The IgVH gene sequence analysis showed remarkable similarities, concerning VH family gene distribution, mutation frequency and CDR3 composition, between B cells of AChR–MG patients and controls. MG patients showed clear evidence of clonal B cell expansion in contrast to controls. In this latter aspect, MG resembles multiple sclerosis and clinically isolated syndrome, but differs from systemic lupus erythematosus.Our results support an antigen driven immune response in the MG thymus, but the paucity of AChR-specific B cells, in combination with the observed polyclonal expansions suggest a more diverse immune response than expected.

A Case of Encephalitis Secondary to NMDA Receptor Antibody with Concurrent Striational Antibodies and Thymic Hyperplasia

The number of paraneoplastic encephalitis cases has been gradually rising. The most common one being anti- N -methyl-D-aspartate (NMDAR) encephalitis (over 120 cases reported in literature) [1]. Various other synaptic antibodies have also been associated with autoimmune encephalitis. These include: anti-leucine-rich glioma- inactivated protein (LGI1), anti-α-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPAR), anti-gamma-aminobutyric acid (GABA-B) receptor, and anti-contactin-associated protein 2 (CASPR-2).

Striational antibodies in a paraneoplastic context

The clinical significance of striational antibodies (StrAbs) detected in the course of paraneoplastic antibody testing is unknown. We compared all 203 striational antibody (StrAb)-seropositive patients identified (2004-2005) during evaluation for paraneoplastic antibodies with age- and sex-matched seronegative controls. Thymoma and myasthenia gravis (MG) were significantly more common among cases (P<0.0001). Cancers more rarely detected after StrAb detection were adenocarcinoma in 5 patients and sarcoma in 3 patients. All patients who had a cancer identified after StrAb testing had a titer of ≥ 1:7680 or a coexisting muscle AChR-binding antibody. Autoimmune disorders more commonly observed among cases (with any StrAb value) included: hypothyroidism; rheumatoid arthritis; and pernicious anemia (all P<0.05). StrAbs may serve as a diagnostic clue for an autoimmune diagnosis. There is a low likelihood of oncological significance in patients with StrAb titers <1:7680 without coexisting paraneoplastic Abs.

Three types of striational antibodies in myasthenia gravis.

Myasthenia gravis (MG) is caused by antibodies that react mainly with the acetylcholine receptor on the postsynaptic site of the neuromuscular junction. A wide range of clinical presentations and associated features allow MG to be classified into subtypes based on autoantibody status. Striational antibodies, which react with epitopes on the muscle proteins titin, ryanodine receptor (RyR), and Kv1.4, are frequently found in MG patients with late-onset and thymoma. Antititin and anti-RyR antibodies are determined by enzyme-linked immunosorbent assay or immunoblot. More recently, a method for the detection of anti-Kv1.4 autoantibodies has become available, involving 12–15% of all MG patients. The presence of striational antibodies is associated with more severe disease in all MG subgroups. Anti-Kv1.4 antibody is a useful marker for the potential development of lethal autoimmune myocarditis and response to calcineurin inhibitors. Detection of striational antibodies provides more specific and useful clinical information in MG patients.

Multifocal Paraneoplastic Cortical Encephalitis Associated With Myasthenia Gravis and Thymoma

To report a case of multifocal cortical encephalitis associated with thymoma and to establish an association of this thymoma-related paraneoplastic syndrome with voltage-gated potassium channel antibodies. Case report. University hospital. A 43-year-old woman with a history of seropositive myasthenia gravis and successfully treated invasive thymoma. Four years after thymectomy, she presented with seizure and rapidly progressive confusion and aphasia. Myasthenia gravis remained in pharmacological remission. Magnetic resonance imaging of the brain showed innumerable cortically based signal abnormalities as well as extensive left mesial temporal lobe abnormality with minimal enhancement. Chest computed tomography showed abnormal pleural thickening of the left lung, which proved to be recurrent metastatic thymoma. Results of serological evaluation were positive for acetylcholine receptor, striational, and voltage-gated potassium channel antibodies. She showed partial improvement in response to immunotherapy and chemotherapy but ultimately died 2 months later of tumor complications. Thymoma and myasthenia gravis may be associated with other autoimmune neurological disorders including paraneoplastic encephalitis. This second case of thymoma-associated multifocal cortical encephalitis demonstrates that autoimmune encephalitis can extend to cortical regions outside the limbic system. Autoimmune encephalitis should be considered in the differential diagnosis of patients with myasthenia gravis or thymoma who develop new cognitive symptoms.

Autoimmune Gastrointestinal Dysmotility Treated Successfully With Pyridostigmine

Autoimmune gastrointestinal dysmotility (AGID) is a limited form of autoimmune autonomic neuropathy occurring idiopathically or in a paraneoplastic context. This disorder is considered rare, but is underrecognized as a cause for GI dysmotilities of varying anatomic extent, severity, and duration. We describe the diagnosis and management of an instructive case. A 60-year-old (nondiabetic) woman presented with a 15-year history of severe isolated gastroparesis. Paraneoplastic autoantibody evaluation aided the diagnosis of AGID. This included indirect immunofluorescence (neuronal nuclear and cytoplasmic antibodies), radioimmunoprecipitation assays (neuronal and muscle plasma membrane cation channel antibodies), and enzyme-linked immunosorbent assay (muscle striational antibodies). Serologic testing revealed both ganglionic neuronal acetylcholine receptor and N-type voltage-gated calcium channel autoantibodies. This profile was consistent with AGID and, despite the long history, raised the possibility of lung, breast, or ovarian carcinoma or thymoma. An underlying neoplasm was excluded by appropriate investigations. In a 1-month trial of oral pyridostigmine therapy, the patient's GI symptoms improved and her weight stabilized. Pyridostigmine was continued at a low dose, and was supplemented by tegaserod. Autoimmune serology is a valuable adjunct to the diagnosis and guide to management of patients with AGID. The favorable response to acetylcholinesterase inhibitors, despite a 15-year history, suggests an immunopharmacologic rather than an inflammatory cytotoxic pathology. Immunomodulatory therapy may not always be required. Of numerous autoantibodies currently recognized as biomarkers of AGID, the ganglionic acetylcholine receptor autoantibody is the only proven pathophysiologic effector. Certain neuronal nuclear and cytoplasmic autoantibodies are highly predictive of an underlying malignancy.

Striational Antibodies in Myasthenia Gravis

Myasthenia gravis is an autoimmune disease caused, in most cases, by antibodies attaching to the acetylcholine receptor. Some myasthenia gravis patients have antibodies that bind in a cross-striational pattern to skeletal and heart muscle tissue sections (striational antibodies). These antibodies react with epitopes on the muscle proteins titin and ryanodine receptor, are found mainly in sera of patients with thymoma and late-onset myasthenia gravis, and may correlate with myasthenia gravis severity. Their presence may predict an unsatisfactory outcome after thymectomy. The detection of titin and ryanodine receptor antibodies provides more specific clinical information than the immunofluorescent demonstration of striational antibodies.

Paraneoplastic antibodies coexist and predict cancer, not neurological syndrome

Paraneoplastic autoimmune disorders are usually regarded as syndromic (for example, paraneoplastic optic neuropathy with CRMP5 antibody, opsoclonus with ANNA-2 (antiRI) antibodies. However, for most paraneoplastic antibodies, the spectrum of clinical manifestations is broader than what was initially described in syndromic patients. This study evaluated coexisting autoantibodies in sera of 553 patients with a neurological presentation and one or more paraneoplastic neuronal nuclear or cytoplasmic autoantibodies: antineuronal nuclear autoantibody type 1 (ANNA-1), ANNA-2, ANNA-3; Purkinje cell cytoplasmic autoantibody type 1 (PCA-1), PCA-2; and CRMP-5-immunoglobulin G or amphiphysin-immunoglobulin G. Except for PCA-1, which occurred alone, 31% of sera had more than one of these autoantibodies. In addition, 25% of sera had neuronal calcium channel (P/Q-type or N-type), potassium channel, ganglionic acetylcholine receptor, muscle acetylcholine receptor, or striational antibodies. The authors conclude that the autoantibody profiles observed in patients with paraneoplastic disorders imply the targeting of multiple onconeural antigens and predict the patient’s neoplasm, but not a specific neurological syndrome. They emphasize that optimal serological evaluation for the detection of autoantibody profiles predictive of cancer requires broad screening for autoantibodies. Indeed, diagnostically important autoantibodies are often missed if a single or limited number of individual antibodies are tested.—Valérie Biousse

Myasthenia Gravis, Thymoma, and Intestinal Pseudo-Obstruction

We report a 28-year-old man who presented with intestinal pseudo-obstruction as the initial manifestation of thymoma, myasthenia gravis, and dysautonomia. The patient's autoantibody profile was characteristic of this constellation of disorders, being positive for both muscle and ganglionic nicotinic acetylcholine receptor antibodies and striational antibody. Inflammatory cell infiltrates were found in the myenteric plexus of the stomach and small intestine. Review of 12 previously reported cases suggests that patients with both myasthenia gravis and dysautonomia in the context of thymoma respond poorly to therapy.

Ion channel and striational antibodies define a continuum of autoimmune neuromuscular hyperexcitability.

Neuromuscular hyperexcitability is a characteristic of Isaacs' syndrome. Autoantibodies specific for voltage-gated potassium channels (VGKC) or ganglionic nicotinic acetylcholine receptors (AChR) are markers of this disorder. To determine the frequency of these ion channel antibodies and of related neuron- and muscle-specific antibodies in patients with acquired neuromuscular hyperexcitability, we tested serum specimens from 77 affected patients (35 neuromyotonia, 32 cramp-fasciculation syndrome, 5 rippling muscle syndrome, and 5 focal neuromuscular hyperexcitability) and 85 control subjects. Among study patients, 14% had coexisting myasthenia gravis, and 16% had an associated neoplasm. We found that 35% had VGKC antibodies, 12% ganglionic AChR antibodies, 16% muscle AChR antibodies, and 10% striational antibodies. Overall, 55% had serological evidence of neurological autoimmunity compared to 2% of control subjects. Patients with neuromyotonia were more frequently seropositive (71%) than patients with cramp-fasciculation syndrome (31%). We conclude that acquired neuromuscular hyperexcitability consists of a continuum of clinical disorders with a common autoimmune pathogenesis.

Fulminant Autoimmune Cortical Encephalitis Associated With Thymoma Treated With Plasma Exchange

A 55-year-old man presented with fever, malaise, dysarthria, and intermittent twitching of his right hand. He progressed rapidly to aphasia, intractable myoclonic seizures, and unresponsiveness. Magnetic resonance imaging (MRI) of the head demonstrated multiple nonenhancing areas of signal abnormality involving the cortex of both cerebral hemispheres. Extensive evaluation revealed no infectious cause for his symptoms. Muscle acetylcholine receptor binding and modulating antibodies, striational antibodies, and a neuronal autoantibody specific for collapsin response-mediator protein were detected. An invasive thymoma was discovered and resected. Brain biopsy revealed microglial activation, gliosis, and scant perivascular lymphocytic inflammation. His condition worsened despite treatment with anticonvulsants, intravenous corticosteroids, and antimicrobials. Plasma exchange was performed. The myoclonus stopped; he regained consciousness and gradually improved to the point that he could talk and ambulate with assistance. An MRI revealed regression of the lesions with residual cortical atrophy. This case demonstrates that paraneoplastic encephalitis may occur with thymoma and may extend to cortical regions outside the limbic system.

Serologic profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome

Article abstract-Autoimmune serologic testing is indicated in the initial investigation of a patient believed to have myasthenia gravis (MG) or the Lambert-Eaton myasthenic syndrome (LES). Serologic confirmation of mild, ocular, or recent-onset MG is ensured by a panel of antibody tests more than by any single test, and by testing before commencing immunosuppressant therapy. A positive result for the acetylcholine receptor (AChR)-binding antibody test is characteristic but not diagnostic of MG. AChR-binding or striational autoantibodies are found in 13% of patients with LES, a disorder that tends to be mistaken for MG when the presenting symptoms include ocular or bulbar muscle weakness. Seropositivity for P/Q-type calcium channel-binding antibodies distinguishes these disorders (LES 95%; MG &lt;or=to5%). The AChR-blocking antibody assay is not recommended as a screening test for MG, but if the assay for AChR-modulating antibodies is positive, a positive result for AChR-blocking antibodies provides an additional quantitative baseline for future comparisons in monitoring an individual patient9s immune response in relation to the clinical course and treatment. Seropositivity for striational antibodies is most predictive of thymoma when coupled with an AChR modulating antibody value of &gt;90% AChR loss. Results of all serologic tests must be interpreted by a physician in the context of a patient9s history, physical and electromyographic findings, response to Tensilon, chest imaging, and other serological findings (e.g., striational antibodies, thyroid and gastric autoantibodies, and P/Q-type calcium channel-binding antibodies). <b>NEUROLOGY 1997;48(Suppl 5): </b> S23-S27